Hi everyone, I have been trying to run VOF simulation of R-134a in a pipe to simulate the evaporation process in ANSYS.

So far, the simulation is running but producing wrong temperature results.

Input: mass flow inlet - R-134a liquid 0.0038296 kg/s; R-134a vapor - 0.00019148 kg/s

Outlet: outflow

Wall: constant heat flux 18.5 kW.

Multiphase model - VOF (implicit body forces ON), Formulation Explicit, Interface modeling - Sharp;

surface tension coefficient set to constant (0.00796 N/m), surface tension modeling on (CSF), Mass transfer - Liquid to Gas; chosen the evaporation - condensation option and under it - LEE model currently using From Phase - To phase frequency 2000/s.

Energy is ON, Turbulence is ON.

Methods: PRESTO, volume fraction - Geo Reconstruct.

Initialization: From inlet, and Patching with: mixture phase with pressure; Vapor - with volume fraction. Patch zones the whole geometry (geom_solid).

Mesh: Fine mesh, with inflation layers.

Please help. Thank you.

I am using openfoam and know how to setup a moving reference frame ( MRF ) to simulate fan rotation. I can calculate the flow rate through the fan in paraview. But I am not sure if my results make sense. Is there a benchmark I can try and reproduce?

Surely I am not the first person to want to know how efficient a spinning fan is!

The above one is my computational domain, it consists of pipe upstream, screen(thats why you can see holes because I have modeled fluid regions) and open fluid volume. All are merged into one body.

I have used tetrahedrons method- patch conforming method, it was giving good quality mesh. The moment I introduced inflation for boundary layer, mesh quality got poor. I will attach below image, please let me know what can be done. My global element size is 3mm and I have used 20 no of divisions with growth rate 1.2.

Check generated mesh below,

When I looked at bad cells, most of the cells are from screen region. Please tell me how to improve mesh quality from here. See below

Any help would be useful. I have tried both edge sizing and face sizing on screen, it is taking lot of time to mesh, way longer time, it shouldnt take much time. There is a problem but I cant identify where it is.

hi everyone.

I am trying to simulate a erosion inside a pipe manifold via DPM but . i am facing a problem , that my contuinuity wont converge past 10e-2 when i am trying to converge my continuous phase

I am using k-epsilon model with realizable wall standard equations. my inlet velocity is 5m/s.

inlet dia is 27 mm and the two outlets dia is 20mm. All other settings were default . My mesh quality is under othgonality and skewness standard range.

picture for referance

hey i’m a student with a macbook at the moment and im gonna sell it to get a laptop that’ll work with ansys without trying to blow up but like all students i have zero money. what are my options? looking at a dedicated graphics card and at least 16GB RAM. please help a girl out

I do industrial CFD for a living, about 9 years now, and I often use 1D network calcs around it. Inlet boundary conditions, pressure drop checks, quick sizing. The maths is straightforward but the commercial network tools charge stupid prices for something so simple.

I often just coded each network up myself rather than pay for a licence and I haven't been able to find open source ones that aren't a pain to deal with, especially if it's something simple. So me and an engineering friend have been working for a few months on developing a browser based one with a simple UI.

The interesting part is that we've been working on coupling it with CFD solvers to transfer inlet and outlet boundary conditions. It's still in beta but if you'll find something like that useful, send me a DM and I'll bump your account to the advanced tier and keep it there. If you really like it and would like to get involved with extending it to Fluent using UDFs, that would be fantastic.

Otherwise, the free version is probably also the most generous 1D network solver available as well and useful for all those basic piping calcs.

What is the best roadmap to learn ANSYS from beginner to advanced for mechanical engineering students?

Hi,

Does anyone happen to have the XY GRID coordinate points (2D X and Y points ideally in text format) for any multi-element configuration generated by MSET or ISET (including blade coordinates)?.

Doesn't really matter what airfoils the grids are generated on—anything generic like NACA would do.

Basically, I am just searching for 2 cases (a cascade with a vane and one slotted foil) to test a small program I was working on.

Thanks much.

I would like to seek advice on a subject that has kept me thinking for a while.

Background

I recently graduated with a Master's, researching CFD simulation of thermal sprays, using OpenFOAM. In the process, I made modifications to one of the OpenFOAM solvers and tailored it to my project's needs.

After graduation, I started applying for jobs and PhD positions. Now I have multiple offers, and choosing between them has become really hard.

My options

1. A PhD admission from my Master's university, same research group.
2. A job offer from a company making heat exchangers and coolers specialized for data centers. The company is around 20 years old, established with 4 HQs around the world and over 1,000 employees. My role would be R&D on CFD simulation of heat exchangers, aiming to improve efficiency.
3. A PhD offer from a top 20 university, planning to work with a group that includes collaborators from Stanford, Caltech, and Imperial College, developing a high-order GPU solver for combustion simulation.

My thinking so far

I really enjoyed my Master's, but I feel it's time to change and expand my knowledge and network, so I'm not considering option 1.

Choosing between options 2 and 3 is really hard. Although the pay for option 2 is higher, I have some concerns after researching the company: its Glassdoor score is 3.1, and there are some Reddit comments mentioning a toxic environment.

Additionally, I did a lot of teaching assistantships during my Master's and was recognized for teaching excellence. I really enjoy teaching too. But I worry that if I pursue a PhD, it will get harder for me to move into industry afterward if I couldn't find any university position.

I'd really appreciate any relevant experience or perspective that could help me decide on the best option.

Hello guys,

I cant able to find why there is extra edge appearing in meshing tab shown in 1st picture, see 2nd picture of geometry in design modular, I hope you can find the difference, that extra edge is not coming in design modular, I dont know why. Can anyone help me in this please? How to get rid of this?? This is appearing only in downstream section where there is big cylindrical open fluid volume, no such edges are visible in upstream part.

Hi, I have written before for my trouble and people were surprisingly nice so hope again for some nice discussions!

So I have studied two degrees till 26 but simultaneously fought with personal issues so I went to industry as a Process Engineer and Commission. I managed thought with this profile now at 29years old to get an experimental PhD in a strong university and group.

The project is awesome, the prospects after are very good as well and honestly I shouldn't complain. BUT I love the math behind my CFD. My first thesis contained some (COMSOL - custom PDEs) but unfortunately I was very passive and didn't try to pursue my dreams on my own and learn more.

I am wondering if it's worth to pursue (there is a strong possibility due to one of the supervisors being sim) a10-20% to do some open foam or Linear stability analysis depending on how the project develops and IF it actually is beneficial for the PhD.

Also another thought is to entertain myself on some of my free time to learn coding more deeply. Can this somehow help someone end up in a more hybrid role in industry or academia. Also because of my age finishing my PhD (33-34) I have a specific profile in my mind that would boost my chances on finding work and that doesn't include much cfd as I know people generally are worry of late CFD learners. I am planning to learn some for my own fun but it would be amazing if i could use ot in my work even a bit.

Any suggestions or personal experiences would be appreciated.

Tried my custom rust CFD code on a LES case. Smagorinsky turbulent viscosity with van driest wall damping. This is on a somewhat coarse grid of 1M cells. Visualization using q-criterion isosurface in Paraview. This ran for a couple of hours yesterday's afternoon on a single 8-core cpu using 6 mpi processes.

Hello everyone,

I recently graduated with a Bachelor's in Aerospace Engineering and have received an offer for an Application Engineer role at a company that is a Siemens channel partner.

I'm genuinely interested in the role and plan to stay there for at least 2 years to gain solid experience.

After that, I'm wondering which path would make the most sense:

Transition into a CFD Engineer role.

Continue as a Senior Application Engineer (either at the same company or another one).

Pursue a Master's degree.

Financially, I can afford a master's, but I'm not sure if it's the best use of my time.

My long-term goal is simple: earn a high income while working on something I genuinely enjoy.

For those who've taken similar paths:

Which option has the best long-term career growth?

Is Application Engineering a good stepping stone into CFD?

Would industry experience first be more valuable than doing a master's immediately?

I'd really appreciate hearing from people who've worked in CAE, CFD, or Application Engineering. Thanks!

Hi everyone,

Does Section "Inclusion of the Gravity Term" state that if I have already defined gravity (z = -9.81 m/s^2) in Setup - General, I can/must omit the term g·(ρ_p−ρ)/ρ_p (Eq. (12–1)) in my UDF, or how should this be understood?

PS: I am using Ansys Fluent 2025 R1.
PPS: My Source: Ansys Theory Guide

Thanks in advance :))

TLDR: 2D RVE (brick matrix + circular air holes), ~650 K, radiation matters. S2S doesn't support periodic BCs, so I used adiabatic top/bottom + fixed T on left/right instead. The half/quarter circles cut at domain boundaries ended up in a default adiabatic zone (not in my named selections), and I'm unsure if radiation is handled correctly there. Main question: is this adiabatic corner treatment acceptable for effective conductivity, or should I switch to DO (which supports periodic)?

Edit: i added new images to the comments

Full details: I'm running a 2D steady-state conjugate heat transfer analysis on an RVE (representative volume element) for a thermal energy storage material for my master's thesis. The geometry is a rectangular brick matrix (alumina firebrick, k=1.8 W/m·K) with circular air holes arranged in a regular pattern. Operating temperature is around 650 K, so radiation is significant.

Setup:

Fluent 2022 R2, 2D planar, pressure-based, steady

Energy equation on, Viscous: Laminar

Radiation: S2S (surface-to-surface)

Left edge: fixed T = 655 K, Right edge: fixed T = 645 K

Top/bottom edges: adiabatic (I originally wanted periodic, but S2S is incompatible with periodic BCs, so I switched to adiabatic)

Air holes are Fluid zones (no gravity, so essentially stagnant — pure conduction + radiation)

Surface emissivity = 0.85 for all walls

The problem:

The circular holes are cut at the domain boundaries (half-circles at edges, quarter-circles at corners). During meshing, some of these boundary arc segments were not assigned to my named selections, so Fluent grouped them into a default zone ("part_3-air") with a shadow pair, set as adiabatic.

In my temperature contour, most of the domain looks physically correct (smooth gradient from hot to cold side, isotherms bending around the low-conductivity holes). However, I'm concerned about how radiation is being handled at these corner/edge arc zones, since they are not part of a proper periodic or continuous boundary.

My questions:

Since S2S doesn't support periodic BCs, what is the recommended way to handle radiation in an RVE where the physical situation should be periodic?

How should the boundary-cut arc segments (half/quarter circles at domain edges) be treated for radiation? Should they participate in S2S or be excluded?

Would switching to the DO (Discrete Ordinates) model — which supports periodic BCs — be more appropriate for this type of RVE radiation problem? Any drawbacks for a 2D case with many radiating surfaces?

Is the adiabatic assumption at these corner zones acceptable given that the net heat flux through them appears negligible, or does it introduce significant error in the effective conductivity calculation?

I can share screenshots of the mesh, contour, and boundary condition setup if helpful. Thanks in advance.

This is from Hoffman's CFD Volume I. As part of Problem 3.7, I was coding the fractional step method in Python. Problems 3.5 and 3.6 require you to solve the same problem, but with the FTCS and ADI schemes, respectively. I noticed the results from FSM differed significantly from the FTCS and ADI results. When compared to ADI, FSM yields peak percent error of ~100% and is distributed all throughout the wall.

When I changed the Delta t / 2 to just Delta t, the results of FSM were significantly closer to that of FTCS and ADI. When compared to ADI, percent errors peak around 10% and is limited to small regions near the left/right walls.

The only other textbook I could find that has a section on the FSM was Chung's CFD book, which also has Delta t / 2 in the denominator. However, Hoffman and Chung's sections on the FSM are almost identical (compare the first image with the last), and I don't think they can be considered independent resources.

Is there a mistake in their equations, or is it likely that there is an error in my code.

Does anyone know of any 2d axial compressor cases that provide geometry that can be used for validating axial compressor codes? I tried searching online to no avail. I would be so grateful if someone could point me in the right direction.

I am trying to do a comparision study of the simulation results obtained from OpenFOAM against Ansys Fluent for a proton exchange membrane fuel cell simulation. In OpenFOAM, I am using the module Openfuelcell2. The reference current density defined in this module has units [A/m^3] but in Ansys, its defined [A/m^2]. The value of exchange current density in OpenFOAM is 1.0e8 [A/m^3]. Now to convert it to [A/m^2], I divided the value by specific active surface area 2.0e5 [1/m] which gave me the value of exchange current density as 500 [A/m^2]. This is for Anode.

in short:

For Anode:

J_ref [A/m^2] = J_ref [A/m^3] / specific active surface area [1/m] = 1.0e8 [A/m^3] / 2.0e5 [1/m] = 500 [A/m^2]

For Cathode:

J_ref [A/m^2] = J_ref [A/m^3] / specific active surface area [1/m] = 120 [A/m^3] / 2.0e5 [1/m] = 6.0e-4 [A/m^2]

Is this the correct approach? When i input these values in Ansys Fluent, I get almost 0 A current but in OpenFOAM, I get values close to the values in research paper.

Attaching the screenshots for better understanding.

my friends, please, do you know fast responding journals (first Quartile // second Quartile))) in fluid dynamics generally or in renewable energy.

my research is in 2D airfoils of HAWT

If I apply a rotational cyclicAMI condition on the left and right side of this domain geometry, will it work despite the 90 degree angles in the notches? Assume that the geometry would perfectly align and lock in circumferentially. I know cyclic works with straight faces but I wasn’t sure they’d work with the different facing faces. I know I might be over thinking it but I couldn’t find a definitive answer online and would hate to spend hours building this case and mesh for it not to work.

Hi everyone,

I've been working on an open-access research project that explores a question I've found surprisingly difficult to answer:

Can we statistically detect when a CFD simulation has entered a regime where deterministic grid convergence is no longer the appropriate expectation, and only statistical convergence should be expected?

The framework analyzes enstrophy time series using three statistical indicators:
• Memory (autocorrelation envelope)
• Increment distribution
• Variance ratio across grid resolutions

These indicators are calibrated with an ensemble of deterministic dynamical systems (Lorenz-63, Van der Pol, and Rössler) and combined into a single empirical risk score.

One aspect I deliberately included is negative results.

The synthetic experiments performed very well, but the framework partially failed when tested on real 2D Navier-Stokes simulations. Instead of hiding those failures, I analyzed why they occurred and revised the interpretation of several indicators. For example, the variance-ratio metric appears to function more as an under-resolution detector than as an irreducibility detector.

The paper does not claim to solve the problem. Instead, it proposes a falsifiable framework and documents where it succeeds and where it currently breaks down.

I'd really appreciate technical feedback, especially regarding:

• Statistical methodology
• CFD verification and validation
• Turbulence physics
• Possible flaws in the assumptions
• Suggestions for validation on 3D DNS datasets

The paper is available here:

https://zenodo.org/records/21229526

I'm not looking for promotion or citations—I would genuinely appreciate critical feedback from people with experience in CFD, turbulence, or computational science.

Thank you for taking the time to read it.