Evaluating the Flow Fields Around Low Aspect Ratio Flat Plates in Wind Tunnel Turbulence

2013 ◽  
Author(s):  
Michael J. Sytsma ◽  
Lawrence S. Ukeiley
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Flow Fields ◽  
Flat Plates ◽  
Low Aspect Ratio

Mean Loads from Wind-Tunnel Turbulence on Low-Aspect-Ratio Flat Plates

2013 ◽  
Vol 50 (3) ◽  
pp. 863-870 ◽  
Author(s):  
Michael Jon Sytsma ◽  
Lawrence Ukeiley
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Flat Plates ◽  
Low Aspect Ratio

The development of the winged keel for twelve-metre yachts

1986 ◽  
Vol 173 ◽  
pp. 55-71 ◽  
Author(s):  
P. Van Oossanen ◽  
P. N. Joubert
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Experimental Analysis ◽  
Design Parameters ◽  
Low Aspect Ratio ◽  
Lifting Surface ◽  
Wind Tunnel Measurements ◽  
America’S Cup

In this paper the authors present a numerical and experimental analysis of the winged keel originally developed for the International twelve-metre class yacht Australia II that won the America's Cup in 1983. After briefly explaining why this keel was evolved in 1981, some basic considerations are presented relating keel performance to various design parameters. The results of numerical flow analyses and wind-tunnel measurements on a model of a winged keel are then presented and compared. The differences between the performance with and without winglets fitted to the keel are discussed. The fitting of winglets appreciably enhances the performance of a low-aspect-ratio lifting surface such as the keel of a twelve-metre yacht.

Three-Dimensional Simulation of Micro Air Vehicles with Low-Aspect-Ratio Wings

2007 ◽  
Vol 339 ◽  
pp. 377-381
Author(s):  
Xiao Quan Zhang ◽  
L. Tian
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Aspect Ratio ◽  
Low Reynolds Number ◽  
Three Dimensional ◽  
Micro Air Vehicles ◽  
Wind Tunnel Experiments ◽  
Low Aspect Ratio ◽  
Dimensional Simulation

Micro Air Vehicles (MAVs) are catching more and more attentions for their broad application in civilian and military fields. Since the theories on the aerodynamics of low Reynolds number are not maturely presented and the wind-tunnel experiments cost long periods and great expenses. The numerical simulation based on computational fluid dynamics (CFD) is a good method to choose. Through three-dimensional simulation of the wings, the aerodynamic characteristics of the flows around MAVs can be easily obtained. The tip vortices produced around low-Reynolds-number and low-aspect-ratio wings can increase the lift and stall angles. The result of numerical simulation can be used as references of theory analysis and wind-tunnel experiments.

scholarly journals WIND TUNNEL CALIBRATION, CORRECTIONS AND EXPERIMENTAL VALIDATION FOR FIXED-WING MICRO AIR VEHICLES MEASUREMENTS

Aviation ◽  
2020 ◽  
Vol 23 (4) ◽  
pp. 104-113
Author(s):  
Ahmed Aboelezz ◽  
Yunes Elqudsi ◽  
Mostafa Hassanalian ◽  
Ahmed Desoki
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Aspect Ratio ◽  
Low Reynolds Number ◽  
Micro Air Vehicles ◽  
Measured Data ◽  
Published Data ◽  
Low Aspect Ratio ◽  
Low Reynolds ◽  
Air Vehicles

The increase in the number of Unmanned Aerial Vehicles (UAVs) and Micro Air Vehicles (MAVs), which are used in a variety of applications has led to a surge in low Reynolds number aerodynamics research. Flow around fixedwing MAVs has an unusual behavior due to its low aspect ratio and operates at low Reynolds number, which demanded to upgrade the used wind tunnel for this study. This upgrade enables measuring the small aerodynamics forces and moment of fixed-wing MAVs. The wind tunnel used in this work is upgraded with a state of art data acquisition system to deal with the different sensors signals in the wind tunnel. For accurate measurements, the sting balance, angle sensor, and airspeed sensor are calibrated. For validation purposes, an experiment is made on a low aspect ratio flat plate wing at low Reynolds number, and the measured data are corrected and compared with published results. The procedure presented in this paper for the first time gave a detailed and complete guide for upgrading and calibrating old wind tunnel, all the required corrections to correct the measured data was presented, the turbulence level correction new technique presented in this paper could be used to estimate the flow turbulence effect on the measured data and correct the measured data against published data.

scholarly journals Role of the tip vortex in the force generation of low-aspect-ratio normal flat plates

2007 ◽  
Vol 581 ◽  
pp. 453-468 ◽  
Author(s):  
MATTHEW J. RINGUETTE ◽  
MICHELE MILANO ◽  
MORTEZA GHARIB
Keyword(s):  
Aspect Ratio ◽  
Vortex Formation ◽  
Three Dimensional ◽  
Unsteady Motion ◽  
Tip Vortex ◽  
Flat Plates ◽  
Low Aspect Ratio ◽  
Start Up ◽  
Image Velocimetry

We investigate experimentally the force generated by the unsteady vortex formation of low-aspect-ratio normal flat plates with one end free. The objective of this study is to determine the role of the free end, or tip, vortex. Understanding this simple case provides insight into flapping-wing propulsion, which involves the unsteady motion of low-aspect-ratio appendages. As a simple model of a propulsive half-stroke, we consider a rectangular normal flat plate undergoing a translating start-up motion in a towing tank. Digital particle image velocimetry is used to measure multiple perpendicular sections of the flow velocity and vorticity, in order to correlate vortex circulation with the measured plate force. The three-dimensional wake structure is captured using flow visualization. We show that the tip vortex produces a significant maximum in the plate force. Suppressing its formation results in a force minimum. Comparing plates of aspect ratio six and two, the flow is similar in terms of absolute distance from the tip, but evolves faster for aspect ratio two. The plate drag coefficient increases with decreasing aspect ratio.

Sailing Downwind: Aerodynamic Performance of the Velella Sail

1991 ◽  
Vol 158 (1) ◽  
pp. 117-132
Author(s):  
LISBETH FRANCIS
Keyword(s):  
Natural Selection ◽  
Wind Tunnel ◽  
Aspect Ratio ◽  
Hydrodynamic Force ◽  
Center Of Pressure ◽  
Aerodynamic Force ◽  
Aerodynamic Performance ◽  
Polar Plot ◽  
Low Aspect Ratio

Using a wind tunnel built over a shallow pool and methods devised for measuring the performance of yacht sails, I describe aerodynamic performance in situ for the sailor-by-the-wind, Velella velella. By contrast with designers of the modern yacht mainsail, natural selection has apparently favored stability and seaworthiness over performance to windward. The Velella sail is a low aspect ratio airfoil with an unusually flat polar plot. Primarily a drag-based locomotory structure, this thin, leaf-like sail generates maximum force when oriented at attack angles between 50° and 90°. In the wind tunnel, free-sailing animals spontaneously assumed stable orientations at attack angles ranging from 28° to 87° and sailed with their hulls approximately broadside to the apparent flow of oncoming water. At these angles, aerodynamic force on the sail is asymmetrical, with the center of pressure upwind of the sail midline. Since aerodynamic force on the sail is balanced at equilibrium by hydrodynamic force on the hull, this orientation must be caused by asymmetrical forces acting on surface and underwater parts as the wind drags the animal along the surface of the water.

scholarly journals Leading-Edge Vortex Characteristics of Low-Aspect-Ratio Sweptback Plates at Low Reynolds Number

2021 ◽  
Vol 11 (6) ◽  
pp. 2450
Author(s):  
Jong-Seob Han ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Leading Edge ◽  
Flapping Wing ◽  
Flat Plates ◽  
Leading Edge Vortex ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Oil Flow ◽  
Edge Vortex

A sweptback angle can directly regulate a leading-edge vortex on various aerodynamic devices as well as on the wings of biological flyers, but the effect of a sweptback angle has not yet been sufficiently investigated. Here, we thoroughly investigated the effect of the sweptback angle on aerodynamic characteristics of low-aspect-ratio flat plates at a Reynolds number of 2.85 × 104. Direct force/moment measurements and surface oil-flow visualizations were conducted in the wind-tunnel B at the Technical University of Munich. It was found that while the maximum lift at an aspect ratio of 2.03 remains unchanged, two other aspect ratios of 3.13 and 4.50 show a gradual increment in the maximum lift with an increasing sweptback angle. The largest leading-edge vortex contribution was found at the aspect ratio of 3.13, resulting in a superior lift production at a sufficient sweptback angle. This is similar to that of a revolving/flapping wing, where an aspect ratio around three shows a superior lift production. In the oil-flow patterns, it was observed that while the leading-edge vortices at aspect ratios of 2.03 and 3.13 fully covered the surfaces, the vortex at an aspect ratio of 4.50 only covered up the surface approximately three times the chord, similar to that of a revolving/flapping wing. Based on the pattern at the aspect ratio of 4.50, a critical length of the leading-edge vortex of a sweptback plate was measured as ~3.1 times the chord.

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