scholarly journals A Method for Continuous Study of Soaring and Windhovering Birds

2021 ◽  
Author(s):  
Matthew Penn ◽  
George Yi ◽  
Abdulghani Mohamed ◽  
Simon Watkins ◽  
Shane Windsor
Keyword(s):  
Wind Tunnel ◽  
Turbulent Flows ◽  
Flow Characteristics ◽  
Wind Tunnels ◽  
Hovering Flight ◽  
Flight Tests ◽  
Bird Flight ◽  
Future Studies ◽  
Avian Flight ◽  
Autonomous Aircraft

Abstract Avian flight continues to inspire aircraft designers. As the scales of autonomous aircraft reduce to those of birds and large insects, new control challenges are apparent when attempting to hold steady flight in turbulent atmospheric wind. Some birds, however, are capable of remarkably stable hovering flight in the same conditions. This work describes the development of a wind tunnel configuration that facilitates the study of flapless windhovering (hanging) and soaring bird flight in wind conditions replicating those in nature. Updrafts were generated by flow over replica “hills” and turbulence was introduced through upstream grids. Successful flight tests with windhovering nankeen kestrels (Falco cenchroides) were conducted, verifying that the facility is suitable for future studies investigating the flight of soaring and windhovering birds in smooth and turbulent flows. The wind tunnel allows the flow characteristics to be carefully controlled and measured, providing great advantages over outdoor flight tests. Also, existing wind tunnels may be readily configured using this method, eliminating the need for the development of dedicated bird flight wind tunnels.

Development of Large Intermittent Wind Tunnels

1955 ◽  
Vol 59 (532) ◽  
pp. 259-278 ◽  
Author(s):  
J. Lukasiewicz
Keyword(s):  
Mach Number ◽  
Wind Tunnel ◽  
Mass Flow ◽  
High Speed ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Wind Tunnels ◽  
Number Range ◽  
Pressure Storage ◽  
Vacuum Storage

SummaryTwo types of intermittent wind tunnel drives, the pressure storage drive(with atmospheric exhaust) and the vacuum storage drive (with atmospheric inlet), are examined and found to match well the tunnel pressure ratio-mass flow characteristics over a wide Mach number range (0 to 4). The design of components of intermittent wind tunnel installations, their operation and instrumentation are then considered in some detail. In order to increase the output of intermittent wind tunnels to a level comparable to that of continuously running tunnels, it is proposed to drive the models during each tunnel run through a range of incidence. This technique is at present under development in the National Aeronautical Establishment's High Speed Aerodynamics Laboratory and results so far obtained are discussed. Two tunnels are considered as examples of large intermittent installations: a 4 ft. square pressure-driven tunnel and a 6 ft. square vacuum-driven tunnel. The former is found to be a more compact and economical installation. Relative merits of continuous and intermittent installations are discussed.

Model Test Techniques Developed to Investigate the Wind Heeling Characteristics of Sailing Vessels and Their Response to Gusts

1991 ◽  
Author(s):  
Barry Deakin
Keyword(s):  
Wind Tunnel ◽  
Model Test ◽  
Wind Tunnels ◽  
Stability Assessment ◽  
Tunnel Floor ◽  
The Stability ◽  
Scaled Models ◽  
Scale Data ◽  
Heeling Moment ◽  
Gust Response

During the development of new stability regulations for the U.K. Department of Transport, doubt was cast over many of the assumptions made when assessing the stability of sailing vessels. In order to investigate the traditional methods a programme of work was undertaken including wind tunnel tests and full scale data acquisition. The work resulted in a much improved understanding of the behaviour of sailing vessels and indeed indicated that the conventional methods of stability assessment are invalid, the rules now applied in the U.K. being very different to those in use elsewhere. The paper concentrates on the model test techniques which were developed specifically for this project but which will have implications to other vessel types. The tests were of two kinds: measurement of the wind forces and moments on a sailing vessel; and investigation of the response of sailing vessels to gusts of wind. For the force and moment measurements models were mounted in a tank of water on a six component balance and tested in a large boundary layer wind tunnel. Previous tests in wind tunnels have always concentrated on performance and the heeling moments have not normally been measured correctly. As the measurements of heeling moment at a range of heel angles was of prime importance a new balance and mounting system was developed which enabled the above water part of the vessel to be modelled correctly, the underwater part to be unaffected by the wind, and the interface to be correctly represented without interference. Various effects were investigated including rig type, sheeting, heading, heel angle and wind gradient. The gust response tests were conducted with Froude scaled models floating in a pond set in the wind tunnel floor. A mechanism was installed in the tunnel which enabled gusts of various characteristics to be generated, and the roll response of the models was measured with a gyroscope. These tests provided information on the effects of inertia, damping, rolling and the characteristics of the gust. Sample results are presented to illustrate the uses to which these techniques have been put.

scholarly journals Aerodynamics of manoeuvring flight in brown long-eared bats ( Plecotus auritus )

2018 ◽  
Vol 15 (148) ◽  
pp. 20180441 ◽  
Author(s):  
Per Henningsson ◽  
Lasse Jakobsen ◽  
Anders Hedenström
Keyword(s):  
Particle Image Velocimetry ◽  
Wind Tunnel ◽  
High Speed ◽  
Particle Image ◽  
Future Studies ◽  
Image Velocimetry ◽  
Mechanistic Basis

In this study, we explicitly examine the aerodynamics of manoeuvring flight in animals. We studied brown long-eared bats flying in a wind tunnel while performing basic sideways manoeuvres. We used particle image velocimetry in combination with high-speed filming to link aerodynamics and kinematics to understand the mechanistic basis of manoeuvres. We predicted that the bats would primarily use the downstroke to generate the asymmetries for the manoeuvre since it has been shown previously that the majority of forces are generated during this phase of the wingbeat. We found instead that the bats more often used the upstroke than they used the downstroke for this. We also found that the bats used both drag/thrust-based and lift-based asymmetries to perform the manoeuvre and that they even frequently switch between these within the course of a manoeuvre. We conclude that the bats used three main modes: lift asymmetries during downstroke, thrust/drag asymmetries during downstroke and thrust/drag asymmetries during upstroke. For future studies, we hypothesize that lift asymmetries are used for fast turns and thrust/drag for slow turns and that the choice between up- and downstroke depends on the timing of when the bat needs to generate asymmetries.

A Theoretical Investigation of the Maximum-lift Coefficient

1935 ◽  
Vol 39 (295) ◽  
pp. 619-632
Author(s):  
TH. Von karman ◽  
Clark B. Millikan
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Theoretical Investigation ◽  
Lift Coefficient ◽  
Wind Tunnels ◽  
California Institute ◽  
California Institute Of Technology ◽  
Junior Author ◽  
Institute Of Technology

The problem of the maximum lift of airfoils has concerned the authors greatly since there were first discovered in the spring of 1932 serious discrepancies in this characteristic between results obtained in the wind tunnel of the Guggenheim Aeronautics Laboratory at the California Institute of Technology (GALCIT) and those reported from certain other wind tunnels. An elaborate experimental investigation by the junior author and A. L. Klein indicated that the value of CLmax for a given airfoil was strongly affected both by Reynolds number and by the degree of turbulence in the tunnel wind stream.

scholarly journals Wind Tunnel testing of small Vertical-Axis Wind Turbines in Turbulent Flows

2017 ◽  
Vol 199 ◽  
pp. 3176-3181 ◽  
Author(s):  
Andreu Carbó Molina ◽  
Gianni Bartoli ◽  
Tim de Troyer
Keyword(s):  
Wind Tunnel ◽  
Turbulent Flows ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Wind Tunnel Testing ◽  
Vertical Axis Wind Turbines ◽  
Tunnel Testing

scholarly journals Experimental Investigation of a Prandtl Probe Fabricated Using Desktop Stereolithography Technology

2020 ◽  
Vol 5 (10) ◽  
pp. 1274-1280
Author(s):  
Alfred Gift Mwachugha ◽  
Jean Byiringiro ◽  
Harrison Ngetha ◽  
Thomas Carolus ◽  
Kathrin Stahl
Keyword(s):  
Additive Manufacturing ◽  
Wind Tunnel ◽  
Accurate Determination ◽  
Wind Tunnels ◽  
Research Institution ◽  
Flow Characterization ◽  
Desktop Manufacturing ◽  
Flow Quality ◽  
Manufacturing Platform

A Prandtl probe is one of the standard instruments used for flow characterization in wind tunnel facilities. The convectional fabrication method of this instrument requires skilled artisanship, precision drilling, lathing and soldering of its several parts. This reflects into high costs of production in turn making wind energy studies expensive. With the adoption of additive manufacturing, the tooling costs, skills required and design to manufacture constraints can be addressed. This research presents a Prandtl probe that was designed using NX™ software, fabricated by desktop stereolithography additive manufacturing platform and validated in a wind tunnel for velocity range of 0 m/s to 51 m/s. This research attested the option of fabricating relatively cheap functional Prandtl probe with desktop stereolithography technology which can be used for accurate determination of flow quality in wind tunnels experiments. This provides various learning and research institution in developing countries that have already invested in additive desktop manufacturing technology certainty and a cheaper option to fabricate wind research instruments for use at their laboratories. Moreover, fabrication and validation of a 5-hole Prandtl probe can also be examined.

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