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FLUID MECHANICS

机译：流体力学

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Nominally zero-pressure-gradient fully developed flat-plate turbulent boundary layers with heated and unheated isothermal walls at supercritical pressures are studied by solving the full compressible Navier-Stokes equations using direct numerical simulation. With a heated isothermal wall, the wall temperature sets such that the flow temperature varies through the pseudo-critical temperature, and thus pseudo-boiling phenomena occur within the boundary layers. The pseudo-boiling process induces strongly nonlinear real-fluid effects in the flow and interacts with near-wall turbulence. The peculiar abrupt density variations through the pseudo-boiling process induce significant near-wall density fluctuations within the heated transcritical turbulent boundary layers. The large near-wall density fluctuations induce a turbulent mass flux . and the turbulent mass flux amplifies the Favre-averaged velocity fluctuations in the near-wall predominant structures of streamwise low-speed streaks that are associated with the ejection (where ), while reducing the velocity fluctuations in the high-speed streaks associated with the sweep (u' > 0 and v' 0). Although the near-wall low-speed and highspeed streak structures dominate the Reynolds-shear-stress generation, the energized Favre-averaged velocity fluctuations in the low-speed streaks enhance both the mean-density- and density-fluctuation-related Reynolds shear stresses ( and ) in the ejection event and, as a result, alter the Reynolds-shear-stress profile. The large density fluctuations also alter the near-wall viscous-stress profile and induce a near-wall convective flux (due to non-zero ). The changes in the contributions in the stress-balance equation result in a failure of existing velocity transformations to collapse to the universal law of the wall. The large density fluctuations also greatly contribute to the turbulent kinetic energy budget, and especially the mass flux contribution term becomes noticeable as one of the main positive terms. The unheated non-transcritical turbulent boundary layers show a negligible contribution of the real-fluid effects, and the turbulence statistics agree well with the statistics of an incompressible constant-property turbulent boundary layer with a perfect-gas law.
机译：通过使用直接数值模拟解决全部可压缩的Navier-Stokes方程，研究了标称零压力梯度完全开发的具有加热和未加热的等温壁的平板湍流边界层，采用直接数值模拟来研究全部压缩Navier-Stokes方程。通过加热的等温壁，壁温设置使得流量温度通过伪临界温度变化，因此在边界层内发生伪沸腾现象。伪沸腾的方法在流动中诱导强烈的非线性实际液体效应并与近壁湍流相互作用。通过伪沸腾过程的特殊突然密度变化在加热的跨临界湍流边界层内引起显着的近壁密度波动。大的近壁密度波动诱导湍流质量磁通量。湍流质量磁通放大了与喷射（其中）相关的流动低速条纹的近壁主导结构中的近壁上的速度波动的速度平均速度波动，同时减少与扫描相关联的高速条纹中的速度波动（U'> 0和V'0）。虽然近壁的低速和高速条纹结构占主导地位雷诺 - 剪切应力产生，但低速条纹中的通电的Favre平均速度波动增强了平均密度和密度波动相关的雷诺剪切应力（和）在弹出事件中，因此改变了雷诺 - 剪切应力分布。大密度波动也改变了近壁粘性应力型材，并诱导近壁的对流助焊剂（由于非零）。压力平衡方程的贡献的变化导致现有速度变换失败以崩溃到墙壁的普遍规律。大密度波动也大大促进了动荡的动能预算，特别是质量助焊剂贡献期作为主要阳性术语之一变得显着。未加热的非跨临界湍流边界层显示出真实流体效应的贡献可忽略不计，并且湍流统计数据与具有完美气体法的不可压缩的恒定性湍流边界层的统计数据吻合。

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    《Oceanographic Literature Review》 |2019年第4期|933-945|共13页
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