Problem with CFD analysis

EnDF

Hi everybody,

I’m new to AcuSolve. I have to do a CFD analisys of a chainsaw muffler, so I think that for most of you is a simple task. 

For this first time I worked following with video: 

 

beacause I think that this analysis is very similar to mine.

 

I also set the BL parameters ( first layer thickness, BL growth rate and number of layer) according to the video but I don't know how they should be inserted.

I exported the model from hypermesh to acuconsole, and in acuconsole i set the following parameters:

•             Analysis type: Steady State;

•             Flow equation: Navier Stokes;

•             Turbolence equation: Laminar; (If I set Spalart Almaras there is this error: ks+ is negative number, I tried to solve it but I'm not able)

•             Fluid: I created Nitrogen (with its density and viscosity)

•             Max time step= 1000;

•             Convergence tollerance =0.01 (looking at the residual ratio i’ve seen that it doesn’t fall under 0.1)

•             Inflow 'Simple Boundary Condition' , Mass Flux 0.0046 kg/s

 

The problem is that i get a wrong speed value ad you can see below.

 <?xml version="1.0" encoding="UTF-8"?>

 

In the outlet I set 0 n/m^2 for the pressure, because I want to reproduce the atmospheric pressure.

This is the first time that I do a cfd analysis and it’s problably completely wrong, so I would be really happy if you helped me.

 

I post the .hm and .acs files, thanks in advance

Best regards 

 

<?xml version="1.0" encoding="UTF-8"?>

Unable to find an attachment - read this blog

ydigit

There are two issues with your models. 

 

1. Scaling. If using acuConsole, you can scale your model by 0.001 in all directions, using Mesh Ops > Transform Coordinates. 

 

2. You are using mixed topology (Tri3 and Quad4 for Inlet) in AcuConsole for mass_flux inlet. This is not supported by AcuConsole (HyperMesh supports it though).

https://altairuniversity.com/6266-did-you-know-cfd-tips-tricks/

You have two options either to use pure Tri3 and Tetra4 mesh for entire domain or to use the BC type Constant velocity as stated in the link. The easiest would be to use split elements in AcuConsole.

 

Also HyperMesh supports mixed topology. So starting AcuSolve from HM should be OK (I did not check your HM file though). 

 

Hope this helps. 

ydigit

<?xml version="1.0" encoding="UTF-8"?>Result from the scaled model. 

EnDF

Hi ydigit, thanks for the response

 

How can I scale my model in AcuSolve instead?

EnDF

I have transformed it in this way

 

<?xml version="1.0" encoding="UTF-8"?>

ydigit

Altair Forum User said:

Hi ydigit, thanks for the response

 

How can I scale my model in AcuSolve instead?

 

The screenshot for scaling was from AcuConsole. As you uploaded ACS file I assumed that you are using AcuConsole.

 

You can also scale in HyperMesh using Mesh > Scale > Components 

EnDF

thanks for the response

best regards

 

simone