Honestly, you taught me more than what I was able to learn in the last year at university. Thank you so much. Love your talks. I have watched em all atleast twice

@fluidmechanics101

4 жыл бұрын

Amazing! I am trying to make the talks like a resource that we can all jump back into when we need them. I sometimes forget things as well and have to look back at them 😅

I am enjoying these episodes much more than Game of Thrones

@fluidmechanics101

4 жыл бұрын

... especially Season 8

@MesbahSalekeen

4 жыл бұрын

LOL

@ozgunonen7427

2 ай бұрын

That is absolutely true :)

Excellent work Prof. Aidan I enjoy your pretty clear explanations. Amazing !

You do a very good job with your videos. They explain things in a very understandable way.

Excellent talk! Carry on mate! Hope to see a full lecture series on CFD!

What a beautiful talk! Amazing from start to end!

Thank you so much for your well-organized slides and clear teaching! Your teaching style is to ask HOW before conveying a new idea, which makes me follow the main idea better.

Clear explanations, easy to understand, excellent work as always. Thank you Aidan! I would really appreciate if you do some videos on the programming theory or programming skills related to OpenFOAM.

awesome explanation for the modified pressure. I was confused about this and I always though we are applying static pressure. But, when I checked fluent guide and openfoam, there they mentioned regarding the modified pressure which I failed to understand. But, this video cleared out my doubts.

Your way of explaining things is superb

People are lucky that these videos are free.

Amazing!!! Thank you so much for this wonderful explanation. May your tribe increase!! I have liked and subscribed 👍

Thank you so much for this. Really good for understanding the basic concepts.

Hi! here you have an hispanic follower, you teach really amazing even in another language i get everything, thank you so much!

Great explanation about modified pressure bc. For the OpenFOAM users this is the p_rgh, which generates thousands of doubts at the CFD Online Forum The screen you appear on sometimes cover part of text on the slide.

@fluidmechanics101

4 жыл бұрын

Yes! p_rgh is the modified pressure in OpenFOAM 😄

@nickjohnsonn9761

3 жыл бұрын

@@fluidmechanics101 Hope you may include OpenFOAM based samples also. Haha. But it really helps us, to navigate more in the foam directories.

excellent ,really appreciate your valuable knowledge and helping us improve rapidly. thanks a lot.

Enjoying your videos. Great Work!! 👏👏💕

Sir, thanking you so much because your videos are really outstanding and it's really valuable. We always need a person like you who teaches us at its best. Once again thank you sir

Thank you so much for making these videos, it helped me a lot!

You actually are amazing teacher, thanks a lot !!!!

Thanks so much, Aidan. Very helpful.

I am eternally gratefull for your guidance

Excellent talk! Thank you for nice explanations.

Brilliant as usual

This has been super helpful. Thank you!!

This series just solved some of my OpenFOAM problems! Wutt! A talking forum.

Great work, very interesting talk

Thank you found this video very useful for my project.

Thanks for inspring videos, please keep going

Your explanation is very clear. I taught many things. Allah bless you. Thank you!!

Just Stumbled upon your videos while learning Fluent. Great Work. Could you please do a video on other common boundary conditions? Thank You!

At 17:39 M should be M>0.3 (1>M>0.3) as flow to Subsonic Compressible flow. Rest all of your videos are amazing. When I get doubts about working on CFD, I look into your videos!

I wanna take a moment and appreciate your work and the effort you put into creating these. Even if there is only a niche of viewers, in my case, your content has really helped me understand the concepts well. Keep doing more content of FM like the awesome ones that you have done!

Thank you for a video from Belarus!

This is the only KZread channel that I subscribed and clicked the bell icon. You're a great teacher. Love your content. I would really appreciate if you would do videos about following topics: 1- General talk about 'Large Eddy Simulations' 2- Smagorinsky-Lilly turbulence model 3- Vortex visualisation 4- Unsteady RANS I am an university student. My final project is about the efficiency of a wind turbine with leading-edge slat. I am trying to eliminate the tip losses.

@fluidmechanics101

4 жыл бұрын

These are some great suggestions, thanks Ekin. I am planning on doing the LES type models soon, starting with a general introduction on scale resolving simulations. I still have a bit of research left to do on the subject though before i can make these ones! As you are looking at tip vortices and tip losses for wind turbines, you might find my thesis useful for your studies (Tip Flow Corrections for Horizontal Axis Wind and Tidal Turbine Rotors). Best of luck with your studies!

Amazing video as always! If you ever get around to making more videos on compressible flow CFD, a video on non-reflecting BCs would be great!

@fluidmechanics101

Жыл бұрын

Great suggestion! I will add it to my list

a wonderful video, thanks you so much

you are a blessing man, thank you very much.

Thank you for the lecture

Really great talk !

Amazing job mate

It was very useful, thank you so much

Thank you very much! it helps me a lot!

Спасибо за видео !

Excellent.. thanks

Wonderful explanation!!! It helps so many people. Hope you will provide more knowledge to many more. You have mentioned Subsonic compressible flow as (M

@fluidmechanics101

Жыл бұрын

Yep well spotted

@dekkalavinay9625

Жыл бұрын

Please continue to spread the knowledge !!

Clear and awesome explanation! I have a question to ask. For segregated flow solver, what is the difference between correcting the velocity on pressure boundary after solving the pressure correction equation and the method in this video? Are both equivalent? Thanks.

Crystal clear

Great sir

very interesting

Kindly make a video on aeroacoustics as well if possible using fluent. How we are going to set up the case and validate the case

Really helpful video as always! I have a question that is somewhat related to this topic. Why is it more appropriate to apply stagnation pressure to fluid entering the domain (either through an inlet or backflow through an outlet) but to apply static pressure to fluid leaving a domain (either through an outlet or backflow through at an inlet)? I am trying to understand why recirculating flow is treated differently at an inlet or outlet boundary compared to the rest of the flow. A get the impression that the reasoning goes beyond numerical stability.

Hi, I really appreciate everything you post in your channel. You videos are very informative and I've learned a lot from them. I would like to ask Could you please let me know how can I find the inlet boundary conditions and the exit boundary conditions , if I have only those inlet parameters incidence angle, Mach number and Reynolds number. Thank you.

@fluidmechanics101

2 жыл бұрын

Try working them out by hand. If you know your Reynolds number, Mach number and temperature (presumably at an altitude) then you should be able to work out the velocity, density, static pressure, total pressure, total temperature using a combination of the ideal gas law and isentropic relationships

Thank you for your videos! They made some topics more clear to me :) Is it possible to share the LaTeX preamble of the "calculators.pdf" on your web page (tools.html at the bottom)?

Thank you for the video! is there any chance that you can make a video about setting backflow condition at the outlet? I tried to find one for OpenFoAM but I cant understand which boundary conditions to use for p, p_rgh, u, T, alphat, k, epsilon, nut. I can't be sure which BC to use as I don't understand the theory behind it. Great work anyway!

hope there is a video about transient analysis and courant no as it is very important topic

@fluidmechanics101

4 жыл бұрын

Yep, the Courant number video should be out in the next few weeks 😄 i am just finishing it off

Great Work man!

I learn lot from your viedeos and also motivates me to do things in different ways in CFD. I am doing aeroacoustic analysis using LES. I used the RANS data from a plane to prove inlet boundary condition to LES inlet which comprises the variables as Pressure, Mach no, and Temperature. I am curious to know what should be the outlet boundary condition (i just gave as 0 pa at outlet) . Should the pressure at outlet may be zero as I had with velocity inlet boundary condition or may not be zero in the mean. Should I estimate a mean pressure value at outlet from RANS and set it as Pressure Outlet pressure in the simulation. The outlet boundary is sufficiently far away from area of interest.

Good Evening, In the same thing i am using a udf, for sinusoidal input but it is not working correctly. Could you help me please. Ur vedios have much more knowledge than the textbooks of cfd i have read till now. Thank you !

Respected sir Please make video on large eddy simulation your all videos are great and helped me lot in my project you are great

@fluidmechanics101

4 жыл бұрын

I am writing the LES video in the next few weeks! It should be a good one 😄

i have done some work on s duct diverging nozzle there i am facing some type of diverging problem it doesn't converse.

Hi ! I really like those videos, really good explanations. Sometimes I wonder why fluent documentation is not made like that. I have a question concerning pressure inlet BC : in "thermal" I can specify a "total temperature". If I understand Fluent vocabulary well, it means that I can specify a stagnation temperature. I do not really understand what is the point of specifying one and how it can change the velocity calculation since only static temperature is involved in velocity calculation ( in equation 13). So I wonder : Does that total temperature have any role in changing the velocity being calculated after specifying Po and P ? Thanks !

Could you please explain non reflective boundary condition at outlet?

Sir, can you upload a video on exhaust fan and fan boundary condition

Hello. I have studied fluid mechanics most of my career but it is been since months now that I am approaching problems with numerical methods. I mean I know the whereabouts of most the common methods (FEM, FVM, FDM, Spectral Methods) but I have been mainly a user of packages such as FLUENT or COMSOL. I would like to ask you, what is your take on Lattice Boltzmann Method for solving incompressible flows. I have read encouraging and discouraging opinions about its use. What would be your take regarding LBM for solving N-S? Thank you very much for your answer. Cheers.

Thanks for the video! I have a question. What if I am trying to simulate a transonic flow past a wing at an angle of attack. Sure I can specify the Gauge total pressure at the inlet and a static pressure at the outlet since it is a subsonic case. But then the calculation of the velocity from the total pressure gives a velocity that is the magnitude and not the individual components. I have set a pressure far field boundary condition with the components of the velocity though. So will this ensure that the velocity components at the leading edge of my wing correspond to the desired angle of attack by using information from the far field or will it not?

@10:13, u mentioned P-o as static pressure (in subtitles its showing) U r saying for static pressure it will take value from previous iteration, but what happens for the first iteration ? Is it same as taking values we initialized the whole domain ...?? for hydrostatic pressure case, as u mentioned CFD automatically accounts for hydrostatic pressure variation (rho*g*z) as it takes modified pressure p' for calculation. but if u see the expression p'=p-(rho*g*z), we are actually subtracting this (rho*g*z) value from static pressure. doesn't it mean we are neglecting the hydrostatic pressure variation ....?? correct me if my understanding is wrong. As usual ur interesting videos are great help for CFD beginners like me. Thank you

I am a bit confused about prescribing stagnant pressure p0 (incompressible flow). Lets say I have a pipe and I measured the pressure with a barometer upstream and downstream (lets say 3 atm and 2 atm respectively). Now I wanna apply those conditions and solve for the flow. How can I apply the stagnant pressure upstream if I do not know the velocity? In a steady case I could rerun my model many times with different p0 until p upstream matches 3 atm (pain in the butt to run many though, takes forever). And even worst in an unsteady case in which I have a time-varying p measured upstream and downstream, what do I do?

can we take the instantaneous velocity calculated by CFD as a transient case , so that i can calculate the transient flow rate? Thanks

Your CFD lectures are very useful, especially for the learners. My question about the inlet pressure condition is that how do you specify the value of the stagnation pressure at the inlet which also is unknown if you do not know the inlet velocity?

@fluidmechanics101

3 жыл бұрын

You will have to do a quick hand calculation. If you take the velocity (that you know), calculate Mach number, then use the stagnation pressure equation to calculate the stagnation pressure from the static pressure (the static pressure will probably be atmospheric) 👍 this is also a useful way to check your CFD before you start running the case

@ziadalaswad4462

2 жыл бұрын

Yes, but the velocity in unknown. Does that mean that we take an initial guess for the velocity?

@fluidmechanics101

2 жыл бұрын

You have to know something about your inlet condition ☺️ what information do you have? Mach number, static pressure, stagnation pressure, altitude, velocity, temperature, total temperature, mass flow rate?

@ziadalaswad4462

2 жыл бұрын

@@fluidmechanics101 Got the idea!! Thank you very much for these videos!! I am new to the channel and I am enjoying every single episode. Keep it up! I would love to see more applications though 😊

Could you please elaborate how the outlet pressure p propagates upstream, from what I understand -- the atmosphreric pressure (static pressure=0) applied at the outlet would propogate back as ripple? Further, is this also the pressure which is used in case of calculating velocity at the inlet when we give stagnation pressure as inlet condition?

This presentation is very helpful thank you. I have a question about BC for a forced convection study of a self ventilated electric motor cooling. Is it possible to only use "pressure-outlet" BC for the 6 faces of the enclosure surrounding my motor or do I have to set at least 1 face of the enclosure with a "pressure-inlet" BC ? In both case I want to fix the temperature at theses boundaries, will the result be the same ? Thank you

@fluidmechanics101

Жыл бұрын

These simulations are always tricky to get the right boundary conditions. My recommendation would be to make a very coarse mesh and try out some different boundary conditions (so you can do this quickly). Once you have it working and you are happy, then run the same boundary conditions on your fine mesh

Exactly what mathematical process shows the influence that the outlet static pressure has over the inlet static pressure when the flow is subsonic? I can't find anything online for it.

Can you add video on presto scheme

Thank you so much! Excellent explanation! I have a question about pressure inlet BC. In the scenario of bouyancy-driven flow showed in your video, the modified pressure is not constant across the inlet, because the streamlines will contract when it is drawn into the room from the ambient. In addition, there will also be pressure loss at the inlet due to that contraction. So i was wondering if there is any way of applying more accurate boundary condition at the inlet.

@fluidmechanics101

4 жыл бұрын

Have you tried extending the geometry further upstream, so that the contraction is included as part of the CFD geometry? Often people will add large boxes around the inlet of a geometry so that you can capture the inlet losses more accurately.

@junegon528

4 жыл бұрын

@@fluidmechanics101 Thanks for your suggestion! I will try it.

Thank you for this great video! I have a question. At 9:10, let us say we use static pressure at the inlet but we still need the velocity to be specified as the boundary condition at the inlet. So, how velocity is calculated at the inlet for this case. You have very well explained that this case will diverge but to solve the equation and to get a diverged solution, we need to specify the velocity boundary condition at the inlet. Can you please explain? Just curious to know!

@fluidmechanics101

3 жыл бұрын

In this case, the velocity will initially take the value of your initial condition (the initialisation in Fluent or 0/U in OpenFOAM). The velocity is then updated from the solution of the momentum equations. Moving next to the pressure equation (see my video on PISO or simple algorithm) the pressure equation will struggle to reach a solution as it can't find a pressure field that is consistent with the velocity field you prescribed. Bit confusing but hopefully that helps!

@prakashthirunavukkarasu29

3 жыл бұрын

@@fluidmechanics101 Thank you for the reply and yes, that helps! Thank you once again for your great effort!!

Great lecture! One question, so you said in the subsonic case we specify the stagnation pressure and the static pressure at the initial condition. Do you mean a static pressure for the entire domain as a "guess"? I'm a bit confused since if we specify the static pressure and the stagnation pressure at the inlet then velocity would be by definition fixed there, so it cannot be updated as the code progresses.

@fluidmechanics101

4 жыл бұрын

Ahh yes. We specify both the stagnation pressure and static pressure at the inlet as an initial guess (to get the first velocity guess to apply at the inlet). Then we solve momentum and pressure equations using SIMPLE or PISO. Now we have a new static pressure field. The stagnation pressure remains fixed for the whole simulation. We use the new static pressure field to get the new velocity and so on. The initial guess for the entire domain is what you do when you initialise the solution in Fluent (or the 0 folder in OpenFoam)

@nikan4now

4 жыл бұрын

@@fluidmechanics101 That makes sense. Thanks a lot. Looking forward to your future videos :)

Hello, I want to simulate Stirling engine so could you help me how to set boundery conditions?

Thank you again for your high quality video. I have a question about one of your slide. when you said that "The computed Velocity field (U) has to balance the pressure gradient exactly" and that "any numerical errors will lead to divergence", I am not sure to clearly understand this mechanism of divergence and how it happens. Could you provide some details about it or at least refered me to some litterature references that could clarify this point? Thanks !

@fluidmechanics101

3 жыл бұрын

Sadly I don't have any references for this. The way to think about it is with a flow in a box with one inlet and one outlet with equal area. Taking a control volume around the box, the static pressure gradient has to balance the sum of the forces on the box. As we are specifying the static pressure at the inlet and the outlet, we are specifying the static pressure gradient. This has to balance the sum of the forces on the box (skin friction and pressure drag). But we don't know the sum of these forces yet, and so our guess for the static pressure gradient is likely to be wrong! If it is wrong then the code will never be able to converge to a solution. I realise this is complicated but I think a bit of control volume analysis might help you out 😃

@jeremiebisson9024

3 жыл бұрын

@@fluidmechanics101 Thank you for your feedback !

Thank you for the video. When I tried pressure-driven flow, for which I imposed pressures (static pressure + dynamic pressure) at the inlet and oulet, the solution became divergent. To solve this problem, should I impose velocity condition? When I impose zero velocity at inlet, flow became convergent. Or should I impose only static pressure at outlet, not stagnation pressure (static pressure + dynamic pressure)? A result I want is that flow which is purely driven by pressure, not velocity.

@fluidmechanics101

3 жыл бұрын

Your divergence could be from a number of different things (mesh, timestep, boundary conditions, source terms etc). Have you done all your checking and you are sure it is due to the boundary condition? It is a good idea to check that you can get a stable solution with the simpler case (velocity inlet and pressure outlet) and then switch to pressure inlet and pressure outlet if that converges

8:24: Why we can't specify the static pressure at inlet and outlet

@fluidmechanics101

3 жыл бұрын

This is a subtle point. Assuming that you have an inlet and outlet with equal area, the static pressure difference has to balance the total force applied to the domain exactly! You would have to ensure that your calculated pressure difference is 100% correct. In general this is not possible to do and the CFD solver will diverge if you try and run the simulation as it can't balance the total force with the pressure difference you have applied.

The Navier-Stokes equation uses the total pressure term, but in OpenFOAM boundary conditions, we specify the static pressure. Can you correct my misconception about this?

Sir can u give me the graph between coefficient of pressure and length? Pls

Is it possible to apply a shear flow velocity profile at the inlet right away in ANSYS Fluent?

@fluidmechanics101

3 жыл бұрын

Yes, you will need to load a profile for each of your inlet variables and then apply the profiles at your inlet boundary condition. Maybe have a look for a tutorial which shows parabolic flow at the inlet? You can then work out how to do a shear profile from this

thanks a lot for the video. I am simulating flow through a box with fans inside. I will be using dynamic meshes to rotate the fans and the objective is to see how much flow rate the fans can generate at the outlet. Do you think pressure inlet in this case is an apt boundary condition? thanks again

@fluidmechanics101

Жыл бұрын

Yes, pressure inlet and pressure outlet seems fine to me. You can always try with a coarse mesh first to check your boundary conditions and then switch to a fine mesh once you are happy

@bhootmehra

Жыл бұрын

@@fluidmechanics101 thank a lot :)

one question: as you shown in picture of house with chimney, we dont know the inlet velocity. so how do we calculate stagnant pressure to give as input (we get stagnant pressure by adding static and velocity head). as I am understanding, we have inlet and out static pressure i.e. 0 Pa as the domain is open to atmosphere.

@fluidmechanics101

7 ай бұрын

Both are 0Pa

while applying stagnation BC in the inlet, how do i know the exact value of it, do we need to assume some sort of a velocity at the inlet, but that assumption will not be accurate, and my BC is therefore not accurate.

@fluidmechanics101

2 жыл бұрын

Yep, if you are doing aerodynamics you can calculate it from the Mach number. For general systems the stagnation pressure is equal to the static pressure far away from the inlet where the flow is stationary (reservoir pressure)

For the inlet velocity BC: what commercial codes implicitly do for pressure at the upstream boundary and velocity at the downstream one? Is it gonna be a Neumann boundary condition for both?

@fluidmechanics101

3 жыл бұрын

Yep 👍 unless the upstream is supersonic. Then the commerical code does dirichlet for pressure

Sir how is consideration for open foam rhogh bc in buoyant pimple foam and buoyant simple foam

@fluidmechanics101

4 жыл бұрын

OpenFOAM uses the gauge pressure in the same way as fluent. The variable is titled p_rgh as this is the static pressure without the hydrostatic pressure 👍 it makes it easier to specify boundary conditions for pressure

How can we implement this in OpenFoam?

Thanks a lot for this series, like even my professors never explained us this way. But as a novice, I don't understand how does the CFD compute static pressure in each iteration for pressure inlet (subsonic compressible flow). Because what I need is I have to simulate flow over a body starting from Mach 0.3 to 5 so I used Pressure inlet so that in one simulation I can capture the compressible subsonic n supersonic part, but what I observed is in (facet average of velocity magnitude)velocity vs flow time , the velocity was lesser than I expected. I mean I have data for velocity from Mach 0.3 to 5 but as velocity inlets are used only fr subsonic so I had to find manually find stagnation pressure and static pressure at each mach number and used a transient table for this whole data. Basically the velocity that cfd computes was less than wht i need and it is mostly because of the static pressure that it is calculating at each point right? Can you just explain how the CFD computes the static pressure at every iteration?

@fluidmechanics101

3 жыл бұрын

This will depend on the type of solver you are using (density based or pressure based). However, it is usually easier to think about it this way: You specify the static pressure at the outlet. The static pressure at the inlet = static pressure at the outlet + pressure loss in the domain. You cant calculate the pressure loss in the domain by hand (you need the CFD code to do this) so the static pressure at the inlet will always float. Your best bet is to try a range of slightly different total pressures and select the one that gives you the target Mach number you are after 👍

@vaijayantimallick4928

3 жыл бұрын

@@fluidmechanics101 Thanks a lot for the reply. I am using density based solver, so is there any other factor because of which I am getting a different velocity than expected?

For CD nozzle, at the inlet the flow is subsonic and the outlet flow is supersonic, so it's the second case for the pressure inlets?

@fluidmechanics101

3 жыл бұрын

Yes, it's all about whether the pressure 'information' is able to propagate back upstream 👍

Your video are really very helpful. I have one question related to the boundary conditions only, can we use total pressure inlet and mass flow outlet type boundary conditions in case of unknown outlet static pressure? Also one request if possible then please can you make a one video on the micro gas turbine engine combustion chamber combustion analysis using Fluent or CFX. Just what kind of inlet and outlet boundary conditions we can apply and flamlet set-up.

@fluidmechanics101

2 жыл бұрын

You could try the mass flow outlet and total pressure inlet. I suspect it will probably be ok, as the static pressure difference between the inlet and outlet can still develop across the domain. Sadly I don't have much experience with combustion models, so I can't offer anything yet but I am looking into it!

@shivkushwa6149

2 жыл бұрын

@Fluid Mechanics 101 Thank you sir for your response. As you said the static pressure difference between the inlet and outlet can still develop across the domain but I'm getting constant pressure across the domain ( static equal to static). I have set the inlet total pressure which is comming from the compressor and the mass flow outlet as totat mass flow of air and fuel. To check the pressure loss inside the combustion chamber. But from the result, I have not found any difference in pressure. So, I confused where exactly I'm making mistakes wheather boundary conditions setup or something mistake in my geometry. Now, with your response I'm bit confidence about my boundary conditions setup So, I will check combustion chamber geometry.

@fluidmechanics101

2 жыл бұрын

It would also be worth a bit of detailed post processing. Like have a look at the forces on walls, heat losses, mass flow rates and see if you can work out what is going on. I am sure you will probably find a small mistake

hi sir, I currently doing my own code by interest. Could u plz see if my implementation of pressure inlet is right? My question is what happen if the total pressure is small than the static pressure at the inlet boundary cell. for(face in the boundary) { if(total pressure >= pressure[boundary cell]) // flow enters the domain { velocityMagitudeAtFace = sqrt(2*abs(totalPressure- pressure in the boundary cell])); velocityAtFace = -faceNormal * velocityMagitudeAtFace; // my faceNorm of boundary face is point out of the domain velocity[ghost cell] = 2*velocityAtFace - velocity[boundary cell]; // dirichlet boundary condition for velocity pressure[ghost cell]=pressure[boundary cell]; // zero gradient for pressure } else if (total pressure { } } Thank u for your timing. BTW, u video is always my best choice for learning CFD best wishes, jialiang.zhou

Please answer this=some difficulties arise for setting boundary conditions in super sonic flow

@fluidmechanics101

Жыл бұрын

Sure, what is your question?

For supersonic compressible flow, doesn't specifying the static and stagnation pressure on the inlet equate to specifying the flow velocity? If so, why not just specify the flow velocity?

@fluidmechanics101

Жыл бұрын

Often with compressible flow, engineers are more interested in Mach number than velocity (i.e flight Mach number). Static pressure comes from altitude, and we get stagnation pressure from an isentropic flow equation. So it is just convenience really

hi, thank you for all the hard work! i have a question if you could help me figure it out.....that would be awesome! the problem i have is that if there is a room and on one of the room wall we have exhaust fans. now i want to study the ventilation of the room. one way is to actualy model the fan and then use sliding mesh method to make the air flow out of the room but that is very hard and time consuming instead what i want to do is that create outlet face on the domain wall and use some suitable boundary condition to mimic the behavior of an exhaust fan (ie move air from inside to outside) now, i want to figure out what boundary conditions should i use.... thank you!

@fluidmechanics101

3 жыл бұрын

Just use a 'velocity inlet' but specify the velocity components (U, V and W) as pointing out of the domain. This will act as a velocity outlet and pull the flow out of the domain, mimicing the effect of the ventilation fan. For your other boundaries, use pressure inlets. 👍

@muhammadtayyab6280

2 жыл бұрын

@@fluidmechanics101 Thank you very much! so, my model would be like this, use velocity inlet with outward vector direction to mimic exhaust fans and i have a door that is used for air inlet....just an opening (un restricted, un forced and open flow) should i use pressure inlet for this? Thank you for your help!

@fluidmechanics101

2 жыл бұрын

Yep perfect. You can have the open doors as a pressure inlet or opening 👍 pressure inlet should work fine but if it is being difficult to converge (if you get a lot of reversed flow) you can always switch to an opening

Thank you so much for all your great content. I found your video while looking into pressure inlets as I'm working on a case that I would like to have your opinion on if you may. I'm working on a centrifugal fan (blower) case where I'm trying to calculate the mass flowrate at its outlet coming out of the volute; we do not know any velocity, the only given we have is the rpm of the impeller. The blower is in an ambient room. I would like the steady-state case to simulate the suction effect of the rpm and to find the flowrate at the outlet. However, I do not have a value for total or stagnation pressure at the inlet; would it be physically correct in the model to add it as zero gauge pressure? since that the blower is in an ambient room. And would it be okay for the model to have both inlets and outlets as zero gauge pressure; one that is total at the inlet and static at the outlet.

@fluidmechanics101

Жыл бұрын

Yep zero gauge for total pressure at the inlet and zero gauge static pressure at the outlet should be fine. The mass of rate will then be the output of the CFD simulation for the particular rpm that you choose. An easy way to check these types of confusing boundary conditions is to make a really coarse mesh first (say 5000 cells) which runs really quickly. That way you can check what the pressure and mass flow rates are doing. When you have the boundary conditions you want, just rerun the case with your full mesh

@mostafaseif4409

Жыл бұрын

@@fluidmechanics101 Thank you so much for replying I much appreciate it! I will definitely use that trick as well, thank you.

@himanshushrivastava7062

7 ай бұрын

@@fluidmechanics101 Hello Sir, one question from side: if we are giving 0 gauge total pressure, isnt we are giving static head + velocity head as 0 instead of static head as 0 (as the domain is in atmosphere). i am trying to find this answer but no luck till now

@himanshushrivastava7062

7 ай бұрын

@@mostafaseif4409 Hi, I am doing the same thing as you. did it solve your problem?

@mostafaseif4409

7 ай бұрын

@@himanshushrivastava7062 Yes it did solve my problem. And to answer the question you're asking above: Yes, this would mean that you are making the static + velocity = zero. But these boundary conditions are not constant ones; the RPM of the rotating part would then change this boundary condition anyways as the case starts to converge the velocity component in the total pressure would also change.

sir, on what ground you have selected inlet static pressure is 4500 out of 5000 total pressure,.....is it follow the isentropic relation??

@fluidmechanics101

Жыл бұрын

Yes 👍

It was extremely helpful. As shown in the video it's easy to do this in ANSYS Fluent, just set pressure-inlet and pressure-outlet for inlet and outlet . I have a question about how to implement these boundary conditions for incompressible flow in OpenFOAM, I know for p i can set inlet with totalPressure and outlet with fixedValue, but how to set the boundary conditions of U, are pressureInletVelocity or pressureInletOutletVelocity for inlet and zeroGradient or inletOutlet for outlet correct ? and I'm also confused about the 'value' key word in 'pressureInletVelocity' and 'pressureInletOutletVelocity' boundary condition in OpenFOAM, does this mean the CFD code initial guess value for U of the inlet?

@fluidmechanics101

3 жыл бұрын

Yes you are correct. OpenFOAM lets you input two values, one is the boundary value and the other is the initial condition for that boundary. I think pressureInletVelocity or pressureInletOutletVelocity would work (although I am a bit rusty with OpemFOAM) so you should probably check the documentation. An easy way to check if your boundary conditions are working is to make a really simple case (a few hundreds cells in the mesh) and check the boundary conditions one by one. Then use the working boundary conditions on your real case

@hli3587

3 жыл бұрын

​@@fluidmechanics101 Thanks！I'm a beginner of CFD，your courses on Udemy are excellent which give me a lot of help. Hopefully you'll have videos on periodic boundary condition in the future，there seems to be another 'modified pressure' too.