Abstract A numerical simulation of a rectangular surface jet is performed at a Reynolds number of Re j = 4400 . The global parameters of the jet e.g. maximum velocity decay, jet surface normal and lateral spread rates, entrainment, jet momentum flux and turbulent momentum flux are in agreement with several other studies reported in the literature. It is shown that the mean velocity and Reynolds stress profiles scale with the maximum local streamwise velocity and jet half width in the surface normal and lateral directions. The current simulation provides balance, explicitly calculated budgets for the turbulence kinetic energy, Reynolds normal and shear stresses. The surface jet develops a thin layer of fast moving fluid in the lateral direction near the surface. This layer is called the ‘surface current’. It has been suggested that the surface current arises due to the Reynolds stress anisotropy in the near surface region. The current study shows that this explanation is incomplete. The turbulence production for the Reynolds stress in the lateral direction is negative, which can drive the mean flow in the lateral direction. The higher level of negative production in the near surface region is responsible for the development of the surface current.

中文翻译：

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沿无剪切边界的矩形射流的数值研究：表面射流

摘要 对雷诺数Re j = 4400 的矩形面射流进行了数值模拟。射流的全局参数，例如最大速度衰减、射流表面法向和横向扩展率、夹带、射流动量通量和湍流动量通量与文献中报道的其他几项研究一致。结果表明，平均速度和雷诺应力分布与表面法向和横向上的最大局部流向速度和射流半宽度成比例。当前的模拟为湍流动能、雷诺法向应力和剪切应力提供了平衡、明确计算的预算。地表射流在靠近地表的横向方向上形成一薄层快速移动的流体。这一层被称为“表面电流”。有人提出表面电流是由于近表面区域的雷诺应力各向异性引起的。目前的研究表明，这种解释是不完整的。横向雷诺应力的湍流产生为负，可以驱动横向平均流动。近地表区域较高水平的负产生是造成地表电流发展的原因。