This paper considers the convection of the dynamic stall vortex. A brief discussion of existing data is given. A comparison of two sets of data from different experimental facilities is then presented, and it is indicated that an important anomaly exists concerning the behaviour of the dynamic stall vortex. It emerges that freestream Mach number is the only parameter that can account for the observed differences. The importance of this parameter is then discussed in the context of vorticity flux from the aerofoil surface.

Flow transition in the developing region of a plane wall jet is studied experimentally by means of hot-wire measurements. The Reynolds number, based on the jet exit velocity and nozzle exit height, varies from 3 x 102 to 3 x 104 in the investigations. The results indicate that the most important factor causing wall jet flow to change from the initial exit state to the final turbulent state is the rapid increase of turbulent intensity from the formation of vortical structures and their interactions with the wall. Data also shows that the transition process of the wall jet depends on the Reynolds number in the operating range. When the Reynolds number is greater than 2000, the mean velocity distribution of the wall jet changes directly from a top-hat profile at the nozzle exit to a turbulent profile in the turbulent developed region. When the Reynolds number is smaller than 2000, Glauert's laminar velocity profile is found between the nozzle exit and the turbulent region. It is also found that the transition will be delayed and the transition region prolonged with the decrease of the Reynolds number.

A non-linear methodology based on high resolution Navier-Stokes solutions has been proposed to predict incipient separation boundaries. Comparison has been made between the prediction and an empirical criterion based on vast experimental data.

In planning interplanetary missions which involve an aerobraking manoeuvre, it is necessary to make accurate predictions of the aerodynamic drag acting on a vehicle during its descent. Of interest to the authors is the Nasa initiative for exploration of Mars and its atmosphere. The Mars Pathfinder is a probe that is expected to enter the Martian atmosphere at a relative velocity of approximately 7.6 kms-1;. The forebody of this vehicle is based on a 70° blunted cone and is typical of aerobraking designs.

In this note, a comparison is made between experimental and numerical techniques for predicting drag in hypervelocity flow. Three different models were examined in this study: a 30° sharp cone; an Apollo heat shield; and a Viking heat shield. A relatively simple analytical result for the drag on a cone provides a convenient reference for both the experimental and numerical results. The two heat shields are typical of those used for interplanetary exploration, such as the Mars Pathfinder. Our aim is to give an example of how computational fluid dynamics can be used in conjunction with experiments to obtain information about the hypervelocity flow about re-entry vehicles.

This paper addresses the problem of limit-cycle taming, which is defined in this paper as the use of nonlinear control laws to ensure that the limit-cycle behaviour of the system beyond the stability boundary is of a benign rather than a destructive nature. Specifically, we consider a one-parameter (denoted by λ) autonomous dynamic system having algebraic nonlinearities. We assume that the system has a stable solution, x = 0, for λ < λ0, and experiences a Hopf bifurcation at λ = λ0. Using a singular perturbation analysis about the stability boundary, it is shown that, using a simple nonlinear control law, limit-cycle taming is always possible in the neighbourhood of a Hopf bifurcation. The control system proposed for limit-cycle taming is fully nonlinear, and therefore does not affect the linear behaviour of the system (in particular its stability characteristics). Hence, limit-cycle taming may be used in conjunction with a standard linear active control (e.g. use of linear active control to increase the stability boundary). Applications of the theory to the problem of flutter are presented.

This paper describes the implementation of the DRA GVAM87 model in Modula-2, using the Hood design methodology, and the subsequent validation of the real-time model running on a personal computer. The work demonstrates that the execution speed of the model is not compromised while overall validity of the simulation is maintained. The model was interfaced with an existing simulation of the Sea Harrier head-up display (hud) in order to provide visual cues of the aircraft's motion during piloted flight.