Learning Forum

[sharm2a2]

Hello everyone,

What is the difference between pseudo transient simulation and transient simulation?

When to use pseudo transient ? I know about the transient simulation but pseudo is bit confusing. If we want to run pseudo we have to run as a steady which confuses me as since it is steady state than why transient in it.

Please help. 

 

Thanks

[Keyur Kanade]

Hi, 

Pseudo transient  is a form of implicit under-relaxation for steady-state cases. It helps in stabilizing the case and at the same time gives faster convergence. Please see help manual for more information. 

Regards,

Keyur

[Keyur Kanade]

Moving to fluid dynamics category. 

Regards,

Keyur

[seeta gunti]

Given more information from the document. 

 

For the set up,  you can go through  our user guide section 28.13.

 

Regards,

Seeta

[denispansolin]

Hi guys,

I am doing a simulation with Turbulent and compressible Hydrogen (Internal Flow) in 3-Dimensions.  I m doing it using Pseudo Transient Time. My residual after 200 iterations becomes flat. Is that normal? When I run it steady state ( no Pseudo Transient) the iterations go up and down forever. Can someone explain to me why in pseudo transient they become flat so soon?? 

Thank you for your help !!!!

 

[Brett D]

Hey guys,

 

let's say we look at the transport equation, if it's a steady problem we can eliminate the term with time in it, so d.phi/dt for example. However if we then proceed to solving with the jacobi or gaussian method then we will likely experience instabilities. To help this we keep the transient term but phrase it as a relaxation term and keep everything else the same (such as the value at boundary nodes) because it's a steady state solution.

 

Is this more or less what the pseudo transient method does? I've had a hard time pinning down what's actually happening numerically.