Three-dimensional turbulent structure in straight open channel flows

Tominaga, Akira; Nezu, Iehisa; Ezaki, Kazuhiro; Nakagawa, Hiroji

doi:10.1080/00221688909499249

Cited by 203 publications

(147 citation statements)

References 9 publications

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“…기존 실험 연구들을 살펴보면 협폭수로의 경우 크게 바닥부근에 서 발생하는 바닥 이차흐름(bottom secondary currents)과 자유수 면 근처에서 발생하는 자유수면 이차흐름(free surface secondary currents)이 존재한다고 알려져 있다 (Nezu and Rodi, 1985;Tominaga et al, 1989). 또한, 최근 연구에 의하면 측벽과 자유수면의 접합부 에서 또 다른 작은 와가 존재한다고 밝혀졌다 (Grega et al, 1995;Hsu et al, 2000).…”

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“…For the non-isotropic residual stress term, Smagorinsky's (1963) model is used. The flow in the open-channel whose width-to-depth ratio is 2, from experiment of Tominaga et al (1989), is simulated numerically. Simulation results are compared with measured data by Tominga et al (1989) and Nezu and Rodi (1985) and with LES data by Shi et al (1999).…”

Section: Introductionmentioning

confidence: 99%

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Large Eddy Simulation of Rectangular Open-Channel Flow using OpenFOAM

Ban¹,

Choi²

2014

Journal of The Korean Society of Civil Engineers

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This study presents numerical simulation of turbulent flows in a rectangular open-channel that has a width-to-depth ratio of 2 using the source code provided by OpenFOAM. Large eddy simulations are carried out by solving the filtered continuity and momentum equations numerically. For the non-isotropic residual stress term, Smagorinsky's (1963) model is used. The flow in the open-channel whose width-to-depth ratio is 2, from experiment of Tominaga et al. (1989), is simulated numerically. Simulation results are compared with measured data by Tominga et al. (1989) and Nezu and Rodi (1985) and with LES data by Shi et al. (1999). Comparisons revealed that the model simulates the mean flow and turbulence statistics well. Specifically, the model reproduced the inner secondary currents located at the corner of sidewall and free surface successfully. In addition, the vortical component of turbulence intensity shows bulged contours towards the bottom edge. 수공학Water Engineering

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Section: Introductionmentioning

confidence: 99%

Large Eddy Simulation of Rectangular Open-Channel Flow using OpenFOAM

Ban¹,

Choi²

2014

Journal of The Korean Society of Civil Engineers

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“…To study channel migration or to prevent bank erosion, awareness of wall shear stress is required. The effective parameters in shear stress values are the channel geometry, secondary flows and the channel wall and bed roughness recognized through numerous experimental studies (Knight 1981;Tominaga et al 1989;Knight and Sterling 2000;Atabay et al 2004;Seckin et al 2006). Based the division channel into two subsections, the channel bed and sidewall, by Einstein (1942), many researchers used this idea for estimating bed and wall shear stress, e.g., Lundgren and Jonsson (1964), Yang and Lim (2005), Khodashenas and Paquier (2002) and Yang (2005).…”

Section: Introductionmentioning

confidence: 99%

Using two soft computing methods to predict wall and bed shear stress in smooth rectangular channels

2017

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Two soft computing methods were extended in order to predict the mean wall and bed shear stress in open channels. The genetic programming (GP) and Genetic Algorithm Artificial Neural Network (GAA) were investigated to determine the accuracy of these models in estimating wall and bed shear stress. The GP and GAA model results were compared in terms of testing dataset in order to find the best model. In modeling both bed and wall shear stress, the GP model performed better with RMSE of 0.0264 and 0.0185, respectively. Then both proposed models were compared with equations for rectangular open channels, trapezoidal channels and ducts. According to the results, the proposed models performed the best in predicting wall and bed shear stress in smooth rectangular channels. The obtained equation for rectangular channels could estimate values closer to experimental data, but the equations for ducts had poor, inaccurate results in predicting wall and bed shear stress. The equation presented for trapezoidal channels did not have acceptable accuracy in predicting wall and bed shear stress either.

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“…Due to the turbulence and secondary flow generating at the shear layer, the flow structure becomes more complex in an overbank flow case. Detailed experimental measurements have been conducted by Tominaga et al (1989), Arnold et al (1989), Knight (1988, 1989), and Tominaga and Nezu (1991) to investigate experimentally the effects of turbulence quantities and secondary currents in the compound channels.…”

Section: Introductionmentioning

confidence: 99%

Application of the Shiono and Knight Method in asymmetric compound channels with different side slopes of the internal wall

2018

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The Shiono and Knight Method (SKM) is widely used to predict the lateral distribution of depth-averaged velocity and boundary shear stress for flows in compound channels. Three calibrating coefficients need to be estimated for applying the SKM, namely eddy viscosity coefficient (λ), friction factor (f) and secondary flow coefficient (k). There are several tested methods which can satisfactorily be used to estimate λ, f. However, the calibration of secondary flow coefficients k to account for secondary flow effects correctly is still problematic. In this paper, the calibration of secondary flow coefficients is established by employing two approaches to estimate correct values of k for simulating asymmetric compound channel with different side slopes of the internal wall. The first approach is based on Abril and Knight (2004) who suggest fixed values for main channel and floodplain regions. In the second approach, the equations developed by Devi and Khatua (2017) that relate the variation of the secondary flow coefficients with the relative depth (β) and width ratio (α) are used. The results indicate that the calibration method developed by Devi and Khatua (2017) is a better choice for calibrating the secondary flow coefficients than using the first approach which assumes a fixed value of k for different flow depths. The results also indicate that the boundary condition based on the shear force continuity can successfully be used for simulating rectangular compound channels, while the continuity of depth-averaged velocity and its gradient is accepted boundary condition in simulations of trapezoidal compound channels. However, the SKM performance for predicting the boundary shear stress over the shear layer region may not be improved by only imposing the suitable calibrated values of secondary flow coefficients. This is because difficulties of modelling the complex interaction that develops between the flows in the main channel and on the floodplain in this region.

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Three-dimensional turbulent structure in straight open channel flows

Cited by 203 publications

References 9 publications

Large Eddy Simulation of Rectangular Open-Channel Flow using OpenFOAM

Large Eddy Simulation of Rectangular Open-Channel Flow using OpenFOAM

Using two soft computing methods to predict wall and bed shear stress in smooth rectangular channels

Application of the Shiono and Knight Method in asymmetric compound channels with different side slopes of the internal wall

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