摘要
分离泡的产生是绕翼型低雷诺数流动的一个重要特征,分离泡通常都是非定常的,会对整个流场产生极大的影响,由于分离附面层的不稳定性,很快诱发转捩,并产生湍流再附。文中通过求解雷诺平均N-S方程,数值模拟了绕Eppler387翼型的低雷诺数非定常流动,并对两方程SSTk-ω湍流模型,代数B-L模型和层流的计算结果作了比较。N-S方程和两方程湍流模型的控制方程非耦合求解,时间推进均采用近似因子方法(AF);空间离散无粘项采用ROE格式,粘性项用中心差分方法计算;计算非定常流场时,采用伪时间子迭代(τt-s)方法保证二阶时间精度,湍流模型计算时都是在固定点转捩。最后分析了转捩对低雷诺数流动的影响、分离泡的存在引起的流动不稳定性和周期性的脱出涡,数值计算给出的时间平均升力系数、阻力系数和压力分布与实验结果比较吻合。
Low-Beynolds-mumber flows over airfoils are characterized by the presence d separation bubbles. The separation bubbles are unsteady and have a significant impact on the overall flow field. The separated boundary layer is unstable and rapidly undergoes transition, and then the turbulent flow reattaches. This paper numerically simulates the unsteady two dimensional low-Reynolds-mumber flow over Eppler387 airfoil with an unsteady Navier-Stokes （N-S） solver dosed by two-equation SST k-ω turbulence model. The N-S equations and two turbulence equations are advanced in time with an implicit approximate-factorization （AF） method and solved uncoupled from each other; the pseudo time sub-iteration （τ-ts） is used for unsteady computations for second-order temporal accuracy. Upwind spatial differencing is used for the inviscid terms, and viscous terms are centrally differenced, the flux difference splitting method of Roe is employed to obtain fluxes at the faces. The unsteady laminar and turbulent calculations with a two-layer algebraic eddy viscosity （B-L） model are also done for comparison; the transition location is fixed for both SST k-ω and B-L turbulence model. An analysis of the numerical solutions show the influence of transition to the overall flow, the unstable of separation bubbles and periodic vortex shedding, the time-averaged lift, drag and pressure coefficients are compared with experimental values and are in good agreement with experimental results.
出处
《空气动力学学报》
EI
CSCD
北大核心
2006年第4期482-486,共5页
Acta Aerodynamica Sinica
