Effect of Gap on the Flow Characteristics in the Wake of a Bluff Body Near a Wall

Effect of Gap on the Flow Characteristics in the Wake of a Bluff Body Near a Wall

G. Nasif R. Balachandar R.M. Barron

University of Windsor, Ontario, Canada

Available online: 
| Citation



A numerical investigation is carried out to evaluate the influence of the gap between the bluff body and the bed on the wake characteristics generated in shallow flows. A sharp-edge bluff body with a fixed gap from the bed is employed in the study,  and the results are compared with the no gap case. A sharp-edged bluff body was chosen to minimize the effect of reynolds number and ensure fixed flow separation points. The transient three-dimensional Navier–Stokes equations are numerically solved using a finite volume approach with the detached eddy simulation  turbulence model. The flow field in this study involves two different fluids, i.e. water and the air above it. The volume of fluid method is used for tracking the free surface separating the water and air. The fluid structures that are generated in the wake are identified using the λ2-criterion. The results reveal that the gap flow will develop a new structure near the bed, which enhances the upwash flow immediately after the submerged jet is about to turn upwards due to the weak hydraulic jump. This structure plays an important role in recovering the free surface to its original shape at a shorter downstream distance from the bluff body than when there is no gap.


free surface, Navier–Stokes equation, numerical simulation, turbulent models, two-phase flow, viscous flow, wake flow, wall jet


[1] Dey, S., Lodh, R. & Sarkar, S., Turbulence characteristics in wall-wake flows downstream of wall-mounted and near-wall horizontal cylinders. Environmental Fluid Mechanics, 18(4), pp. 1–31, 2018.

[2] Panigrahi, P.K., PIV investigation of flow behind surface mounted detached square cylinder. Journal of Fluids Engineering, 131(1), 011202, 2009.

[3] Wang, X.K. & Tan, S.K., Experimental investigation of the interaction between a plane wall jet and a parallel offset jet. Experiments in Fluids, 42(4), pp. 551–562, 2007.

[4] Martinuzzi, R.J., Bailey, S.C.C. & Kopp, G.A., Influence of wall proximity on vortex shedding from a square cylinder. Experiments in Fluids, 34(5), pp. 585–596, 2003.

[5] Taniguchi, S. & Miyakoshi, K., Fluctuating fluid forces acting on a circular cylinder and interference with a plane wall. Experiments in Fluids, 9(4), pp. 197–204, 1990.

[6] Shinneeb, A.M. & Balachandar, R., Effect of gap flow on the shallow wake of a sharpedged bluff body–mean velocity fields. Journal of Turbulence, 17(1), pp. 94–121, 2016.

[7] Shinneeb, A.M. & Balachandar, R., Effect of gap flow on the shallow wake of a sharpedged bluff body–turbulence parameters. Journal of Turbulence, 17(1), pp. 122–155, 2016.

[8] Shinneeb, A.M., Balachandar, R. & Zouhri, K., Effect of gap flow on the shallow wake of a sharp-edged bluff body—Coherent structures. Physics of Fluids, 30(6), 065107, 2018.

[9] CD-adapco, STAR-CCM+ V10.06.009, User Manual, 2015.

[10] Hirt, C.W. & Nichols, B.D., Volume of fluid (VOF) method for the dynamics of free boundaries. Journal of Computational Physics, 39(1), pp. 201–225, 1981.

[11] Muzaferija, S., A two-fluid Navier-Stokes solver to simulate water entry. In Proceedings of 22nd Symposium on Naval Architecture, pp. 638–651, 1999.

[12] Leonard, B.P., The ULTIMATE conservative difference scheme applied to unsteady one-dimensional advection. Computer Methods in Applied Mechanics and Engineering, 88(1), pp. 17–74, 1991.

[13] Spalart, P.R., Comments on the feasibility of LES for wings, and on a hybrid RANS/LES approach. In Proceedings of First AFOSR International Conference on DNS/LES, 1997.

[14] Wilcox, D.C., Simulation of transition with a two-equation turbulence model. AIAA Journal, 32(2), pp. 247–255, 1994.

[15] Wilcox, D.C., Turbulence Modeling for CFD. La Canada, CA: DCW Industries, Vol. 2, pp. 103–217, 1998.

[16] Hoffmann, K. & Chiang, S., Computational Fluid Dynamics, Vol. 3, 4th ed., Engineering Education System, Wichita, KS, USA, 2000.

[17] Nasif, G., Balachandar, R. & Barron, R.M., Influence of bed proximity on the threedimensional characteristics of the wake of a sharp-edged bluff body. Physics of Fluids, 31(2), p. 025116, 2019.

[18] Nasif, G., Barron, R.M. & Balachandar, R., DES evaluation of near-wake characteristics in a shallow flow. Journal of Fluids and Structures, 45, pp. 153–163, 2014.

[19] Nasif, G., Balachandar, R. & Barron, R.M., Characteristics of flow structures in the wake of a bed-mounted bluff body in shallow open channels. Journal of Fluids Engineering, 137(10), 101207, 2015.

[20] Nasif, G., Balachandar, R. & Barron, R.M., Mean characteristics of fluid structures in shallow-wake flows. International Journal of Multiphase Flow, 82, pp. 74–85, 2016.

[21] Maheo, P., Free Surface Turbulent Shear Flow, PhD dissertation, California Institute of Technology, CA, USA, 1999.

[22] Akilli, H. & Rockwell, D., Vortex formation from a cylinder in shallow water. Physics of Fluids, 14(9), pp. 2957–2967, 2002.