THE DEVELOPMENT OF A STRUCTURED MESH GRID ADAPTION TECHNIQUE FOR RESOLVING SHOCK DISCONTINUITIES IN UPWIND NAVIER-STOKES CODES

A technique is described for the adaptation of a structured control vo lume mesh during the iterative solution process of the Navier-Stokes e quations. The scalar equidistribution method is adopted, in conjunctio n with a Laplace-like grid solver to make a curvilinear body-fitted gr id sensitive to local flow gradients. Hence, whilst the total number o f grid nodes remains constant during a computation, their relative pos ition is continuously adjusted to promote clustering of cells in regio ns where gradients are high. The focus of this work is in compressible aerodynamics, where such clustering would be desirable in regions con taining shocks but also in boundary layers. The technique is three-dim ensional and operates in a series of user-defined grid subdomains or p atches. These patches act as reference frames within which grid activi ty takes place. Bi-cubic splines are extensively used to define the ae rodynamic surfaces forming the calculation boundaries and to ensure th at grid movement does not compromise surface integrity. The technique is applied to aerofoils, wing surfaces, transonic ducts and nozzles an d a supersonic wedge cascade. Significant sharpening of both normal an d oblique shock discontinuities is demonstrated over static grid simul ations and with fewer overall grid nodes. The technique is successful in both inviscid and viscous (turbulent) simulations.