Passive boundary layer control experiments were conducted on a small supersonic sidewall intake at a Mach number of 1·46 to study the possibility of controlling and improving the intake performance by such a control. The passive control configurations tested included a suction slot in the intake duct located down stream of the shock system (1) connected by a breather passage to a narrow tangential injection slot upstream of the intake and (2) vented to a location where the pressure is free stream static pressure and well away from the inlet of the intake. The results of the experiments showed, that for a supersonic intake, passive control can control the pre-entry shock position, reduce the shock interaction losses and improve the overall pressure recovery.

A numerical technique for the stability analysis of linear mechanical dynamic systems with periodically varying parameters is proposed. The technique is based on representation of the solution vector in terms of Chebyshev polynomials defined over the principal period. Two formulations have been presented. The first formulation is suitable for systems described by state space equations, while the second can be applied directly to a set of second order equations with periodically varying mass, damping and stiffness matrices. As an illustrative example, the flap-lag stability of a multi-bladed rotor is examined. The numerical accuracy and efficiency of the proposed technique is compared with standard numerical codes based on Runge-Kutta, Adams-Moulton and Gear algorithms. The results indicate that the suggested approach is by far the most efficient one, particularly for systems with larger dimensions.

The dynamic stall characteristics of a NACA 0015 performing ramp-up motions are considered. Pressure data show the development and convection of structures at the leading and trailing edges, which indicate differing degrees of what are described as leading edge and trailing edge stall mechanisms. When a transition strip is placed at the leading edge, the characteristics of leading edge stall predominate, and the growth of the structure at the trailing edge is suppressed. In addition the stall vortex convection speed is observed to alter significantly, which is interpreted as a change in the vortex origin, size, strength and trajectory.