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Friday, 14. December 2018
 

Experimental investigations of structure formation in turbulent mixed convective duct flows

Convective flows in rectangular ducts are of interest in many applications. The must obvious examples are the flow through heat exchangers or in cooling devices. The principle found in many industrial applications is forced channel flow heated from below, which is characterized by the interaction of buoyancy with a pressure-driven flow leading to complex three-dimensional and often turbulent mixed convection. A further complication arises from the temperature dependency of the fluid properties. Due to the complexity of this mutual interaction of the buoyancy-driven and forced flow the physical mechanisms involved are up to now not fully understood.  
At the DLR Göttingen a generic heat exchanger channel has been developed in order to study the formation and dynamics of buoyancy induced flow structures and their influence on the forced flow. The partially transparent duct allows for optical flow measurement e.g. Particle Image Velocimetry, Schlieren photography or Laser Doppler Anemometry. In addition the apparatus is equipped with temperature sensors in order to study the flow structure dynamics and transport of heat as a function of the ratio of buoyancy to inertia forces, the aspect ratio of the duct and the fluid properties. 

The experimental set up for a studies of mixed convection in a water filled rectangular duct by means of PIV.
By PIV results calculated spatial distribution of the probability of the thermal convection roll centre position. Red und yellow indicates regions where the role centre is preferred located.

Contact:

Dr. rer. nat. Andreas Westhoff
German Aerospace Center (DLR)
Institute of Aerodynamics and Flow Technology, Department Ground Vehicles
Göttingen
Phone: +49 551 709-2294

 
German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, SCART
Bunsenstraße 10, 37075 Göttingen, Germany