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

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.

Influence of Wall Proximity on the Lift and Drag of a Particle in an Oscillatory Flow

Journal of Fluids Engineering ◽

10.1115/1.1905647 ◽

2004 ◽

Vol 127 (3) ◽

pp. 583-594 ◽

Cited By ~ 7

Author(s):

Paul F. Fischer ◽

Gary K. Leaf ◽

Juan M. Restrepo

Keyword(s):

Lift Force ◽

Degrees Of Freedom ◽

Oscillatory Flow ◽

Numerical Solutions ◽

Stokes Equations ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Drag Forces ◽

Lift And Drag ◽

Two Parameters

We report on the lift and drag forces on a stationary sphere subjected to a wall-bounded oscillatory flow. We show how these forces depend on two parameters, namely, the distance between the particle and the bounding wall, and on the frequency of the oscillatory flow. The forces were obtained from numerical solutions of the unsteady incompressible Navier–Stokes equations. For the range of parameters considered, a spectral analysis found that the forces depended on a small number of degrees of freedom. The drag force manifested little change in character as the parameters varied. On the other hand, the lift force varied significantly: We found that the lift force can have a positive as well as a negative time-averaged value, with an intermediate range of external forcing periods in which enhanced positive lift is possible. Furthermore, we determined that this force exhibits a viscous-dominated and a pressure-dominated range of parameters.

Influence of wing kinematics on aerodynamic performance in hovering insect flight

Journal of Fluid Mechanics ◽

10.1017/s0022112007009172 ◽

2007 ◽

Vol 594 ◽

pp. 341-368 ◽

Cited By ~ 95

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 ◽

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.

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

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

10.1177/14750902211070743 ◽

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.

Aerodynamic Analysis on Wind Turbine Aerofoil

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i3.27.17997 ◽

2018 ◽

Vol 7 (3.27) ◽

pp. 456

Author(s):

Albi . ◽

M Dev Anand ◽

G M. Joselin Herbert

Keyword(s):

Wind Turbine ◽

Turbine Blade ◽

Cfd Simulation ◽

Turbine Blades ◽

Wind Turbine Blade ◽

Wind Turbine Blades ◽

Ansys Fluent ◽

Wind Speeds ◽

Drag Forces ◽

The aerofoils of wind turbine blades have crucial influence on aerodynamic efficiency of wind turbine. There are numerous amounts of research being performed on aerofoils of wind turbines. Initially, I have done a brief literature survey on wind turbine aerofoil. This project involves the selection of a suitable aerofoil section for the proposed wind turbine blade. A comprehensive study of the aerofoil behaviour is implemented using 2D modelling. NACA 4412 aerofoil profile is considered for analysis of wind turbine blade. Geometry of this aerofoil is created using GAMBIT and CFD analysis is carried out using ANSYS FLUENT. Lift and Drag forces along with the angle of attack are the important parameters in a wind turbine system. These parameters decide the efficiency of the wind turbine. The lift force and drag force acting on aerofoil were determined with various angles of attacks ranging from 0° to 12° and wind speeds. The coefficient of lift and drag values are calculated for 1×105 Reynolds number. The pressure distributions as well as coefficient of lift to coefficient of drag ratio of this aerofoil were visualized. The CFD simulation results show close agreement with those of the experiments, thus suggesting a reliable alternative to experimental method in determining drag and lift.

Development and Application of a Simulation Tool for Vertical and Horizontal Axis Wind Turbines

Volume 8: Supercritical CO2 Power Cycles; Wind Energy; Honors and Awards ◽

10.1115/gt2013-94979 ◽

2013 ◽

Cited By ~ 5

Author(s):

David Marten ◽

Juliane Wendler ◽

Georgios Pechlivanoglou ◽

Christian Navid Nayeri ◽

Christian Oliver Paschereit

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Vertical Axis ◽

Turbine Rotor ◽

Horizontal Axis ◽

Vertical Axis Wind Turbine ◽

First Case ◽

Horizontal Axis Wind Turbines ◽

Lift And Drag ◽

A double-multiple-streamtube vertical axis wind turbine simulation and design module has been integrated within the open-source wind turbine simulator QBlade. QBlade also contains the XFOIL airfoil analysis functionalities, which makes the software a single tool that comprises all functionality needed for the design and simulation of vertical or horizontal axis wind turbines. The functionality includes two dimensional airfoil design and analysis, lift and drag polar extrapolation, rotor blade design and wind turbine performance simulation. The QBlade software also inherits a generator module, pitch and rotational speed controllers, geometry export functionality and the simulation of rotor characteristics maps. Besides that, QBlade serves as a tool to compare different blade designs and their performance and to thoroughly investigate the distribution of all relevant variables along the rotor in an included post processor. The benefits of this code will be illustrated with two different case studies. The first case deals with the effect of stall delaying vortex generators on a vertical axis wind turbine rotor. The second case outlines the impact of helical blades and blade number on the time varying loads of a vertical axis wind turbine.

Experimental Study of the Vertical Hydraulic Drag Force on Regular Tetrahedron

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.860-863.1547 ◽

2013 ◽

Vol 860-863 ◽

pp. 1547-1550

Author(s):

Rui Le ◽

Wei Jiang ◽

Qi Liu ◽

Nan Chang Sun ◽

Bing Xu

Keyword(s):

Experimental Study ◽

Drag Coefficient ◽

Drag Force ◽

Vertical Velocity ◽

Hydraulic Engineering ◽

Hydraulic Drag ◽

Regular Tetrahedron ◽

Impact Effect ◽

Drag Forces ◽

It is well known that the hydraulic drag force on objects cant be ignored in computing the movement of objects in water. And the drag forces on sphere and cuboids have long been studied. While in hydraulic engineering, objects with regular tetrahedron shape are widely used to form the foundation and temporary dam for they can interlock each other to obtain a compacted integral. In this article the vertical hydraulic drag force on regular tetrahedron is studied by indoor experiments, the relation of the vertical hydraulic drag coefficient and the vertical velocity is proposed. And the max vertical speeds of different materials are deduced. The result is helpful to compute the movement of regular tetrahedron in water and estimate the impact effect on the groundwork.

Analysis of lift and drag coefficients of a GT2 racing car at various speeds with movable wheels and ground

World Journal of Engineering ◽

10.1260/1708-5284.12.3.261 ◽

2015 ◽

Vol 12 (3) ◽

pp. 261-270

Author(s):

Albert Boretti

Keyword(s):

Wind Tunnel ◽

Drag Force ◽

Computational Fluid Dynamic ◽

Lift Force ◽

Fluid Dynamic ◽

Time Simulation ◽

Rear Wing ◽

Speed Range ◽

Drag And Lift ◽

The paper proposes a study of a GT2 racing car with a computational fluid dynamic (CFD) tool. Results of STAR-CCM+ simulations of the flow around the car in a wind tunnel with movable ground and wheels are presented for different air speeds to assess the different contributions of pressure and shear to lift and drag over the speed range. The rear wing contributes more than 85% of the lift force and 7-8% of the drag force for this particular class of racing cars. When reference is made to the low speed drag and lift coefficients, increasing the speed from 25 to 100 m/s produces an increase of CD of more than 3% and a reduction of CL of more than 2%. The resultsuggests modifying the constant CD and CL values used in lap time simulation toolsintroducing the tabulated values to interpolate vs. the speed of the car.

Forces on particles in oscillatory boundary layers

Journal of Fluid Mechanics ◽

10.1017/s0022112002001234 ◽

2002 ◽

Vol 468 ◽

pp. 327-347 ◽

Cited By ~ 16

Author(s):

PAUL F. FISCHER ◽

GARY K. LEAF ◽

JUAN M. RESTREPO

Keyword(s):

Numerical Simulation ◽

Direct Numerical Simulation ◽

Boundary Layers ◽

Lift Force ◽

Drag Forces ◽

Buoyancy Forces ◽

Lift Forces ◽

Lift And Drag ◽

Standing Question ◽

Oscillatory Boundary Layers

The lift and drag forces on an isolated particle resulting from an oscillating wall- bounded flow, are approximated using direct numerical simulation and extrapolation techniques. We also confirm the existence of anomalies in the lift force, which arise from the interaction of the vortical field with the particle. Anomalies can also occur for computational reasons and these are discussed as well.This study was motivated by a long-standing question about the importance of lift forces in the dynamics of sediments in oceanic settings. To answer this question we use the numerically generated data as well as extrapolations to compute the ratio of the lift to buoyancy forces on a particle. This analysis suggests that for particles and oceanic conditions typical of the nearshore, the lift force can play a role in the dynamics of sedimentary beds.

Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4048451 ◽

2020 ◽

Vol 142 (11) ◽

Author(s):

Francesco Papi ◽

Lorenzo Cappugi ◽

Sebastian Perez-Becker ◽

Alessandro Bianchini

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Prolonged Exposure ◽

Leading Edge ◽

Future Generation ◽

Operating Conditions ◽

Wind Speeds ◽

And Performance ◽

Lift And Drag ◽

Abstract Wind turbines operate in challenging environmental conditions. In hot and dusty climates, blades are constantly exposed to abrasive particles that, according to many field reports, cause significant damages to the leading edge. On the other hand, in cold climates similar effects can be caused by prolonged exposure to hail and rain. Quantifying the effects of airfoil deterioration on modern multi-MW wind turbines is crucial to correctly schedule maintenance and to forecast the potential impact on productivity. Analyzing the impact of damage on fatigue and extreme loading is also important to improve the reliability and longevity of wind turbines. In this work, a blade erosion model is developed and calibrated using computational fluid dynamics (CFD). The Danmarks Tekniske Universitet (DTU) 10 MW Reference Wind Turbine is selected as the case study, as it is representative of the future generation wind turbines. Lift and Drag polars are generated using the developed model and a CFD numerical setup. Power and torque coefficients are compared in idealized conditions at two wind speeds, i.e., the rated speed and one below it. Full aero-servo-elastic simulations of the turbine are conducted with the eroded polars using NREL's BEM-based code OpenFAST. Sixty-six 10-min simulations are performed for each stage of airfoil damage, reproducing operating conditions specified by the IEC 61400-1 power production DLC-group, including wind shear, yaw misalignment, and turbulence. Aeroelastic simulations are analyzed, showing maximum decreases in CP of about 12% as well as reductions in fatigue and extreme loading.

Numerical Investigation of the Hydrodynamics of Changing Fin Positions within a 4-Fin Surfboard Configuration

Applied Sciences ◽

10.3390/app10030816 ◽

2020 ◽

Vol 10 (3) ◽

pp. 816

Author(s):

Sebastian Falk ◽

Stefan Kniesburges ◽

Rolf Janka ◽

Tom O’Keefe ◽

Roberto Grosso ◽

...

Keyword(s):

Fluid Dynamics ◽

Lift Force ◽

Longitudinal Axis ◽

Parameter Study ◽

Computational Investigation ◽

Inflow Velocity ◽

Drag Forces ◽

Computational Fluid Dynamics Cfd ◽

Simulation Results ◽

Most sports like surfing are highly developed. It is necessary to tease the last percentages out of the competitors and equipment—in the case of surfing the surfboard-fin-system—to win competitions or championships. In this computational investigation, a parameter study of the positioning of the two rear fins within a 4-fin configuration with fixed front fins on a surfboard is executed to find appropriate fin positions for specific surf situations. Four different inflow velocities are investigated. The RANS and URANS models combined with the SST k − ω turbulence model, which is available within the computational fluid dynamics (CFD) package STAR-CCM+, are used to simulate the flow field around the fins for angles of attack (AoA) between 0° and 45°. The simulation results show that shifting the rear fins toward the longitudinal axis of the surfboard lowers the maximum lift. Surfboards with 4-fin configurations are slower in nearly the whole range of AoA due to a higher drag force but produce a higher lift force compared to the 3-fin configuration. The lift and drag forces increase significantly with increasing inflow velocity. This study shows a significant influence of the rear fin positioning and the inflow velocity on lift and drag performance characteristics.