Kun Ye

Aerodynamic Optimization for Hypersonic Wing Design Based on Local Piston Theory

Optimization of aerodynamic shapes using numerical methods has always been of engineering interest. This paper presents a highly efficient aerodynamic optimization method for hypersonic wings based on local piston theory. The objective of the optimization is to improve the aerodynamic characteristics of original airfoils or wings generated from NACA0012 while satisfying constraints on structure requirements. In the optimization procedure, a genetic algorithm is employed for optimum search, the Hicks–Henne bump function is used for airfoil geometrical modification, and local piston theory is used for unsteady pressure perturbations caused by geometrical modification from the baseline. Because unsteady pressure perturbations at supersonic or hypersonic conditions could be calculated by local piston theory based on initial flowfield results in the optimum searching process, only one steady-state solution without any use of moving or deforming grids is required. Therefore, the optimization method described in...

Effects of structural thermal boundary conditions on hypersonic aerothermoelasticity of all-movable control surface:

Structural thermal boundary conditions are usually simplified in the aerothermoelastic analysis. However, it will influence the heat transfer, the temperature distribution, and the structure stiffness, which have effects on the accurate prediction of the aerothermoelastic characteristics. In this study, an aerothermoelastic framework for hypersonic vehicles is developed, and the effects of structural thermal boundary conditions on aerothermoelasticity of all-movable control surface are investigated. The Reynold’s averaged Navier–Stokes equations are solved by computational fluid dynamics method to obtain the thermal environment. The transient heat transfer, the thermal stress, and the structure mode are analyzed by using finite element method. Finally, the local piston theory is used to calculate the unsteady aerodynamic force, and aeroelastic characteristics are analyzed in the state space. Aerothermoelastic characteristics of three different structural thermal boundaries are investigated in detail, including aerodynamic heating only on control surface; aerodynamic heating on both the control surface and the shaft; and aerodynamic heating on the control surface, the shaft, and the body. The results show that the heat transfer process, the temperature distribution, the thermal stresses, and the natural frequencies of the structure are influenced significantly by structural thermal boundary conditions especially in the shaft. Furthermore, the aerothermoelastic stability margin is affected ultimately.

Effects of aeroelasticity on the performance of hypersonic inlet

Effects of the aeroelasticity on the performance of the hypersonic inlet have been investigated numerically in this study. The aeroelasticity has been simulated using the coupled computational fluid dynamics/computational structural dynamics method, which is solved by the in-house code. The unsteady Reynolds-averaged Navier–Stokes equations have been solved in the computational fluid dynamics simulation, and the modal method has been adopted in the computational structural dynamics simulation. Two cases have been utilized to validate the numerical method. Finally, the aeroelasticity has been simulated for inlet plate with different thicknesses. The effects of aeroelasticity on performance parameters and flow structure have been discussed in detail. The results show that the generalized displacements present the “beat” phenomenon in the time domain. The power spectral density of the generalized displacements implies that the aeroelastic instability is mainly caused by the coupling between the fourth- and fifth-order modes. The time-average flow rate coefficient and pressure rise ratio increase relative to the initial value, while the total pressure recovery coefficient decreases. The fluctuation amplitude of the flow rate coefficient is small, while that of the total pressure recovery coefficient and pressure rise ratio are relatively large. Besides, the phases of the three performance parameters are greatly different. Furthermore, the aeroelasticity has significant effect on the shock wave structure especially at the exit of the inlet.

Study on areothermoelastic for hypersonic all moving control surface

In this paper, the effect of the aerodynamic heating on shaft and the connection between the shaft and the body on areothermoelasticity for hypersonic all moving control surface is studied. A loosely coupled framework on aerothermoelastic stability boundary calculation for hypersonic vehicles is developed. Firstly, based on the computational fluid dynamics (CFD) technology, Navier-Stokes equation is solved to get the thermal environment. Then transient heat transfer of structure is analyzed. After that structural mode is analyzed under the effect of structures thermal stress caused by temperature gradient and material property decrease caused by high temperature. Then structural mode is interpolated to the aerodynamic grids. Finally, Euler equation is solved to get flow parameters, and based on CFD local piston theory, aerothermoelasticity is analyzed in state space. The results show that: the heat transfer process and temperature distribution of the shaft structure are influenced obviously by the effect of the aerodynamic heating on shaft and the connection between the shaft and the body, and natural frequency and flutter characteristics are affected significantly, too. For the model in this paper, the effect of the aerodynamic heating on shaft and the connection between the shaft and the body on aeroelastic stability boundary is 8.31% and 6.87%, respectively.

Aerodynamic optimization for hypersonic airfoil design based on local piston theory

Aerodynamic optimization by numerical methods has always been of engineering interest with the great advancement of computers. This paper presents a highly efficient aerodynamic optimization method for hypersonic airfoil based on local piston theory. In the optimization procedure, local piston theory has been employed for unsteady pressure perturbations caused by geometrical modification from the baseline. Because unsteady pressure perturbations at hypersonic conditions could be calculated by local piston theory based on initial flow field results in the optimum searching process, only one steady-state solution is required. Therefore, the optimization method described in this paper is an extremely efficient technique which combines the advantages of steady CFD and the local piston theory and thus with zero-computational cost in optimum search process. In order to investigate the applicability of local piston theory on aerodynamic prediction for blunt leading edge shape, single-objective and multi-objective optimizations for NACA0008 at various Mach numbers have been conducted with the objective to improve the lift-to-drag ratio and moment coefficient, and the optimization results have been validated by CFD and it is concluded that the optimization method based on local piston theory could be used in a wide Mach range while keeping a satisfactory efficiency and accuracy, therefore it can be employed for hypersonic airfoil optimization in the process of initial design in the engineering application.

A New Design Concept for Wind Turbine Airfoil

Wind energy has been attracting more and more attentions due to its clean and renewable source. The aerodynamic characteristic of wind turbine airfoil directly affects the turbine efficiency. In order to improve the airfoil aerodynamic characteristic, a new concept airfoil configuration for wind turbine is presented. A cave on the upper surface near the trailing edge is designed to generate a trapped vortex in the cave. The trapped vortex is used to stabilize the separated flow when the airfoil at high angle of attack. Combining with the Gurney flap, the airfoil with the cave behaves very good aerodynamic characteristics at wide range of incidences, especially at high angles of attack. The method is used on the well-known FFA-W3-301 turbine airfoil. By using numerical simulation, it is shown that the new airfoil has a higher lift than the original airfoil at the same angle of attack, the stall angle of attack increases from 12 degree to 17 degree, and the maximum lift coefficient increases approximately 64 percents. In addition, the effects of the chord-wise location of starting point of the designed cave are discussed. Therefore, it is believed that the new-designed concept can be investigated and explored further for wind turbine.