Journal of Fluid Mechanics

An experimental study of geometrical effects on the drag and flow field of two bluff bodies separated by a gap

Keith  Koenig a1 1 and Anatol  Roshko a1
a1 California Institute of Technology, Pasadena, California 91125

Article author query
koenig k   [Google Scholar] 
roshko a   [Google Scholar] 


This paper describes an experimental investigation of the shielding effects of various disks placed coaxially upstream of an axisymmetric, flat-faced cylinder. Remarkable decrease of the drag of such a system was observed for certain combinations of the basic geometric parameters, namely the diameter and gap ratios. For such optimum shielding the stream surface which separates from the disk reattaches smoothly onto the front edge of the cylinder, in what is close to a ‘free-streamline’ flow; alternatively, the flow may be viewed as a cavity flow. For the optimum as well as other geometries, flow pictures, pressure distributions and some LDV measurements were also obtained. From these, several flow regimes depending on the gap/diameter parameters were identified. Variations on the axisymmetric disk–cylinder configuration included a hemispherical frontbody, rounding of the front edge of the cylinder and a change from circular to square cross-section.

(Published Online April 20 2006)
(Received July 11 1984)


1 Now at Aerospace Engineering, Mississippi State, Mississippi 39762.