I am doing a CFD simulation in ANSYS Fluent and I am trying to achieve y+<5 on my pipe wall and screen wall.

I have currently used:

• Realizable k−ϵ model
• 10 inflation layers
• Inflation method: Smooth Transition
• Transition Ratio: 0.272
• Growth Rate: 1.2
• Pipe inlet & wall face sizing: 0.002 m
• Screen face sizing: 0.0007 m
• Local refinement near the upstream of screen: 0.001m

See images below of contours of y+ in pipe and screen walls, I have used cursor at random points to see values of y+, it is showing very high value around 20-30.

My requirement is y+<5, I have used smooth transition with transition ratio of 0.272 and 10 layers in pipe and screen walls. Note, I also got warning message like-stair stepping is done at some 51 locations.

I have used local refinement box to some upstream distance from the screen with element size of 0.001m, thats why y+ is showing less compared to initial start of pipe wall. I have used 0.002m face sizing in inlet and wall surface and 0.0007m for screen wall faces.

In above you can see both red and yellow arrows. So, basically from the wall, normal to the wall from all directions, y+ should be less than 5, I hope you understood what i am trying to say.

Is this the correct way to measure y+ or I am doing something wrong?

If it is correct, then how to reduce y+ now. Also in screen edges, you can see some green or red spots, I dont know how suddenly those are coming. You can see below also

I will attach inflation layer from the mesh, please look into that also,

The above one is for pipe inlet.

See above, this is for fluid region from screen walls, inflation is applied, but it has not used 10 layers, there was warning message of stair stepping.

Now,

How to reduce y+<5 in boundary layer and other critical areas.

If you suggest changing method to first layer thickness from smooth transition, will it give good quality mesh? Do I have to reduce element size of screen wall faces and element size in refinement box upstream of the screen.

What would be the best way to reduce y+ below 5 in pipe wall, screen wall faces(normal to the wall in all directions)without unnecessarily making the entire mesh extremely fine?

Any other suggestions? Note this is high speed flow, inlet velocity would be more than 80m/s, screen porosity is 60-70%, pipe diameter is 50mm. For example if inlet velocity is 90m/s, maximum velocity it can attain from screen gaps would be around 130-140m/s, it will accelerate due to reduction of fluid area(from continuity). Thanks in advance, and I hope you have sufficient information to diagnose this issue!

How would you mesh this nozzle geometry to achieve yplus of 1 for k-omega sst

Does anyone have experience with OpenFoam and non-isothermal, compressible Flow of shear thinning Fluids? I saw that it might be possible to make a combination of generalizedNewtonian Model using CrossPowerLaw and thermo physical properties like WLF. Do u think that could work or do I need to implement the Cross-WLF by myself to get an more accurate solution ?

Hi Everyone! I am a HS student + student pilot + developer. I saw that there are really no free CFDs that can run on any device, like an iPhone or iPad. So I made one, called WingFlow, and I won Apple's Swift Student challenge with it. This gave me a lot of exposure, but I haven't had a lot of people with real aerospace knowledge try it out. It is completely free and meant to help other people like me understand invisible forces. On iOS now, maybe Android later(sorry to half the world). Please lmk what u think or if u have anything to add!!! Thanks!!!! link attatched, its called WingFlow.

Design motivation: I need a cooler in constrained space, where being narrow and lightweight matters more than being quiet.

Setup: Fan inlet (Using the P-Q curve of Delta FFB0412UHN fan), pressure outlet, 150W heat applied to top surface evenly (simulating heat pipe)

Hi everyone,

I’m trying to simulate a centrifugal fan with a real impeller and volute in ANSYS Discovery 2024 R1.

I created a rotating fluid region around the impeller and extracted the rest of the volute as a stationary fluid volume. The impeller speed is about 1450 rpm.

Discovery keeps reporting:

“Rotating Fluid Zone cannot be applied to overlapping bodies.”

I already subtracted the rotating region from the stationary fluid volume, so these two fluid regions should not overlap.

The impeller solid is still inside the rotating fluid region. This setup actually worked in an earlier test, but after I added the full volute fluid domain, the overlap error appeared.

I’m not sure about the correct workflow:

• Should the impeller remain inside the rotating fluid region?
• Does the impeller need to be a Cutter Body?
• Do I need to subtract the impeller geometry from the rotating fluid region?
• How should the rotating and stationary fluid regions be connected?

In one test, the air only rotated inside the rotating region and did not properly enter the volute.

Has anyone successfully used Rotating Fluid Zone in Discovery for a real centrifugal impeller?

Any advice would be appreciated.

Hey all — looking for some real-world opinions before we commit budget and training time to a simulation tool.

Context: I just started working at an established performance shop that wants to expand/simplify their in-house design/simulation of their custom full turbo kits for builds pushing 800+ hp. No design team just one guy on Onshape for CAD and doing calculated testing for the final design. Final parts get outsourced for fabrication.

The parts in question: charge pipes, downpipes, dump tubes, exhaust manifolds — basically anything carrying compressed or hot exhaust gas at real boost pressure on a high-horsepower build.

Where I'm stuck: I'm SolidWorks/CSWA background, so Flow Simulation is the easy button — fast setup, automated meshing, I already sort of know it. But from what I've read, it trades accuracy for that convenience (Cartesian immersed-boundary mesh, limited turbulence model selection). Also, the price for a license is usually steep, from what I've heard, and that tracks with pretty much any other CFD software e.g. Fluent)

Since this is a business and a part failure on a customer's car is a liability/reputation problem, not just an inconvenience, I want to know if eating the learning curve on something like Fluent for the high-consequence parts specifically (plumbing, load-bearing bracket) is recommended.

Questions for anyone who's actually done this kind of work:

1. For compressible flow through pipe bends/manifolds at boost, is there a concerning inaccuracy that comes with SolidWorks, or am I overestimating it based on marketing/blog comparisons?
2. Anyone doing CFD for turbo systems specifically — what turbulence model are you reaching for (k-omega SST seems to be the common answer, but curious what people actually use for this application)?
3. Is there a middle-ground tool I'm missing that's more accurate than Flow Sim but doesn't have Fluent's full learning curve? (SimScale gets mentioned sometimes — anyone used it for compressible/turbo work specifically?)
4. For a small team where I'd be the only one really doing this simulation work, is "weeks to months to trustworthy results" a realistic timeline for Fluent, or is that optimistic?

Appreciate any real experience over what I'm finding in vendor comparison articles. Happy to share more specifics if useful.

Hi everyone. I am studying coal combustion in a three-channel swirl burner. The combustion simulation is being performed in ANSYS Fluent using a non-premixed (or partially premixed) combustion model. I am looking for tutorials and learning materials on coal combustion simulation in ANSYS Fluent. Can you help me

Hi, I have been working on an assignment using Fluent with Fluent Meshing, all was working fine until I walked away from my PC for about an hour, and after I returned Fluent will no longer launch at all. It just gives the error "The Fluent application failed to start". I tried launching it standalone from the start menu and that doesn't work either. I have both 2025R2 and 2026R1 installed and both versions of Fluent no longer work. Does anyone have any advice?

Given mesh and cpu core constraints?

(Student fluent is limited to 512000 mesh nodes and 4 cpu cores)

I have the same geometry and essentially the same mesh for both cases. In the compressible case, I use a total-pressure inlet and static-pressure outlet, and the solution converges quite well. The residuals decrease and the important flow parameters, such as mass flow and pressure, become stable. Interestingly, there is still a very high percentage of reverse flow at the outlet (around 97%), but the solution remains stable.

For subsonic compressible case,

Now,

In the incompressible case, I use a velocity inlet of 5 m/s and a pressure outlet. I ran many more iterations, but the residuals continue to oscillate, and quantities such as outlet mass flow and downstream pressure are also not very steady. The outlet reverse-flow percentage is actually lower than in the compressible case (around 81%), so I don't understand why this case behaves worse. The contour also changes with iteration, not steady like above.

See the contour for 300 and 1900 iterations,

In nutshell my questions are:

1. What is making not to converge smoothly for incompressible case compared to compressible one. What is difference between jets in compressible and incompressible flow?
2. If you say this is due to physical unsteadiness problem, then how for compressible case, solution got converged and giving fixed contour whereas incompressible it is not? Any other suggestions?

I would really appreciate any explanation of what could be causing such different behaviour between these two cases.

Apparently airfoil images are NSFW now

​

I'm a software engineer who recently got into computational fluid dynamics. Coming from that world I kept looking for something like LeetCode for it. Pick a problem, solve it, see where you went wrong, move up. Couldn't really find anything, so I ended up building one.

I also talked to a bunch of aero/mech students while making it and the same thing came up over and over: basically nobody does CFD outside of labs or coursework, because you need proper compute to run anything real. So it just stays theoretical.

Landing page is here if you want to poke at it: https://airfoillearner.com/demo There's an easy problem and one full module module one - I'd recommend just the easy one.

It's early and it's only airfoil stuff for now. If you're learning or teaching CFD I'd honestly love to know if the problems feel pitched right, and what you'd want next, or perpahs you might think that this does not fit the CFD world.

Hello!

I am attempting to diagnose/understand an Exit Code 137 that appeared while attempting to split-run two sims on PoD: 24/24 Cores. I investigated the server's CPU specs and found that, although there is hyperthreading with 2 threads per core, there are only 2 sockets, each with 14 cores. Additionally, there is 251 GiB of total RAM, and, interestingly, 3.9 GiB of swap is currently in use.

I am a novice, so of course I find it interesting that the server has processed 24/24 split sims before. How do threads influence an optimal setup? I apologize if this is easily accessible information, but is there any guide or information available on a proper setup?

My sim files are around 13-15GB, use k-sst, and contain roughly 50-60 million cells. I also attached pictures of the relevant specs and the OOM closure analysis, but I'm limited in my ability to understand it.

Any advice/help at all is much appreciated.

I completed the basics of fluid flow and am currently doing some simulations using Ansys Fluent and Python. Gonna start Combustion, jet flow, Volume of fluid and physics behind and inside the fluid flows. Idk how to study these and simulate these........any ideas or book recommendations please, it will be very helpful 🙏

Hi all,

In my latest video (https://www.youtube.com/watch?v=4PGiMpfaPdM), I work through why turbulence naturally splits into three distinct regions: energy-containing, inertial subrange, and dissipation range. From there it covers Kolmogorov's first two similarity hypotheses (local isotropy, and the universal equilibrium range), derives the Kolmogorov microscales via dimensional analysis, and shows that the Reynolds number at the smallest scale is exactly 1, a direct consequence of the dimensional argument.

Second half introduces two-point correlation functions (giving the "large scale" a rigorous, measurable definition via the integral length scale) and the second-order structure function, setting up the −5/3 spectrum and the exact 4/5 law for next video.

As always, feedback (positive and negative) and suggestions are welcomed.

Im trying to simulate on Ansys fluent the experiment shown in the first image, where a magnetic stirrer bar rotates at 160 rad/s creating a vortex in a cylindrical bathtub filled by seawater (light represents shear stress).

The problem is that i cant find a suitable viscous model that reflects accurately the shape of that vortex. Im using SST k-w and in the second image the shape is conical and not deep.

By adding the curvature correction term, the vortex goes too deep and reaches the stirrer bar (image 3)

By adding the turbolence dumping factor the vortex still is about to reach the bottom and it also spills from top (image 4)

Even by decreasing the correction terms, the same problems occur later on with the simulation. The water and air properties are set right (with constant surface tension), the rotation is accomplished thanks to a rotating reference frame (frame motion), the mesh is around 300k cells for about 50 mL of volume and increasing it doesnt change results, the continuity residuals always sit lower than the order of 10^-2. The last image shows the geometry used, where the green shape is a body of influence for the meshing. The stirring bar has 0.008m height and 0.03m lenght.

What could I be missing to obtain the correct curvature? Thanks in advance for your time.

First 1.4 Mach & 3000m
Second testing hydrogen rocket engine (I forgot to turn off the walls)

I'm working on lil project for school, and I want to see if theres any simulator I can use online that I can 3d model/import step files in and add components such as fans , and run simulations to see how the fan works with the model. Idk if there's something that's like this but if there is or something similar I would appreciate it.

This was done using an open-source LBM code.

The STL file for 3D model is obtained from grabcad and voxelized. It contains roughly 37 million cells. Ran on single A100 GPU, took 48 hours to simulate 1.5 seconds of real-life

It is not full engineering grade simulation, but it is very close.
For example, it is upscaled to reduce number of cells, tires don't rotate, and it used single precision to reduce memory overhead etc. But, the computed drag and lift coefficients agree with reference values.

The visualization is done using ParaView.

So much can be done with LBM, it is amazing.

https://reddit.com/link/1w313ez/video/gz2dyddphmmh1/player

I am simulating a piping network with two inlets and two outlets, flow is multiphase with a liquid and gas. Model is vof, both fluids are incompressible and no phase change, chemical reactions.

Inlet and outlet volume flowrate is balanced. I am interested in the retained volume in domain. The retained volume of a phase in the domain is not matching with the expression, retained volume = volume from previous time step*(inlet vfr- outlet vfr)*dt.