环帆伞稳降阶段织物透气性影响数值模拟

Numerical simulation of the effect of the permeability on the ringsail parachute in terminal descent stage

为研究织物透气性对降落伞气动性能的影响,将织物的透气性能用Ergun公式描述,建立了含织物透气性能附加源项影响的新型流场动量控制方程,对上述方程进行了数值求解,并和无织物透气性影响的传统模型的数值结果进行了对比。数值结果表明,新型流场动量方程能够得到织物透流速度,该速度明显低于周围有孔出流速度和绕流速度。伞衣尾部存在紧贴伞衣织物的第一尾涡区和尾部中心旋涡对组成的第二尾涡区,织物透气性使第一尾涡区变长,螺旋点增多,旋涡分布更均匀对称,而第二尾涡区尺寸则变小,整个尾涡区变短变窄,提高了伞衣的稳定性。其次,织物透气性使伞衣内侧压力有所降低,外侧负压有所升高,沿伞衣径向压差系数减小,阻力系数小于非透气性伞衣,更接近空投试验结果,该模型可以提高透气性伞衣流场计算的准确性。

For the study of the influence of permeability of fabric on aerodynamic perform-ance of parachute,the permeability of fabric is described by the Ergun equation and introduced into the source term ,establishing a new governing equation of flow momentum with the permea-bility of fabric fully considered .The numerical solution is get and compared with the traditional result,in which the influence of permeability of fabric was ignored.The result shows that the ve-locity penetrating the fabric can be obtained through the new flow field momentum equation and it’s obviously lower than the velocity of the flow through the surrounding holes and that around the parachute.The first wake vortex region which clings to the canopy and the second wake vor-tex region which consists of a pair of center points are in the wake of the canopy,the permeability of fabric makes the first wake vortex region longer,the number of the vortex points increase and the distribution of the vortex more uniform and symmetrical.It also decreases the size of the sec-ond wake vortex,which improves the stability of the canopy through a shorter and narrower whole wake vortex region.Besides,the permeability of fabric decreases the pressure inside the canopy,increases the pressure outside.The pressure coefficient of the canopy in the radial direc-tion decreases,thus,the drag coefficient of the new model is lower than the traditional model, which is closer to the results of the airdrop experiments.Obviously,the new model is significant to improve the accuracy of flow field simulation around the porous canopy.