Efficient Optimization of Ringlets for Drag Reduction over the Complete Mission Profile

Use of microsurface features such as riblets within turbulent boundary layers has proved to be an effective means of friction drag reduction. This paper proposes an effective and efficient methodology for riblet optimization for the complete mission profile with varying speed and altitude. An altitude-correction method was first developed that provided an efficient method for the prediction of drag-reduction ratios for different altitude with much fewer computational fluid dynamics solutions. The method built on data obtained from a Reynolds-averaged Navier–Stokes simulation with the k−ϵ turbulence model. The Reynolds-averaged Navier–Stokes results have been validated against experimental data for a flat plate with V-shaped grooves. Such a procedure was combined with a genetic algorithm and response surface models to obtain a riblet configuration with optimal drag reduction for the complete mission profile. Compared to traditional single-point optimization, an additional improvement of 1.53% (increasing by 20.8 from 7.38%) in drag-reduction ratio could be achieved with this method. The results presented here could provide significant practical engineering value for the riblet design for flight vehicles with a wide range of varying operating conditions.