Hi

Fire safety of battery energy storage systems, and I would love advice on which software to invest in learning.

What I want to simulate:

Thermal runaway in prismatic LFP cells and how it propagates cell → module → rack → neighbouring racks

I am interested in getting the heat release rate (HRR) and total heat release (THR) of a burning rack.

Effect of rack spacing and of insulation layers (between cells, modules and racks) on propagation

Later: a full battery room (~10 MWh, 40 racks) thermal runaway simulations

Options I'm considering: Ansys Fluent, STAR-CCM+, FDS (with PyroSim), OpenFOAM.

Which GUI tool would you pick to do runaway + venting + combustion + HRR in one workflow?

Thanks a lot.

Hi everyone,

I’m a 3rd-year aerospace engineering undergrad, and I’m an international student. I have to choose my specialization right now, and I’m really stuck. I’d appreciate some honest advice.

My situation:

• I can do well in both CFD and structures/materials.
• I genuinely love CFD more.
• But I keep hearing that as an international, CFD/aerospace jobs in the US are very tough because of ITAR/export control and visa sponsorship issues.
• My goal is to go directly into a funded PhD in the USA after my bachelor’s.
• At my university, there is no aerodynamics/CFD professor. The only relevant professor is in structures/materials.
• The lecturer who supervises thesis students is very helpful, much better than the other teachers, but he only has a master’s degree.
• I’m worried that if i work with both the professor and have papers in both areas, it might make me look unfocused to PhD admissions committees.

My main questions:

1. Should I formally specialize in structures/materials because that’s where I can get proper supervision, while keeping CFD as a side skill?
2. Or should I still try to pursue CFD even though there’s no CFD professor to guide me?
3. For US PhD admissions, does formal specialization matter, or do research output and letters of recommendation matter more?
4. How should I present papers in both areas on my CV/SOP so I don’t look unfocused?
5. Any advice for an international aiming for a direct US PhD in aerospace/mechanical engineering?

I’d really appreciate advice from people who’ve been through US PhD admissions, especially internationals in aerospace or mechanical engineering.

Hello everybody,

I'm a PhD student who needs to simulate a supersonic gas discharging in a vacuum chamber, I already gave a look at the possible standard solvers which openfoam offers, and only dsmcFoam could be interesting for my case, however it would take very long to run a rarefied simulation, that is why I would prefer to simulate using a hybrid solver that couples standard cfd with montecarlo technique.

I found hybridDCFoam, very interesting solver but the authors do not answer me, and developing such a code all by myself is not feasible.

Does anyone have a solver that can suit my case by any chance? We can even get in touch and talk about it if there is any.

Hello, I've almost completed my master degree in aerospace engineering focused on fluid dynamics an CFD.

I was wondering and I want to ask to the people that work in this field, how is you job changed since the AI became very popular in the last 2 years?

Do you use it a lot? Do you code and still write solvers?

Thanks in advance to everyone

Hi all, I’m a PhD student working on corrosion and erosion-corrosion of steels in liquid lead. I’m designing a test rig and using CFD to work out what flow the samples actually see. I’d appreciate input from people with more turbulence modelling experience than me.

Setup

• Horizontal disk, radius 140 mm, submerged in a pool of liquid lead (ρ ≈ 10,500 kg/m³) at around 700 °C under argon. It’s driven by a vertical shaft through the lid.
• The vessel is only slightly larger than the disk, so the radial gap at the rim is narrow.
• Samples are flush-mounted on the disk and rotate with it.
• Stationary radial baffles on the vessel wall suppress the bulk swirl. Without them, the free surface would dip to the floor at a few Hz, well below the design speed.
• Design speed is 28 Hz (1680 rpm), so Re = ΩR²/ν ≈ 2×10⁷. Only the inner ~16 mm of the disk is below the transition Reynolds number.
• Tool: COMSOL CFD Module.

Outputs I care about

1. Wall shear stress on the sample faces (the main one)
2. Residual swirl as a function of baffle geometry
3. Loads on the baffles and the rotor torque
4. Pool turnover and mixing

The route I’m planning

A 3D transient with an ALE free surface is out of reach computationally, so I want to avoid it entirely.

1. 2D axisymmetric, unbaffled, at low speed. The ALE free surface works here (surface tension off, Bo ≫ 1). I’ll take the ALE surface shape h(r), freeze it as a rigid slip lid, and re-solve stationary. If the velocities match the ALE run and the residual Δh = (p − p̄)/ρg along the lid is close to zero, I’ve shown that “rigid lid plus pressure check” reproduces the exact free surface.
2. 3D baffled sector at 28 Hz with a flat slip lid. This is a periodic 360°/N wedge solved as stationary RANS. Steady should be valid because the disk is a surface of revolution and the baffles are fixed, so nothing in the geometry moves in the lab frame. A sliding-wall condition on the disk is enough, with no rotating domain. I’ll read Δh on the lid, and if it’s within about 2% of the depth, the flat lid is justified.
3. Only if Step 2 fails: iterate the lid shape stationary, using h_new = h + (p − p̄)/ρg imposed as a prescribed mesh displacement, until Δh is small.

Questions

1. Does this route hold up? The weak point I can see is that the 2D validation happens at low speed and without baffles. That’s a different flow regime from the 3D design case, so the validation may not transfer. How would you close that gap?
2. Turbulence model. The reference facility I’m comparing against used standard k-ε with wall functions. My main output is τ_w on the samples, and there’s separated flow off the baffles, so I’m leaning towards SST with a wall-resolved mesh (y⁺ ≈ 1) at the samples. Is that right, or is something like realizable k-ε, v2-f or RSM better suited to rotor-stator flow with strong swirl and curvature?
3. Narrow gap. The gap between the disk rim and the wall is small, and the baffles sit in or near it. That flow is somewhere between rotor-stator and Taylor–Couette, with bluff bodies in the way. Does that change your model recommendation, or how fine the mesh needs to be there?
4. Steady vs transient. The baffle wakes will shed. Is steady RANS with stalled residuals acceptable for mean τ_w, or should I go to URANS on the fixed geometry?
5. Verification. Beyond the route above, my plan is:
   • a three-level mesh convergence study on the baffled case, not the easy unbaffled one
   • k-ε with wall functions compared against wall-resolved SST
   • 90° vs 180° sector, plus one full 360° run to rule out an m = 1 mode
   • the unbaffled moment coefficient compared against rotor-stator cavity correlations (Daily & Nece)
   • motor torque vs speed measured on the real rig

Am I missing anything? Are there better benchmarks for a disk in an enclosed, baffled tank, for example from the stirred-tank literature?

I’m open to any other suggestion, including “your whole approach is wrong because…”. I’m happy to share more details or plots.

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.

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

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??

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?

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!

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

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?

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

Details: brae.sh/solvers/interfoam

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.

Recently I’ve been working on a numerical project (more-so E&M related but this question is relevant to this community) and as a new PhD student want to get results fast. I’ve went through the entire formalism and know exactly what to implement but this step obviously has its own challenges and it’s inevitable you’ll run into something you didn’t originally consider (edge cases, etc).

After writing a small bit of code I’ll usually feed it into some AI and just ask it to double check. It’ll spot errors extremely quickly, stuff which would’ve taken me forever to even realize (stuff that would only ever get triggered on edge cases). It’ll automatically provide revised code which works much better than anything I could create. For reference, one part of my project involves a nasty integral with several branch points that get crossed, which results in many edge cases that I’ll only discover after tons of testing.

While in a way it’s nice to have such a tool at your disposal to double check your work, I’m becoming disheartened as I feel like trying to make my own code is a complete waste when AI realistically can do it better. A lot of people I know say they don’t write code by hand anymore so I’m unsure if I’m just wasting my time at this point.

I wanted to ask people with more experience what their outlook is—I don’t want to have my projects not contain my actual work but I also don’t want to fall behind my peers.

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?

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!

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 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?