An investigation of eddy diffusivities of momentum and heat in circular pipes.
The theoretical analysis of the present work was based on a thermodynamic approach, using the method of inference. An analysis was made to find the macroscopic turbulence transport properties from the description of microscopic behaviour of entities of varying shape, size and velocity. Momentum and energy trans port in a turbulent fluid were investigated and expressions for the eddy diffusivities of momentum and heat proposed. Communication theory has been success: fully used as a means for the interpretation of turbulence parameters. Velocity profiles in simple shear flows, obtained with the present analysis, were compared with those found by others, both experimentally and theoretically. An overall heat transfer similarity parameter was derived with the assumption of a constant turbulent Prandtl number. Measurement of mean velocity, microscale, turbulence intensity and eddy diffusivities of momentum and heat were obtained in a water tunnel Results were obtained for Reynolds numbers from 2 x 10 5 to 9 x 10 5. Pipes were roughened internally with paint mixed with fine particles and roughness ratio r/k ranging between 7.2 x 10 3 and 2.5 x l0 5 with absolute roughness height between 4um and 10um. In the light of the present analysis, it is concluded that the new and more realistic approach to turbulence phenomenon is a useful concept for predicting turbulence transport properties, as well as heat transfer characteristics of a simple shear flow.
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