Abo Bibliothek: Guest

ISSN Online: 2377-424X

ISBN Print: 0-89116-130-9

International Heat Transfer Conference 6
August, 7-11, 1978, Toronto, Canada

BUOYANCY EFFECT ON EDDY DIFFUSIVITIES IN THERMALLY STRATIFIED FLOW IN AN OPEN CHANNEL

Get access (open in a dialog) DOI: 10.1615/IHTC6.3110
pages 91-96

Abstrakt

This paper presents experimental results on the eddy diffusivities of momentum and heat in thermally stratified flow in an open channel under both stable and unstable conditions to provide some insight into the buoyancy effect on turbulence. The eddy diffusivities of momentum and heat were calculated as a function of position from time-smoothed velocity and temperature profiles measured by a laser Doppler velocimeter and thermocouples. The results in stable stratified flows indicate that the eddy diffusivities of momentum εm and heat εh decrease with stability and that the reciprocal turbulent Prandtl number also decreases with in¬creasing Richardson number Ri, reaching a value of about 0.1 at Ri ~ 1.
Under unstable conditions, εm and εh increase with instability and the reciprocal turbulent Prandtl number increases as the stratification shifts from neutral to weakly unstable conditions but then drops gradually as (−Ri) increases. It has a maximum of about 3 at Ri ~ −0.2 and drops to unity at Ri ~ −10. This behavior is different from other previous atmospheric measurements.