An experimental investigation of fluid dynamic interference forces
Experimental investigations have been conducted in the VPI & SU towing basin to assess the feasibility of testing fully submerged configurations, simulating aerodynamic phenomena, and in particular, measuring aerodynamic interference force between blunt bodies. Special instrumented struts were constructed and calibrated for the measurement of drag and side forces. A series of tests were conducted with spherical models in order to verify the reliability of the method by comparison with earlier classical results. The effects of flat walls and surface wave formation were studied and it was discovered that their influence on aerodynamic forces is reduced to less than 10% if the body is removed from the wall or the surface by a distance larger than half its typical width. Experiments were also conducted with crude models that approximate the shapes of a passenger car and a truck. In particular, the passing process under the presence of a strong wind was simulated by towing the models at an angle of 240 with respect to motion of the carriage. The results appear to be essentially in agreement with the data received with much larger models tested in air, by other investigators.