For practical purposes, it is beneficial to be able to predict the useful operating range of an aerofoil in oscillatory motion before the onset of the strong non-linear effects associated with dynamic stall. In the current work, a range of criteria which have been used to indicate the onset of dynamic stall are presented. It is observed that, since all of these are based on physical manifestations of the dynamic stall process, they may only provide an indication that the process has started rather than identifying the initiation itself. A more suitable criterion for this is the concept of critical angle, first proposed by Wilby. It is shown that the critical angle, which is normally determined through an extensive programme of oscillatory tests on a given aerofoil, is achieved in advance of all the other criteria. The present work presents a correlation which has the potential to determine the critical angle, and hence the useful oscillatory range of an aerofoil, on the basis of simple ramp function tests.

The problem of designing a composite laminated plate subject to multiple loading cases is addressed using the methodology of heuristic redesign. Lower bounds on extensional stiffnesses together with a maximum strain first ply failure criterion constitute the design constraints. The general theory of heuristic redesign and its application to this particular problem are described. Results for different combinations of loading cases and redesign strategies are presented.

A comparative study is made on the performance of several low Reynolds number k-ε models and the k-ω model in predicting the shockwave-turbulent-boundary layer interaction over a supersonic compression ramp of 16°, 20° and 24° at a Mach numbers of 2.85, 2.79 and 2.84, respectively. The model equations are numerically solved by a higher order upwind scheme with the 3rd order MUSCL type TVD. The computational results reveal that all of the low Reynolds number k-ε models, particularly those employing y+ in their damping functions give erroneously large skin friction in the redeveloping region. It is also interesting to note that the k-ε models, when adjusted and based on DNS data, do not perform better, as expected, than the conventional low Reynolds number k-ε models. The k-ω model which does not adopt a low Reynolds number modification brings about reasonably accurate skin friction, but with a later onset of pressure rise. By recasting the ω equation into the general form of the ε equation, it is inferred that the turbulent cross diffusion term between k and ε is critical to guarantee better performance of the k-ω model for the skin friction prediction in the redeveloping region. Finally, an asymptotic analysis of a fully developed incompressible channel flow, with the k-ε and the k-ω models, reveals that the cross diffusion mechanism inherent in the k-ω model contributes to the better performance of the k-ω model.