A self‐adaptive gridding for inviscid transonic projectile aerodynamics computation

Abstract

AbstractAn adaptive grid generation technique based on modified variational principles coupled with an exponential clustering has been developed and tested successfully for the computation of steady inviscid transonic projectile aerodynamics. The isoperimetric problem for adaptive gridding is to extremize a grid smoothness functional subject to grid orthogonality and resolution functionals; however, the Lagrange multipliers have been assumed to be variables with zero variation and are properly chosen as functions of local grid size to enhance locally the grid resolution as well as to maintain the weight of three grid characteristics the same over the entire flow field. With computed pressure gradient as the control function for grid adaptation, the resulting Euler equations cannot provide sufficient grid resolution in the boundary layer region of the projectile geometry; hence, a clustering technique is needed to redistribute the points along the normal grid lines. A grid generation code has been developed and coupled to an axisymmetric thin‐layer Navier‐Stokes code for self‐adaptive grid generation. For the three transonic flow cases considered, M∞ = 0.91, 0.96 and 1.10, the distribution of surface pressure calculated from the inviscid option of the Navier‐Stokes code is indeed in excellent agreement with published measured data.