CFD-based Gust Response And Alleviation Research Of Aircraft Wing

Based on unsteady Euler and N-S equations, computational methods of gust response andalleviation are studied in detail, including researches of field velocity approach, gust response inthe time domain for elastic aircraft, gust alleviation simulation method, and reduced order modelof gust response.Based on the field velocity method, a novel approach for simulating unsteady pitching andplunging motion of an airfoil is presented in this paper. Responses to pitching and plungingmotions of the airfoil are simulated under different conditions. The obtained results are comparedwith those of moving grid method. Good agreement is achieved. In the conventional field velocitymethod, the Euler solver is usually used to simulate the movement of the airfoil. However, whenviscous effect is considered, unsteady N-S equations have to be solved and the viscous fluxcorrection must be taken into account. In this work, the viscous flux correction is introduced intothe conventional field velocity method when non-uniform grid speed distribution is occurred.Based on modal theory considering structural vibration, coupled unsteady Euler/N-S equationsand structural equations are solved in time domain. As a result, an integrated time-domain methodfor aerodynamic/structural/gust dynamic response analysis of the coupled system is obtained.Coupled field velocity method with moving grid method, it is easy to perform gust responsetime-domain simulation of unsteady moving free-elastic wing. The unsteady rigid movement andgust of wing are considered by field velocity, while structural vibration is performed by movinggrid method. This provides a simple way to realize gust response of free-elastic wing, whichavoids large mesh deformation.CFD based analysis of coupled Aerodynamic/Structural/gust/control nonlinear system isrealized. Based on time-domain analysis of dynamic gust response, combined with the controlsystem, the gust alleviation numerical simulation in the time domain is realized by control surfacedeflection. Numerical simulations of airfoil and wing show that the aileron gap reduces thealleviation effect of the airfoil. At high Mach number, nonlinear infection is a very important, thealleviation effect of both rigid and elastic wing will reduce.Based on conventional convolution method, a new approach is presented, which involvescomputing sharp-edge gust responses of both generalized aerodynamic forces and gust generalizedaerodynamic forces in a CFD run, computing the gust response due to arbitrary gust profiles viaconvolution. The method is highly computationally efficient, as only one relatively short CFD runis required for the computation of the sharp-edge gust responses, after which responses to arbitrarygust profiles can be computed in seconds.