Flow - Science topic

By way of supplement and, in part, objection to the previous reply. Piaget's epistemology is certainly quite good and describes human gnostic processes quite comprehensively. But as I understand it, the original discussion in this thread (and the discussion that was the premise of this one) was not about cognition in general, but about the motivation and drive to learn very specific areas of knowledge, namely, academic subjects in higher education, in the academic form of that higher education. Of course, humans and new information interact, but often humans choose the information with which they feel more comfortable interacting. The rest of the information often passes by his consciousness, or has very little effect on him. And then the question of motivation, aspiration to self-organisation comes to the fore. As a pedagogical approach and concept explaining student's motives and actions, I am closer to the approach of existential pedagogy and phenomenological method

Dear Krishnanand, MFI is only meaningful for polyolrfins (PEs and PPs). Most probably this is due to the plasticization effect imparted by TPU to PLA. The solutions are either to crosslink or graft TPU into PLA matrix. My Regards

Hi Lucille,

For inducing cell death/apoptosis, I have put cells that are in a 1.5ml tube into a microwave-heated boiling water for 5min and put it back on ice for 2min, and repeat for 3 cycles, and I get ~80% annexin V + cells. This is done with mouse lymph node cells, and I am not sure if your image showed the staining for platelets in all conditions, but you don't need platelets to be your positive control for Annexin V staining.

Another way of inducing apoptosis specifically is to use a drug called staurosporine (1285, Tocris) and you can check this paper ( ) for how they did it in cell culture in vitro.

Hope this is helpful,

Zhixin

I too would like to ask, did you find the answer? I am planning to do the same.

Maojin Gong This AI response is not false as it could be sufficient for a reader Lamda. However, it is not scientifically accurate as we are on a research thread. Furthermore, it does not display the mentioned references...

Maciej: The short answer to your question is no (as far as i know). The main challenge is defining a proper length scale in Re, and the sensible solution is to use some hydraulic diameter for internal flows, and the local position for external flows (flat plates, aerofoils, tubes etc). The main thing is that Re in some way should relate to the boundary layer thickness, which can be difficult (This is why the Nu and Cf for developing flows must be corrected with a d/L-expression for internal flows). Some attempts have been made at using the momentum thickness as length scale, which has showed some success in estimating the transition to turbulence.

There are several main factors to consider:

1) Seed particle characteristic response time which is related to Stokes number. This should always be explicitly calculated for any PIV investigation and is one good gauge for how well the resultant cross-correlated particle velocity represents the actual flow velocity

2) Overlap ratio. In regions with sharp gradients you must pay more attention to using the correct/most advantageous overlap ratio between iterations to best capture the gradients

3) The relative magnitude of your velocity fluctuations to your mean flow. Like any measurement instrument, you have a limited bandwidth. If your fluctuations are on the order of 1/100th or above of full scale/mean you should be able to get reliable measurements without resorting to specialized approaches. Fluctuations below that may still be possible with PIV but require more novel approaches.

4) Based on your physical and assumed temporal scales, you will need to be rigorous in your application of optical distortion corrections as they may be on the order of the magnitude of your fluctuations

Liquid-phase working medium inside the reactor is simulated formation water, and the gas phase (CO2+N2) is above.

Howdy Filippo Maria Denaro ,

You might find the thought experiment in my previous post interesting. It is a consequence of your suggestion that I read Sir James Jeans An Introduction to the Kinetic Theory of Gases and my choice to read his The Dynamical Theory of Gases as well. Writing the thought experiment triggered greater insight into processes because I had to address problems with answers that ring true. It also produced a richer view of a laminar flow past a cylinder with believable cause of curvature. I really appreciate our discussion that has led to it.

Happy Trails, Len

A good writer in science and/or arts will develop further and beyond limits.

There are some excellent ultrasonic flow meters available but read carefully claims of accuracy and note all disclaimers. While these might achieve a high level of accuracy under certain ideal conditions in a laboratory, this does not mean that you can stumble up, clamp one on to any old pipe anywhere, and measure the flow to that same accuracy. Accurately measuring any flow in any pipe is an extremely difficult and complicated task, regardless of the instruments used. There are many good references on this subject published by ASME, CTI, IIHR, USNRL, TVA, etc.

Hi Mustafa,

our tech support team is happy to help with your question but would need a bit more info on your research question, experimental setup, etc. Please get in touch via Email: techsupport@ibidi.com

I am using FACSCanto || which has 3 laser with 9 color, and i will stain surface and intra for the same cell.

Richard Fenner and Steve Mounce have done work using Kalman filters for leak detection in water distribution networks Seyed.

Assuming no change in channel height, this is a conservation of energy situation in which some of the fluid's energy is in the pressure and some in the kinetic energy of the fluid. Because the mass flow rate must remain constant, if the cross-sectional area of the fluid is raised, the fluid's speed will also increase , but the pressure in that section of the channel will decrease to main the mass flow rate at constant

Hi, I think you may be getting confused. The numbers of the axes are not voltages, but is a scale of fluorescence intensity.

I'm not sure which instrument you are using, but check that how you are exporting the data files as this can affect what you see on FlowJo. Nonetheless, there can be a slight difference between what you see on the instrument and what you see in FlowJo.

Also check that when you optimized your voltages, were you looking at FSC height, area, or width on the instrument? I see on the picture you put that you selected area, just check if that's what you used on your instrument.

If all else fails, email FlowJo support for assistance. They are really helpful

Yes, the project finished in 2016. You can see some of the settings in this publication:

The depends on the depth of erosion you want to define. The assumed flow depth is the local depth immediately ahead of the supports or abutments.

Running related "high" or coherent experiences is an everyday passion, as expounded in attached.

Interesting

Dear Aydin Donmez

Note that by default, Venturi flow meters offer an accuracy of around ±1% of the discharge coefficient. Optimum calibration allows an even greater accuracy of up to ±0.25%. Venturi nozzle flow rate measurement systems are marginally more expensive than orifice-style flow meter systems.

Kind Regards

Hello Prof.Sean,

Check on this website

Hi, thanks for sharing the links. The daily and weekly flows between CBG to POI, CBG to CBG are gathered in the first two links, are there any sources that covers POI to POI inside a city?

Flow rate is volume divided by time. So just put a floater and determine the time the floater goes round. Secondly determine the volume of water that you are stiring. This will give you a flow rate. Though this flow rate is higher than the middle one.

Hi,

We used devices repeatedly made up of PDMS as well as other materials with pathogenic bacteria. As long as the materials are Autoclaveable there is no problem in reusing them. Infact the current scenario of having sustainable development contains inherent clause of showing how we can use the same devices for longer periods with use of minimal processing. Apart form that, technically PDMS has shown to provide good results as long as the devices made from it are sterilized meticulously. It all percolates down to how good your skills are while handling cell cultures!!!

Regards

Amit

Please follow the link attached to get your answer

Thank you, Brett Boisjolie, for discussing this issue. Since I live in a Himalayan region, we are still coping up to bring automated data loggers in our hydrological assessments. Usually, the systems we use are stand-alone systems that record data, which field workers manually pick up. However, in downstream areas wherein cellular networks are available, the data is continuously logged and sent to the admin while storing that in the cloud too...

Thanks

Interesting question. Fluent provides you platform for using different input boundary conditions. But it requires a proper meshing and validation of the experimental results. You somehow have to formulate a process of extracting the input boundary conditions from the IR image.

Raju Kumar , what is the initial temperature of the oven ?

In my hands cell loss was largely due to the fact that there are many centrifugation steps (more than in FACS for instance), and I really compared lower vs. higher centrifugation steps and this appeared to be one major parameter that could reduce cell loss. I also thought 1000 x g was too high and would harm cells, but it worked like a charm and it might be even possible to go higher (I also did not mention that I began working at 800 x g, just like you, and I spun at 800 x g for all centrifugations until the methanol step).

I don't remember having big issues with aggregates, but I was working with human PBMCs and not bone-marrow cells so this was a bit different from you.

However, before I figured out that increasing centrifugation speed and working in V-bottom plates reduced cell loss, I tested if treating cells with DNase could help. The reason why I tested this is because I was suspecting dead cells (following the cisplatin treatment, which stains dead cells but which also induce cell death) to activate cells and/or to create some smears that would impair the process (trapping cells from the pellet, that would then move to the supernatant, for instance). Maybe that could be something you could test in your case ? Another thing we tested, but this was a pain in the neck, was to check the presence of cells in the supernatant after each centrifugation step, but I don't remember something spectacular from this and if I remember correctly number of cells found in the supernatant just began to increase after the methanol permeabilization.

You might want to start with lattice-boltzman schemes, as I think they offer an an easy to understand introduction into numerical simulations. There is this python library pylbm ( https://pylbm.readthedocs.io/en/latest/). You could check out their example gallery to see if it's sufficient for your purposes..

Dear Kanishk Sharma,

ANSYS does not possess the ability to perform direct computations with deformation theory of plasticity.

However, in the case of monotonic loading, the Multilinear Elasticity (TB,MELAS) can be used. The material behavior is described in this case by a piece-wise linear stress-strain curve. But the unloading is not linear and there is no hysteresis behavior.

Many years ago, I have implemented the deformation theory of plasticity into the finite element programm PANTOCRATOR (C++ code) developed in the St. Petersburg polytechnic university. Comparison of the finite-element simulation results for the deformation theory with the flow theory has shown their coincidence under proportional loading and strong differences under non-proportional loading.

Dear Dr Tawaha, according to following reference, the optimum flow rate of water in NTF for lettuce ranges from 3 to 8 L/square meter/hour i.e. 50-133 mL/square metre/minute.

Ref: Soilless culture: Theory and Practice. 2nd edition. 2019. (Eds. M. Raviv, J.H. Lieth and A. Bar-Tal).

With best regards Brahmanand

Dear Hadi

Actually I like using draw.io

Full link: https://www.draw.io/

I have a list of build-in templates and tools for different aspects.

The main advantage is the ability to save the diagrams as pdf files.

Dear Mr. Thomas Frank.Thank you for your answer. I found exactly what I was looking for in the book that was recommended by Bachir Achour

Hi Kalpana

Lots of other manufacturers out there as well, e.g. GE Druck for industiral sensors, Kistler for more scientific sensors.

https://www.instrumart.com/brands/819/druck

https://www.kistler.com/en/

Take a look here for something that may land in between

https://www.setra.com/product/pressure/differential

I believe that Setra offers both typical strain based pressure sensors as well as capacitive pressure sensors. My guess is that the latter has a wider signal to noise ratio.

That said, amplitude resolution depends on how you digitze your signal - if you m

measure an analog output signal.

Sincerely

Claes

Dear Dr. Majeid Heidari ,

It would be appreciated if you explain more about the method you used to simulate the POROUS MEDIA for your Ph.D. thesis.

Best regards,

Mehdi

In developing flows Reynolds number is a function of length and so is the arc of bend. If it is developed flow, with arc radius less than 10.33 mts ( atmospheric pressure head) the reynold's number is independent on arc radius and dependent on diameter. As long as dia is constant, there is no variation of reynolds, number.

But if the bend is sharp, the fluid creates a back pressure on the incoming flow, which will mostly make it unsteady flow pattern, where sudden drop in pressure occurs ( can be calculated using darcy-weisch bach relation) and suitable friction factor can be assessed. We can use reynold - calburn analogy to obtain Stanton number, with this we can arrive at reynold's number of the associated flow, at down stream of 180 degrees bend.

Hi, ABS is a powerful tool but the most important think is to determine your agent , what I would suggest is to perform the Arena the simulation of your current system and check how the system behaves than you can model your system , it has OPTQUEST for optimization but I would not suggest that as it is just hit and trial method but what arena will do will provide you clear picture of your system with current waiting times and utilization value added etc times , after that you can use PSO or GA to solve the problem

@R. Guy Grantham Can we discuss about your research?

Yes, you can by assuming the tube to be locally Cartesian.

Greetings!

While not as precise as using a current meter, you can still get decent results using the float method. I offer a few suggestions below:

Float Choice. I agree with previous comments: Oranges are an excellent float because you want a float that is just below the water surface. If you use a stick or an empty plastic bottle, for example, any wind you have will likely influence your results. Oranges are relatively cheap (at least in the US) and they are biodegradable if you lose one in the stream. No matter what you use, it needs to be just dense enough that it sits just below the water surface, but doesn't sink or hit the bottom. Oranges fit this requirement. A half-filled plastic bottle might work, too, in an emergency.

Measurement Reach. This is not going to be an issue in a concrete trapezoid, but find a straight reach with minimum turbulence. There shouldn't be any constrictions, bends, or other other obstructions within about 5 channel widths up or downstream of your selected measurement reach. The more uniform the flow, the better the results. If present, you can remove wood, rocks, debris, etc... before you start the measurement. Just make sure you wait a period of time to allow the flow to become uniform again--15 minutes is a good rule of thumb, but it depends upon the size of the obstruction versus the size of the channel. You'll need to read the reach to decide when it's appropriate.

The section should be long enough such that you get at least 20 seconds of travel time for the floats. If you are doing storm event measurements, at the start of the measurement, you need to note the location of the water surface elevation as you'll likely have to come back later and measure the cross sectional area when it's safe to do so. In baseflow conditions, you should be able to measure the cross sectional area at the time you do the work.

If your intention is to go to the same site or sites in fair weather and foul for multiple measurements, I suggest that you monument or mark the measurement section. That way, you don't need to string a tape every time you go to a site. It's a time saver when you're working in the wet, in particular.

Finally, realize this--it is typically very difficult to find the perfect measurement location for a discharge measurement, no matter how you do it. Find the best site you can and do the best you can! Take lots of pictures of your site, take good notes during your work, and caveat your results as necessary in your write up.

Taking the Measurement. You need to sample the entire section, slow parts and fast. Don't just throw five floats in the middle, for example. In your mind or your field book, break the reach into two or three sections (example: Right Side third, Middle, Left Side Third). How many sections you need is best professional judgement.

In each section, I would recommend at least five measurements (so you'd have 15 data points in the example above). Also, make sure you introduce the float upstream far enough so that it has time to accelerate to the stream velocity before it crosses into the measurement reach. Use a stopwatch to measure the time needed for the float to travel to the downstream point of the measurement reach. I'm sure you realize this, but this type of flow measurement is usually a two person job.

Data Processing. Nothing to add here, really. You simply divide your measurement reach distance by the individual float travel times to get the individual surface velocities for each measurement. Then, I typically average all the measurements to compute an average velocity for the entire section. Once you have your average velocity, one important thing that was touched on before is you need to correct surface velocity measurements to average velocity measurements as surface values are always faster. The standard formula is:

Vavg = kVsur

where k is a correction coefficient that ranges from 0.80 in natural streams to 0.90 in artificial channels. Commonly, 0.85 is used--I might go to 0.90 in your case, based on your site description.

Final Thoughts. I don't know what your reason is for measuring discharge here, but if you are working long-term and you want to understand water flow at this location, you might want to install a staff plate and develop a rating curve for this site. Eventually, that would allow you to go to the site, take a reading off the staff plate, and get an instantaneous discharge value without having to measure it every time. That process, however, is too involved to describe here. But there are all kinds of references on-line for developing rating curves.

Good luck!

Amin Rahdarian Agree, as long as the Courant number of your model is less than the recommended maximum value, the time step of the model should not be the key reason for the model to blow up or to cause unrealistically high water levels.

For surface elevation type of boundary condition, is there a recommended time step a time series boundary data? Will the time step have an impact on the simulation stability or extremely high water levels?

Dear Alaa Temimy,

you can be fairly certain, then all commercial codes available on the market are free of coding and algorithmic errors, i.e. they implement a numerical method for the solution of your problem correctly.

However, the numerical method itself, inherently, includes sources of error. These come primarily from space and time discretization (computational grid density and time step) as well as from which method has been used and terms up to which order have been neglected.

Furthermore, the mathematical-physical model, employed to describe the process you are simulating, is usually also an approximation of reality. For example, we know fluid viscosity is temperature dependent, but we choose to neglect that in our simulations, etc.

If the problem simulated is non-linear, a user-prescribed criterion is usually used to set the desired lowering of the error norms, which also contributes to the overall error.

My suggestion is to first identify all sources of error and try to keep them of the same order.

Secondly, one should always perform a nodalization analysis (and possibly a Richardson extrapolation) to examine, how the solution changes when different grids and time steps are used.

A short answer to your question, it is impossible to give a percentage to estimate the accuracy of a simulation. And beware, the accuracy does indeed depend on the expertise of the engineer doing the simulation.

I might try looking at the rainfall in periods from the last vegetation assessment to the current vegetation count. I could see that an average rainfall might be important. Variance and periods of flood or drought might also be important. Before analysis, I would try graphing the data. Relationships might not be linear. I would also expect thresholds. Flooding for 2 days has little effect, but 3 weeks causes more extensive damage.

Temperature might influence vegetation growth as much or more than rainfall.

For water, the continuity equation reduces to the divergence-free constraint divv =0.

this link is useful

https://www.flow3d.com/.../Numerical-investigation-of-the-effect-of-...

regards

You can use the Developed power flow from this link

https://www.gams.com/latest/psoptlib_ml/libhtml/index.html#psoptlib

I fully agree with previous answers. But your question is not clear enough.

the distribution of fluids (previous history) and wettability (if the viscosities are similiar) are the controlling factors for the pressure needed to flow. involving capillary pressure muddles the issue.

For example, if your water saturation is 40 % and all the other variables are the same. Not all the pores have 40%! some will have 100% and others 20%. Therefore, the pressure drop will be different for different pore size distributions, mainly if they are not unimodal.

Also, during imbibition and drainage at the same saturation you will have different fluid distributions and as a consequence different pressures.

Hi Feichen and all.

OK: no loose particles migration and pore blocking. Then, the porous medium itself could be undergoing compression during experiment, thus reducing its permeability (Cf. Darcy’s Law). In this case, a constant flow rate would give what you getting: an increasing pressure drop. Try a constant very small flow rate. It will give a very small pressure drop, hopefully not enough to compress the medium and the pressure drop will be constant. If that is the case, you’re dealing with very compressible porous medium. If it is unavoidable to deal with this medium, for a given flow rate, you will need a large cross section so as to have low velocity and low pressure drop.

You can consider two parameters:

1) the mass flow rate, if it is taken constant an increase in the diameter causes a diminishing averaged velocity.

2) the Reynolds number, if the averaged velocity is taken constant the Re number increases. From 0.20 to 0.25 you are increasing the 25% and the Re number can be such that transition to turbulence can occur,

Dear Aaron Altman

Thanks for your suggestion.

Thanks to you Ahmed.

I will examine it and give you feedback soon.

Thanks again.

Joseph

Yes

consult this link

Sharing link:

Regards!

Dear Sir,

Experimental study with numerical one for nanofluids is very interesting. But when we go for experimental part, the entire results are different. The trend was same but numerical value has great difference. As there are number of parameters which come into picture while doing experimentation which was not considered in numerical analysis.

Good luck

This leakage should be a function of speed and pressure.

If your  undergraduate work is related with environmental flows , perhaps it could be useful to read Chapter 9 (turbulent jets and plumes) of the now classic book by Fischer, List, Koh, Imberger and Brooks "Mixing in Inland and Coastal Waters"

Thank you Patrick

Dear Velusamy,

There are 3 ways that grains can move: 1. lifting of the grain off the grains beneath it. 2. sliding of the grain up and out of its position on the bed. 3. rotation of the grain about a pivot point formed by neighboring grains

For case 1, lift forces must exceed the “gravity force” (i.e. the weight, since gravity itself is an acceleration) For case 2, drag forces in the direction of easiest movement must exceed the combined frictional and gravitation force in the opposite direction For case 3, the moment of the fluid forces must exceed the moment of the gravitational force.

Fluid force is the resultant between lift component and Drag force.

http://www.sfu.ca/~hickin/FLUIDS/Chapt6-Sediment%20transport.pdf   (Page 6.19)

With my best regards

Prof. Bachir ACHOUR

Hi Kelly,

If you expect to see fluorescent shifts in the colors you are interested in I would suggest compensating.  Although the GFP may not contribute to the other fluorophores in this experiment, but it may in the future.  It's a good habit to get into because it eliminates one more confounder.  Finally, if you're using FlowJo you can remove the compensation after the fact and look at the differences.  Here is a article (of sorts) on compensation.

Good luck,

NM

Thanks Mohammed

You don't need to select the moving mesh. Just select the boundary of the cylinder as 'wall' and specify the wall as moving, then select 'rotating', then put the rotating wall in ' rad/sec'.

Friction will be the main reason to reduce the RPM even the power increases.

you can insert a plane in the position you interest and then insert vector in that plane, this will help you to see the velocity vector and if you interest about the vorticity you can export it from FLeunt and select it instead of vector 

Thanks for your favor, Dr Adel Oueslati.

Dear Renan Thomes,

I am happy that (atleast) some of my advice proved useful. From your (I must say pretty extensive) searches and simulation attempts, we are now confident that it is NOT the rate of mesh/grid extension/expansion/coarsening that is the problem. Further, you stated that you had already tried refining the mesh which didn't lead to major changes in the results. So at this stage we can (probably) assume that it is NOT the grid that's the problem.

My experience in CFD tells me that ONE computational framework (or solver setting) cannot conquer all cases of a given problem....in your case....different values of Re of flow over the sphere.

One has to understand the balance between inertia and viscous forces in a given simulation (hoping that those are the only two things we need to worry about :))...my Ph.D. senior taught me that (♡). Hence, for 20 < Re < 200, the flow is comparatively more advection (inertia) dominant than when Re < 20. Hence, there is a risk of artificial/numerical diffusion contaminating the solution at larger Re...so, a higher order (LinearUpwind in your case) scheme is necessary. On the other hand, because the low Re flow would be diffusion (viscous) dominant, a (pure) first order scheme would probably suffice and using a higher order scheme there may involve a risk of over-predicting velocities (which higher-order schemes do...by the way). 

Regarding the free-stream velocity being 1.03 m/s far away from the sphere...the free-stream velocity will increase AROUND THE SPHERE due to flow separation since the domain has to accommodate the same flow-rate (across any section) regardless of separation bubbles getting formed. But far away from the sphere...a 3% increase in free-stream velocity might be of some concern...hope you are not using WALL/SLIP/NO-PENETRATION conditions at the domain boundaries....What you can do is carry out a flux-balance between the inlet and the outlet (an option available in FLUENT but not sure about OpenFOAM)....the inlet-outlet mass flow rate difference should be around 1e-15 kg/s (or m³/s) or less to ensure that there is no volume dilatation in the domain. 

Regarding your attempts towards validating the analytical solutions...I think the expressions are in terms of radial (U_r) and tangential (U_θ) velocities...so I hope you used some kind of transformation to convert them from curvilinear (r,θ,z) to Cartesian space (x,y,z). Regarding the differences between simulation and analytical values....the analytical solution neglects all acceleration effects occurring during interaction with the sphere (as stated in the MIT-OCW document). For instance, analytically, the vertical velocity (W) is consistently zero above the sphere which is not possible in practice (observable in your results). Moreover, the U-velocity above the sphere ought to be more in practice (also observable from your results) because of the "crowding effect" (also mentioned in the MIT-OCW document).

But the fact that the free-stream velocity will actually decrease for creeping flows (Re<<1) has really "damaged my intuition" :) :) :)...

I hope you will be able to find a solution to your problem for Re<20 as well Renan. It was really nice having this discussion with you.  

Best regards.

Shaswat Saincher

Thank you everyone!!

Dear Mohamed,

I invite to take a look at Ph.D. thesis that can be found in the following link (it is in french) :

or at the article :

I have studied single phase flow and two-phase flow (condensation) inside BPHE. In general there is no single value for "critical" Reynolds number. I prefer not to call it critical because it is not a transition between laminar and turbulent flow. it is in fact a transition between helical flow and zig-zag (cross-flow). this Reynolds number represents the transition between a dominant helical flow for Re < Re_cr and a dominant zig-zag flow for Re> Re_cr.

the value of this Reynolds number depends on the geometry (inclinaison angle, corrugation pitch, plate spacing). In my Ph.D. , the first part is about single phase flow where you can find all the previous informations.

I hope this will be helpful for you.

Kind regards,

Kifah SARRAF

Thank You Sir

I did fail to mention, a plastic pipe with clear, watertight plexiglass viewer at bottom was sometimes useful in fast and shallow waters to see some darters and sculpins.  These are commercially available, and handles on the plastic pipe help to hold in place or move as needed.  Would not work well in highly turbid or bubbly waters.  The view is limited, but still may be useful in some circumstances.

u can use same EES of vertical plate itself...am not sure 100% let me check 

Yes, but not only vorticity is important. You are also to take into investigations the geometry of the nozzle

I have to maximize hvdc transmission power. 

 Thank you for your answer and publication you have recommended, I just wonder which kind of model she will use in pulsatile flow research for crossflow.