Abstract
It is well known that Reynolds stresses which are expressed as double correlations of velocity fluctuations are the main controlling factors of momentum-transfer rates in a turbulent field. A universally applicable Reynolds stress model is required in order to describe the flow pattern in a turbulent flow. This study is aimed at making clear the applicability and universality of conventional phenomenological Reynolds stress models.
A two-dimensional turbulence in homogeneous shear flow (Couette flow) being chosen as the simplest turbulent shear flow field, effects of turbulent eddy scales and time-mean velocity gradient on a Reynolds stress were investigated analytically and experimentally. Two conventional representative Reynolds stress models, namely a Kolmogoroff-type model and Bradshaw-type model, were compared with experimental results. The following conclusions were obtained.
i) Where the velocity-gradient of time-mean flow is extremely smaller than that of turbulent eddy, the Kolmogoroff-type model is applicable.
ii) Where the velocity-gradient of time-mean flow approaches that of turbulent eddy, both the Kolmogoroff-type model and the Bradshaw-type model are applicable.
