scholarly journals PROBING INTO THE EFFECTS OF CAVITATION ON HYDRODYNAMIC CHARACTERISTICS OF SURFACE PIERCING PROPELLERS THROUGH NUMERICAL MODELING OF OBLIQUE WATER ENTRY OF A THIN WEDGE

Brodogradnja ◽  
2017 ◽  
Vol 69 (1) ◽  
pp. 151-168 ◽  
Author(s):  
Nasrin Javanmardi ◽  
◽  
Parviz Ghadimi ◽  
Sasan Tavakoli
Keyword(s):  
Numerical Modeling ◽  
Water Entry ◽  
Hydrodynamic Characteristics ◽  
Thin Wedge

scholarly journals Numerical Investigation on the Water Entry of Several Different Bow-Flared Sections

2020 ◽  
Vol 10 (22) ◽  
pp. 7952
Author(s):  
Qiang Wang ◽  
Boran Zhang ◽  
Pengyao Yu ◽  
Guangzhao Li ◽  
Zhijiang Yuan
Keyword(s):  
Stokes Equations ◽  
Water Entry ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Surface Evolution ◽  
Mesh Method ◽  
The Difference ◽  
Dynamics Method

The bow-flared section may be simplified in the prediction of slamming loads and whipping responses of ships. However, the difference of hydrodynamic characteristics between the water entry of the simplified sections and that of the original section has not been well documented. In this study, the water entry of several different bow-flared sections was numerically investigated using the computational fluid dynamics method based on Reynolds-averaged Navier–Stokes equations. The motion of the grid around the section was realized using the overset mesh method. Reasonable grid size and time step were determined through convergence studies. The application of the numerical method in the water entry of bow-flared sections was validated by comparing the present predictions with previous numerical and experimental results. Through a comparative study on the water entry of one original section and three simplified sections, the influences of simplification of the bow-flared section on hydrodynamic characteristics, free surface evolution, pressure field, and impact force were investigated and are discussed here.

scholarly journals Gravity effects in the water entry problem

1965 ◽  
Vol 5 (4) ◽  
pp. 427-433 ◽  
Author(s):  
A. G. Mackie
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Boundary Conditions ◽  
Formal Solution ◽  
Water Entry ◽  
Initial State ◽  
Non Linear ◽  
Gravity Effects ◽  
Linearized Theory ◽  
Thin Wedge

The following paper is a sequel to the author's earlier paper [2]. In that paper some general results were obtained which described the motion of a fluid with a free surface subsequent to a given initial state and prescribed boundary conditions of a certain type. The analysis was based on a linearized theory but gravity effects were included. Viscosity, compressibility and surface tension effects were neglected. Among the problems treated was that of the normal symmetric entry of a thin wedge into water at rest. This Water entry problem has attracted a considerable amount of attention since the pioneer paper by Wagner [5]. Both linear and non-linear approximations have been used but all papers apart from [2] neglect gravity on the assumption that in the early stages of the penetration this is unimportant. One of the objects of [2] was to determine the solution with the gravity terms retained. A formal solution was obtained but no attempt was made to analyse this quantitatively. In the present paper we examine the extent of this effect in some detail. It will be of help to the reader to have some familiarity with the first three or four sections of [2] but in order to make the present paper self-contained we shall first reintroduce the notation used there and quote the necessary results from that paper without proof.

Numerical Modeling of Launching Steel Jackets With Consideration of Water Entry Forces

2008 ◽  
Author(s):  
Nikzad Nourpanah ◽  
Moharram D. Pirooz
Keyword(s):  
Numerical Modeling ◽  
Numerical Model ◽  
Impact Force ◽  
Water Entry ◽  
Operating Conditions ◽  
Solution Technique ◽  
Large Magnitude ◽  
Environmental Loading ◽  
Fluid Forces ◽  
Offshore Jackets

In this paper, a numerical model describing launching of offshore jackets from barge is developed. In addition to commercial software’s, water entry forces on jacket members and an implicit Newmark solution technique are included in the model. The results are in general agreement with other numerical software’s available (SACS). Special attention is paid to the fluid forces acting on jacket and the importance of each one. Also it is observed that water entry forces on horizontal jacket elements are very significant and may locally govern the design of these members. This force is more important for horizontal slender members near the mud-line, which do not experience significant environmental loading in operating conditions. Therefore the water entry impact force with large magnitude can cause over-stress and/or ovalling. It is also observed that taking water entry forces in account modifies the jacket trajectory in little extent.

Numerical evaluation of the hydrodynamic impact characteristics of the air launched AUV upon water entry

2020 ◽  
Vol 34 (14) ◽  
pp. 2050149
Author(s):  
Ahmad Zamir Chaudhry ◽  
Guang Pan ◽  
Yao Shi
Keyword(s):  
High Speed ◽  
Impact Load ◽  
Research Work ◽  
Computational Cost ◽  
Water Entry ◽  
Structure Design ◽  
Hydrodynamic Characteristics ◽  
Ale Method ◽  
The Impact ◽  
Selection Of

In this paper, water entry process of air launched AUV is investigated by employing fully coupled finite element method and arbitrary Lagrange–Euler formulation (FEM-ALE) and using penalty coupling technique. Numerical model is established to describe the hydrodynamic characteristics and flow patterns of a high-speed water entry AUV. The effectiveness and accuracy of the numerical simulation are verified quantitatively by the experiments of the earlier study. Selection of suitable advection method and mesh convergence study is carried out during experimental validation process. It is found that appropriate mesh size of impact domain is crucial for numerical simulations and second-order Van Leer advection method is more appropriate for high speed water entry problems. Subsequently, the arbitrary Lagrange–Euler (ALE) algorithm is used to describe the variation laws of the impact load characteristics with water entry velocities, water entry angles and different AUV masses. Dimensionless impact coefficient of AUV at different velocities calculated using ALE method is compared with SPH results. This reveals that ALE method can also simulate the water entry process accurately with less computational cost. This research work can provide beneficial reference information for structure design of AUV and for selection of the water entry parameters.

scholarly journals МОДЕЛЮВАННЯ ГІДРОДИНАМІКИ КОРПУСА СУДНА З УРАХУВАННЯМ БІОЛОГІЧНОГО ЗАБРУДНЕННЯ

2019 ◽  
Vol 39 (1) ◽  
pp. 14-21
Author(s):  
В.В. Афтанюк ◽  
◽  
◽  
◽  
Keyword(s):  
Numerical Modeling ◽  
Fluid Velocity ◽  
Hydrodynamic Characteristics ◽  
Clean Surface ◽  
Environmental Friendliness ◽  
Fuel Supply ◽  
Biological Contamination ◽  
Coating Roughness ◽  
Biological Contaminants ◽  
Conducting Research

The article presents a study of the effect of roughness and waviness (including taking into account bioburden) on the hydrodynamic characteristics of the vessel. To carry out the experiments, a model of the hull of the vessel was developed, which includes the submerged underwater part of the vessel and a special channel in which the flow is modeled. Biological contamination (bio-fouling of the underwater hull) of seaships and river-ships is a problem for all fleets. To maintain the speed of a ship with biological contamination, the hull requires an increase in diesel power by increasing the fuel supply. To maintain the speed of a ship with biological contamination, the requires an increase in diesel power by increasing the fuel supply. It affects the economy and environmental friendliness of maritime transport. The model investigated the change in fluid velocity during flow around a "clean surface" with a roughness of 75, 100, 125 microns. Numerical modeling showed a slight effect of changes in coating roughness for a “clean surface”. Numerical modeling for a surface contaminated with biological contaminants (roughness of 750 micron) revealed a significant effect on the change in fluid velocity along the hull. The developed model can be used when conducting research for a comparative assessment of the energy efficiency of ships.

Hydrodynamic Characteristics of Water-Entry Blades

2003 ◽  
Author(s):  
Hisashi Kamikubo ◽  
Dasisuke Ikegami ◽  
Kotaro Sato ◽  
Shinichi Mizuno ◽  
Okitsugu Furuya ◽  
...  
Keyword(s):  
High Speed ◽  
Water Entry ◽  
Hydrodynamic Characteristics ◽  
Complex Nature ◽  
Two Dimensional ◽  
Propulsive Efficiency ◽  
Triangular Shape ◽  
Speed Up

The partially submerged ventilated propeller (PSVP) is of interest to many researchers and ship builders due to its high propulsive efficiency and thrusting capability at the high sea states. As a matter of fact, it is now used for those ships of high speed up to 50 knots. However, its full capability is not totally utilized to date due to the complex nature of both hydrodynamic and material problems. It is a well known fact that PSVP fails materially after a certain period of time. The cause of the failure is not fully understood to date. Although PSVP is tested in the form of propeller for many years, the detailed ventilation phenomena, i.e., blade entry problems are not fully investigated. The paper presented herein will discuss about the results of blade entry experiments with two-dimensional blades of triangular shape used.

Position detection method and hydrodynamic characteristics of the water entry of a cylinder with multidegree motion

2020 ◽  
Vol 61 (2) ◽  
Author(s):  
Weixue Xia ◽  
Cong Wang ◽  
Yingjie Wei ◽  
Jiachuan Li ◽  
Yuanyuan Li ◽  
...  
Keyword(s):  
Detection Method ◽  
Water Entry ◽  
Hydrodynamic Characteristics ◽  
Position Detection

scholarly journals Numerical Simulation on the Cavitation Flow of High Speed Oblique Water Entry of Revolution Body

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Qing Mu ◽  
Yipin Lv ◽  
Kangjian Wang ◽  
Tianhong Xiong ◽  
Wenjun Yi
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Water Entry ◽  
Hydrodynamic Characteristics ◽  
Multiphase Model ◽  
Cavitation Flow ◽  
Entry Angle ◽  
Positive Direction ◽  
Cavity Shape ◽  
The Revolution

To explore the effects of water entry angle on the cavitation flow field of high-speed revolution body, based on the finite volume method, VOF (Volume of Fluid) multiphase model, Schnerr-Sauer cavity model, SST k-ω turbulence model, and dynamic mesh method, numerical simulation for modeling the oblique water entry of revolution body at high speed is performed. The evolution laws of cavity shape, motion characteristics, and hydrodynamic characteristics of revolution body at different water entry angles are analyzed. The results show that the numerical calculation method can effectively simulate the change of cavity shape during the water entry of the revolution body. With the increase of water entry angle, the uplift of liquid level decreases in the positive direction of the open cavity and increases in the negative direction. The angle of water entry has little effect on the velocity of the revolution body. The larger the angle of water entry, the greater the peak pressure and the faster the pressure decay at the moment of water entry.

Sign in / Sign up

Export Citation Format

Share Document