Hydrodynamic force of a circular cylinder close to the water surface

2018 ◽  
Vol 171 ◽  
pp. 154-165 ◽  
Author(s):  
Chia-Ren Chu ◽  
Yu-An Lin ◽  
Tso-Ren Wu ◽  
Chung-Yue Wang
Keyword(s):  
Circular Cylinder ◽  
Water Surface ◽  
Hydrodynamic Force

Large Eddy Simulation of a Smooth Circular Cylinder Oscillating Normal to a Uniform Flow

2000 ◽  
Vol 122 (4) ◽  
pp. 694-702 ◽  
Author(s):  
Mustafa Tutar ◽  
Arne E. Holdo̸
Keyword(s):  
Circular Cylinder ◽  
Numerical Evaluation ◽  
Hydrodynamic Force ◽  
Uniform Flow ◽  
Transitional Flow ◽  
Finite Element Code ◽  
Law Of The Wall ◽  
Eddy Simulation ◽  
Steady Current ◽  
Large Eddy

Results of a numerical evaluation of transitional flow around a circular cylinder forced to oscillate in a direction normal to a uniform flow are presented. The cylinder is considered to be a representative of a single riser exposed to a steady current. Numerical simulations were carried out using the LES method in 2-D and 3-D with a near-wall approach that was developed without using a “law of the wall” for a finite element code (FEM). The 3-D simulations were compared with the 2-D results and experimental data in order to assess the relative performance of the 3-D LES simulations. The results show that 3-D LES gives more realistic flow field predictions and can further remove overconservatism in the prediction of hydrodynamic force coefficients. [S0098-2202(00)01103-2]

scholarly journals Hydroelastic effects during the fast lifting of a disc from a water surface

2019 ◽  
Vol 869 ◽  
pp. 726-751 ◽  
Author(s):  
P. Vega-Martínez ◽  
J. Rodríguez-Rodríguez ◽  
T. I. Khabakhpasheva ◽  
A. A. Korobkin
Keyword(s):  
Water Surface ◽  
High Speed ◽  
Hydrodynamic Force ◽  
Early Stage ◽  
The Body ◽  
Plate Motion ◽  
Elastic Behaviour ◽  
Simple Extension ◽  
Wetted Area ◽  
Water Exit

Here we report the results of an experimental study where we measure the hydrodynamic force acting on a plate which is lifted from a water surface, suddenly starting to move upwards with an acceleration much larger than gravity. Our work focuses on the early stage of the plate motion, when the hydrodynamic suction forces due to the liquid inertia are the most relevant ones. Besides the force, we measure as well the acceleration at the centre of the plate and the time evolution of the wetted area. The results of this study show that, at very early stages, the hydrodynamic force can be estimated by a simple extension of the linear exit theory by Korobkin (J. Fluid Mech., vol. 737, 2013, pp. 368–386), which incorporates an added mass to the body dynamics. However, at longer times, the measured acceleration decays even though the applied external force continues to increase. Moreover, high-speed recordings of the disc displacement and the radius of the wetted area reveal that the latter does not change before the disc acceleration reaches its maximum value. We show in this paper that these phenomena are caused by the elastic deflection of the disc during the initial transient stage of water exit. We present a linearised model of water exit that accounts for the elastic behaviour of the lifted body. The results obtained with this new model agree fairly well with the experimental results.

Two-Dimensional Unsteady Viscous Flows

2017 ◽  
Author(s):  
Jian-Jun Shu
Keyword(s):  
Circular Cylinder ◽  
Flow Field ◽  
Hydrodynamic Force ◽  
Viscous Flows ◽  
Reynolds Numbers ◽  
Fundamental Solutions ◽  
Time Dependent ◽  
Two Dimensional ◽  
Low Reynolds Numbers ◽  
Rotational Motions

A number of new closed-form fundamental solutions for the two-dimensional generalized unsteady Oseen and Stokes flows associated with arbitrary time-dependent translational and rotational motions have been developed. As an example of application, the hydrodynamic force acting on a circular cylinder translating in an unsteady flow field at low Reynolds numbers is calculated using the new generalized fundamental solutions.

scholarly journals Incompressible impulsive sloshing

2012 ◽  
Vol 708 ◽  
pp. 279-302 ◽  
Author(s):  
Peder A. Tyvand ◽  
Touvia Miloh
Keyword(s):  
Circular Cylinder ◽  
Time Scale ◽  
Hydrodynamic Force ◽  
Small Time ◽  
Surface Velocity ◽  
Leading Order ◽  
Intermediate Time ◽  
Time Expansion ◽  
Horizontal Cylinders ◽  
Intermediate Time Scale

AbstractThe incompressible impulsive time scale for inviscid liquid sloshing in open rigid containers suddenly put into motion is defined as the intermediate time scale in between the acoustic time scale and the gravitational time scale. Surge and sway boundary-value problems for incompressible impulsive sloshing in some realistic container shapes are solved analytically to the leading order in a small-time expansion. A solution is provided for two types of horizontal cylinders: a triangular cylindrical wedge and a half-filled circular cylinder. The surface velocity and the hydrodynamic force with its corresponding virtual fluid mass are calculated. The cases of constant impulsive velocity and constant impulsive acceleration are linked by transformation equations. Flows with waterline singularities are discussed, being leading-order outer flows in terms of matched asymptotic expansions.

Distribution of gyrotactic micro-organisms in complex three-dimensional flows. Part 1. Horizontal shear flow past a vertical circular cylinder

2018 ◽  
Vol 852 ◽  
pp. 358-397 ◽  
Author(s):  
L. Zeng ◽  
T. J. Pedley
Keyword(s):  
Circular Cylinder ◽  
Shear Flow ◽  
Vortex Shedding ◽  
Water Surface ◽  
Concentration Distribution ◽  
Three Dimensional ◽  
Swimming Velocity ◽  
Horizontal Shear ◽  
Active Particles ◽  
Micro Organisms

As a first step towards understanding the distribution of swimming micro-organisms in flowing shallow water containing vegetation, we formulate a continuum model for dilute suspensions in horizontal shear flow, with a maximum Reynolds number of 100, past a single, rigid, vertical, circular cylinder that extends from a flat horizontal bed and penetrates the free water surface. A numerical platform was developed to solve this problem, in four stages: first, a scheme for computation of the flow field; second, a solver for the Fokker–Planck equation governing the probability distribution of the swimming direction of gyrotactic cells under the combined action of gravity, ambient vorticity and rotational diffusion; third, the construction of a database for the mean swimming velocity and the translational diffusivity tensor as functions of the three vorticity components, using parameters appropriate for the swimming alga, Chlamydomonas nivalis; fourth, a solver for the three-dimensional concentration distribution of the gyrotactic micro-organisms. Upstream of the cylinder, the cells are confined to a vertical strip of width equal to the cylinder diameter, which enables us to visualise mixing in the wake. The flow downstream of the cylinder is divided into three zones: parallel vortex shedding in the top zone near the water surface, oblique vortex shedding in the middle zone and quasi-steady flow in the bottom zone. Secondary (vertical) flow occurs just upstream and downstream of the cylinder. Frequency spectra of the velocity components in the wake of the cylinder show two dominant frequencies of vortex shedding, in the parallel- and oblique-shedding zones respectively, together with a low frequency, equal to the difference between those two frequencies, that corresponds to a beating modulation. The concentration distribution is calculated for both active particles and passive, non-swimming, particles for comparison. The concentration distribution is very similar for both active and passive particles, except near the top surface, where upswimming causes the concentration of active particles to reach values greater than in the upstream strip, and in a thin boundary layer on the downstream surface of the cylinder, where a high concentration of active particles occurs as a result of radial swimming.

Hydrodynamic Force Measurements on a Circular Cylinder Fitted With Peripheral Control Cylinders: Preliminary Results on the Development of VIV Suppressors

2015 ◽  
Author(s):  
Mariana Silva-Ortega ◽  
Gustavo R. S. Assi ◽  
Murilo M. Cicolin
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Vortex Shedding ◽  
Hydrodynamic Force ◽  
Force Measurements ◽  
Number Range ◽  
Preliminary Results ◽  
Reynolds Number Range

Recent achievements in controlling the boundary layer by moving surfaces have been encouraging the development and investigation of passive suppressors of vortex-induced vibration. Within this context, the main purpose of the present work is to evaluate the suppression of vortex shedding of a plain cylinder surrounded by two, four and eight smaller control cylinders. Experiments have been carried out on a fixed circular cylinder to investigate the effect of the control cylinders over drag reduction. Control cylinders with diameter of d/D = 0.06 were tested, where D is the diameter of the main cylinder. The gap between the main cylinder and the control cylinders varied between G/D = 0.05 and 0.15. Experiments with a plain cylinder in the Reynolds number range from 5,000 to 50,000 have been performed to serve as reference. It was found that a cylinder fitted with four control cylinders presented less drag and fluctuating lift than cylinders fitted with two or eight small cylinders.

Hydrodynamic force on a moving circular cylinder submerged in a general fluid flow

1992 ◽  
Vol 438 (1903) ◽  
pp. 331-339 ◽  
Keyword(s):  
Circular Cylinder ◽  
Hydrodynamic Force ◽  
Body Movement ◽  
Offshore Structures ◽  
Inertia Force ◽  
Wave Loading ◽  
Fluid Loading ◽  
Velocity Gradients ◽  
Flow Changes ◽  
Arbitrary Flow

This paper develops an expression for the fluid loading on a circular cylinder due to classical inviscid, irrotational and incompressible flow. The cylinder has an arbitrary rigid body movement, and the fluid, and in the absence of the cylinder, has an arbitrary flow pattern, subject only to the requirement that the length scale over which the flow changes is sufficiently large compared with the dimensions of the cylinder cross-section that only velocities and velocity gradients need be considered. The result is intended to be used as the ‘inertia’ force component of wave loading on the cylindrical members of offshore structures in the conventional Morison’s Equation formulation, and as such it differs significantly from that currently in use.

scholarly journals HYDRODYNAMIC FORCES ON A CIRCULAR CYLINDER DUE TO COMBINED WAVE AND CURRENT LOADING

1984 ◽  
Vol 1 (19) ◽  
pp. 191
Author(s):  
Yuichi Iwagaki ◽  
Toshiyuki Asano
Keyword(s):  
Circular Cylinder ◽  
Lift Force ◽  
Hydrodynamic Force ◽  
Flow Characteristics ◽  
Hydrodynamic Forces ◽  
Transverse Force ◽  
Particle Movement ◽  
Mass Coefficient ◽  
Line Force ◽  
Current Loading

The hydrodynamic force acting on a circular cylinder in a wavecurrent co-existing field and its generating mechanism are discussed. This study focuses on the asymmetries of both the water particle movement and the resultant vortex property with respect to the cylinder, which produce inherent characteristics in the hydrodynamic forces in the wave-current co-existing field. First of all, the vortex property around a circular cylinder in the wave-adverse current co-existing field has been examined by flow visualization tests. It has been found that the vortex property depends on the flow characteristics around the trough phase when the wave-current composite velocity becomes maximum and can be represented with a newly proposed K.C. number for the co-existing field. Secondly, the characteristics of the in-line force has been made clear by evaluating the drag coefficient and the mass coefficient in the expanded Morison's equation for the co-existing field. These coefficients can be well arranged by (/CC. )•$, which is one of the newly proposed K.C. numbers, and their characteristics coincide with the existing results in the wave only field. The in-line hydrodynamic force in the co-existing field can be explained sufficiently by considering the vortex property in the same manner as clarified in the wave only field. Thirdly, the characteristics of the transverse force (lift force) are discussed in connection with the vortex properties. It has also been found that the fluctuating frequency of the lift force is synchronized with the loading wave frequency.

Free-surface flow due to impulsive motion of a submerged circular cylinder

1995 ◽  
Vol 286 ◽  
pp. 67-101 ◽  
Author(s):  
Peder A. Tyvand ◽  
Touvia Miloh
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Hydrodynamic Force ◽  
Free Surface Flow ◽  
Small Time ◽  
Surface Flow ◽  
Constant Acceleration ◽  
Impulsive Motion ◽  
Gravitational Effects ◽  
Bipolar Coordinates

The impulsively starting motion of a circular cylinder submerged horizontally below a free surface is studied analytically using a small-time expansion. The series expansion is taken as far as necessary to include the leading gravitational effects for two cases: constant velocity and constant acceleration, both commencing from rest. The hydrodynamic force on the cylinder and the surface elevation are calculated and expressed in terms of bipolar coordinates. Comparisons are also made with earlier theoretical and experimental work. The theory is valid for arbitrary value of submergence depth to cylinder radius.

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