Proceedings of the 9th International Conference

on Hydrodynamics (ICHD 2010)

October 11 – 15, 2010,Shanghai, China
Editors: Y. S. Wu, S. Q. Dai, H. Liu, L. D. Zhou, X. C. Yang

Computational Fluid Dynamics (25)

B1-1 Three-dimensional numerical simulation of flow around a circular cylinder under combined steady and oscillatory flow

Ming Zhao, Liang Cheng, Hong-wei An.

School of Civil and Resource Engineering, The University of Western Australia,  35 Stirling Highway, Crawley, WA 6009, Australia

Abstract :

Combined steady and oscillatory flow past a circular cylinder is investigated numerically by three-dimensional Direct Numerical Simulation (DNS). The incompressible Navier-Stokes equations are solved by finite element method (FEM). The aim of this study is to investigate influence of the existence of steady current on the flow regime and hydrodynamics forces. The computational results of pure oscillatory flow past a circular cylinder agree well with the experimental data. The flow ratios(ratio of current velocity to oscillatory velocity amplitude) are 0.0, 0.2 0.5 and 1.0 in the study. The influence of the flow ratio on the vortex shedding regime and hydrodynamic forces on the cylinder are investigated numerically.

.

B1-2 Study of droplet deformation, heat-conduction and solidification using incompressible smoothed particle hydrodynamics method

Hong-bing Xiong, Jian Zhu.

Department of Mechanics, Zhejiang University, Hangzhou, China

Abstract :

This paper presents a numerical model based on incompressible smoothed particle hydrodynamics (SPH) method to simulate the deformation, heat-conduction and solidification process of a droplet impinging on a substrate. Continuum, momentum and energy equations of the fluid flow are solved using SPH method, with van der Waals force accounting for the surface tension and Fourier's law for heat conduction. Incompressible smoothed particle hydrodynamics method (ISPH) is used here instead of weakly compressible smoothed particle hydrodynamics method (WSPH), to satisfy the fluid incompressibility. Effects of rough and smooth substrates are also taken into account. Results show that the droplet begins to deform and spread, followed by solidification. Also, the temperature of droplet falls faster in the rough one, and this may attribute to the roughness.

B1-3 A hybrid RANS-LES model for combining flows in open-channel T-junctions.

Cheng Zeng, C. W. Li.

Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, China.

Abstract :

In the present study, a hybrid RANS-LES (Reynolds Averaged Navier-Stokes equation – Large Eddy Simulation) model is developed for the simulation of open channel T-junction flows. The hybrid approach can save computational effort comparing to the LES approach. The comparison between the computational results and the detailed experimental data shows that this relatively new modeling approach is more accurate than the RANS approach in the prediction of the combining flows in T-junctions.

B1-4 Large eddy simulation of oscillatory boundary layer at REδ=3500.

Qiang Zhang.

School of Aerospace Engineering, Beijing Institute of Technology, Beijing, china.

Abstract :

The oscillatory boundary layer at Reynolds number of 3500 over an oscillating wall is simulated by the method of large-eddy simulation (LES). The Reynolds number is chosen as Reδ=3500 in according with one of the wellknown experimental cases (Test No. 10, Ref. [3]). The simulation presents the first- and second-order statistics of the oscillatory boundary layers, which are in good agreement with the experimental data. By investigating of the existence of the logarithmic layer in the velocity profiles, the fully developed turbulence state is identified; During half a cycle (90°-270°), the logarithmic layer starts to appear at about 110°, and lasts till 250° in the current simulation. The evolutions of the turbulent energy spectra are also illustrated.

B1-5 Effects of turbulence models on numerical simulations of wave breaking and run-up on a mild slope beach.

Hong Xiao, Wen-rui Huang.

Department of Civil and Environmental Engineering, Florida State University, Tallahassee, USA.

Abstract :

The performance of the standard k–ε model, the high-Reynolds-number k–ω model, the 1-equation k model, and the non-friction Euler model is examined against the case of wave run-up on a mild slope. A numerical model based on N-S equations and Volume Of Fluids (VOF) method is employed. Comparisons of elevation, velocity and shear stress are made among the four turbulence models against experimental data of wave run-up on a mild slope beach. It is found that before wave breaking on the slope, the outputs of the four different turbulence models agree reasonably well with each other. This suggests that during the run-up process the turbulence effect is negligible before wave breaking. Moreover, in the wave breaking zone, both the standard k–ε model and the high-Reynolds-number k–ω model predict the mean velocity field quite well, but generally under-predict the velocity and turbulent kinetic energy using wall functions on the solid slope surface.

B2-1 Nonlinear motions in head waves with a RANS and a potential code.

Alessandro Grasso, Diego Villa, Stefano Brizzolara , Dario Bruzzone.

Departement of Naval Architecture and Marine Tecnologies, University of Genova, Genova, Italy.

Abstract :

In the last years, the employment of RANS codes for a wide range of naval architecture problems is grown, since this methodology is capable of reproducing physical behaviors that are generally neglected by other models. The paper presents the results of a set of numerical tests performed employing this methodology with the aim of verifying its capability in the solution of seakeeping problem. Several conditions are analyzed varying the frequency of the incident wave and its amplitude, in order to catch nonlinear effects. The results are compared with the ones achieved by a weakly nonlinear procedure based on potential theory.

B2-2 A three-dimensional fictitious domain method for the simulation of fluidstructure interactions.

Zhao-sheng Yu , Xue-ming Shao.

Department of Mechanics, State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou, China.

Abstract :

The Distributed-Lagrange-Multiplier based Fictitious Domain (DLM/FD) method previously proposed by Yu [J. Comput. Phys. 207 (2005), 1-27] for the simulation of fluid/flexible-body interaction problems is extended from the 2D to the 3D case in this study. We first demonstrate that the Lagrange multiplier problem can be more efficiently solved with a direct-forcing scheme instead of the original Uzawa iterations without the sacrifice of the accuracy. The type of the interpolation function (i.e. smoothed delta function) for the transfer of the quantities between the Eulerian and Lagragian frames is shown not to affect the results significantly. Secondly, the fictitious domain method is implemented in the three dimensional case. The new 3D codes are applied to the flapping of a 3D flexible plate in a uniform flow, and the deformation of tri-leaflets at opening stage.

B2-3 A simulator developed for a twin-pod AUV, the Marport SQX-500.

Mo-qin He, Christopher D.Williams, Peter Crocker etc.

National Research Council Canada, Institute for Ocean Technology St. John's, Newfoundland, Canada.

Abstract :

A vertically arranged twin-pod autonomous underwater vehicle (AUV) is presently under development in St. John’s Newfoundland. A large separation of the centre of gravity (CG) and the centre of buoyancy (CB) can be achieved by placing heavy batteries and payloads in the lower pod and placing the light controller and communication electronics on the upper pod. With the large vertical separation between CG and CB the twin-pod vehicle becomes highly stable in pitch and roll and thus provides an ideal platform for obtaining photos, video and sonar images of the seabed. This paper presents the vehicle motion simulations that have been done in support of this novel AUV design and development.

B2-4 Numerical study on flow structure near two impermeable trapezoid submerged breakwaters on slop bottoms.

Yong-gang Cao, Chang-bo Jiang, Yu-chuan Bai.

School of Civil Engineering, Tianjin University, Tianjin ,China.

Abstract :

Studying on hydrodynamic characteristics in water waves propagating over two impermeable trapezoid submerged breakwaters is of great significance to research design and construction of this type of submerged breakwaters. The turbulent characteristics are discussed with cnoidal waves in the wave flume with 1:20 smooth slope. The governing equations of the vertical 2D model are the Reynolds-averaged Navier-Stokes equations. The Reynolds stress terms are closed by a nonlinear (anisotropic) k ε − turbulence transportation model. Using a VOF method for tracking the free surface and source function wave generating method. Furthermore, the supplementary discussion is made by means of numerical results.

B2-5 A numerical study of wave propagation and run-up in water channels.

Masazumi Amakata, Masatoshi Yuhi, Hajime Ishida.

Yachiyo Engineering, Co. Ltd., Shinjuku, Tokyo, Japan.

Abstract :

It is important to understand how water waves propagate through water channels in order to reduce inundation damages induced by surges and/or tsunami run-up. For this purpose, a two-dimensional numerical model is developed based on Nonlinear Shallow Water Equations. In order to appropriately describe the strongly nonlinear hydrodynamics, a high-order TVD scheme is implemented. Model capabilities are confirmed through comparison with existing analytical studies including the dam-break problems, run-up and back-wash on a sloping bathymetry. The model is then applied to the study on the inundation of bore propagating in a channel of parabolic cross-section from a side breach.

B3-1 IBM/ICM method for interactions between moving bodies and free surfaces.

Deng Jian, Xie Fang-fang, Shao Xue-ming, Yu Zhao-sheng.

School of Aeronautics and Astronautics, Zhejiang University, Hangzhou, China.

Abstract :

The IBM/ICM method is developed to simulate the interactions between moving bodies and free surfaces. This method is a combination of Immersed Boundary Method (IBM) and Interface Capture Method (ICM), inheriting the IBM’s capability of using non-body conformal grids to represent the effect of a moving body in the flow by only adding a pseudo body-force in the right side of Navier-Stokes equations, as well as the capability of ICM, i.e. VOF, to capture the interface between two immiscible fluids. In the current paper, the Lagrange-multiplier based IBM method is employed and the volume of fraction (VOF) is introduced as an indicator function to mark the different fluids. The numerical method is validated by the case of high-speed impact by a horizontal circular cylinder, which exhibits a wide range of dynamical response characteristics, i.e. the formation of a cavity and induced pressure waves in the late stages of the cavity collapse, depending primarily on the projectile’s impact velocity.

B3-2 Free-surface flow past a submerged cylinder.

Meng-yu Lin, Liang-hsiung Huang.

Department of Civil Engineering, National Taiwan University, Taipei, China.

Abstract :

This study employs a Lagrangian frame numerical method to investigate two-dimensional free surface flow induced by a submerged moving cylinder. This method combines the advantages of vortex methods and boundary integral methods, and is capable of capturing the complex motion of free surface and vortices. A series of computations are performed to investigate the effects of Froude number, the depth of submergence and still water depth on the flow motion. Free surface deformation, wake vortex and hydrodynamic forces are studied.

B3-3 Numerical study of high-order Lagrangian structure functions in a turbulent channel flow with low Reynolds number.

Jian-ping Luo, Zhi-ming Lu, TatsLo Ushijima, etc.

Shanghai Institute of Technology, Shanghai, China.

Abstract :

The scaling exponents of Lagrangian velocity structure functions from orders 1 to 10 in a low Reynolds number turbulent channel flow are investigated by using direct numerical simulation. The Reynolds number Reτ is 80 (based on friction velocity on the wall). The Lagrangian velocity structure functions are shown to obey the scaling relations <Δvq(τ)>~τζL(q). The scaling exponents are normalized by ζL(2)(so-called ESS procedure). The coincidence between the theoretical predictions and numerical calculations is very good for the longitudinal scaling exponent in the channel center. It is also found that the high-order longitudinal scaling exponents agree with theoretical values better than those for the transverse direction.

 

B3-4 High effective WENO scheme for transonic inviscid flow computation on a helicopter rotor in hover.

Li Xu, Pei-fen Weng, Ai-ming Yang, Jue Ding.

Department of Mathematics and Physics, Shanghai University of Electric Power Shanghai, China.

Abstract :

A high-order upwind scheme with high efficiency has been developed to compute the inviscid flow of a helicopter rotor in hover. For rotary-wing wake capturing, an improved fifth-order weighted essentially non-oscillatory (WENO) scheme is adopted to interpolate higher order left and right states across a cell interface with Roe Riemann solver updating inviscid flux. To improve the efficiency and convergence to steady state, three-level V-cycle multigrid relaxation scheme is used. The performance of the schemes is investigated in a transonic inviscid flow around hovering rotor. The results reveal that WENO has the great capabilities to capture shock with high resolution and has a lower numerical dissipation than MUSCL for capturing wake vorticity. Moreover, multigrid scheme can accelerate convergence to a great extent.

 

B3-5 High-order finite difference solution for 3D nonlinear wave-structure interaction.

Guillaume Ducrozet, Harry B. Bingham, Allan Peter Engsig-Karup & Pierre Ferrant.

Laboratoire de Mécanique des Fluides Ecole Centrale de Nantes, Nantes, France.

Abstract :

This contribution presents our recent progress on developing an efficient fully-nonlinear potential flow model for simulating 3D wave-wave and wave-structure interaction over arbitrary depths (i.e. in coastal and offshore environment). The model is based on a high-order finite difference scheme OceanWave3D presented in [1, 2]. A nonlinear decomposition of the solution into incident and scattered fields is used to increase the efficiency of the wave-structure interaction problem resolution. Application of the method to the diffraction of nonlinear waves around a fixed, bottom mounted circular cylinder are presented and compared to the fully nonlinear potential code XWAVE as well as to experiments.

B4-1 SPH simulation of green water and ship flooding scenarios.

D. Le Touzé, A. Marsh, G. Oger, P.-M. Guilcher, etc.

Fluid Mechanics Lab., Ecole Centrale Nantes / CNRS, Nantes, France.

Abstract :

Flooding of a ship's deck (greenwater) or within its internal compartments can severely restrict the operational ability of the vessel, and the safety of its cargo. In severe circumstances such as those produced by freak waves or hull damage, the vessel can becomeunstable causing it to sink and/or capsize. The flows produced by such events tend to be highly dynamic, with large amounts of free surface deformation. For this reason, SPH is a valuable method for predicting the physics of such flows. In this paper, SPH is used to predict fluid behaviour for two different flooding scenarios. The first is the interaction between a vessel (represented by a rigid body) and undulating travelling waves. The predicted water heights on the deck are compared to experimental results in [1]. The second is the transient flooding behaviour that occurs during, and immediately after a side collision between two vessels. Water heights are measured close to the point of impact within the vessel. The measurements are compared to experimental results in [2].

B4-2 Numerical investigation of a swirling flow under the optimal perturbation.

Cheng Chen, De-jun Sun.

Department of Modern mechanics, University of Science and Technology of China Hefei , China

Abstract :

The nonlinear evolution of 3-D instability of a viscous swirling flow, namely, the Oseen vortex, is addressed by direct numerical simulation with a Reynolds number equal to 5000. The global optimal perturbation is considered as the initial perturbation. In axisymmetric cases, three flow regimes are found: (1) the linear growth; (2) the decay of perturbation energy; (3) secondary energy growth. The linear energy growth, which is characterized by the amplification of radial perturbations, is arrested by the interaction between the vortex ring and the Oseen vortex core. The development of the vortex structure is also investigated for non-symmetric flows.

 

B4-3 Numerical simulation of cavity flow induced noise by LES and FW-H acoustic analogy.

Nan Zhang , Hong-cui Shen, Hui-zhi Yao.

China Ship Scientific Research Center, Wuxi, China.

Abstract :

The predictions of cavity flow and flow-induced noise are two important and complex issues in fluid-acoustic coupling field. Numerical studies for these issues are performed in the paper by large eddy simulation (LES) and FW-H acoustic analogy. Firstly, the wall pressure fluctuations of plate, foil, shutter hole are computed and compared with experimental results. The robustness of large eddy simulation in unsteady flow calculation is analyzed. Secondly, the calculation of a 2-D cavity flow is accomplished. The power spectrum of pressure fluctuations is compared with measured data and the vorticity distribution is analyzed. Finally, the flow induced noises of two 3D cavities are predicted. The computed results are compared with experimental data of Large Circulation Channel in CSSRC. It shows that the numerical prediction method in the paper is credible.

 

B4-4 Forces due to exterior singularities upon 2- and 3-dimensional bodies.

Seung-joon Lee.

Department of Naval Arch. & Ocean Eng., Engineering College, Chungnam National University, Daejeon, Korea.

Abstract :

Thrust deduction, or the resistance increase, is not fully investigated probably because of the complexity of the flow pattern in the stern region. In this work, it is assumed that the theory of potential flows may represent the most significant portion of the physics of the phenomena. Hence the propulsor and other devices in the stern region are represented by exterior singularities and their effects upon the resistance increase are estimated by taking a circular cylinder and a sphere as the 2- and 3-dimensional body, respectively. Results for a circular cylinder are summarized, and those for a sphere are given more attention.

 

B4-5 3-D numerical simulations of violent sloshing by CIP-based method.

Chang-hong Hu , Kyung-Kyu Yang, Yong-hwanKim.

Research Institute for Applied Mechanics, Kyushu University, Japan.

Abstract :

The violent sloshing flow inside a rectangular tank is computed by the CIP (Constrained Interpolation Profile)[1]based Cartesian grid method. Two kinds of CIP scheme, the original CIP scheme and the RCIP scheme, have been applied to the flow solver. 2-D and 3-D computations using the two CIP schemes are carried out and their performances are discussed by comparing the results of the impact pressures on the wall and the free surface profiles to the experimental measurements.

 

B5-1 Three dimensional numerical simulation of bore type tsunami propagation and run up on to a dike.

Indradi Wijatmiko, Keisuke Murakami.

Interdisciplinary Graduate School ofAgriculture and Engineering, University of Miyazaki, Miyazaki, Japan.

Abstract :

Tsunami increases its height on the shallow water area and may transfers into bore when it breaks. Bore type tsunami sometimes produces huge forces and causes large damages on coastal infrastructures. In order to mitigate tsunami damages, bore type tsunami propagation, run-up and its characteristics need to be understood. And aside of experimental study, numerical simulation provides principal physical quantities with higher resolution in time and space. This study discus the validity of a numerical simulation based on VOF method, CADMAS-SURF, and characteristics of bore propagation on to a dike.

 

B5-2 3-D Investigation on forces exerted on a sediment particle in current and wave boundary layer through 3D lattice Boltzmann simulation.

Qing-he Zhang, Lei Ding.

School of Civil Engineering, Tianjin University & Key Laboratory of Harbor and Ocean Engineering (Tianjin University), Ministry of Education,Tianjin , China.

Abstract :

The 3-D lattice Boltzmann method is applied to evaluate the forces exerted on a stationary spherical particle in current and wave boundary layer flow in order to analyze the forces contributing to the incipient motion of the sediment particle. Results indicate that for current, the forces reach statistically steady finally at a relative low particle Reynolds number (less than 40). The streamwise drag force is the main driven force while the effect of the spanwise force can be ignored. The reason that results in the phenomenon is also discussed. As for the wave, the cyclical nature of the flow makes the evolution of drag and lift forces become quasiperiodic. The streamwise drag force is still the main driven force, but it changes direction with the flow. Meanwhile, the spanwise vorticity and the pressure around the particle show asymmetric distribution. The influence of spanwise force on the particle cannot be neglected.

 

B5-3 Numerical simulations of viscous flows around surface ship by level set method.

De-cheng Wan, Zhi-rong Shen, Juan Ma.

State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, China.

Abstract :

Numerical simulations of viscous flows around surface ships by coupling the 3D incompressible RANS equations with level set method are presented in this paper. The finite difference method is used to discretize the RANS equations with turbulent model SST ω − k . The fully nonlinear boundary condition at the free surface is satisfied at each time step and the evolution of the free surface is achieved by using the level set method. The coupled solver is applied to a benchmark case of viscous flows around an advancing Wigley ship with various Froude numbers. The computational results are in excellent agreement with experimental data. The simulations reveal clearly the generation and evolution of bow and stern waves.

 

B5-4 Research on particle size distribution in rectangular turbulent channel flow.

Fu-jun Gan, Jian-zhong Lin.

State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University.

Abstract :

Large eddy simulations of three dimensional particle-laden turbulent channel flow are performed for Re = 13800. The flow results are validated using the experimental data and good agreements are achieved. TEMOM is employed to deal with PGDE, which describes PSD, involving the effect of shear induced coagulation, which is greatly affected by the effects of turbulent transport and preferential concentration, represented by radial relative velocity and radial distribution function, respectively. Particles with four different stokes number are considered to study the above effects on the evolution of PSD. In the results, the distributions of particle number concentration, polydispersity, particle diameter are detailed discussed.

 

B5-5 Coupling of CFD model and FVCOM to predict small-scale coastal flows.

Xiu-guang Wu, Han-song Tang.

Zhejiang Inst. of Hydraulics & Estuary, Hangzhou, China.

Abstract :

In order to accurately simulate small-scale coastal ocean phenomena, we propose to couple a computational fluid dynamics (CFD) model with the Unstructured Grid Finite Volume Coastal Ocean Model (FVCOM). The CFD model resolves small-scale flows, the FVCOM predicts large-scale background currents, and the resulting hybrid system is able to capture flow phenomena with spatial scales from centimeters to hundreds of kilometers. The coupling is two-way and realized using domain decomposition with aid of Chimera overset grids. Numerical examples are presented to demonstrate the feasibility and performance of the proposed hybrid approach.