Prototype

Modeling

Both experimental data obtained from the NASA Ames Research Center, and from Computational Fluid Dynamics (CFD) experiments, provide the range of forces and moments on the CONEX and tailfin. The CFD experiments will be performed on a Beowulf cluster housed at Northern Arizona University under the supervision of Dr. Earl Duque.

The CFD angle-of-attack static sweep for the 6'x6'x8' CONEX alone for 361 cases shows good correlation with experimental data (Appendix B). Currently, the results for the angle-of-attack sweep for the 6'x6'x8' CONEX and the passive NACA0015 tailfin combination are in process (Appendix C). The angle-of-attack sweep for the active tailfin alone has just begun and is projected to give data for 200 cases. All cases are run steady, using the Spalart-Allmaras turbulence model. A few unsteady cases, at angles-of-attack corresponding to high-frequency vortex shedding, are also being run.

The forces from the CFD computations will be used to mathematically model our design inside a Finite Elements Analysis (FEA) package. The goal of the FEA model will be to produce the least-expensive mounting hardware that also satisfies the design requirements.

Testing

In order to test some of our static design concepts, we will also build a small-scaled model of the CONEX to test various fuselages and fin placements. The scale model tests will use Froude and Strouhal numbers as closely as possible (Appendix D). The model test will consist of both "truck tests" as well and wind tunnel testing. The truck test consists of attaching the model to a frame on a truck and matching dimensionless weight and frequency numbers. The test vehicle will be driven under controlled conditions, and within DPS safety requirements. The main goal of these tests is to determine the effect of static fin placements and fuselage faring shapes upon the CONEX yawing motions.

After development of the mounting hardware and the active control laws, we plan to test a prototype in a wind tunnel here in northern Arizona. The purpose of the wind tunnel test will be to verify proof-of-concept for the active fin. The wind tunnel we will use is as Southwest Windpower, Inc. It is a small 64kW open jet machine capable of wind speeds from 10 to 50 mph in a 96in x 96in test section. Simple data acquisition systems are available to record Tunnel Q and model data. Below are views of the tunnel and of the test section with an AirX wind turbine installed.