Experimental Study of Water Entry and Exit of a Circular Cylinder at Free Surface: An Educational Approach

2012 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Arman Molki
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Circular Cylinder ◽  
Flow Visualization ◽  
High Speed ◽  
Mechanical Engineering ◽  
Water Entry ◽  
Experimental Setup ◽  
Entry And Exit ◽  
Educational Approach

This paper outlines a proposed experimental setup for characterizing the vertical motion of a horizontal circular cylinder through a free surface. Both water entry and exit are studied. The proposed experimental setup will enhance the student’s learning of the hydrodynamic impact phenomena. The experimental study is based on the flow visualization of free surface and surrounding water during the cylinder’s motion. The fluid flow phenomenon around the submerged cylinder is investigated using high-speed digital imaging and Particle Image Velocimetry (PIV). The proposed experiment is used as part of an undergraduate mechanical engineering fluid mechanics course taught at a university, which aims to educate young male and female engineers for the local oil and gas industry and particularly for the companies involved in sponsoring the institution. The details of the flow visualization system and teaching strategy for implementing this experiment in a Mechanical Engineering curriculum is discussed.

Water Entry and Exit of a Horizontal Circular Cylinder

2005 ◽  
Author(s):  
Xinying Zhu ◽  
Odd M. Faltinsen ◽  
Changhong Hu
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Surface Deformation ◽  
Vertical Motion ◽  
Water Entry ◽  
The Body ◽  
Computational Domain ◽  
Entry And Exit ◽  
Constrained Interpolation ◽  
Horizontal Circular Cylinder

This paper describes the fully nonlinear free-surface deformations of initially calm water caused by water-entry and water-exit of a horizontal circular cylinder with both forced and free vertical motions. This has relevance for marine operations as well as for the ability to predict large amplitude motions of floating sea structures. A new numerical method called the CIP (Constrained Interpolation Profile) method is used to solve the problem. In this paper, the circular cylinder and free surface interaction is treated as a multiphase problem, which has liquid (water), gas (air) and solid (circular cylinder) phases. The flow is represented by one set of governing equations, which are solved numerically on a non-uniform, staggered Cartesian grid by a finite difference method. The free surface as well as the body boundary is immersed in the computational domain. The numerical results of the water entry and exit force, the free surface deformation and the vertical motion of the cylinder are compared with experimental results, and favorable agreement is obtained.

Water Entry and Exit of a Horizontal Circular Cylinder

2006 ◽  
Vol 129 (4) ◽  
pp. 253-264 ◽  
Author(s):  
Xinying Zhu ◽  
Odd M. Faltinsen ◽  
Changhong Hu
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Surface Deformation ◽  
Vertical Motion ◽  
Water Entry ◽  
The Body ◽  
Computational Domain ◽  
Entry And Exit ◽  
Constrained Interpolation ◽  
Horizontal Circular Cylinder

In this paper we describe the fully nonlinear free-surface deformations of initially calm water caused by the water entry and water exit of a horizontal circular cylinder with both forced and free vertical motions. Two-dimensional flow conditions are assumed in the study. This has relevance for marine operations as well as for the ability to predict large amplitude motions of floating sea structures. A new numerical method called the CIP (Constrained Interpolation Profile) method is used to solve the problem. In this paper, the circular cylinder and free surface interaction is treated as a multiphase problem, which has liquid (water), gas (air), and solid (circular cylinder) phases. The flow is represented by one set of governing equations, which are solved numerically on a nonuniform, staggered Cartesian grid by a finite difference method. The free surface as well as the body boundary is immersed in the computational domain. The numerical results of the water entry and exit force, the free surface deformation and the vertical motion of the cylinder are compared with experimental results, and favorable agreement is obtained.

Characterization of Air-Entrainment in a Plunging Water Jet System Using Image Processing: An Educational Approach

2011 ◽  
Author(s):  
Arman Molki ◽  
Lyes Khezzar ◽  
Afshin Goharzadeh
Keyword(s):  
Image Processing ◽  
Free Surface ◽  
Flow Behavior ◽  
Air Entrainment ◽  
Experimental Setup ◽  
Water Mixture ◽  
Educational Approach ◽  
Image Processing Techniques ◽  
Processing Techniques

This paper outlines a proposed experimental setup and image processing techniques using MATLAB for the characterization of the average dynamic behavior of the air/water mixture under the free surface of water penetrated by a plunging jet. The proposed setup focuses on the dynamics of air entrainment below the free surface and the identification of the major regimes related to the entrainment process of bubbles in water, namely: (a) no-entrainment, (b) incipient entrainment, (c) intermittent entrainment, and (d) continuous entrainment. The experimental setup allows students to observe the flow behavior below the free liquid surface and determine the penetration depth of the bubble plumes using image processing techniques in MATLAB. The focal point of the experiment is image analysis for qualitative and quantitative characterization of the bubble plume.

Numerical Investigation of Air Cavity Formation During the High-Speed Vertical Water Entry of Wedges

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Jingbo Wang ◽  
Odd M. Faltinsen
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Nonlinear Boundary ◽  
Water Entry ◽  
Similarity Solutions ◽  
Free Surface Flows ◽  
Cavity Formation ◽  
Air Cavity ◽  
Numerical Instabilities ◽  
Entry Velocity

In this paper, a nonlinear boundary element method (BEM) is developed for investigating air cavity formation during the high-speed water entry of wedges. A technique is proposed for dynamic re-gridding of free surface boundaries. This technique applies to both equally and nonequally spaced grids, and it is able to suppress the numerical instabilities encountered using a BEM for simulating free surface flows. The authors also develop a purely numerical method to simulate nonviscous flow separation, which occurs when the flow reaches the knuckle of the wedge. The present nonlinear BEM has been verified by comparisons with similarity solutions. We also compare numerical results with experimental results. Finally, we give a numerical prediction of the evolution of the cavity until the closure of the cavity, and the influence of the initial entry velocity, wedge mass, and deadrise angle on the characteristics of the transient cavities is investigated.

Validation of Open-Source SPH Code DualSPHysics for Numerical Simulations of Water Entry and Exit of a Rigid Body

2017 ◽  
Author(s):  
Sergei K. Buruchenko ◽  
Ricardo B. Canelas
Keyword(s):  
Free Surface ◽  
Rigid Body ◽  
Stokes Equations ◽  
Offshore Structures ◽  
Water Entry ◽  
Surface Flow ◽  
Rigid Body Dynamics ◽  
Structural Safety ◽  
Entry And Exit ◽  
Momentum Exchange

Water entry and exit of a body is an important topic in naval hydrodynamics as these phenomena play relevant roles both for offshore structures and vessels. Water entry and exit events are intrinsically transient and represent intense topological changes in the system, with large amounts of momentum exchange between phases. At its onset, they can be characterized by highly localized, both in space and time, loads on the vessel, influencing both the local structural safety of the structure and the global loads acting on it. The DualSPHysics code is proposed as a numerical tool for the simulation of fluid and floating object interaction. The numerical model is based on a Smoothed Particle Hydrodynamics discretization of the Navier-Stokes equations and Newton’s equations for rigid body dynamics. This paper examines the water impact, fluid motions, and movement of objects in the conventional case studies of object entry and exit from still water. A two dimensional body drop analysis was carried out demonstrating acceptable agreement of the movement of the object with published experimental and numerical results. The velocity field of the fluid is also captured and analyzed. Simulations for water entry and exit of a buoyant and neutral density cylinder compares well with previous experimental, numerical, and empirical studies in penetration, free surface evolution and object kinematics. These results provide a good foundation to evaluate the accuracy and stability of the DualSPHysics implementation for modeling the interaction between free surface flow and free moving floating objects.

scholarly journals Unsteady forces on spheres during free-surface water entry

2012 ◽  
Vol 704 ◽  
pp. 173-210 ◽  
Author(s):  
Tadd T. Truscott ◽  
Brenden P. Epps ◽  
Alexandra H. Techet
Keyword(s):  
Free Surface ◽  
Surface Water ◽  
High Speed ◽  
Accurate Determination ◽  
Water Entry ◽  
High Speed Imaging ◽  
Air Cavity ◽  
Unsteady Forces ◽  
Unsteady Force ◽  
Low Mass

AbstractWe present a study of the forces during free-surface water entry of spheres of varying masses, diameters, and surface treatments. Previous studies have shown that the formation of a subsurface air cavity by a falling sphere is conditional upon impact speed and surface treatment. This study focuses on the forces experienced by the sphere in both cavity-forming and non-cavity-forming cases. Unsteady force estimates require accurate determination of the deceleration for both high and low mass ratios, especially as inertial and hydrodynamic effects approach equality. Using high-speed imaging, high-speed particle image velocimetry, and numerical simulation, we examine the nature of the forces in each case. The effect of mass ratio is shown, where a lighter sphere undergoes larger decelerations and more dramatic trajectory changes. In the non-cavity-forming cases, the forces are modulated by the growth and shedding of a strong, ring-like vortex structure. In the cavity-forming cases, little vorticity is shed by the sphere, and the forces are modulated by the unsteady pressure required for the opening and closing of the air cavity. A data-driven boundary-element-type method is developed to accurately describe the unsteady forces using cavity shape data from experiments.

Oblique Water Entry and Exit of a Fully Ventilated Foil

1979 ◽  
Vol 23 (01) ◽  
pp. 43-54 ◽  
Author(s):  
D. P. Wang
Keyword(s):  
High Speed ◽  
Horizontal Layer ◽  
Water Entry ◽  
Control Surface ◽  
Entry And Exit ◽  
Sea State ◽  
Ratio Effect ◽  
Present Solution ◽  
Arbitrary Thickness ◽  
Advance Ratio

The oblique entry of a two-dimensional, fully ventilated foil into a horizontal layer of water of arbitrary thickness is considered. When the thickness of the layer is finite, exit of the foil from the layer is studied. The present work is an extension of a previous one,2 in which only vertical entry and exit of the foil were considered. The consideration of oblique entry makes the present solution useful in studying not only the advance ratio effect on a partially submerged supercavitating propeller but also many other problems, such as the high-speed water entry and exit of a wing or a control surface, the operation of a high-speed hydrofoil in a high sea state. The results obtained in this work indicate that the force and moment coefficients of a foil decrease as the advance ratio is reduced.

Turbulent fluid-structure interaction of water-entry/exit of a rotating circular cylinder using SPH method

2015 ◽  
Vol 26 (08) ◽  
pp. 1550088 ◽  
Author(s):  
Jafar Ghazanfarian ◽  
Roozbeh Saghatchi ◽  
Mofid Gorji-Bandpy
Keyword(s):  
Circular Cylinder ◽  
Water Entry ◽  
Numerical Code ◽  
Navier Stokes ◽  
Inertia Force ◽  
Entry And Exit ◽  
Sph Method ◽  
Drag Forces ◽  
Rotating Circular Cylinder ◽  
Lift And Drag

This paper studies the two-dimensional (2D) water-entry and exit of a rotating circular cylinder using the Sub-Particle Scale (SPS) turbulence model of a Lagrangian particle-based Smoothed-Particle Hydrodynamics (SPH) method. The full Navier–Stokes (NS) equations along with the continuity have been solved as the governing equations of the problem. The accuracy of the numerical code is verified using the case of water-entry and exit of a nonrotating circular cylinder. The numerical simulations of water-entry and exit of the rotating circular cylinder are performed at Froude numbers of 2, 5, 8, and specific gravities of 0.25, 0.5, 0.75, 1, 1.75, rotating at the dimensionless rates of 0, 0.25, 0.5, 0.75. The effect of governing parameters and vortex shedding behind the cylinder on the trajectory curves, velocity components in the flow field, and the deformation of free surface for both cases have been investigated in detail. It is seen that the rotation has a great effect on the curvature of the trajectory path and velocity components in water-entry and exit cases due to the interaction of imposed lift and drag forces with the inertia force.

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