Calculation of steady and unsteady aerodynamic characteristics for ballonets
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摘要: 对于0~20 km范围内不同外形的浮空气囊,采用虚拟压缩方法求解不可压缩非定常N-S(Navier-Stokes)方程,数值模拟了5个高度下气囊的定常和非定常流场.定常状态时,随高度及气囊外形的变化,模拟了气囊气动力及背风区复杂流动分离.结果表明,当气囊厚度率逐渐增大时,其背风区存在复杂的空间流动分离.运用双时间步方法及动网格技术,成功实现了气囊平移或俯仰运动状态下非定常流场的数值模拟.考察了不同的平移方向及速度对气囊非定常气动特性的影响,得到了气囊平移过程中气动力及流场的变化情况.对于气囊的俯仰运动,获得了不同俯仰速度及不同最大俯仰角时气囊的气动力及流场.计算结果表明气囊的非定常运动对其流场和气动力影响显著.Abstract: For ballonets with various shapes at 0~20 km, the incompressible Navier-Stokes(N-S) equations were solved by artificial compressibility approach, and steady and unsteady flow fields around ballonets at five different altitudes were numerically simulated. The ballonet aerodynamic force and the complex flow separation at leeward region with changes of altitude and its shape for the steady condition were simulated. The results show that the complex spatial flow separation exists at leeward region when the ballonet thickness rate increases gradually. The unsteady flow field numerical simulation at translational or pitching motion conditions was performed successfully by applying dual-time method and dynamic grid technology. The effects of translational direction and velocity on ballonet unsteady characteristics were investigated. The variations of aerodynamic force and flow field during the translational process were obtained. For the pitching motion, the ballonet aerodynamic force and flow field at various pitching speeds and maximum angles were achieved. The calculation results show that the ballonet unsteady motion has evident effects on its flow field and aerodynamic force.
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Key words:
- numerical simulation /
- ballonet /
- aerodynamic characteristic /
- flow separation
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