A Method of Assessment of the Liquid Sloshing Impact on Ship Transverse Stability

Liquid sloshing phenomenon taking place in partly filled ships’ tanks directly affects the stability of a vessel. However, only static calculations are carried out onboard ships nowadays and static transfer of liquid weight is taken into account in the course of routine stability calculation. The paper is focused on a dynamic heeling moment due to liquid sloshing in tanks onboard ships. The set of numerical simulations of liquid sloshing taking place in moving tanks is carried out. The realistic range of geometric parameters is taken into account. The conducted CFD simulations are experimentally verified. Finally, the method of an assessment of the liquid sloshing impact on ship transverse stability is worked out. The key point of the method is a dynamic coefficient describing relation of the researched dynamic heeling moment and the quasi‐static one in terms of dynamic stability of a vessel which is related to the weather criterion of ship stability assessment.

P. Krata Gdynia Maritime University, Gdynia, Poland

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Analysis of Dynamic Heeling Moment Due to Liquid Sloshing in Partly Filled Ship’s Tanks for Realistic Range of Rolling Periods –  Case Study

Liquid sloshing phenomenon is a result of partly filled tank motions. As a tank moves, it supplies energy to induce and sustain a fluid motion. Both the liquid motion and its effects are called sloshing. The interaction between ship’s tank structure and water sloshing inside the tank consists in the constant transmission of energy. As the ship rolls, the walls of a partly filled tank induce the movement of water. Liquid sloshing phenomenon occurring in partly filled ships tanks directly affects the stability of the vessel. However, only static calculations are carried out onboard ships nowadays and static transfer of liquid weight is taken into account in the course of routine stability calculation and
assessment. Since previous researchers reveal the necessity of dynamic approach towards liquid movement onboard ships, the investigation is focused on problems related to time dependent wave-type phenomena. This aspect is omitted in the course of standard ship stability calculations. The set of numerical simulations of liquid sloshing taking place in moving tanks is carried out. Among many obtained characteristics, the heeling moment due to sloshing is emphasized and thoroughly investigated. The realistic range of possible metacentric heights and rolling periods is examined. The influence of ship’s rolling period on the heeling moment due to liquid sloshing is analyzed for one exemplary seagoing vessel as a case study. However, the conclusions can be generalized to some degree and comprise many other ships.

Jacek Jachowski, Przemyslaw Krata, Wojciech Wawrzynski, Wojciech Wieckiewicz
Gdynia Maritime University
Department of Ship Operation
Jana Pawla II Av. 3, 81-345 Gdynia, Poland

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CAE Simulation of Water Flow Around a Ship Hull

The goal of this project was to run CAE simulations of water flow around the hull of a ship much more quickly than was possible using available resources. Current simulations took a long time to compute, limiting the usefulness and usability of CAE for this problem. For instance, on the resources currently available to the end user, a simulation of 50-60 seconds of real time water flow took two to three weeks of computational time. We decided to run the existing software on a HPC resource to realize whatever runtime gains might be achieved by using larger amounts of computing resources.

Case Study Authors – Adrian Jackson, Jesus Lorenzana, Andrew Pechenyuk, and Andrey Aksenov.

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Virtual Basin for Simulating Ship Sailing Qualities on HPC Resources

A Virtual Basin project and some features of its implementation for High-Performance Computing (HPC) are presented in this paper. There are many attempts to create virtual basin approach for ship hydrodynamic simulations over the world, and the current project is well aligned with this activity. The main features of the Virtual Basin described in this paper in contrast with the analogues are: firstly, developing a simple tool for ship designers without deep expertise in the numerical methods, and, secondly, implementing a simple access to remote HPC resources. The problems of the Virtual Basin implementation on HPC resources are shown in the example project of towing test simulation of the well-known test KCS from Gotherberg-2000 workshop.

Andrey Aksenov1 , Andrey Pechenyuk2 , Alexey Poyda3 , Eygene Ryabinkin3 , Igor Tkachenko3 , Viacheslav Ilyin3 and Vasily Velikhov3

1-) JSC “Tesis”, Moscow, Russia

2-) LLC “Digital Marine Technology”, Odessa, Ukraine

3-) National Research Centre “Kurchatov Institute”, Moscow, Russia

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Design of Hull Lines Using Modern CFD Software Package FlowVision

Design of hull lines based on simulation of viscous flow around a ship hull with the free surface (VOF Model) was provided by a commercial CFD code FlowVision. All the resistance components, wave-making resistance and viscous resistance, have been simultaneously considered in simulation. The object of research was the seagoing ship of logistical support for Russian navy. The complex design problem of providing the required propulsion qualities, towing and icebreaking characteristics was succesfully resolved largely through the active use of CAE FlowVision. The final hull lines were designed on the base of the CFD propulsion research of 8 hull form variants. The CFD results have been also verified with experimental data (error was less tahn 5 % only). As the result, the reliability and high efficiency of the used simulation approach and the FlowVision software were proved in practice. Thus CAE FlowVision has good references and perspectives for the future use in the design of hull lines for the modern ships.

A.A.Aksenov1, S.V.Zhluktov1, A.S.Petrov2, A.V.Pechenyuk3, B.N.Stankov3, Yu. Chung Cheng4

1-) Capvidia/Tesis (Moscow)

2-) SpetsSudoProekt (St. Petersburg)

3-) Digital Marine Technology (Odessa)

4-) Deanwell/Samwell Testing Inc. (Beijing/Taipei)

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Influence of Interaction Between Oil and Rubber on Valve Stem Seal Oil Leakage

The valve stem seal is an important part of any internal combustion engine. The seal supplies a lubrication of valve stem and limits emission of oil. To design reliable and long-life stem seals a numerical simulation of the seal work is used. Numerical simulation helps to understand the main features of the stem seal working cycle and estimate the changing seal characteristics because of seal aging processes. The problem of oil flow via stem seal involves fluid-structure interaction between an oil flow induced by oscillating stem and deformable seal made from rubber. The Fluid-Structure Interaction Problem is solved numerically by using two codes: Abaqus/Explicit to get deformation of rubber seal and CFD code FlowVision to simulate oil flow.

Both codes are two-way coupled by Multi Physics Manager. Simulation of the oil leakage through valve stem seal was studied for different engine rpm and for different rubber elasticity. Results from analysis show the strong dependence of the leakage on engine operating condition and elasticity of the rubber. Increasing engine speed and elasticity of the rubber result in increasing oil leakage through the seal. Moreover, increasing elasticity resulted in faster growth of the leakage with higher engine rpm. Also we found that during stem oscillation the rubber has complex motion. This motion results in wave-like changing of the clearance between the valve stem and the seal. Investigation of this effect allows predicting more accurately the properties of the valve stem seal.

A. Aksenov, K. Iliine TESIS, Russia

T. Luniewski – Capvidia,  Belgium

T. McArthy, F. Popielas, R. Ramkumar, Victor Reinz – Sealing Products Division, Dana Corporation, USA

ABAQUS Users’ Conference 2006, Page1/16

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Oil Leakage Through a Valve Stem Seal

The first valve stem seal was invented in 1958. It was made up of Buna-N (NBR) Elastomer Body, Ring retainer, Teflon insert working in a 400°F temperature environment. In the early days before the invention of valve stem seals, there was higher oil consumption, excess blow by through the valves and high wear of the valves.

The design of the valve stem seal depends on several factors since the valve stem seal works in a very complex environment. Yet the primary function of the seal is to meter the oil in the right quantity against the pressure. It resists flowing oil to vacuum. Too much oil causes extensive emissions and deposits, while too little oil causes valve seat, face and guide wear. Therefore the solution is hydrodynamic lubrication. Oil metering rate is dependent upon the valve stem diameter, oil viscosity, and stem speed.

There are several other factors that affect the oil flow rate in the valve stem seal. One of the main factors that affect long term performance of the seal is the material aging due to oil, heat and temperature, which produces lots of challenges in the design process. Since the lab aging of the seals during the design process cuts into the design time, numerical processing is needed to predict the oil flow rate. Finite element analysis (FEA) shows how the seal deforms under installation and working conditions of the engine and also determines the contact pressure between the seal and the stem that in turn determines the oil flow rate. FEA can also be used to observe the difference in contact pressure due to the changes in materialproperties due to aging. Computational fluid dynamics (CFD) methods provide calculations of the oil metering rate in channel formed by stem and deformed seal. But FEA or CFD techniques alone are unable to predict the amount of oil flow due to pressure changes between the top and bottom of the seal. Therefore the Fluid Structure Interaction (FSI) techniques is necessary to provide a comprehensive study the oil flow rate in the seal.

The FSI technique uses ABAQUS to predict the stem seal deformation and FlowVision to calculate the oil flow. Two-way interaction between ABAQUS and FlowVision is managed by the Multi-Physics Manager. The FSI technique couples the CFD and FEA simulation domains. The link to ABAQUS is implemented using Abaqus user subroutines and does not involve any other intermediate data structures.

A. Aksenov, K. Iliine TESIS, Russia
T. Luniewski, Capvidia, Belgium
T. McArthy, F. Popielas, R. Ramkumar

ABAQUS Users’ Conference 2005, Page1/14

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