Experimental Study of the Effects of Flow Discharge, Diameter, and Depth on Shear Stress in a Rectangular Channel with Rigid Unsubmerged Vegetation

Foad Maturi 1  and Mehdi Behdarvandi Askar 1
  • 1 Department of Offshore Structures, Faculty of Marine Engineering

Abstract

Shear stress is one of the most critical parameters in hydraulic and coastal engineering, which is often measured indirectly. Since there is no instrument to measure this parameter directly and given that it is usually calculated by measuring other parameters such as velocity and pressure and using some equations, shear stress measurement is often accompanied with large measurement errors. In this study, a new technique and direct measurement using physical modeling in a hydraulic knife-edge flume and load cell were employed to measure the shear stress in a rectangular channel with rigid unsubmerged vegetation with Dv= 20, 25, and 32mm in

Q=25 and 30 Lit/S and y=10, 12, 17, and 20 cm. The results indicate that the shear stress and the dimensionless τ0τ ratio decrease in a constant flow discharge with increasing the flow depth. It was also shown that the shear stress would be enhanced with an increase

in vegetation diameter due to increasing vegetation density against flow. According to dimensionless ratios of τ0τ and Dvy in the graphs and considering the trend lines with appropriate correlation coefficients, some equations were presented to calculate the shear stress in the concerned range.

If the inline PDF is not rendering correctly, you can download the PDF file here.

  • Hoshmandi F., Zahiri A., Dehghani A. A. and Meftah Halghi M., 2014, “Comparison of Estimation of Shear Stress Distribution in Open Channels”, Journal of Soil and Water Protection Research, 21(5), 284-295.

  • I. Nezu, and H. Nakagawa, 1993, “Turbulence in open-channel flows”, Rotterdam, The Netherlands: Balkema.

  • D. W. Knight, J. D. Demetrious, and M. E. Hamed, 1984, “Boundary shear in smooth rectangular channel”, J. Hydraulic Eng., 110(4), 405-422.

  • A. Tominaga, I., Nezu, K. Ezaki, and H. Nakagawa, 1989, “Threedimensional turbulent structure in straight open channel flows”, Journal of Hydraulic Research, 27, 149-173.

  • S. Dey, and M. F. Lambert, 2005, “Reynolds and bed shear in nonuniform unsteady open-channel flow”, Journal of. Hydraulic Engineering, 131(7), 610-614.

  • J. Guo, and P. Y. Julien, 2005, “Shear stress in smooth rectangular open channel flows”, Journal of. Hydraulic Engineering, 131, 30-37.

  • A. R Zarrati., Y. C. Jin, and S. Karimpour, 2008, “Semi-analytical model for shear stress distribution in simple and compound open channel flows”, Journal of. Hydraulic Engineering, 134(2), 187-192.

  • Behdarvandi Askar M., Fathi Moghadam M. and Mosavi Jahromi S. H., 2013, “Comparison of the method of energy and the size of motion in the investigation of the transfer of the size of movement between the sub sections of a compound cross section”, Journal of Water Resources Engineering, 6th year, Summer, 1-14.

OPEN ACCESS

Journal + Issues

Search