Efficient Optimization Of Riblet Drag Reduction And Aerodynamic Heating

Drag reduction is a fundamental technical issue in flight vehicle design.For civil aircraft,reduction of drag can improve its economic efficiency and flight performance.For missiles,“drag reduction and range increase” is always a high priority goal for designers.Use of micro surface features such as riblets within turbulent boundary layers has proved to be an effective means of friction drag reduction.This paper developed an efficient phased riblet design method for aerodynamic drag and heating analysis.With this method,optimal parameters of riblets on various geometries can be obtained based on RANS results.The effects of flow conditions,the size and shape parameters of riblet on friction drag were first studied respectively.An altitude correction method was then developed to provide an efficient method for the prediction of drag reduction ratios at different flight altitudes with much fewer number of CFD solutions.Genetic algorithm and response surface models were used to obtain riblet parameters with optimal drag reduction for specific flow conditions and the complete mission profile.Cases of realistic geometries with large coverage of riblets present particular challenge for direct CFD analysis,a new riblet wall function based on Spalding formula was proposed to predict drag reduction effect of riblets.This method adjusted velocity profile within the turbulent boundary layer to account for the effects of riblet.Validations of the method on various geometries were conducted including NACA 0012 airfoil,CAST 7 airfoil and GAW(2)wing.With this method,RANS simulation on RAE 2822 airfoil and ONERA M6 wing with riblet covered for both subsonic and supersonic flow conditions were carried out in OpenFOAM.Based on the studies of drag reduction characteristics of riblet and riblet wall function,the effects of riblet on aerodynamic heating were considered in a computational process based on the change in friction coefficients.The relationships between riblet parameters and wall heat flux density were obtained using aerodynamic heating analysis methods.By analyzing the wall temperature variations of missile under two typical flight profiles,the effects of riblet on wall heat flux density and surface temperature field were obtained.The analysis and results showed that the paper provides an effective and efficient methodology for riblet optimization for the complete mission profile.Riblet wall function and aerodynamic heating analysis method based on MATLAB were developed for the aerodynamic drag and heating simulation of riblet-covered surfaces.This research provides a basis for further research on optimal design of riblets with an important academic value and engineering applications.