HiSa Boundary Conditions

[ssiemons]

Hi People!

I am trying to understand how to set up an HiSa simulation for compressible internal flow. In this effort I have gone back to the most simple case I can imagine: laminar pipe flow. Unfortunately, I cannot get this converged.

I think the issue is with setting the correct boundary conditions. From my experience with commercial packages, I have learned that a mass flow inlet and static pressure outlet boundary condition is a valid combination for compressible flow. I've read that the massFlow BC in OpenFOAM is a wrapper around the velocity boundary condition, so this approach might not be suitable here(?).

Attached is my test simulation:
Steady State
Pipe, Length = 10m, Diameter = 1m.
Gas = Air (default)
Pressure Outlet BC, static pressure = 100 Pa
massFlowInlet, m_dot = 9.34e-6 kg/s.

This should result in Reynolds number of approximately 1.

Just Mesh and Run it, no further edits are required.


Now, I don't think the issue is with HiSa or the installation. Either way here my setup:

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.4 (GitTag)
Build type: Release
Branch: releases/FreeCAD-0-18
Hash: 980bf9060e28555fecd9e3462f68ca74007b70f8
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/Netherlands (en_NL)


The dependency checker is up-to-date (HiSa 1.1.4) and the tutorials from the HiSa source are all running. For those simulations a FreeStream BC was applied, but since I have internal flow I don't think this is applicable for me(?).

So my question is how to use HiSa together with FreeCAD? Should I avoid certain BCs? Should I edit files?

Sebastiaan

[thschrader]

... and the tutorials from the HiSa source are all running.
...

Hi, welcome to the forum.
How can I run the tutorial? lets say basic finner
https://hisa.gitlab.io/archive/asc/basi ... inner.html

Rebuilding with the cfdof-wb?

[ssiemons]

Hi!

I downloaded the tutorial files here:
https://gitlab.com/hisa/hisa/-/tree/master/tutorials

You can open the blueCFD terminal and execute the runSim file in the 'basicFinner/simulation' dir.

The basicFinner is rather expensive simulation in core and memory, maybe try the nacaAirfoil instead.

[ssiemons]

Have you been able to test your HiSa built against one of their tutorials/examples?

Sebastiaan

[Roland]

Hi ssiemons,

probably the basic question is whether HiSA is a suitable solver for internal compressible flow (piping, reactors, etc). I observe that all the examples provided by the developers are about flows that are external to bodies such as air foils.

Hopefully the developers can give a clue. Or perhaps other solvers would be recommendable?

Greetz,

Roland

[thschrader]

Have you been able to test your HiSa built against one of their tutorials/examples?

Sebastiaan

airfoil tutorial runs in bluecfd console. A RAM-friendly case
But how can I see the results in paraview?

hisa_airfoil.JPG (107.66 KiB) Viewed 2147 times

[ssiemons]

You should go one directory deeper to the simulation dir

[thschrader]

You should go one directory deeper to the simulation dir

Life can be so easy...

naca_high_mach.JPG (20.01 KiB) Viewed 2126 times

[oliveroxtoby]

Hi ssiemons,

probably the basic question is whether HiSA is a suitable solver for internal compressible flow (piping, reactors, etc). I observe that all the examples provided by the developers are about flows that are external to bodies such as air foils.

Hopefully the developers can give a clue. Or perhaps other solvers would be recommendable?

Greetz,

Roland

HiSA is a density-based solver, and as such suitable for the Mach number range of approximately 0.3 -> 5. If the majority of the flow is in that range, it shouldn't matter if you are looking at internal or external flow. That said, as you observe it has not been extensively tested with internal flow.

[oliveroxtoby]

So my question is how to use HiSa together with FreeCAD? Should I avoid certain BCs? Should I edit files?

Sebastiaan

If the Mach number is below 1 at the boundaries, any of the available boundary conditions should work. Otherwise, only the fixed velocity and fixed pressure inlet or ourlet is designed to account for a transonic situation (although they are not very well tested).

Sometimes it is a good idea to add a plenum chamber at a boundary so that a simpler, subsonic boundary condition can be used.