Steady State Simulations of a Mars Entry Vehicle

Using computational fluid dynamics, steady state simulations of a capsule like Mars entry vehicle at certain trajectory points was performed. Trajectory points were chosen incrementally from 90 to 11.5 kilometers altitude. The Direct Simulation Monte Carlo method and the Overflow 2 Navier-Stokes solver were used depending on Knudsen number values greater than or less than 0.1, respectively. To compare flow effects of the maximum angle of attack error margin of three degrees, axially symmetric cases were computed and compared to three dimensional cases demonstrating an attack angle (α) of three degrees. Lift and drag coefficients are reported and compared. The greatest lift and drag coefficients were recorded with the 11.5 kilometer altitude case: 0.0 and 0.635 for α = 0° , and 0.029 and 0.566 for α = 3°, which introduces a lifting force and demonstrates a 12.3% change in drag

Ongoing Study of Supersonic Retro-Propulsion Using Structured Overset Grids and OVERFLOW

The interest in supersonic retro-propulsion (SRP) as a means of deceleration during planetary entry increases with the desire to land high mass vehicles on Mars. Since it is difficult to obtain flight data or properly simulate this type of flow field in a wind tunnel, the use of computational fluid dynamics (CFD) becomes increasingly important, as does the need to verify the current CFD methods. This presentation will show results from structured overset grids and OVERFLOW, a Reynolds Averaged Navier-Stokes solver, obtained during the continuing CFD verification process. Flow structure, surface pressure, forces, and moments are compared to historic and modern wind tunnel data as well as to other Navier-Stokes solvers, DPLR and FUN3D. Cases include single and multiple nozzle cases from the Jarvinen and Adams experiment,i the Daso et al experiment, and a recent test in the NASA Langley Unitary Wind Tunnel (scheduled for June 2010)

Continuing Validation of Computational Fluid Dynamics for Supersonic Retropropulsion

A large step in the validation of Computational Fluid Dynamics (CFD) for Supersonic Retropropulsion (SRP) is shown through the comparison of three Navier-Stokes solvers (DPLR, FUN3D, and OVERFLOW) and wind tunnel test results. The test was designed specifically for CFD validation and was conducted in the Langley supersonic 4 x4 Unitary Plan Wind Tunnel and includes variations in the number of nozzles, Mach and Reynolds numbers, thrust coefficient, and angles of orientation. Code-to-code and code-to-test comparisons are encouraging and possible error sources are discussed