对带气室的展弦比为3的不同平面形状翼伞模型的流场进行了三维定常数值模拟,详细考察了平面形状对翼伞气动性能的影响。运用有限体积法对三维坐标系下不可压雷诺时均Navier-Stokes(RANS)方程进行了直接求解,采用剪切应力输运(SST)k-ω二方程湍流模型进行湍流模拟。数值模拟得出的原始翼伞的气动性能参数与试验数据在总趋势上符合很好,多种平面形状的翼伞模型计算结果表明:椭圆形翼伞模型获得最小阻力系数,前缘切口改变了上下缘流态使其升力系数并非最大;前缘后掠能明显减小翼伞阻力;由于翼伞中部区域对有效升力贡献更大,前缘后掠的翼伞模型获得最大升阻比;阻力对翼伞升阻比影响很大,前缘切口阻力是总阻力的主要来源之一,且是一种二维效应的阻力。该文可为进一步研究更多不同几何参数的翼伞模型提供参考。
3D steady flow fields of parafoils with cells, an aspect ratio of 3.0, and different planform geometries are numerically simulated by using a computational fluid dynamics (CFD) technique to study the planform geometry effect on parafoil aerodynamic performance. The incompressible Reynolds-averaged Navier-Stokes (RANS) equation in a three-dimensional coordinate system is solved by using the finite volume method. The shear stress transport (SST) k-ω two-equation turbulent model is also applied to simulate the turbulence. Numerical simulation results of the aerodynamic performance of the original model show good agreement with the tunnel experimental data. The results indicate that the elliptical parafoil model achieves the minimal drag coefficient among all the models, because the leading edge cut has changed the flow state, so that its lift coefficient is not the maximum. The swept back leading edge can obviously decrease the drag of a parafoil model. Because the middle part of a parafoil contributes more to effective lift, the model with a swept back leading edge achieves the maximal lift-drag ratio. Drag has a great impact on the lift-drag ratio, and the leading edge cut drag, which has only a two-dimensional effect, is one of the main sources of the total drag. This paper can provide reference for further studies on parafoil aerodynamic performance with different geometric parameters.
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