scholarly journals Effects of uniform vertical inflow perturbations on the performance of flapping wings

2021 ◽  
Vol 8 (6) ◽  
pp. 210471
Author(s):  
Soudeh Mazharmanesh ◽  
Jace Stallard ◽  
Albert Medina ◽  
Alex Fisher ◽  
Noriyasu Ando ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Control Strategies ◽  
Linear Increase ◽  
Flapping Wing ◽  
Flapping Wings ◽  
Drag Coefficients ◽  
Inflow Velocity ◽  
Wake Interaction ◽  
Significant Interest ◽  
Lift And Drag

Flapping wings have attracted significant interest for use in miniature unmanned flying vehicles. Although numerous studies have investigated the performance of flapping wings under quiescent conditions, effects of freestream disturbances on their performance remain under-explored. In this study, we experimentally investigated the effects of uniform vertical inflows on flapping wings using a Reynolds-scaled apparatus operating in water at Reynolds number ≈ 3600. The overall lift and drag produced by a flapping wing were measured by varying the magnitude of inflow perturbation from J Vert = −1 (downward inflow) to J Vert = 1 (upward inflow), where J Vert is the ratio of the inflow velocity to the wing's velocity. The interaction between flapping wing and downward-oriented inflows resulted in a steady linear reduction in mean lift and drag coefficients, C ¯ L and C ¯ D , with increasing inflow magnitude. While a steady linear increase in C ¯ L and C ¯ D was noted for upward-oriented inflows between 0 < J Vert < 0.3 and J Vert > 0.7, a significant unsteady wing–wake interaction occurred when 0.3 ≤ J Vert < 0.7, which caused large variations in instantaneous forces over the wing and led to a reduction in mean performance. These findings highlight asymmetrical effects of vertically oriented perturbations on the performance of flapping wings and pave the way for development of suitable control strategies.

Induced Strain Actuation for Solid-State Ornithopters: An Aeroelastic Study

2018 ◽  
Author(s):  
Francis Hauris ◽  
Onur Bilgen
Keyword(s):  
Reynolds Number ◽  
Solid State ◽  
Aspect Ratio ◽  
Interaction Model ◽  
Flapping Wing ◽  
Flapping Wings ◽  
Structural Behavior ◽  
Structure Interaction ◽  
Dynamic Motion ◽  
Lift And Drag

This paper investigates the dynamic aeroelastic behavior of strain actuated flapping wings with various geometries and boundary conditions. A fluid-structure interaction model of a plate-like flapping wing is developed. Assuming a chord Reynolds number of 100,000, the wing is harmonically actuated while varying parameters such as aspect ratio and wing root clamped percentage. Characteristic metrics for the dynamic motion, natural frequency, lift and drag are developed. These results are compared with purely structural behavior to understand the aeroelastic effects.

Design and Analysis of Flapping Wing

2011 ◽  
Vol 110-116 ◽  
pp. 3495-3499
Author(s):  
G.C. Vishnu Kumar ◽  
M. Rahamath Juliyana
Keyword(s):  
Experimental Data ◽  
Flapping Wing ◽  
Micro Air Vehicle ◽  
Flapping Wings ◽  
Visualization Technique ◽  
Aerodynamic Forces ◽  
Flapping Motion ◽  
Smoke Flow ◽  
Air Vehicle ◽  
Lift And Drag

This paper the optimum wing planform for flapping motion is investigated by measuring the lift and drag characteristics. A model is designed with a fixed wing and two flapping wings attached to its trailing edge. Using wind tunnel tests are conducted to study the effect of angle of attack (smoke flow visualization technique). The test comprises of measuring the aerodynamic forces with flapping motion and without it for various flapping frequencies and results are presented. It can be possible to produce a micro air vehicle which is capable of stealthy operations for defence requirements by using these experimental data.

scholarly journals The flow induced by a rotationally oscillating and translating circular cylinder

2000 ◽  
Vol 407 ◽  
pp. 123-144 ◽  
Author(s):  
S. C. R. DENNIS ◽  
P. NGUYEN ◽  
SERPIL KOCABIYIK
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Interesting Phenomenon ◽  
Navier Stokes Equations ◽  
Drag Coefficients ◽  
Small Times ◽  
High Reynolds ◽  
Lift And Drag

The temporal development of two-dimensional viscous incompressible flow induced by an impulsively started circular cylinder which performs time-dependent rotational oscillations about its axis and translates at right angles to this axis is investigated. The investigation is based on the solutions of the unsteady Navier–Stokes equations. A series expansion for small times is developed. The Navier–Stokes equations are also integrated by a spectral–finite difference method for moderate values of time for both moderate and high Reynolds numbers. The numerical method is checked with the results of the analytical solution. The effects of the Reynolds number and of the forcing Strouhal number S on the laminar asymmetric flow structure in the near-wake region are studied. The lift and drag coefficients are also extracted from numerical results. An interesting phenomenon has been observed both in the flow patterns and in the behaviour of drag coefficients for S = π/2 at Reynolds number R = 500 and is discussed. For comparison purposes the start-up flow is determined numerically at a low Reynolds number and is found to be in good agreement with previous experimental predictions.

A Meta-Model for Aerodynamic Properties of a Reversible Profile in Cascade With Variable Stagger and Solidity

2018 ◽  
Author(s):  
Gino Angelini ◽  
Tommaso Bonanni ◽  
Alessandro Corsini ◽  
Giovanni Delibra ◽  
Lorenzo Tieghi ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pitch Angle ◽  
Cfd Simulation ◽  
Aerodynamic Performance ◽  
Specific Work ◽  
Drag Coefficients ◽  
Stall Margin ◽  
Meta Model ◽  
Aerodynamic Properties ◽  
Lift And Drag

In this paper, a systematic CFD work is carried out with the aim to inspect the influence of different cascade parameters on the aerodynamic performance of a reversible fan blade profile. From the obtained results, we derive a meta-model for the aerodynamic properties of this profile. Through RANS simulations of different arrangements in cascades, the aerodynamic performance of airfoils are analyzed as Reynolds number, solidity, pitch angle and angle of attack are varied. The definition of a trial matrix allows the reduction of the minimum number of simulations required. The computed CFD values of lift and drag coefficients, stall margin and the zero-lift angle strongly depend on cascade configuration and differ significantly from standard panel method software predictions. In this work, X-Foil has been used as a benchmark. Particularly, the high influence of pitch angle and solidity is here highlighted, while a less marked dependence from the Reynolds number has been found. Meta-models for lift and drag coefficients have been later derived, and an analysis of variance has improved the models by reducing the number of significant factors. The application of the meta-models to a quasi-3D in-house software for fan performance prediction is also shown. The effectiveness of the derived meta-models is proven through a spanwise comparison of a reversible fan with the X-Foil based and meta-model based versions of the software and 3D fields from a standard CFD simulation. The meta-model improves the software prediction capability, leading to a very low global overestimation of the specific work of the fan.

Numerical investigation of Gurney flap influences on aerodynamic performance of a pitching airfoil in low Reynolds number flow

2018 ◽  
Vol 233 (10) ◽  
pp. 3819-3832
Author(s):  
Alireza Naderi ◽  
Alireza Beiki ◽  
Bahram Tarvirdizadeh
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Aerodynamic Performance ◽  
Solid Boundary ◽  
Aerodynamic Efficiency ◽  
Drag Coefficients ◽  
Gurney Flap ◽  
Unified Algorithm ◽  
Low Reynolds ◽  
Lift And Drag

The main purpose of present work is to investigate the aerodynamic performance of a pitching NACA 0012 airfoil equipped with a Gurney flap in flow with low Reynolds number. The aerodynamic influences of flap location, mounting angle, and height are numerically studied. In this regard, a Lagrangian–Eulerian pressure-based numerical algorithm is developed on hybrid grids attached to a pitching solid boundary. A finite volume-based finite element method is used to discretize the governing equations. As reported in previously related studies, this unified algorithm could be used to solve the unsteady incompressible flow in domains with moving mesh and/or moving boundary with sufficient robustness and accuracy. The other advantage of this algorithm is that it does not need any type of dissipation term and/or damping function. Using this unified algorithm, the numerical experiments indicate that the Gurney flap increases the lift and drag coefficients and enhances the aerodynamic efficiency. The best aerodynamic performance is predicted for the case in which the flap is located at trailing edge with the mounting angle of 90°. The flap height is predicted to have different and most impacts on aerodynamic efficiency during upstroke and downstroke. The numerical results show that the airfoils equipped by flaps with height between 6% and 12% of the airfoil chord are the most aerodynamically efficient airfoils. Changing of lift and drag coefficients are due to increase of effective camber and thickness in all cases.

scholarly journals A Computational Investigation of Unsteady Aerodynamics of Insect-Inspired Fixed Wing Micro Aerial Vehicle’s 2D Airfoil

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Somashekar V
Keyword(s):  
Reynolds Number ◽  
Control Volume ◽  
Unsteady Aerodynamics ◽  
Aerodynamic Characteristics ◽  
Research Field ◽  
Drag Coefficients ◽  
Unsteady Aerodynamic ◽  
Air Vehicle ◽  
Lift And Drag ◽  
2D Airfoil

A Micro air vehicle (MAV) is defined as class of unmanned air vehicle (UAV) having a linear dimension of less than 15 centimeters and a mass of less than 100 grams with flight speeds of 6 to 12 meters per second. MAVs fall within a Reynolds number (Re) range of 50,000 and 120,000, in which many causes of unsteady aerodynamic effects are not fully understood. The research field of low Reynolds number aerodynamics is currently an active one, with many defence organizations, universities, and corporations working towards a better understanding of the physical processes of this aerodynamic regime. In the present work, it is proposed to study the unsteady aerodynamic analysis of 2D airfoil using CFD software and Xfoil panel code method. The various steps involved in this work are geometric modelling using CATIA V5R17, meshing using ICEM CFD, and solution and postprocessing through FLUENT. The finite control volume analysis and Xfoil panel code method has been carried out to predict aerodynamic characteristics such as lift coefficients, drag coefficients, moment coefficients, pressure coefficients, and flow visualization. The lift and drag coefficients were compared for all the simulations with experimental results. It was observed that for the 2D airfoil, lift and drag both compared well for the midrange angle of attack from −10 to 15 degree AOA.

scholarly journals An empirical model to determine lift and drag coefficients of cambered plates at moderate Reynolds numbers

2020 ◽  
pp. 095765092091531
Author(s):  
Esztella Balla ◽  
János Vad
Keyword(s):  
Reynolds Number ◽  
Empirical Model ◽  
Angle Of Attack ◽  
Reynolds Numbers ◽  
Third Order ◽  
Drag Coefficients ◽  
The Third ◽  
Lift And Drag

This article presents the lift and drag coefficients of cambered plate blade sections of different relative camber at moderate Reynolds numbers. Relative cambers between 0% and 8% are investigated at an angle of attack range from 0° to 10°. Based on own measurements and literature data, empirical formulae are proposed for the determination of the lift and drag coefficients for Reynolds numbers within the range of 60,000 to 300,000. The formulae determine the lift and drag coefficients as a function of angle of attack, relative camber, and Reynolds number. Third-order polynomials have been proven to be suitable for the empirical formulae. The coefficients of the third-order polynomials have been determined and reported by the authors herein.

Efficient flapping wing drone arrests high-speed flight using post-stall soaring

2020 ◽  
Vol 5 (44) ◽  
pp. eaba2386 ◽  
Author(s):  
Yao-Wei Chin ◽  
Jia Ming Kok ◽  
Yong-Qiang Zhu ◽  
Woei-Leong Chan ◽  
Javaan S. Chahl ◽  
...  
Keyword(s):  
High Speed ◽  
Electrical Power ◽  
Flapping Wing ◽  
Flapping Wings ◽  
Direct Drive ◽  
Wing Membrane ◽  
Air Speed ◽  
Lift And Drag ◽  
Smooth Transitions ◽  
High Thrust

The aerobatic maneuvers of swifts could be very useful for micro aerial vehicle missions. Rapid arrests and turns would allow flight in cluttered and unstructured spaces. However, these decelerating aerobatic maneuvers have been difficult to demonstrate in flapping wing craft to date because of limited thrust and control authority. Here, we report a 26-gram X-wing ornithopter of 200-millimeter fuselage length capable of multimodal flight. Using tail elevation and high thrust, the ornithopter was piloted to hover, fly fast forward (dart), turn aerobatically, and dive with smooth transitions. The aerobatic turn was achieved within a 32-millimeter radius by stopping a dart with a maximum deceleration of 31.4 meters per second squared. In this soaring maneuver, braking was possible by rapid body pitch and dynamic stall of wings at relatively high air speed. This ornithopter can recover to glide stability without tumbling after a 90-degree body flip. We showed that the tail presented a strong stabilizing moment under high thrust, whereas the wing membrane flexibility alleviated the destabilizing effect of the forewings. To achieve these demands for high thrust, we developed a low-loss anti-whirl transmission that maximized thrust output by the flapping wings to 40 grams in excess of body weight. By reducing the reactive load and whirl, this indirect drive consumed 40% less maximum electrical power for the same thrust generation than direct drive of a propeller. The triple roles of flapping wings for propulsion, lift, and drag enable the performance of aggressive flight by simple tail control.

scholarly journals RANS Simulations of Flow Past an DU-91-W2-250 Airfoil at High Reynolds Number

2018 ◽  
Vol 44 ◽  
pp. 00150
Author(s):  
Krzysztof Rogowski ◽  
Martin O.L. Hansen
Keyword(s):  
Reynolds Number ◽  
Navier Stokes ◽  
Transient Model ◽  
Drag Coefficients ◽  
Pressure Distributions ◽  
Sst Turbulence Model ◽  
Rans Simulations ◽  
High Reynolds ◽  
Lift And Drag ◽  
Good Agreement

This paper presents numerical results of the DU-91-W2-250 airfoil. Reynolds-averaged Navier–Stokes (RANS) simulations of the 2D profile are performed employing the Transient SST turbulence model. The airfoil was investigated for the Reynolds number of 6 106. Lift and drag coefficients are compared with the experimental data from LM Low Speed Wind Tunnel (LSWT). The results of lift and drag coefficients obtained using the SST Transient model are in a good agreement in comparison with the experiment in the angle of attack range from -10° to 10°. The static pressure distributions calculated by the SST Transition model are also in good agreement with the experiment.

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