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

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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.