各向异性网格自适应计算在超燃模拟中的应用

采用各向异性网格自适应求解技术,将其应用于DLR超燃冲压发动机燃烧室中的超燃模拟.开展了3个算例,包括采用滑移壁面条件的燃烧室冷流场模拟、采用无滑移壁面条件的冷流场模拟及采用无滑移壁面条件的反应流模拟.模拟中,各向异性网格自适应计算捕捉到了如激波、射流、边界层、火焰面等具有各向异性特征的大梯度区域,并利用各向异性网格进行了很好的加密.对比利用各向同性网格的初始流场计算,各向异性网格自适应计算使基于滑移条件、无滑移条件的冷流计算及反应流计算的网格单元数量分别下降了36.2%,36.4%和36.8%,有效降低了计算规模,而且流场大梯度区域的计算结果更准确,辨析度更好.结果表明:对于像超燃这类具有各向异性特征的问题,各向异性网格系统比各向同性网格系统有更好的计算效率及准确性,同时也表明基于Mach数场构造的各向异性网格系统可以有效应用于超燃计算. 

Applications of anisotropic unstructured mesh adaption insupersonic combustion simulations

Anisotropic unstructured mesh adaption has been introduced and used in 2-D simulations of supersonic combustion in the DLR (Deutsches Zentrum für Luft-und Raumfahrt) scramjet combustion chamber. Three cases of non-reaction flow simulation with slip wall conditions, non-reaction flow simulation with non-slip wall conditions and reaction flow simulation (with nonslip wall conditions) were carried out. In the calculations, large gradient areas with anisotropic characteristics, such as shockwaves, jet-flows, boundary layers, and flames, were detected and well refined with anisotropic meshes. As a result, compared with the initial simulation using an isotropic mesh, element numbers were reduced by 36.2%, 36.4% and 36.8%, respectively, in case of slip conditions, nonslip conditions and reactions, meanwhile the accuracy and resolution in large gradient areas was even better. The results show high efficiency and high accuracy of anisotropic mesh approach compared with the isotropic mesh, for the problems with significant anisotropic characteristics such as supersonic combustion. It has been demonstrated that Hessian metrics based on Mach numbers can be used to generate anisotropic meshes for the supersonic combustion simulation.