内外流一体化气动热模拟一致性研究

The aerodynamic heating consistency study between CFD and experiment for air-breathing integrated vehicle

  • 摘要: 以内外流一体化设计的飞行器为研究对象,对比分析了内外流场气动热仿真和风洞试验的一致性,定量分析了气动热仿真与风洞试验之间的差异,并研究了产生差异的原因。气动热仿真采用有限体积法求解Navier−Stokes方程,湍流模型为SA,空间格式为Roe的FDS,时间格式为LU−SGS。在FD−20a激波风洞中开展风洞试验,来流马赫数6,单位雷诺数1.14 × 107~2.98 × 107 m−1,迎角0°~8°。仿真与试验的对比结果表明:沿流向流动干扰复杂程度增大,热流模拟一致性降低;压缩面流动以附着流和小分离为主,仿真与试验一致性较好,平均差异约22.3%;在分离与激波边界层干扰等作用下,与压缩面相比,内流的仿真与试验差异增大,其中喉道平均差异约43.5%,隔离段平均差异约31.8%。受Edney型激波干扰的作用,唇口的仿真与试验在三维空间分布上的最大差异达到100%。从网格、数值方法、非定常特性和不确定度评估等方面,归纳总结了沿流向气动热仿真与试验差异增大的原因。

     

    Abstract: In order to improve the accuracy of simulation and obtain the aerodynamic heating consistency of the prediction method for the typical integrated design of the aircraft forebody model, experiments were carried out at FD−20a shock tunnel under the condition of Ma = 6, Re = 1.14 × 107~2.98 × 107 m−1, α = 0°~8°. Numerical simulations were applied through the compressible Navier−Stokes equation implemented with the finite volume method, Roe’s flux difference splitting scheme, LU−SGS spatial method and Spalart–Allmaras (SA) turbulence model. Simulation results were compared with the experimental data to validate the prediction methods. Results show that with the increase of the complexity and disturbance intensity, the heat flux consistency decreases. The compression surface flow was dominated by the attached flow and small separation, where relative good consistency was found between the simulation and experimental data with the average difference being about 22.3%. The throat boundary layer was interfered by shock waves, and 43.5% difference was found between the heat flux simulation and experimental data. The heat flux difference in the isolation section increased to 31.8%. When the oblique shock impinged on the subsonic part of the bow shock and three dimensional flow patterns were obvious, the difference of heat flux reached the maximum of around 100% in three dimensional areas. Mesh, simulation methods and unsteady characteristics are concluded as the reasons for heat flux consistency decreasing along the airflow.

     

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