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.

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.

Free-Surface Boundary-Layer Approach to Study the Bow Vortices Generation Ahead of a Semisubmerged Horizontal Circular Cylinder

1995 ◽  
Vol 39 (04) ◽  
pp. 284-296
Author(s):  
L. R. Raheja
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Circular Cylinder ◽  
The Body ◽  
Instability Criterion ◽  
Surface Boundary ◽  
Surface Shear ◽  
Surface Boundary Layer ◽  
Surface Separation ◽  
Horizontal Circular Cylinder

In the light of experimental observation of a free-surface shear layer, the flow ahead of a semisubmerged horizontal circular cylinder is modeled as a free-surface boundary layer of concentrated vorticity joining the potential flow below it with the aim to study the generation of bow vortices theoretically. The boundary-layer equations are linearized subject to a suitable assumption and are integrated using basically the Kármán Pohlhausen method. It is found that the free surface moves slower than the layer beneath it, but there is more likelihood of bow vortices being generated by instability of velocity profile rather than by separation and backflow. This is confirmed by the nonmonotonicity in the vorticity profile and the fulfillment of the Görtler instability criterion for flow along curved boundaries, near the body upstream. The position of the point of onset of instability, as stipulated from the above observations, compares well with the position of the free-surface separation point as observed in the experiments.

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.

EFFECTS OF SURFACE TENSION ON TRAPPED MODES IN A TWO-LAYER FLUID

2015 ◽  
Vol 57 (2) ◽  
pp. 189-203 ◽  
Author(s):  
S. SAHA ◽  
S. N. BORA
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Circular Cylinder ◽  
Boundary Value Problems ◽  
Finite Depth ◽  
Trapped Modes ◽  
Trapped Waves ◽  
Linearized Theory ◽  
Horizontal Circular Cylinder ◽  
Effect Of Surface

We consider a two-layer fluid of finite depth with a free surface and, in particular, the surface tension at the free surface and the interface. The usual assumptions of a linearized theory are considered. The objective of this work is to analyse the effect of surface tension on trapped modes, when a horizontal circular cylinder is submerged in either of the layers of a two-layer fluid. By setting up boundary value problems for both of the layers, we find the frequencies for which trapped waves exist. Then, we numerically analyse the effect of variation of surface tension parameters on the trapped modes, and conclude that realistic changes in surface tension do not have a significant effect on the frequencies of these.

Comparison of Single and Overset Grid Techniques for CFD Simulations of a Surface Effect Ship

2014 ◽  
Author(s):  
Colton G. Clark ◽  
David G. Lyons ◽  
Wayne L. Neu
Keyword(s):  
Free Surface ◽  
Surface Effect ◽  
The Body ◽  
Computational Domain ◽  
Overset Grid ◽  
Hexahedral Mesh ◽  
Surface Effect Ship ◽  
Mesh Resolution ◽  
Refined Meshes ◽  
Air Cushion

Overset, or Chimera meshes are used to discretize the governing equations within a computational domain using multiple meshes that overlap in an arbitrary manner. The overset mesh technique is most applicable to problems dealing with multiple or moving bodies. In order to extend existing full craft CFD (RANS) simulations of a surface effect ship (SES) into shallow water and maneuvering cases, an overset mesh is needed. Deep water simulations were carried out using both single and overset grid techniques for evaluation of the overset grid application. The single grid technique applies a hexahedral mesh to the fluid domain and SES geometry. An adequate mesh resolution was determined by performing a grid convergence study on a series of systematically refined meshes. An overset mesh of the same resolution was then constructed and was fixed to the body. Drag and pitch results are compared among the two simulations. Free surface elevations around the craft and under the air cushion for simulations with the single and overset meshes are compared. Steady-state simulations using the overset mesh and the single mesh show general similarities in drag, pitch, and free surface elevations.

Numerical simulations of nonlinear axisymmetric flows with a free surface

1987 ◽  
Vol 178 ◽  
pp. 195-219 ◽  
Author(s):  
Douglas G. Dommermuth ◽  
Dick K. P. Yue
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Vertical Cylinder ◽  
Free Surface Flows ◽  
Boundary Integral ◽  
The Body ◽  
Special Treatment ◽  
Computational Domain ◽  
Vortex Sheets

A numerical method is developed for nonlinear three-dimensional but axisymmetric free-surface problems using a mixed Eulerian-Lagrangian scheme under the assumption of potential flow. Taking advantage of axisymmetry, Rankine ring sources are used in a Green's theorem boundary-integral formulation to solve the field equation; and the free surface is then updated in time following Lagrangian points. A special treatment of the free surface and body intersection points is generalized to this case which avoids the difficulties associated with the singularity there. To allow for long-time simulations, the nonlinear computational domain is matched to a transient linear wavefield outside. When the matching boundary is placed at a suitable distance (depending on wave amplitude), numerical simulations can, in principle, be continued indefinitely in time. Based on a simple stability argument, a regriding algorithm similar to that of Fink & Soh (1974) for vortex sheets is generalized to free-surface flows, which removes the instabilities experienced by earlier investigators and eliminates the need for artificial smoothing. The resulting scheme is very robust and stable.For illustration, three computational examples are presented: (i) the growth and collapse of a vapour cavity near the free surface; (ii) the heaving of a floating vertical cylinder starting from rest; and (iii) the heaving of an inverted vertical cone. For the cavity problem, there is excellent agreement with available experiments. For the wave-body interaction calculations, we are able to obtain and analyse steady-state (limit-cycle) results for the force and flow field in the vicinity of the body.

Boundary Layer Measurements at an Internal Free Surface in a Partially Filled Horizontal and Rapidly-Rotating Container

1989 ◽  
Vol 111 (4) ◽  
pp. 457-463 ◽  
Author(s):  
T. J. Singler
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Circular Cylinder ◽  
Steady Flow ◽  
Symmetry Axis ◽  
Azimuthal Velocity ◽  
Free Surfaces ◽  
Horizontal Circular Cylinder ◽  
Good Agreement

Steady flow in a partially filled horizontal circular cylinder rotating rapidly about its symmetry axis is investigated experimentally. Radial boundary layer profiles of the azimuthal velocity in the neighborhood of the internal free surface are reported for a range of inverse Froude numbers and for two types of free surfaces. Results indicate good agreement with an existing theory.

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.

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