Proceedings of the 11th International Conference

on Hydrodynamics (ICHD 2014)

October 19 – 24, 2014Singapore
Editors: TAN Soon Keat, WANG Xikun, GHO Wie Min & Joy CHUA

Session Papers (1-20)

1.  Flow structure and hydrodynamic forces of a near-wall cylinder of different cross-sections

X.K. Wang, S.K. Tan.

Maritime Research Centre, Nanyang Technological University, Nanyang Avenue 639798, Singapore

Abstract :

The effects of wall proximity on the flow around a cylinder (of circular or square cross-section with D = 15 mm) are investigated experimentally under a constant subcritical Reynolds number Re = 6300.Detailed measurement data are provided for different gap heights form the cylinder bottom to the wall surface, with the gap ratio (*G) varied from 0.15 to 2. The flow field was measured using digital Particle Image Velocimetry (PIV), together with direct measurement of fluid dynamic forces (lift and drag) on the cylinder using a piezoelectric load cell. The dynamics of vortex shedding are illustrated by contours of the instantaneous spanwise vorticity and spectral analysis of the lift fluctuation. It is shown that the flow varies significantly with G*in terms of the shear layer development and interference,  which result in corresponding change in hydrodynamic force coefficients and vortex shedding frequencies. The critical gap ratios for the circular and square cylinders are 0.3 and 0.5, respectively, below which periodic vortex shedding from the cylinder is suppressed.

2.  Basic Performance Checks of Twelve-Wire Probe.

Z. Hao, T. ZHOU, L. CHUA.

College of Logistics Engineering, Shanghai Maritime University, 1550 Haigang Avenue, Shanghai, 201306, China

Abstract :

The basic performance in measuring the velocity and temperature derivatives of a probe consisting of four “X-type” hot wires and two pairs of parallel cold wires, totally twelve wires, are conducted to further calculate the full energy dissipation rate f and temperature dissipation rates f. The probe has been checked satisfactory by comparing the measured values with the corresponding isotropic values.

3. Natural Convection in a Vertical Polygonal Duct With Both Walls Exhibiting Superhydrophobic Slip and Temperature Jump.

H. Yuan, C.O. Ng, C.Y. Wang.

Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China.

Abstract :

Free convection with velocity slip and temperature jump in a vertical polygonal duct with a heated circular core is semianalytically solved by the methods of eigenfunction expansion and point match. The conditions of the core wall being at uniform wall temperature or uniform heat flux are considered. The optimum core radius for maximum flow rate is determined as a function of the slip length, temperature jump coefficient, and the number of sides of the polygon.

4.  The use of coarse sediment transport hydraulics to estimate the peak discharge of catastrophic floods.

Colin Clark.

CHRS, Shute Lane, Bruton, Somerset, UK.

Abstract :

Estimates of the magnitude of catastrophic floods are vital for the design of hydraulic structures such as bridges, culverts, reservoir spillways, and urban flood alleviation schemes. However, these events are rare and cannot be studied at the time of their occurrence. A post event survey is needed soon after the event. But when the event took place long ago this is not possible unless a method is used to estimate the peak discharge from the presence of coarse sediment (boulders) in the river channel. In the past critical stream power and stream power have been used to estimate total sediment transport, but it is possible to use these hydraulic relations to estimate peak discharge during the flood. This paper will give three examples of how critical stream power has been used to estimate the peak discharge of catastrophic events, which have eithertaken place recently or in the past. The first occurred in 1857 on the North York Moors UK. A boulder dump was identified near the village of Iburndale. The estimated discharge was close to the extreme catastrophic flood. During the flood several people were drowned and there was considerable damage to property at Iburndaleand also Scarborough. The second event took place in the Cheviot Hills UK in 1893. This event may have been caused by the biggest ever two-hour storm to occur in the UK which means it could be used as a design  event  in similar circumstances. The third event took place at Boscastle inNorth Cornwall UK in 2004. The estimated peak discharge was close to that produced using standard hydraulic calculations and also a non-linear unit hydrograph flow model. This flood caused considerable damage to the lower part of the village.

5.  Flow Behavior around a Coated Pipeline Embedded Partly in a Permeable Seabed.

H.Y. Chang, L.H. Huang, M.Y. Lin, K.H. Chang.

Department of Civil Engineering, Hydrotech Research Institute, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan, China.

Abstract :

In order to explore the possible mechanisms involved in submarine pipeline problems, a simplified model, made up of a coated pipeline embedded partly in a rigid permeable seabed, is proposed. For periodically oscillating flows, the standard boundary element method is applied to examine the fundamental characteristics of the flow field around the pipe. Fluid flow in the porous media is assumed to obey Darcy’s law and that in the pure-water region the potential theory. The use of the regular perturbation technique entirely prohibits the occurrence of highly ill-conditioned linear systems, arising due to the substantial difference in order of magnitude among the flux and pressure continuity conditions across the soil-and coating-water interfaces. Tentative numerical tests show positive results. The employment of a porous pre-coated layer is an effective treatment for reducing the high flow-induced pressure in localized regions, and, therefore, the potential piping effect might be suppressed.

6.  Flow field and density variation for an internal solitary wave evolution over a trapezoidal topography.

Ming-Hung Cheng, Chih-Min Hsieh, Robert R. Hwang, etc.

Department of System Engineering and Naval Architecture, National Taiwan Ocean University, Keelung 20224, Taiwan, , China.

Abstract :

While shoaling from deep water in a stratified ocean, an internal solitary wave (ISW) may experience waveform inversion on a continental margin. Despite the widely accepted belief among oceanographers thatthe inversion may commence at the turning point, the detailed process of waveform evolution for a depression ISW shoaling remains rather limited. In order to clarify this interesting phenomenon, laboratory experiment and numerical simulation are conducted on the evolution of an ISW of depression across a slope connecting a horizontal plateau which resembles a pseudo slope-shelf topography. Experimental results indicate that the process of waveform inversion took place after internal run-down, hydraulic jump, vortex motion and run-up on the front slope, prior to the wave propagation on the plateau. In this paper, a numerical method to solve the Reynolds-averaged Navier Stokes equation using the k-ε model for the turbulent closure is adopted for explicit calculation of the velocity field when a depression ISW propagates over pseudo slope-shelf topography. The numerical modelling reveals the variation of flow field and density profile as an ISW propagates across the slope-shelf and waveform inversion on the plateau. Based on these numerical results, a counterclockwise self-generated vortex above the wavetrough diminishes and a clockwise one under the crest prior to the leading trough increases on the plateau after the wave encounters the submarine obstacle.

7.  Transversal internal seiches in basin of variable depth and continuous stratification.

I.V. Sturova.

Lavrentyev Institute of Hydrodynamics of SD RAS,pr. Lavrentyeva 15, Novosibirsk, 630090, Russia。

Abstract :

Internal seiche solutions are evaluated for arbitrary bathymetry and continuous stratification using a linear, inviscid, 2D numerical model. The influence of the earth’s rotation on internalseiche is ignored. As a test case, internal seiche solutionsare computed for the transverse cross-section of Lake Teletskoye. The results for continuous stratification are compared with the approximate solutions for two-layer and three-layer models. For continuous stratification, the domain of the cross-section was discretized using finite differences on a rectangular grid, which transforms the equation for the stream function into a generalized algebraic eigenvalue problem. For two-layer and three-layer density profiles, the eigenvalue problem was solved by spectral method. It is shown that internal seiche structure is highly dependent on both bathymetry and stratification. The accurate modeling of seishes therefore requires the use ofrealistic density profiles and basin shapes.

8.  Prediction of Steady Performance of Contra-Rotating Propellers including Wake Alignment.

Y. Inukai,T. Kanemaru, J. Ando.

Japan Marine United Corporation,Mita Bellju Building, 36-7, Shiba5-chome, Minatoku, Tokyo, 108-0014, Japan.

Abstract :

To reduce fuel oil costs and emission of greenhouse gases of ships in operation, application of Contra-Rotating Propellers (CRP) will be one of the solutions, which have high propulsive efficiency. Although several estimation methods of predicting open water characteristics of CRP have been developed in the past, few methods treat trailing wake geometry accurately, which influences much on estimation accuracy. CRP makes the flow around the propellers more complicated compared with conventional single propeller because the aft and forward propeller interact each other strongly. In order to improve estimation accuracy, more rigorous treatment of the trailing wake geometry is desirable. This paper presents a calculation method, taking deformation of trailing wake accurately into account. The method is based on a simplified surface panel method “SQCM” which satisfies the Kutta condition easily. The wake vortex lines are arranged in accordance with the direction of the flow including induced velocity by both propellers. We show some calculated results and validate them by comparing with experiments in this paper. The calculated results with deformed wake agrees very well with the experiment, while the calculated results without deformed wake always overestimate the thrust and torque of the aft propeller.

9.  Using specialized natural condition maps and hydrodynamical simulation results to be based on marine spatial planning of Phu Quoc – Con Dao Islands areas.

Q. N. Hoang, T. X. Bui, T. H. Dao, etc.

Marine Science Department – Hanoi University for Natural Resources and Environment, Hanoi, Vietnam.

Abstract :

This report approaches Marine Spatial Planning (MSP) with two first steps which are: preparing scientific basic and setting planning. In order, those tasks identifyboundary and planning periods of these areas. In our research, the natural condition maps are firstly built within the boundaries which are identified the beginning moments;  we continue to use the results of hydrodynamic and hydro-air dynamic simulation that are based on using MIKE 21. With orientation of building specialized maps that inherit the results of simulations, we introduce maps which describe climate in Phu Quoc – Con Dao marine areas space with scale 1:200,000. All these first tasks are a part of the process of conducting national level research “Research, identification of scientific arguments and proposal for orientation of Phu Quoc – Con Dao Marine Spatial Planning for sustainable development”.

10.  Identification speed of sea level rise at observed stations in Eastern and Western coast of Vietnam Southern Part.

T. X. Bui, Q. N. Hoang, T. D. Bui, T. H. Dao, L. V. Vu, L. Nguyen.

Marine Science Department – Hanoi University for Natural Resources and Environment, Hanoi, Vietnam.

Abstract :

The GEO2TECDI – SONG project in cooperation with Thailand and EU about marine surveying concluded that speed of sea level rise (SLR) in Thailand Gulf fluctuated between 3.2-5.8 mm/year which was higher than the speed of mean SLR in the World. This paper that initially calculates and analyses the trend of fluctuation in sea level in long time reaches a conclusion that the speed of SLR in which was measured at Vietnam stations fluctuated between 1.2-4.2 mm/year. This data is believed to be suitable for data surveying from satellite altimetry in GEO2TECDI – SONG project.
The result of identification SLR that was measured at Vietnam Southern stations was based on short-different surveyed water level. However, this paper contributes togeneral conclusion about the speed of SLR in Eastern and Western coast of Vietnam Southern part that has been high and increased for last 10 years.

11.  Numerical Modelling of the Circulation Flow Movement of the Zhoushan LNG Berth and Improvement Scenarios.

M.X. Xie, X.Li, H.B.Zhao, Y.Cai.

Coastal and Estuarine Engineering Research Center, Tianjin Research Institute for Water Transport Engineering,2618 Xingang erhao Road, Tianjin, 300456, Chin.

Abstract :

The planned Zhoushan LNG berths locate near the northeastern corner of a large island. Using a two-dimensional hydrodynamic numerical model, the tidal current motion characteristics of the study area are simulated. The result shows that a circulation cell is generated by the strong flooding currents bypassing the adjacent reefs, and it initiates from their western side. The original berth locations could be significantly affected by the circulation flows. In order to avoid the circulation flows, two effective regulation scenarios could be considered, and they are (1) move the berths 300m to the west, and (2) build a short breakwater to link the reefs to move the circulation center away from the berths.

12.  Numerical Simulation on Coupled Effect between Ship Motion and Liquid Sloshing under Wave Action.

S.C. Jiang, B. Teng, Y. Gou, L. Lu, W. Bai.

State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology,Dalian 116024, China. Department of Civil and Environmental Engineering, National University of Singapore, Singapore, 117576.

Abstract :

Three-dimensional coupled model is established for considering the motion response of ship in waves coupled with sloshinginduced internal sloshing and their effects on sloshing-induced impact loads. The linear ship motion is solved using an impulseresponse-function (IRF) method, while the viscous two-phase flow model with VOF interface capture technique based OpenFOAM package is established for solving the internal liquid sloshing problem. Numerical simulations are conducted to investigate the coupled effects between Ship Motion and Liquid Sloshing, including the global ship response and local sloshing impact loading. It is found that the coupling effects are dominant for low-filling conditions. The roll RAOs show typical antirolling effect, so that the roll motion decreases dramatically near ship motion resonance and double peaks at sloshing motion resonant frequencies can be observed. The nonlinearity of sloshing flows can result in the prediction of different motion RAOs for different incident wave amplitude, especially around the resonant frequencies. In the present numerical simulation, it can be seen that the sloshing pressures have no impulsive characters around ship motion resonant frequency. Whereas, near sloshing resonant frequency, the inside sloshing pressures have evident impulsive characters and its magnitude is larger than that of ship motion resonant frequency, meaning that the violent sloshing pressures will act on internal structure and it is the controlling condition for cargo structural damage design. The higher-order harmonics of the sloshing moment are filtered out by the system. The steady-state ship motion is almost linear and sinusoidal character with the frequency of the linear incident waves, although the evident impulsive phenomena can be observed in sloshing moment signals. It implies that the higher-order harmonics of the sloshing moment are filtered out by the system.

13.  Wave drift forces estimation for the preliminary design of dynamic positioning systems.

M. Viviani, G. Panzalis, D. Ruscelli, L. Sebastiani, R. Depascale.

Department of Electrical, Electronic, Telecommunication Engineering and Naval Architecture, Università di Genova, Via Montallegro 1, Genova, 16145, Italy.

Abstract :

In present work, a simplified methodology able to provide a sufficiently accurate assessment of wave drift forces is presented, with the aim of providing a procedure which may be applied in the preliminary stages of the design, when the technical data of the ship (such as the hull forms) are not yet available, and only main hull parameters are present. In particular, the 3D panel seakeeping program PRECAL, developed at Cooperative Research Ships (CRS) is utilised. At first, its capabilities are verified comparing numerical results with literature data, showing the code reliability. Then, a series of simplified ellipsoidal hull forms have been analysed and compared with more complex hull forms in order to identify a criterion of equivalence, which may be used when a detailed description of the hull form is not available. Results show that the proposed simplified methodology is reliable and enough accurate to allow a proper sizing of the propulsion and manoeuvring systems of a ship with dynamic positioning requirements in the preliminary stage of the design.

 

14.  Comparison of different scaling methods for model tests with CLT propellers.

J. GONZÁLEZ-ADALID, M. PÉREZ SOBRINO, A. GARCÍA GÓMEZ, etc.

SISTEMAR – Peñalara, 2, Bloque B, 1ºJ, 28224Pozuelo de Alarcón, Madrid, Spain.

Abstract :

CLT and other tip loading propellers designs can be checked by model tests as in the case of conventional propellers. In this paper the problem of the scaling of the model tests results of these propellers is reviewed. A way of solving this problem consists in the introduction of new procedures for scaling of the Open Water model tests results while maintaining the rest of the scaling procedures for resistance and propulsion tests. ITTC’78 standard method is widely used but some Institutes and Model Basins have their own more or less similar procedures. A series of technical approaches used for the scaling of Open Water tests results are presented here and applied to a reference case that has been very deeply studied in several Research Projects. The conclusion is that it is definitely necessary to use specific Open Water model tests results scaling procedure for CLT propellers in order to obtain full scale predictions with the same level of accuracy than in the case of conventional propellers.

 

15.  Dimension control of the ventilated supercavity in the maneuvering motion.

W. Zou, H. Liu.

MOE Key Laboratory of Hydrodynamics, Department of Engineering Mechanics, Shanghai Jiao Tong University, Shanghai, 200240, China.

Abstract :

Dimension control of ventilated supercavity is of significance to realize the controllability and maneuverability of supercavitating vehicle by regulating its hydrodynamic distribution. The ventilation control system is designed using control valve with equal percentage flow characteristic. Based on the control system and maneuvering ventilated supercavity model, the control algorithm is developed to regulate supercavity dimensions on the three-dimensional maneuvering trajectory. Control simulations of supercavity with constant dimensions are carried out using the algorithm, and control performances are evaluated. The algorithm is finally proved to be feasible by simulations.

16.  Hydrodynamic analysis on the typical underwater gliders.

Zh. Ma, Y.J. Chen, H.X. Chen, J. Kuang.

China Ship Scientific Research CenterShanghai Branch, No. 185, Gaoxiong Road, Shanghai, 20011, China.

Abstract :

The underwater glider changes its weight and distribution on the body through the battery, so as to move up and down and move forward in the sea. It has many advantages such as a long endurance, and a long operational range with its unique device. So it cannot evaluate the performance of the underwater glider only by the drag, the energy consumption is also one of the key factors. In this paper, the gliding efficiency isproposed according to the transfer efficiency from the gravitational potential energy to the available work, and the performances of three typical underwater gliders from multi-angles are evaluated, such as the drag, power conversion ratio and barycenter's offset. So that glide performance and energy consumption in various motion states can be analyzed. As a result, that can provide a theoretical basis for the further study of underwater glider.

17.  Numerical study of wave interaction with two bodies in close proximity.

D.Z. Ning, X.J. Su, B. Teng.

State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, 116024, China

Abstract :

The numerical investigations on nonlinear water wave interaction with two-bodies in close proximity are reported based on a fully nonlinear numerical wave tank (NWT) model in 2D. The model is developed using a time-domain higher-order boundary element method (HOBEM) combined with a mixed Eulerian-Lagrangian technique and a 4th-order Runge-Kutta scheme as a time marching process. The source generation technique is used to generate the input waves, so that the reflected waves from the object can pass through the incident surface and no re-reflection occurs. An empirical viscous parameter is used on the free surface conditions in the gap to approximatethe viscous effect of the vortex or flow separation. By comparison with the published experimental and numerical data, the proposed model is validated. The influence of incident wave height and frequency on the surface elevation in the gap, wave loads, wave height at the lee side and the weather side of the structure is studied.

 

18. Rudder-propeller interaction: Analysis of different approximation techniques.

D. Bruzzone, S. Gaggero, C. Podenzana Bonvino, D.Villa, M. Viviani.

DITEN, University of Genova,Via Montallegro 1 Genova, Italy.

Abstract :

This paper addresses the problem of the numerical evaluation of the forces exerted byrudder/propeller complex; in particular, considering the common framework of RANS computations, different possible approximations of the propeller effect are taken into account, starting from the simplest uniform actuator disk and moving successively to an actuator disk with radial distributions of axial and tangential forcesand then to a set of unsteady body forces, computed by a panel method, representative of the rotating pressure field of the propeller. All the results, in terms of global mean forces on the rudder and of fluctuating components and flow field, are compared to the full RANS computations and to the experimental results in model scale for the same configuration. The comparison of the results allows to identify the merits and the shortcomings of the different approaches, in order to select the best ones for the various possible applications, having in mind the necessity to keep the computational efforts to a reasonable level during the design phases.

 

19.  Simulating Flooding in Complex Underground Spaces with GPU-based SPH Method.

J.S. WU, Y.P. QIN, X.B. YANG,H. ZHANG,R.A. DALRYMPLE.

Department of Safety Engineering, China University of Mining & Technology, Beijing, 100083, China.

Abstract :

In this paper, the mesh-free Smoothed Particle Hydrodynamics (SPH) method with the Graphic Processing Unit (GPU) parallel computing technique employed (GPUSPH) is used to investigate dam-break flooding in co mp le x urban underground spaces. SPH explicitly conserves mass and linear momentum, and does not require explicit interface tracking treatment so that geometrically complex and moving boundaries can be handled without undue difficulty. Taking advantage of aforementioned attractive strengths of SPH and the powerful ability of GPU parallel computing techniques, the following two underground inundation cases involving millions of particles (computational nodes) are examined: i) flooding in a two-level underground space connected by staircases with two 90-degree turns, ii) flooding involving three floating objects in a underground facility. Numerical results fairly reproduce the complex underground inundation process, and reasonably present complicated flooding features involving interactions of flooding flow and floating objects and staircases with 90-degree turns, which indicates SPH method is an alternative tool for the modeling of flooding in complex urban underground spaces.

 

20.  Effects of the vertical launching parameters on the underwater vehicle movement.

Z.X.Gong, C.J. Lu, J.Y. Cao, J. Li, X. Chen, Y. Chen.

Department of Mechanics, MOE Key Laboratory of Hydrodynamics, Shanghai Jiao Tong University. Shanghai, China.

Abstract :

The entire process of an underwater vehicle movement, from vertically launching out of a canister to exiting the sea level of the water, is numerically simulated by means of an axisymmetric model containing the VOF multiphase model and Standard turbulence model. The effects of the launching parameters on the movement of the vehicle are studied. The primary parameters considered here include launching velocity, depth and pressure. While one single launching parameter is focused, the other parameters keep constant. The evolution  of the ventilated cavitation around the vehicle side as well as the gas bubble under the bottom are exhibited. For each launching parameter, its impacts on the vehicle trajectory are illustrated. The results show that the shape of the ventilated cavitation and the gas bubble are changed while altering the launching parameters, and elucidate its corresponding influence on the vehicle movement. The variations of each physical variable under different launching parameters have the similar tendency, however, the contrast are obvious.