Optimising transport in shear flows over heterogeneous rough walls

大多数的工程和环境流的发展空间异质粗糙表面，在地形的表面包含各种各样的长度尺度。最近的研究指出，强大的二次流发展在剪切流在这些表面上，修改整个剪切层的运输。然而，仍有几个悬而未决的问题。例如，目前尚不清楚这些水流形成的主导长度尺度是多少，也不清楚这些结构的形成是否在不同的水流中具有普遍性。同样缺乏的是"工程师"最佳粗糙表面的工具和理解，例如，最大化传输特性，以实现例如最大热传递或最小阻力。在这个项目中，我们将首先开发一个基于RANS建模和伴随方程的计算框架，这将使我们能够设计具有最佳属性的异质表面。其次，将进行最佳表面的补充DNS，以详细了解二次电流的产生机制。

A majority of engineering and environmental flows develops over spatially heterogeneous rough surfaces, where the topography of the surface contains a wide variety of length scales. Recent investigations have pointed out that strong secondary currents develop in shear flows over these surfaces, modifying the transport across the shear layer. However, there remain several open questions. For instance, it is not clear what is the leading length scale for the formation of these currents, nor if the formation of these structures is universal across different flows. What is also lacking are tools and understanding to ''engineer'' optimal rough surfaces that, e.g., maximize transport properties, to achieve, e.g. maximum heat transfer or minimum drag. In this project, we will first develop a computational framework based on RANS modelling and adjoint equations that will allow us to design heterogeneous surfaces with optimal attributes. Secondly, complementary DNS of the optimal surfaces will be performed to develop a detailed understanding of the generation mechanisms of secondary currents.