Comparison of performance of simplified RANS formulations for velocity distributions against full 3D RANS model

Alawadi, WAAK; Prasad, TD

Abstract

Several analytical models of velocity distribution for turbulent uniform open channel flows were lately developed by analysis and simplification of the Reynolds-averaged Navier-Stokes equations (RANS). These simplified RANS-based models, which are called dip-modified laws, are frequently employed to predict the velocity profile in flow cases where the maximum velocity may occur below the water surface. In this paper, the performance of two simplified RANS models, namely the dip-modified log law (DML-law) and the dip-modified log wake law (DMLW-law) are compared against the full 3D RANS model used in the computational fluid dynamics (CFD) modelling. The results show that although the simplified RANS models can predict the velocity dip phenomenon, the accuracy of such models is less than the full RANS (CFD) model. This is likely to be due to the assumption imposed for approximating the secondary current term in the governing equations. It is also found that the DMLW-law can give results closer to that obtained by the full RANS model. This may because of including the wake effect in eddy viscosity calculation

Citation

Alawadi, W., & Prasad, T. (2018). Comparison of performance of simplified RANS formulations for velocity distributions against full 3D RANS model. International journal of hydraulic engineering (Online), 7(2), 33-42. https://doi.org/10.5923/j.ijhe.20180702.03

• Journal Article Type: Article
• Publication Date: Jan 1, 2018
• Deposit Date: Dec 23, 2019
• Publicly Available Date: Dec 23, 2019
• Journal: International Journal of Hydraulic Engineering
• Print ISSN: 2169-9771
• Electronic ISSN: 2169-9801
• Volume: 7
• Issue: 2
• Pages: 33-42
• DOI: https://doi.org/10.5923/j.ijhe.20180702.03
• Publisher URL: http://dx.doi.org/10.5923/j.ijhe.20180702.03
• Related Public URLs: http://www.sapub.org/journal/articles.aspx?journalid=1062