A numerical analysis of free-surface flow in curved open channel with velocity?pressure-free-surface correction

Abstract

This paper presents a numerical study on free-surface flow in curved open channel. An improved SIMPLEC algorithm with velocity-pressure-free-surface coupled correction is developed and validated. Such algorithm differs from the traditional SIMPLEC algorithm and includes three correction equations which are named as the velocity correction equation, the freesurface correction equation derived from the continuity equation with the kinematic boundary conditions on the free-surface and the bottom bed, and the pressure correction equation taking the same formulation as the traditional SIMPLEC algorithm does. In this study, the improved method is used to solve the incompressible, three-dimensional, Reynolds-averaged Navier-Stokes equation set combined with the standard k-e model and/ or the low Reynolds number k-e model for free-surface viscous flow in curved open channels. The power law scheme (POW) is used to discretize the convection terms in these equations with a finite-volume method. The practical cases studied are free-surface flow through the 180 curved open channel with different hydraulic discharge rates. The comparisons between computations and experiments reveal that the model is capable of predicting the detailed velocity field, including changes in secondary motion, the distribution of bed shear, and the variations of flow depth in both the transverse and the longitudinal directions. In summary, the improved SIMPLEC algorithm is feasible and effective for numerical study of free-surface viscous flows in curved open channels.

Experimental and Numerical Study on Velocity Fields and Water Surface Profile in a Strongly-Curved 90° Open Channel Bend

“…Booij (2003) reported the existence of a minor secondary flow at the outer wall and claimed that such flow leads to the local scour at outer wall in the form of wash underneath. Lu et al (2004) applied a threedimensional numerical model to simulate flow pattern at a 180° bend using the standard   k turbulence model. They showed an acceptable agreement between the results obtained from the numerical model and experimental data; but their numerical model was not capable of predicting minor secondary rotational cell in the outer wall.…”

Numerical Modeling of Flow Pattern at a Right-angled River Bend Using CCHE2D Model

“…According to Chang (1984), even for small curves without flow separation, flow resistance or the energy cost caused by transverse flow can be extremely large. Many researchers have studied flow dynamics in a wide variety of channel bend configurations using various methods owing to the major significance of this content (Tominaga and Nagao, 2000;Blanckaert and Graf, 2001;Booij, 2003;Blanckaert and De Vriend, 2004;Lu et al, 2004;Bodnar and Prihoda, 2006;Roca et al, 2007;Blanckaert, 2009;Zhou et al 2009). These studies aim to collect data on flow variables in channel bends and analysis of the results that have provided the knowledge base for understanding the bend flows.…”

Characteristics of Flow Movement in Complex Canal System and Its Influence on Sudden Pollution Accidents

“…At the top of the bend, the longitudinal average velocity distribution is close to a parabola, and the maximum point is below the water surface, and the overall average velocity is large on the top and small on the bottom [3]. erefore, many scholars [4][5][6][7] have studied the movement of secondary flow, the change of water depth in transverse and longitudinal direction, and the distribution of bed shear force in the bend and found that there are multiple vortices in the secondary flow in the continuous bend, and there is a region of secondary flow direction reversal near the riverbed. e secondary flow also affects the redistribution of downstream velocity, and the transport of secondary flow also affects the redistribution of bed shear stress.…”