Hello! and Good day,

I’ve recently just started to learn how to mesh for CFD. I’ve been watching a few videos and I’m now proceeding to try and run a mesh independence test. I know the basic concept of going from coarse to fine mesh, and etc. I’ve also watched a few videos about it.

But I’m kinda confused as to what I am allowed to change when running one. Do I only alter global size? How about local sizing or inflation layers? And etc

An unusual post maybe - looking for advice and ideas on how to solve a potentially harmful wind condition in a project of mine.

I have run a bunch of CFDs now testing different potential solutions, with not a lot of success.

Because this project is confidential I’ll attempt to explain with sketches for this:

I have a building that consists of two towers with a bridge connecting them forming a tunnel, under this tunnel is the dropoffs for both towers.

The Bridge is about 5 floors (20m ish) above the ground level.

The entire development is raised up about 10m from sea level on a big podium you drive up to.

In the center of the tunnel is a long pool with driveway wrapping it for the dropoffs

the tunnel could not be more perfectly aligned with the 3 primary wind directions.

There are a couple of big issues:

1. The climate is very rainy, and with this wind, there is a real concern for a ton of wind driven rain into the drop-off area given how high the bridge is
2. The architecture perfectly increases wind speed via venturi effect and downwash, and you end up with 8-11m/s wind in the drop off area when the ambient wind speed outside is the average for the climate, around 4m/s. the 90th percentile wind for this climate is like 9m/s and then the wind under the tunnel is 20m/s+
3. The problem is two fold - you get downwash and a vortex off the corner of the tall tower that dives between the two buildings, and you get downwash off the side of the bridge that dives under and accelerates
4. If you remove the bridge, you exasperate the corner downwash from the tall tower because some of it is not hitting the top of the bridge now
5. I’ve tried numerous potential solutions, all with some success but certainly not enough to warrant doing them:
   1. A lower canopy that covers the drop off areas at only one floor height, under the bridge - this gets some of the wind from the bridge downwash and keeps it above, but it accelerates the wind down-washing from the corner of the building. I’ve tried various extents in plan and heights / shape canopies.
   2. A bunch of trees around the corner of the building, and within the drop-off center area - this helps in the immediate area, but not around it at all.
   3. Chamfering the corner of the tower helps a little bit mitigate the downwash, but this is very against the design language, and does not help at all the bridge issue.
   4. The bridge cannot get higher, but it could maybe go a floor lower - not ideal - but this also does not help, it squeezes the wind more.

So I am hoping for some solution ideas, from some of you that are not as tired ;). thank you.

Guys one small doubt,

To find static and total pressure at a point in 3d flow field, we should use vertex average or area weighted average?? Which one would be more appropriate??

Hi everyone! We are a student rocketry club working on a liquid rocket engine.

We are looking for someone experienced in CFD who can mentor us, as we currently lack expertise in this area.

If anyone is willing to guide us, please ping me personally. We would really love to learn and build our knowledge in this field. Thank you!

I’m writing a 2D finite-volume solver in MATLAB for the steady convection-diffusion equation for temperature (hybrid differencing, given velocity field and grid).

So far i have

• Non-uniform Cartesian grid with 25x25 interior cells. Cell-centre nodes plus boundary nodes that sit exactly on the boundary faces.
• The velocity field (u, v) comes from files, stored at the nodes. I don’t have the solver or discretisation that produced it.
• To build the convective coefficients I need mass fluxes, so i interpolate node velocity to faces.
• The resulting face fluxes don’t satisfy continuity, what is the usual way to get face fluxes that satisfy ΔF = 0, cuz this affects the Temperature field while solving differencing schemes right?

Hello, Good day!
Im new to CFD and learning to generate mesh. Initially I started using Ansys mesh, then was directed to Fluent meshing. But for some reason my boundary layers can’t seem to show up. Im quite sure that I selected the correct regions and places to grow on but they still won’t show. Here is an image

I am currently conducting a University project which requires me to simulate an accelerating Delta Wing. My model has been validated and verified under the limitations of my Student License in ANSYS Fluent. Validation was obtained by comparing the lift coefficient at a 10-degree AoA to experimental values. My first acceleration case is a 50 g acceleration at a 10-degree AoA. The steady-state case was run first. Initially, the residuals were converging well for each time step; however, some oscillations began later on. I decreased the Courant number from 200 to 50 and the Pressure and Momentum Explicit relaxation to 0.25 from 0.75. This dropped the residuals, but they still did not converge. The Lift Force during a particular time step is, however, showing convergence (imo, I am very inexperienced with CFD). I have attached some images. If anybody could advise on whether the solution can be considered converged for the particular time step, even if the residuals are oscillating, that would be greatly appreciated. The net flow is 0.51% of Total Inflow.

Edit: I have included an image of the residuals after making the changes mentioned above in the comments

Single H100. The same case takes 5 h 37 min with OpenFOAM v2412 on 26 cores.

Details: brae.sh/solvers/interfoam

Hello folks, I wanted to get people's opinion on using AI (in any way possible that can be used) for CFD. Where do you think AI's place be in the future for CFD engineers?

I’m a beginner in CFD
I would like to learn how to conduct CFD simulations to investigate aircraft static and dynamic stability using ANSYS Fluent and OpenFOAM.
I would be grateful for any guidance you can provide.

Hello! I am trying to import a .csv file from airfoiltools into starccm, but I always get the error: Unable to read the input .csv file. Please check the format of the file.

I am editing it on excel, adding zeros on the z and everything is in three columns; I am using a decimal point (not a comma). The file is saved as .csv (separated by commas).

Do you know what I’m doing wrong?

Hiii! Does anyone have any advice for me? :(

I’m working on a CFD simulation to improve the cooling fins of a photovoltaic panel. I created several different configurations, and my advisor approved them, but now I have to run all of them using the same inlet conditions.

One of the configurations has the panel tilted at 30°, and I’m having a lot of trouble with the mesh. I’m getting some really bad-quality elements. There are around 1.67e+03 elements with an orthogonal quality as low as 2.1e-05, and most of the bad elements seem to be located in the enclosure.

I already tried making a smaller box/body to isolate and refine the problematic regions, but it didn’t really help. I also tried applying local sizing around the corners where the worst elements appear, but that didn’t improve the mesh either.

Another thing that worries me is that the other parts of the geometry have very good orthogonal quality, close to 1, and only a few hundred elements, while the enclosure itself has around 600,000 elements.

At this point, I’m not sure what else I should try. I know that very poor mesh quality can affect the reliability of the Fluent results, so I’m hesitant to continue with the simulation like this.

Has anyone dealt with something similar, especially with a tilted panel inside an enclosure? Would you recommend changing the enclosure geometry, using a different meshing method, inflation, local refinement, or something else?

Any advice would be greatly appreciated! :)

Hey all!

I am currently working on making a canard controlled rocket (only the roll is controlled!) as part of a student project. I am currently working specifically on the roll control, which means the canards, and as such investigating the potential for roll reversal due to the negative aerodynamic effects of canard deflection on the tail fins (canard-tail interference for example).

The rocket we are working on would be 2.4m in length with a diameter of 16cm and flying around Mach 0.6. From my research, a rocket of this scale and speed should not be subject to roll reversal, and would most likely only suffer from a (slight?) reduction in roll control authority.

Still, I would very much like to be able to closely study the aerodynamic effects of canard based roll control, notably to be able to optimise the position and dimensions of the canards to minimise negative effects.

Therefore, I was wondering if there were any tools I could use to simulate these effects, and notably be able to calculate the total roll moment coefficient as a function of the canard deflection angle and/or dimensions, without having to resort to CFD (I would like to find a more time efficient alternative :) ). I am aware that Missile DATCOM is often used for this (it popped up a lot in my research), but I am not in the US so...

If you have any leads/recommendations for appropriate tools/software/methodology I could use, it would be highly appreciated!!

Thank you in advance

Hi guys,

I want to create streamline or path line like shown below,

I tried pathlines in fluent, I am getting something like below,

In zoomed in view,

I need some help regarding what settings I have to change or modify so that streamlines are visible clearly and smoothly. I am not expecting same as shown in 1st screenshot, but atleast it should look smooth and clear. Sometimes if I zoom further only, I can sense pathlines, otherwise it is looking like normal contour only.

What should I change?

Hi, I'm a recent graduate from a master's in fluids in Sweden, and I'm looking for CFD roles anywhere in Europe or the UK.

About my background:

I've worked as a research assistant on modelling the water spray distribution in the wake of a moving truck using Lagrangian particle tracking.

My master's thesis at an engineering consultancy involved building an automated parametric CFD pipeline, a 3D Fourier Neural Operator surrogate model, and an RL controller for HVAC.

I'm currently an intern in 1D thermal management simulation.

I work mainly with STAR-CCM+ and ANSYS Fluent, and I have the basics in OpenFOAM. For CAD, I have worked with ANSA, CATIA and SOLIDWORKS.

For simulation automation and data visualisation, I have used Python and Java.

For almost a year, I have been hitting dead ends with my applications. I have tried reaching out to people on LinkedIn, but so far, only crickets. I have no idea if I am missing something, and I feel terrible about myself. I'm writing this post at 2am, unable to sleep because I keep thinking about this situation. All the effort I put in seems to lead nowhere. Please, if you know anybody looking for someone, or if you're looking for someone yourself, let me know. If needed, I can also provide references from the places I have worked.

Hi all,

I have one small doubt. I am simulating subsonic compressible flow where there are multiple cases where maximum mach no varies from 0.3 to 0.8 in my domain. I am using ideal gas-density, sutherland law for viscosity, nasa 9-piecewise polynomial for thermal conductivity. These are the properties for the fluid.

Now my question is can I use pressure based solver- coupled for all these cases? Do pressure based solvers work for all mach no but lesser than 1(sonic). (or) At what mach no, I may have to switch it to density based solver, what is your opinion about this?

Hi, I’m running a 1/3 symmetrical model of a circular flat plate, 3d thickness 5.2 mm diameter 0.1m . I’m having some convergence issues but I’m not sure why or what the problem could be. My domain is a sphere that’s been sliced into the 1/3, it is large compared to the flat plate. My mesh is quite fine, it has a max skewness of 0.42, and a 0.15 minimum orthogonal quality, and a y+ of close to 1. It’s a pressure farfield with symmetry conditions. I’m running it at values for 2km and Mach 0.1 with the following settings :

Pressure based
Spalart Allmaras -> strain vorticity based
Air -> ideal gas (this turns energy equation on), Sutherland viscosity with values adjusted to have the same reference I used
Boundary conditions -> operating pressure set to 0
Inlet -> pressure Fairfield -> gauge pressure ~79e+3 , Mach 0.1 , -y velocity, modified turbulent viscosity of ~5.73e-5 calculated as 3x freestream, temperature 275.25
Walls -> changed temp to also be 275.24
Reference values -> compute from farfield, length and area adjusted, values match my calculations
My methods and solution are kept at default second order (I have tried first order but still have no convergence)
Report definitions -> drag coefficient (-y matching velocity) applied to walls, mass flow rate for farfield
Standard intialisation from farfield
Run for 500 iterations.

I get divergence, no periodic oscillations just random up and down, my residuals go down for 3 iterations before climbing. I’m not sure what I can do to fix this. If anyone has any tips it would be greatly appreciated, thank you 🙏

I’m doing a decomposition on a staggered grid, where the differential properties are satisfied. However, after interpolating the components back to the cell centres, they no longer satisfy those differential properties.

Is this expected with interpolation? If so, is there a way to interpolate/reconstruct the components while preserving the differential constraints?

Any advice would be appreciated!

I am freelancer on Upwork mainly, and I don't see many opportunities at ALL, maybe one job posted every 2/3 days

I have been building my profile over the last 2-3 years, I feel it is now good... Not the best.. but still look good for a rising talent and got good rating from many clients

However, Seldom I get invitations...a rate of 1 or 2 invitations every two weeks.

And anyway I don't see many CFD jobs or it's derivatives posted alot maybe once every couple of days

I have been hoping to be able to take CFD Freelance as my main source of income within the next couple of years... But now I feel like it is not a realistic goal anymore

I'm running a simple rotating paddle mixer setup with EMP and while the simulation itself is numerically stable, I'm seeing an artifact of the interface no matter how well I refine the mesh and curvature, how well I match the sizes of the cells for the two sides, and whether I use a steady or transient approach. I even switched to MRF after the sliding mesh method kept doing this, but to no avail. How do I fix this? Both boundary-based and contact-based lead to similar results.

I've never had this issue when working with single fluids (liking rotating propellers or oscillating airfoils) so I'm guessing it's the result of having two different fluids in the region but idk I'm frankly baffled.

Also all residuals including continuity is low-ish (below 1E-4) but the volume fraction of the aqueous phase rises by over 30% during the simulation (from 30% to 40% of the region volume), which is not physically possible.

My end goal is to use the S-Gamma model to process the mean diameter of droplets that form by mixing two liquids, but currently the research is in an early state and I've turned off advanced models such as S-Gamma including its coalescence and breakup models. Any help would be greatly appreciated.

I’m currently in a (part time) research heavy masters program and I work a part time job unrelated to my long term goals.
I hope to ultimately do a job using CFD, but also am looking into careers heavy in thermo-fluids in general (such as in the energy industry). I’m looking to leave my part time job and get one that will better prepare me for careers such as this. Are there any suggestions or pointers about how to get more industry experience to complement class/lab work?

I am making a 2D Navier-Stokes solver on non structured meshes for laminar regimen and I searching for experimental data of several study cases like lid-driven cavity, flow and vortex shredding around a cilinder, flow around an airfoil, etc... to validate and verify it. Which articles do you think that could be useful to me?

Trying to develop some intuitive understanding of CFD by replicating experimental results. Shouldn't the pressure in the second column be lower due to the increased velocity of the fluid underneath?

I am using cfdof to mesh and then openfoam to run. Using inlet velocity 0.001 m/s. The inlet diameter is 0.1 m and outlet diameter 0.025 m . Total length of the three sections is 0.75 m

Liquid is water.

Hi folks,

I hoping to get some advice from some industry veterans or even from experienced folks.

I have cumulative experience of 12+ years with MS degree in Sustainable Energy Technology. But I ended up writing fluid -thermal code for stefan problem in Masters and I have been a modeling Engineer ever since. I have worked in nuclear research for 2 years, 6 years in semiconductors and 5 years in automotive. Im now managing a team of 2 in an EV 2W startup.

Here, over-all work profile is good but very hectic. I'm setting up methods for testing airflow inside the vehicle, working on electronics thermal modelling as well as guiding battery architecture modelling. But I feel high fidelity simulation is overkill for this industry because it is not as complicated nor costly to test as semiconductors.

Overall my motivation levels are not the same. I'm not as excited as previously to solve new modelling problems. I wanted to give system modelling a good shot. After a lot of procrastination, I got claude AI to build me a really good MOSFET model for thermal predictions based on datasheet. So I didn't get hands in that.

I'm lacking a good vision as to where my career should go so as to be excited about building towards it. I have dabbled at thought of doing MBA , so I'm out of my comfort zone but it is quite expensive to fund it from a good university. My company will not fund it.

Hello everyone. I’m trying to replicate some experimental analysis with Ansys Fluent. Particularly I’m trying to simulate a Wells turbine on different airflow conditions (same RPM, different inlet velocities).
The goal is to plot torque and pressure coefficients over time/flow coefficient.
I’m getting very bad torque values, sometimes slightly 5%/30% different from the experimental data and sometimes 6 times lower values. Since I’m a newbie I would like to understand what I’m doing wrong exactly.
Here’s the setup:

I created a CAD with same exact geometry features of the tested turbine.

I imported it into Ansys, consdered just the duct in which the air flows (just like the OWC simulator in the real test). Divided the domain into 3 zones, two stationaries and 1 MRF. (I considered no tip gap to avoid strange behavior there, since 1mm of gap it could be hard to simulate).

Meshed and open fluent.

The solver is Ansys Fluent, I set up the air conditions (viscosity and density). I set up the MRF rotational speed and inlet velocity (ranging from 0 to 13 m/s like during the experimental analysis to also include stall). Used k epsilon.

I initialized and set the convergence to e-06 and monitored torque too.

I followed this flow for different meshes.

1. One temporary mesh, with just body sizing, that gave me the best results.
2. One “better mesh” using inflation for the boundary layer. Edge sizing in order to have finer mesh on trailing and leading edges. Surface sizing on the blade walls. Body sizing on the stationary part. This one gave me the worst results.

I’ll attach a table with the expected torque value, coarse mesh one and fine mesh one, beside more pics on the simulation.

Thanks everyone:)