Accession Number : ADA266692


Title :   Free-Wake Computation of Helicopter Rotor Flowfield for General Flight Regimes


Descriptive Note : Final rept. 1 Oct 89-30 Sep 92,


Corporate Author : FLOW ANALYSIS INC BROOKLYN NY


Personal Author(s) : Ramachandran, Krishna ; Steinhoff, John ; Yonghu, Wenren


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a266692.pdf


Report Date : 30 Sep 1992


Pagination or Media Count : 79


Abstract : A CFD based computer code, HELIX II has been developed for computing helicopter rotor flowfield in hover and in forward flight. In order to predict the vibratory airloads in forward flight and the performance in hover the effect of shed wake has to be accurately accounted for. This has been accomplished by an unique vorticity embedding procedure. The wake is convected in a Lagrangian sense and does not suffer from numerical dissipation. The effect of this convected wake is included in the Eulerian using Clebsch representation. The unsteady full potential equation is solved in the Eulerian grid with the embedded vortical velocity accounting for the influence of wake. The wake evolves as a part of the solution. Dynamic grid modifications are performed at each time step to account for blade motion and deformation. These modifications are confined to regions near the blade using suitable blending functions. In addition a vorticity confinement method is developed which involves adding a term to the momentum conservation equation of fluid dynamics. This modification is very useful in the numerical solution of flow problems involving vortical regions. The Euler equations solved with this extra term can convect vortices without Numerical dissipation. Unsteady airloads, Lagrangian wake convection, Eulerian grid, Vorticity Embedding, Clebsch representation, Vorticity confinement, Euler Equation solution without dissipation


Descriptors :   *COMPUTER PROGRAMS , *HELICOPTER ROTORS , *FLOW FIELDS , VELOCITY , COMPUTATIONS , ACCOUNTING , BLENDING , COMPUTERS , MODIFICATION , REGIONS , MOMENTUM , FLUID DYNAMICS , CONSERVATION , EULER EQUATIONS , FLUIDS , EMBEDDING , WAKE , FLIGHT , HELICOPTERS , HELIXES , BLADES , DEFORMATION , MOTION , CONVECTION , DISSIPATION , VORTICES , COMPUTATIONAL FLUID DYNAMICS


Subject Categories : Helicopters
      Computer Programming and Software
      Fluid Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE