Current grid-generation strategies and future requirements in hypersonic vehicle design, analysis and testing

Abstract

Recent advances in computational power enable computational fluid dynamic modeling of increasingly complex configurations. A review of grid generation methodologies implemented in support of the computational work performed for the X-38 and X-33 are presented. In strategizing topological constructs and blocking structures factors considered are the geometric configuration, optimal grid size, numerical algorithms, accuracy requirements, physics of the problem at hand, computational expense, and the available computer hardware. Also addressed are grid refinement strategies, the effects of wall spacing, and convergence. The significance of grid is demonstrated through a comparison of computational and experimental results of the aeroheating environment experienced by the X-38 vehicle. Special topics on grid generation strategies are also addressed to model control surface deflections, and material mapping. development and testing. Our involvement in the hypersonic vehicle design is to provide external aerodynamic and aerothermodynamic environments. The requirements for grid generation are determined from the simulation objectives. Aerodynamic simulations are required to determine the stability and controllability

Numerical Assessment of Data in Catalytic and Transitional Flows for Martian Entry

“…For all cases, a 512x172 axisymmetric grid was employed to maintain consistency between the solutions. In each case, the grid was adapted to the shock layer to generate a quality heating profile and a cell Reynolds number of 1.0 was enforced at the surface 35 . Chemical or vibrational freezing in increments of 10% were independently considered up to 50%.…”

Critical Hypersonic Aerothermodynamic Phenomena

“…Surface geometry definition and grid generation still remain the biggest bottlenecks in the CFD process. Papadopoulos et al (1999) stated that, "the factors that limit the use of CFD in the early design phase are how quickly the grids can be generated and how quickly 'sufficiently' accurate CFD simulations can be provided. For complex shapes, 10-100 CFD solutions with marginal fidelity but a very fast turn around time would allow CFD to be part of this stage."…”

“…Papadopoulos et al (1999) showed that, "a com putational mesh and a level of convergence which result in accurate surface-pressure and shear stress values do not guarantee accurate heat-transfer values." In addition, they found that both the level of convergence required for accurate predictions and the numerical algorithm used (including the flux-splitting method and the limiter used) could impact the results of a flow simulation at hypersonic speeds.…”

“…In addition, they found that both the level of convergence required for accurate predictions and the numerical algorithm used (including the flux-splitting method and the limiter used) could impact the results of a flow simulation at hypersonic speeds. Papadopoulos et al (1999) believe that accurate predictions require careful monitoring of both the cell Reynolds number and the temperature jump near the wall. The cell Reynolds number, given by ρ wall a wall �y Re cell = (5) µ wall helps to insure that the initial grid spacing near the wall is small enough to accurately deal with the viscous and heat-transfer effects at the surface.…”

A parametric grid generation tool for the aerodynamic evaluation of hypersonic vehicles

“…Although these are good indicators, the true measure of grid quality is in the validation of the solution and depends on the specific physical problem (Papadopoulos et al, 1999). …”