Top left: velocity. Top right: vorticity
Bottom left: velocity mag. Bottom right: density

Simulation:
grid: 200x200
lid velocity: CFL 0.45, wave speed: CFL 0.09 (at time zero)
walls: free slip
approximate Re: ~ 1e6 (from comparing its turbulence intensity against other simulations)
pressure function: shallow water
runtime: around 20 - 25 minutes (around 47,000±2,000 Δt) (35Δt/s)

⠀

After I've done that mach 2.1 simulation, I wanted to see what would happen at higher mach number, so I did it with this water (compressible Euler) solver.

This simulation was started right after I've done the previous test simulation. I've simulated this far, so I didn't bother redoing the simulation.

Stay tuned for the part 3 where I've got ideal gas pressure function and energy equation working properly. It'll have better visualization than this too with proper physical scale.

Here's Part 1 of Supersonic Lid-Driven Cavity Flow Series

I know how to setup the MRF zone in OpenFOAM but I struggle to get convergence. I believe my mesh is not fine enough along the propeller blades. So I want to try and reproduce some results of published experiments to gain confidence with MRF.

The examples I see in YouTube seem hypothetical. Also most example are using fixed/ straight blade agitators. I want to see results from blades that look more profiled like a propellor.

I have so many doubts like what is 1d basically. How its geometry looks like of cd nozzle in 1d. And most impt how to setup its run. And also what is difference between 1d vs 2d

I am using Ansys Fluent to simulate for a slender rocket body without fins. This is at freestream mach 0.8, 37530 Pa, 243.5 K.

When I did this in axisymmetric, I got a positive base drag with an average pressure at the base of the rocket being 36369 Pa resulting in positive base drag.

But when I switched to a 3D model using the same setup but with a 1/4 symmetry, I got a base pressure of 38316 Pa resulting in negative base drag? Now the residuals dropped as low as 1e-4, mass flux seems to be conserved. The average pressure at the base is more than the freestream?? It does not make sense. I thought of plotting velocity vectors, even they seem correct to me.

I thought it may be due to 1/4 symmetry, so I went with 1/2 and full body, same result. I went with transient sim with SAS too. Again, same result.

I know that the info put here maybe not sufficient but if you have encountered even something similar, please do share your experience how you resolved the issue.

Thanks.

Since yesterday, when I finished setting up my simulation, something weird has been happening with the solver. Pressure in a whole area of the building keeps rising linearly, even though the building is split into over- and under-total-pressure areas. The weird thing is that both my inlets and outlets are matched exactly, and so I thought that maybe it could be the difference in air temperature between the inlet and outlet affecting the density of the air and thus creating an imbalance in the system. So I switched one outlet to a pressure outlet, and yet again, pressure kept going up linearly well above atmospheric pressure.

Another thing: my initial conditions are set to 24.1°C, and for some reason, the solver starts at cca 68°C; God knows why :(

Thank you very much if you find a second to help me!

Here is a link to a copy of the project:

https://www.simscale.com/projects/STAN1119/help_1728548534

Hola a todos. Estoy trabajando en un caso transitorio 2D que involucra una turbina. Tengo una pregunta: necesito un refinamiento de malla cerca de las palas de la turbina—representadas por los tres círculos más pequeños que se muestran—pero no estoy seguro de cómo manejar estos cuerpos, dado que están separados de la zona rotatoria. ¿Debería crear una malla deslizante, distinta de la que se usa para la interfaz rotor-exterior? ¿O cuál es el mejor enfoque para asegurar que este refinamiento se mantenga alineado con las palas durante toda la simulación? (Disculpad mi inglés; Estoy usando un traductor.)

I'm working on a multiphase CFD simulation in ANSYS Fluent, and I'm having trouble setting up the interfaces between my fluid regions. I've attached images of my 3D geometry to make the problem easier to understand.

1. Geometry and physical setup

My model consists of three regions:

• 🔵 Blue region – Air: The incoming airflow region.
• 🟢 Green region – Fluid: A separate fluid region that interacts with the incoming air.
• 🟫 Brick-coloured region – Solid: The solid workpiece region.

The physical process I'm trying to simulate involves the incoming air interacting with the green fluid region first, followed by the fluid interacting with the solid workpiece.

Both fluids should remain within their intended regions while interacting across their shared interface. I want to capture the fluid–fluid interaction and the subsequent interaction between the fluid and the solid workpiece.

2. The problem I'm facing

After importing my geometry into ANSYS Fluent, the interfaces between the different regions appear as wall boundaries with a no-slip condition.

The main problem is that I cannot change these boundaries to fluid interfaces. Even when I try changing their types in the Boundary Conditions panel, the changes do not persist, and the boundaries revert to their original wall type when I reopen the panel.

I'm unsure whether this behaviour originates from my geometry setup in SpaceClaim, the way the bodies or cell zones were created, or the interface configuration in Fluent.

3. What I'm trying to achieve

I want to configure the model so that:

1. Air and the second fluid can interact across their shared interface.
2. Both fluids remain within their intended regions, rather than simply mixing throughout the entire computational domain.
3. The second fluid interacts with the solid workpiece through the appropriate fluid–solid boundary condition.
4. The interfaces are configured correctly for a multiphase simulation, rather than unintentionally behaving as impermeable solid walls.

I'm considering a VOF-based multiphase approach, but I'm unsure whether my current geometry and interface configuration are appropriate for this setup.

4. My questions

I'd really appreciate some guidance on the following:

• Geometry: Should I create the fluid regions using shared topology and conformal meshing, or should I keep the bodies separate and create mesh interfaces in Fluent?
• Boundary conditions: Why are the fluid–fluid interfaces automatically appearing as walls, and why can't I change their types?
• Interface setup: Should these boundaries be configured using coupled wall/shadow pairs, mesh interfaces, or another approach? How do I determine which is appropriate for my geometry?
• Multiphase modelling: Is VOF suitable for this setup if both fluids occupy predefined regions initially but must interact across their interface?
• Fluid–solid interaction: How should I configure the interface between the second fluid and the solid workpiece?

sorry for long text, i have generated my text form AI for better understanding of my problem.

Hi everyone! I’m working on my first external aerodynamics study to learn CFD. I’m trying to predict the drag and lift coefficients of a vehicle prototype using ANSYS Fluent Student, with a mesh limit of around 1 million cells. I’ve been having trouble with convergence and choosing an appropriate near-wall treatment.

From what I’ve read, k–ω SST is commonly used for external aerodynamic simulations, often with a mesh targeting y+ ≈ 1 or lower to resolve the near-wall region. However, achieving this while adequately refining the rest of the domain is challenging within my cell limit.

I’m also considering realizable k–ε with a wall-function approach targeting y+ > 30. My understanding is that this could reduce the near-wall mesh requirements, although predicting separation under adverse pressure gradients may be more challenging. I’m unsure which near-wall treatment would be appropriate: standard wall functions, scalable wall functions, non-equilibrium wall functions, or enhanced wall treatment.

The vehicle uses narrow bicycle-type wheels, and the rear wheel is enclosed by a fairing. One geometry-related question is whether I should include the air cavity between the rear tire and its fairing, or simplify that region. What level of detail is appropriate for this type of simulation?

My current setup is:

• Steady-state RANS with k–ω SST.
• Inlet velocity: 8 m/s.
• A symmetry plane.
• Rotating-wall boundary conditions for both wheels.
• A moving ground.
• No rear tire cavity volume (fully closed).

As for the mesh:

• 1M cells.
• Minimum orthogonal quality 0.12
• Body of influence regions and local sizing.
• Last Ratio method and 15 boundary layers (first cell height adjusted)

I estimated the first-layer height to target y+ < 1 and ran the simulation, but the drag and lift coefficients did not settle to constant values.

I’d appreciate some advice on the following:

1. Are there any obvious problems with my mesh or near-wall approach?
2. How can I distinguish numerical convergence problems from flow behavior that may require a transient simulation? Or perhaps it is a geometry issue.
3. Within the cell limit, would you prioritize an SST mesh targeting y+ ≈ 1, or consider realizable k–ε with wall functions?

I’ve attached the drag and lift coefficient histories, a mesh view, a y+ contour, and a velocity plot.

Any feedback would be appreciated. Thanks!

Y+ Contour seems to be fine without going in between de 5-30 region.

Has anyone here been working on those gigs where you can do CFD for AI training? I know it's kind of digging my own grave thinking long-term, but has anyone earned decent money from it? I lost my job and have been looking into different alternatives until I find something

Hi everyone! I'm interested in learning SIMULIA XFlow for CFD simulations, particularly for aerospace applications.

What resources or tools would you recommend for a beginner? Are there any good tutorials, documentation, sample projects, or YouTube channels to help me learn the software?

I'd appreciate any tips from those who have experience using XFlow. Thanks!

Guy's actualy iam doing an final year project , in this we will aim to improve the aerodynamics performance an existing RG-15 airfoil throungh an bio inspired , for first bird we have choosen an albatros by this we actualy desinged an airfoil through its wing characteristic , when we do an CFD analysis the result (CL,CD) where abnormal then usual , actualy we all the checked again and again from mesh to setup , we dont know what to do get the result , actualy we have to show the result to our guide tommorow , if you guy's where anybody free, can you do as CFD analysis for us , i will give you an step or iges file of an airfoil and give you an all the parameters to do

I opened VSPAERO on my model, there were no graphs in the convergence or any other tab, and in the viewer tab my model is fully purple and it does not change when i change the AoA. Any advice would be helpful, i heard there might be a problem with vertical the stabilizers but there should not be the problem since i dont have one in my model. I have a basic model with only a stock fuselage and a lightly modified wings, i only wanted to test VSPAERO but i did not expect to run i to such problems on my first try. I also tried a more advanced model but i ran into the same issues.

Hey Folks,

As part of my thesis, I am supposed to carry out a complete melt pool + single bead + multiple bead walls.

For those who don't know what ARC DED is, it's also known as WIRE ARC ADDITIVE MANUFACTURING (WAAM). It's a form of controlled layer deposition incorporating Welding.

Though I am not new to Fluent, my only superpower is replicating a video, and on my expectations youtube is filled with Demonstration videos than case setup. Literatures does provide a model overview, equations that will be used, but far from setting up.

CFD is being done so that complete surface morphology, effect of gravity, maragoni forces, shear, surface tension, etc are captured.

Kindly assist in Model Development.

​

I'm looking to build or purchase a top of the line CFD workstation specifically for computationally intensive marine hydrodynamics simulations, turbulent flows, rotating machinery, and complex boat geometries.

My primary tools are ANSYS Fluent and OpenFOAM, with simulations potentially involving 5-10 million mesh cells, transient flow analysis, and multiphase CFD.

I'm particularly interested in recommendations regarding:

1. CPU: AMD Threadripper PRO vs AMD EPYC vs Intel Xeon. Is 64 to 96 cores the sweet spot, or are there diminishing returns?

2. RAM: 256 GB, 512 GB, or 1 TB for large transient simulations?

3. GPU: Do NVIDIA professional GPUs provide meaningful acceleration for these applications?

4. Storage: Optimal NVMe SSD configurations for massive CFD datasets.

5. Parallel performance: How well do Fluent and OpenFOAM scale with increasing CPU core counts?

6. Hardware: Would you recommend a powerful single workstation or a small computing cluster?

My background is biology and I'm particularly interested in hearing from engineers and scientists in the CFD marine Hydrodynamics field running serious marine CFD simulations rather than synthetic benchmarks.

Real world experiences, solver benchmarks, and complete hardware configurations would be greatly appreciated! Thanks

I have been given a simple 2D rectangular mesh file. I can adjust the height and length of this with Mesh -> Scale... easily enough, but then the grid cells become compressed where I have reduced the length.

Adapt -> Manual... or Automatic... and selecting the channel as a region (both the exact size, and a region slightly larger than the grid) hasn't worked with any combination of coarsening settings I've tried so far to decompress them.

Meshing mode doesn't work with the mesh file I have, no edge groups, no way to visualise it etc, and in the context of the course I'm doing I'm assuming it can be done in Solution mode somewhere.

How do I simply change the number of cells in the x and y directions?

Hola, soy nuevo en esto del CFD, vengo del diseño orientado a los vehiculos y quiero empezar a agregarle calidad y valor a los proyectos con un estudio CDF.

Empecé hace una semana a ver y probar Ansys Discovery con la version gratuita.

Puedo realizar una simulacion basica pero no entiendo como analizarla para modificar o no el modelado.

Muchas gracias!

So iv been working on this project for a couple of months, I wanted to show it because I finally believe it is a bit presentable now, it is basically a gui with openFOAM, and additionally I added TENO schemes from Fu et al, I thought it was an interesting paper and I wanted to add higher order schemes to achieve higher accuracy (note that I also like swirly lines), going through this project I will be extending it to Ji, Liang & Fu 2021 for unstructured meshes when I have the time. Since most of the coding in this project is human slop, apologies in advance for any bugs that may arise (I lost sleep because of segfaults in cpp)

Source code: https://github.com/CakeCFD/cake-studio

Website: https://cakecfd.org/

I would like opinions from fellow engineers on how to improve this further and make this better, or more specifically what validation case would you trust before using the TENO schemes?

So, im a first time poster so pls be kind :) Also english isnt my first language so excuse any mistakes in my writing

Anyways, I just started my masters in computational mechanics, and I only had some basic knowledge on the subject from my postgrad (plus I only know C++, Matlab and theoretically fortran but not really). They just told us to write a code with a basic grid (like 3x3 or 3x4) and create a NOP(I,J) function, where I is the number of elements (square elements), J is the number of local nodes (J=1,...,4), and the output should be the global node corresponding to a specific local node of a specific element or something like that. Forgive me if the explanation is garbage, I understand it theoretically but not 'computationally' per say.

Does any kind human 1) have any idea of what i'm trying to say and 2) know how to actually help me? for some reason i cant find ANYTHING by googling, and no reddit posts as well (may have missed though). even AI cant help even though i prefer not to use it

Ty for reading xxx

I’m doing bachelor in Mechanical engineering. I’m interested in learning but don’t know where to start from can you give some beginner friendly tips and should i learn open foam or ansys

Im still in school & ik im gonna major in aero so i got openfoam a couple of months ago but never got the chance to learn.

Hey everyone!

I'm a 31-year-old mechanical engineer with several years of experience in Oil & Gas (Project Engineer), Tool Installation (Team Lead), and currently BIM (Technical Expert / Mechanical Piping Modeler).

My dream has always been to work in automotive or aerospace engineering, especially in design and aerodynamics. However, career opportunities led me elsewhere, as these fields are almost nonexistent in my country due to the lack of R&D.

Now that I've graduated, I'm considering pursuing a Master's in Computational Mechanical Design in Europe to transition into CFD, aerodynamics, or mechanical design.

My question is: Is this a realistic career move at 31, with no professional experience in CFD or design? Would my previous engineering experience be valuable, or would I essentially be starting from scratch?

Thanks for your time!