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Information Journal Paper

Title

NUMERICAL STUDY ON ENERGY DISSIPATION OF BLOCK RAMPS

Pages

  137-146

Abstract

 One of the most efficient energy dissipatoion structures in open channel flow are BLOCK RAMPs; which have been considered and used most often recently because of the simple performance. This kind of energy dissipators can be assumed as a particular type of baffle block chutes, but with natural base materials like sands and gravels and without cement. In laboratories, several physical models have been built and examined regarding their efficiencies to dissipate energy of flow. These experimental studies are not only too expensive and time consuming, but also some of the hydraulic conditions like higher velocities could not be obtained in controlled conditions of laboratories. Moreover, there are always problems with changing scales in laboratory studies. Hence, using computational fluid dynamics (CFD) codes are to some extent more favorable to engineers with which fluid hydraulic behavior is more widely examined. This paper at first, reviews the classifications of these structures regarding their fabrication and roughness from various point of views, and then deals with the formation of some types of flow regimes with different volume flow rates on them. In continuation, to study the three dimensional flow field around BLOCK RAMPs, FLOW-3D SOFTWARE is utilized and hence, the mechanism of energy dissipation on various flow regimes on these structures has been surveyed. In this research, incompressible fluid assumption is made and Large Eddy Simulation (LES) turbulence model is used. Since it was a shallow water condition, Volume of Fluid (VOF) method is used to calculate the free surface elevation. The numerical results showed the more energy dissipation with more turbulence and more turbulence with forming the recirculating flow and extending the distance of the reattachment point from the boulders. Consequently, energy dissipation is maximum for lower volume flow rate and higher slope of the ramp. Since in these two conditions, the flow involves with roughness of the ramp more and more; hence it gets easier for turbulent flow to happen. In other words, energy dissipation is also maximum for the non-submerged boulders. Flows for the cases in which boulders are submerged have different mechanism of energy dissipation. In these types of flows, energy dissipation is maximum for the wake-interface flow condition and isolated roughness flow condition, respevtively. Therefore, in order to enhance the energy dissipation in flow over BLOCK RAMPs, it is advised to reduce the effective cross section or reduce the submergence of scale roughness while maintaing the same effective cross section and the volume of fluid flowing over the structure. Changing the boulder ordering from rows to staggered would be another way to increase the energy dissipation.

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    APA: Copy

    SHARIFNEJAD AZIZI, Z., & Salehi Neishabouri, s.a.. (2016). NUMERICAL STUDY ON ENERGY DISSIPATION OF BLOCK RAMPS. MODARES CIVIL ENGINEERING JOURNAL, 15(4), 137-146. SID. https://sid.ir/paper/256930/en

    Vancouver: Copy

    SHARIFNEJAD AZIZI Z., Salehi Neishabouri s.a.. NUMERICAL STUDY ON ENERGY DISSIPATION OF BLOCK RAMPS. MODARES CIVIL ENGINEERING JOURNAL[Internet]. 2016;15(4):137-146. Available from: https://sid.ir/paper/256930/en

    IEEE: Copy

    Z. SHARIFNEJAD AZIZI, and s.a. Salehi Neishabouri, “NUMERICAL STUDY ON ENERGY DISSIPATION OF BLOCK RAMPS,” MODARES CIVIL ENGINEERING JOURNAL, vol. 15, no. 4, pp. 137–146, 2016, [Online]. Available: https://sid.ir/paper/256930/en

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