Annual Research Briefs ...


Book Description




Time Accurate Computation of Unsteady Inlet Flows with a Dynamic Flow Adaptive Mesh


Book Description

Research has been performed to obtain very accurate dynamic simulations of supersonic inlet unstart using CFD codes and a dynamic solution adaptive mesh algorithm developed at NCSU. The codes use Runge-Kutta time differencing and Advective Upwind Split Method spatial differencing in finite volume form. Other changes have been incorporated to improve the time accuracy when the computational mesh is dynamically adapted. Solutions have been obtained and animated for unstart of generic 2-D mixed compressions and fully supersonic inlets. Analysis of results revealed that laminar viscous flow unstart occurs by a separation/oblique shock mechanism rather than movement of a normal shock. Turbulent flow simulations reveal that initial shock motion occurs initially but then reverts to the separation/oblique shock mechanisms. 3-D steady and unsteady simulations are presented and conclusions drawn concerning the role of separation in inlet unstart. Computational fluid dynamics, Dynamic adaptive mesh, Mixed compression inlet unstart, Unsteady flow.




Aerospace America


Book Description







Analysis of Hypersonic Aircraft Inlets Using Flow Adaptive Mesh Algorithms


Book Description

The numerical investigation into the dynamics of unsteady inlet flowfields is applied to a three-dimensional scramjet inlet-isolator-diffuser geometry designed for hypersonic type applications. The Reynolds-Averaged Navier-Stokes equations are integrated in time using a subiterating, time-accurate implicit algorithm. Inviscid fluxes are calculated using the Low Diffusion Flux Splitting Scheme of Edwards. A modified version of the dynamic solution-adaptive point movement algorithm of Benson and McRae is used in a coupled mode to dynamically resolve the features of the flow by enhancing the spatial accuracy of the simulations. The unsteady mesh terms are incorporated into the flow solver via the inviscid fluxes. The dynamic solution-adaptive grid algorithm of Benson and McRae is modified to improve orthogonality at the boundaries to ensure accurate application of boundary conditions and properly resolve turbulent boundary layers. Shock tube simulations are performed to ascertain the effectiveness of the algorithm for unsteady flow situations on fixed and moving grids. Unstarts due to a combustor and freestream angle of attack perturbations are simulated in a three-dimensional inlet-isolator-diffuser configuration.