Hello guys,
i have been performing CFD on a plane.Recently i came across Y+ as a metric of accuracy for the CFD analysis.My questions are as follows:
1)Do different models require different range of Y+ value to be validated?If so what is the range for K-omega model? is it between 1 and 5 as given in the links (would'nt the inflation layers be too small for generic laptops to mesh?)

2)Since it is a personal project(plane cfd).How do i get the reference of the entire body?My friend told me to perform CFD at a very fine mesh so that the results are as close to accurate and then use it as the reference to perform mesh independence study.

3. Is Y+ used for actual mesh independance study?Can i Do a mesh study by randomly selecting a low computational cost model like spalart alarmas(1eqn) and check for acceptable drag variation.

4)Is performing a Y+ check neccesary at RC scale? my reynolds number is around 320579, density = 1.162 kg/m3, MAC = 0.283m, cruise velocity 18m/s.

5. also since i am doing 3d analysis should i check my Y+ spanwise or cord wise for validation?Also very importantly how do i include inflation layers in my geometry?Can you guys please suggest me a playlist on how to be able to mesh entire aircraft geometries instead of single components like wing-tail geometries.

These are the recent websites and video links that i have visted to learn about Y+:
1)https://www.researchgate.net/post/How_use_y_plus_value_with_different_types_of_turbulence_models_in_cfd
2)https://www.cfd-online.com/Forums/main/214353-y-plus-2d-vs-3d-does-matter.html#post723186

3)https://www.cfd-online.com/Forums/fluent/242527-y-range-different-turbulence-models-wall-functions.html

4)https://www.youtube.com/watch?v=60fDz2cVdy8

My second question is that at high angles of attack around 16 deg my simulation plots starts to oscillate.Is it because the solution might be transient?If so can i average the oscilations and take the values or should i perform a transient simulation?

thank you for your time and valuble insights.Have a nice day.

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I am in the middle of a PFE internship in CAE NVH scope I have prerequisites for the theoretical (MEF, NVH, crash, reliability....) but unfortunately I have no experience in software practice CAE and for my internship the company gave us training for the ANSA software (mesh assembly cleaning) in your opinion how I can master the simulation software is repeating the exercises enough thank you for your response

I am currently doing a propeller analysis in fluent the velocity i want to test is at around 16 m/s . But the fluent is showing floating point error every time i try to increase the magnitude

After I run a successful simulation, I go back into setup and edit the gauge pressure slightly. It now won't get past the first few iterations without getting the floating point exception #f error.

I have previously run at both pressures I am alternating between, but now the setup won't work. My mesh is fine. What else could be the issue?

OpenFOAM in Windows Subsystem for Linux (WSL) - Updated version

Code named WSL-SUSEFoam2023v1

http://www.wolfdynamics.com/tools.html?id=186

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If you are a Windows user, and new to Linux and OpenFOAM, and if you do not want to go thru the hustle and bustle of partitioning your hard drive, backing-up your data, and installing Linux and OpenFOAM, we highly recommend use Windows Subsystem for Linux (WSL).

The Windows Subsystem for Linux (WSL) is a feature of the Windows operating system that enables you to run a Linux file system, along with Linux command-line tools and GUI apps, directly on Windows, alongside your traditional Windows desktop and apps.

WSL requires fewer resources (CPU, memory, and storage) than a full virtual machine. WSL also allows you to run Linux command-line tools and apps alongside your Windows command-line, desktop and store apps, and to access your Windows files from within Linux. This enables you to use Windows apps and Linux command-line tools on the same set of files if you wish.

This WSL distribution is based on OpenSUSE 15.5 and comes with OpenFOAM 10, OpenFOAM 11, OpenFOAM v2312, paraview, and DAKOTA 6.19 pre-installed. It also comes with all the compilers and libraries necessary to compile most of the applications.

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#CFD #OpenFOAM

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👉Follow us on YouTube: https://www.youtube.com/channel/UCNNBm3KxVS1rGeCVUU1p61g

OpenFOAM 11 in a Linux virtual machine - Updated version

http://www.wolfdynamics.com/tools.html?id=190

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If you are new to Linux and OpenFOAM, and if you do not want to go thru the hustle and bustle of partitioning your hard drive, backing-up your data, and installing Linux and OpenFOAM, we highly recommend you use this Linux virtual machine based on OpenSUSE 15.4.

You can install this Linux virtual machine under Windows, MacOS, and Linux (yes, you can install a Linux virtual machine in Linux). To do so, we highly recommend using VMWare Workstation player (for Windows or Linux), or VMware Fusion (for MacOS). Both versions are free for non-commercial personal use.

This virtual machine comes with OpenFOAM 10, OpenFOAM 11 and OpenFOAM v2312 pre-installed, plus a few additional applications for visualization, optimization, and data analysis. It also comes with all the compilers and libraries necessary to compile most of the applications.

#CFD #OpenFOAM

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👉Follow us on YouTube: https://www.youtube.com/channel/UCNNBm3KxVS1rGeCVUU1p61g

I've been trying to export the CAE to use with OpenFOAM but I keep getting the same message "The location selected is not writable" with any folder I use. I've looked everywhere and can't find a solution. Does anyone know why this happens or a solution?

Any help would be much appreciated. I have simulated the hydrodynamics responses for a cubic shape body in Ansys Aqwa. The cube has free to move object inside it (under gravity). Rigid dynamics performs well when I apply the gravity with fixed support, but I am unable to find any way to see the wave motion effects in rigid body motion. Is there any way I can load the motion data from the Aqwa and see same motion in Rigid body dynamics affecting the motion of free object inside it?

Thank you again.

What is the difference between steady and transient solver?

So iam super new to CFD and Ansys fluent, I am doing a simulation of heat sink under forced convection. So when I alter the size of fluid domain [box] the dissipation rate changes . Can anyone please clarify why is that ?

Edit : I have given velocity inlet and outflow conditions

I have a wavy finned heat exchanger to be studied. I tried to use flat fins for ease of simulation but still the model is heavy due the amount of fins I'm using an linear array twice for creating single group of 32 and arraying the group by 6 times again

I am searching for a job within the CFD industry in Sweden.

I came across people saying, "Pitch yourself". I have been thinking about it and speaking with people.

Certain aspects are very common among all the applicants—extensive CFD experience, teamwork, stellar communicative skills, etc. I find that problem-solving for the team is something they are looking for, but this seems common among applications.

In this subreddit, I suppose there are hiring managers or people who got hired using a great "pitch yourself" strategy. If you have heard of it or if you have used it, please mention it, and I could learn from it and try to use it.

Thanks!

Hi! I am a beginner at ANSYS Fluent and I was trying to simulate a rotary lobe pump for a school project but I don't know how to make the lobes rotate. I have seen tutorials about these two but don't know the difference between them. So far, I have tried simulating the pump I made in Fusion 360 in a steady-state using frame motion while the region around the lobes have angular velocity instead of the lobes themselves.

Hi,

I am trying to make a rigid wall move in a particular way.
I have the following udf:

#include "udf.h"

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DEFINE_CG_MOTION(moving_wall, dt, vel, omega, time, dtime)

{

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`real t = CURRENT_TIME;`

`NV_S(vel, =, 0.0);`

`vel[0] = 0.00016 * 3.1415 * 20 * cos(10*3.1415 * t + 3.1415/2);`

​

}

I want to realize the following motion:

1. Displacement for a certain value of distance from point A to point B
2. No Motion for a certain amount of time at point B
3. Displacement from point B back to point A

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My knowledge in C programming is very poor, so I have no idea how the code which provides this motion behaviour should look like. Can anyone help me with this?

Thanks in advance!

Can anyone explain in detail about the negative cell volume problem in dynamic meshing? I know that it is caused by having moved the mesh too far in a single time step but what are other things that factor in this(time step size, velocity, no of iterations/time step?).

I'm trying to use the Boussinesq equation (see image) in ANSYS Fluent to output the uv Reynolds Stress tensor. However, I am having difficulty with writing it in the user defined functions command window. I found some folks on the CFD forums talking about it but they way they descibe implementing it does not seem right. Hoping someone here might be able to help a newbie. Thanks!

Hi, so I’m working on a project at uni and I need to analyse external flows I have images for the contours, directional field and path lines. Can anyone help me with starters for how I’d analyse these any links would be helpful as well

Hi, so I’m performing a simulation on an underwater drone and I wanted to create a report definition for the drag force and drag coefficient. I was researching different enclosure sizes as I saw this was impacting the results and I was curious what you guys would recommend for ratios. The front face is the inlet and the back face is the outlet. The other question I have is when I select what regions to include for the report definition I noticed there is a shadow region, and after looking it up online my understanding is that it is the interface between the fluid and solid regions. Should I select just this region when I’m trying to get the drag force or all 3 (enclosure-fluid, shadow region, and drone-solid). Thank you for your time.

Hi there,

I am new to CFD and ANSYS Fluent. I am trying to model a 2D periodic system. I plan on using MATLAB for the data analysis, so I am doing this by doing file->export->solution data. I am trying to look at the static pressure at the walls throughout the period. In the solution data, there is a data column for 'Static Pressure' and a column for 'Periodic Static Pressure' and they produce different results. I was wondering if someone could explain what the difference is between them and which one I should use for my application. Also, if you could point me in the direction of a help page that explains what all of the data exports reoresent in more detail, that would be great.

Hi, I’m about to finish my Master in Northern Europe and want to continue with a PhD in LES turbulence modelling.

I would like to know whether it is worth possessing a PhD in CFD, especially for development. In some EU countries, such as where I’m from, having a PhD is almost an obstacle rather than a perk. In general (at least in your country), are salaries for mechanical engineers with a PhD actually higher than those of a Master graduate with four years experience? Is it harder to find a job? I had an internship this summer and almost everyone in my department had a PhD.

Note that I’m not questioning my motivation: I’m convinced I want to do a PhD. I’m just evaluating what may happen next, since I still don’t know whether I’ll transition to the industry afterwards. Thanks!

Hey all,

This is quite a general post and I’ll be happy to provide some more details while we discuss it but as a general question, do you have any tips about modelling porous domains? I’m trying to do it and I really think my problem is quite easy. Its just two domains side by side where one of them is porous and the other isn’t. So, the liquid flows from the non-porous domain to the porous domain and I have two source terms a negative to the liquid and a positive to the gas.

But, I am not entirely sure why, everything goes wrong, the simulation converges but with reverse flow at the outlet and although it’s converged is wrong.

How should I proceed? I feel like I have no control on what is going on.

https://preview.redd.it/1t6r14z07vtc1.png?width=1287&format=png&auto=webp&s=57517038b3807661206fbbbc061d20ef229a05b0

Hi guys ,

I'm interested in understanding the current job prospects for CFD engineers in India. I've been working as a CFD engineer for two years, specializing in ANSYS products like CFX and Fluent. I'm curious about how to distinguish myself in this field. Are there any emerging technologies or products I should focus on to improve my skills?

Thanks

Hi I am New to CFD and I am working with comsol multiphysics 6.2. I have a copper Part with multiple channels. This copper Part is heated by a heat flux. The Fluid that is pumped through these channels is cryogenic and will likely evaporate. How do I tell the Programm that the Fluid will evaporate? I know there is a multiphase tab but I dont understand what exactly I have to click or define, so that it works. I had a lot of trouble testing it and failing, as well as looking for good documentation. My Part is a 3d part.

If i wanted to do a simulation on a pump should I put rotating cell zone only or do i put motion on the cell zones such as the blade and the pump? i ran one where i rotated cell zone only and it looked like someof the streamlines got stuck on the blade help would be appreciated

https://preview.redd.it/dh4sglworttc1.png?width=1210&format=png&auto=webp&s=76f66a001c3d209cdc1dbedfb2e94b77b091511a

Hi, I am a novice for CFD, There is a mesh problem that puzzles me, I know size of a object, then how do i estimate the initial mesh size ?

Thanks!

I have an automotive background, and I need to get into ANSYS Fluent and CFD. I just don't know whether I should start learning the software. I need some guidance to start my career in this field as I have no idea where to begin.

1. Is it a good choice to pursue a career path in CFD?
2. What are the basics I need to be strong in?

I'm learning flow simulation, and I'm a little confused as to what's happening here. I have flow trajectories going into this 1" thick bellmouth, but one seems to just pass through the solid part and creates a vortex on the backside of it (ignore the greenish lines, those are just visual and are actually inside the bellmouth). There is no actual hole there where it passes through the solid model.

Is there a way to just disable this one streamline so that the vortex doesn't appear in my results?

https://preview.redd.it/l0ey8ybw7ptc1.png?width=675&format=png&auto=webp&s=4d99c4b65c647c9eb7079418c65553f2a264e9c8

So I'm conducting experiments using the same mesh for standard, RNG and realizable k-epsilon models. I did mesh independence test for standard k-epsilon. Do I need to do it again with the other models since they predict slightly different results?

Short form:

Any recommendations for literature that guides me in the simulation of a aircraft (ideally antique aircraft)? Especially in regards to Meshing, solvers, initial conditions etc.

The whole text:

Hello dear CFD community,

So I have just started my bachelor's work which to a larg part is about the numerical simulation and analysis of the condor Nr. 21 using star ccm+.

Unfortunately I am not that well versed in computational fluid dynamics of aircrafts. I have a very basic understanding of the topic and the program from my one semester of flow simulation. Therefore I am looking for literature that ideally guides me in the process of simulating the flight of aircrafts in general or ideally old aircrafts. Especially the Meshing, the types of solvers, initial conditions an all those other important parameters.

Sadly I am having a very hard time finding anything fitting. Most literature is either about very specific topics, and not so much a board guide about aircraft modeling and simulation. The books in my university focus on flow simulation/ mechanic as a whole for the most part and are not specific to aircrafts or are from the early 2000.

So are there any aerodynamik enthusiast that can recommend some literature? Anything is welcome, but ideally freely accessible. I my have to option that my university orders a book too, but thats not certain.

I thank you for your help in advance.