## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### CFD analysis of spacecraft re-entry phase

• Pierpaolo Viggiano
Subscriber
Hello,
I am a student new to using fluent.
The work I would like to do for my thesis concerns the re-entry phase of a spacecraft into the atmosphere of Jupiter.

Having defined the objective, and learnt how to import UDFs for the thermodynamic and transport properties of the atmosphere in question, I have come across some issues/doubts:

1.  Wanting to use a calculation domain like the one shown in the attached figure, how should I perform the named selection? On the web, I heard about the "far-field" boundary condition: is it possible to set all the outer sides of the geometry with this type? Without specifying inlet and outlet?

2. Having defined the basic model, is it possible to insert a source defined by an electric field on a surface? The surface in question would be the spacecraft's heat shield, which I decided to remove from the contour by means of a Boolean.

I hope I have made myself clear.
• Federico Alzamora Previtali
Subscriber

Yes, you can set all outer faces as Pressure Farfield boundary type, which is what I would recommend for this case. You can find an example from our Ansys Innovation Courses Airfoil Simulation Example | Ansys Courses

Regarding your second question, what type of source are you looking to define?

• Pierpaolo Viggiano
Subscriber
My idea is to set a source on the surface of the heat shields. The source generates heat through an electric field. Again, I would have to enter a UDS describing the trend in electrical conductivity.
The problem is that it seems to me that you can only set a source on a volume and not on a surface.

Is there a method for setting it on a surface?

In my case study I do not need the body of the spacecraft, so through a subtractive boolean I eliminate the volume of the spacecraft and therefore cannot apply the source as I would like.
• Surya Deb
Ansys Employee

Hello,

If I undertsand the issue properly, then there are 2 ways to model this.

1. Use Fluent's Electric Potential Model to provide the required boundary condition on the re-rentry vehicle. You might need good information on the electric potential boundary conditions. Also, there are limitations of this approach, specially if you are planning to use shell conduction.
2. The second approach can be to provide energy sources directly to cells neighboring the heated wall. It will be volumetric source term and you can use Cell register approach to mark the cells in and around the heated wall and then patch the source using the register. Alternatively, you can use UDF route by making use of connectivity macros.

I hope this helps.

Regards,

SD

• Pierpaolo Viggiano
Subscriber
Thank you very much for the alternatives shown to me. I will give it a try.

Are there any tutorials that explain how to use UDFs in this case?