A Simple Device for Wind Tunnel Performance Testing of Small Scale Powered Propellers

2005 ◽  
Author(s):  
B. Terry Beck ◽  
Nelson A. Pratt
Keyword(s):  
Wind Tunnel ◽  
Rotation Speed ◽  
Force Measurement ◽  
Performance Testing ◽  
Test Facility ◽  
Wind Tunnels ◽  
Small Scale ◽  
Torque Measurement ◽  
Measurement Device ◽  
Propeller Design

Propellers represent an interesting application of the principles of aerodynamics. The basic physics of propeller operation can be modeled as a rotating wing section using classical blade element analysis procedure, which can also include flows induced by the propeller motion itself. Performance testing of small-scale powered propellers in modest size educational wind tunnels could yield important verification of these analysis tools, and also provide valuable experimental insight into important aspects of propeller design for the engineering laboratory. To provide useful data, measurements of propeller performance must include not only rotation speed and thrust, but also torque. These variables need to be investigated as a function of the imposed wind tunnel airspeed, which represents the forward speed of a powered propeller in flight. Rotation speed is easily measured using a variety of simple optical (including stroboscopic) techniques and thrust simply corresponds to the axial force measurement obtained directly from the typical “sting” balance used with educational wind tunnels. However, commercial devices for practical torque measurement can be quite expensive and are also typically of much higher torque range than that achieved by small-scale propellers designed for model airplane use, which limits their usefulness in the educational engineering wind tunnel laboratory. This paper presents a simple and inexpensive strain gage based device designed for measurement of low level torque developed by small-scale powered propellers. The operating principles of the torque measurement device are described, along with static calibration test results and experimental measurements of the performance characteristics of a small-scale electric motor driven powered propeller using our educational wind tunnel test facility. The torque sensor can be combined with rapid prototyping propeller design to allow investigation of a wide variety of propeller design features. Additional planned improvements and other wind tunnel applications for the torque measurement device are also discussed in the paper.

Numerical and Experimental Study of Turbulent Flows Around Clark Y-14 Aerofoil

2015 ◽  
Author(s):  
Kshitij Vadake ◽  
Jie Cui
Keyword(s):  
Fluid Dynamics ◽  
Wind Tunnel ◽  
Real World ◽  
Force Measurement ◽  
Test Model ◽  
Wind Tunnel Testing ◽  
Cfd Simulations ◽  
Measurement Device ◽  
Tunnel Testing

Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD) have been instrumental in Fluid Mechanics to help solve scientific and engineering problems. This research attempts to use both techniques to perform a parametric study of turbulence flow around airfoil ClarkY-14 at various velocity and angle of attack (AoA). Clark Y-14 airfoil was designed in the 1920’s. It demonstrated good overall performance at low and moderate Reynolds numbers. With the progress in the aviation field, its performance was sub-optimal for newer aircraft designs. However, with the advent of RC airplanes and model aircrafts, there is a renewed interest in this airfoil. Various research projects have been conducted using this airfoil, but there hasn’t been a combined EFD and CFD study of the performance characteristics of the airfoil itself, which still finds real world applications today. One important aspect of this research included the investigation of the effects of a Force Measurement Device/Sensor, which is typically used in scaled/full-size wind tunnels to mount the test model as well as measure the forces/moments acting on it during the testing. The presence of such a device could affect the quality of the data obtained from the wind tunnel testing when compared to a real world application scenario where the aforementioned device may not be present. To the best of the author’s knowledge, no detailed study has been published on the effects of such devices. In this study, the results with and without the measuring device were generated by using CFD simulations. The results were then compared to see to what extent the inclusion of these devices will affect the results. The methodology used for this research was experimental as well as computational. In the present research, a commercially available CFD software STAR-CCM+ was employed to simulate the flows around airfoil Clark Y-14. The experimental data was obtained from wind tunnel tests using AEROLAB Educational Wind Tunnel (EWT) and compared with the simulation data from the CFD. The two data sets were in good agreement. Both experimental and simulation results were used to understand the effects of the measurement device/sensor used in the scaled wind tunnel on the lift and drag coefficients of the airfoil. Two separate CFD simulation setups were designed to model the presence and absence of the measurement device/sensor. These setups replicated the wind tunnel setup. The airfoil was tested and simulated at different speeds as well as different AoA. The comparative study gave a useful insight on the accuracy of the CFD simulations in relation to the actual testing. The analysis of results concluded that the force measurement device/sensor had insignificant effects on the accuracy and quality of data collected through wind tunnel testing.

scholarly journals Validation of CFD Predictions of Urban Wind - Developing a Methodology

2021 ◽  
Author(s):  
◽  
Riley Willis
Keyword(s):  
Wind Tunnel ◽  
City Council ◽  
Wind Tunnels ◽  
Small Scale ◽  
Cfd Model ◽  
Validation Process ◽  
Cfd Simulations ◽  
Entire Area ◽  
Cfd Models ◽  
Wind Tunnel Measurements

<p>“Good mental health in a fluid or CFD modeller is always indicated by the presence of a suspicious nature, cynicism and a ‘show me’ attitude. These are not necessarily the best traits for a life mate or a best friend, but they are essential if the integrity of the modelling process is to be maintained.” (Meroney, 2004)  Over the past 50 years, Computational Fluid Dynamics (CFD) computer simulation programs have offered a new method of calculating the wind comfort and safety data for use in pedestrian wind studies. CFD models claim to have some important advantages over wind tunnels; which remain the most common method of wind calculation. While wind tunnels provide measurements of selected points, CFD simulations provide whole-flow field data for the entire area under investigation (Blocken, 2014; Blocken, Stathopoulos, & van Beeck, 2016). Similarly, wind tunnel measurements must consider the similarity requirements involved with testing a model at small scale, while CFD simulations can avoid this as they are conducted at full scale (Ramponi & Blocken, 2012a).  However, CFD simulations can also often be misleading; and they should only be trusted once they can be proven to be accurate. To appease the requirements for this cynical view- referenced in the above quote- proper verification and validation of a model is imperative.  This thesis investigated and tested the current best practice guidelines around CFD model validation, using existing wind tunnel measurements of generic urban arrays. The goal of the research was to determine whether the existing data and guidance around the validation process was sufficient for a consultant user to trust that a CFD model they created was sufficiently accurate to base design decisions from.  The CFD code Autodesk CFD was used to simulate two configurations first tested as wind tunnel models by the Architectural Institute of Japan, and Opus labs in Wellington. The Wellington City Council wind speed criteria were used to determine whether the CFD simulations met the required accuracy criteria for council consent.  Results from the study found that the CFD models could not meet the accuracy criteria. It concluded that while the validation process provided sufficient guidance, there is a lack of available data which is relevant to CFD validation for urban flows.  It was recommended that at least one improved dataset was required, to build a system by which a consultant can identify what the requirements of a CFD model are to provide accurate CFD analysis of the site under investigation. To accommodate the range of sites likely to be present in urban wind studies, it was recommended that the new dataset provided data for a variety of wind flows likely to be found in cities.</p>

scholarly journals Demonstration and uncertainty analysis of synchronised scanning lidar measurements of 2-D velocity fields in a boundary-layer wind tunnel

2017 ◽  
Vol 2 (1) ◽  
pp. 329-341 ◽  
Author(s):  
Marijn Floris van Dooren ◽  
Filippo Campagnolo ◽  
Mikael Sjöholm ◽  
Nikolas Angelou ◽  
Torben Mikkelsen ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Uncertainty Analysis ◽  
Wind Turbine ◽  
Short Range ◽  
Goodness Of Fit ◽  
Wind Tunnels ◽  
Small Scale ◽  
Measurement Technology ◽  
Lidar Measurement ◽  
Hot Wire

Abstract. This paper combines the research methodologies of scaled wind turbine model experiments in wind tunnels with short-range WindScanner lidar measurement technology. The wind tunnel at the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner lidars to demonstrate the benefits of synchronised scanning lidars in such experimental surroundings for the first time. The dual-lidar system can provide fully synchronised trajectory scans with sampling timescales ranging from seconds to minutes. First, staring mode measurements were compared to hot-wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u and v components of the wind speed, respectively, validating the 2-D measurement capability of the lidar scanners. Subsequently, the measurement of wake profiles on a line as well as wake area scans were executed to illustrate the applicability of lidar scanning to the measurement of small-scale wind flow effects. An extensive uncertainty analysis was executed to assess the accuracy of the method. The downsides of lidar with respect to the hot-wire probes are the larger measurement probe volume, which compromises the ability to measure turbulence, and the possible loss of a small part of the measurements due to hard target beam reflection. In contrast, the benefits are the high flexibility in conducting both point measurements and area scanning and the fact that remote sensing techniques do not disturb the flow during measuring. The research campaign revealed a high potential for using short-range synchronised scanning lidars to measure the flow around wind turbines in a wind tunnel and increased the knowledge about the corresponding uncertainties.

Turbulence reduction by screens

1988 ◽  
Vol 197 ◽  
pp. 139-155 ◽  
Author(s):  
Johan Groth ◽  
Arne V. Johansson
Keyword(s):  
Wind Tunnel ◽  
Reynolds Numbers ◽  
Wind Tunnels ◽  
Small Scale ◽  
Flow Conditions ◽  
Upstream Side ◽  
Turbulence Suppression ◽  
Controlled Flow ◽  
Reduction Effectiveness

Turbulence suppression by use of screens was studied in a small wind tunnel especially designed and built for the purpose. Wide ranges of mesh sizes and wire-diameter Reynolds numbers were covered in the present investigation, enabling the study of sub- and super-critical screens under the same, well-controlled, flow conditions. For the latter type small-scale fluctuations, produced by the screen itself, interact with the incoming turbulence. In the immediate vicinity of the screen the turbulence was found to be highly anisotropic and the intensities were higher than on the upstream side. Downstream of a short initial decay region, where the intensities decrease rapidly, the return to isotropy was found to be much slower than for the unmanipulated turbulence. The latter was generated by a square rod grid, and was shown to become practically isotropic beyond a distance of roughly 20 mesh widths from the grid. The role of the turbulence scales for the overall reduction effectiveness, and for the optimization of screen combinations for application in low-turbulence wind tunnels was studied.

A Modular Wing-Tail Airplane Configuration for the Educational Wind Tunnel Laboratory

2004 ◽  
Author(s):  
B. Terry Beck
Keyword(s):  
Wind Tunnel ◽  
Rapid Prototyping ◽  
Calibration Procedure ◽  
Aerodynamic Characteristics ◽  
Wind Tunnels ◽  
Small Scale ◽  
Pitching Moment ◽  
Gravity Effects ◽  
Basic Parameters ◽  
Rapid Prototyping System

An innovative modular airplane configuration has been developed for use in small-scale educational wind tunnels. The “airplane” consists of an interchangeable wing and horizontal tail configuration that mounts on a conventional wind tunnel electronic balance (“sting”) to facilitate measurements of normal force, axial force and longitudinal pitching moment. From these basic parameters, the total lift, total drag, and resultant airplane pitching moment can be deduced, along with the location of the aerodynamic center of the total airplane. Using known wing planform and airfoil shapes facilitates comparison of the total airplane aerodynamic characteristics with those predicted from the known characteristics of the separate wing and horizontal tail. In particular, the aerodynamic center of the simplified airplane configuration can be determined, along with the effect that downwash on the tail has on longitudinal stability of the airplane. Included in the paper is a description of the calibration procedure for the modular “sting” mount. This procedure accounts for an offset “line of action” for aerodynamic forces, as well as offset center of gravity effects. In conjunction with this same test setup, an available Rapid Prototyping system has been used to manufacture the test sections (separate wing and tail) for use in the wind tunnel, and in particular, in the modular wing-tail assembly. This provides tremendous flexibility in the types of wing-tail assemblies that can be investigated experimentally using the same module. The relatively inexpensive prototyping procedure also provides the capability for students to design and test their own configurations. Furthermore, the precision manufacturing capability of the Rapid Prototyping system guarantees reliable reproduction of virtually any desired aerodynamic planform and airfoil shape.

scholarly journals Demonstration and uncertainty analysis of synchronised scanning lidar measurements of 2D velocity fields in a boundary-layer wind tunnel

2017 ◽  
Author(s):  
Marijn F. van Dooren ◽  
Filippo Campagnolo ◽  
Mikael Sjöholm ◽  
Nikolas Angelou ◽  
Torben Mikkelsen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Wind Tunnel ◽  
Uncertainty Analysis ◽  
Wind Turbine ◽  
Short Range ◽  
Goodness Of Fit ◽  
Wind Tunnels ◽  
Small Scale ◽  
Lidar Measurement ◽  
Hot Wire

Abstract. This paper combines the currently relevant research methodologies of scaled wind turbine model experiments in wind tunnels with remote-sensing short-range WindScanner lidar measurement technology. The wind tunnel of the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner lidars to demonstrate the benefits of synchronised scanning lidars in such experimental surroundings for the first time. The dual-lidar system can provide fully synchronised trajectory scans with sampling time scales ranging from seconds to minutes. First, staring mode measurements were compared to hot-wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u- and v-components of the wind speed, respectively, validating the 2D measurement capability of the lidar scanners. Subsequently, the measurement of wake profiles on a line as well as wake area scans were executed to illustrate the applicability of lidar scanning to measuring small scale wind flow effects. An extensive uncertainty analysis was executed to assess the accuracy of the method. The downsides of lidar with respect to the hot-wire probes are the larger measurement probe volume and the loss of some measurements due to moving blades. In contrast, the benefits are the high flexibility in conducting both point measurements and area scanning, and the fact that remote sensing techniques do not disturb the flow while measuring. The research campaign revealed a high potential for using short-range synchronised scanning lidars to accurately measure small scale flow structures in a wind tunnel, and increased the knowledge about the corresponding uncertainties.

Transient Performance of Fixed-Bed Regenerators for Energy Recovery in Building Applications

2020 ◽  
Author(s):  
Hadi Ramin ◽  
Easwaran N. Krishnan ◽  
Gurubalan Annadurai ◽  
Carey J. Simonson
Keyword(s):  
Steady State ◽  
Fixed Bed ◽  
Performance Testing ◽  
State Condition ◽  
Test Facility ◽  
Small Scale ◽  
Outlet Temperature ◽  
Quasi Steady State ◽  
Steady State Condition ◽  
Steady State Operation

Abstract A small-scale test facility is developed to determine the sensible effectiveness of a Fixed-Bed Regenerator (FBR) and the results are used to validate a numerical model. The numerical and experimental results for quasi-steady-state conditions are in a good agreement within the experimental uncertainty bounds. At quasi-steady-state condition, the outlet temperature of FBR varies with time but cyclically repeats itself; this is an important difference between FBR (regenerator) and recuperator heat exchangers. The outlet temperature of recuperator heat exchangers reaches a constant value during the steady-state operation. The quasi-steady-state temperature profile is used to determine the sensible effectiveness of FBRs. However, FBRs undergo several cycles to reach the quasi-steady-state condition. The prediction of the duration of the transient duration of FBR is important for performance testing that could save money and time. CSA (Canadian Standards Association) recommends operating FBR for at least one hour to achieve a quasi-steady-state condition. This paper addresses the heat transfer behavior of FBRs during their transient operation. The initial transient cycles depend on the cycle period of FBR, air flow rate and the thermal condition of the exchanger at the beginning of the test. The small-scale FBR test facility is used to study the transient behavior of FBRs and this is the main focus of this paper. The temperature profile during the transient condition of FBR is obtained and the results are compared with the numerical model. The effects of the mass flow rate of air and the cycle duration on the transient period of FBR are studied. The results show that FBR reaches a quasi-steady state operation in less than 30 minutes. The results will be useful for understanding the time required for performance testing, which will reduce the cost and time of each test.

scholarly journals Aerofoil behaviour at high angles of attack and at Reynolds numbers appropriate for small wind turbines

2014 ◽  
Vol 229 (11) ◽  
pp. 2007-2022 ◽  
Author(s):  
Longhuan Du ◽  
Arganthaël Berson ◽  
Robert G Dominy
Keyword(s):  
Wind Tunnel ◽  
Turbine Blades ◽  
Sudden Change ◽  
Reynolds Numbers ◽  
Surface Flow ◽  
Wind Tunnels ◽  
Small Scale ◽  
Flow Visualisation ◽  
Data Set ◽  
High Angles Of Attack

The aerodynamic characteristics of a NACA0018 aerofoil have been investigated experimentally for incidence angles ranging from [Formula: see text] to [Formula: see text] in closed-jet and open-jet wind tunnels with different blockage coefficients at Reynolds numbers from 60,000 to 140,000. The results provide a comprehensive data set for studying the performance of typical, small-scale Darrieus wind turbine blades which mainly operate at relatively low Reynolds number and experience extreme angles of attack, particularly during start-up. Measurements in both very high and very low blockage, open-jet wind tunnels capture a “second-stall” phenomenon at high angles of attack, but this behaviour is not observed in the closed-jet wind tunnel confirming the sensitivity of aerofoil performance at extreme incidence to wind tunnel configuration. Surface flow visualisation suggests that the “second-stall” occurs when the flow separation point near the leading edge of the aerofoil moves from the suction side to the pressure side which leads to a sudden change of wake structure. In the closed-jet wind tunnel, the tunnel walls constrain the wake and prevent the flow from switching from one regime to another. The measured data are also used to demonstrate that established wind tunnel blockage corrections break down under these extreme, post-stall angles of attack.

scholarly journals Impact of the oasis effect on wind tunnel measurements of ammonia volatilization from urea

2016 ◽  
Vol 96 (4) ◽  
pp. 485-495 ◽  
Author(s):  
Devon Watt ◽  
Philippe Rochette ◽  
Andrew VanderZaag ◽  
Ian B. Strachan ◽  
Normand Bertrand
Keyword(s):  
Wind Tunnel ◽  
Ammonia Volatilization ◽  
Wind Tunnels ◽  
Small Scale ◽  
Nonlinear Relationship ◽  
Concentration Gradients ◽  
Concentration Difference ◽  
Wind Tunnel Measurements ◽  
Flux Difference ◽  
Oasis Effect

The validity of emission factors derived from small-scale measurements of ammonia (NH3) volatilization has been questioned in the literature because gaseous NH3 concentration gradients differ at the edge of the measurement plot and may result in higher emissions than at field scale. We studied this “oasis effect” using two very long (22 m) wind tunnels constructed indoors over soil plots fertilized with surface-applied urea (20 g N m−2). We hypothesized that NH3 flux would be highest at the start of the tunnel and decrease with distance. Air NH3 concentration was measured every 2 m along each tunnel for 2 wk after urea application; NH3 flux did not decrease along the length of the tunnels. Of the 60 measurement periods, when there was significant NH3 volatilization, only two had a significant nonlinear relationship (P ≤ 0.05) between NH3 concentration and distance. For the other periods, the NH3 concentration increased linearly with distance (P ≤ 0.05). The background NH3 concentration difference between halves of the tunnels was not significantly related to NH3 flux difference (P > 0.1). Our results indicate that wind tunnel measurements of NH3 volatilization fertilized using urea are not impacted by a measurable oasis effect.

scholarly journals Validation of CFD Predictions of Urban Wind - Developing a Methodology

2021 ◽  
Author(s):  
◽  
Riley Willis
Keyword(s):  
Wind Tunnel ◽  
City Council ◽  
Wind Tunnels ◽  
Small Scale ◽  
Cfd Model ◽  
Validation Process ◽  
Cfd Simulations ◽  
Entire Area ◽  
Cfd Models ◽  
Wind Tunnel Measurements

<p>“Good mental health in a fluid or CFD modeller is always indicated by the presence of a suspicious nature, cynicism and a ‘show me’ attitude. These are not necessarily the best traits for a life mate or a best friend, but they are essential if the integrity of the modelling process is to be maintained.” (Meroney, 2004)  Over the past 50 years, Computational Fluid Dynamics (CFD) computer simulation programs have offered a new method of calculating the wind comfort and safety data for use in pedestrian wind studies. CFD models claim to have some important advantages over wind tunnels; which remain the most common method of wind calculation. While wind tunnels provide measurements of selected points, CFD simulations provide whole-flow field data for the entire area under investigation (Blocken, 2014; Blocken, Stathopoulos, & van Beeck, 2016). Similarly, wind tunnel measurements must consider the similarity requirements involved with testing a model at small scale, while CFD simulations can avoid this as they are conducted at full scale (Ramponi & Blocken, 2012a).  However, CFD simulations can also often be misleading; and they should only be trusted once they can be proven to be accurate. To appease the requirements for this cynical view- referenced in the above quote- proper verification and validation of a model is imperative.  This thesis investigated and tested the current best practice guidelines around CFD model validation, using existing wind tunnel measurements of generic urban arrays. The goal of the research was to determine whether the existing data and guidance around the validation process was sufficient for a consultant user to trust that a CFD model they created was sufficiently accurate to base design decisions from.  The CFD code Autodesk CFD was used to simulate two configurations first tested as wind tunnel models by the Architectural Institute of Japan, and Opus labs in Wellington. The Wellington City Council wind speed criteria were used to determine whether the CFD simulations met the required accuracy criteria for council consent.  Results from the study found that the CFD models could not meet the accuracy criteria. It concluded that while the validation process provided sufficient guidance, there is a lack of available data which is relevant to CFD validation for urban flows.  It was recommended that at least one improved dataset was required, to build a system by which a consultant can identify what the requirements of a CFD model are to provide accurate CFD analysis of the site under investigation. To accommodate the range of sites likely to be present in urban wind studies, it was recommended that the new dataset provided data for a variety of wind flows likely to be found in cities.</p>

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