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WAKE OF A BLOCK VEHICLE IN A SHEAR-FREE BOUNDARY FLOW: AN EXPERIMENTAL AND THEORETICAL STUDY
Citation:
Eskridge, R. AND Roger S. Thompson. WAKE OF A BLOCK VEHICLE IN A SHEAR-FREE BOUNDARY FLOW: AN EXPERIMENTAL AND THEORETICAL STUDY. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/3-82/007 (NTIS PB82196528).
Description:
The wake of a moving vehicle was simulated using a specially-constructed wind tunnel with a moving floor. A 'block-shaped' model vehicle was fixed in position over the test-section floor while the floor moved at the freestream air speed to produce a uniform, shear-free, approach flow. This simulates an automobile traveling along a straight highway under calm atmospheric conditions. Vertical and lateral profiles of mean and fluctuating velocities and Reynolds stresses in the wake of the vehicle were obtained using a hot-film anemometer with an X-probe. Profiles were taken at distances of 10 to 80 model heights downwind. A momentum type wake was observed behind the block-shaped vehicle. The wake does not have a simple self-preserving form. However, it is possible to collapse the velocity deficit with one length and one velocity scale. Two new theories for the velocity deficit are compared to the theory of Eskridge and Hunt (1979). A theory which considered a height-dependent eddy viscosity was found to fit the data best. Length and velocity scales were found for the longitudinal variation of the turbulent kinetic energy. The lateral variation is described by a two-dimensional numerical fit of the crosswind variation of the data.