scholarly journals Experimental Analysis of a Small-Scale Rotor at Various Inflow Angles

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Amir Kolaei ◽  
Devin Barcelos ◽  
Götz Bramesfeld
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Axial Flow ◽  
Unmanned Aircraft ◽  
Performance Characteristics ◽  
Small Scale ◽  
Flow Conditions ◽  
Wind Tunnel Experiments ◽  
Wind Tunnel Data ◽  
Advance Ratio

The performance characteristics of a rotor that is typically used for small unmanned aircraft were analyzed in a series of wind-tunnel experiments. Wind-tunnel measurements were conducted with the rotor at various inflow angles in order to investigate the effects on the rotor performance of partially or fully edgewise flow as they are typically encountered with small multirotor vehicles. Rotor tests were also performed under static and fully axial flow conditions in order to investigate the aerodynamic performance during hover as well as vertical climb and descent. The wind-tunnel data were corrected to account for the interference of wind-tunnel walls with the rotor wake and the blockage due to the presence of the rotor test stand in the wind-tunnel test section. The results are presented in terms of thrust, power, and roll moment coefficients under different rotor rotational speeds for a T-motor 18x6.1. Additionally, the measured thrust and power coefficients of Master Airscrew Electric 11x7 are compared with available propeller data under static and axial flow conditions for verification purposes. It is shown that the rotor performance characteristics are strongly affected by the freestream advance ratio and the freestream inflow angles. For example, at inflow angles that are typical for multirotor vehicles between about 15° and 0° with respect to the rotor disc, thrust coefficients stay constant or grow with increasing advance ratio, whereas power coefficients remain relatively constant with changing advance ratio.

scholarly journals Surface Renewal as a Significant Mechanism for Dust Emission

2016 ◽  
Author(s):  
Jie Zhang ◽  
Zhenjiao Teng ◽  
Ning Huang ◽  
Lei Guo ◽  
Yaping Shao
Keyword(s):  
Wind Tunnel ◽  
Emission Rate ◽  
Dust Emission ◽  
Limit Surface ◽  
Soil Dust ◽  
Flow Conditions ◽  
Wind Tunnel Experiments ◽  
Surface Renewal ◽  
Surface Particle ◽  
Significant Mechanism

Abstract. Wind-tunnel experiments of dust emissions from different soil surfaces are carried out to better understand dust emission mechanisms. The effects of surface renewal on aerodynamic entrainment and saltation bombardment are analysed in detail, and the measurements are used to test published dust models. It is found that flow conditions, surface particle motions (saltation and creep), soil dust content and ground obstacles all strongly affect dust emission, causing dust emission rate to vary over orders of magnitude. Aerodynamic entrainment is highly effective, if dust supply is unlimited, as in the first 2–3 minutes of our wind-tunnel runs. While aerodynamic entrainment is suppressed by dust supply limit, surface renewal through the motion of surface particles is found to be an effective pathway to remove the supply limit. Surface renewal is also found to be important to the efficiency of saltation bombardment. We demonstrate that surface renewal is a significant mechanism affecting dust emission and recommend that this mechanism be included in future dust models.

scholarly journals Simulation and flight experiments of a quadrotor tail-sitter vertical take-off and landing unmanned aerial vehicle with wide flight envelope

2018 ◽  
Vol 10 (4) ◽  
pp. 303-317 ◽  
Author(s):  
Ximin Lyu ◽  
Haowei Gu ◽  
Jinni Zhou ◽  
Zexiang Li ◽  
Shaojie Shen ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Unmanned Aerial Vehicle ◽  
Wind Tunnel Test ◽  
Small Scale ◽  
Level Flight ◽  
Flight Envelope ◽  
Aerial Vehicle ◽  
Attitude Controller ◽  
And Control ◽  
Thrust And Torque

This paper presents the modeling, simulation, and control of a small-scale electric powered quadrotor tail-sitter vertical take-off and landing unmanned aerial vehicle. In the modeling part, a full attitude wind tunnel test is performed on the full-scale unmanned aerial vehicle to capture its aerodynamics over the flight envelope. To accurately capture the degradation of motor thrust and torque at the presence of the forward speed, a wind tunnel test on the motor and propeller is also carried out. The extensive wind tunnel tests, when combined with the unmanned aerial vehicle kinematics model, dynamics model and other practical constraints such as motor saturation and delay, lead to a complete flight simulator that can accurately reveal the actual aircraft dynamics as verified by actual flight experiments. Based on the developed model, a unified attitude controller and a stable transition controller are designed and verified. Both simulation and experiments show that the developed attitude controller can stabilize the unmanned aerial vehicle attitude over the entire flight envelope and the transition controller can successfully transit the unmanned aerial vehicle from vertical flight to level flight with negligible altitude dropping, a common and fundamental challenge for tail-sitter vertical take-off and landing aircrafts. Finally, when supplied with the designed controller, the tail-sitter unmanned aerial vehicle can achieve a wide flight speed envelope ranging from stationary hovering to fast level flight. This feature dramatically distinguishes our aircraft from conventional fixed-wing airplanes.

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 Kriging Approach for CFD/Wind-Tunnel Data Comparison

2005 ◽  
Vol 128 (4) ◽  
pp. 847-855 ◽  
Author(s):  
J.-C. Jouhaud ◽  
P. Sagaut ◽  
B. Labeyrie
Keyword(s):  
Wind Tunnel ◽  
Response Surface ◽  
Uncertain Parameters ◽  
Free Flight ◽  
Wind Tunnel Experiments ◽  
Data Comparison ◽  
Wind Tunnel Data ◽  
Compressible Turbulent Flow ◽  
Kriging Approach ◽  
Insight Into

A Kriging-based method for the parametrization of the response surface spanned by uncertain parameters in computational fluid dynamics is proposed. A multiresolution approach in the sampling space is used to improve the accuracy of the method. It is illustrated considering the problem of the computation of the corrections needed to recover equivalent free-flight conditions from wind-tunnel experiments. Using the surface response approach, optimal corrected values of the freestream Mach number and the angle of attack for the compressible turbulent flow around the RAE 2822 wing are computed. The use of the response surface to gain an insight into the sensitivity of the results with respect to other parameter is also assessed.

scholarly journals Research and Development of a Small-Scale Icing Wind Tunnel Test System for Blade Airfoil Icing Characteristics

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Lei Shi ◽  
Fang Feng ◽  
Wenfeng Guo ◽  
Yan Li
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Temperature Stability ◽  
Liquid Water Content ◽  
Test System ◽  
Simulation Software ◽  
Small Scale ◽  
Two Dimensional ◽  
Low Speed ◽  
Spray System

In order to study the icing mechanism and anti-icing technology, a small low-speed reflux icing wind tunnel test system was designed and constructed. The refrigeration system and spray system were added to the small reflux low-speed wind tunnel to achieve icing meteorological conditions. In order to verify the feasibility of the test system, the flow field uniformity, temperature stability, and liquid water content distribution of the test section were tested and calibrated. On this basis, the icing tests of an aluminium cylinder, an NACA0018 airfoil, and an S809 airfoil were carried out, and the two-dimensional ice shape obtained by the test was compared with the two-dimensional ice shape obtained by the numerical simulation software. The results show that in the icing conditions and icing time studied, the parameters of the test system are stable, and the experimental ice shape is consistent with the simulated ice shape, which can meet the needs of icing research.

scholarly journals Forebody Wake Effects on Parachute Performance for Re entry Space Application

2020 ◽  
Vol 70 (3) ◽  
pp. 223-230
Author(s):  
Mahendra Pratap ◽  
Anil K. Agrawal ◽  
Subhash C. Sati ◽  
Vipin Kumar
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Design Parameters ◽  
Stability Characteristic ◽  
Limited Data ◽  
Wind Tunnel Experiments ◽  
Subsonic Speed ◽  
Wake Effects ◽  
Scale Down ◽  
Parachute Canopy

Forebody generates its own wake that influences the performance of aerodynamic decelerators during the flights. Many parachute Jumpers have experienced the failure of an ejected pilot chute as the parachute canopy collapsed and fell back on the Jumper because of wake developed behind the Jumper. In the available literature, limited data is available to predict the exact loss of parachute drag in presence of the forebody (FB). The purpose of this paper is to generate a comprehensive aerodynamic data to study the behaviour of FB-parachute dynamics by conducting the wind tunnel experiments. Wind tunnel test has been carried out to establish the initial design parameters of aerodynamic parachute. The experiment was carried out on a scale down model of 20 degree conical ribbon drogue parachute and FB with and without each of them at a subsonic speed for studying dynamic stability characteristic for different orientation of FB. The test results indicate that to ensure adequate stability for the capsule to descend vertically at a low subsonic speed, a cluster of two drogue parachutes be used. Under such condition, the overall drag coefficient found to be above 0.50 providing not only a safe descends velocity but increasing reliability of mission as well.

The ABC Helicopter

1969 ◽  
Vol 14 (4) ◽  
pp. 10-19 ◽  
Author(s):  
M. C. Cheney
Keyword(s):  
Wind Tunnel ◽  
Rotor Blades ◽  
Small Scale ◽  
Wind Tunnel Experiments ◽  
Forward Flight ◽  
Basic Principles ◽  
Stability And Control ◽  
Analytical Research ◽  
And Control

Presented is an introduction to the basic principles of the Advancing Blade Concept (ABC) rotor and a review of the related experimental and analytical research conducted in support of the Sikorsky ABC helicopter program. The ABC helicopter is comprised of two coaxial, counter‐rotating rotors having blades rigidly attached to the hub except for feathering freedom. The blades are significantly stiffer than conventional rotor Blades and are capable of supporting large moments without excessive tip deflections. Improved forward flight efficiency and the elimination of retreating blade stall results from the ability of the ABC rotor to utilize to a large extent the lifting potential of the advancing blades—a capability not present in conventional single rotors. Results of various small‐scale wind tunnel experiments are presented along with summaries of several analytical investigations which were conducted to provide information concerning rotor performance, blade dynamics, vibration, and stability and control

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