Volume of fluid model for an open channel flow problem

2005 ◽  
Vol 32 (5) ◽  
pp. 996-1001 ◽  
Author(s):  
A S Ramamurthy ◽  
Junying Qu ◽  
Diep Vo
Keyword(s):  
Experimental Data ◽  
Channel Flow ◽  
Turbulence Model ◽  
Open Channel ◽  
Fluid Model ◽  
Open Channel Flow ◽  
Pressure Head ◽  
Volume Of Fluid ◽  
Vof Model ◽  
Free Overfall

In the past, the solutions to open flow problems were generally found on the basis of experimental data or through the development of theoretical expressions using simplified assumptions. The volume of fluid (VOF) turbulence model can be applied to obtain the flow parameters such as pressure head distributions, velocity distributions, and water surface profiles for flow in open channels. The free overfall in a rectangular open channel that serves as a discharge measuring structure is selected to apply to the VOF model. The predictions of the proposed VOF model are validated using existing experimental data for both subcritical and supercritical flow approach conditions. Based on the path followed by a fluid particle leaving the brink section, the equations for the nappe profiles in supercritical flows are obtained in terms of the end depth. The VOF turbulence model developed is used to predict the characteristics of a free overfall in a rectangular open channel.Key words: turbulence model, VOF model, numerical simulation, overfall characteristics, open channel flow.

scholarly journals Use of conventional flow resistance equations and a model for the Nikuradse roughness in vegetated flows at high submergence

2018 ◽  
Vol 66 (1) ◽  
pp. 107-120 ◽  
Author(s):  
Paola Gualtieri ◽  
Sergio De Felice ◽  
Vittorio Pasquino ◽  
Guelfo Pulci Doria
Keyword(s):  
Experimental Data ◽  
Channel Flow ◽  
Flow Resistance ◽  
Open Channel ◽  
Open Channel Flow ◽  
Experimental Methodology ◽  
Flow Depth ◽  
Vegetation Height ◽  
Rigid Vegetation ◽  
Grain Roughness

Abstract This study examines the problem of flow resistance due to rigid vegetation in open channel flow. The reliability of the conventional flow resistance equations (i.e. Keulegan, Manning and Chézy-Bazin) for vegetated flows at high submergence, i.e. h/k >5, (where h = flow depth and k = vegetation height) is assessed. Several modern flow resistance equations based on a two-layer approach are examined, showing that they transform into the conventional equations at high submergences. To compare the conventional flow resistance equations at high submergences, an experimental methodology is proposed and applied to the experimental data reported in the literature and collected for this study. The results demonstrate the reliability of the Keulegan equation in predicting the flow resistance. Based on the obtained results, a model to evaluate the Nikuradse equivalent sand-grain roughness, kN, starting from the vegetation height and density, is proposed and tested.

Numerical simulation of sharp-crested weir flows

2009 ◽  
Vol 36 (9) ◽  
pp. 1530-1534 ◽  
Author(s):  
J. Qu ◽  
A.S. Ramamurthy ◽  
R. Tadayon ◽  
Z. Chen
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Open Channel ◽  
Flow Characteristics ◽  
Pressure Head ◽  
Flow Parameters ◽  
Weir Flow ◽  
Wide Range ◽  
And Control ◽  
Measurement And Control

The sharp-crested weir in a rectangular open channel can be used as a simple and accurate device for flow measurement and control in open channels. However, in the past, the solution to this problem was found mainly on the basis of experimental data or through the development of simplified theoretical expressions. In the present study, k-ε turbulence model is applied to obtain the flow parameters such as pressure head distributions, velocity distributions, and water surface profiles. The predictions of the proposed numerical model are validated using existing experimental data. The k-ε turbulence model developed is used to predict the characteristics of a sharp-crested weir in a rectangular open channel. The volume of fluid (VOF) scheme is used to find the shape of the free surface. A properly validated model permits one to obtain the flow characteristics of the sharp-crested weir for a wide range of weir and hydraulic parameters without recourse to expensive and more time consuming experimental methods. Further, the model permits one to incorporate small changes in the geometric parameters involving small changes in inlet and outlet conditions and study their impact on the weir flow characteristics.

A new analytical model for dip modified velocity distribution in fully developed turbulent open channel flow

2019 ◽  
Vol 46 (8) ◽  
pp. 657-668 ◽  
Author(s):  
Minakshee Mahananda ◽  
Prashanth Reddy Hanmaiahgari ◽  
Chandra Shekhar Prasad Ojha ◽  
Ram Balachandar
Keyword(s):  
Experimental Data ◽  
Analytical Model ◽  
Channel Flow ◽  
Correction Factor ◽  
Open Channel ◽  
Open Channel Flow ◽  
Channel Flows ◽  
Superior Performance ◽  
Open Channel Flows ◽  
Proposed Model

This paper presents a new analytical model to predict the streamwise time-averaged velocity profile affected by the dip phenomenon in open channel flows. The novel approach of the present study is that the Finley wake law has been used instead of Coles’ wake law for the outer layer. To validate the new analytical model, six high quality experiments were conducted in a hydraulically rough bed open channel flow by considering variations of aspect ratio, defined as the ratio of the width of the channel to the depth of flow, from 2 to 4. In these controlled experiments, the time-averaged velocities were measured using a Nortek Vectrino-plus acoustic Doppler velocimeter. In addition, 14 sets of available experimental data, including five field experiments conducted across the globe were also used to test the performance of the proposed model. The proposed model, the Finley-dip-modified-log-wake law (FDMLWL), was used to develop a semiempirical equation to compute the dip position as a function of the dip correction factor and the wake parameter. In addition, using the experimental data and FDMLWL, an empirical equation was developed to compute the dip correction factor for hydraulically smooth open channel flows. The comparison of the FDMLWL model with the experimental data belonging to hydraulically smooth, transition, and rough regimes has consistently indicated better representation of the velocity dip phenomenon. The FDMLWL model has also been compared with other analytical models available in the literature and the superior performance of the proposed model is further observed. Finally, based on the satisfactory validation between experimental data and FDMLWL, it is inferred that the proposed model is better suited for modeling zero velocity gradient at the boundary layer edge, as in open channel flows with dip phenomenon.

A numerical model of sediment-laden turbulent flow in an open channel

2005 ◽  
Vol 32 (1) ◽  
pp. 233-240 ◽  
Author(s):  
Joon-Yong Yoon ◽  
Seung-Kyu Kang
Keyword(s):  
Turbulent Flow ◽  
Suspended Sediment ◽  
Channel Flow ◽  
Turbulence Model ◽  
Open Channel ◽  
Concentration Field ◽  
Open Channel Flow ◽  
Sediment Concentration ◽  
Suspended Sediment Transport ◽  
Eddy Viscosity Model

A numerical analysis of sediment-laden flow is carried out. Velocity and suspended sediment concentration profiles are compared with the experiments in open channel flow. The k-ω turbulence model is selected for the fully turbulent flow field because this model has shown good results for wall-bounded flows and for flows on rough surfaces. The concentration equation that takes into account the settling velocity is adopted for the concentration field. A new eddy viscosity model is proposed in the turbulence modeled equations to couple the velocity field and the concentration field. The bed load thickness and surface roughness are considered in this study, and reasonable predictions are achieved.Key words: numerical simulation, suspended sediment transport, open channel flow, k-ω turbulence model.

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