Resistance in Steep Open Channels due to Randomly Distributed Macroroughness Elements at Large Froude Numbers

Thappeta, Suresh Kumar; Bhallamudi, S. Murty; Fiener, Peter; Narasimhan, Balaji

doi:10.1061/(asce)he.1943-5584.0001587

Cited by 8 publications

(24 citation statements)

References 33 publications

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“…It can be concluded from the results presented in this section and from previous studies [31][32][33]35,48,49] that the ANSYS-CFX model can be effectively used for performing numerical experiments to simulate flows in step-pools in steep channels. Results obtained from such numerical experiments can be analyzed to gain insight into the energy loss due to step-pools in mountainous channels.…”

Section: Testing and Validation Of Ansys-cfxmentioning

confidence: 67%

“…The data is used to develop a simple empirical power law equation as shown below with R 2 value of 0.87. The power law was found to be the most reasonable functional relation while studying flow resistance [31,35]. Authors did not consider ratio of step height to length since it is not investigated in this study.…”

Section: Multiple Step-poolsmentioning

confidence: 95%

“…The standard k − ε turbulence model was chosen based on the performances of previous model studies from the literature, e.g., [31,32,35,36,39,43] as discussed in the introduction. The governing equations for k − ε turbulence model are as follows [45]:…”

Section: Description Of Cfd Modelmentioning

confidence: 99%

“…Over the last few years, myriad research, e.g., [31][32][33][34][35] has proved that threedimensional (3D) computational fluid dynamics (CFD) models could be a practical and robust tool to investigate flow structure in complex flow fields. With regard to step-pools, Chen et al [36] used volume of fluid (VOF) technique with k − ε turbulence model to simulate flow structure on stepped spillways.…”

Section: Introductionmentioning

confidence: 99%

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Energy Loss in Steep Open Channels with Step-Pools

Thappeta

Bhallamudi

Chandra

et al. 2020

Water

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Three-dimensional numerical simulations were performed for different flow rates and various geometrical parameters of step-pools in steep open channels to gain insight into the occurrence of energy loss and its dependence on the flow structure. For a given channel with step-pools, energy loss varied only marginally with increasing flow rate in the nappe and transition flow regimes, while it increased in the skimming regime. Energy loss is positively correlated with the size of the recirculation zone, velocity in the recirculation zone and the vorticity. For the same flow rate, energy loss increased by 31.6% when the horizontal face inclination increased from 2° to 10°, while it decreased by 58.6% when the vertical face inclination increased from 40° to 70°. In a channel with several step-pools, cumulative energy loss is linearly related to the number of step-pools, for nappe and transition flows. However, it is a nonlinear function for skimming flows.

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Section: Testing and Validation Of Ansys-cfxmentioning

confidence: 67%

Section: Multiple Step-poolsmentioning

confidence: 95%

Section: Description Of Cfd Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Energy Loss in Steep Open Channels with Step-Pools

Thappeta

Bhallamudi

Chandra

et al. 2020

Water

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“…Roughness coefficient was decreased by increasing the vegetation flexibility. Thappeta, et al, [5] investigated the effect of using hemisphere boulders and cylindrical roughness elements constructed in a staggered distribution in a steep open channel by using CFD software. The energy loss was decreased as the density of the boulders was increased.…”

Section: Introductionmentioning

confidence: 99%

Investigations on Large-Scale Geometric Roughness Elements in Open Channels with Different Heights

Alwan¹,

Azzubaidi²

2021

JAARU

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Large-scale geometric roughness elements is one of the solutions that is used to protect openchannels from erosion. It is use to change the hydraulic characteristics of the flow. It may be concrete blocksor large stone placed at the bed of the channel to impose more resistance in the bed. The height of theseroughness elements is an important parameter that can affect the hydraulic characteristics of the flow. Usinga series of tests of T-shape roughness elements at three different heights, 3, 4.5, and 6cm, arranged in thefully rough configuration in order to investigate the velocity distributions along the flume. ANSYSParametric Design Language, APDL, and Computational Fluid Dynamics, CFD, were used to simulate theflow in an open channel with roughness elements. This simulation helps to find the best height of roughnesselements that can be used to change the hydraulic characteristics of the flow. The results showed that thevelocity values are decreased near the bed by about 61%, 58%, and 64% in case of 3cm, 4.5cm, and 6cmroughness heights consequently compared with the velocity of the control case. The velocity values areincreased near the free surface by about 32% and 19% in case of roughness elements height 6cm comparedwith 3cm and 4.5cm roughness heights respectively. The case of 6cm roughness height is considered to bethe effective case for decreasing the velocity values near the bed of the flume.

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