基于大涡模拟的平流层浮空器气动特性分析
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摘要
为研究不同球体间距对"球形囊体型"平流层浮空器(SLV)气动特性的影响,采用有限体格式、结构网格和大涡模拟(LES)计算方法求解不可压缩的Navier-Stokes(NS)方程,对超临界雷诺数"球形囊体型"平流层浮空器绕流进行数值模拟,并对不同球体间距下的数值计算结果进行详细的分析比较.通过对比试验数据,单球体数值模拟的阻力系数时均值与Achenbach的试验数据一致,验证了计算方法分析超临界雷诺数球体绕流问题的准确性.研究不同间距的双球体阻力变化规律以及振动频谱特性,随上下游球体间距G的增加,合阻力先增大后减小,上游球体的阻力占优振动频率逐渐减小;G=1.5D(D为球体直径)和G=2D时,上下游球体有相同的占优振动频率.随间距G的增加,两球体相互作用与上游球体对下游球体的尾涡结构影响逐渐减弱.
Flowing over stratospheric lighter-than-air vehicle( SLV) with spherical capsule shape at supercritical Reynolds number were simulated by using large eddy simulation( LES) method. Meanwhile,the results at different sphere spacing were analyzed and compared so that the influence of different sphere spacing on stratospheric lighter-than-air vehicle's aerodynamic characteristics was obtained. Compared with the results of the experiments,the calculations of time-average drag coefficients agreed well with Achenbach's experimental results in the single sphere. The method was verified accurate on the analysis of flow over spheres at supercritical Reynolds number. The drag coefficients of the two spheres at different sphere spacing and frequency spectrum were studied. With the increase of the upstream and downstream spheres 'spacing,the whole drags increased first,then decreased,and the the dominant frequencies of upstream sphere decreased.The upstream and downstream spheres had the same dominant frequency of vibration when the spheres' spacing were G = 1. 5D and G = 2D. With the increasing of G,the interaction between the two spheres and the influence of upstream sphere's trailing vortex to downstream sphere's trailing vortex waned.
Flowing over stratospheric lighter-than-air vehicle( SLV) with spherical capsule shape at supercritical Reynolds number were simulated by using large eddy simulation( LES) method. Meanwhile,the results at different sphere spacing were analyzed and compared so that the influence of different sphere spacing on stratospheric lighter-than-air vehicle's aerodynamic characteristics was obtained. Compared with the results of the experiments,the calculations of time-average drag coefficients agreed well with Achenbach's experimental results in the single sphere. The method was verified accurate on the analysis of flow over spheres at supercritical Reynolds number. The drag coefficients of the two spheres at different sphere spacing and frequency spectrum were studied. With the increase of the upstream and downstream spheres 'spacing,the whole drags increased first,then decreased,and the the dominant frequencies of upstream sphere decreased.The upstream and downstream spheres had the same dominant frequency of vibration when the spheres' spacing were G = 1. 5D and G = 2D. With the increasing of G,the interaction between the two spheres and the influence of upstream sphere's trailing vortex to downstream sphere's trailing vortex waned.
引文
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[2]Volpe J.Lockheed Martin’s HALE-D airship learns to fly makes a crash landing[EB/OL].(2011-07-28).http://www.engadget.com/2011/07/28/lockheed-martins-hale-d-airship-learns-tofly-makes-a-crash-la/.
[3]Sakamoto H,Haniu H.A study on vortex shedding from spheres in a uniform flow[J].Journal of Fluids Engineering,1990,112(4):386-392.
[4]Constantinescu G,Squires K.Numerical investigations of flow over a sphere in the subcritical and supercritical regimes[J].Physics of Fluids,2004,16(5):1449-1466.
[5]Rodriguez I,Lehmkuhl O,Borrell R,et al.Flow dynamics in the turbulent wake of a sphere at sub-critical Reynolds numbers[J].Computers&Fluids,2013,80:233-243.
[6]Moradian N,Ting D S K,Cheng S.The effects of freestream turbulence on the drag coefficient of a sphere[J].Experimental Thermal and Fluid Science,2009,33(3):460-471.
[7]Hassanzadeh R,Sahin B,Ozgoren M.Numerical investigation of flow around a sphere[J].International Journal of Computational Fluid Dynamics,2011,25(10):535-545.
[8]Hassanzadeh R,Sahin B,Ozgoren M.Large eddy simulation of flow around two side-by-side spheres[J].Journal of Mechanical Science and Technology,2013,27(7):1971-1979.
[9]Pinar E,Sahin B,Ozgoren M,et al.Experimental study of flow structures around side-by-side spheres[J].Industrial and Engineering Chemistry Research,2013,52(40):14492-14503.
[10]邹建峰,任安禄,邓见.圆球绕流场的尾涡分析和升阻力研究[J].空气动力学学报,2004,22(3):303-308.Zou J F,Ren A L,Deng J.Numerical investigations of wake and force for flow past a sphere[J].Acta Aerodynamica Sinica,2004,22(3):303-308(in Chinese).
[11]任安禄,李广望,邹建峰.中等雷诺数圆球绕流的数值研究[J].浙江大学学报,2004,38(5):644-648.Ren A L,Li G W,Zou J F.Numerical study of uniform flow over sphere at intermediate Reynolds numbers[J].Journal of Zhejiang University,2004,38(5):644-648(in Chinese).
[12]邹建锋,任安禄.串列双圆球的流场转捩研究[J].浙江大学学报,2006,40(1):107-112.Zou J F,Ren A L.Study on transitions for flow past two spheres in tandem arrangement[J].Journal of Zhejiang University,2006,40(1):107-112(in Chinese).
[13]Germano M,Piomelli U,Moin P,et al.A dynamic subgrid-scale eddy viscosity model[J].Physics of Fluids A:Fluid Dynamics(1989-1993),1991,3(7):1760-1765.
[14]Wilcox D C.Turbulence modeling for CFD[M].2nd ed.La Caflada,CA:DCW Industries,Inc.,1998.
[15]Achenbach E.Experiments on the flow past spheres at very high Reynolds numbers[J].Journal of Fluid Mechanics,1972,54(3):565-575.
[16]Jeong J,Hussain F.On the identification of a vortex[J].Journal of Fluid Mechanics,1995,285:69-94.