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混合层强化混合的数值研究 总被引:2,自引:0,他引:2
受 Wang & Fiedler(1997)的实验的启发,采用高阶精度的差分格式,通过数值模拟的方法,研究了二维混合层及限于两平板间的二维混合层(二维受限混合层)入口处加振动对提高混合层混合效率的作用.计算结果表明:对二维混合层,振动的频率越低,在混合层中产生的大尺度涡结构的尺度越大,在频率很低时,涡具有相似性;对限于两平板间的二维混合层,在一定的振动频率下,混合层中产生的涡较大而且破碎得也较好,这将有利于混合.这一结论与 Wang & Fiedler(1997)的实验观测到的结果是一致的. 相似文献
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Numerical Investigation on Inviscid Instability of Streaky Structures in Incompressible Boundary Layer Flow 下载免费PDF全文
Numerical investigation is made on the effect of streaky structures in transition by inviscid linear disturbance equation with temporal mode. Several disturbances with different streamwise wave numbers were induced, and the evolutions with time step were received. It suggests that the exponential growth and periodic variation of the waves are in existence. As the streamwise wave number increases, the disturbance growth rate begins by increasing, reaches a maximum at around α=0.4 with a disturbance frequency of 0.2186 + 0.001457i, and then decreases. Furthermore, the eigenfunctions of pressure disturbance are plotted. 相似文献
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Mechanism of transition in a hypersonic sharp cone boundary layer with zero angle of attack 总被引:2,自引:0,他引:2
Firstly, the steady laminar flow field of a hypersonic sharp cone boundary layer with zero angle of attack was computed.Then,two groups of finite amplitude T-S wave disturbances were introduced at the entrance of the computational field,and the spatial mode transition process was studied by direct numerical simulation (DNS) method. The mechanism of the transition process was analyzed.It was found that the change of the stability characteristics of the mean flow profile was the key issue.Furthermore,the characteristics of evolution for the disturbances of different modes in the hypersonic sharp cone boundary layer were discussed. 相似文献
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超音速混合层的流动不稳定性较之亚音速或不可压的混合层大大减弱,为了提高混合效率,
通过数值模拟的方法分别研究了展向曲率、展向速度、来流马赫数等因素对混合效率所
起的作用. 计算结果表明:在给定展向速度的情况下,带有展向曲率的三维混合层,曲率越
大三维扰动增长率越大,而且法向的卷起范围也越大. 当展向曲率不为零时,展向速度的增
大也能有效地增强混合能力. 由流场中的高频扰动波产生的涡,在向下游发展过程中会有破
碎、拉伸,低频扰动波没有发现这一现象. 对于有展向曲率和展向速度的混合层,提高来流
马赫数时,流场中最不稳定扰动的增长率仍很大. 因此,这是一种提高混合层混合效率的新
途径. 相似文献
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求解扰动速度幅值的演化规律,是流动稳定性非线性理论的关键问题之一。现有的方法都只能用于准中性的情况,或其中有一定的人为因素。本文将给出解决这一问题新方法。 相似文献
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Direct numerical simulations are carried out with different disturbance forms introduced into the inlet of a flat plate boundary layer with the Mach number 4.5. According to the biorthogonal eigenfunction system of the linearized Navier-Stokes equations and the adjoint equations, the decomposition of the direct numerical simulation results into the discrete normal mode is easily realized. The decomposition coefficients can be solved by doing the inner product between the numerical results and the eigenfunctions of the adjoint equations. For the quadratic polynomial eigenvalue problem, the inner product operator is given in a simple form, and it is extended to an Nth-degree polynomial eigenvalue problem. The examples illustrate that the simplified mode decomposition is available to analyze direct numerical simulation results. 相似文献
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先计算出高超音速零攻角尖锥边界层的定常层流流场.然后在计算域的入口引入两组有限幅值的T-S波扰动,对空间模式的转捩过程进行了直接数值模拟.分析了转捩过程的机理,发现平均流剖面稳定性的变化是其关键.并进一步讨论了不同模态初始扰动在高超音速尖锥边界层中的演化规律. 相似文献
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