Experimental facility for velocity measurements in a turbulent wall jet

在工业或环境应用中遇到的大多数流动都是湍流，也就是说，它们的特征是与速度场明显随机的小范围波动相关的混合水平增强。这是所谓的物理系统混沌行为的一个例子。虽然湍流本身很难理解，但它有许多重要的实际应用，包括增加表面摩擦阻力（例如飞机）和增加壁面传热率（例如热交换器）。在大气和水圈中，湍流是污染物迅速稀释的原因。为了改进流动系统的设计或减轻对环境的不利影响，工程师需要更好地了解湍流及其相关的运输。

Most flows encountered in industrial or environmental applications are turbulent, which is to say that they are characterised by enhanced levels of mixing associated with apparently random small-scale fluctuations of the velocity field. This is one example of so-called chaotic behaviour of a physical system. Although inherently difficult to understand, turbulence has many important practical applications including increasd skin friction drag (e.g. for aircraft) and increased wall heat transfer rates (e.g. for heat exhcangers.) In the atmosphere and hydrosphere, turbulence is responsible for the rapid dilution of contaminants. In order to improve the design of flow systems or mitigate adverse environmental impacts, engineers need to better understand turbulence and the associated transport.