Hello.

 I am simulating a supersonic flow inside a converging-diverging nozzle with non-equilibrium condensation model. For validation purposes, I am trying to validate the model comparing the results with experimental data from Moses and Stein (1978) and numerical data Yang et al. (2017). The CD nozzle was built using a 2D simplification.

 I am using the following models: Coupled Energy; Coupled Flow; DMP; RANS k-e; Steady Solution; Multiphase Interaction. For simulating water vapor, I selected IAPWS-IF97.

 In DMP phases, I have created a discrete phase following the configurations: Liquid, Constant Density, Two-way Coupling, Flow Model, Segregated Fluid Temperature and Discrete Quadrature S-Gamma.

 In Multiphase Interaction, I have selected the following models: Drag Force (Schiller Naumann), Interaction Length Scale, Multiphase Material and Non-Equilibrium Condensation.

 At inlet and outlet, the volume fraction of the discrete phase is zero. That is because I am trying to simulate an homogeneous condensation, where the particles are formed inside the nozzle when the properly conditions are achieved.

 At first, the simulation was not converging at all. After a while, I changed the Sauter Mean Diameter in Initial Conditions inside DMP model to a smaller value, and the simulation converged. Also, in Interaction Length Scale I choose the Sauter Mean Diameter. Although I got convergence, the results are not what I expected to be. The nucleation rates are higher than expected and it happens later inside the nozzle. Comparing the results with the paper from Yang et al. (2017):

https://preview.redd.it/n80oz5kfpo4e1.png?width=1806&format=png&auto=webp&s=c2adda8459b8129a5e32e80c12eb0469830887aa

 By studying different materials and reading both physics simulations and theory manuals of Simcenter Star-CCM+, I undestood that the particles are formed when specific conditions of the flow are achieved. When the flow reaches these conditions, the critical radius r* is achieved and the growth process begins.

 So, if the particle radius is given by this r* (which is calculated by using flow properties) and after that by the growth model, why do I have to choose a Sauter Mean Diameter? What is the order of the value I should use there? And why it has so much impact in the simulation?

Hi!

I want to simulate blood and contrast agent through a simple straight vessel. In Fluent setup I have created both blood and contrast as separate materials and the created a blood_contrast mixture which includes both of these species. However, when I look at the inlet boundary conditions blood is the only species present even though the mixture has been selected as the material. I have attached a couple images which may support my explanation.

I would really appreciate any help on what I may be doing wrong :) Thank you in advance!!!!

https://preview.redd.it/xjgrcmpzvn4e1.png?width=796&format=png&auto=webp&s=82e6256de9f263290c8d56bee121b4abb059217c

https://preview.redd.it/viuvslqzvn4e1.png?width=741&format=png&auto=webp&s=61302a492482b7547fd11d72c0141f6fd6b1ec14

As part of a heat transfer course at my university, we were tasked with designing heat sinks. I chose to go slightly more advanced and try to optimize the heat sink to be as light as possible. I wanted to validate my analytical calculations and implementation into my code by doing CFD. When I did so it was a lot colder than I expected. I then decided to do a simple flat plate to check the simulation was accurate and it was also about 20C cooler than anticipated (the analytical solution from the textbook and professor both said it should be 70C but CFD converged to ~50C).

I did this using LES for my turbulence model, with most of the model parameters in second order (particularly energy terms), and had an energy and heat balance requirement for convergence of 0.1%. I used the full buoyancy model (as opposed to the Boussinesq approximation) as the flow was entirely due to natural convection. The heat sink was very small 40x40x20mm if that matters. I used Siemens Simcenter 3D Thermal-Fluid Simulations Software. Does anyone have any suggestions about why the CFD was so much cooler than the analytical estimation?

As part of a design challenge, we designed a prosthetic arm for pro cyclists. One aspect not tested heavily is if using aerodynamic devices on the arm shell could provide any benefits. This exercise has taught me 3 things:

- An airfoil arm does give sizable benefit to drag coefficient along the arm as it reduces vortex shedding by forcing the flow to stay attached as much as possible

- The body and head of the cyclist will produce most drag anyway

- 15 million cell mesh on only a 16GB RAM laptop is a bad idea 😂😂😂

Tried to include some colorful CFD images as well:

BASELINE

Geometry and Isosurface (colored in velocity) for baseline case

Airfoil Arm

Geometry and Isosurface (colored in velocity) Airfoil Arm

I want to simulate an operation where 2 gases are separated on passing through a filter due to porosity difference. How do i simulate that

https://preview.redd.it/ynpfcj15bj4e1.png?width=1169&format=png&auto=webp&s=2749fd800a67a5767a726a1df8cb2b3305dff574

Hi everyone,

I am currently using ANSYS Fluent to conduct simulations on a particular problem. The fluid flow through a tube (20 mm in diameter and 100 mm in length) with a obstacle in it, and the small cavities on the bottom are pressure tapping points. The highest point of the obstacle ranges from 0.5 mm - 19.5 mm with 0.5 mm intervals. I plotted the pressure I obtained from pressure point A and B on separate graphs, and found that the results follow good pattern except for when the obstacle size is 10 mm. I tried different methods and ruled out the possibility of this being a physics problem. I think it has something to do with the software and the fact that the obstacle is exactly half of the tube. Do you guys know what could potentially be causing this?

I'm trying to optimize flow through a rocket nozzle, and I want to analyze how different converging and diverging angles affect the thrust generated.
Is there a way to run this quickly in ANSYS? Or do I have to change the angle in the sketch, mesh it and then run the solution again and again.
Any tips would be appreaciated, thank you :)

Hi, I've conducted a study of the affects of angle of attack on the coefficients of an aerofoil to compare against experimental data, both lift and drag appear more or less as would be expected, however, my moment coefficient is the 'mirror' of what I would expect based on my experimental data I am comparing to, i.e. there is a slow decrease in pitching moment in my CFD, meanwhile my experimental data suggests there should be a progressive increase in Cm. I was hoping someone could help me to understand why this may be the case and whether I am missing something obvious.

Many thanks for any help

experimental data I am comparing to

Quick and dirty graph of my CFD

Hello all. I have been quite an active member of this sub for quite some time, and have held discussions with people on multiphase flows, compressible flows and meshes in general. This is application time for the US and the UK, and I have been in a state of self-doubt for quite some time now. Please help me and give me a reality check.

My research work and interests:

1.) Multiphase compressible flows:

During my Masters' thesis, I worked on developing solvers for single phase and multiphase compressible flow problems. From reading books and papers, I have coded quite a few solvers ground up. Examples include convergence based analytical Riemann solver, Rusanov, HLL and HLLC schemes, and higher order variants using MUSCL Hancock Method with a choice of slope limiters, which is simultaneously second order space and time accurate.

In multiphase, I have used variants of the same schemes in a VOF setup. Volume fraction was chosen because mass fraction, to my understanding, forces an instant mixing and equilibrium between the fluids within the control volumes and if the fluids are very disparate in properties, it can lead to large oscillations in adjacent cells within a few time steps. Volume fraction allows different fluids to attain different temperatures, phase velocities and pressures within the same control volume. For closure, Stiffened Equation of State was used for all fluids.

We have further experimented with DEM (Discrete Equations Method) for the interface velocity to be calculated from the formulation of a contact discontinuity speed, but with the properties of two pure fluids on either side of the interface. This has led to 50% drop in L2 norm in density, and using MHM, another 33% drop in the error.

I have not seen seven equations model (which I worked with) being used in most practical problems or solvers, plus HLL has been preferred in most of these studies. DEM is again such a powerful tool, which albeit with a bit more computational costs, leads to a massive increase in accuracy. So I would love to explore this avenue, and hence solve some practical problems with the aforementioned methods.

We got a humble poster presentation at a national conference this year for this work (I was the first author).

2.) Code optimisation:

I have also made the solvers faster by many orders of magnitudes, when compared to established solvers used in our lab. It has mainly been due to vectorisation. For a scalable solver like mine, which should adapt to not just cells but number of ghost cells as well so that higher order accuracy models can be easily included, vectorisation was not exactly easy because of its sensitivity to indexes and array sizes. But I was able to generalise the process pretty well. My explicit loops in total, for a multiphase problem with velocity and pressure relaxations is THREE. That is it. As the dimensions of the problems increases, processes like primitive to conservative variables conversion and vice versa scale even better, because of the aforementioned loop-less SIMD method.

I am sure there are many such techniques to explore, and applied to unstructured meshes especially, which are infamous for being hard to parallelise. Reduced ordered methods is another umbrella whose shade I have not entered yet.

3.) Turbulence and PINNs:

Two other avenues I want to explore are turbulence, and use of PINNs. There are some problems with LES that I won't like to discuss in public, because its a gaping hole I have not seen most researchers address, but it is an important one. With PINNs, we can leverage a lot of experimental and numerical data we have over all these years, and use these to train models to a.) extrapolate lower order solutions to higher orders and b.) solve problems in compressible flows and turbulence. There is a massive potential with feature engineering here, activation functions, equations of states and the structure of the neural networks themselves.

Academic experience:

I have taken course on Turbulence from an OG in the field of turbulence, a former student of Pope. Some of my course instructors and LOR writers are alumni of UIUC, Princeton, Purdue + CTR (Stanford).

My bachelors and masters have been done from the ivy equivalents, T10 schools in India. My undergrad GPA is a bit low, around 2.967, but my postgrad GPA is 9.34/10, which should be equivalent to 3.96/4.0.

I have done really well in some related coursework, on CFD, ML and its applications, Turbulence and I have As across my 24 thesis credits.

I have a few more projects, related to writing the kNN classification model and recognising hand written text, writing codes to simulate guidance algorithms for homing missiles (in 2-D) and evaluating factors like control effort, time of interception, positive gain etc. and a few others in ANSYS Fluent and MATLAB.

Schools I am targeting:

Some of the programs where I see a great match with my interest in high speed flows, turbulence modelling and ML application also happen to be the most selective ones.

1.) Aeroastro at MIT

2.) Aerospace at Purdue

3.) Computational Science and Engineering at GATECH

4.) Aerospace at UIUC (CHESS group)

5.) Professor Ricardo Garcia at Cambridge, and Whittle Laboratory with Professor Andrew Wheeler

6.) Oxford Thermofluids Institute

7.) Professor Raman's group at UMich

8.) GALCIT at Caltech, Professor Tim Colonius and Professor Dan Meiron

9.) Supponen group at ETH Zurich

Request:

Please let me know what are my chances at ANY of these places. Many of the places I have mentioned have open positions, but I want a reality check, a brutal one, as to what are my odds. Also, any heads up on groups that you know, for which I could be a decent match is really appreciated.

Hi, I have an airfoil that my professor bought off of Amazon and I was wondering a good way of accurately capturing the airfoil so that I can run it in star ccm+? To clarify, I don’t have any CAD models or dimensions to work with, but I do physically have the blade. I want to start with 2D, but 3D methods are helpful too.

TL; DR: how do PDE solvers accurately perform time integration between solutions that are sampled on different meshes?

Suppose the I have a time-dependent PDE, where the solution at time t is denoted by u^(t). I would like to apply a solver S to advance the solution in time to u^(t+1). This requires discretizing space. We would like for the mesh to have high resolution in areas where the spatial gradient is high to accurately resolve dynamics in this region. However, since the regions of high spatial gradient shift with time, the mesh needs to as well. Therefore, we would like the solver S to do the following computation:

u^(t+1)(M^(t+1))=S(u^(t)(M^(t)))

where u^(t)(M^(t)) denotes u^(t) sampled on the mesh M^(t), and M^(t) and M^(t+1) are constructed to allocate fine resolution in the high gradient regions of u^(t) and u^(t+1), respectively.

My question is how S can be implemented to map between solutions sampled on different meshes. Obviously, we could just integrate u^(t)(M^(t)) to u^(t+1)(M^(t)) using a time integrator like Runge-Kutta, determine M^(t+1) using a software like AMRex by looking at high-gradient regions of u^(t+1)(M^(t)), and then interpolate u^(t+1)(M^(t)) to u^(t+1)(M^(t+1)) -- I think this is close to the approach taken by the original works on mesh refinement (https://www.sciencedirect.com/science/article/pii/0021999184900731 ):

If a new fine grid is created, its initial values are interpolated using the finest grids from the already existing grid structure

This doesn't seem as though it could possibly work well. Since we are allocating new mesh points in places where we think there is error in u^(t+1)(M^(t)), it seems as though interpolating the solution in these regions will not resolve these errors. Instead, it seems like we need to "combine" the two meshes into M^(t) U M^(t+1) and redo the integration u^(t)(M^(t) U M^(t+1))->u^(t+1)(M^(t) U M^(t+1)), and repeat this until "converged", in the sense that our remeshing algorithm doesn't detect any regions with insufficiently low resolution.

Is this close to how re-meshing is actually done?

Hi everyone,

I'm new to the CFD world and for my exam of Fluid Dynamics I have to install StarCCM+ on my Macbook pro m2 pro. The easiest way of course is to install it using paralles, but emulating windows entirely isn't optimal and it's expensive to get the license. I heard that someone was able to install some CFD softwares using Docker and, if I understand well, it is like using only the windows pieces required reducing the load on the machine and basically running it for free. Can someone help me to set up it? Anyone can share with me some feedback about performances and the overall usage experience?

Thanks

Hi everyone,

I’m running a simulation in ANSYS where a capsule at 55°C is submerged in a static water tank at 25°C. I’m calculating the heat transfer coefficient (HTC) using the Surface Heat Transfer Coefficient option, as I plan to validate the results later in a lab experiment. I calculate surface heat transfer coefficient on Shadow wall of capsule

I understand that ANSYS calculates HTC as: h = q / ΔT, where ΔT = (T_wall - T_ref).

My question is: Does q in this case represent the heat flux coming from the shadow boundary (from the capsule wall to the water near the capsule)? And is ΔT correctly defined as T_wall of the capsule - T_ref, where in my simulation T_ref = 25°C (the water temperature)? Is it correct approach or should I change something?

I want to ensure I’m interpreting this correctly. Thanks for your help!

Hi , I'm new to this channel and not educated in cfd in any way. At the moment I'm constructing an engine which uses Compressed Air. The Two valves (inlet and outlet) are basically just two cylinders which are rotating and every half turn the Hole drilled through the cylinder matches with one hole above and one under the cylinder, letting air into the engine. I now want to calculate the Max Airvolume which is able to travel through the "valve". Is there a way to calculate the flow even at higher RPMs or is it better to simulate the whole Valve. And if I want to simulate the Valve, what software gives me the ability to do fluid simulation with a rotating Valve at different RPMs? Thanks in Advance for an answer.

SOLUTION: the hexes should read as follow:

vertices

(

(0 0 0) //0 inlet11

(0 0 0.05) //1 inlet12

(0 0.075 0) //2 inlet13

(0 0.075 0.05) //3 inlet14

(0.085 0.075 0) //4 xcon5

(0.085 0.075 0.05) //5 xcon6

(0.085 0.175 0) //6 xcon7

(0.085 0.175 0.05) //7 xcon8

(0.015 0.175 0) //8 inlet21

(0.015 0.175 0.05) //9 inlet22

(0.015 0.205 0) //10 inlet23

(0.015 0.205 0.05) //11 inlet24

(0.165 0.205 0) //12 outlet23

(0.165 0.205 0.05) //13 outlet24

(0.165 0.175 0) //14 outlet21

(0.165 0.175 0.05) //15 outlet22

(0.095 0.175 0) //16 xcon1

(0.095 0.175 0.05) //17 xcon2

(0.095 0.075 0) //18 xcon3

(0.095 0.075 0.05) //19 xcon4

(0.2 0.075 0) //20 outlet13

(0.2 0.075 0.05) //21 outlet14

(0.2 0 0) //22 outlet11

(0.2 0 0.05) //23 outlet12

);

blocks

(

hex (0 22 20 2 1 23 21 3) (200 20 1) simpleGrading (1 1 1) // pipe1

hex (8 10 11 9 12 13 15 14) (150 15 1) simpleGrading (1 1 1) //pipe2

hex (4 5 7 6 16 17 19 20) (50 10 1) simpleGrading (1 1 1) //xcon

);

------------

ORIGINAL QUESTION: Hello all, I keep getting the error that my vertices are inside out, even though I've 5x checked at this point (including using Copilot) and I'm at my wit's end, If anyone has any guidance they could provide, I'd appreciate it.

This is the error I keep getting:

"Reading "blockMeshDict"

Creating block mesh from

"system/blockMeshDict"

Creating block edges

No non-planar block faces defined

Creating topology blocks

--> FOAM FATAL IO ERROR:

Block hex (0 1 3 2 22 23 21 20) (200 20 1) simpleGrading (1(1) 1(1) 1(1)) is inside-out

file: /home/91366/openfoam10/tutorials/incompressible/icoFoam/finalProject/pipeProject/system/blockMeshDict/blocks at line 48.

From function void Foam::blockDescriptor::check(const Foam::Istream&)

in file blockDescriptor/blockDescriptor.C at line 100.

FOAM exiting"

Text of my blockMeshDict:

convertToMeters 1;

vertices

(

(0 0 0) //0 inlet11

(0 0 0.05) //1 inlet12

(0 0.075 0) //2 inlet13

(0 0.075 0.05) //3 inlet14

(0.085 0.075 0) //4 xcon5

(0.085 0.075 0.05) //5 xcon6

(0.085 0.175 0) //6 xcon7

(0.085 0.175 0.05) //7 xcon8

(0.015 0.175 0) //8 inlet21

(0.015 0.175 0.05) //9 inlet22

(0.015 0.205 0) //10 inlet23

(0.015 0.205 0.05) //11 inlet24

(0.165 0.205 0) //12 outlet23

(0.165 0.205 0.05) //13 outlet24

(0.165 0.175 0) //14 outlet21

(0.165 0.175 0.05) //15 outlet22

(0.095 0.175 0) //16 xcon1

(0.095 0.175 0.05) //17 xcon2

(0.095 0.075 0) //18 xcon3

(0.095 0.075 0.05) //19 xcon4

(0.2 0.075 0) //20 outlet13

(0.2 0.075 0.05) //21 outlet14

(0.2 0 0) //22 outlet11

(0.2 0 0.05) //23 outlet12

);

blocks

(

hex (0 1 3 2 22 23 21 20) (200 20 1) simpleGrading (1 1 1) // pipe1

hex (8 9 11 10 14 15 13 12) (150 15 1) simpleGrading (1 1 1) //pipe2

hex (4 5 6 7 16 17 18 19) (50 10 1) simpleGrading (1 1 1) //xcon

);

edges

(

);

boundary

(

inlet1

{

type patch;

faces

(

(0 1 2 3)

);

}

inlet2

{

type patch;

faces

(

(8 9 10 11)

);

}

outlet1

{

type patch;

faces

(

(22 23 20 21)

);

}

outlet2

{

type patch;

faces

(

(14 15 12 13)

);

}

wall

{

type wall;

faces

(

(0 1 22 23) //bottom wall

(2 3 18 19) //middle bottom left

(18 19 20 21) //middle bottom right

(16 17 14 15) //middle top right

(8 9 6 7) //middle top left

(10 11 12 13) //top wall

);

}

);

mergePatchPairs

(

);

I'm trying to simulate air flow through a heated copper pipe. The idea is to check if the heating effect makes the air come out faster. The only parameters i know are that the inlet velocity is 8 m/s and inlet pressure is 1 Pa. I do not anything about the outlet. Can someone tell me what settings i should use in setup to get the right solution (I e increased volume flow rate at outlet).

Hello, Everyone

I tried to study how to mesh and validation result of my simulation.

My result is still not quite correct compare to the reference that I refer from Simscale.

https://www.simscale.com/docs/validation-cases/turbulent-pipe-flow/

3D Geometry

Mesh For Wall Function

It's simple simulation of a water flow in a pipe.

I have tried to mesh and expermental with Wall Layer Function by using K-Epsilon and SST Omega,

But the pressure loss prediction by Autodesk CFD result still not quite close to the analytics result value,

The Analytics calculation of Pressure Loss Along the pipe length should be 1580 Pa to 0 Pa.

Pressure Loss Reference from Simscale Website

Velocity Profile Reference From Simscale Website

I think, I might have do something wrong.

So Let's me know what you think about my result ?

Any suggestions are welcome, and I really appreciate for your time.

For K-Epsilon ,I have aim Y+ Around [35,300] and For SST Omega Y+ is below 1.

Thank Everyone.

FOR K-EPSILON MODEL

Turbulence Model : K-epsilon

Velocity Inlet : 1m/s

Pressure at Outlet : 0 Pa

Estimated Wall Distance For Y+ = 35

https://preview.redd.it/8fdl3hod094e1.png?width=276&format=png&auto=webp&s=d49f8ea5fb0d9ce9c60e5f7cd889e434e8115366

Wall Distance

Mesh

Pressure Loss Plot from Center Of Pipe Inlet through Outlet

Velocity Profile Across Pipe Diameter

---------------------------------------------------------------------------------------------------------------------------

FOR SST OMEGA MODEL

Turbulence Model : SST-Omega

Velocity Inlet : 1m/s

Pressure at Outlet : 0 Pa

https://preview.redd.it/t0yb9d5yy84e1.png?width=423&format=png&auto=webp&s=303922f6689c8de318714e9f67ad07bc07878570

https://preview.redd.it/m3cfbjk9094e1.png?width=273&format=png&auto=webp&s=6dbde748e7596fc517e07fd15dd6cc6b6059b8f6

Estimate Wall Distance For Y+ =< 1

Mesh

Pressure Across Center Of Pipe Inlet through Outlet

Velocity Profile Across Pipe Diameter

Guys I have been doing transient analysis. I am new to it. Now the problem is for Ahmed body with a slant angle of 35 and the velocity being 40m/s² the drag co-efficient is 0.35. But from some paper I saw the CD is 0.26.But I can't be sure of the paper I am literally confused. Is my answer even correct .

I want to develop a GPU first solver, but I don’t want to work on an LBM solver because of its drawbacks. On the other hand, it seems that unstructured FVM and GPUs do not work well together because of their fundamental properties (ie. unstructured memory layout, implicit solvers, sparse matrix etc). So, for a GPU-first solver, what do you suggest I research and implement instead of traditional FVM? Think this as a long term side project so I am completely free about it.

On BBC they said they evaluated over 2000 designs and show CFD simulation in the end. I am wondering how long it took them to do that. I already struggle with meshing of a simple stirred tank 😅 What are your thoughts?

https://www.theengineer.co.uk/content/news/ai-designed-birmingham-blade-is-optimised-for-urban-wind

Hello, I have been doing PhD for the past 4.5 years. I contributed to four SCI journals and all were published with my name. Now, I need to produce two more articles. However I will be moving to a full time position, due to my financial problems. Please throw your advises to complete two reasearch article. I am asking you because my prof can't guide me directly hereafter. If you know any consultancy who helps PhD student to publish SCI journals, please let me know. I am asking here because folks can suggest me something to do with CFD.

arxiv

https://preview.redd.it/tync79nln24e1.png?width=1204&format=png&auto=webp&s=d09369a03d6b3c54b6df84d91f16caf56e13d804

https://onlinelibrary.wiley.com/doi/full/10.1002/zamm.202100254

this is the link to the paper, it use GENERIC framework to derive the PDE system of reactive flow, and there are even some papers that use the same framework to derive the PDE system of fluid structure coupling, maybe in the future we must learn a lot of statistical mechanics to become a good CFD engineer

For those working on CFD and related fields, consider cross-posting some of your detailed or exploratory posts to r/VXJunkies. It's a satirical subreddit that thrives on highly technical-sounding content. I know nothing about CFD, but all the posts I’ve seen here—charts, simulations, rotors, matrixes, discussions, tutorials—would fit in perfectly.

Make sure to keep the acronyms coming, like STAR-CCM+, ANSYS, and all that jazz. The overlap in tone could highlight some humor in the field—or maybe even spark unconventional ideas?

Why not share and see how it’s received? Just an idea from a lost redditor 😁

I am a Mechanical Engineering student, and I want to learn ANSYS CFD. Can someone please guide me on where to start and provide some resources? I have a basic knowledge of CFD, but I’m struggling to find tutorials on YouTube that cover the in-depth process I’m seeking, as most of them lack detailed explanations.

Hey everyone, I’ve been working with Fluent on some pretty complex models with tons of parts, and checking if emissivity values are set correctly has always been a pain. I thought, "Why not just plot emissivity on a contour plot?" But turns out... you can’t.

So, I hacked together a little script in pyFluent to do it:

• It makes boundary regions for each emissivity value.
• Assigns emissivity values as expression to those regions.
• Then plots it all in a contour plot.

It’s not the most elegant solution, but it gets the job done.

Do you have a better way to deal with this? Have you had the same problem?

If you're curious about the script, just let me know, and I’ll share the details!

I need to simulate this type of wing, but in the cell quality control I have about 70000 cells under 0.15. Some mesh data: 9mln cells, control surface of my wing with target surface size 0.6 and minimum surface saze 0.02 percent of the base (only these two are custom). (base = 1m). Prism layer thickness 0.0057m with 28 layers. I already tried to decrease the minimum to 0.01 and the curve is better defined but it does not improve the quality of the cells (the number of cells under 0.15 doubles). What can I try?

https://preview.redd.it/8p2kw4h1ly3e1.png?width=1172&format=png&auto=webp&s=0ea7c66ee56fc23ea2c6b8975fb60de08895484a

https://preview.redd.it/sih7f6h1ly3e1.png?width=1177&format=png&auto=webp&s=12752b05e231f4a69103e3d8a4905a853cbcad49

https://preview.redd.it/vfahgbi1ly3e1.png?width=1173&format=png&auto=webp&s=7502c44d1f62ff45c23f9710a9df39e9f5003a68

https://preview.redd.it/m3f0m6h1ly3e1.png?width=1037&format=png&auto=webp&s=8efb9df443f1ec94d50e6e59d53b130cae3abd87

https://preview.redd.it/xeltykh1ly3e1.png?width=1163&format=png&auto=webp&s=36251f0ef42bc72bc70a67b0653e3e8bcf09cb78

https://preview.redd.it/c6m1v8i1ly3e1.png?width=1163&format=png&auto=webp&s=088b9ba2c721b94760437bc9ee50060ad8d09d3a

In figure 2 of https://arxiv.org/abs/2212.07564, the pressure ranges from -4.6K to 1.5K:

https://preview.redd.it/c1ccavvnkx3e1.png?width=3115&format=png&auto=webp&s=09e86f7c91ce4d33c99f89b4b917ff14108d088b

However, I thought pressure could only be positive. I emailed the author and asked if it was because of subtracting away a reference pressure, but he said no, and that reference pressures were only necessary in the compressible case.

Various sources online seem to indicate that negative pressure equates to suction. I am just surprised, since I though pressure was proportional to density divided by volume, and since both density and volume are non-negative (by my understanding), pressure should be as well.

Hello everyone,

I have very minimal understanding of CFD but I have a grandfather who wants to get a new pc for CFD computations. He has been using an old dell workstation with a Xeon 2145 processor. He has been able to do calculation with 8 million or so nodes but would like to be able to do up to 20 or 30 million without the pc taking weeks to do the calculations. I'm hoping that someone on here is more knowledgeable than me in this field and would like to help me figure out what parts would be best for him. He is a retired engineer and is doing the calculations. I am fairly well versed in building pc's but he would be more at ease with mostly prebuilt that I could slightly modify. If anyone has suggestions and would like to help me help an old bored engineer it would be greatly appreciated.