 low densiti wind tunnel studi shock wave structur relax phenomena gase low densiti wind tunnel studi shock wave structur relax phenomena gase profil thick normal shock wave moder strength determin experiment term variat equilibrium temperatur insul transvers cylind free-molecul flow shock wave produc steadi jet low-densiti wind tunnel initi mach number 1 72 1 82 helium 1 78 shock thick determin maximum slope cylind temperatur profil vari free path superson stream comparison experiment shock profil theoret predict lead tent conclus 1 navier-stoke equat adequ descript shock transit initi mach number 2 2 effect rotat relax time air account introduct second bulk viscos coeffici equal two-third ordinari shear viscos 