Rocket Aerodynamics Workflow

This example shows a plain workflow for taking a model rocket from initial geometry to aerodynamic results using OpenVSP and Stallion 3D.

Overview

OpenVSP is used to build the rocket geometry. The example rocket includes a smooth nose cone, a cylindrical body, and four caned fins for stability. After the geometry is complete, it is exported as an STL file and imported into Stallion 3D for CFD analysis.

Step 1. Create the rocket geometry

Start in OpenVSP and define the main parts of the rocket. Adjust the nose length, body diameter, fin sweep, and fin thickness until the design is ready for analysis. OpenVSP makes these changes directly through its parametric geometry controls.

Step 2. Export the geometry

Export the finished rocket as an ASCII STL file. This is the file format used by Stallion 3D for imported solid geometry.

Step 3. Import the STL file into Stallion 3D

In Stallion 3D, open the imported STL file, load the rocket geometry, and align it with the flow direction. Confirm the units, check the scale factor, and make sure the surface normals are properly oriented before proceeding.

Step 4. Define the flow conditions

Under the flow parameter settings, enter the aerodynamic conditions for the case. In this example, the angle of attack is 0 degrees, the speed is Mach 2, and the air properties correspond to sea level conditions.

Also enter the reference area, the moment reference length, the rocket weight, and the center of gravity coordinates so the aerodynamic outputs are referenced correctly.

Step 5. Set the CFD solver options

In the CFD solver setup, select a grid size of about 512,000 cells. Use the Reynolds averaged Navier Stokes solver with the k-epsilon turbulence model. For improved numerical accuracy, select the second order solver option.

Set the computational domain large enough to surround the rocket comfortably. Use radiation boundary conditions for the far field, and make the boundary length about eight times the rocket length.

Step 6. Generate the grid and solve the flow

Run the generate grid and solve flow command. Stallion 3D first creates the grid around the rocket and then iterates through the CFD solution until the pressure and velocity fields converge.

Step 7. Review the results

Once the solution is complete, review the pressure distribution along the rocket body and fins. In the example, high pressure appears on the nose and on the leading edges of the fins, while lower pressure regions form in the wake.

Stallion 3D can then compute lift, drag, side force, and stability derivatives that are useful for predicting flight performance.

Takeaway

By combining OpenVSP for fast geometry creation with Stallion 3D for CFD, a rocket concept can be turned into detailed aerodynamic insight in a matter of hours without separate meshing software or external solvers.

The same general workflow can also be used for drones, aircraft, and other aerodynamic configurations.