Experimental Fluid Mechanics - Science topic

Dear all,

I am facing the same issue. Could you guys show the solution of this issue?

Thanks

Hi Noraihan,

In mathematical perspective it is just a method to reduce the dimensionality of System of PDEs to ODEs.

Amouiri Raouf There are various software alternatives for modeling thermofluid design applications, each with its own set of advantages and disadvantages. Among the most common choices are:

1. Comsol Multiphysics: Comsol is a commercial program used for thermofluid simulations. It has several capabilities, such as heat transport, fluid dynamics, and structural mechanics. It also provides an easy-to-use interface and a number of add-on modules for specialty simulations.

2. ANSYS Fluent: Another commercial product that is commonly used in thermofluid simulations is ANSYS Fluent. It provides excellent computational fluid dynamics (CFD) and heat transfer modeling capabilities. It also includes a diverse set of physical models, boundary conditions, and computational approaches.

3. OpenFOAM: OpenFOAM is a free, open-source program used in CFD simulations. It has several capabilities, such as fluid dynamics, heat transport, and mass transfer. It also has a big user and development community that may help with support and extra tools.

4. SimScale: SimScale is a cloud-based commercial product that provides a wide variety of thermofluid simulation features. It contains an easy-to-use interface and a number of add-on modules for specialty simulations.

5. Simcenter: Simcenter is another another commercial program that provides a wide variety of thermofluid simulation features. It also has additional simulation features, such as electromagnetic and multiphysics simulations.

6. Python, R, and Wolfram Mathematica are general-purpose programming languages that may be used to create thermofluid simulation scripts and applications. They are frequently used alongside other simulation tools, such as OpenFOAM or ANSYS Fluent.

What software to employ together is entirely dependent on the exact situation and amount of complexity. For example, if the problem is complicated and necessitates specialist skills, such as multiphysics simulations, employing software such as Comsol may be the best option. If the problem is simple and simply requires basic CFD simulations, software such as OpenFOAM or SimScale may suffice.

I don't understand your problem. Do you generate steam mixed with air at 100 C at above ambient pressure, or is it ambient pressure and you are sucking vacuum (since you have pressure drop in valves)? Anyway, there is no straight forward answer to the temp. reading. You may have measurement errors if the sensor is not properly insulated or calibrated, it may also be due to heat loss, since you have a significant amount of inert gas present. You should carefully check your measurement system before diving into speculations.

Academic resources on Fluid Mechanics are provided on

SINGLE PHASE AND MULTIPHASE TURBULENT FLOWS (SMTF) IN NATURE AND ENGINEERING APPLICATIONS | Jamel Chahed | 3 publications | Research Project (researchgate.net)

definitely you can. Please follow the article attached to get more information

Oras Khudhayer Obayes Thank you for your answers.

This might be useful:

Hi Dinar,

what is a CIRCULAR pipe? Is it a pipe with circular cross section? If yes, then surely the radius and the lenght scale of energy-containing eddies near boundary matter. I am just thinking exactly about this topic and a nice application would be the Princeton superpipe, http://www.princeton.edu/~gasdyn/Facilities/Facilities.html ,

and/or the COLA pipe,

https://www.b-tu.de/fg-aerodynamik-stroemungslehre/forschung/ausstattung/colapipe .

Note also this theory-oriented paper:

If you see a chance for collaborative work, it could be nice. Only some research coins are needed: not for profit. For the honor only ...

In such computations I always compute the Re number based on the projected area.

You could use a pure copper pipe and spot weld to it small constantan (0.1mm diameter) single wires so making a series of T thermocouples. Be sure they are not electrically shorted on the cold side.

The copper tube will also ensure a temperature very close to the pipe internal one.

Thank you for your answer Alex. The problem is that the cc map is not at all Gaussian and often has fancy shapes that are not well fitted by a Gaussian. Hence the peak location becomes very ambiguous. I‘ll try to look for an example when I come back from holidays !

Ghassan Fadhil Smaisim which paper?

I should make a more specific statement on the ambient light that I was thinking of. It comes from any objects in the lab with their surfaces being able to reflect lights. In this case light source is most likely from the light scattering of laser beam or laser light sheet. The energy of such ambient light is undoubtedly much lower than that of light scattering. If there are objects with excellent reflective surface in the lab, chances are that such energy level may still be high enough to illuminate dark or even low-light area in the filed of view and sensed by the camera sensor with extremely high sensitivity. However, this situation is much less likely to happen because it causes safety issues and should always be avoided.

For open source PIV analysis tool, you can consider PIVlab, a MATLAB-based software package. I have been using DaVis for many years, and PIVlab for about a year. For now I don't see PIVlab is any different from DaVis in terms of velocity determination.

Soroush Abolfathi Many thanks for your response Sir

Not sure what kind of results/research you are trying to validate because that might influence how to answer the question. Is it surface pressures or integrated forces? What's the target Re range to know the susceptibility to flow separation across the range of angle of attack? Or is it a bluff body? Or is it simply flowfield data acquired through diagnostics (PIV, Hot-Wire, etc)?

All of these questions point towards the relative importance of reproducing the inlet geometry. Most tunnel inlets maintain some level of flow angularity in the entry to the test section. This is a good reason (along with boundary layer growth mentioned by above) to include the inlet geometry. Since it's a low turbulence tunnel, presumably tunnel turbulence intensity is relevant and should thus be correctly modeled.

Freestream component turbulence intensity reduction as a function of inlet to test section area ratio is given by 1/C^2 where C is the contraction ratio. So if you know the test section turbulence intensity you could back out what it would be post-screen and post-honeycomb or the equivalent of your inflow boundary.

Good luck indeed!

We have carried out some experiments in the past. They are described in the publication that I send to you. If you are interested in some, I can try to find the data

Alessandra

As the previous responses pointed out correctly, PIV might not be the right way for this case of the CW laser and 1000 Hz recording. You could consider using particle tracking and especially streaks particle tracking velocimetry. For that case I can recommend (disclosure - I'm involved in its development) the open source particle tracking velocimetry project, OpenPTV (www.openptv.net) or an excellent trackpy project.

Yes

consult this link

Dear researchers

usually water flow in porous media is too low especially for fine grained formations which may be regarded as laminar flow category. So what is the importance of scraping through this?

Update to readers.

Right now, we edit some points in the protocol then we get satisfied result as described

1. We reduce the concentration of BSA down to 2% w/v and we can see less cells get stuck while flushing them out.

2. Thinner PDMS. Maybe the thicker PDMS may accumulate more cells at the inlet and outlet. Gravitational force will pull cells into the ground and aggregate at the bottom of inlet and outlet.

3. Flushing cell out controlled by using syringe pumps is preferred.

I hope that the one who may encounter this problem can adapt some techniques posted by others and me to your work.

Best Regards,

Surasak

Please see the file here:

Go to the definition of discharge coefficient in https://en.wikipedia.org/wiki/Discharge_coefficient

Amin- You are right. You may use free wind speed if you are working on large Reynolds number. However, technically, you should be using relative wind speed, especially for small wind turbines. Thanks and best

Thanks and best wishes

Thanks for all  answers above!  It is finally found that the low frequency disturbance comes from the vibration of cantilever beam which is mounting my hot-wire probe ( I changed the weight of cantilever beam , the vibration frequency indeed changed as well.).  The microscopic vibrations of the hot-wire probe in the wall-normal direction in the boundary layer will cause this false signal ("a strong wall-normal mean-velocity gradient" is the source ). By using the traversing system which is  provided a prescribed pressing on the surface like “Komarik”  used by Borodulin et al. 2014 (https://www.researchgate.net/publication/283265027), this problem could be acceptably resolved. I am particularly grateful to Y.S Kachanov for his kind proposal of this question.

Dear Loo,

I just sent you the document (55 Mo) in your email box.

With my best regards

Prof. Bachir ACHOUR

You can also take a look at ISO 4287 and 4288.

I remember there was a table referring to the required minimum profile length.

Good luck

You can get dispersion error from your numerical scheme. Try decreasing your mesh spacing to see if the dispersion reduces. You could try using dispersion-relation-preserving (DRP) schemes. Another reason for inaccuracy is your boundary condition. When comparing against the analytical solution, do it at an instant when the wave has not reached the boundary, so you can isolate the effect of boundary conditions. 

Two vortices of equal strength and opposite sign are shed each oscillation period in the wake of a cylinder. The drag of the cylinder is however not sensitive to the sign of the vortex. This results in a period doubling compared to the oscillation of the lift (proportional to the circulation of the vortices).

For an airfoil, one usually consider an airfoil with an average lift. Hence there is symmetry breaking. An oscillating drag for an airfoil is as mentioned by Yuichi Kuya usually not dominated by vortex shedding, but by skin-friction, unless there is massive flow separation. If there is massive flow separation the vortex shedding is dominated by vortices with the same sign. Basically in both cases the oscillations in drag have the same cause as the lift oscillation and the same frequency (because there is no symmetry).

I came across this instrument which is a clip-on, so easy to use with existing gear. https://www.motionizeme.com/

It doesn't measure force, but if you integrate the data (and video) with good real-time speed measurement (so you get the change of velocity during the stroke), the 'skeptical young guys' will be able to observe the impact of changes to the stroke.

I am sorry I forgot to emphasis I need to calculate it for developing flow. Therefore I am suspicious about use of formula given in my previous post.

Dear Jyoti Prakash Panda,

I would suggest the following books:

(1) Turbulent Flows by Stephen Pope

(2) Advanced Engineering Fluid Mechanics by K. Muralidhar and G. Biswas

(3) Introductory Lectures on Turbulence (Physics, Mathematics and Modeling) by J. M. McDonough

(4) Lectures in Turbulence for the 21st Century by William K. George

Of these, (3) and (4) are available for free...just Google them.

Hope this helps.....best regards.

Shaswat Saincher

Making a parallel to what one usually does for a wing at incidence, the reference area for the calculation of forces should remain constant. For the cylinder it looks reasonable to employ the cross-sectional area across the axis of the cylinder (a rectangle). It should not change as the angle of attack is changed. However, it is also usual, for the calculation of other non-dimensional quantities, such as the Strouhal number for vortex shedding (which eventually will occur in this case) to consider the projected area in a section perpendicular to the flow direction (i.e. taking the sinus of the angle of attack) because, in this case, the physical phenomenon is actually directly depending on that scale. When accounting for aerodynamic forces it is a different situation and one definitely needs a fixed reference area (though different choices can be made) to be able to make a sensible analysis of the results.

Oops, thanks Xiang Lei. Of course - the higher viscosity phase displaces the lower viscosity phase if you want to see fingering. My mistake.

Happy to see your reply sir, but when i choose LES model in viscous , those options are locked. I couldn't able to enter the values.... 

Just mix some particle like hollow glass bead or TiO2 powder with some water. Add the mixture into the flume. Use the PIV image itself to adjust the density. Usually, several grams of powder was enough for a flume.

In an external flow or Internal flow problems

In General D (Diameter of cylinder) is proffered.

You might relate temperature to motor power and speed with a feed back controller, tuned to the character of the equipment.

Dear Arshan,

as far as I know, the Couette flow is used by NASA in rotating bioreactor for cartilage tissue engineering applications (a good resource for a start could be this https://smartech.gatech.edu/handle/1853/18174 or this http://ajprenal.physiology.org/content/281/1/F12). Also, the Magnus effect on a cylinder has been used for an exotic type propulsion, called "Flettner rotors" (http://en.wikipedia.org/wiki/Rotor_ship). 

Finally, I believe page 1 of this (ftp://ftp.nist.gov/pub/itl/div891/thesis-final.pdf) thesis contains all the information you need. I quote: "applications include rotary fractionation columns (Willingham et al. 1947; Macleod & Matterson 1959), heat transfer (Gazley 1958; Kaye & Elgar 1958; Becker & Kaye 1962; Kataoka, Doi & Komai 1977), electrochemical reactors using rotating cylinder electrodes (Gabe 1974; Legrand, Dumargue & Coeuret 1980; Coeuret & Legrand 1981; Gu & Fahidy 1982; Gabe & Walsh 1983; Eklund & Simonsson 1988; Gabe et al. 1998; Gao, Scheeline & Pearlstein 2002), membrane oxygenation and filtration devices (Strong & Carlucci 1976; Moore & Cooney 1995), and so-called "vortex flow reactors" (Giordano et al. 1998, 2000; Resende et al. 2001).

Other applications include continuous-flow photochemical reactors (Haim & Pismen 1994; Sczechowski, Koval & Noble 1995), and reactors for certain classes of chemical reactions in which a nearly uniform residence-time distribution is desired (Kataoka et al. 1975; Cohen & Marom 1983; Haim & Pismen 1994; Giordano et al. 1998). When the inner shaft has either an axisymmetric axially-periodic radius variation or has helical symmetry (e.g., a screw), applications include screw extruders (Griffith 1962; Kroesser & Middleman 1965; Tung & Laurence 1975; Choo, Neelakantan & Pittman 1980; Booy 1981; Choo, Hami & Pittman 1981; Elbirli & Lindt 1984; Bruker, Miawl, Hasson & Balch 1987; B¨ohme & Broszeit 1997; Broszeit 1997) used in polymer processing, and viscoseals or labyrinth pumps and seals (Stoff 1980; Rhode et al. 1986). Other applications include "through-hole" Schwartz et al. (1992) and "blind-hole" plating processes, and microfluidic applications of static mixers with helical elements (cf. Bertsch et al. 2001)."

Regards,

Andrea Antonello

Thank you  for your advice Wolfgang.

I've since come across several sources that use 2300 xg for 30 minutes to compact erythrocytes. This method has a strong positive correlation with methods such as cell counts so I have opted to use this in my study. I have tried methods similar to yours but have found the outcome to be inflated when compared to what would be expected from literature. If I find any other information I will be sure to re-post.

Alan

It is not trivial to calculate the droplet velocity emanating from the Taylor cone breakup in a typical electrospray application.

There are different scaling available which take into consideration balance between the applied electrical field, surface tension force and viscous force that determines the Taylor cone-jet stability hence formation of the droplets from jet breakup. The minimum flow rate scaling could be found in:

Scheideler and Chen, 2014, The minimum flow rate scaling of Taylor cone-jets issued from a nozzle. Applied Physics Letters 104, 024103, pp.1-4.

This is however only the volume flow rate and needs to be divided by the jet diameter to obtain the jet velocity. It should be noted that the actual nozzle diameter is much larger than the jet diameter hence should not be used to determine the cross sectional area.

A time-of-flight and energy analysis technique could be found in the below reference where the droplet velocities were measured for different electrical conductivity of the fluid. Please see Table 2 of this reference.

Gamero-Castano and Hruby, 2002, Electric measurements of charged sprays emitted by cone-jets, J. Fluid Mech., vol. 459, pp.245-276.

Hope it helps,

SM

Good day !

In my opinion BC with velocity distribution (= mass flow rate) at the inlet are more stable.  If you want use pressure at inlet nozzle then you need to prepare long input branch (5-7) diameters.

Best regards,

Serge

Dear Zoubair Boulahia,

Thank you for your answer and the document you sent. I'll try to learn about Camber from it first

Although, I have not worked on this specific problem, I am inclined to agree with your anticipation of the occurrence of aerodynamic instability. I have however worked on flow-induced vibrations of a tube bundle in cross flow, which to a good extent resembles the case of 3-wire conductor subjected to wind cross flow. In our study, we pointed out the onset of instability, and how to determine the conditions at which it occurs by solving the generalized nonlinear eigenvalue problem. You may wish to check our related publications that may be of benefit.  

Regards

For post processing, currently I am using tecplot 360

The Geometry has to provide the maximum contact area allowed between the water and the surface, so, small thickness of the water-stream in the perpendicular direction to the plate, and wide span of the plate's cross section, the perpendicular one to the stream velocity vector.

If the velocity of the stream is not high, and you have no problems with skin friction, I would suggest to introduce so small spike, or irregularities on the surface, where the stream flows, to create a more energetic boundary layer, that would advance the termal exchange between plate and stream.

The thermodynamic pressure (or total pressure) is a global quantity and does not depend on space variables, but only on time. This is noted just before eq. 4 in the paper. If the system is open, equilibrium conditions at the boundary dictate the value of the total pressure, which is however not  a priori constant. This is remarked just after eq. 7. If the fluid is assumed inviscid, the friction coefficient and the conduction coefficient are implicitly null, thus leading the right-hand side on eq. 6 to be zero. Under this condition, the time derivative of the thermodynamic pressure is zero.

thank you for your help

Please refer to the following paper:

P. Vedula and R. J. Adrian, “Optimal solenoidal interpolation of turbulent vector fields: Application to PTV and super-resolution PIV,” invited paper, Experiments in Fluids (Special issue), 39, pp. 213-221 (2005)

There are so many ferrofluids available. However, suspension stabilty did not depend on the type of ferrofluids its mostly depend on various parameter like size of particles and so many other factors.

Please can you explain details of application 

What is your application? If your fluid is liquid and the regime is turbulent you can sometimes use the inhomogeneities (and also air bubbles) and follow them

The above answers given are very good. But I will try to answer in a more bascic level. The momentum of the flat plate is zero and the momentum of the uniform flow has a finite value. When the incoming uniform flow flows over a flat plate, the fluid particles near the plate will stick to the plate (no-slip condition). That means that the momentum of the flat plate is diffused to the fluid. The reason for this no-slip condition is adhesion between the flat plate and the fluid particles. The fluid particles have a force between them that holds them together, which is cohesion. When the fluid flows this cohesive force along with adhesion shows itself in the macroscopic scale as viscosity. As the flow proceeds downstream of the flat plate the viscosity is able to slow down more and more fluid layers above the flat plate. This is what is called momentum transfer. And hence the boundary layer thickness increases as the fluid moves downstream.

Dear Dr

Some of my papers

1- A. R. Seadawy, Fractional solitary wave solutions of the

nonlinear higher-order extended KdV equation in a stratified

 shear flow: Part I, Comp. and Math. Appl. \textbf{70} (2015)

 345–352.

2- Khater, A. H., Callebaut D. K., Malfliet, W. and Seadawy A. R., Nonlinear Dispersive

Rayleigh-Taylor Instabilities in Magnetohydro-dynamic Flows,

Physica Scripta, 64 (2001) 533-547.

3- Khater, A. H., Callebaut D.

K. and Seadawy A. R., "Nonlinear Dispersive Kelvin-Helmholtz

Instabilities in Magnetohydrodynamic Flows" Physica Scripta, 67

(2003) 340-349.

4- A.R. Seadawy, Exact solutions of a two-dimensional

nonlinear Schrodinger equation, Appl. Math. Lett. 25 (2012) 687.

5- A.R. Seadawy, Stability analysis for Zakharov-Kuznetsov equation of weakly

nonlinear ion-acoustic waves in a plasma, Computers and

Mathematics with Applications 67 (2014) 172-180.

6- A.R. Seadawy, Stability analysis for two-dimensional ion-acoustic waves in

quantum plasmas, PHYSICS OF PLASMAS 21 (2014) 052107.

7- Helal, M. A. and  Seadawy A. R., Variational method for the

derivative nonlinear Schrodinger equation with computational

applications, Physica Scripta, 80, (2009) 350-360.

8- Helal, M. A. and  Seadawy A. R., Exact

soliton solutions of an D-dimensional nonlinear Schrodinger

equation with damping and diffusive terms, Z. Angew. Math. Phys.

(ZAMP) 62 (2011), 839-847.

9-  Khater, A. H., Callebaut D. K. and Seadawy A. R., General

soliton solutions of an n-dimensional Complex Ginzburg-Landau

equation, Physica Scripta, Vol. 62 (2000) 353-357.

10- Khater, A. H., Helal M. A. and Seadawy A. R.,

General soliton solutions of n-dimensional nonlinear Schrodinger

equation" IL Nuovo Cimento 115B, (2000) 1303-1312.

11-  Khater, A. H., Callebaut D. K., Helal, M. A. and  Seadawy A.

R., Variational Method for the Nonlinear Dynamics of an Elliptic

Magnetic Stagnation Line, The European Physical Journal  D, 39,

(2006) 237-245.

12-  Khater, A. H., Callebaut D. K.,

Helal, M. A. and  Seadawy A. R., General Soliton Solutions for

Nonlinear Dispersive Waves in Convective Type Instabilities,

Physica Scripta, 74, (2006) 384.

13- Seadawy A. R., Three-dimensional nonlinear modified Zakharov–Kuznetsov

equation of ion-acoustic waves in a magnetized plasma, Computers

and Mathematics with Applications 71 (2016) 201-212.

14- M.A. Helal and A.R. Seadawy, Benjamin-Feir-instability in

nonlinear dispersive waves, Computers and Mathematics with

Applications 64 (2012) 3557-3568.

15- Seadawy, A.R., and El-Rashidy, K., Traveling wave solutions for some coupled nonlinear

evolution equations by using the direct algebraic method, Math.

and Comp. model. \textbf{57} (2013) 1371.

16- A. R. Seadawy, New exact solutions for the KdV equation with higher  order nonlinearity

by using the variational method, Comp. and Math. Appl. 62 (2011)

3741-3755.

17- Seadawy A. R, Stability analysis solutions for nonlinear

three-dimensional modified Korteweg-de Vries-Zakharov-Kuznetsov

equation in a magnetized electron-positron plasma" Physica A:

Statistical Mechanics and its Applications  Physica A 455 (2016)

44-51.

18- A.R. Seadawy, Nonlinear wave solutions of the three-dimensional

Zakharov–Kuznetsov–Burgers equation in dusty plasma, Physica A

439 (2015) 124–131.

19- A.R. Seadawy, Stability analysis of traveling wave

solutions for generalized coupled nonlinear KdV equations, Appl.

Math. Inf. Sci. 10 (1) (2016) 209–214.

Thank you Prof.Hassan

It maybe

1. Solution is not correct when you use relative velocity

or 2. the non-dimensionalization is not consistent.

I think it is hard to say. If add leakages, it means more engry. It is a mix process between leakage flow and origin area with energy exchange.

I have found a partial answer to my own question its in the text book A. Bejan "Convection Heat Transfer" defines "Heat lines" to allow the visualisation of convection. All I have to do now is to extend his mathematical definition to include the unsteady work transfer process (dp/dt). Anyone know how to do that?

Martin

Better to read first the book :Gas Dynamics by Liepmann and Roshko. 

I am amazed so much as been done on the slug and plug flows. Surely, nice to learn that so much has been accomplished. Perhaps, there is another way of looking at the structures of the two-phase flows you are interested in. When I needed to know more about how such as a flow "moves", but knew only the approximate value of the ratio of void fractions to the fluid fractions volumes' and desperately wanted my device to work for a wide range of surface tension and liquid-solid adhesion values, I have resorted to a trick. It may be a shortcut that may help you out.

I have started at the inlet, took gas as "massles" and computed accelleration of liquid plugs under an action of the motive pressure, being common for gas and liquid masses reamaining in contact. SUrely I have included viscous friction of liquid plugs, taking this to corrrspond to liquid cylinder in laminar flow. When you have more than a dozen of such composite pairs (bubble and plug) you get a flow that is averaged out over a couple of impulses. Moreover, a bubble, say, number n, was bubble the n-1, at a previous impulse juncture. Having this averaged over several impulses, gave me the pipe exit pressure value. Not trusting these calulations too much, I have proceded with my design work and results were very, very  good. What is funny about that is that values of the pressure and the throughput corresponded very well with expierimental values for plug and and for slug flows,all the same, althouh for the slug flow gas slugs may overtake liquid blobs. Apparently, for the pressure distribution occasional situation when the liquid plug stretches accross the entire pipe span (cross section) have a lot more to do with the overall behavior of the (averaged) flow than the precise structure of the very flow. Mathrmatically speaking, such flows are chaotic, but the outlayers (cross spans, near-pugs ) may be the controlling factor, but we stilll keep on segregating the pheonomenon based on our failry superficial observations.    

I think you could find some advices in superhydrophobic surface. Paper:

PRL 114, 014501 (2015)

Experimental Thermal and Fluid Science 51 (2013) 239–243

Best wishes

Follow the British Standard. This what I did when I designed my wind tunnel in my MSc  research. 

Dear Ergin,

I invite you to check out Patrick Leblay's work (https://www.researchgate.net/profile/Patrick_Leblay), and especially the following article:

You can also download his PhD thesis (in French) with the following link:

There are many cavitation numbers depending on the purpose of research. If you want to define the incipient or end of cavitation, or cavitation threshold, or supercavitation, initial cavitation erosion or etc. and want to use data from previous studies, it is important to use the same cavitation number and to read the definition where the pressure difference and the speed is taken. In most cases you have to trust the selected cavitation number. Sometimes based on the experimental data (if published), it can make interesting conclusions or change cavitation number and propose new criteria.

If you're doing research perhaps for ultrasonic cavitator you should know the pressure distribution and choose correct place for measurements of the pressure difference and the velocity.

Thanks for the paper. I'll try to implement the equations. If I may, I wanted to ask you some other question, as an expert in the field : I need to Abel reconstruct the measured projections of the gas jet. However, due to noise amplification of the reconstruction algorithm I want to filter first the measured data. I wonder if  the frequency spectrum of the density profile function has some kind of a cut-off frequency, so that I can be assured that filtering the projection data with a wider filter won't result in any loss of information ? 

Salman Bin Kashif,

I did not understand your question fully. What do you mean by "extent of mixing between the two gases" ? Don't you think, mass fraction contour presents the extent of mixing of gases? 

Change in mass fraction is not caused by reactions. It is caused by diffusion occurring due to species concentration gradient. 

Palani.

Respected Contributors,

My intent to put forth this question was to check if I am updated enough about the theoretical developments in studying space-time discretizations. My question being naive, yet it was solely meant to see if there was an answer to the question. I guess, I have benefitted a lot from the answers here, and also refreshed some of the concepts that were taught to me during my Master's. I also agree now that the answer to my question is "NO", and would like to again say that, I was looking for a theoretical (pen and paper) solution, without having to do any simulation, and that the error scaling would depend upon numerical parameters and not time explicitly. Hence, I was not looking for an answer wherein, I have to do spatial/temporal evaluations via simulations, which I again state was a very naive question.

I would sincerely thank all the respected contributors above.

Regards

Shakti

DMEM = Dulbecco's Modified Eagle Medium ? first time i hear about it, it is out from  my field of expertise, I don't know if standard degasing methods used for physical research (boiling, vacuum , ultrasonic,) may destroy  your medium.

if your problem is the oxigen, then work with a different gas (Nitroge, elium..)

If you don't want any gas, you could connect your device to a vaccum pump and to the bottlle of your medium. all connections controlled by valves. First vacuum youir device, may be also yout bottle, then let your fluid flow from the bottel to the device. Take care your fluid do not flow into the vaccum pump (it could destroy it). 

Apart these general ideas, the details pof your necessity remain still quite unknown to me.

In addition to Prof. Qin's answer about the resolution requirements in the near wall region, the mesh refinement level is dictated by the resolution of the species mass fraction profiles in the reaction zone. I assume the reacting flow you are simulating is a propagating flame. If so, then the reaction zone within the flame front should be discretized with at least 10-15 grid points. On top of this, under the influence of high pressure the flame thickness becomes much lower, hence the spatial discretization step needs to be smaller.

A way to extract the length scale of the reaction zone is to solve the 1D profile of the reacting mixture using software like chemkin or cantera.

The Kolmogorov scales are: n/L ~ Re^(-3/4), where n/L is the ratio of the smallest to the largest length scale. 

 Hi Bernard,

Thanks for the reply.  What do you mean by additional O-grids? I mean should i go to create block and using entities create a block and merge it with the existing one? Iam actually a beginner in ICEM CFD. I actually included a block and tried meshing but it din't pan out well. 

Thanks

regards

Sankeerth

Starting from your mesh you can create a dfsu file in which you can specify the desired value of  roughness (z0) for each node, obviously different for seagrass and rock. In this way you can load a space-varying roughness as input. 

Could you please post the figure of the spectrum? Previous answers addressed problems in doing FFT but if you are solving high Re number flows, many characteristic frequencies can also appear..

If I understand your question correctly, a straightforward way to create an array of water drops with different sizes would be to pattern a surface with alternating circular hydrophobic/hydrophillic regions of different diameters (hydrophillic where you want the drops). SiO2 on a silicon wafer would work fine.Pooling water on the top and then slowly tilting to remove excess water would leave the drop pattern you need (on the hydrophillic regions).

Though the diameter of the drops would be a known quantity (based on the size of the patterned features), the volume for a given diameter would have to be characterized (though probably just once) or inferred from knowledge of the different surface energies.

Mostly  50 times the diameter gives good results in most applications where flow geometries change. Although different researchers take any value from 10 D to 100 D, depending how flow development length is defined.

There is an epoxy putty which you can mix and shape and then harden in an oven. That worked well for any fluid and gas tight connection, however a permanent solution.