An Acoustic Procedure for Measuring Blade-Frequency Forces Generated by Model Ship Propellers

2001 ◽  
Author(s):  
M. Strasberg
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Test Section ◽  
Sound Pressure ◽  
Water Tunnel ◽  
Measurement Point ◽  
Theoretical Relation ◽  
Point Measurement ◽  
Direct Measurements ◽  
Blade Frequency

Abstract An acoustic procedure is described for measuring the blade-frequency fluctuating forces developed by a powered model propeller operating behind a model of a ship’s hull or a wake generator in the anechoic test section of a wind tunnel. The sound pressure radiated by the propeller in a given direction is measured and its magnitude inserted into a simple theoretical relation to determine the alternating force developed by the propeller in that direction. Although the procedure was developed years ago, the details and limitations have not previously been described in the literature. Restrictions are discussed on the size of the propeller, location of the measurement point, measurement frequency, and the wind speed. Measurements determining the validity of the procedure are described, including comparisons of the magnitude of forces determined by this acoustic procedure with direct measurements made with a force dynamometer in a water tunnel.

A new low-turbulence wind tunnel for bird flight experiments at Lund University, Sweden

1997 ◽  
Vol 200 (10) ◽  
pp. 1441-1449 ◽  
Author(s):  
C J Pennycuick ◽  
T Alerstam ◽  
A Hedenström
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Test Section ◽  
Safety Net ◽  
Turbulence Level ◽  
Bird Flight ◽  
Contraction Ratio ◽  
Unrestricted Access ◽  
Side Walls ◽  
Air Speed

A new wind tunnel for experiments on bird flight was completed at Lund University, Sweden, in September 1994. It is a closed-circuit design, with a settling section containing five screens and a contraction ratio of 12.25. The test section is octagonal, 1.20 m wide by 1.08 m high. The first 1.2 m of its length is enclosed by acrylic walls, and the last 0.5 m is open, giving unrestricted access. Experiments can be carried out in both the open and closed parts, and comparison between them can potentially be used to measure the lift effect correction. The fan is driven by an a.c. motor with a variable-frequency power supply, allowing the wind speed to be varied continuously from 0 to 38 m s-1. The whole machine can be tilted to give up to 8 ° descent and 6 ° climb. A pitot-static survey in the test section showed that the air speed was within ±1.3 % of the mean at 116 out of 119 sample points, exceeding this deviation at only three points at the edges. A hot-wire anemometer survey showed that the turbulence level in the closed part of the test section was below 0.04 % of the wind speed throughout most of the closed part of the test section, rising to approximately 0.06 % in the middle of the open part. No residual rotation from the fan could be detected in the test section. No decrease in wind speed was detectable beyond 3 cm from the side walls of the closed part, and turbulence was minimal beyond 10 cm from the walls. The installation of a safety net at the entrance to the test section increased the turbulence level by a factor of at least 30, to 1.2 % longitudinally and 1.0 % transversely.

scholarly journals Optimizing the Coupling of a Firebrand Generator to a Horizontal Wind Tunnel

2013 ◽  
Vol 726-731 ◽  
pp. 971-976
Author(s):  
Javad Hashempour ◽  
Ahmad Sharifian
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Test Section ◽  
Experimental Studies ◽  
Fire Spread ◽  
Horizontal Wind ◽  
Experimental Facility ◽  
Velocity Difference ◽  
Wind Speeds ◽  
Computational Work

Australia is considered as the most fire-prone country in the world. Spotting ignition by lofted firebrands is the main mechanism of fire spread. Many experimental studies have been conducted to evaluate the effect of the firebrand attacks on structures and to identify possible solutions. The experimental facility consists of a firebrand generator coupled to a wind tunnel. The wind speed in the firebrand generator is relatively low, in order to assure a quality continuous flow of glowing firebrands. On the contrary, the wind speed in the wind tunnel is high to duplicate actual firebrand attacks. Previous works show a highly turbulent region above the entrance of firebrands to the wind tunnel which is formed because of the velocity difference and penetration of firebrand entrance hose into the wind tunnel. The penetration is required to provide a uniform firebrand distribution along the height of the test section. In this computational work, the influence of the height of the entrance hose, its orientation respect to the tunnel and the distance between the coupling port and the test section are analyzed. The optimized results are presented and discussed for a variety of wind speeds within the wind tunnel and the firebrand generator.

Experimental Analysis of a Counter-Rotating Wind Turbine

2009 ◽  
Author(s):  
Jason R. Gregg ◽  
J. Shane Merchant ◽  
Kenneth W. Van Treuren ◽  
Ian A. Gravagne
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Optimum Operating ◽  
Operating Efficiency ◽  
Water Tunnel ◽  
Total System ◽  
Wind Tunnel Testing ◽  
Air Column ◽  
Tunnel Testing

Increases in wind turbine efficiency have helped to provide cost-effective power to an ever-growing portion of the world. This paper explores the possibility of increasing power production using two counter-rotating sets of wind turbine blades. A review of design characteristics, such as number of blades, blade angle of twist, chord length, and generator efficiencies, resulted in the design of a counter-rotating wind turbine incorporating three different National Renewable Energy Laboratory (NREL) cross-sectional blade profiles along the span of the blades. A three-blade front system and two different three-blade rear systems were studied. The blade prototypes were modeled in SolidWorks®, produced using a Dimension SST 3D printer, and then tested using two Parallax™ four-pole stepper motors as generators in a model 406B ELD wind tunnel. Testing was performed between 15 mph and 40 mph in 5-mph increments. Preliminary results indicate that a counter-rotating assembly is promising for increasing energy extraction from a column of air. The counter-rotating system reached its optimum operating efficiency in wind tunnel testing at 25 mph using an exact reflection for the rear fan. At these test conditions 0.40% of the energy in the air column was converted into usable power. This outcome compares to a 0.21% power conversion when testing only the front-blade system. Additional testing will be completed using flow visualization in a ELD 502 water tunnel along with CFD analysis. The purpose of this testing is to discover air column behavior behind the upstream and downstream blade systems to optimize the design and increase total system efficiency. An appropriate scaling method must also be found. Currently, an energy model is being used to scale from the wind tunnel to the water tunnel. These tests would make it possible to design blade sets to create a maximum total efficiency at a specific wind speed. It would also be valuable to determine if counter-rotating systems could expand the range of possible turbine locations by lowering the required wind speed for significant power generation.

Experimental Results of a Vertical Axis Wind Turbine

2010 ◽  
Author(s):  
Bernardo Fortunato ◽  
Sergio Mario Camporeale ◽  
Marco Torresi ◽  
Davide De Fazio ◽  
Mauro Giordani
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Personal Computer ◽  
Test Section ◽  
Fluid Dynamic ◽  
Vertical Axis ◽  
Hot Wire ◽  
Vertical Axis Wind Turbine ◽  
Wire Probe ◽  
Set Up

In the present paper the new wind tunnel located in the Fluid-dynamic Laboratory of the Dipartimento di Ingegneria Meccanica e Gestionale (DIMeG) of the Bari Polytechnic will be shortly described and the first experimental measurements on a vertical axis wind turbine (VAWT) will be shown. The DIMeG wind tunnel has been designed by the research group on wind energy of the Department. It is a subsonic, closed loop, wind tunnel with a transparent test part where small scale models can be analyzed. A four bladed axial fan is driven by an asynchronous three phase electric motor, which is connected to an inverter in order to change the wind speed. Angular blades have been inserted at the two curves between the fan and the test section in order to increase the uniformity of the velocity profile after the two curves. An optimization fluid-dynamic study has been carried out in order to find the best blade profile. A honeycomb has been also inserted upstream the test section in order to destroy the still existing small vorticity generated by the fan and the curves. A three-axis traversing, called Cartesian robot, has been designed and built above the test section, in order to move the hot wire probe, for wind speed measurements, by means of four step by step electric motors controlled by a personal computer. A data acquisition system has been set up. All the principal commands and controls can be performed by a dedicated personal computer, which has been programmed using LabVIEW® G-programming language. The first experimental activity has been performed on a VAWT model, of the Giromill type with parallel blades. The turbine has been connected to an AC brushless servo, able to control the braking torque. Experimental results of the flow field in two horizontal planes have been set up using a two component hot wire probe (Dantec 55R51) calibrated with the manual system Dantec 54H10. The measurement grid adopted is formed by 20 nodes in the Y direction (main flow direction) and 10 nodes in the X direction.

Extremely Gusty Winds from a Viewpoint of Aerodynamic Force

2020 ◽  
Author(s):  
Junji Maeda ◽  
Takashi Takeuchi ◽  
Eriko Tomokiyo ◽  
Yukio Tamura
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Rise Time ◽  
Aerodynamic Force ◽  
Step Function ◽  
Object Size ◽  
Aerodynamic Forces ◽  
Wind Force ◽  
Wind Observation

To quantitatively investigate a gusty wind from the viewpoint of aerodynamic forces, a wind tunnel that can control the rise time of a step-function-like gust was devised and utilized. When the non-dimensional rise time, which is calculated using the rise time of the gusty wind, the wind speed, and the size of an object, is less than a certain value, the wind force is greater than under the corresponding steady wind. Therefore, this wind force is called the “overshoot wind force” for objects the size of orbital vehicles in an actual wind observation. The finding of the overshoot wind force requires a condition of the wind speed recording specification and depends on the object size and the gusty wind speed.

Instability in slotted wall tunnels

1958 ◽  
Vol 4 (3) ◽  
pp. 283-305 ◽  
Author(s):  
J. L. King ◽  
P. Boyle ◽  
J. B. Ogle
Keyword(s):  
Wind Tunnel ◽  
Experimental Evidence ◽  
Theoretical Explanation ◽  
Water Tunnel ◽  
Design Consideration ◽  
Working Section

A new water tunnel, incorporating a slotted wall working section, was found to suffer from severe vibration. A theoretical explanation is given for this, together with experimental evidence gleaned from this water tunnel and a small wind tunnel. It is shown that the oscillations are hydrodynamic in origin and are associated with the slotted wall design. Consideration is given to methods of elimination or reduction of the oscillations.

Study on the Relation Between Side Ratios of Rectangular Cross Sections and Secondary Vortices at Trailing Edge in Motion-Induced Vortex Excitation

2017 ◽  
Author(s):  
Kazutoshi Matsuda ◽  
Kusuo Kato ◽  
Kouki Arise ◽  
Hajime Ishii
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Cross Sections ◽  
Leading Edge ◽  
Trailing Edge ◽  
Wind Speeds ◽  
Smoke Flow ◽  
Flow Visualizations ◽  
Institute Of Technology ◽  
Secondary Vortices

According to the results of conventional wind tunnel tests on rectangular cross sections with side ratios of B/D = 2–8 (B: along-wind length (m), D: cross-wind length (m)), motion-induced vortex excitation was confirmed. The generation of motion-induced vortex excitation is considered to be caused by the unification of separated vortices from the leading edge and secondary vortices at the trailing edge [1]. Spring-supported test for B/D = 1.18 was conducted in a closed circuit wind tunnel (cross section: 1.8 m high×0.9 m wide) at Kyushu Institute of Technology. Vibrations were confirmed in the neighborhoods of reduced wind speeds Vr = V/fD = 2 and Vr = 8 (V: wind speed (m/s), f: natural frequency (Hz)). Because the reduced wind speed in motion-induced vortex excitation is calculated as Vr = 1.67×B/D = 1.67×1.18 = 2.0 [1], vibrations around Vr = 2 were considered to be motion-induced vortex excitation. According to the smoke flow visualization result for B/D = 1.18 which was carried out by the authors, no secondary vortices at the trailing edge were formed, although separated vortices from the leading edge were formed at the time of oscillation at the onset wind speed of motion-induced vortex excitation, where aerodynamic vibrations considered to be motion-induced vortex excitation were confirmed. It was suggested that motion-induced vortex excitation might possibly occur in the range of low wind speeds, even in the case of side ratios where secondary vortices at trailing edge were not confirmed. In this study, smoke flow visualizations were performed for ratios of B/D = 0.5–2.0 in order to find out the relation between side ratios of rectangular cross sections and secondary vortices at trailing edge in motion-induced vortex excitation. The smoke flow visualizations around the model during oscillating condition were conducted in a small-sized wind tunnel at Kyushu Institute of Technology. Experimental Reynolds number was Re = VD/v = 1.6×103. For the forced-oscillating amplitude η, the non-dimensional double amplitudes were set as 2η/D = 0.02–0.15. Spring-supported tests were also carried out in order to obtain the response characteristics of the models.

Characterization of the Custom-Designed, High Reynolds Number Water Tunnel

2016 ◽  
Author(s):  
Yasaman Farsiani ◽  
Brian R. Elbing
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Test Section ◽  
High Reynolds Number ◽  
Layer Growth ◽  
Water Tunnel ◽  
Freestream Velocity ◽  
Section Design ◽  
High Reynolds

This paper reports on the characterization of the custom-designed high-Reynolds number recirculating water tunnel located at Oklahoma State University. The characterization includes the verification of the test section design, pump calibration and the velocity distribution within the test section. This includes an assessment of the boundary layer growth within the test section. The tunnel was designed to achieve a downstream distance based Reynolds number of 10 million, provide optical access for flow visualization and minimize inlet flow non-uniformity. The test section is 1 m long with 15.2 cm (6-inch) square cross section and acrylic walls to allow direct line of sight at the tunnel walls. The verification of the test section design was accomplished by comparing the flow quality at different location downstream of the flow inlet. The pump was calibrated with the freestream velocity with three pump frequencies and velocity profiles were measured at defined locations for three pump speeds. Boundary layer thicknesses were measured from velocity profile results and compared with analytical calculations. These measurements were also compared against the facility design calculations.

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