Evaluation of the buoyancy drag on automobile models in low speed wind tunnels
Abstract
Of the several sources of inaccuracy in interpreting wind tunnel data for automobile models, the most prominent is the blockage interference. Streamwise variation of the wall induced pressure gives, in addition, rise to buoyancy drag. Buoyancy drag is analyzed in closed, 3/4 open, and slotted wind tunnels. The disturbance velocity potential is represented by a simple layer distribution. A numerical solution is obtained by a first-order panel method, approximating the surface by an assembly of flat panels, with a piecewise constant source density. The increment of the pressure coefficient due to wall interference considers only the contributions of the wall panels. Examples of the calculated buoyancy drag are given for the generic car model of the Motor Industry Research Association. Judged by the magnitude of the buoyancy drag, experiments at high blockage ratios would be highly distorted if performed in a closed-wall test section. However, with 30 percent open area ratio slotted walls, the buoyancy drag is reduced to about the same magnitude as that for test sections with low blockage ratios.
- Publication:
-
4th CASI Aerodynamics Symposium
- Pub Date:
- 1993
- Bibcode:
- 1993casi.symp..144M
- Keywords:
-
- Aerodynamic Drag;
- Aerodynamic Interference;
- Automobiles;
- Low Speed Wind Tunnels;
- Slotted Wind Tunnels;
- Wind Tunnel Models;
- Wind Tunnel Tests;
- Wind Tunnel Walls;
- Bluff Bodies;
- Buoyancy;
- Panel Method (Fluid Dynamics);
- Wall Flow;
- Fluid Mechanics and Heat Transfer