Learning Forum

[GuillaumeCRENN]

Hello,

I am trying to simulate the heat transfer of a Rover at 2m from ground on Titan, Saturne's moon.

[Rob]

Rather than using a species model I'd just work out the density & viscosity at the relevant pressure & temperature and input that as a single species. Unless the atmospheric composition is changing you're wasting cpu time solving species equations for no reason.
To set pressures etc elsewhere, you want Patch. To set the materials by zone, you do this via the Cell Zone condition so need the two (or more) zones to have recognisable labels (Named Selections). The mesh sections don't appear to be connected, is this intentional?

[GuillaumeCRENN]

Hi Rob Alright, I take your idea for the atmosphere and will apply it.
To set a constant pressure for the internal fluid domain I used the Patch tool. But it did not work. The pressure is still 0Pa while I set 101 325Pa. I don't understand why. Do you have an idea ? I can set the materials for every part but this pressure does not settle.
Yes, the mesh sections don't appear conformal, as a speed preliminary geometry, my mesh was not-conformal but I changed it into a conformal one (sections connected).
Best

[Rob]

You initialise the system and then patch the pressure etc. Not sure why it's not sticking unless you're then initialising the system again or haven't separated the fluid zone labels out.

[GuillaumeCRENN]

I did that and the pressure is still at 0 Pa. To me, I correctly named the different fluid and solid zones.

[Rob]

Can you post images?

[GuillaumeCRENN]

For the geometry, I used a conformal mesh (1 piece)
These are the solids and faces named.
I used a pressure-based, steady state simulation. Turbulence model : k-omega SST, energy : ON. I initialized then patch the internal fluid domain with a pressure at 101 325Pa (external pressure 1.5 bars) and I put an inlet wind at 10m/s.
This is the result of the pressure.

[Rob]

Can you post a screen grab of the initialisation and patch settings? What's the operating pressure set as?

[GuillaumeCRENN]

When I Patch the zone, nothing appears into the command pad, after "Hybrid initialization is done". I also tried with Operating pressure : 101 325 Pa. The result remains the same.

[GuillaumeCRENN]

I found my mistake ! I was plotting the static pressure but I should have plotted the Absolute Pressure contours ! By changing the operating pressure, the Patch pressure and the Pressure-Outlet BC, I noticed I need to be careful to obtain the right pressures inside and outside.
Thank you for your precious help!! Now I solved this issue, I will work on your idea for the Titan's atmosphere.