Experimental study of mutual interference between two spheres placed on a plane boundary

This paper describes an experimental study of the mutual interference between two spheres placed on a plane boundary. The experiment was carried out in an N. P. L. type wind-tunnel having a working section of 500×500×2000 mm³ in size at a Reynolds number of 4.74×10⁴. The surface-pressure distributions of two spheres were measured for the various relative positions of two spheres and the drag, side-force, and lift coefficients were determined from surface-pressure distributions. The separation of the flow and the formation of vortices were observed by the method of visualization. The distributions of velocities, and turbulent intensities of the flow past two spheres were measured. The experimental results for two spheres were compared with those of a single sphere.List of symbols C _D drag coefficient - C _L lift coefficient - C _p surface-pressure coefficient of sphere=(P-P )(qU ² ) - C _s coefficients of side force - D diameter of sphere mm] - P static pressure Pa] - P static pressure in free stream Pa] - Re Reynolds number= DU/v - S spacing between the centers of two adjoining spheres in plane view mm] - U time-mean velocity in X-direction m/s] - m/s] free stream velocity m/s] - u, v, w X, Y and Z-components of velocity fluctuation m/s] - X, Y, Z coordinate axes with origin at the bottom center of test sphere, X, Y, Z axis being taken in the streamwise, lateral and vertical directions respectively mm] (Fig. 1) - latitude angle °] - longitude angle °] - angle between the line connected with the centers of two spheres and wind direction °] (Fig. 2) - kinematic viscosity of air m²/s] - density of air N/m³] This paper was presented at the 10th Symposium on Turbulence, University of Missouri-Rolla, Sept. 22–24, 1986