Find answers, ask questions, and connect with our <br>community around the world.

Home Forums CFD foundation course: Forum External Aerodynamic simulation

• # External Aerodynamic simulation

Posted by on June 2, 2023 at 7:08 am

I wanted to generate freestream data for an external aerodynamic simulation to get values of forces and moments acting on a body.

In freestream analysis, there are lot many parameters like Angle of attack, angle of side slip, mach number, altitude, etc.,

By keeping a fixed Mach number & varying the angle of attack from small to higher AoA i will runÂ  (n) number of cases and will do the same for all other Mach numbers @ Sea level., where test cases will be around 100 or more.

By changing altitude the only aerodynamic force that will change is axial force coefficient (Ca)/ Drag force coefficient (Cd) remaining all other parameters will be the same (Cn, Cl, Cp center of pressure value, and Cm values)

My question here is, whether we need to run all test cases, at each n every altitude again n again?

Or is there any way to interpret the data from where I already ran cases at sea level condition !!!!

replied 10 months, 2 weeks ago 2 Members · 1 Reply
• ### Rahul

Member
June 8, 2023 at 6:34 am

Hi Anudeep,
From your question, what I understand is that you want to model external aerodynamics for a geometry at a specific Mach number, but different angle of attack and altitude. For cases having different angle of attack, you need to run separate cases. If the AoA is being implemented simply as a change in the inlet velocity direction, then you can use the converged solution of one AoA and use that as initial data for the next AoA by simply changing the boundary condition and running more iterations. This will provide faster convergence than initializing the case from the beginning. Same process is possible for Mach number too, provided the geometry and domain size remain same. If you are looking for an empirical relation to interpolate such data, please refer some literature for the same.

Also regarding the change in altitude, unless you are considering the difference in density or other properties of fluid, and the domain used for the sea level simulation can sufficiently resolve flow on all sides of the body, the results should not be the same at different altitudes.

Warm regards
Flowthermolab support team