Print Email Facebook Twitter Development of a Two-Scale Turbulence Model and Its Applications Title Development of a Two-Scale Turbulence Model and Its Applications Author Chen, C.J. Singh, K. Corporate name TU Delft Date 1985-06-01 Abstract The use of second order closure turbulence model in predicting turbulent flows is known to be more successful than the classical mixing length model. However, it is found that if the turbulence constants are not altered or modified, the second order closure turbulence model is unable to predict satisfactorily f or some flows such as round jet and wake flows. In order to improve the predictability of the second order closure model, the present work proposes to consider two turbulent scales in the modelling of turbulent flows. One of these scales is based on using the turbulent kinetic energy, k, and its dissipation rate, epsilon, to characterize the large energy containing eddies. The other scale is based on the dissipation rate and the kinematic viscosity, nie, to characterize the small energy dissipating eddies. The second scale is based on the well known Kolmogorov hypothesis that dissipation of turbulent kinetic energy occurs primarily at small eddies. The turbulence model derived based on the concept of two different scales is called the two-scale turbulence model. The existing turbulence model which is modelled based on the one-scale concept of k and epsilon is called the one-scale turbulence model. The two-scale turbulence model is then applied to predict turbulent free shear flows and recirculating flows. The calculations were done in three parts. The first test case was nonbuoyant free shear flows which included round and plane jets in stagnant and moving streams, plane wakes and mixing layer. In the second part, the model was tested for plane and round buoyant jets having different Froude numbers. Finally, some results were obtained for recirculating flows, namely, backward facing step and flow past an obstruction. It is shown in the present study that the two-scale turbulence model performs significantly better than the one-scale turbulence model in all the cases concerned. The prediction capability of the two-scale turbulence model is shown since one does not need to alter or modify the turbulence constants as in the case of the one-scale turbulence model. Subject turbulenceturbulence modeltwo-scale modelone-scale modelturbulent flowsmodellingjet and wake flowscomputational fluid dynamics Classification EHD1000EHA2000 To reference this document use: http://resolver.tudelft.nl/uuid:18e869f3-cbd9-462e-a64c-be7c16a17e25 Publisher University of Iowa Source IIHR report no. 299 Part of collection Hydraulic Engineering Reports Document type report Rights (c) 1985 University of Iowa Files PDF Chen_Singh1986.pdf 43 MB Close viewer /islandora/object/uuid:18e869f3-cbd9-462e-a64c-be7c16a17e25/datastream/OBJ/view