Upstream Blocking and Airflow Over Mountains
Upstream Blocking and Airflow Over Mountains
复制标题
DOI：
10.1146/annurev.fl.19.010187.000451
复制
发表时间：
1987
影响因子：
27.7
通讯作者：
P. Baines
中科院分区：
文献类型：
--
作者：
P. Baines
）高度为 h 的障碍物，那么朴素的能量论证（和常识）表明，如果 Nh/U 足够大，靠近地面的流体将被阻挡在上游侧，并且不会流过障碍物。偶然的观察和“民间传说”早已表明这种现象在大气层中的山脉附近很常见。然而，其发生的本质和机制直到最近才变得清晰。现在已知，大雷诺数流中的上游阻塞以波现象的形式传播，由地形上的非线性效应产生。根据具体情况，这些波可能是线性的或非线性的，它们主要以“柱状”运动的形式传播，这意味着它们在穿过障碍物前面的流体时会永久改变密度和水平速度分布。当这些变化达到足够的幅度时就会发生阻塞。由于它们改变了上游条件，因此无论流动的其他细节如何，了解障碍物引起的这些上游扰动是计算障碍物上稳态流的先决条件。这些效应通常取决于具有足够大高度的近似二维 (2D) 的形貌。它们在峡湾、河口和大气等地球物理环境中很常见。由于阻塞主要是一种二维分层现象，因此在本次综述中我们排除了旋转的影响并关注
)obstacle of height h, then naive energy arguments (and common sense) indicate that if Nh/U is sufficiently large, fluid near the ground would be blocked on the upstream side and not flow over the obstacle. Casual observations and "folklore" have long indicated that this phenomenon is common near mountain ranges in the atmosphere. However, the nature and mechanics of how it occurs have only recently become clear. It is now known that upstream blocking in large-Reynolds number flows propagates as a wave phenomenon, generated by nonlinear effects over the topography. These waves may be linear or nonlinear depending on circumstances, and they propagate primarily as "columnar" motions, meaning that they permanently alter the density and horizontal velocity profiles as they pass through the fluid ahead of the obstacle. Blocking occurs when these changes reach sufficient amplitude. Since they alter the upstream conditions, the understanding of these upstream dis turbances caused by the obstacle is a prerequisite for calculating the steady state flow over an obstacle, regardless of the other details of the flow. These effects generally depend on the topography being approximately two-dimensional (2D) with sufficiently large height. They are common in geophysical situations such as fjords, estuaries, and in the atmosphere. Since blocking is primarily a two-dimensional stratified phenomenon, in this review we exclude the effects of rotation and are concerned with