Altair RISE

A program to recognize and reward our most engaged community members

Nominate Yourself Now!

How to view viscoelastic stress and shear rate?

Hello all,

I'm examining simulations of viscoelastic fluids with Acusolve 2017.1. When exporting the result files to EnSight to view them in Hyperview, I can't find the option to show the viscoelastic stresses, only the gradient. Also, I'd like to see the apparent fluid shear rate. How can one do this?

Find more posts tagged with

AcuSolve

English

Accepted answers

All comments

Rahul Rajan_21763

I see this results type is supported for Acusolve CFD reader in HyperView.PFA doc from online help.

I had to move post to the Acusolve forum for further support.

Unable to find an attachment - read this blog

Altair Forum User

Wonderful, thank you. However, the shear rate is not available with this option, either. Is there a possibility to view it?

Also, I meant to post the topic in the Hyperview subforum initially. But while we're here, I've got another question: I'm using Acusolve 2017.1 locally and Acusolve 14 on a cluster and I've noticed a strange behaviour with version 14. When using the Phan-Thien Tanner or Giesekus viscoelasticity model, the fluid viscosity sometimes stays constant although the models predict a shear thinning behaviour. I know that setting a viscoelastic model overrides the use of any viscosity option like Carreau or Power law and setting them doesn't change anything, so this is very odd. I haven't been able to pinpoint the exact reason. Any ideas?

Edit: Okay, I've found it. When using the AcuConsole GUI and defining a viscosity type like Carreau in the viscoelastic section of a fluid, it is not recognised! You have to set this in the viscosity section of the material, otherwise it is ignored. The same goes for the definition via inputfiles of course. Why is that?

Altair Forum User

Any ideas on how to view the shear rate?

I've got a few other questions as well. I'm trying to get a viscoelastic flow through a pipe to work. It's a highly viscous HDPE and I've got some trouble getting it to stabilize at high inflow pressure values (10 bar and above). The job aborts with the following error:

acuSolve: *** ASSERTION in Function <lesGmres> File <lesGmres.c> Line <1345>
acuSolve: *** Error from fLesGetHbrgEig <26>
acuRun: *** ERROR: error occurred executing acuSolve

It runs at lower pressures like 1 bar, but that won't suffice for my case. I tried raising the Krylov vector count and lowering the time step considerably, but no luck so far. The viscoelastic residual ratio starts at 0.9 and drops to 0.5 which isn't great, but the other residual ratios as well as the solution ratios are ok. So what exactly is the cause of this instability?

Following this, I wanted to stabilize it by using a multiplier function to raise the pressure or the inflow velocity linearly as I got the same *** ASSERTION error when trying to start a viscoelastic case using restart files from a purely viscous case. However, Acusolve does not seem to accept my implementation of a multiplier function. I attached the case - what's the error?

Unable to find an attachment - read this blog