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.

Influence of wing kinematics on aerodynamic performance in hovering insect flight

2007 ◽  
Vol 594 ◽  
pp. 341-368 ◽  
Author(s):  
FRANK M. BOS ◽  
D. LENTINK ◽  
B. W. VAN OUDHEUSDEN ◽  
H. BIJL
Keyword(s):  
Insect Flight ◽  
Fruit Fly ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Insect Wing ◽  
Wing Kinematics ◽  
Drag Forces ◽  
Kinematic Models ◽  
Characteristic Features ◽  
Lift And Drag

The influence of different wing kinematic models on the aerodynamic performance of a hovering insect is investigated by means of two-dimensional time-dependent Navier–Stokes simulations. For this, simplified models are compared with averaged representations of the hovering fruit fly wing kinematics. With increasing complexity, a harmonic model, a Robofly model and two more-realistic fruit fly models are considered, all dynamically scaled at Re = 110. To facilitate the comparison, the parameters of the models were selected such that their mean quasi-steady lift coefficients were matched. Details of the vortex dynamics, as well as the resulting lift and drag forces, were studied.The simulation results reveal that the fruit fly wing kinematics result in forces that differ significantly from those resulting from the simplified wing kinematic models. In addition, light is shed on the effect of different characteristic features of the insect wing motion. The angle of attack variation used by fruit flies increases aerodynamic performance, whereas the deviation is probably used for levelling the forces over the cycle.

Prediction of drag and lift forces of a high-speed vessel at full scale by CFD-based GEOSIM method

2022 ◽  
pp. 147509022110707
Author(s):  
Ugur Can ◽  
Sakir Bal
Keyword(s):  
High Speed ◽  
Full Scale ◽  
Navier Stokes ◽  
Drag Forces ◽  
Fluid Body ◽  
Unsteady Rans ◽  
Lift Forces ◽  
Drag And Lift ◽  
Lift And Drag ◽  
Model Family

In this study, it was aimed to obtain an accurate extrapolation method to compute lift and drag forces of high-speed vessels at full-scale by using CFD (Computational Fluid Dynamics) based GEOSIM (GEOmetrically SIMilar) method which is valid for both fully planing and semi-planing regimes. Athena R/V 5365 bare hull form with a skeg which is a semi-displacement type of high-speed vessel was selected with a model family for hydrodynamic analyses under captive and free to sinkage/trim conditions. Total drag and lift forces have been computed for a generated GEOSIM family of this form at three different model scales and full-scale for Fr = 0.8 by an unsteady RANS (Reynolds Averaged Navier–Stokes) solver. k–ε turbulence model was used to simulate the turbulent flow around the hulls, and both DFBI (Dynamic Fluid Body Interaction) and overset mesh technique were carried out to model the heave and pitch motions under free to sinkage/trim condition. The computational results of the model family were used to get “drag-lift ratio curve” for Athena hull at a fixed Fr number and so the corresponding results at full scale were predicted by extrapolating those of model scales in the form of a non-dimensional ratios of drag-lift forces. Then the extrapolated full-scale results calculated by modified GEOSIM method were compared with those of full-scale CFD and obtained by Froude extrapolation technique. The modified GEOSIM method has been found to be successful to compute the main forces (lift and drag) acting on high-speed vessels as a single coefficient at full scale. The method also works accurately both under fully and semi-planing conditions.

Lift And Drag Forces On A Submerged Circular Cylinder

1971 ◽  
Author(s):  
J.F. Beattie ◽  
L.P. Brown ◽  
B.F. Webb
Keyword(s):  
Circular Cylinder ◽  
Drag Forces ◽  
Lift And Drag

Model Test Study on Vortex-Induced Motions of a Floating Cylinder

2009 ◽  
Author(s):  
Ying Wang ◽  
Jianmin Yang ◽  
Tao Peng ◽  
Xin Li
Keyword(s):  
Circular Cylinder ◽  
Scale Model ◽  
Visualization System ◽  
Forced Motion ◽  
Drag Forces ◽  
Fluid Field ◽  
Helical Strakes ◽  
Induced Motion ◽  
Motion Characteristics ◽  
Lift And Drag

Vortex-Induced Motions (VIM) under current flow is an important issue for surface piercing cylinders, such as Spar platforms and floating buoys, since it affects the motion performance of these structures greatly. In recent years this phenomenon attracts much attention and many researchers have been making efforts to deal with this problem. VIM is such a complicated phenomenon that more fundamental studies are needed to understand the essence behind VIM. This paper mainly concentrates on a circular cylinder, aiming to eliminate outside influences and reveal the inherent characteristic of vortex-induced motion mechanism. A circular cylinder with an aspect ratio of 1:2.4, which could be considered as a scale model for the hard tank of a typical Truss Spar, is studied by experimental method to investigate the surrounding fluid field, the excitation forces and Vortex-Induced Motion characteristics under various governing parameters, such as the current velocity and direction, the mooring stiffness and distribution, the use and efficiency of helical strakes, and so on. By using a simple flow visualization system, the unsteady flow passing the circular cylinder and the vortices in the wake are captured and recorded. The cylinder is tested respectively under fixed, forced-motion and elastically moored conditions. The fluid field, the vortex structures, and the lift and drag forces under fixed and forced-motion conditions are measured, the VIM performance of the cylinder with two different mooring distributions are studied, and strake efficiency is studied considering current directionality and strake height influence.

The Interaction of Porous Metal Coating With the Near Wake of Bluff Body

2012 ◽  
Author(s):  
Hanru Liu ◽  
Jinjia Wei ◽  
Zhiguo Qu
Keyword(s):  
Circular Cylinder ◽  
Bluff Body ◽  
Porous Metal ◽  
Metal Coating ◽  
Wake Flow ◽  
Navier Stokes ◽  
Aerodynamic Forces ◽  
Near Wake ◽  
Drag Forces ◽  
Flow Induced Noise

The flow around a circular cylinder with porous metal coating (PMC) is numerically investigated based on an approach of unsteady Reynolds Averaged Navier-Stokes (URANS) at subcritical Reynolds number. The model validation is carried out through comparison with some available experimental results in the literatures. It is found that the simulated results in the present work coincide well with the experimental data. The interaction of PMC with the near wake of circular cylinder such as streamline, vorticity and shear stress are studied in detail. The result reveals that PMC has capability of manipulating the wake flow so that the near wake of PMC cylinder is substantially different from that of smooth one. In addition, the fluctuations of aerodynamic forces are mitigated effectively. Varying the thickness of porous metal coating causes various velocity distributions and aerodynamic performance of bluff body. When the thickness is appropriate, the drag forces can be reduced to a certain extent. It is expected that the modification of flow characteristic and aerodynamic forces also produces the suppression of flow-induced noise generated by bluff body. These studies on wake flow and analysis of its relationship to flow-induced noise will be useful to understand the mechanism of controlling bluff body flow-induced noise by using PMC and to optimize the PMC for controlling flow and flow-induced noise.

Experimental Force Coefficients for a Parametric Series of Spinnakers

2003 ◽  
Author(s):  
William C. Lasher ◽  
James R. Sonnenmeier ◽  
David R. Forsman ◽  
Cheng Zhang ◽  
Kenton White
Keyword(s):  
Aspect Ratio ◽  
Thrust Force ◽  
Statistical Design ◽  
Navier Stokes ◽  
Statistical Design Of Experiments ◽  
Force Coefficient ◽  
Force Coefficients ◽  
Drag Forces ◽  
Parametric Series ◽  
Lift And Drag

A parametric series of eight spinnaker models was built and tested in a wind tunnel according to the theory of statistical Design of Experiments. In these models, three sail shape parameters were varied - cross section camber ratio, sail aspect ratio, and sweep. Lift and drag forces were measured for a range of angles of attack, and the thrust force coefficient was determined as a function of apparent wind angle for each of the eight sails. It was found that flat spinnakers are faster than full spinnakers and that spinnakers with low sweep (more vertical) are faster than spinnakers with high sweep. This is consistent with general sailing practice, which maximizes projected sail area by pulling the pole back and down. The influence of aspect ratio on drag coefficient was small and within experimental error. A description of the sail shapes and corresponding force coefficients is presented for future validation of Reynolds Averaged Navier-Stokes simulations.

scholarly journals Prediction of Turbulent Flow Around a Square Cylinder With Rounded Corners

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
S. S. Dai ◽  
B. A. Younis ◽  
H. Y. Zhang
Keyword(s):  
Turbulent Flow ◽  
Vortex Shedding ◽  
Turbulence Closure ◽  
Navier Stokes ◽  
Square Cylinder ◽  
Mean Flow ◽  
Drag Forces ◽  
Turbulence Closures ◽  
High Reynolds ◽  
Lift And Drag

Predictions are reported of the two-dimensional turbulent flow around a square cylinder with rounded corners at high Reynolds numbers. The effects of rounded corners have proved difficult to predict with conventional turbulence closures, and hence, the adoption in this study of a two-equation closure that has been specifically adapted to account for the interactions between the organized mean-flow motions due to vortex shedding and the random motions due to turbulence. The computations were performed using openfoam and were validated against the data from flows past cylinders with sharp corners. For the case of rounded corners, only the modified turbulence closure succeeded in capturing the consequences of the delayed flow separation manifested mainly in the reduction of the magnitude of the lift and drag forces relative to the sharp-edged case. These and other results presented here argue in favor of the use of the computationally more efficient unsteady Reynolds-averaged Navier-Stokes approach to this important class of flows provided that the effects of vortex shedding are properly accounted for in the turbulence closure.

The lift and drag forces on a circular cylinder in a flowing fluid

1964 ◽  
Vol 277 (1368) ◽  
pp. 32-50 ◽  
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Drag Force ◽  
Central Axis ◽  
Flowing Fluid ◽  
Drag Forces ◽  
Lift And Drag

Apparatus is described for measuring directly fluctuating lift and drag forces and steady mean drag force. These forces are exerted upon a cylinder placed so that its central axis is perpendicular to the direction of flow of water in a channel. Results are given for the stationary cylinder for the range of Reynolds number 3600 to 11 000.

Numerical Simulation of Water-Entry and Sedimentation of an Elliptic Cylinder Using Smoothed-Particle Hydrodynamics Method

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Roozbeh Saghatchi ◽  
Jafar Ghazanfarian ◽  
Mofid Gorji-Bandpy
Keyword(s):  
Free Surface ◽  
Smoothed Particle Hydrodynamics ◽  
Elliptic Cylinder ◽  
Water Entry ◽  
The Body ◽  
Numerical Code ◽  
Sph Method ◽  
Navier Stokes Equation ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

This paper studies the two-dimensional water-entry and sedimentation of an elliptic cylinder using the subparticle scale (SPS) turbulence model of a Lagrangian particle-based smoothed-particle hydrodynamics (SPH) method. The motion of the body is driven by the hydrodynamic forces and the gravity. The present study shows the ability of the SPH method for the simulation of free-surface-involving and multiphase flow problems. The full Navier–Stokes equation, along with the continuity equation, have been solved as the governing equations of the problem. The accuracy of the numerical code is verified using the case of the water-entry and exit of a circular cylinder. The numerical simulations of the water-entry and sedimentation of the vertical and horizontal elliptic cylinder with the diameter ratio of 0.75 are performed at the Froude numbers of 0, 2, 5, and 8, and the specific gravities of 0.5, 0.75, 1, 1.5, 1.75, 2, and 2.5. The effect of the governing parameters and vortex shedding behind the elliptic cylinder on the trajectory curves, velocity components within the flow field, rotation angle, the velocity of ellipse, and the deformation of free-surface have been investigated in detail.

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