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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Mertens, Christoph Cordero, Tomas de Rojas Sodja, Jurij Sciacchitano, Andrea van Oudheusden, Bas W. Delft Univ Technol Fac Aerosp Engn Aerodynam Dept NL-2629 HS Delft Netherlands Delft Univ Technol Fac Aerosp Engn Aerosp Struct & Mat Dept NL-2629 HS Delft Netherlands

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

The three components in Collar's triangle of forces (aerodynamic, elastic and inertial) acting on a flexible wing are determined, based on integrated optical measurements of the structural and the aerodynamic response to steady and unsteady periodic inflow conditions. The measurement device is a coaxial volumetric velocimeter mounted on a robotic arm, which is used to perform optical measurements of fiducial markers on the wing surface and simultaneously of helium-filled soap bubbles that are used as flow tracers. The optical measurements of the structural markers and the flow tracers are both processed with the Lagrangian particle tracking algorithm Shake-The-Box. Subsequently, physical models are used to determine the inertial and the elastic force of the aeroelastic interaction from the marker tracking results, and to determine the unsteady aerodynamic lift force from the flow velocity fields. The results of this integrated aeroelastic characterization approach are in physical agreement with each other according to the equilibrium of forces in Collar's triangle and good agreement with external reference measurements.

关键词： rectangular wing Particle Tracking Velocimetry Freestream Velocity Fiducial Marker Flow Velocity Lagrangian Particle Tracking Finite Element Formulation Euler Bernoulli Beams Wind Tunnel Tests Irrotational Flow

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Low-Order Modeling of wing-Tip Vortices Using an Augmented Vortex Lattice Method

Low-Order Modeling of Wing-Tip Vortices Using an Augmented V...

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AIAA Aviation Forum and Exposition

作者： Loewenthal, Ethan Gopalarathnam, Ashok North Carolina State Univ Dept Mech & Aerosp Engn Raleigh NC 27695 USA

ISBN: (数字)9781624105890

ISBN: (纸本)9781624105890

wing-tip flow effects become increasingly significant in the prediction of forces and moments on a wing as the aspect ratio decreases. Similar to the attached leading-edge vortex of delta wings, the wing-tip vortex is a flow structure that results in a supplementary lift known as "vortex lift," and is not captured by conventional vortex lattice method (VLM) models. Many augmented VLMs have addressed these free vortical flows on the leading edges of delta wings and wing tips. The current work consists of an augmented VLM designed to capture the geometry and strength of the free tip vortex along the wing tip, and is distinguished from prior models by its allocation of vorticity between the wing tip and the tip vortex at each chordwise position. Where the total vorticity along the tip exceeds a maximum allowable value, vorticity is shed to feed the free vortex. This paper presents the model and its predictions of tip-vortex positions, as well as forces and moments on low-aspect-ratio wings. The model demonstrates lift distributions typical of vortex lift, as well as promising initial agreement with forces and moments from experimental work. Furthermore, it is demonstrated that forces and moments may be controlled by adjusting the maximum allowable bound vorticity along the wing tips.

关键词： Vortex Lattice Method wing Tip Horseshoe Vortex Flow Visualization rectangular wing Kutta Joukowski Theorem High Aspect Ratio Delta wing Configuration Lift Coefficient Flow Separation

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AERODYNAMIC CHARACTERISTICS OF rectangular wingS AT SUPERSONIC SPEEDS

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JOURNAL OF THE AERONAUTICAL SCIENCES 1947年第2期14卷 110-116页

作者： BONNEY, EA Applied Physics Laboratory The Johns Hopkins University

By combined use of A. BUSEMANN second order approximation theory for pressure distribution over two-dimensional airfoil with straight leading edge and theory for loss in lift at tips of rectangular airfoil in supersonic flow, expressions for lift, drag, and moment coefficients and center of pressure are derived for rectangular type of wing. (See also - discussion n 6, 7, June p 335-6, July p 409-10, 432)

关键词： Aerodynamic Characteristics rectangular wing Supersonic Speed High Aspect Ratio Center of Pressure Lift Coefficient Two Dimensional Flow Thickness Ratio Mach Angle Skin Friction Drag

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wing Planform Effects on the Aerodynamic Performance of Insect-Like Revolving wings

Wing Planform Effects on the Aerodynamic Performance of Inse...

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AIAA Aviation Forum

作者： Broadley, Paul A. Nabawy, Mostafa R. A. Quinn, Mark K. Crowther, William J. Univ Manchester Sch Engn Dept Mech Aerosp & Civil Engn Manchester M1 3BB Lancs England Cairo Univ Dept Aerosp Engn Fac Engn Giza Egypt

ISBN: (数字)9781624105982

ISBN: (纸本)9781624105982

Simple revolving wing experiments provide a useful means to simulate the translational aerodynamics and measure the lift and drag characteristics of insect-like wing planforms. In this study, nine wings based on the beta chord distribution are employed. The wing planforms are varied in a systematic fashion to represent three aspect ratio and three area centroid location values. The steady lift and drag characteristics are measured for these wings at Reynolds number of 10(4) representing an upper bound for insect flight operational regime. It is shown that that the measured lift and drag coefficients reasonably follow the trends from the simple normal force theoretical model. wing area centroid location showed greater effect on the measured force coefficients than the aspect ratio. The general trend found is that lift coefficient values will increase with the increase in both area centroid location and aspect ratio. Peak drag coefficient values still showed an increasing trend with the increase of area centroid location, but showed a decreasing trend with the increase in aspect ratio.

关键词： Aerodynamic Performance High Aspect Ratio Aerodynamic Characteristics wing Root rectangular wing Thickness to Chord Ratio Skin Friction Drag Vortices Flow Visualization Flow Conditions

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wing optimization using dual number automatic differentiation in MachUp 55

Wing optimization using dual number automatic differentiatio...

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55th AIAA Aerospace Sciences Meeting

作者： Hodson, Joshua D. Hunsaker, Douglas F. Spall, Robert E. Utah State University Mechanical and Aerospace Engineering 4130 Old Main Hill LoganUT84322 United States

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

The design and optimization of lifting surfaces on an aircraft is a difficult problem, and is typically performed using computational fluid dynamics, which is an expensive process. This paper demonstrates the capabilities of MachUp and Optix to provide cheap early-design optimization of lifting surfaces. MachUp is an open-source software tool that implements a modern numerical lifting-line algorithm to compute lift and drag for multiple lifting surfaces with arbitrary twist, sweep, and dihedral. Optix is an open-source software tool that implements the BFGS optimization algorithm for solving nonlinear optimization problems. Derivatives needed by Optix can be computed using Dual Number Automatic Differentiation, an open-source Fortran library which implements forward-mode Automatic Differentiation using derived types and operator overloading. The use of automatic differentiation decreases computational cost and increases accuracy of the derivatives. Results are presented which demonstrate efficient and accurate optimization of lifting surfaces to minimize induced drag through variation of chord, twist, and camber. © 2017 by Douglas F. Hunsaker and Josh Hodson. Published by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Aerodynamic Characteristics FORTRAN Camber Computational Fluid Dynamics Open Source Software Optimization Algorithm High Aspect Ratio Lift Coefficient rectangular wing Thin Airfoil Theory

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Rudimentary Emulation of Covert Feathers on Low-AR wings for Poststall Lift Enhancement

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AIAA JOURNAL 2020年第2期58卷 501-516页

作者： Arivoli, D. Singh, Ishan Suriyanarayanan, P. Natl Aerosp Labs Expt Aerodynam Div Bangalore 560017 Karnataka India

Covert feathers, a group of feathers on the upper surface of bird wings, are one of birds' features that aid them in flight at high angles of attack, making them more maneuverable. In a previous study, the authors found that a rudimentary emulation of this feature (termed a self-adaptive flap) enhances the poststall lift characteristics of low-aspect-ratio flat-plate wings at Re=100,000. This enhancement, however, was found to vary with the different chordwise locations of the flap and across different planforms. In a continued effort to understand this further, two-dimensional particle image velocimetry investigation was carried out in the midspan plane of the low-aspect-ratio wings. For the varying-span elliptical wings, the results reveal that the flap/shear layer interaction promotes reattachment of the separated shear layer via increased entrainment. This reattachment location varies for the different chordwise location of the flap, resulting in a different extent of the separation bubble and bubble-induced camber, which in turn is responsible for different poststall lift enhancement. On the other hand, for the rectangular wing, the flap promotes large-scale vortex formation. The formation and shedding cycle of large-scale vortices has a significant impact on the mean-body forces because of which the time-averaged poststall lift is enhanced.

关键词： Flow Separation Aerodynamic Performance Strouhal Number Particle Image Velocimetry Aspect Ratio rectangular wing Thickness to Chord Ratio Camber Kutta Condition Aerodynamic Characteristics

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Angle of Attack and Core Size Effects on Transitional Vortical-Gust-Airfoil Interactions

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AIAA JOURNAL 2020年第7期58卷 2881-2898页

作者： Barnes, Caleb J. Visbal, Miguel R. US Air Force Res Lab Aerodynam Technol Branch Wright Patterson AFB OH 45433 USA

This paper presents high-fidelity implicit large-eddy simulations of counterclockwise-oriented parallel vortical gust interactions with a NACA0012 airfoil operating at a transitional chord-based Reynolds number ofRec=200,000. Both the angle of attack (alpha=4, 8, and 12 deg) and gust core size (rv/c=0.125, 0.25, and 0.50) are varied. In all cases, flow disruptions induced by the various gust encounters are analyzed alongside the corresponding aerodynamic load perturbations. Equivalent inviscid simulations supplement the present flow analyses. Boundary-layer disruption exhibits increased complexity at higher angles of attack characterized by a more coherent leading edge vortex (LEV) and a secondary boundary-layer disruption further downstream. By alpha=12 degthese features begin to resemble dynamic stall. Both flow laminarization upstream of the induced LEV and lower boundary-layer breakup are less pronounced as angle of attack increases. Interaction with a large gust,rv/c=0.50, at the lowest angle of attack,alpha=4 deg, produced a response similar to that observed in the higher alpha encounters, that is, more coherent LEV and secondary boundary-layer disruptions downstream.

关键词： Lift Coefficient Airfoil Boundary Layer Transition Freestream Mach Number Vortex Modeling rectangular wing Direct Numerical Simulation Pressure Coefficient Transitional Flow Blade Vortex Interaction

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A practical method for aerodynamic investigation of WIG

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AIRCRAFT ENGINEERING AND AEROSPACE TECHNOLOGY 2016年第1期88卷 73-81页

作者： Seif, Mohammad Saeed Dakhrabadi, Mohammad Tavakoli Sharif Univ Technol Dept Mech Engn Ctr Excellence Dynam & Hydrodynam Marine Vehicles Tehran Iran

Purpose - The purpose of this paper is to present a fast, economical and practical method for mathematical modeling of aerodynamic characteristics of rectangular wing in ground (WIG) effect. Design/methodology/approach - Reynolds averaged Navier-Stokes (RANS) equations were converted to Bernoulli equation by reasonable assumptions. Also, Helmbold's equation has been developed for calculation of the slope of wing lift coefficient in ground effect by defining equivalent aspect ratio (ARe). Comparison of present work results against the experimental results has shown good agreement. Findings - A practical mathematical modeling with lower computational time and higher accuracy was presented for calculating aerodynamic characteristics of rectangular WIG effect. The relative error between the present work results and the experimental results was less than 8 per cent. Also, the accuracy of the proposed method was checked by comparing with the numerical methods. The comparison showed fairly good accuracy. Research limitations/implications - Aerodynamic surfaces in ground effect were used for reducing wetted surface and increasing speed in high-speed marine and novel aeronautical vehicles. Practical implications - The proposed method is useful for investigation of aerodynamic performance of WIG vehicles and racing boats with aerodynamic surfaces in ground effect. Originality/value - The proposed method has reduced the computational time significantly as compared to numerical simulation that allows conceptual design of the WIG crafts and is also economical.

关键词： Aerodynamic characteristics Ground effect Mathematical modeling rectangular wing

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Heat transfer enhancement by twisted tapes with alternate-axes and triangular, rectangular and trapezoidal wings

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CHEMICAL ENGINEERING AND PROCESSING-PROCESS INTENSIFICATION 2011年第2期50卷 211-219页

作者： Wongcharee, Khwanchit Eiamsa-Ard, Smith Mahanakorn Univ Technol Fac Engn Dept Chem Engn Bangkok 10530 Thailand Mahanakorn Univ Technol Fac Engn Dept Mech Engn Bangkok 10530 Thailand

The effects of twisted tapes with alternate-axes and wings on heat transfer, flow friction and thermal performance characteristics in a round tube are investigated. The influence of wing shape including triangle, rectangle and trapezoid is also studied. The experiments are performed using twisted tape with three different wing-chord ratios (d/W) of 0.1, 0.2 and 0.3 and constant twist ratio (y/W) of 4.0. The alternate-axis is made by arranging each plane of twisted tape to 60 degree difference relative to the adjacent plane. The results show that both heat transfer rate and friction factor associated by all twisted tape are consistently higher than those without twisted tape. Under the similar operating conditions. Nusselt number, friction factor as well as thermal performance factor given by the tape with alternate-axes and trapezoidal wings are higher than those given by the others. It is also found that that Nusselt number, friction factor and thermal performance increase with increasing wing-chord ratio. The maximum thermal performance factor of 1.42 is found with the use of twisted tape with alternate-axes and trapezoidal wings at d/W = 0.3, where the heat transfer rate and friction factor, respectively increase to 2.84 and 8.02 times of those in the plain tube. (c) 2010 Elsevier B.V. All rights reserved.

关键词： Heat transfer enhancement Friction factor Twisted tape Swirl flow Alternate axis Triangular wing rectangular wing Trapezoidal wing

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Effect of the perforation design on the fluid flow and heat transfer characteristics of a plate fin heat exchanger

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2018年 126卷 172-180页

作者： Boukhadia, Karima Ameur, Houari Sahel, Djamel Bozit, Mohamed Ctr Univ Naama Univ Ctr Salhi Ahmed Naama Inst Sci & Technol Dept Technol PB 66 Naama 45000 Algeria USTO MB Fac Mech Engn 1505 El Mnaouar Oran 31000 Algeria Univ Amar Thilidji Laghouat Dept Tech Sci Laghouat Algeria

Three dimensional numerical simulations are carried out to explore the performance of vortex generators in a plate fin heat exchanger. rectangular and perforated wings are used as vortex generators to enhance the heat transfer rates. A comparison is made between the performances of a plate fin with and without baffles. When the heat exchanger is equipped with baffles, the efficiency of two configurations was compared: a baffle with and without perforation. Also, the effects of the perforation shape were studied. It concerns three cases: rectangular, triangular and circular. Validation of our numerical results with the available experimental data has revealed a satisfactory agreement. The obtained results show that the baffled cases perform better than the unbaffled one. The performance factor is found to be higher in the perforated baffle than the baffle without perforation. Compared to the unbaffled case, the maximum thermal performance factor (TPF) of 2.14 was obtained with the circular perforated baffle, followed by the rectangular perforated baffle (TPF = 1.57), triangular baffle (TPF = 1.46) and finally the baffle without perforation (TPF = 1.41). At the end of paper, new correlations for the prediction of friction factor and Nusselt number depending on Reynolds number and the shape of perforation in baffles are developed.

关键词： Plate fin heat exchanger Vortex generator Perforated baffle rectangular wing Shear thinning fluid

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