Experimental Measurements of the Laminar Separation Bubble on an Eppler 387 Airfoil at Low Reynolds Numbers

Experimental Measurements of the Laminar Separation Bubble on an Eppler 387 Airfoil at Low Reynolds Numbers
Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
Total Pages: 150
Release: 2018-11-18
Genre: Science
ISBN: 9781731314970

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An experimental investigation was conducted to measure the flow velocity in the boundary layer of an Eppler 387 airfoil. In particular, the laminar separation bubble that this airfoil exhibits at low Reynolds numbers was the focus. Single component laser Doppler velocimetry data were obtained at a Reynolds number of 100,000 at an angle of attack of 2.0 degree. Static Pressure and flow visualization data for the Eppler 387 airfoil were also obtained. The difficulty in obtaining accurate experimental measurements at low Reynolds numbers is addressed. Laser Doppler velocimetry boundary layer data for the NACA 663-018 airfoil at a Reynolds number of 160,000 and angle of attack of 12 degree is also presented. Cole, Gregory M. and Mueller, Thomas J. AIRFOILS; BOUNDARY LAYER SEPARATION; BUBBLES; FLOW VELOCITY; LAMINAR BOUNDARY LAYER; ANGLE OF ATTACK; FLOW VISUALIZATION; LASER DOPPLER VELOCIMETERS; LOW REYNOLDS NUMBER; STATIC PRESSURE...

Experimental Results for the Eppler 387 Airfoil at Low Reynolds Numbers in the Langley Low-Turbulence Pressure Tunnel

Experimental Results for the Eppler 387 Airfoil at Low Reynolds Numbers in the Langley Low-Turbulence Pressure Tunnel
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Total Pages: 234
Release: 2018-07-24
Genre:
ISBN: 9781723574788

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Experimental results were obtained for an Eppler 387 airfoil in the Langley Low Turbulence Pressure Tunnel. The tests were conducted over a Mach number range from 0.03 to 0.13 and a chord Reynolds number range for 60,000 to 460,000. Lift and pitching moment data were obtained from airfoil surface pressure measurements and drag data for wake surveys. Oil flow visualization was used to determine laminar separation and turbulent reattachment locations. Comparisons of these results with data on the Eppler 387 airfoil from two other facilities as well as the Eppler airfoil code are included. Mcghee, Robert J. and Walker, Betty S. and Millard, Betty F. Langley Research Center NASA-TM-4062, L-16430, NAS 1.15:4062 RTOP 505-60-21-01...

An Experimental Analysis of the Laminar Separation Bubble at Low Reynolds Numbers

An Experimental Analysis of the Laminar Separation Bubble at Low Reynolds Numbers
Author: Karla Marie Swift
Publisher:
Total Pages: 96
Release: 2009
Genre:
ISBN:

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This paper is an investigation into the laminar separation bubble that frequently plagues airborne vehicles operating in the low Reynolds number regime -- experimentally found to be typically present in flows with Reynolds numbers below 106 (Lissaman 1983). The specific application driving the present investigation is the fixed wing performance of unmanned micro air vehicles (MAVs), defined by their maximum chord length of 6 inches and current cruising speeds of 10-20 meters per second (Mueller 2001). A basic generic model was chosen for this investigation: a circular arc (section of 16 inch diameter PVC pipe) with sharp leading and trailing edges having a chord length of 9.3 inches and height of 1.5 inches. This airfoil model was tested in the UTSI water tunnel at Reynolds numbers of 27,000 and 45,000. The goal of this study was to gain some insight into the boundary layer behaviour through the use of dye injection for flow visualization and hot film anemometry for quantitative velocity measurements. Small diameter cylinders were then statically placed upstream of the model to determine their interaction with the laminar separation bubble and its effects on the boundary layer downstream over the airfoil model. The length and height of the laminar separation bubble was found to be impacted with a small cylindrical wire placed upstream at all Reynolds numbers and angles of attack with the exception of an 18 degree angle of attack at the higher Reynolds number. However, these changes did not result in a substantial or distinguishable improvement in the downstream separation point. The laminar separation bubble was found to be nearly or completely eliminated when a thermocouple wire was placed upstream of the leading edge. Although the elimination of the bubble would result in only a minor decrease in drag and increase in lift, there would be a possible improvement in the stability of the leading edge stall and possible reduction or elimination in the hysteresis associated with stall.

Low Reynolds Number Aerodynamics

Low Reynolds Number Aerodynamics
Author: Thomas J. Mueller
Publisher: Springer Science & Business Media
Total Pages: 456
Release: 2013-03-08
Genre: Science
ISBN: 3642840108

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Current interest in a variety of low Reynolds number applications has focused attention on the design and evaluation of efficient airfoil sections at chord Reynolds numbers from about 100,000 to about 1,000,000. These applications include remotely piloted vehicles (RPVs) at high altitudes, sailplanes, ultra-light man-carrying/man powered aircraft, mini-RPVs at low altitudes and wind turbines/propellers. The purpose of this conference was to bring together those researchers who have been active in areas closely related to this subject. All of the papers presented are research type papers. Main topics are: Airfoil Design and Analysis, Computational Studies, Stability and Transition, Laminar Separation Bubble, Steady and Unsteady Wind Tunnel Experiments and Flight Experiments.

Low Reynolds Number

Low Reynolds Number
Author: Mustafa Serdar Genç
Publisher: BoD – Books on Demand
Total Pages: 176
Release: 2012-04-04
Genre: Science
ISBN: 9535104926

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This book reports the latest development and trends in the low Re number aerodynamics, transition from laminar to turbulence, unsteady low Reynolds number flows, experimental studies, numerical transition modelling, control of low Re number flows, and MAV wing aerodynamics. The contributors to each chapter are fluid mechanics and aerodynamics scientists and engineers with strong expertise in their respective fields. As a whole, the studies presented here reveal important new directions toward the realization of applications of MAV and wind turbine blades.