Numerical and experimental analyses of the flow around a horizontal wall-mounted circular cylinder

The numerical modeling of two-dimensional turbulent flow around a horizontal wallmounted circular cylinder at Reynolds numbers in the range of 1000?ReD?7000 is investigated. Ansys® 10.0-FLOTRAN program package is used to solve the governing equations by finite element method, and the performance of the standard k-?, standard k-? and SST turbulence models are examined. A sensitivity study for the three turbulence models is carried out on eight computational meshes with different densities and structures. The computational velocity fields from the present simulations are compared with the experimental results obtained from particle image velocimetry (PIV) measurements for validation purposes. The point of the boundary layer detachment from the cylinder surface and the lengths of primary and secondary separation regions occurring around the cylinder are determined numerically and compared with those obtained experimentally. From these comparisons it is found that the numerical modeling using either of k-v and SST turbulence models is reasonably successful. Using the results of numerical solutions, the drag and lift coefficients, Cd and C1, are also calculated and compared with the measured values. Copyright © 2009 Springer Science+Business Media B.V

Secondary pressures of waves breaking on Seawall

[No abstract available

Experimental and theoretical analyses of two-dimensional flows upstream of broad-crested weirs

Using the particle image velocimetry (PIV) technique, the laboratory experiments are conducted to measure the velocity fields of two-dimensional turbulent free surface flows upstream of rectangular and triangular broad-crested weirs. The experimental flow cases are analyzed theoretically by a computational fluid dynamics (CFD) modeling in which the finite element method is used to solve the governing equations. In the CFD simulation, the volume of fluid (VOF) method is used to compute the free surfaces of the flows. Using the standard k-? and standard k-? turbulence models, the numerical results for the velocity fields and flow profiles are compared with the experimental results for validation purposes. The computed results using k-? turbulence model on compressed mesh systems are found in good agreement with measured data. The flow cases are also analyzed theoretically using the potential flow (PF) approach, and the numerical results for the velocity fields are compared with measurements. © 2008 NRC Canada

Dynamic response of caisson plate to wave impact

Recent experimental studies show that the impact pressures resulting from a wave breaking directly on a vertical wall are very severe in magnitude and short in duration. Some evidence in the literature suggests that these kinds of pressures are capable of causing structural damage to composite-type breakwaters. This study is mainly concerned with the theoretical analysis of the response characteristics of a caisson plate under the wave impact loading. Impact pressure data is taken from recent experimental work. In the dynamic analysis of the caisson plate the classical elastic plate theory is used and the numerical results for the dynamic values of moments and transverse displacement are obtained by employing the method of finite elements together with a mode superposition technique. A new criterion is proposed to determine the number of modes to be considered in the analysis. The time histories of the moments and transverse displacement exhibit similar patterns and the dynamic values are considerably greater than the static values. The latter values are obtained by representing the maximum impact pressure distribution as a static load. A procedure for the dynamic design of caisson plates is proposed which is based on the dynamic magnification factor. © 1986 ASCE

Experimental and numerical modeling of a sluice gate flow

Laboratory experiments are conducted to measure the velocities of 2D turbulent open channel flow upstream of a vertical sluice gate. The flow case having the same conditions with the experiment is analyzed by computational fluid dynamics simulation. The finite element method is used to solve the governing equations by employing the standard k-and standard k-? turbulence closure models. The volume of fluid method is used to determine the free surface of the flow. The numerical results for the velocity field and the free surface profile from eight different computational meshes are compared with the experimental data, and based on the comparisons; the most suitable mesh system among the eight is selected. The comparisons of the numerical and experimental results show that the numerical simulation using the k-turbulence closure model predicts the velocity field and free surface profile more accurately compared to that of the k-? turbulence model. © 2009 International Association of Hydraulic Engineering and Research

Numerical modeling of interaction of a current with a circular cylinder near a rigid bed

The numerical modeling of 2D turbulent flow around a smooth horizontal circular cylinder near a rigid bed with gap ratio G/D = 0.3 at Reynolds number ReD = 9500 is investigated. Ansys® 10.0-FLOTRAN program package is used to solve the governing equations by FEM, and the performance of the standard k - ?, standard k - ?, and SST turbulence models are examined. A sensitivity study for the three turbulence models is carried out on three computational meshes with different densities near the cylinder surface. The computational velocity fields and the Strouhal numbers from the present simulations are compared with those obtained from the PIV measurement. It is found that the time-averaged velocity field of the flow in the proximity of the cylinder is closely affected by the mesh resolution near the cylinder surface, and the mesh refinement in radial direction improves the results of present simulations. The shedding of vortices in the cylinder wake is not predicted by k - ? model on all the three meshes. The results for the time-averaged velocity field show that the numerical modeling using either of k - ? and SST turbulence models on the finest mesh used on the cylinder surface is reasonably successful. © 2009 Elsevier Ltd. All rights reserved.MMF2004D4This work was partly supported by Cukurova University Research Fund under Project No: MMF2004D4. This support is gratefully acknowledged

Numerical modeling of flow over a chute spillway

The simulation performance of two-dimensional flow over a round-crested chute spillway is examined using the finite element method along with the standard k-e and the standard k-w turbulence models. The volume of fluid method is used to determine the free surface of the flow. A mesh dependence study is conducted using the results obtained from three meshes of different densities. Grid convergence analyses indicate that the discretization error in the predicted velocities on the fine-mesh solution is within 2%. A two-layer model for the near-wall treatment was adopted involving a sufficiently fine mesh to model the viscosity-affected region. The numerical results are compared with experimental data for validation of turbulence models. Mean square errors of measured and predicted free surface and velocity profiles indicate that although both closure models predict the chute flow properties with a reasonable accuracy, the agreement using the k-? model is slightly better. © 2009 International Association of Hydraulic Engineering and Research

Experimental validation of volume of fluid method for a sluice gate flow

Laboratory experiments are conducted for 2D turbulent free surface flow which interacts with a vertical sluice gate. The velocity field, on the centerline of the channel flow upstream of the gate is measured using the particle image velocimetry technique. The numerical simulation of the same flow is carried out by solving the governing equations, Reynolds-averaged continuity and Navier-Stokes equations, using finite element method. In the numerical solution of the governing equations, the standard k - ? turbulence closure model is used to define the turbulent viscosity. The measured horizontal velocity distribution at the inflow boundary of the solution domain is taken as the boundary condition. The volume of fluid (VOF) method is used to determine the flow profile in the channel. Taking into account of the flow characteristics, the computational domain is divided into five subdomains, each having different mesh densities. Three different meshes with five subdomains are employed for the numerical model. A grid convergence analysis indicates that the discretization error in the predicted velocities on the fine mesh remains within 2%. The computational results are compared with the experimental data, and, the most suitable mesh in predicting the velocity field and the flow profile among the three meshes is selected. © 2012 A. A. Oner et al

Prediction of geometrical properties of perfect breaking waves on composite breakwaters

Breaking wave loads on coastal structures depend primarily on the type of wave breaking at the instant of impact. When a wave breaks on a vertical wall with an almost vertical front face called the "perfect breaking", the greatest impact forces are produced. The correct prediction of impact forces from perfect breaking of waves on seawalls and breakwaters is closely dependent on the accurate determination of their configurations at breaking. The present study is concerned with the determination of the geometrical properties of perfect breaking waves on composite-type breakwaters by employing artificial neural networks. Using a set of laboratory data, the breaker crest height, hb, breaker height, Hb, and water depth in front of the wall, dw, from perfect breaking of waves on composite breakwaters are predicted using the artificial neural network technique and the results are compared with those obtained from linear and multi-linear regression models. The comparisons of the predicted results from the present models with measured data show that the hb, Hb and dw values, which represent the geometry of waves breaking directly on composite breakwaters, can be predicted more accurately by artificial neural networks compared to linear and multi-linear regressions. © 2011 Elsevier Ltd

Dynamic analysis of a vertical plate exposed to breaking wave impact

From the experimental studies in recent years, it has become known that when a wave breaks directly on a vertical faced coastal structure, high magnitude impact pressures are produced. The theoretical and experimental studies show that the dynamic response of such structures under wave impact loading is closely dependent on the magnitude and duration of the load history. The dynamic analysis and design of a coastal structure can be succeeded provided the design load history for the wave impact is available. Since these types of data are very scarce, it is much more convenient to follow a method which is based on static analysis for the dynamic design procedure. Therefore, to facilitate the dynamic design of a vertical plate that is exposed to breaking wave impact, a multiplication factor called "dynamic magnification factor" is herein presented which is defined as the ratio of the maximum value of the dynamic response to that found by static analysis. The computational results of the present study show that the dynamic magnification factor is a useful ratio to transfer the results of static analysis to the dynamic design of a coastal plate for the maximum impact pressure conditions of pmax/?H0?18. © 2004 Elsevier Ltd. All rights reserved.MMF2002BAP11This work was partly supported by Çukurova University Research Fund under the project no: MMF2002BAP11 which is gratefully acknowledged