EXPERIMENTAL INVESTIGATION OF A'CONTINUOUS YAW DATA ACQUISITION METHOD FOR GROUND VEHICLE AERODYNAMICS

摘要

Classical methods of data acquisition in wind tunnel testing involve a "point pause" approach, where aerodynamic data is gathered over a brief time period with the model orientation and wind tunnel conditions held nominally fixed. Following acquisition of data for an appropriate interval, the model orientation (or tunnel condition) is changed relatively quickly to the next desired value(s) and the process repeated. It is generally acknowledged that this technique is relatively "slow", where a large number of model orientations or tunnel set points are to be investigated. Further, there is little possibility of detecting subtle aerodynamic anomalies occurring between the chosen set points.The possibility of acquiring aerodynamic data on a more-or-less continuous basis, with slow, typically monotonic changes in model orientation and/or tunnel conditions has therefore been a subject of investigation in the aeronautical application. The technique is referred to as "continuous sweep" or similar. No prior investigation into the use of continuous sweep data acquisition with ground vehicle testing is known to the author.An experimental investigation was therefore performed to test the feasibility of continuous data acquisition during yaw angle sweeps of a ground vehicle. The tests were performed in Old Dominion University's (ODU) Langley Full-Scale Tunnel (LFST) with an automotive balance. The LFST is a low speed, continuous return wind tunnel with a large (30 ft. by 60 ft.) open test section. The Ahmed reference model was chosen as the test subject, due to the known stability of the flow structure, and availability of previous data.The experiment shows that force data over a range of yaw angles can be attained in a shorter time period with little loss in data quality. The experiment also showed that aerodynamic details could be detected in the sweep data that would not have been possible with the classical point-pause method of data acquisition.