Two-dimensional Circular Cylinder Research Articles

An Experimental Investigation of the Formation and Flow Characteristics of an Impulsively Generated Vortex Street

In this shock tube investigation, the passage of a plane normal shock wave and its associated drift flow over a two-dimensional circular cylinder impulsively generated a vortex street. The operating free stream Reynolds and Mach number range was 3.25 × 104 ≤ Rn ≤ 2.03 × 105 and 0.193 ≤ M∞ ≤ 0.483, respectively. The formation of the initial standing pair of vortices, their shedding, and the subsequent establishment of the vortex street were recorded interferometrically using a high speed framing camera. The movement of the initial vortex pair was observed to be significantly altered for Rn > 1.5 × 105, where a secondary vortex pair was generated and merged with the initial vortex pair well before shedding commenced. During the lifetime of the impulsively generated wake, the Strouhal number, S, approached an average value of 0.16 which is significantly lower than the usual steady-state value of about S ≃ 0.2. Values of spacing ratio were found to decrease with increasing vortex street lifetime for all downstream locations. Other pertinent vortex street characteristics were also reported.

Low Reynolds numbers flow past an ellipsoid of revolution of large aspect ratio

The results of Proudman & Pearson (1957) and Kaplun & Lagerstrom (1957) for a sphere and a cylinder are generalized to study an ellipsoid of revolution of large aspect ratio with its axis of revolution perpendicular to the uniform flow at infinity. The limiting case, where the Reynolds number based on the minor axis of the ellipsoid is small while the other Reynolds number based on the major axis is fixed, is studied. The following points are deduced: (1) although the body is three-dimensional the expansion is in inverse power of the logarithm of the Reynolds number as the case of a two-dimensional circular cylinder; (2) the existence of the ends and the variation of the diameter along the axis of revolution have no effect on the drag to the first order; (3) a formula for drag is obtained to higher order.

VII.Experiments on supersonic flow over flat-nosed circular cylinders at yaw—II: Pressure measurements on a cylinder at10°yaw

Summary In a previous paper (Hall 1954) the supersonic flow over flat-nosed circular cylinders at yaw was investigated by schlieren photography. This investigation was continued for the case of a cylinder at 10° yaw by measurements of the surface pressure distribution, which are described in the present paper. Close to the nose the cross force, obtained by integrating the pressure distribution, was found to be large. This was due to the asymmetry of the boundary layer separation. Further downstream the variation of the cross force with (tistance from the nose was in good qualitative agreement with the variation with time of the drag force on a two-dimensional circular cylinder started impulsively from rest.