Learning Forum

[youssefaider]

Hi, i am trying to do a shock tube problem in ansys aim, but i am struggling to set up two different fluid initial conditions ( high pressure and temperature in one side and low pressure Temperature in the other) i get only one option since i am working with one flow region, however when i try with two fluid regions i can still do two initial conditions but i don't get an option where to put each one. when i use the two flow regions i get no change in the results in all time frames.

[Sandeep Medikonda]

Hi,

I am not an expert in fluid simulations but this is what the manual says:

Initial Conditions for Fluid Flows

Before solving a steady-state fluid-flow simulation, an initial guess must be provided for the solution.The initial conditions will generally not affect the converged solution, but may affect the path to convergence. In some cases, a poor initial guess may lead to divergence during startup.

There may be situations where if the physics supports multiple solutions, the initial guess may affect which solution is obtained. For example, a converging-diverging nozzle may have purely supersonic or transonic flow with a shock; if the supersonic solution is desired, you should choose user-specified initial conditions which are supersonic throughout the geometry.

For time-dependent simulations, initialization provides the initial conditions for the simulation. If you are interested in how the transient flow field evolves from a known set of initial conditions, you must specify these initial conditions directly.

Initial Conditions for Time-Dependent Fluid Flows

Depending on what information you are looking for in the time-dependent simulation, initial conditions may need to be specifically provided. For instance, if you would like to capture startup transient behavior from known initial conditions, you need to specify those initial conditions. On the other hand, if you are interested in longer-term transient behavior such as resolving a periodic-in-time solution, then the initial conditions are less important. By default, ANSYS AIM assumes you are interested in the second type of simulation, and therefore applies Automatic initial conditions instead.

Also please see if the tips and tricks video below and this document help:

Regards,

Sandeep