Influence of surface roughness distribution on aerodynamic characteristics of vehicles

To address the challenge of predicting the effects of surface roughness on the aerodynamic characteristics and trajectory of vehicles during hypersonic reentry, this work establishes a feasible loosely coupled model integrating aerodynamics in engineering applications, aerothermal effects, dynamic ablation, and structural heat transfer, forming a coupled system with mutual interactions. Based on this model, a statistical approach is introduced to characterize the uncertainty of surface roughness, and a distributed random roughness model is developed with the statistical means and variances of different meridional planes as constraints. The model is used to represent the non-uniform surface roughness morphologies of axisymmetric spherical-cone reentry vehicles arising from manufacturing and ablation processes, and to investigate their effects on the aerodynamic and trajectory characteristics of the vehicle. The numerical results indicate that, as the regular surface roughness of the vehicle increases from 3 μm to 9 μm, the drag coefficient rises by 6.2×10⁻⁴, and the horizontal flight distance in the late reentry phase is reduced by approximately 34 meters. When randomly distributed roughness is considered, with both the mean roughness and variance set to 9 μm, the difference in horizontal flight distance relative to the 3 μm regular roughness case reaches 111 meters, which is 77 meters greater than that in the 9 μm regular roughness case. These findings provide a new perspective for aerodynamic prediction and thermal protection system design of reentry vehicles.