Spatial Scaling of Large-Scale Circulations and Heat Transport in Turbulent Mixed Convection

by Andreas Westhoff
Doctoral thesis
Date of Examination:2012-11-14
Date of issue:2013-02-18
Advisor:Prof. Dr. Dr. Andreas Dillmann
Referee:Prof. Dr. Andreas Dillmann
Referee:Prof. Dr. Andreas Tilgner
Persistent Address: http://dx.doi.org/10.53846/goediss-3733

 

 

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Abstract

English

The present study reports an experimental investigation of the scaling of large-scale coherent structures, their dynamics and heat transport in turbulent mixed convection. Based on a concept of spatial scaling, mixed convective air flow was examined by particle image velocimetry and temperature measurements in two rectangular containers with the same geometry and similar characteristic numbers. The dimensions of the container are scaled by a factor five. Due to the unsteady nature of mixed convection in the present configuration and parameter range, the instantaneous velocity vector fields are subjected to a proper orthogonal decomposition and a vortex detecting algorithm in order to identify the predominant coherent structures and their dynamics. It was found that mixed convection is far from equilibrium and comprises numerous of flow states; depending on the ratio of inertia to buoyancy forces. In addition, the study reveals a strong correlation between the dynamics of the large-scale coherent structures and the transport of heat. Based on these characteristic features, mixed convection was examined for similitude of the predominant coherent structures and for kinematic similitude. A good accordance of the topology of the large-scale structures and their dynamics was found.
Keywords: mixed convection; scaling; coherent structures; heat transfer; low frequency dynamics; particle image velocimetry; proper orthogonal decomposition
 
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