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.

scholarly journals Aerodynamic Performance of the NREL S826 Airfoil in Icing Conditions

2017 ◽  
Author(s):  
Julie Krøgenes ◽  
Lovisa Brandrud ◽  
Richard Hann ◽  
Jan Bartl ◽  
Tania Bracchi ◽  
...  
Keyword(s):  
Wind Farm ◽  
Aerodynamic Performance ◽  
Cold Climate ◽  
Navier Stokes ◽  
Computational Results ◽  
Energy Potential ◽  
Pressure Distributions ◽  
Wind Energy Potential ◽  
Experimental Values ◽  
Lift And Drag

Abstract. The demand for wind power is rapidly increasing, creating opportunities for wind farm installations in more challenging climates. Cold climate areas, where ice accretion can be an issue, are often sparsely populated and have high wind energy potential. Icing may lead to severely reduced aerodynamic performance and thereby reduced power output. To reach a greater understanding of how icing affects the aerodynamics of a wind turbine blade, three representative icing cases; rime ice, glaze ice and a mixed ice, were defined and investigated experimentally and computationally. Experiments at Re = 1.0 × 105–4.0 × 105 were conducted in the low-speed wind tunnel at NTNU on a two dimensional wing with applied 3D-printed ice shapes, determining lift, drag and surface pressure distributions. Computational results, obtained from the Reynolds Averaged Navier–Stokes fluid dynamics code FENSAP, complement the experiments. Measured and predicted data show a reduction in lift for all icing cases. Most severe is the mixed ice case, with a lift reduction of up to 30 % in the linear lift area, compared to a clean reference airfoil. Computational results show an under-prediction in maximum lift of 7–18 % compared to experimental values. Curvature and tendencies for both lift and drag show good agreement between simulations and experiment.

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.

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.

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.

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.

scholarly journals Performance analysis of a Darrieus-type wind turbine for a series of 4-digit NACA airfoils

2019 ◽  
Author(s):  
Krzysztof Rogowski ◽  
Martin Otto Laver Hansen ◽  
Galih Bangga
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Point Of View ◽  
Navier Stokes ◽  
Vertical Axis Wind Turbine ◽  
Wide Range ◽  
Sst Turbulence Model ◽  
Lift And Drag ◽  
Blade Loads

Abstract. The purpose of this paper is to estimate the H-Darrieus wind turbine aerodynamic performance, aerodynamic blade loads and velocity profiles downstream behind the rotor. The wind turbine model is based on the rotor designed by McDonnell Aircraft Company. The model proposed here consists of three fixed straight blades; in the future this model is planned to be develop with controlled blades. The study was conducted using the unsteady Reynolds averaged Navier-Stokes (URANS) approach with the k-ω shear stress transport (SST) turbulence model. The numerical two-dimensional model was verified using two other independent aerodynamic approaches: the vortex model developed in Technical University of Denmark (DTU) and the extended version of the CFD code FLOWer at the University of Stuttgart (USTUTT). All utilized numerical codes gave similar result of the instantaneous aerodynamic blade loads. In addition, steady-state calculations for the applied airfoils were also made using the same numerical model as for the vertical axis wind turbine (VAWT) to obtain lift and drag coefficients. The obtained values of lift and drag force coefficients, for a Reynolds number of 2.9 million, agree with the predictions of the experiment and XFoil over a wide range of angle of attack. The maximum rotor power coefficients are obtained at 0.5, which makes this impeller attractive from the point of view of further research. This work also addresses the issue of determining the aerodynamic performance of the rotor with various 4-digit NACA airfoils. The effect of two airfoil parameters, maximum airfoil thickness and maximum camber, on aerodynamic rotor performance is investigated. Research has shown that if this rotor were to work with fixed blades it is recommended to use the NACA 1418 airfoil instead of the original NACA 0018.

A Computational Study of the Flow Around an Isolated Wheel in Contact With the Ground

2005 ◽  
Vol 128 (3) ◽  
pp. 520-530 ◽  
Author(s):  
James McManus ◽  
Xin Zhang
Keyword(s):  
Computational Study ◽  
Experimental Results ◽  
Navier Stokes ◽  
Flow Structures ◽  
Road Vehicles ◽  
Accurate Representation ◽  
Drag Forces ◽  
Mechanisms Of Formation ◽  
Lift And Drag ◽  
Good Agreement

The flow around an isolated wheel in contact with the ground is computed by the Unsteady Reynolds-Averaged Navier-Stokes (URANS) method. Two cases are considered, a stationary wheel on a stationary ground and a rotating wheel on a moving ground. The computed wheel geometry is a detailed and accurate representation of the geometry used in the experiments of Fackrell and Harvey. The time-averaged computed flow is examined to reveal both new flow structures and new details of flow structures known from previous experiments. The mechanisms of formation of the flow structures are explained. A general schematic picture of the flow is presented. Surface pressures and pressure lift and drag forces are computed and compared to experimental results and show good agreement. The grid sensitivity of the computations is examined and shown to be small. The results have application to the design of road vehicles.

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

2004 ◽  
Vol 127 (3) ◽  
pp. 583-594 ◽  
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.

scholarly journals Optimal Aerodynamic Shape Optimization of a Paraglider Airfoil Based on the Sharknose Concept

2018 ◽  
Vol 221 ◽  
pp. 05002
Author(s):  
Amir A. Abdelqodus ◽  
Innokentiy A. Kursakov
Keyword(s):  
Shape Optimization ◽  
Stokes Equations ◽  
Pressure Coefficient ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Aerodynamic Shape Optimization ◽  
Aerodynamic Shape ◽  
Air Inlet ◽  
Gradient Based ◽  
Lift And Drag

The effects of classical air inlet configurations on the aerodynamic performance of a paraglider airfoil are firstly presented. Followed by conducting gradient-based aerodynamic shape optimization of the baseline airfoil used in the investigation of the classical air inlets. Different air inlet configurations are introduced to the optimized profile, and there effects on the aerodynamic performance are then compared to the initial and optimized airfoils. The Reynolds averaged Navier-Stokes equations (RANS) are solved for the flow field around the closed and open airfoils. The canopy is assumed to be smooth, rigid and impermeable. Results are focused on both of lift and drag coefficients for performance analysis and on the internal pressure coefficient which can be critical for a real flexible wing regarding the risk of collapse.

A Novel Concept for Floating Offshore Wind Turbines: Recent Developments in the Concept and Investigation on Fluid Interaction With the Rotating Foundation

2010 ◽  
Author(s):  
Luca Vita ◽  
Frederik Zhale ◽  
Uwe S. Paulsen ◽  
Troels F. Pedersen ◽  
Helge A. Madsen ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Vertical Axis ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Navier Stokes ◽  
Drag Forces ◽  
Floating Offshore Wind Turbines ◽  
Recent Developments ◽  
Lift And Drag ◽  
Novel Concept

This paper describes the recent developments regarding a new concept for deep sea offshore vertical axis wind turbines. The concept utilizes a cylindrical foundation rotating in the water. The 2D Navier-Stokes solver EllipSys2D has been used to investigate the interaction between the rotating foundation and a water flow stream passing the turbine. Lift and drag forces, and the friction moment on the rotating foundation of the turbine have been computed. The calculations are repeated for different operating conditions of the wind turbine on a range of rotational speeds. The Reynolds number, based on the diameter of the foundation, is 5×106.

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