Experimental Study of Drag and Lift Forces on Prototype Scale Models of Large Wood

2005 ◽  
Author(s):  
Carlos V. Alonso ◽  
F. Douglas Shields, Jr. ◽  
Darrel M. Temple
Keyword(s):  
Experimental Study ◽  
Large Wood ◽  
Scale Models ◽  
Lift Forces ◽  
Drag And Lift

Experimental study on the effect of turning angle on drag and lift forces for various cut angles on spheres

2007 ◽  
Vol 221 (3) ◽  
pp. 303-306 ◽  
Author(s):  
A Pudjanarsa
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Experimental Results ◽  
Force Balance ◽  
Turning Angle ◽  
Minimum Value ◽  
Lift Forces ◽  
Drag And Lift

An experimental study on the effect of turning angle on drag and lift forces for various cut angles on spheres is performed. Five different cut angles on different spheres were applied including: 30°, 45°, 53°, 55°, and 75°. Drag and lift forces were measured using a wind tunnel force balance and the wind speed was set so that a corresponding Reynolds number of 5.3 × 104 was achieved. Wind turning angle was varied from 0° to 60°. Experimental results show that, in general, drag and lift forces increase as the turning angle increases. At 0° turning angle, Cd minimum is attained at a cut angle of 53° and is ∼32 per cent less than Cd without cut angle. The maximum C1 is attained at a cut angle of 75° for a turning angle of 50° for approximately 0.68. This value of C1,max is about 855 per cent higher than that of the same turning angle for a cut angle of 30°. At a particular turning angle, lift attains a maximum and beyond that turning angle-drag and lift forces decrease. Minimum value of drag and lift forces reached at the cut angle of 30° for all turning angles.

Numerical Investigation of the Drag and Lift Forces Acting on Impenetrable Rotating Spherical Nano-Particle

2008 ◽  
Author(s):  
M. R. Meigounpoory ◽  
A. Rahi ◽  
A. Mirbozorgi
Keyword(s):  
Lift Coefficient ◽  
Three Dimensional ◽  
Slip Boundary Condition ◽  
Slip Condition ◽  
Nano Particle ◽  
Slip Coefficient ◽  
Slip Boundary ◽  
Lift Forces ◽  
Drag And Lift ◽  
Drag And Lift Coefficient

The drag and lift forces acting on a rotating impenetrable spherical suspended nano-particle in a homogeneous uniform flow are numerically studied by means of a three-dimensional numerical simulation with slip boundary condition. The effects of both the slip coefficient and rotational speed of the nanosphere on the drag and lift forces are investigated for Reynolds numbers in the range of 0.1 < Re < 100. Increase of rotation increases the drag and lift force exerted by flow at the surface of nano-sphere. By increasing slip coefficient the values of drag and lift coefficients decreases. At full slip condition, rotation of the nano-sphere has not significant effects on the drag and lift coefficient values moreover the lift coefficient of flow around the rotating spherical particle will be vanished. Present numerical results at no-slip condition are in good agreements with certain results of flow around of rotating sphere.

Drag and Lift Forces Acting on a Sphere in Shear Flow of Power-Law Fluid

2018 ◽  
Vol 27 (4) ◽  
pp. 474-488 ◽  
Author(s):  
A. A. Gavrilov ◽  
K. A. Finnikov ◽  
Ya. S. Ignatenko ◽  
O. B. Bocharov ◽  
R. May
Keyword(s):  
Shear Flow ◽  
Power Law ◽  
Power Law Fluid ◽  
Lift Forces ◽  
Drag And Lift

scholarly journals A Ghost-Cell Immersed Boundary Method for Wave–Structure Interaction Using a Two-Phase Flow Model

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3346
Author(s):  
Yuan-Shiang Tsai ◽  
Der-Chang Lo
Keyword(s):  
Immersed Boundary Method ◽  
Flow Model ◽  
Two Phase Flow ◽  
Immersed Boundary ◽  
Phase Flow ◽  
Ghost Cell ◽  
Two Phase ◽  
Boundary Method ◽  
Lift Forces ◽  
Drag And Lift

The air-water two-phase flow model is developed to study the transformation of monochromatic waves passing over the submerged structure. The level set method is employed to describe the motion of the interface while the effect of the immersed object on the fluid is resolved using the ghost-cell immersed boundary method. The computational domain integrated with the air-water and fluid-solid phases allows the use of uniform Cartesian grids. The model simulates the wave generation, wave decomposition over a submerged trapezoidal breakwater, and the formation of the vortices as well as the drag and lift forces caused by the surface waves over three different configurations of the submerged structures. The numerical results show the capability of the present model to accurately track the deformation of the free surface. In addition, the variation of the drag and lift forces depend on the wavelength and wave induced vortices around the submerged object. Hence, the study observes that the triangular structure experiences the relatively small wave force.

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.

On the Axial-Flexural-Torsional Coupling of Underwater Slender Cylinders

2012 ◽  
Author(s):  
Waldir T. Pinto ◽  
Carlos A. Levi
Keyword(s):  
Large Strains ◽  
Element Formulation ◽  
Algebraic Equations ◽  
Three Dimensional Model ◽  
Cylindrical Structures ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Torsional Coupling ◽  
Lift Forces ◽  
Drag And Lift

This paper presents a numerical model for the simulation of the axial-flexural-torsional coupling of undewater cylindrical structures. Cylindrical structures are largely utilized in the marine environment in a wide range of applications as in risers, marine cables, flexible pipes, mooring systems and so on. They may exhibit complex axial-flexural-torsional coupling, which makes the structural analysis highly nonlinear. In addition, the fluid-structure interaction may include flow induced vibrations, frequency lock-in and internal flow effects. The proposed three-dimensional model assumes that the structure aspect ratio is very high, its cross section is circular, the cable is elastic and may experience large displacements and large strains, as long as the elastic regime holds. The steady state load on the cylinder consists of the self-weight and buoyancy, drag and lift forces, in addition to a distributed residual twist along the cylinder. The drag and lift forces are evaluated by Morison type formulation. The governing differential equations are derived from first principles, assuming Newtonian mechanics. Then, they are solved numerically by a finite element formulation based on nonlinear space frame elements. The resulting set of algebraic equations is solved by a minimization technique that uses the Newton-Raphson algorithm. Results show the ability of the model to predict the static configuration of equilibrium of the cylinder and to capture the coupling between axial, flexural and torsional responses of the cylinder.

REVIEW—Review of Flow Interference Between Two Circular Cylinders in Various Arrangements

1977 ◽  
Vol 99 (4) ◽  
pp. 618-633 ◽  
Author(s):  
M. M. Zdravkovich
Keyword(s):  
Flow Pattern ◽  
Drag Force ◽  
Lift Force ◽  
Flow Direction ◽  
Critical Survey ◽  
Tandem Arrangement ◽  
Critical Spacing ◽  
Gap Flow ◽  
Lift Forces ◽  
Drag And Lift

There are infinite numbers of possible arrangements of two parallel cylinders positioned at right angles to the approaching flow direction. Of the infinite arrangements, two distinct groups may be identified: in one group, the cylinders are in a tandem arrangement, one behind the other at any longitudinal spacing; and in the second group, the cylinders face the flow side by side at any transverse spacing. All other combinations of longitudinal and transverse spacings represent staggered arrangements. The tandem arrangement will be treated first. A critical survey of previous research revealed some “odd” features which had been observed and overlooked by various authors. The discontinuity of vortex shedding implies that a similar discontinuity should be expected for the drag force on both cylinders. The measurements of the front (gap) pressures of the downstream cylinder and the base pressures of both cylinders at various spacings reveal a discontinuous “jump” at some critical spacing. The discontinuity is caused by the abrupt change from one stable flow pattern to another at the critical spacing. A new interpretation is given for the existing data on the drag force for both cylinders. The effects of Reynolds number and surface roughness are treated in some detail. Following this, two cylinders arranged side by side to the approaching flow are considered. All the available data on measured forces are compiled together with additional measurements in the range of intermittent changes of drag and lift forces. The bistable nature of the asymmetric flow pattern around each cylinder produces two alternative values of the drag force coupled with two alternative values of the lift force. The introduction of the interference force coefficient exposes the physical origin of two different forces experienced by the cylinders when arranged side by side. Finally, the least reported arrangement of two staggered cylinders is reviewed. The various arrangements are grouped into classes according to the sign of the lift force, or whether the drag force is greater or less than that for a single cylinder. The measurements of drag and lift forces for various arrangements reveal two different regimes for the lift force. In one regime, the lift force directed toward the wake of the upstream cylinder is due to the entrainment of the flow into the fully developed wake of the upstream cylinder. The lift force in this regime reaches a maximum value when the downstream cylinder is near to the upstream wake boundary. In the second regime, at very small spacings, the lift force becomes very large due to an intense gap flow which displaces the wake of the upstream cylinder. The maximum lift force occurs with the downstream cylinder near to the horizontal axis of the upstream cylinder. A discontinuity in the lift force for some staggered arrangements is found and attributed to the bistable nature of the gap flow.

Effect of explosion source location on tunnel damage

2020 ◽  
Vol 11 (4) ◽  
pp. 448-467
Author(s):  
Petr Prochazka ◽  
Dagmar Jandeková
Keyword(s):  
Shock Wave ◽  
Experimental Study ◽  
Shock Waves ◽  
Longitudinal Axis ◽  
Source Location ◽  
Tunnel Lining ◽  
Scale Models

The experimental study, the results of which are presented in this article, focuses on the shock wave behavior in scale models of tunnel structures and their consequences on the damage of tubes simulating tunnel lining. The source of the explosion is located either on the longitudinal axis of the tunnel or it is located near the bottom of the tunnel. The second case is more akin to reality. This article analyzes the consequences of the location of explosion sources and the influence of their brisance. In order to compare the effects of explosions on the tunnel lining, the effect of the charge deposited on the axis of the tunnel is investigated on a 0.5-m-diameter tube, while the effect of the charge deposited outside the tunnel axis is monitored on a 1-m-diameter tube. Thus, the magnitudes of the brisance may be comparable for both cases. The characteristics of the shock waves are described. The mass of the charges is graded so as not to allow a total collapse of the structure, but to manifest its damage.

Numerical study of obstacle geometry effect on the vortex shedding suppression and aerodynamic characteristics

2019 ◽  
Vol 30 (2) ◽  
pp. 469-495 ◽  
Author(s):  
Salwa Fezai ◽  
Nader Ben-Cheikh ◽  
Brahim Ben-Beya ◽  
Taieb Lili
Keyword(s):  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Time Derivative ◽  
Content Type ◽  
Rectangular Shape ◽  
Lift Forces ◽  
Drag And Lift ◽  
Obstacle Geometry ◽  
Unsteady Regimes

Purpose Two-dimensional incompressible fluid flows around a rectangular shape placed over a larger rectangular shape at low Reynolds numbers (Re) have been numerically analyzed in the present work. The vortex shedding is investigated at different arrangements of the two shapes allowing the investigation of three possible configurations. The calculations are carried out for several values of Re ranging from 1 to 200. The effect of the obstacle geometry on the vortex shedding is analyzed for crawling, steady and unsteady regimes. The analysis of the flow evolution shows that with increasing Re beyond a certain critical value, the flow becomes unstable and undergoes a bifurcation. This paper aims to observe that the transition of the unsteady regime is performed by a Hopf bifurcation. The critical Re beyond which the flow becomes unsteady is determined for each configuration. A special attention is paid to compute the drag and lift forces acting on the rectangular shapes, which allowed determining; the best configuration in terms of both drag and lift. The unsteady periodic wake is characterized by the Strouhal number, which varies with the Re and the obstacle geometry. Hence, the values of vortex shedding frequencies are calculated in this work. Design/methodology/approach The dimensionless Navier–Stokes equations were numerically solved using the following numerical technique based on the finite volume method. The temporal discretization of the time derivative is performed by an Euler backward second-order implicit scheme. Non-linear terms are evaluated explicitly; while, viscous terms are treated implicitly. The strong velocity–pressure coupling present in the continuity and the momentum equations are handled by implementing the projection method. Findings The present paper aims to numerically study the effect of the obstacle geometry on the vortex shedding and on the drag and lift forces to analyze the flow structure around three configurations at crawling, steady and unsteady regimes. Originality/value A special attention is paid to compute the drag and lift forces acting on the rectangular shapes, which allowed determining; the best shapes configuration in terms of both drag and lift.

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