The class of aircraft known as gyroplanes (orautogyros) helped to pave the way for thedevelopment of the helicopter. However, they havefound no application in contemporary commercial ormilitary aviation. It is in recreational or sportflying that the gyroplane has proved popular. Mostif not all designs are however homebuilts, and as aconsequence little analysis of any significance hasbeen conducted on the flight mechanics of theseaircraft. This Paper presents an analysis of thelongitudinal stability of gyroplanes. Simpleconsideration of the basic forces and moments thatmight influence stability, in the context ofelementary rotor behaviour, is used to assess thefundamental nature of gyroplane longitudinalstability. This is quantified by the application ofa sophisticated generic rotorcraft mathematicalmodel to the gyroplane problem. It is concluded thatthe basic configuration can be longitudinally stablewith appropriate design, and that the rotorspeeddegree of freedom must also be included whenmodelling the aircraft.

A novel automatic grid generation method for complexCFD applications has been developed, driven by theneed of the industrial CFD practitioner to reducethe turnaround time from an initial CAD geometry toobtaining a flow simulation. The method uses asubdivision strategy, allowing hanging nodes in aCartesian unstructured mesh environment and iscombined with a non-overlapping, semi-structuredsurface grid. Unusually, the surface grid is the endrather than the starting point of the presentapproach. This reversal of gridding strategy allowsusability to be enhanced, in that the gridgeneration is reduced to one automatic step. Thecapabilities of the method are demonstrated byreference to selected inviscid and viscous flowsolutions using the Fluent code Rampant v4.0 as aflow solver.

Steady, inviscid, incompressible, two dimensional flowscontaining vortex patches bounded by vortex sheetsare used to model finite separated regions oncertain closed bodies as an approach to modellingseparation bubbles. First of all the problem of avortex patch on a circle is considered. Calculationswere done for symmetric flows covering a wide rangeof values of the separation position, the strengthof the vortex sheet and the circulation at infinityand for non-symmetric flows at various angles ofincidence. Smooth separation was detected in somecases. This model is used as an intermediate stepfor the calculation of the flow around an ellipseand a Joukowski aerofoil with the use of theJoukowski transformation.

During recent years a new vortex model of the unsteadyaerodynamics of a hovering rotor or a rotor in axialflight, named Temura, has beendeveloped in the Technion. This model has succeededin describing various phenomena of rotor dynamics.In the present paper Temura is usedin order to develop a model which describes theblades’ responses to harmonic variations of theirpitch angles. This model includes unsteadyinfluences of trailing and shed vortices, togetherwith unsteady geometric effects which represent aspecial capability of Temura. Themodel is general and can be applied to any number ofblades and arbitrary differences between the pitchangle variations of different blades. Theapplication of the model to analyse cases ofcollective harmonic pitch variations anddifferential harmonic pitch variations is presented.Numerical results of the new model are compared withexperimental results from the literature and goodagreement is shown.