Measurements of Surface Pressure Distributions on a Freely Falling Sphere with a Tripping Wire

Abstract

The effect of a tripping wire on a sphere in free fall has been investigated. The test sphere is of 1OOmm in diameter, and is equipped with built-in processors, such as a pressure sensor, a tension sensor, an amplifier, a memory, a power supply and a CPU. The tripping wire was formed by a ring of enptyv1mm wire attached to the surface at angles of θ_γ=25° and 55°, respectively, measured from the stagnation point. In the case of θ_γ=25°, the pressure distributions were nearly the same as those on a smooth sphere. In the case of θ_γ=55°, on the other hand, the effects of the tripping wire were striking, indicating a laminar-turbulent transition of the boundary layer at Re≒5×10⁴.