scholarly journals Experimental validation of lift and drag forces on an asymmetrical hydrofoil for seafloor anchoring applications

2019 ◽  
Vol 9 ◽  
pp. 175931311881197
Author(s):  
Gerry Byrne ◽  
Tim Persoons ◽  
William Kingston
Keyword(s):  
Drag Force ◽  
Force Measurement ◽  
Tidal Flow ◽  
Tidal Energy ◽  
The Sun ◽  
Tidal Power ◽  
Renewable Power ◽  
Drag Forces ◽  
Numerical Predictions ◽  
Lift And Drag

Tidal power can be described as harnessing the kinetic energy of the in and out flows known as tides created by the changing gravitational pull of the moon and the sun on the oceans of the world. As the relative positions of the sun and moon can be accurately predicted, so can the resultant tidal movements, making tidal energy such a valuable resource and an attractive option for renewable power generation. However, the high costs and difficulties associated with the deployment of underwater turbines, which includes anchoring, are prohibitive factors in the widespread utilisation of tidal power technology. Existing turbine fixation methods are primarily based on the use of large gravity anchors or monopole structures to secure the turbine to the seabed. In an effort to reduce size, environmental impact on the seafloor and installation cost, a hydrofoil-based anchor could be considered. The objective of this study is to experimentally test the lift and drag force behaviour of a finite-span hydrofoil with endplates, whose profile was selected based on simplified two-dimensional (2D) numerical simulations using the vortex panel method. A customised lift and drag force measurement system for this prototype hydrofoil was designed, fabricated and calibrated, and subsequently installed and tested in the Dutch Tidal Testing Centre (TTC) in Den Oever, the Netherlands. A series of tests with force and flow velocity measurements are described for different angles-of-attack under realistic tidal flow conditions. Results for the lift and drag coefficients as a function of angle-of-attack are compared to numerical simulation data and revealed that the real-world lift force is predicted well, whereas the drag force is underpredicted by the numerical predictions. These findings provide useful information for the design of anchoring systems based of hydrofoil profiles.

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.

Fluid forces on a body in shear-flow; experimental use of ‘stationary flow'

1974 ◽  
Vol 340 (1621) ◽  
pp. 147-171 ◽  
Keyword(s):  
Shear Flow ◽  
Lift Force ◽  
Force Measurement ◽  
Fluid Velocity ◽  
Stationary Flow ◽  
The Body ◽  
Fluid Forces ◽  
Drag Forces ◽  
Lift And Drag ◽  
Repulsive Forces

The lift and drag forces have been measured on a sphere and a transverse cylinder immersed in an open liquid shear-flow and situated close to the lower, frictional, boundary (the bed). Two conditions were investigated: ( a ) that of zero drag, when the body was drifting with the flow, and ( b ) that when it was held against the flow. In condition ( a ) the body could be either allowed to rotate about a transverse axis subject to unavoidable pivot friction, or prevented from rotating. Marked difference was found in the magnitude of the lift force according to the applied resistance to rotation. The lift force was a maximum when rotation was prevented and small or undetectable when free rotation was allowed. In the conditions ( a ) and ( b ) the lift force decreased with increasing clearance between body and boundary, to zero when the clearance exceeded approximately one body diameter. In condition ( b ) lift, i. e. normally repulsive, forces of approximately equal magnitudes to those below were exerted as the body approached the upper free liquid surface. In the drifting condition ( a ) the considerable difficulties of observation and force measurement when a body is moving with the flow were removed by the use of a backward-moving bed boundary. By thus superimposing a reverse velocity on the whole system, the mean fluid velocity at any desired distance from the boundary can be made zero relative to the observer without appreciably affecting the internal dynamics of the flow. This device also permitted the repetition of the measurements made by using liquids of greater viscosity than water available in limited quantities. The results are interpreted with an explanation in mind of certain aspects of the motions of unsuspended solids in saltation over a stream bed.

Lift and Drag Forces With Respect to Azimuth Position of a Darrieus Wind Turbine

2018 ◽  
Author(s):  
Sajid Ali ◽  
Sang-Moon Lee ◽  
Choon-Man Jang
Keyword(s):  
Wind Turbine ◽  
Drag Force ◽  
Lift Force ◽  
Tangential Force ◽  
Navier Stokes ◽  
Drag Forces ◽  
Force Variation ◽  
Lift And Drag ◽  
Naca 0015 ◽  
The Impact

Tangential force is the most important parameter for driving the blade of a straight bladed H-Darrieus wind turbine forward. The direction of this force is very critical as it may move the blade forward (positive force) or it can also oppose the rotation (negative force). The direction of tangential force depends upon the distribution of two fundamental aerodynamic forces around the wind turbine blade i.e. Lift and drag. Current study aims to understand the impact of lift and drag forces on the tangential force variation with respect to (w.r.t) azimuth position. Commercial CFD software SC/tetra was employed in order to solve the unsteady Reynold-averaged Navier stokes (URANS) equations around the blades. Results show that very small portion (maximum 20% during rotation) of the drag force is actually converted into useful tangential force whereas rest of the drag force is converted into either normal force or negative tangential force (waste of energy). On the other hand, out of all the generated lift force, 70–90 percent is seemed to be beneficial for moving the blade forward and rest of the lift force also tries to oppose the motion (almost 15%). Overall, it was found that only 50–60 percent of the resultant force (lift + drag) acting on the blade, is actually useful to move the blade forward. The study was conducted at seven different tip speed ratios (TSRs) i.e. 1, 2, 2.28, 3, 3.5, 4 and 5 with NACA 0015 airfoil. Relatively higher fluctuations were observed in the distribution of forces at low values of TSRs (1 and 2) as compared to high values of TSRs (4 and 5). The results presented here are only limited to NACA 0015 whereas same methodology can be adopted for other blade profiles in future as well.

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

1964 ◽  
Vol 277 (1368) ◽  
pp. 51-75 ◽  
Keyword(s):  
Circular Cylinder ◽  
Drag Force ◽  
Flowing Fluid ◽  
Drag Forces ◽  
Lift And Drag

A circular cylinder was placed in a flowing fluid with its axis across the stream. The fluctuating lift and drag forces, and the steady drag force were measured. The results for the stationary cylinder were given in a previous paper (Bishop & Hassan 1964). Here, the results are described and summarized for a cylinder that is made to oscillate transversely in a direction perpendicular to the stream.

scholarly journals Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 14
Author(s):  
Gianluca Zitti ◽  
Nico Novelli ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Offshore Structures ◽  
Fish Farm ◽  
Maximum Displacement ◽  
Drag Forces ◽  
Real Size ◽  
Lift And Drag ◽  
Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

Harmonic Analysis on Low Quality Tidal Data

2014 ◽  
Author(s):  
Joost den Haan
Keyword(s):  
Harmonic Analysis ◽  
Three Dimensional ◽  
Measurement Data ◽  
Tidal Energy ◽  
Energy Yield ◽  
Profile Measurement ◽  
Current Profile ◽  
Tidal Power ◽  
Data Set ◽  
Tidal Forcing

The aim of the study is to devise a method to conservatively predict a tidal power generation based on relatively short current profile measurement data sets. Harmonic analysis on a low quality tidal current profile measurement data set only allowed for the reliable estimation of a limited number of constituents leading to a poor prediction of tidal energy yield. Two novel, but very different approaches were taken: firstly a quasi response function is formulated which combines the currents profiles into a single current. Secondly, a three dimensional vectorial tidal forcing model was developed aiming to support the harmonic analysis with upfront knowledge of the actual constituents. The response based approach allowed for a reasonable prediction. The vectorial tidal forcing model proved to be a viable start for a full featuring numerical model; even in its initial simplified form it could provide more insight than the conventional tidal potential models.

Estimation and Feasibility of Generating Power Using Tidal Energy

2020 ◽  
Author(s):  
Satya Prasad Paruchuru ◽  
Siva Kalyani Koneti ◽  
Deepthi Jammula ◽  
Jashwitha Nuthalapati
Keyword(s):  
Renewable Energy ◽  
Power Plants ◽  
Space Exploration ◽  
Tidal Energy ◽  
Regions Of Interest ◽  
Working Fluid ◽  
Tidal Power ◽  
The Cost

Abstract Capturing the tidal energy is one of the ways of tapping natural and renewable energy which do not involve the cost of working fluid/ fuel. The present work focuses on some of the feasibility aspects of setting up of major tidal power plants along the seacoast. Besides, the present study synergizes on methods of estimating the power-producing capacities in regions along the seacoast. Estimation of power-producing capacities, calendar month-wise, and lunar month-wise gave handy information. Also, the estimation of power-producing capacities of different regions along a location gave clarity on the probable regions of interest for producing power simultaneously. A comparison of the estimates with the details of the literature authenticated the study. A discussion of producing more tidal power in specific locations gave insights into the aspects that may have been ignored in the literature. Geographic restrictions along the local seacoast like identifying the security-sensitive regions rationalized the estimating procedures. The paper includes a discussion of various factors that address the feasibility concerns. The study supposedly helps space exploration too.

Lift and Drag Force Calculations and Magnet Design for the Magneplane Model

1973 ◽  
Author(s):  
C. H. Tang ◽  
W. J. Harrold ◽  
Hugh C. Wolfe ◽  
C. D. Graham ◽  
J. J. Rhyne
Keyword(s):  
Drag Force ◽  
Magnet Design ◽  
Lift And Drag

Drag Forces on, and Deformation of, Closed Flexible Bags

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Pål Lader ◽  
David W. Fredriksson ◽  
Zsolt Volent ◽  
Jud DeCew ◽  
Trond Rosten ◽  
...  
Keyword(s):  
Drag Force ◽  
Hydrodynamic Forces ◽  
Towing Tank ◽  
Drag Forces ◽  
Uniform Current ◽  
Salmon Production

The use of closed flexible bags is among the suggestions considered as a potential way to expand the salmon production in Norway. Few ocean structures exist with large, heavily compliant submerged components, and there is presently limited existing knowledge about how aquaculture systems with flexible closed cages will respond to external sea loads. The flexibility and deformation of the bag are coupled to the hydrodynamic forces, and the forces and deformation will be dependent on the filling level of the bag. In order to get a better understanding of the drag forces on, and deformation of, such bags, experiments were conducted with a series of closed flexible bags. The bags were towed in a towing tank in order to simulate uniform current. Four different geometries were investigated, cylindrical, cubical, conical, and pyramidal, and the filling levels were varied between 70% and 120%. The main findings from the experiments were that the drag force was highly dependent on the filling level, and that the drag force increases with decreasing filling level. Comparing the drag force on a deflated bag with an inflated one showed an increase of up to 2.5 times.

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