Experimental Investigation and control of turbulent flow structures in mixed convection in a small-scale model experiment

房间和客舱空调的目的是为居住者提供舒适的内饰和有效的能源利用。为了表征室内气候，室内空气的流速和温度非常重要。封闭空间（办公室、报告厅、音乐厅、车辆和飞机机舱）的气流主要以混合对流为特征，混合对流是由复杂的空调系统实现的。物质和能量的输运以温差和送风速度为边界条件。因此，混合对流可以理解为自然对流和强迫对流在空间和时间上的叠加。虽然总体上紊流很强，但速度场和温度场排列在大尺度的相干结构中，即所谓的大尺度环流（LSC）。这些显著特征的材料和能源的运输，这反过来是至关重要的室内空气质量的评估。一些实验表明，这些LSCs具有尖锐边界的尖锐过渡。这些大尺度环流的结构强烈依赖于瑞利数（Ra）、雷诺数（Re）和阿基米德数（Ar）。现有的实验研究表明，随着关键参数的变化，结构会出现明显的不连续过渡，这不利于室内空气质量的预测。已建立的模型只是部分地或根本没有考虑到这方面。在研究项目中，这些结构转变将被研究。

The aim of the room and passenger cabin air conditioning is to provide the occupants comfortably tempered interiors with efficient energy use. To characterize the indoor climate, flow velocity and temperature of the room air are of great importance. Airflows in enclosed spaces (offices, lecture halls, concert halls, vehicle and aircraft cabins) are mainly characterized by mixed convection, which is realized by complex air conditioning systems. The material and energy transport is characterized by temperature difference and supply air velocity, which are boundary conditions. Mixed convection can therefore be understood as a spatial and temporal superimposition of natural and forced convection. Although highly turbulent in general, the velocity and temperature field is arranged in large-scale coherent structures, the so-called large-scale circulation (LSC). These significantly characterize the transport of material and energy, which in turn is crucial for the assessment of indoor air quality. It has been shown in some experiments that these LSCs have sharp transitions with sharp boundaries. The structures of these large-scale circulation flows are strongly dependent on Rayleigh number (Ra), Reynolds number (Re) and Archimedes number (Ar). Existing experimental studies show sharp discontinuous structure transitions with variation of the key parameters, which prevents predictions of indoor air quality. Established models take into account this aspect only partially or not at all. In the research project, these structure transitions will be investigated.