Abstract For low "turbulent" Reynolds numbers in strongly-heated vertical gas flow, fundamental results of existing direct numerical simulation (DNS) databases have been examined to deduce differences between cases which "revert" to turbulent and those that yield integral parameters which correspond to laminar flow (henceforth laminarizing or laminarized). Objectives are (1) to examine the streamwise evolution of near-wall flow structures and (2) to determine which, if any, proposed laminarization parameters could be used to discriminate between turbulent and laminarizing flows resulting. Views of streamlines in r-θ cross sections showed evidence of a ring of irregular-shaped streamwise vortices near the wall at all locations. The transverse advection of these vortices is hypothesized to provide a path of least resistance to the transport of streamwise momentum in the wall-normal direction. It is demonstrated that a steady streamwise laminar vortex can provide apparent turbulent momentum transport (as a consequence of the Reynolds decomposition) such that a reasonable mean velocity profile is predicted near the wall. For the present cases, the values of the non-dimensional radius (yc,w+ = Reτ,w) and of the modified wall Reynolds number did discriminate whether turbulent or laminarizing flow resulted.

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关于加热垂直管中“分层”的一些观察

摘要 对于强烈加热的垂直气流中的低“湍流”雷诺数，已经检查了现有直接数值模拟 (DNS) 数据库的基本结果，以推断“恢复”为湍流的情况与产生对应于湍流的积分参数的情况之间的差异。层流（以下称为层流或层流）。目标是 (1) 检查近壁流结构的流向演变和 (2) 确定哪些（如果有）建议的层流参数可用于区分产生的湍流和层流。r-θ 横截面中的流线视图显示了在所有位置靠近壁的不规则形状流向涡旋环的证据。假设这些涡流的横向平流为沿壁法向的流向动量传输提供了阻力最小的路径。结果表明，稳定的流向层流涡旋可以提供明显的湍流动量传输（作为雷诺分解的结果），从而在壁附近预测合理的平均速度剖面。对于目前的情况，无量纲半径 (yc,w+ = Reτ,w) 的值和修改后的壁雷诺数确实区分了是湍流还是层流。结果表明，稳定的流向层流涡旋可以提供明显的湍流动量传输（作为雷诺分解的结果），从而在壁附近预测合理的平均速度剖面。对于目前的情况，无量纲半径 (yc,w+ = Reτ,w) 和修改后的壁雷诺数的值确实区分了是湍流还是层流。结果表明，稳定的流向层流涡旋可以提供明显的湍流动量传输（作为雷诺分解的结果），从而在壁附近预测合理的平均速度剖面。对于目前的情况，无量纲半径 (yc,w+ = Reτ,w) 和修改后的壁雷诺数的值确实区分了是湍流还是层流。