Experimental measurement of the pitching stability derivatives and of AGARD hyperballistic standard models HB1 and HB2, a hemisphere-cylinder double flared configuration designated HBS and three 10° semi angle cones of bluntness ratios 0.0, 0.2 and 0.4 are reported. Data were obtained at a Mach number of 6.85 in a short duration light piston tunnel using the small amplitude free oscillation technique. The tests were conducted at Reynolds numbers from 0.2 × 106 to 0.85 × 106, based on centre-body diameter, for the hyperballistic shapes and from 1.45 × 1016 to 2.17 × 106, based on base diameter, for the conical shapes. The mean angle of attack was varied from 0 to 17.0 degrees and the frequency parameter from 0.0020 to 0.0043 for the hyperballistic shapes and from 0.0018 to 0.0092 for the cones. All models tested were found to be dynamically stable for all positions of the axis of oscillation considered. The significant observed non linear variations of the damping derivative with angle of attack for the 0.2 and 0.4 bluntness cones and the HB2 shape could be partially accounted for qualitatively by boundary layer transition induced effects. The variation of the derivatives with angle of attack for the pointed cone were consistent with a fully turbulent boundary layer, whereas it was probable that for the HB1 and HBS models the boundary layer remained laminar throughout. Variation of the frequency parameter resulted in no significant effect on the measured stability derivatives.

A numerical method for computing potential flow through either a planar or axisymmetric nozzle is described. Some results obtained from a computer program based on this method are presented and compared with experimental data.

If two small fences are arranged approximately at right angles in plan view, the magnitude and direction of surface shear stress can be deduced from measurements of the pressure difference across each fence. Fence heights as small as 0.05 mm are easily achieved. The device is simpler to use than null-seeking arrangements, and is accurate even in the presence of strong pressure gradients, which are shown to have large effects on other types of surface obstacle in three-dimensional flow.

A discrete-vortex representation of the wake of a circular cylinder, in which vortices are convected in a potential-flow calculation and maintain their identities unless they approach one another or a surface closely, predicts many of the unsteady flow features and is computationally more efficient than other schemes. The mean rate of shedding of vorticity is adjusted to be compatible with experiments at a high subcritical Reynolds number of 3 × 104 and the model gives reasonable predictions of separation, drag, lift, Strouhal number and vorticity loss in the formation region. The method is extended to accommodate a second cylinder and many of the surprising features which have been observed experimentally with two cylinders in a side-by-side arrangement are reproduced.

A method is given for the calculation of incompressible, inviscid flow through an axi-symmetric contracting duct for which the two dimensional flow with the same meridianal boundaries is known. The method, which is based on Whitehead, Wu and Waters original proposal, assumes that the contraction consists of two separate portions, upstream and downstream respectively. The flow in each portion is calculated and the two portions matched to produce a contraction of given area ratio with preassigned values of the two dimensional ‘overshoot’ and ‘undershoot’ parameters. It is worth emphasizing that in practice it is only necessary to do the calculations once to predict wall velocities for a family of contraction shapes with different area ratios provided they share a common upstream or downstream portion. The results given here show reasonable agreement with the pressure coefficients obtained in experiment for the upstream end of a small scale contraction of area ratio 16:1. There is however a discrepancy between theory and experiment at the downstream end and a qualitative explanation is advanced for this.