Autorotating flat-plate wings: the effect of the moment of inertia, geometry and Reynolds number

1979 ◽  
Vol 92 (2) ◽  
pp. 327-348 ◽  
Author(s):  
J. D. Iversen
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Flat Plate ◽  
Plate Thickness ◽  
Thickness Ratio ◽  
Moment Of Inertia ◽  
Speed Ratio ◽  
Free Flight ◽  
Tip Speed Ratio ◽  
The Moment

Free-flight and wind-tunnel measurements by previous investigators of the flat-plate autorotation phenomenon have been analysed. The variation of the autorotation characteristics with changes in the Reynolds number and the aspect ratio, thickness ratio and moment of inertia of the flat plate have been correlated. The interpretation of the role of the Reynolds number made in a previous investigation is shown to be incorrect. The tip-speed ratio, for the ranges of the dimensionless parameters investigated, is shown to be a function of only the plate aspect ratio, thickness ratio, and also the moment of inertia if the latter is sufficiently small. The lift and drag coefficients, and therefore the free-flight glide angle, are shown to be functions of the tip-speed ratio, the aspect ratio and the Reynolds numbers based on the chord and plate thickness.

Performance Estimation of Axial Flow Turbines

1970 ◽  
Vol 185 (1) ◽  
pp. 407-424 ◽  
Author(s):  
H. R. M. Craig ◽  
H. J. A. Cox
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Axial Flow ◽  
Performance Estimation ◽  
Speed Ratio ◽  
Test Results ◽  
Wide Range ◽  
Relevant Variables

A comprehensive method of estimating the performance of axial flow steam and gas turbines is presented, based on analysis of linear cascade tests on blading, on a number of turbine test results, and on air tests of model casings. The validity of the use of such data is briefly considered. Data are presented to allow performance estimation of actual machines over a wide range of Reynolds number, Mach number, aspect ratio and other relevant variables. The use of the method in connection with three-dimensional methods of flow estimation is considered, and data presented showing encouraging agreement between estimates and available test results. Finally ‘carpets’ are presented showing the trends in efficiencies that are attainable in turbines designed over a wide range of loading, axial velocity/blade speed ratio, Reynolds number and aspect ratio.

Reynolds Number Effects on the Freewheeling Behavior of a High Solidity Vertical River Kinetic Turbine

2010 ◽  
Author(s):  
Amir Hossein Birjandi ◽  
Eric Bibeau
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Speed Ratio ◽  
Stream Velocity ◽  
Blade Profile ◽  
Low Reynolds Numbers ◽  
Tip Speed Ratio ◽  
Reynolds Number Effects ◽  
High Reynolds ◽  
The University

A four-bladed, squirrel-cage, and scaled vertical kinetic turbine was designed, instrumented and tested in the water tunnel facilities at the University of Manitoba. With a solidity of 1.3 and NACA0021 blade profile, the turbine is classified as a high solidity model. Results were obtained for conditions during freewheeling at various Reynolds numbers. In this study, the freewheeling tip speed ratio, which relates the ratio of maximum blade speed to the free stream velocity at no load, was divided into three regions based on the Reynolds number. At low Reynolds numbers, the tip speed ratio was lower than unity and blades were in a stall condition. At the end of the first region, there was a sharp increase of the tip speed ratio so the second region has a tip speed ratio significantly higher than unity. In this region, the tip speed ratio increases almost linearly with Reynolds number. At high Reynolds numbers, the tip speed ratio is almost independent of Reynolds number in the third region. It should be noted that the transition between these three regions is a function of the blade profile and solidity. However, the three-region behavior is applicable to turbines with different profiles and solidities.

Plate Shape Effect on the Performance of the Vertical Axis Auto Rotation Current Turbine (VAACT)

2014 ◽  
Author(s):  
Ali Bakhshandeh Rostami ◽  
Antonio Carlos Fernandes
Keyword(s):  
Flat Plate ◽  
High Efficiency ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Shape Effect ◽  
Tip Speed Ratio ◽  
Upper Limit ◽  
Plate Shape ◽  
Uniform Current ◽  
Current Turbine

The present paper explores experimentally the performance of two types of hinged plates which rotate about vertical axis when submitted to uniform current. A flat plate configuration and also a flapped plate (say, S shape) configuration have been investigated. The Vertical axis Auto rotation Current Turbine (VAACT) is one degree of freedom system (free to rotate in yaw direction). It is shown that a high efficiency for S shape type can be obtained of the order of 30 percent while flat blade type reaches approximately to 7 percent. Upper limit of tip speed ratio for flat blade type has been expanded approximately 0.9 whereas S shape approaches 1.3.

Friction Drag on Bladed Disks in Housings as a Function of Reynolds Number, Axial and Radial Clearance, and Blade Aspect Ratio and Solidity

1961 ◽  
Vol 83 (4) ◽  
pp. 719-723 ◽  
Author(s):  
Robert W. Mann ◽  
Charles H. Marston
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Rotating Disk ◽  
Radial Clearance ◽  
Disk Radius ◽  
Moment Coefficient ◽  
Aspect Ratios ◽  
Direct Measurements ◽  
Partial Admission ◽  
The Moment

Extra losses from partial admission operation of a gas turbine occur both in the nozzle flow arc and away from it. The latter have been related to the theory of fluid flow over a rotating disk expressing a dimensionless moment coefficient as a function of Reynolds number. By direct measurements of drag torque, the moment coefficient has been determined over a range of Reynolds number from 2.0 × 104 to 4.5 × 106 for several aspect ratios, axial and radial shroud clearances, and solidities. Losses increase with increasing aspect ratio. Small increases from minimum practical clearance have little effect, but blade pumping losses become severe at radial and axial clearances of the order of half the disk radius. Typical changes in solidity have only small effects on losses.

scholarly journals Investigation of a Morphing Wing Capable of Airfoil and Span Adjustment Using a Retractable Folding Mechanism

Aerospace ◽  
2019 ◽  
Vol 6 (8) ◽  
pp. 85
Author(s):  
Amit Geva ◽  
Haim Abramovich ◽  
Rimon Arieli
Keyword(s):  
Adverse Effect ◽  
Wind Tunnel ◽  
Aspect Ratio ◽  
Selection Process ◽  
Moment Of Inertia ◽  
Wind Tunnel Testing ◽  
Morphing Wing ◽  
Additional Weight ◽  
Opposite Process ◽  
The Moment

The presented aircraft is capable of alternating between two singular working points by folding the exterior surfaces of the wing underneath the interior surfaces. This allows for a significant change in wingspan, lift surfaces, aspect ratio and airfoil (camber and thickness). The motivation for this type of morphing is twofold: The increase in wingspan due to unfolding, results in an increased endurance of the aircraft, while the opposite process, which eliminates the camber of the airfoil and reduces the moment of inertia, is translated into improved manoeuvre capabilities. An analysis was performed to assess the additional endurance gained by the morphing capabilities, factoring in a spectrum of aircraft geometries and flight missions. It was concluded that this morphing concept can, in theory, improve the endurance up to 50% compared to the standard counterparts. The penalty due to the additional weight of the morphing mechanism was factored in, which had an adverse effect on the endurance improvement. The concept also calls for unique airfoil selection process. Selecting a proper airfoil for either working point, results in irregular airfoil geometry upon morphing. The two possibilities were subjected to analysis and wind tunnel testing.

Holes stabilize freely falling coins

2016 ◽  
Vol 801 ◽  
pp. 250-259 ◽  
Author(s):  
Lionel Vincent ◽  
W. Scott Shambaugh ◽  
Eva Kanso
Keyword(s):  
Reynolds Number ◽  
Vortex Ring ◽  
Free Fall ◽  
Outer Edge ◽  
Moment Of Inertia ◽  
Outer Diameter ◽  
Hole Size ◽  
Fluid Medium ◽  
Designed Experiment ◽  
The Moment

The free fall of heavy bodies in a viscous fluid medium is a problem of interest to many engineering and scientific disciplines, including the study of unpowered flight and seed dispersal. The falling behaviour of coins and thin discs in particular has been categorized into one of four distinct modes; steady, fluttering, chaotic or tumbling, depending on the moment of inertia and Reynolds number. This paper investigates, through a carefully designed experiment, the falling dynamics of thin discs with central holes. The effects of the central hole on the disc’s motion is characterized for a range of Reynolds number, moments of inertia and inner to outer diameter ratio. By increasing this ratio, that is, the hole size, the disc is found to transition from tumbling to chaotic then fluttering at values of the moment of inertia not predicted by the falling modes of whole discs. This transition from tumbling to fluttering with increased hole size is viewed as a stabilization process. Flow visualization of the wake behind annular discs shows the presence of a vortex ring at the disc’s outer edge, as in the case of whole discs, and an additional counter-rotating vortex ring at the disc’s inner edge. The inner vortex ring is responsible for stabilizing the disc’s falling motion. These findings have significant implications on the development of design principles for engineered robotic systems in free flight, and may shed light on the stability of gliding animals.

scholarly journals A COMPARETIVE ANALYSIS OF AERODYNAMIC CHARECTERISTICS OF A VERTICAL AXIS VANE TYPE WIND TURBINE OVER EVEN AND ODD NUMBER OF BLADES

2015 ◽  
Vol 45 (1) ◽  
pp. 14-18
Author(s):  
Zulfa Ferdous ◽  
Md. Quamrul Islam ◽  
M Ali
Keyword(s):  
Reynolds Number ◽  
Dynamic Condition ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Subsonic Wind Tunnel ◽  
Aerodynamic Properties ◽  
Wide Range ◽  
Set Up

This paper reports on the experimental investigation of the aerodynamic effects on even and odd number bladed vertical axis vane type rotor. The experiment was conducted with the help of a subsonic wind tunnel together with the experimental set-up of the vane type rotor and a spring balance. To ensure a Reynolds number independent approach, different stream flow was maintained. The flow velocities varied from 5 m/s to 9 m/s covering the Reynolds number from 0.6375 X 10^5 to 1.2 X 10^5. A four, five and six bladed vertical axis vane typerotor was used to determine the aerodynamic properties in dynamic condition. It is found that the power coefficient increases with increasing the number of blade but the significant effect of even and odd number blade is observed on the range of tip speed ratio. An odd number bladed rotor covered a wide range of tip speed ratio compare to the even number one.

Dynamic Stall: The Case of the Vertical Axis Wind Turbine

1986 ◽  
Vol 108 (2) ◽  
pp. 140-145 ◽  
Author(s):  
A. Laneville ◽  
P. Vittecoq
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Leading Edge ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Airfoil Surface ◽  
Helicopter Blade ◽  
Tip Speed Ratio

This paper presents the results of an experimental investigation on a driven Darrieus turbine rotating at different tip speed ratios. For a Reynolds number of 3.8 × 104, the results indicate the presence of dynamic stall at tip speed ratio less than 4, and that helicopter blade aerodynamics can be used in order to explain some aspects of the phenomenon. It was observed that in deep stall conditions, a vortex is formed at the leading edge; this vortex moves over the airfoil surface with 1/3 of the airfoil speed and then is shed at the trailing edge. After its shedding, the vortex can interact with the airfoil surface as the blade passes downstream.

scholarly journals STATORS USE INFLUENCE ON THE PERFORMANCE OF A SAVONIUS WIND ROTOR USING COMPUTATIONAL FLUID DYNAMICS

2011 ◽  
Vol 10 (1-2) ◽  
pp. 63
Author(s):  
J. V. Akwa ◽  
A. P. Petry
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Cylindrical Shape ◽  
Tip Speed Ratio ◽  
Eddy Viscosity Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Moment ◽  
Volume Method

This paper aims at verifying the influence of using five kinds of stators in the averaged moment and power coefficients of a Savonius wind rotor using computational fluid dynamics (CFD). The analyzed stators have cylindrical shape with two and three openings, one and four deflector blades and walls shaped like a wings. The equations of continuity, Reynolds Averaged Navier-Stokes – RANS and the Eddy Viscosity Model k-ω SST, in its Low-Reynolds approaches, with hybrid near wall treatment; are numerically solved using the commercial software Star-CCM+, based on Finite Volume Method, resulting in the fields of pressure and velocity of the flow and the forces acting on the rotor buckets. The moment and power coefficients are achieved through integration of forces coming from the effects of pressure and viscosity of the wind on the buckets device. The influence of the stators use in the moment and power coefficients is checked by changing the geometry of the device for each simulations series, keeping the Reynolds number based on rotor diameter equal to 433,500. The obtained values for averaged moment and power coefficients indicate that for each type of stator used, there was maximum performance for a given tip speed ratio of rotor. Improvement in performance over the operation without stator was obtained only to the operations using stator with four deflector blades and to the stator with cylindrical shape with three openings. The improvement percentage in performance obtained for the best condition (use of four deflector blades at tip speed ratio equal to 1) is 12% compared to the performance of the rotor operating without stator.

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