This paper considers the convection of the dynamicstall vortex. A brief discussion of existing data isgiven. A comparison of two sets of data fromdifferent experimental facilities is then presented,and it is indicated that an important anomaly existsconcerning the behaviour of the dynamic stallvortex. It emerges that freestream Mach number isthe only parameter that can account for the observeddifferences. The importance of this parameter isthen discussed in the context of vorticity flux fromthe aerofoil surface.

Flow transition in the developing region of a planewall jet is studied experimentally by means ofhot-wire measurements. The Reynolds number, based onthe jet exit velocity and nozzle exit height, variesfrom 3 x 102 to 3 x 104 in theinvestigations. The results indicate that the mostimportant factor causing wall jet flow to changefrom the initial exit state to the final turbulentstate is the rapid increase of turbulent intensityfrom the formation of vortical structures and theirinteractions with the wall. Data also shows that thetransition process of the wall jet depends on theReynolds number in the operating range. When theReynolds number is greater than 2000, the meanvelocity distribution of the wall jet changesdirectly from a top-hat profile at the nozzle exitto a turbulent profile in the turbulent developedregion. When the Reynolds number is smaller than2000, Glauert's laminar velocity profile is foundbetween the nozzle exit and the turbulent region. Itis also found that the transition will be delayedand the transition region prolonged with thedecrease of the Reynolds number.

A non-linear methodology based on high resolutionNavier-Stokes solutions has been proposed to predictincipient separation boundaries. Comparison has beenmade between the prediction and an empiricalcriterion based on vast experimental data.

In planning interplanetary missions which involve anaerobraking manoeuvre, it is necessary to makeaccurate predictions of the aerodynamic drag actingon a vehicle during its descent. Of interest to theauthors is the Nasa initiative for exploration ofMars and its atmosphere. The Mars Pathfinder is aprobe that is expected to enter the Martianatmosphere at a relative velocity of approximately7.6 kms-1;. The forebody of this vehicleis based on a 70° blunted cone and is typical ofaerobraking designs.

In this note, a comparison is made between experimentaland numerical techniques for predicting drag inhypervelocity flow. Three different models wereexamined in this study: a 30° sharp cone; an Apolloheat shield; and a Viking heat shield. A relativelysimple analytical result for the drag on a coneprovides a convenient reference for both theexperimental and numerical results. The two heatshields are typical of those used for interplanetaryexploration, such as the Mars Pathfinder. Our aim isto give an example of how computational fluiddynamics can be used in conjunction with experimentsto obtain information about the hypervelocity flowabout re-entry vehicles.

This paper addresses the problem of limit-cycle taming,which is defined in this paper as the use ofnonlinear control laws to ensure that thelimit-cycle behaviour of the system beyond thestability boundary is of a benign rather than adestructive nature. Specifically, we consider aone-parameter (denoted by λ) autonomous dynamicsystem having algebraic nonlinearities. We assumethat the system has a stable solution, x = 0, for λ< λ0, and experiences a Hopfbifurcation at λ = λ0. Using a singularperturbation analysis about the stability boundary,it is shown that, using a simple nonlinear controllaw, limit-cycle taming is always possible in theneighbourhood of a Hopf bifurcation. The controlsystem proposed for limit-cycle taming is fullynonlinear, and therefore does not affect the linearbehaviour of the system (in particular its stabilitycharacteristics). Hence, limit-cycle taming may beused in conjunction with a standard linear activecontrol (e.g. use of linear active control toincrease the stability boundary). Applications ofthe theory to the problem of flutter arepresented.

This paper describes the implementation of the DRAGVAM87 model in Modula-2, using the Hood designmethodology, and the subsequent validation of thereal-time model running on a personal computer. Thework demonstrates that the execution speed of themodel is not compromised while overall validity ofthe simulation is maintained. The model wasinterfaced with an existing simulation of the SeaHarrier head-up display (hud) in order to providevisual cues of the aircraft's motion during pilotedflight.