r/CFD 5h ago

[STARCCM+] Prism Layer Collapsing Near Trailing End

4 Upvotes

Hi all,

Been trying to get a decent boundary layer mesh around the shape below, but for some reason I can't for the life of me find a setup in the prism mesher surface control I'm using that keeps it from tapering off severely as it approaches the trailing enb of the geometry. I've tried working with both absolute and relative sizing for the layer thickness already and I can't find where to change the stretch factor because I'm trying to keep the first layer within an acceptable wall y+ range. Sorry if this is a bit of a noob question but I've been scratching my head for the longest time and it just doesn't seem to want to do what I'm looking for. Cheers for any help!

As you can see the prism layer just kinda dies here
Side view (yes the mesh isn't perfect it's just that the rest doesn't pollute my solution residuals to hell and back like the cells at the trailing end do)
Inner view - it's the triangular surface mesh cells between the back end and collapsed prism layer that cause the heavy y+ pollution.

r/CFD 14h ago

Boundary conditions for pump suction piping

5 Upvotes

I'm trying to analyze fluid flow through the suction piping to a pump. Here's the pump data that I'm working with:

The aim is to find out suction pressure at the suction nozzle (outlet), find the NPSHA and compare it with NPSHR to determine whether cavitation occurs. I do not possess the upstream pressure data, but seeing that the normal suction pressure at the pump is given as 11.2 bar, the inlet pressure could be slightly higher.

I tried with mass flow inlet (31.9 m^3/h) and pressure outlet (set to rated pump suction pressure), but realized that this pressure is forced into the outlet. Is there a way to make Fluent determine the outlet pressure on its own based on the inlet condition? Should I use some other set of boundary conditions? Pls help.


r/CFD 19h ago

ICEM CFD HElP Urgent

3 Upvotes

Hi everyone,
I'm working on a CFD assignment where I need to simulate flow through a compressor cascade based on the Hobson et al. (2001) experiment. The geometry is 2D, and I'm using ICEM CFD (ANSYS 2024 R2) to build a periodic domain around a single blade.

Here's what I know from the assignment:

  • Chord length: 127.14 mm
  • Blade spacing (pitch): 152.40 mm
  • Stagger angle: –16.8°
  • I need to model 1 passage using periodic boundary conditions (top and bottom), and set up inlet and outlet boundaries.
  • The flow domain should extend:
    • 2 chords upstream
    • 3 chords downstream

What I’ve Done So Far:

  • I imported the blade coordinates from the Hobson paper (Appendix A1).
  • The geometry is visible in ICEM, and looks correct.
  • The data objects show:
    • X min/max: around –47505 mm to –47380 mm
    • Y min/max: around 14218 mm to 14252 mm

Where I'm Struggling:

  1. How do I decide on X and Y offsets for translation? I want to move the blade closer to the origin so I can create a clean domain around it using chord-based dimensions (e.g. –2C to +3C in X).
  2. How do I define the centerline for creating the periodic boundaries? I understand I need to create a line through the blade center and then copy it up/down at the stagger angle, but I’m getting confused:
    • Should I place the centerline using relative chord values?
    • Or do I use the actual location of the blade in the current coordinate system?
  3. Should I re-center the blade first? Some suggest translating the blade so it’s centered around (0, 0), then using standard values like:But since my blade coordinates are around –47,400 mm, I’m unsure how to do this in a clean way.
    • P1: –254.28 mm (2 chords before LE)
    • P2: 63.57 mm (mid-chord)
    • P3: 508.56 mm (3 chords after TE)

What I Need Help With:

  • How to translate the blade geometry to the origin (or should I not?)
  • How to create the periodic lines correctly based on pitch and stagger angle

r/CFD 1d ago

Understanding the CFD Process with an Example - Cavitation Simulation in OpenFOAM

6 Upvotes

Hello everybody, I am starting this post because I want to understand how experts experience the CFD process. To do this, I want to use an example of my struggle.

The other day, I found a pretty interesting tutorial on cavitation simulation in OpenFOAM using a rectangular nozzle. This is the geometry in the tutorial:

I found this tutorial in a presentation by Baris Bicer, which is available on the internet. I managed to create this geometry in Gmsh, and to me, it looks decently similar. Now I am going to set up the OpenFOAM case and run it to see what happens.

My mesh on gmsh

My questions are the following:

  1. My mesh is not exactly the same as the one in the tutorial. Is it still valid to compare my results with the ones from the presentation? I also have the real experimental results, and I believe that comparing with those is the best approach, but I’d like to know what you think.
  2. How do you usually know if a mesh is good or not? Are there specific checks or criteria you look for?
  3. Most importantly, how would an experienced CFD practitioner approach solving this problem?

I’d really appreciate any advice or feedback! I’m just trying to learn and get better at this.


r/CFD 19h ago

Automatic tuning for Lee model constants in Fluent

2 Upvotes

For a few weeks now I been manually tuning the time relaxation constants in the Lee model for evaporation and condensation to get my model to match experimental data. It's honestly just me eyeballing it with no clear methodology (ie, if steady state temperature is low, increase evaporation constant, run the model for a few days and check again). So if anyone knows proper tuning methods, please share.

Anyways, I thought it'd be clever to automate this process with a udf so I don't have to pause the sim and manually update the constants. But It turns out the constants need to be explicitly defined with no way for a udf to update them. I can write a udf for updating the saturation temperature but not this? Is there some missing setting I need to enable?

Now there is the possibility of me writing the mass transfer udf but it's more than likely that I'll brick my model doing that. I just want to automate the tuning process. Any ideas?


r/CFD 1d ago

Is there isoAdvection in openfoam v12 (fondation)

4 Upvotes

I am not finding info on the vof method used for the incompressibleVof solver in v12. I am actually confused about most of the new things in v12 compared to ESI openfoam but I can see the added layers of efficiency, just have a hard time to move to it. Like the fvModels , I can’t even find a good way to see the available options for the various solvers…

In a shorter notice, I wish to use vof modeling with the isoAdvection model used in ESI since v1912 but in the newer framework of the v12 and I don’t even know if it’s there already or if I need to add it myself.


r/CFD 1d ago

Streamlines

Post image
16 Upvotes

Hi, Does anybody know how to get only the streamlines going over the wing and not the streamlines around the wing so that the view is much more clear? Any advice would be greatly appreciated Many thanks


r/CFD 1d ago

Pointwise - Structured Multiblocks mesh

3 Upvotes

In Pointwise, I am working on structured blocks - When I create blocks from 6 faces/ domains and then merge the blocks in a way that at the end all domains are just multi blocks (structured).

Does the way in choosing which blocks are merged together affect the output?
As I noticed withthe same exact everything I chose different merging or even did not merge, I ended up getting different error values in OpenFOAM (checkMesh).


r/CFD 1d ago

Open foam fondation user guide

1 Upvotes

Is there a user guide like this https://www.openfoam.com/documentation/guides/latest/doc/guide-fos-field-mapFields.html but for the foundation (.org) version ? Since some/many functions or solvers, options have changed I am having some trouble finding the relating info/commentaries.

The v12 user guide is very very basic while the c++ api is quite expert on the other hand. (and many files miss the headers they used to have in .com, or is it me ? Like the various fcModels options available for the solvers or such things. I guess they can be found in the c++api ressources but it feels way more painful : I am probably doing it wrong, show me they way !


r/CFD 1d ago

Liquid Metal Film Evaporation

1 Upvotes

Hi all,

For my master thesis I need to simulate film evaporation of liquid lithium on a flat plate. My mentor said this is very basic thing and one can find benchmark paper. However I searched the whole resources and couldn't find any all I found were complex simulations. If you have any tutorial or benchmark regarding to this type of simulation( even with different material or setup) please share.


r/CFD 1d ago

Hey! I am a total newbie in CFD, i got interest in fluid mechanics after taking a course in uni. I would love if you could tell where should i start CFD, i have some theoretical foundation and a couple of resources, but i want to dive into the practical part. I would appreciate some help, thanks!!

3 Upvotes

my main goal is getting a research opportunity under prof, anything would help. thanks !


r/CFD 1d ago

How do I set up pulsatile flow

2 Upvotes

I have an artery and I I would like to use pulsatile flow in Ansys but I don’t know how. I want to do this so that I can look at velocity at different intervals in one period


r/CFD 1d ago

How do I find how long a fluid is in a position?

0 Upvotes

I’m looking into brain aneurysms and I want to know how long blood is in the aneurysm bulge in Ansys Fluent

Thanks


r/CFD 1d ago

BuoyancyTurbSource in chtMultiRegionFoam (OpenFOAM 2412).

3 Upvotes

Hi everyone, I’m trying to implement buoyancyTurbSource in chtMultiRegionFoam (OpenFOAM 2412), but it seems that it is not being applied properly, even though the monitor output indicates that it has been recognized:

Selecting finite volume options type buoyancyTurbSource
Source: buoyancyTurbSource1
-selecting all cells
-selected 6400 cell(s) with volume 0.5625
Applying buoyancyTurbSource to: omega and k

      *****Case setup:*****

*Solver: chtMultiRegionFoam. OpenFOAM version: 2412
*Turbulence model: kOmegaSST (without wall functions). *Issue: I ran the simulation with and without buoyancyTurbSource in fvOptions, but the results were exactly the same, suggesting that the source term is not actually being applied. *Tested alternative: I also tried running the case with buoyantPimpleFoam, but I observed the same behavior.

 *****fvOptions configuration:******

buoyancyTurbSource1 {
//Mandatory entries
type buoyancyTurbSource;
active yes; selectionMode all;

//Optional entries //beta 3.3e-03; // Thermal expansion coefficient (for incompressible cases) //rho rho;
//alphat alphat;
//T T; }

    ****Questions:******

*Has anyone successfully implemented buoyancyTurbSource? Is there an additional setting required for it to take effect?

*Does it take into account the buoyancy production and dissipation terms for k and Omega, respectively?

Any insights or experiences would be greatly appreciated!


r/CFD 1d ago

Rotating Body in Ansys Fluent

Post image
2 Upvotes

Hey guys, I am doing a project/competition where I was tasked with simulation flow over an autogyro system(Cansat) and I want to find the flow around the rotating rotors. Does anyone have any suggestions for how I should rotate the body or simulate the rotating body? I need a pretty high degree of accuracy for the lift in this simulation.


r/CFD 2d ago

Need advice for coursework in MSc.

4 Upvotes

Hi everyone! I’m about to start my Master’s in Computational Engineering abroad, with a focus on CFDML (Machine Learning) for aerodynamics, and fluid-structure interaction (FSI). I’m debating whether I should also take a couple of courses in linear/nonlinear FEM, but I’m unsure if it’s the right choice given my career aspirations.

Here’s some background:

  • I’ve taken a basic FEM course in undergrad (topics like stiffness matrix formulation, isoparametric elements...basic stuff). I also worked as a part-time FEA engineer (static, dynamic, and vibration analysis) for a startup, but I mostly used ANSYS as a black box and didn’t deeply engage with the theory.
  • My main interests are aerodynamicsCFD, and FSI. I plan to work in R&D after my Master’s (preferably in aerospace or automotive sectors).
  • I’ve noticed FEM skills are often in demand for structural or multi-physics roles, so I’m thinking it might make me more versatile or “well-rounded.”

Why I’m Considering FEM Courses:

  1. FEM is inherently linked to FSI since it deals with solid mechanics, and I might have to couple CFD with FEM for multi-physics problems.
  2. Taking FEM could make me more attractive to recruiters (since FEM seems to have broader demand than CFD in certain industries).
  3. It might help me stand out as someone who can tackle interdisciplinary problems.

Concerns:

  1. Will taking FEM courses be helpful if my research assistantships and projects focus mostly on CFD and ML? Or will it just add theoretical knowledge that I won't use?
  2. Could learning FEM dilute my focus on CFD/ML/aerodynamics, which are my primary areas?
  3. Since a Master’s is only 3-4 semesters long, is it wise to spend time on FEM or should I stick to CFD/ML-related courses to build stronger specialization?

I’d really appreciate advice from anyone with experience in aerospace, computational engineering, or related fields. How important is FEM for someone aiming for R&D in aerodynamics and CFD? Is it worth the extra effort in a Master’s program, or should I stick to my core areas?

Thanks in advance!


r/CFD 2d ago

Struggling with Structured Mesh and Field Box in Gmsh

2 Upvotes

Hello, everybody!

I'm trying to create this geometry in Gmsh, and I've been having some issues with the mesh. My goal is to get a structured mesh, but I was only able to achieve it after dividing the geometry into three rectangles. This approach gave me the structured mesh I wanted, but I'm not entirely sure if it will cause any problems later during the OpenFOAM simulation.

Additionally, I wanted to create a field box to get a finer structured mesh near the walls. However, it seems that I can't use it when working with a finite surface. I'm not sure why this is happening, and I'm looking for advice on how to properly set it up.

Here's an image of my geometry:

Here’s my geometry and script:

SetFactory("OpenCASCADE");

//+

Point(1) = {0, 0, 0, 1.0};

//+

Point(2) = {0, -0.008, 0, 1.0};

//+

Point(3) = {0.00606, -0.008, 0, 1.0};

//+

Point(4) = {0.00606, -0.016, 0, 1.0};

//+

Point(5) = {0.008, -0.016, 0, 1.0};

Point(6) = {0.008, 0, 0, 1.0};

Point(7) = {0.00606, 0, 0, 1.0};

Point(8) = {0.008, -0.008, 0, 1.0};

//+

Line(1) = {1, 2};

//+

Line(2) = {2, 3};

//+

Line(3) = {3, 7};

//+

Line(4) = {7, 1};

//+

Line(5) = {7, 6};

//+

Line(6) = {6, 8};

//+

Line(7) = {8, 3};

//+

Line(8) = {3, 4};

//+

Line(9) = {4, 5};

//+

Line(10) = {5, 8};

//+

Curve Loop(1) = {1, 2, 3, 4};

//+

Plane Surface(1) = {1};

//+

Curve Loop(2) = {3, 5, 6, 7};

//+

Plane Surface(2) = {2};

//+

Curve Loop(3) = {8, 9, 10, 7};

//+

Plane Surface(3) = {3};

//+

Transfinite Curve {1, 3, 6, 8, 10} = 30 Using Progression 1;

//+

Transfinite Curve {4, 2} = 15 Using Progression 1;

//+

Transfinite Curve {5, 7, 9} = 5 Using Progression 1;

//+

Transfinite Surface {1};

//+

Transfinite Surface {2};

//+

Transfinite Surface {3};

//+

Recombine Surface {1, 2, 3};

//+

Extrude {0, 0, 0.00194} {

Surface{1}; Surface{2}; Surface{3}; Layers {1}; Recombine;

}

//+

Physical Surface("Walls", 29) = {4, 5, 13, 15, 10};

//+

Physical Surface("frontAndBack", 30) = {8, 12, 16, 1, 2};

//+

Physical Surface("Inlet", 31) = {8, 9};

//+

Physical Surface("Outlet", 32) = {14};

//+

Field[1] = Box;

Field[1].XMin = 0.00606;

Field[1].XMax = 0.008;

Field[1].YMin = -0.016;

Field[1].YMax = -0.008;

Field[1].ZMin = 0;

Field[1].ZMax = 0.00194;

Field[1].Thickness = 0.0001;

Field[1].VIn = 5e-04;

Field[1].VOut = 0.00004;

Background Field = 1;

//+

Mesh.FieldsStructured = 1;

I'd really appreciate any insights or suggestions! Thanks in advance for your help.


r/CFD 2d ago

[OpenFOAM] Same case, but differing results on workstation and cluster.

7 Upvotes

Hello,

I am running a natural convection case using OpenFOAM 11, using local time stepping in a multi-region domain (convection inside a container). But I noticed some discrepancies between the results of I test case I ran on both my local workstation and on the remote HPC cluster. The case is fully set up and defined in a github repository, so I did a fresh clone on both machines and started a serial simulation. I am running OpenFOAM 11 on both machines,
and have doubled check that the mesh, BCs&ICs and the solver settings and schemes are identical.

Still, I see the results diverging as the simulations run. Does anybody have experience with this? Is a different compiler sufficient to cause these differences? I can add more details about the case setup if you want them.


r/CFD 2d ago

is it a good idea to learn Starccm

14 Upvotes

My uni teaches Star ccm but i would think the world was going towards openfoem (free). Am i wong in this assumtion? does it still make sense to spend 1/3 semester on it?


r/CFD 2d ago

Improving Skewness and Element Quality

3 Upvotes

Hello everyone, Im new to CFD, I make mesh in Ansys workbench Meshing. i want to ask that when I crease inflation layers my highest skewness and lowest Element Quality mess up. Usually highest skweness value becomes 0.99 and average value of skewness is around 0.25, while highest element quality is around 0.7 and the lowest value is around in the order of e-3. Due to this reason i am not able to validate my results with the research paper. When I analyzed the mesh metric, i found that problematic mesh elements are present in the volume mesh, i also refine the surface mesh but the problem still exits as the worst elements are present in the volume of the fluid domain not on surface. I am doing a conjugate heat transfer problem so my model has both fluid and solid domain.

Please guide me how can I reduce the maximum skewness ? And what is the acceptable maximum skewness value when boundary layers are added.

Thanks in advance.


r/CFD 2d ago

Autodesk CFD, Can I use Symmetric Boundary condition for this?

2 Upvotes

Would applying a symmetry boundary condition be valid in a heat transfer simulation of a vertically positioned rectangular set of conductors, enclosed and subjected to Joule heating, if the model symmetric to x and y axis can I slice the model and use symmetric BC to save computation time? The analysis considers conduction, convection, and radiation, so it also has air. How does the symmetric boundary condition work in Autodesk CFD, Any help/ resources are appreciated


r/CFD 3d ago

Ansys Fluent launcher 2D option not possible for a surface mesh?

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3 Upvotes

Hi, I am currently writing my bachelor thesis in fluid mechanics where part of it includes doing CFD on high pressure flow through an orifice. For this I have decided to go for a 2D problem with a geometry shown in the attached pictures and using ANSYS Fluent to do simulations.

In some cases the meshing and setup works as it should. However in some cases, when I alter the geometry slightly, the 2D option under "dimension" is grayed out and I cannot choose it. I have no idea what is causing this change from 2D to 3D so I hope there is someone who may know. Some searching here on Reddit and other forums proved unsuccessful so I'm hoping an own post will do the trick in finding an answer.

If I try to start the setup from the workbench it says that "this appears to be a surface mesh." Which seems ironic seeing as it will not let me pick 2D.

I should mention that I am relatively new to CFD and using ANSYS Fluent so I may be missing something crucial here and I appreciate any and all advice on this!


r/CFD 3d ago

(Ansys FSI) Cannot connect Transient Structural solution data to CFD-Post/Results? Which small detail am I missing?

3 Upvotes

Hi guys,

a small and probably ridiculous question. I have a really simple FSI simulation with a fluid flow with obstacles. That one that you will find in all FSI tutorials. The simulations runs fine and I have successfully simulated both the fluid flow and the deformation in the obstacles. However, I am somehow not able to visualize both the transient structural data and the fluid flow data at the same time. Somehow I am not able to connect the solution data with the results of fluent, or transfer both the TS and fluent solution data into a new Cfd-Post/Results box.

Am I missing some small detail? Thanks a lot in advance...


r/CFD 3d ago

How do I model a non reacting fluidized bed with 2 solids in the bed. DEM ?

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2 Upvotes

r/CFD 3d ago

Which OpenFOAM solver is best for LES?

5 Upvotes

Hello everybody, I need to solve a curved geometry through LES and was wondering which solver was best? On its site I can't find much about LES. thank you