Numerical Investigations On Aerodynamic Characteristics And Shape Optimization Of Grid Fins

Grid fin is an unconventional lifting and control surface that consists of an outerframe with an inner grid of intersecting planar surfaces of small chord. As a new type oflifting surface, grid fins have excellent aerodynamic characteristics in subsonic,transonic and supersonic flow, especially in supersonic flow at large angles of attackand high Mach number. Recent years, the U.S. Air Force are attempting to use grid finreplacing planar fin as the controlling system of the small diameter bomb. In this paper,according to the aerodynamic requirements for certain type of body-fin configuration, aframe grid fin is designed based on the principle of equivalence of lift area in order toexplore the feasibility to replace the conventional planar fin.Numerical simulation of the body-Fin configurations with Planar Fins and GridFins is conducted at subsonic、transonic and supersonic speeds. The aerodynamiccharacteristics is obtained via3D flow-field simulation and the configurationoptimization requirements of Grid fins are compared and analyzed. An optimizationmethod based on Design of Experiment、Kriging model and genetic algorithm isdeveloped in the Matlab environment and the feasibility of the method is provedthrough calculating global extreme of test functions. This method is then applied to theaerodynamic optimization design of Grid fins.This paper includes7chapters as follows:Chapter1is an introduction that summarizes the background and research statusand the application of grid fins. The main work of this paper is introduced in the end ofthis chapter.In chapter2, the numerical methods applied in this paper are describedsystematically. The RANS equations are discredited with finite volume method, and theLUSGS method is adopted for implicit approach.Chapter3uses two standard cases include one representative grid fin and body-finconfiguration to validate the numerical methods adopted in the dissertation.Numerical simulation of the body-Fin configurations with Planar Fins and GridFins was conducted and compared at subsonic、transonic and supersonic speeds inchapter4. The sensitive parameters of grid fins are obtained.Chapter5introduces the optimization method based on Design of Experiment、Kriging model and genetic algorithm developed in the Matlab environment of thispaper which is applied in the design optimization of grid fins successfully.In chapter6three aspects of innovational study of grid fins are performedincluding the study of increasing lift-drag coefficient by drilled on the wall of grid fins,the study of grid fins in the application to reduce the induced drag of wing and the study of the curved grid fins.In chapter7, the conclusions of the work are summarized in general, and the futureresearch direction is presented.