Science topic

Viscosity - Science topic

Viscosity is the resistance that a gaseous or liquid system offers to flow when it is subjected to shear stress. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
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Mostly, when I measure the viscosity of liquid material at constant shear rate for 10 min , the value does not change with time . But, during the measurement of viscosity of nanocomposite fluid at constant shear rate, I noticed the viscosity changes between two values in the regular pattern.
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is your nano particles in the form of nano tube...then the forces affects the orientation of the nano tubes, good study for creating good lubricants or hydraulic fluids
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Hi, I want to sterilize the chitosan solution (for microbiological purposes). I don't want to autoclave the solution as it might affect the heat-sensitive additives in the solution. Also, I am not sure if I can use membrane filters as the viscosity of the solution is very high. Are there any suggestions?
Regards,
Elham
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Hi Safia
Thank you for the suggestions. I really appreciate that. Actually, I thought of sterilization of the solvents for chitosan and preparing the solutions under aseptic conditions. The problem is that chitosan powder can not be sterilized (to the best of my knowledge) Also, I can not use antibiotics because I want to do the minimum fungal inhibitory concentration (MIC) test for chitosan on specific fungi. So, I assume that the best way is to use ethylene oxide.
Kind Regards,
Elham
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What is known about the molecular weight of EPDM and/or sEPDM! Are there correlations between viscosity and molecular mass for these polymers?
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Dear Gheorghe Nechifor, more meaningfull features are the MWD and monomers composition ratios and repartion. The way of synthesis proven also to have a high impact on properties and cure kinetics. Metallocenes EPDMs have improved characteristics over classical synthesis techniques. Please have a look at the following documents where some correlation are presented. My Regards
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High viscosity MHECs can be used in Tile Adhesive formulations?
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Hello,
and what tiles ? for what use ?
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This is an anectdotal experience- i mixed two brands of liquid handwash soap without adding any water, and the mixture surprisingly appears less viscous (I have not measured with any device, but can tell from ease of flow) in winter months compared to standard handwash soaps I experienced in summer. can you tell why?
The handwashes are not alcohol or glycerine based- these are soap based. I know sodium stearate, palmeate, oleate etc. are main components of body washing solid soaps. Using potassium instead of sodium makes the soaps softer. and the liquid soaps are sodium laureth or pareth sulfate (or sulfonate?) based. This is not like deteregent where cationic and anoic detergent mixed together produces a buch of much-less water soluble entangled polymers. Even If I assume (polymeric) ionic liquid formation scope, even then viscosity reducing with temperature does not make any sense. Or does it? I know thermoplastics show higher elastic modulus at higher temperature sometimes due to entropic effect. Is something like that happening here? can you tell me whether there ane widely circulated liquid-soap-based handwashes that are not laureth or pareth based? Or what can be the role played by additives into the handwash?
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The viscosity of cleaning solutions with a low salt concentration is affected by the nuclear quantum effect. Proton tunneling along the chain of H-bonds is observed, which leads to an increase or decrease in the intermolecular interaction.
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plz recomend methods
i have a problem about Mixing in pipe(polymerization).
because of polymerization speed(too fast), static mixer used to be blocked with gel(polymer gel).
so i need pre-mixing front of static mixer.
i thought about method
mixing plate (make turbulant flow) -> raw material's viscosity is high (X)
jet mixer -> can make a gel (fast polymerization) -> can be block the injector hole
so to solve a problem plz recomend any method which have a small possibility !
thank you
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Dear Jae Hyeok Lee, I couldn't get the whole picture of the situation. Why not working in an emulsion polymerization ? Please give more description of the experimental setup. My Regards
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How can I reduce the viscosity of saliva samples for the proteomics project and homogenize the samples viscosely?
It should be noted that I do not want proteins to be removed in this way
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How to digest mucin in saliva?
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How should I set the viscous resistance coefficient and hydrodynamic resistance coefficient to describe the free exchange of gases between two gas chambers by bulk viscosity? I have been searching for a long time, but I can't find them.
ps:I know how to establish fluid exchange, but how should the two parameters viscous resistance coefficient and hydrodynamic resistance coefficient be calculated (e.g. air)
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  1. Create a fluid exchange parameter. To do this, go to the "Parameters" tab in the "Model Tree" and click "New." Select "Fluid Exchange" as the parameter type and enter a name for the parameter.
  2. Set the viscous resistance coefficient. To do this, click on the fluid exchange parameter you just created and go to the "Properties" tab. Under the "Viscous Resistance Coefficient" field, enter the desired value for the viscous resistance coefficient.
  3. Set the hydrodynamic resistance coefficient. To do this, click on the fluid exchange parameter you just created and go to the "Properties" tab. Under the "Hydrodynamic Resistance Coefficient" field, enter the desired value for the hydrodynamic resistance coefficient.
  4. Assign the fluid exchange parameter to the appropriate region. To do this, go to the "Regions" tab in the "Model Tree" and select the region where you want to apply the fluid exchange parameter. Under the "Material" field, select the fluid exchange parameter you just created.
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Hello everyone.
I am doing a CFD simulation for waste heat boiler and simulation boiling in steam drum.
I used ANSYS Fluent to perform the simulation. However during the calculation section. I received this error
"reversed flow in 274 faces on pressure-outlet 18.
Stabilizing mp-x-momentum to enhance linear solver robustness.
Stabilizing k to enhance linear solver robustness.
Divergence detected in AMG solver: k temperature limited to 1.000000e+00 in 8519 cells on zone 2 in domain 3
turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 18252 cells
Divergence detected in AMG solver: k
Error at host: floating point exception
Error at Node 0: floating point exception
Error at Node 1: floating point exception
Error: floating point exception
Error Object: #f"
May I know what are the possible cause of this error?
Any advice? Thank you
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The "reversed flow in 274 faces on pressure-outlet 18" error message indicates that there is a problem with the boundary conditions at pressure outlet 18. This error can occur if the pressure outlet boundary condition is not properly defined, or if the flow direction at the outlet is opposite to the expected flow direction.
The "Divergence detected in AMG solver: k temperature limited to 1.000000e+00 in 8519 cells on zone 2 in domain 3" and "turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 18252 cells" messages indicate that the solver is encountering numerical instability during the simulation. This can be caused by a variety of factors, including an inappropriate grid, inaccurate boundary conditions, or a poorly defined model.
The "floating point exception" error message indicates that there is a problem with the numerical computation being performed by the solver. This can be caused by a division by zero, an invalid operation, or an overflow.
There are a few things you can try:
  1. Review the boundary conditions at pressure outlet 18 to make sure they are properly defined and the flow direction is correct.
  2. Check the grid quality to ensure that it is suitable for the simulation. A poorly resolved or skewed grid can cause numerical instability.
  3. Review the model and make sure it is properly defined and all necessary parameters are specified.
  4. Check for any invalid or unrealistic input values that may be causing problems with the numerical computation.
  5. Try using a different solver or solver settings to see if the error persists.
I hope this helps!
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Is there any correlation between MFI and viscosity, measured i.e. with Brookfield viscosimeter? In particular for linear polymers.
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Dear @Giacomo Del Bianco, first MFI (melt viscosity) and brookfield (solution viscosity) both have indications on MW. Also note that MFI is meaningfull only for polyolefins (PE and PP). There are many studies going with this topic. Please have a look at the following similar RG thread and the references therin and the other documents. My Regards
10.1016/j.polymertesting.2013.09.009
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I have found EPOON 1004F epoxy resin with good viscosity, but I am not sure how to use it. Could you please tell me how to use EPOON 1004F epoxy resin before? Thank you very much.
Address of attached materials:
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I visited the link you send but everything was in not arabic characters, so I was unable to understand the information. Nevertheless, I can explain you how I use to work in order to embed something in epoxy resin. Depending on the viscosity on the resin actually. The main idea is to dissolve the epoxy in a low-boiling temperature solvent (dichloromethane is an option) to obtain a viscous liquid. Then you embed whatever you need to embed (in this case, microspheres), and after that, the only thing to do is to evaporate the solvent, for example with vacuum or some heat. If you use dichloromethane, with 40ºC is enough. Then you have your spheres embedded with your epoxy resin.
At this point, this should be enough for what you asked for. Remember only that epoxy resins need a crosslinker. Usually, these are added once you want to crosslink, and diamines are the most common.
Hope it helps! Best of luck!
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I have scaled down my geometry 1:1000 ratio. During simulation, if I input the velocity parameter same as the actual case, will it be considered as correct procedure or not?
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虞军辉 junhui yu Thank you for your reply.
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This developed turbulent flow codes is a finite element computer model, written in FORTRAN which was developed to solve the Reynolds equations of motion and continuity for steady and fully developed mean turbulent flow. The Finite Element mathematical treatment of this matter is reported in the following Ph.D. reference at CSU, Fort Collins, Co, the USA (please the link to this dissertation is https://mountainscholar.org/handle/10217/235417). Later on this code was extended to three dimensional and unsteady flows. The turbulent stresses appearing in the Reynolds equations are modeled in terms of mean velocity nonlinear gradients and turbulent viscosity. The non-linear algebraic stress model used in closed channels is totally different from the one used in open channels with new algebraic open surface proximity functions. A two equation turbulence model consisting of the turbulent kinetic energy (K), and its rate of dissipation (ε) evaluates the turbulent viscosity that appears in the algebraic stress models.
For wall bounded flows especially at corners (such as at an airplane's body to wing), my code succeeded in an excellent manner in simulating the main velocity, secondary velocities and turbulence structure (turbulent viscosity, K, and ε). In addition, distributions of the non-gravitational pressure and turbulent stresses are well predicted too. You may contact me for samples of the results of simulating turbulent flow in a square duct. Along the corner bisector the maximum secondary velocity divided by the average shear velocity is calculated as 0.31 which is in agreement with experimental data of Brundrett & Baines (1964) of about 0.32. For the wall bisector a value of 0.21 is predicted versus a measured value of 0.20 by Gessner and Emery 1980. Bulging of the velocity contours toward the corner is well predicted which is important in reducing separation due to adverse longitudinal pressure gradients. No up-winding or (over/under) relaxation are used. Non-linear Newton–Raphson that has quadratic convergence is used for dealing with the system of nonlinear equations. The boundary shear stress is calculated and is shown to be affected by the secondary velocities.
- For open channel flows: a very distinct feature in my nonlinear k-ε model is the use of an-isotropic turbulent viscosity in which the turbulent viscosity in the vertical direction differs from that in the lateral direction, a feature not existing in any existing CFD code to my knowledge. The model succeeded in predicting the depression in the main velocity maximum to be at 0.6 from the bed in a channel with aspect ratio of 1:2. The secondary velocity structure is also well predicted . Another important feature is prediction of the cellular secondary cells due to periodic roughness changes along the bed or walls. This helps in investigation of flow over ribbed surfaces.
Now How much does the source code for this turbulent flow CFD code worth in US $?
I appreciate honest answers and offers.
For more details I can be reached at my email:
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I agree with Filippo, CFD-online would attract more answers from developers.
Let me also clarify that both OpenFOAM and Code_Saturne (not sure about SU2) have today the most advanced turbulence models, which include non linear ones as well. This is especially so for Code_Saturne, that has been the preferred choice for developments in Manchester. If we allow to consider closed source codes, well, Ansys Fluent just has the same capabilities with several algebraic non linear and full Reynolds Stress Models. Also, let's not forget that Florian Menter is in charge for that in Ansys.
I'm not really into free surface flows, so I can't really tell, but the same reasoning applies here. There are several options for the most diverse conditions. In general, coming from commercial development, let me tell you that every low hanging fruit that works for general solvers with unstructured grids is generally a no-brainer and eventually gets in (as long as the model is actually helpful).
This just to clarify that if you intend the CFD solver market as a battle field, it's not the early 90's Fluent that you're going to face. It's 2022, and there is also Siemens with Star, Cadence with ex-Numeca, Altair with several products, and few other less known vendors of high quality.
This, however, it's not the main point here, in my opinion, in valuing your code. I haven't read your thesis, but it seems that the main point of your development is sitting there open to everyone. So, if it is usable for general flow solvers, I guess you are left with little to none, because everyone can already use your model without your code. Also, 5k lines of code is very little in this case. If you want a comparison, I have seen fully original source codes of that length sold, non exclusively, for about 30k USD. So, if ever, in your case the amount should be much lower. Also, note that we are speaking about selling the source code for third party reuse at their wish, not licensing the code here.
So, excluding, de facto, the previous hypothesis as meaningful, let's assume that your unique modeling is not usable in other codes or that not everything is open to everyone, which is basically the same. I am myself into CFD code development and a fully parallel unstructured solver with basic functionality (multi-zone with CHT, URANS, steady/unsteady, implicit/explicit, incompressible/compressible, scalars and all the machinery to make it usable like a major commercial solver) can be fit in 20k-25k lines of code. So, at 5k, I assume your code is weak on some of these basic features. So, we are presumably speaking of a niche code that can eventually do some specific things very well, but doesn't seem more generally usable.
Thus, finally getting to your question, I think the valuation for your code is totally up to the niche you are addressing, the problem you are solving and how costly it is for your niche. If your code solves a multi-billion dollar problem for a very rich industry and nobody else can solve that same problem, people would pay as much as you ask, even if your code was still written on punch cards or could run on ancient hardware of limited availability. The CFD market is full of verticals that get exploited, but it is really up to you to actually know if your code fits any of them.
But if you don't address a specific unsolved problem nor have a more general usability, I don't think you can really monetize your code.
Also, I didn't mention this but, the code must obviously be also usable by a general audience. If it requires expert adjusting for every case, it becomes extremely difficult to use and very few will be able to, even if it addresses a multi-billion dollar problem.
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We have been using PEG-8000 (10%) and NaCl (0.5 M) precipitation for concentrating phage samples before ultracentrifugation and for some of them, we got a really viscous solution after PEG precipitation. Adding DNase I has not helped. Why this high viscosity and what to do to get rid of it? Using samples as they are for ultracentrifugation gives no visible virus bands.
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Bacteria and large bacterial fragments should be fully removed post-PEG precipitation. You can increase the volume to resuspend precipitate, or dialysis into some solutions without PEG, which may alleviate the problem. More sucrose gradient can be used in the density gradient centrifugation if you can`t find the visible virus bands. At the same time, you should avoid the mutual dissolution of sucrose with different concentrations to destroy the density gradient. At last, you can place a light source at the bottom of the centrifuge tube, which can help you get the virus band more easily.
Good luck
Guosong
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I am having trouble with C2C12 cells detaching from the well plates after adding conditioned media. Areas on the left and bottom sides of the wells lack cells after switching to the conditioned media. I assume it is due to the media's higher viscosity than PBS as they only dislodged during the media change and not the PBS wash.
Is there any way to prevent the cells from dislodging when I add the media? Any help would be greatly appreciated!
Experiment overview:
1. cells were seeded 24 hours before the media change
2. media aliquoted with single-channel micropipette against the wall.
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You could perhaps coat your plates with poly-d-lysine to increase the chance they stick a bit better. Best of luck.
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Hi,
Why does the non ionic surfactant, polysorbate 80, decrease the viscosity in a constant PVP ethanol polymer solution, yet at the same time, increase the diameter of its electrospun nanofibres?
Can't find anything in literature, nor in any organic pathways!
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The initial solution is PVP-ethanol polymer solution. Polysorbate 80 is another non-ionic surfactant acting like PVP. It will interfere with PVP in PVP-ethanol polymer solution either in positive or negative result to your research work. Therefore, the answer would be the purpose of the research work study.
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I needed published articles or any applying reference with experimental data on how temperature affects the settling velocity of particles. How the temperature change also affect the kinematic viscosity of fluid.
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Viscosity increases with temperature for gases and decreases with temperature for liquids. Kinematic viscosity is absolute viscosity divided by density, e.g. Temperature, viscosity and density must be in consistent units, and under the same conditions.
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Hello all,
I hope you are doing well!
I am currently doing research in the field of additive manufacturing with technical ceramics, and I have two separate questions specifically regarding silicon dioxide (SiO2).
1. In 3D printing with SiO2, I use a slurry mixture which is composed of SiO2 powder, deionized water, DARVAN C-N (for dispersant) and CELLOSIZE Texture F4M (for binder). The CELLOSIZE Texture F4M is cold-water dispersible hydroxypropyl methylcellulose which is primarily used to control viscosity within the slurry. My main issue is when I add the binder into my SiO2 slurry and mix it, the slurry almost becomes a non-Newtonian liquid within 20 seconds, in that sudden impact hardens the overall slurry and after the impact it immediately goes back to a viscous state. Could you please point me to any research regarding this issue? Additionally, I've tried the same binder on alumina and silicon carbide (other technical ceramics) and haven't faced this issue. I've also experimented with modifying different speeds of mixing, gradual increments of adding the binder, and mixing in a vacuum environment; however, none of these helped. Could it be that methylcellulose reacts chemically with SiO2, and a different binder should be used?
2. For sintering ceramics, I've read that ~80% of the melting temperature is a good baseline for experimentation. My goal is to increase part density and flexural strength. Could you please point me to any research regarding selecting a sintering schedule (time and temperature) for silica specifically? I've read through literature suggesting ~1300C for around 8 hours with a heating rate of 5C/min; however, I'm curious if a lower temperature such as 900C for a longer sintering time or a higher temperature of 1500C for a shorter sintering time would vary the final part density and flexural strength significantly. I'm currently only experimenting with single-stage sintering.
I appreciate all your help and insight.
Thanks & Regards,
Sam Choppala
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Dear Sam Choppala,
Regarding your first question about methyl cellulose. This water-soluble binder works well in a basic solution at temperatures below 15°C (cold water). SiO2 makes the solution acidic and this allows the methyl cellulose to polymerize. For acidic solutions there is another water-soluble binder - polyvinyl alcohol (PVA), which you can successfully use here.
The second question (sintering of SiO2 ceramic) is much more complex than you think. Pure SiO2 ceramic does not exist and cannot be produced by sintering. The problem with this is the polymorphic transformations of SiO2, which are associated with large changes in volume (when heated, alfa quartz first transforms into beta quartz and then tridymite and cristobalite form). In order to avoid this problem with polymorphic transformations, SiO2 (quartz) must be sintered with additions of CaO and FeO. The resulting refractory material (silica brick) is not dense technical ceramics, but porous coarse-grained refractory stone used in furnace construction.
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I am seeking to increase the viscosity of my mammalian cell culture medium while minimizing non-viscosity related effects on my cells.
Do you have any specific protocol and compounds to suggest?
I have ordered high MW dextran sulfate (Sigma D8906), but I am worried by the fact that the only recommended use is nucleic acids hybridization.
Is there any other type of dextran that would be better suited for cell culture?
Thank you for your help.
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Malcolm Nobre Thank you, the first publication had escaped my literature search!
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I am trying to use powder NaCMC (High Viscosity 1100-1900 CPS) as a dispersion agent for dispersing chopped carbon fiber in the concrete mix, but the problem lies in the solubility of NaCMC in water. After adding certain amount of NaCMC in water it forms a lump and floats in beaker. So my question is does the viscosity of chemical affect the solubility in water. If not then what are the ways to increase solubility of NaCMC in water.
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Dear Vedant Sinha, NaCMC is highly water soluble, but its solubility depends on the degree of substitution ? Please have a look at the following documents. My Regards
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I prepared eutectic solvent but the viscosity is high, I want to make it less viscous.
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adding some organic solvents
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Hi, I'm new to rheology and viscosity study. I have emulsion samples containing clay, polymer, and emulsifier. The difference between the samples is just clay concentrations and oil constituents which give them different viscosity from low to medium viscosity (0.2 - 31 Pa.s). The current rheometer I have in the lab is Rheosys Merlin II (controlled shear rate rheometer). The goal of the rheometry analysis is to assess:
1. Apparent viscosity
2. Shear thinning (viscosity slope)
3. Yield stress
4. Thixotropy
For the preset, I can only use shear rate. I have the range of shear stress, viscosity, time, and torque results generated from shear rate of 1s-1 to 1000 s-1 (10 data points per decade; three decades; 10 seconds measuring duration per data). I found out that some medium viscosity samples experienced solvent evaporation, so maybe I will try 5 seconds instead of 10 seconds.
So, my question is:
I found that several references told me to not use curve fitting models for yield stress determination since those methods are only used for simple QC tests and not for modern RnD work. Can you recommend to me which yield stress method with the preset controlled shear rate that I can use instead of curve fitting models? I plan to use a single fitting line because it provides yield point of "reversible deformed" behavior that may benefit the next analysis: thixotropy. But the method can only be used for the preset controlled shear stress. Anyone can help me?
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Thank you so much for the help. After reading the given reference, I have made some modifications to the method, and the data was quite reproducible! Thank you so much
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I synthesized high viscosity phenolic formaldehyde resin with viscosity about 5000-6000 cPs with pH about 8-8.5 (I used alkaline catalyst e.g NaOH). Viscosity of resin decreased drastically (more than 70%) after I just added 10% of water. For coating of cloth backing material application needs resin with lower solubility in water (viscosity will not decrease drastically after add 10-20% of water).
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The subject is not under my jurisdiction.
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Dear researchers,
I tried to investigate the rheological properties of okra mucilage under shear and oscillation condition. When I make a comparison between shear viscosity and complex viscosity, the result is shown as attached (The complex viscosity increases suddenly when frequency is high enough). Can someone give me a reason for this phenomenon, please?
Thank you very much.
Sincerely,
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Dear Minh Nguyen, this is the normal behavior. The correlation between the two types of viscosities is possible only at low shear in the linear viscoelestic domain, at high shear level, the arising of thixotropy make the distinction between viscosities types. My Regards
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Hello everybody~!
I've heard that Einstein come up with a model for how many spheres could we have in liquid without influence to viscosity.
Is there any paper that deals with this?
Thank you~!
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Howdy Sangho Ko,
Try: THE Einstein equation E = E 0 (1 + 2.5 V) relating the viscosity E of a suspension of solid spheres and E 0 the viscosity of the dispersion medium, V being the volume in parts of a cubic centimetre occupied by the dispersed solid, has been used as a basis for determining the molecular structure of proteins and other colloidal substances 1.
Author: E. W. J. Mardles
Publish Year: 1940
Viscosity of Suspensions and the Einstein Equation | Nature
📷
Incidentally, your English is much better than my non-existent Korean.
Happy Trails,
Len
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All, It's known of curse that viscosity depends on pressure. Often this dependence is weak and sometimes it is significant. It is an odd and unmotivated question but, nevertheless, I am wondering if our parameterizations of turbulent viscosities should also include some measure of local pressure fluctuations? (This may be a question resolved long ago by people doing compressible turbulence.) I'm hoping to learn from people's answers and ideas. Thanks! Bill
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It does via velocity. Because we don't have a dynamic equation for pressure, we employ a correction to velocity, and use velocity gradient to model viscosity. We do this (bring pressure fluctuations) in turbulence models, but we don't yet know how to do it properly.
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As per QC related , Viscosity of ophthalmic solution is still not defined . So if anyone just help me regarding this .
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Between 25 and 50 cps
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I would prefer liquids in the 50-100 cps range that will not change viscosity as much over a temperature range of 22-50 degrees celcius.
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I would recommend poly(dimethylsiloxanes) such as DMS-T15 and DMS-T21 (Gelest). See https://www.gelest.com/wp-content/uploads/Goods-PDF-brochures-inert_silicones_2013.pdf, especially p.4 (for definition of the viscosity-temperature coefficient) and p.8 (for actual data).
In principle you should look for compounds that have weak intermolecular attractive forces - so, no H-bonds or ionicity - and that are far above their glass transition at the temperature range of interest, despite the relatively high viscosity you are looking for. (Viscosity dependence on temperature increases sharply as a liquid approaches its glass transition.) PDMS (and probably some related compounds) should be appropriate.
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How CaO, FeO, SiO2, Al2O3 and K2O plays role in determining the viscosity of blast furnace slag?
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There is no contradiction in paragraphs 2 and 3, I just accidentally wrote the word calcium instead of the word potassium (already corrected).
In silicate glasses of the Na2O-CaO-SiO2 system, the replacement of alkaline oxides by alkaline earth ones transforms "long" glasses into "short" ones, in other words, it creates a significant drop in melt viscosity at the liquidus temperature. If silicate glasses with a high content of alkali oxides begin to soften already from 600°C and a further decrease in the viscosity of the melt occurs gradually with increasing temperature, then glasses in which alkali oxides are replaced by alkaline earth ones begin to soften almost at the liquidus point (1300-1400°C), in which there is a sharp drop in the viscosity of the melt. So it turns out that the viscosity of melts with a high content of alkaline earth oxides at temperatures below the liquidus point is very high, and above the liquidus point it is very low.
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Can chemicals ( demulsifier or fast dropper) be used to separate water from Heavy crude oil to prepare for the following tests (viscosity, asphaltene deposition, SARA test and flash point)? Is this ASTM compliant?
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Solvents+ Surfactant
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I am trying to characterize the viscosity of newly developed cell culture media formulation. WE have AR2000Ex Rheometer. I am wondering what could be the values for the parameters to setup for the characterization, especially (a) Range of shear rate (1/s); (b) Gap between the plates; (c) Normal force; (d) diameter of parallel plates; (e) angular velocity (w); and any additional parameters I should consider? Really appreciate any inputs which can help us to get started.
Thanks,
Bhushan
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The speed of movement is determined using the Reynolds number. This is the value at which the laminar flow of the medium becomes turbulent.
Shear stress is the force acting per unit area of the vessel and is measured in pascals (Pa).
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I am doing research on sand erosion experiment. What are the chemicals or additives that can be added to water to simulate the fluid properties of crude oil ( e.g viscosity and density of crude oil) ? Other than glycerin water mixture, what else i can add to water to simulate the viscosity and density of crude oil ?
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you can increase the viscosity by decreasing the temperature
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I was looking for silicone oil based shear thinning liquids. I could't find one yet,
so i was trying to address this issue by dissolving polymers in silicone oils. I tried PEO and Xanthan gum but there was no homogeneous mixture. I want the dynamic viscosity be less than 1000mPa.s .
Appreciate your recommendations
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Hi Sabbir Hassan Sorry for the late response, I haven't checked messages for a long time.
I actually couldn't find any polymer. I am not sure if this could be useful for your case, but I tried to make emulsions (like mixing silicone oil and surfactant (tween 20)). I measured the viscosity, it showed a shear thinning property. note that, the shear thinning property totally depends on the size of dispersed droplets.
Good luck.
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Being aware of the hazardous nature of both phenol and 1,1,2,2 tetrachloroethane, I don't want to take any risk of not being sure about the procedure. I know this solvent mixture is commercially available, but in my case I have phenol (crystals) and 1,1,2,2 tetracholoroethane (98% solution) separately; I need this solution for the ASTM D4603 method to determine the inherent viscosity of PET. 
If anybody here has made the Phenol/1,1,2,2 tetracholoroethane (60:40 w/w) solution by himself, please share your practical experience with me.
Thank you in advance for any help.
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Yes, I have done Intrinsic viscosity measurements by taking phenol and 1,1,2,2 tetrachloroethane in a 60:40 ratio. For a LAUDA Viscosity instrument, you require a minimum 25ml solution. So you just take 15ml of phenol and 10 ml of 1,1,2,2 tetrachloroethane and stirred at 100 deg celsius still your PET material( at different concentrations of 0.1,0.3,0.5,0.7) is dissolved. Then put your solution in a viscometer of 0.8mm dia and start the test. You can get relative viscosity, reduced viscosity, Intrinsic viscosity, and molecular mass of the solution. Before test you have to find out the kinematic viscosity of the solvent mixture.
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Hello
I need temperature-based mechanical properties of Sn63%Pb solder material, specially "viscosity" and "surface tension". Are there any data, books or articles that represent this?
Thank you in advance
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I am trying to simulate miscible liquids in fluent. I am trying to reproduce the results of a paper, but I am not getting the same mass fraction plots as in the paper. I am using species transport model with laminar flow model. I have set the viscosity and molecular diffusion coefficient values as given in the paper. I have tried 4 different sets of mesh based on cell count and refinement. I cannot seem to know what may be the problem
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I've tried both VOF and mixture but there isn't any difference
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I am looking to melt extrude PLA and a microcellulosic filler in a single screw extruder. The concern is insufficient back pressure due to low polymer viscosity before the compression zone. I want the polymer to be softened up instead of losing viscosity. This is the context in which I want to ask if Tg and softening temperatures are the same or different. If so, can a test method for gauging the softening point (temperature) of semicrystalline polymers and composites be shared?
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Of course, and by the way softening is the threshold to melting at which chains are freely flowing, i. e., no restriction to any form of movements. My Regards
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It is well known that for lubricating oils, viscosity changes with change in pressure. But I am not sure if the case with grease is same. If someone could help here, I will be thankful.
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Yes. Grease is defined as a solid to semi-fluid product or dispersion of a thickening agent in a liquid lubricant. Other ingredients imparting special properties may also be included. The base oil is kept inside the thickener structure by a combination of Van der Waals and capillary forces. The oil gives the grease a viscosity-pressure-temperature relationship.
"Grease Lubrication in Rolling Bearings" (Lugt, P) gives a good overview on this topic as well as some example calculations.
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Ansys normally takes the Bulk Viscosity Coefficient (mu_b) as zero in all simulations. However, there are some cases of supersonic flows where mu_b is non-negligible. For such a case, how can we modify the momentum equations in Ansys to add the contribution of bulk viscosity ?
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Yes, if there is no option for bulk viscosity to add, then you may proceed with UDF.
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I recently using the Bio-Rad droplet PCR kit for a qPCR application, However, I realized that the generated droplets' viscosity increased a lot after thermal cycling (40X).
Then, I replaced the Bio-Rad oil system using Novec 7500 +5% Picosurf, the viscosity did not increase.
So if use entire kit from Bio-rad the droplet viscosity increased after Thermal cycling
If use Novec 7500 +Bio-rad reagent supermix for the aqueous phase, no increase in viscosity.
Does anyone know what makes the viscosity increased?
I have difficulty to merge these high viscosity droplets with another droplets library for downstream assay
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We have purchased a viscometer but the lead time is a bit long for now.
I will let you know when I get the equipment delivered
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I used Brookfield DVNEXT RHEOMETER and found the values of viscosity without the values of density. Now I am trying to find the viscosity average molecular weight of the polymer.
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Viscosity average molecular weight determination requires intrinsic viscosity measurement and not apparent viscosity. Ubbelohde viscometer is commomly used. Check this link (http://www.ampolymer.com/Mark-Houwink.html) for a shortlist of polymer-solvent constants. It is important that your polymer is able to completely dissolve in the selected solvent.
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Dear Colleagues,
Do you have any reference/paper/document including the data/information or correlation(s) for the viscosity of lactose solution with various concentration at different temperatures?
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Dear Mohammad Mahdi A. Shirazi,
I have attached one article. I hope it would be useful.
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Although capillary or falling ball viscometers are used but if we wish to get it via rheometer.
Any experts who can give light on this topic especially with reference to PVC solutions.
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Dear Sumit Singh, the same question was asked say 8 years ago, clear answers are presented. Please have a look at the following RG thread. My Regards
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We fabricated the composite of PVA and nano-carbon-particles. The results of zeta sizer show that the size of PVA chains is increased and nano-carbon serves as a crosslinker. But in the case of rheometer's results, the viscosity of the above sample is decreased, which shows that nano-carbon serves as surfactant. The mechanical properties of composite structure are enhanced and XRD shows that the crystalline regions are less in the composite structure. What could be the possible reason of decrease in viscosity in your opinion ?
Here i have attached some XRD, zeta sizer and rheometer results..
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Is it PVA solution? By dynamic viscosity you mean the absolute value of the dynamic viscosity? Could you share the G' and G" values too? Is the carbon dispersion stable?
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I want to design an experiment for measuring the melting, hardening rates of different types of plastics. The equipment that are current available includes; a closed furnace with control valve, thermocouple, infrared thermometer, crucible and stopwatch.
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Melt viscosities (η) typically follow the Vogel–Tammann–Fulcher equation (VTF) with temperature: log η = A + B/(T − T0) with A, B, and T0 as fitted constants.
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Hi,
Does anyone have any experience / advice on stabilizing solutions with heavy fumed silica loading (~60%)?
I am seeing odd viscosity behavior in my system where stored solutions are showing a kind of viscosity gradient with the bottom being less viscous than the top. Are agglomerates of fumed silica forming and rising to the surface? The solution doesn't have a noticeable visual indication of any sort of separation.
Any advice you can give into this phenomenon and how to stabilize it would be greatly appreciated.
Thanks,
Mike
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What apparatus can be used to measure shear strain rate and viscosity for a non-newtonian fluid? Could it be done using the conventional spindle Brookfield viscometer?
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In addition to the previous right answer, Prof. Omar Abro, please look at the following scientific instrument.
Its characteristics seem to be wide, i.e., for very different non Newtonian fluids from viscoelastic to heavy oil:
Best Regards.
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There are different semi-empirical correlations for estimating the binary diffusion coefficient of liquids. For example, correlations involving the formation of complexes covering the low viscosity solvent, correlations involving high viscosity solvents, correlations incorporating the solute-solvent interaction, and correlations containing the effect of solvent association (Wilke and Chang equation).
The Wilke and Chang correlation is one of the most widely used to estimate binary diffusivity. However, in this equation, there is a parameter called solvent association (φ), and its value depends on the type of solvent. Does anyone know how to determine this solvent association parameter (φ)?
I add the equation of Wilke and chang in the annex.
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Dear Diakaridia,
In a relatively recent paper : Miyabe, K. & Isogai, R. Estimation of molecular diffusivity in liquid phase systems by the Wilke–Chang
equation in Journal of Chromatography A, 1218 (2011) 6639– 6645 a method to calculate the association parameter is discussed.
All the best with your research.
Regards,
Paul
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I need to make a polyvinyl acetate homopolymer in ethanol. But I require high viscosity (60000 cPs). I solved the problem using 30% ethanol and 70% ethyl acetate but the customer don't like the product's smell.
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Dear José Luiz Vieira, the following studies have tried various solvents, please check and select the best one. My Regards
10.1002/macp.1961.020440136
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I am researching making droplets using Microfluidics technology.
To create smaller, immiscible droplets, I want to use a very high viscosity (biocompatible oil would be better!) oil.
I tried increasing the content of surfactant, but there was a limit. So far, I have tried Hexadecane ( 2.11cSt ), Light mineral oil ( 17cSt ), Heavy mineral oil ( 65-75cSt ), and Soy bean oil ( 50cSt ).
Any good suggestions would be appreciated.
Thanks.
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Fluids containing high concentration polymers, soils, nanoparticles, etc. typically have high viscosities, and high viscosity fluids are difficult to encapsulate into uniform droplets. When it is desired to generate droplets directly from various aqueous and non-aqueous fluids, viscosities can vary between 1.0 and 11.9 Pa.s
and a dispersed-to-continuous viscosity ratio up to 1,000, while the volume fraction of droplets up to 50% can be achieved.
Regards
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Hello,
Im having trouble understanding why I am seeing increases in viscosity at low frequency and high temperature for some neat polymers. Ive attached an example with neat LDPE. Temperatures 110C - 170C behave like you would expect for a polymer but a 190C and 210C, the visosity starts to increase as the frequency reduces.
We've seen this in some composites, and Ive always assumed it has to do with some rheological percolation. But here you can see we have a neat polymer with no filler material, which shouldnt have any percolation effects.
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Dear Matthew Eaton, this is attributed to the branching length and density. Please have a look at the attached file. My Regards
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I am trying to raise the melt viscosity of a PHA polymer however as it is microbially produced the MW is already very high and difficult to control, and the addition of crosslinking agents will compromise the biodegradation credential.
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Dear Anand J Gaston, you can blend it with PLA, or use fillers such as talc for example. My Regards
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I need the change of the modulus of elasticity, the yield stress, and viscosity parameter with a change of temperatures from 25 degrees Celsius to 400 degrees Celsius... Thanks
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Your data are available in ASME material Code
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Hi people I am attaching a File Please help me how do I explain this rheology Trend? What does it say?
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In the observed frequency window your molecules do not interact much and the material behaves more viscous. If you go to higher frequencies, G' and G'' approach and if you go to even higher frequencies, they'll probabely cross (G'>G''). This is related to your molecules entangling. If they are entangled, they can't react to deformation at higher frequencies as a liquid any more. The entanglements are a kind of physical crosslink at high frequencies, while at low frequencies the molecules can slide past each other.
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Hi all,
I am doing a numerical study for a liquid crystal-colloid using Lattice Boltzmann method as the numerical tool. I am using a MRT-collision scheme in my model which allows me to choose the viscosity independently unlike the BGK operator where the viscosity depends on the relaxation time. But, when I convert the unit of physical parameters to LB units, the viscosity which I get is quite high (O~3) and is unacceptable. Am I allowed to choose the viscosity independently and not calculate it according to the lattice resolution?
Regards,
J.
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When i try to measure the viscosity of my sample via rotational Viscometer, the spindle continues to rotate without giving the readout. I have waited for as long as 30 minutes but to no avail. Can anyone please guide me what's the reason behind this? I would highly appreciate..
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If you have the manual, every thing is specified, if not, you can download it with the instrument specifications. Good Luck in your work
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Hello all
I have been trying to prepare Co doped TiO2 nanoparticles through sol gel method. I have a issue where my gel usually forms after 24 hrs but it is dried and its not viscous anymore. Can anyone help me with suggestions on how to retain the viscosity of the gel
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Dear all, please have a look at the following reference and RG thread. My Regards
doi:10.1080/25765299.2019.1610209
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Hi!
I want to manufature a chip for drop-seq. From previous studies 80-100 um depth has been used. The dripping crossing width is 94um. The drop size is required to be both 100 and 125. The inlet has some viscosity coming from cell lysate (CA-630) and Iodixanol (for cell suspension). Which depth is better and can easily realise both drop size?
Thanks!
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Thanks Qiyou Chen
Well we don't have a fast camera as well. What we do is just measure when from collection pool
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I would like to know the Li2SO4 solution viscosity at 45 deg C
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Please refer to the attached paper where you will find in table 1 the Viscosity value for Aqueous Li2SO4 Solutions at Temperatures from 298 to 575 K, i.e. from 24.85 °C to 301.85 °C.
Regards
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I am interested in solving the dimensionless equations for a bubble motion in COMSOL Multiphysics. But do not how to enter the dimensionless equations for density, viscosity, Reynolds number, Weber number, and Froud number as given in the attached papers. Can anyone please help in this problem. I shall be very thankful.
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Dear Thamasha, I understand what you mean, but I am confused. As in Sussan paper, we non-dimensionalized the density, viscosity, and the conservations all. Now to characterize the viscosity we used Reynolds number, for surface tension, Weber number, and gravity by Froude number. I can understand these all. But tell me that viscosity is non-dimensionalized separatly and it should be determined from the Reynolds number. How can I use them simultaneously to define viscosity. Also how for density. I do not how to define the viscosity and density of two fluids. Please can you make a simple mph model to show this. I shall be very thankful.@ Thamasha Samarasinghe.
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Hi,
In relation to the coupling of fluid flow (gasoline) with magnetic field (permanent magnet) in experimental articles it is mentioned that in the presence of magnetic field, fuel properties such as density, surface tension and viscosity will change. I simulated this problem numerically recruiting the finite element method but I don't see these changes. I appreciate your help in advance.
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Hi Thomas Cuff , I have seen quite a number similar patents.
Just like peer-review, the patent system isn't perfect and sometimes something gets patented that shouldn't be. It can be enough to claim a new twist on an old idea (like a magnet around the fuel line and the air supply of the engine, as in your example) and sometimes, maybe, the good people at the patent office just had a bad day. This problem is not limited to implausible claims, sometime ago we were troubled by a competitor's patent even though all the claims in said patent were already described in much older scientific literature...
Patent applications should contain novelties (1) and be non-trivial (2). But generally, neither of these two criteria will lead to an obvious and sharp demarcation.
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I am currently working on cosmetic formulations.
I transferred the samples of emulsion into 50 ml bottles.
They were then held for a week at either room temperature (23 ±1 °C) or -15 ±1 °C before being heated to 23±1 °C.
However, when I measured the viscosity of samples, it appears that the cold sample is more viscous after thawing.
Does anyone have any ideas on the cause of the increase?
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When you cool your emulsion, it turns into a jelly. If the jelly was stored for a long time, irreversible changes occurred in it under the influence of bacteria and time. After heating, these changes remain and change the viscosity. Compare the IR spectrum of the jelly immediately and after storage and you will see the difference in the spectrum.
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For my research work I need the viscosity of quartzofeldspathic fluid in different metamorphic facies (specially, amphibolite). Is there any research work on this? Please help
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Dear Sir,
I said in my previous message that it is a fluid composed of dissolved rock. I don't think you will find any work related to the viscosity of this liquid in the literature since it is of little interest.
Regards
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I want to measure the zeta potential of spherical particles (d=30µm) with different surface modification. Unfortunately, the particles precipitate during measurement. Can I increase the viscosity of the fluid, e.g. by adding glycerin, to slow down the precipitation and enable reliable measurements? What other work-arounds are possible?
Note: I am not aiming for absolute values of zeta potential but rather would like to compare differently modified particles with each other and obtain a relative statement.
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Measure the sedimentation potential!
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I got my viscosity study data which includes shear stress, shear rate, viscosity, and torque and now I want to find out how to calculate shear train, storage modulus, and loss modulus from these data?
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Hi Amir,
i agree with Miomir Miljković in that with a rotational test only viscosity can be measured. Actually shear stress is a measure of the torque, multiplied with a conversion factor, and shear rate is a measure of the rotational speed of your meausuring geometry, multiplied with another conversion factor. Viscosity, finally, is the ratio between shear stress and shear rate.
Storage and loss moduli cannot be generated with a preset shear rate (or shear stress), but you need to perform an oscillatory shear test, with preset strain and(!) frequency. Storage and loss moduli will then calculate from shear stress and strain (their ratio equals the complex shear modulus) and the phase shift angle. This phase shift angle provides information about the viscous and elastic fractions of material behavior, which then translate into loss and storage moduli.
This also means that oscillatory tests can be performed not only on solid materials, but on the entire range of materials from solid, over visco-elastic, to liquid (with suitable measuring geometries). This is, in fact, the particular strength of oscillatory tests compared to rotational tests.
Good news is that oscillatory tests can be performed with the identical setup as for rotational tests, assuming that an (air-bearing) rotational rheometer was used.
If you are interested in the Basics of Rheology i can recommend the following Wiki page:
...or eLearnings:
Best wishes
Christopher
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I'm currently looking at the rheological properties of the polymer Xanthan Gum. focusing on its dynamic viscosity to be more specific. I'm assessing the effects of pH (ranging from 3.6 to 5.6, 0.4 increment, total of 6 pH's) on the dynamic viscosity of xanthan gum solution (dissolving xanthan gum powder into acetic buffer with equal ionic strength, concentration is kept at 0.04%).
Firstly, my viscosity data collected shows that, as pH increases from 3.6 to 4.0 then 4.4, the viscosity increases; but as I bring up the pH from 4.4 to 4.8, 4.8 to 5.2, then lastly 5.2 to 5.6, the increasing viscosity trend plateaus and the increase in viscosity is less significant compared to the 3.6-4.4 jump. At this range, does pH has an effect on the viscosity of xanthan gum based on its molecular configuration? Though some sources states that xanthan gum's viscosity remains stable and unchanged within the range of pH 3-12 at a high concentration like 1% not 0.04%, yet some suggest pH still plays an effect, though I'm not sure how on the chemical and molecular aspect.
A possible conjecture I can think of is the xanthan gum's order-disorder and helix-coil transition is affected by protonation. In figure 2, it demonstrates how electrolytes affect the structure of the polymer; in figure 3, it shows how at a state of a helical rod and no longer a random coil, it is capable to hydrogen bonds among each other. Hence, I'm wondering of pH plays an effect on it's structural transition, such that the increased intermolecular forces at the form of a helical rod would make it more viscous in solution.
Here are the resources I have used so far:
Brunchi, CE., Bercea, M., Morariu, S. et al. Some properties of xanthan gum in aqueous solutions: effect of temperature and pH. J Polym Res 23, 123 (2016). https://doi.org/10.1007/s10965-016-1015-4
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Dear Ryan Lo, you may find various stufies on this topic. Please have a look at the following free access RG fille. My Regards
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During our rheological measurements, we have often solved one problem. We measure viscosity on an extrusion machine equipped with a rheological head. We need the value of density of rubber (ex. natural rubber) for the calculation of viscosity. The measurement is at an elevated temperature (ex. 110 °C).
When we measure the viscosity of plastic, it is simple, because we can measure the density on a melt flow index machine (MFI). Natural rubber is almost unmeasurable on MFI. So we tried the pycnometer, but there we can measure only to the app. 90 °C. We measure the density at four lower temperatures and we use some curve to get the density at elevated temperature. I think it is not the best technique, but we haven´t found better.
Thank you for some advice.
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We can use the capillary rheometer to measure the density of a melted or high temperature polymer or rubber sample. You can also test the compressibility of it at different pressures or temperatures. This is a test in the Rosand capillary rheometer system. If you'd like to have this done by contract testing, please let us know.
Best regards,
Phil
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Thanks in advance for valuable information.
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Dear Avaz Yangiboyev, please have a look at the attached file. My Regards
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I am preparing a 5% GelMA hydrogel in PBS using APS and TEMED at 20mM concentration. Even after long exposure to UV, there doesn't seem to be any change in the precursor solution. Not even any viscosity changes. Any idea why this might be so? What might I be doing wrong?
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APS and TEMED are thermal initiators, so you have to introduce heat in your system to start the polymerization reaction. Usually, it is done by heating up at 37°C for a small period of time, or overnight at room temperature, to assure that the curing is complete. Today, there are some photoinitiators that could assist your intent, especially if oxygen is depleted from your system. LAP is one of the best ones. It is water-soluble, of relatively low toxicity and can be started even with blue light (405 nm)
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I bought a XL7 viscometer to use on-line the production of adhesive and speed-up the process.
Nowadays, I use a Brookfield viscometer in lab. So I have to stop the production to take a sample to the lab and make the viscosity measurement.
I tried to make some measures with the XL7 in off-line, using it immersed in a sample like the Brookfield.
But the viscosty value are really different between the Brokfield and the XL7.
What can I do to find a conversion factor between the two viscometers for all my different types of adhesives?
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Hi Guilherme,
If your fluid exhibits non-Newtonian behaviour, then these two types of measurements will yield different results due to different shear rates.
There is a section in the VP550 processor user manual supplied with your XL7 that explains how to match readings to a reference viscometer. To achieve this you must use the SPAN function.
To calculate the appropriate value of SPAN, measure the viscosity of a fluid using both viscometers at the same temperature and take the ratio of the two readings. i.e. SPAN = Reference viscometer reading/Hydramotion viscometer reading. Then enter this value into the SPAN menu.
If you require any additional assistance or further detail, then please contact Hydramotion service team directly.
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what is the difference between the Kinematic Viscosity and dynamic viscosity, what is the applicable condition?
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Dynamic viscosity and kinematic viscosity are the two forms of viscosity that exist. Each one represents liquid flow in a distinct way. When the density of the fluid is known, they can be used interchangeably.
The ratio of shear stress to shear rate determines a fluid's dynamic viscosity.
Kinematic Viscosity - The ratio of viscous force to internal force determines a fluid's kinematic viscosity. The diffusion of mass and heat is analogous to kinematic viscosity.