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
Computational(_t,1)yrigId @211(11by th, hi|if i'll i_lt Institute (,f Aeronautics and Astr.nautics, In,. N,, ,:,q,yrigh( is asscrt(xl in the United States und, r Tith 17, II.S. (:(,,h. 'l'h( U.S.g.vernm_nt hasa r,yaltyt'r,_ li (_ns, t,, (xcr[isc MI rig.his under th(: c,, The ttow undergoes a pair of rapid expansions at the heatshield shoulder (point 1 in Fig. 5a) and the rearward facing step (point 2), which result in a local increase in heat transfer during the expansion, followed by a rapid decrease. An enlargement of the afterbody region is shown in Fig. 5b. The numbers in Fig. 5b correspond to the inset in Fig. 5a. The normal spacing was identical to the previous grid.From Fig. 6 .j"
Kn¢;LL
/-
A proposed Mars Smart Lander is designed to reach the surface via lifting-body atmospheric entry (α = 16 deg) to within 10 km of the target site. CFD predictions of the forebody aeroheating environments are given for a direct entry from a 2005 launch. The solutions were obtained using an 8-species gas in thermal and chemical nonequilibrium with a radiative-equilibrium wall temperature boundary condition. Select wind tunnel data are presented from tests at NASA Langley Research Center. Turbulence effects are included to account for both smooth body transition and turbulence due to heatshield penetrations. Natural transition is based on a momentum-thickness Reynolds number value of 200. The effects of heatshield penetrations on turbulence are estimated from wind tunnel tests of various cavity sizes and locations. Both natural transition and heatshield penetrations are predicted to cause turbulence prior to the nominal trajectory peak heating time. Laminar and turbulent CFD predictions along the trajectory are used to estimate heat rates and loads. The predicted peak turbulent heat rate of 63 W/cm 2 on the heatshield leeward flank is 70% higher than the laminar peak. The maximum integrated heat load for a fully turbulent heat pulse is 38% higher than the laminar load on the heatshield nose. The predicted aeroheating environments with uncertainty factors will be used to design a thermal protection system.
NOMENCLATUREmomentum thickness ∞ freestream --------------* Vehicle Analysis Branch, Senior Member, AIAA. † Aerothermodynamics Branch.
Computational(_t,1)yrigId @211(11by th, hi|if i'll i_lt Institute (,f Aeronautics and Astr.nautics, In,. N,, ,:,q,yrigh( is asscrt(xl in the United States und, r Tith 17, II.S. (:(,,h. 'l'h( U.S.g.vernm_nt hasa r,yaltyt'r,_ li (_ns, t,, (xcr[isc MI rig.his under th(: c,, The ttow undergoes a pair of rapid expansions at the heatshield shoulder (point 1 in Fig. 5a) and the rearward facing step (point 2), which result in a local increase in heat transfer during the expansion, followed by a rapid decrease. An enlargement of the afterbody region is shown in Fig. 5b. The numbers in Fig. 5b correspond to the inset in Fig. 5a. The normal spacing was identical to the previous grid.From Fig. 6 .j"
Kn¢;LL
/-
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.