Basic Understanding of Airfoil Characteristics at Low Reynolds Numbers (104–105)

Winslow, Justin; Otsuka, Hiroko; Govindarajan, Bharath; Chopra, Inderjit

doi:10.2514/1.c034415

Cited by 251 publications

(135 citation statements)

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“…18b, 19b). At this Re range, as the Re decreases below 100,000 there is an increase in drag, particularly because of premature flow separation and failure to reattach, resulting in a reduced drag bucket and a large decrease in lift [36]. At Re in the range between 50,000 and 100,000 the separation bubble and turbulent boundary-layer thickness both increase in size (compared to higher Re ), a consequence of the higher contribution of the viscous forces, resulting in increased parasitic drag [36].…”

Section: Xfoil Resultsmentioning

confidence: 97%

“…At Re in the range between 50,000 and 100,000 the separation bubble and turbulent boundary-layer thickness both increase in size (compared to higher Re ), a consequence of the higher contribution of the viscous forces, resulting in increased parasitic drag [36]. Nevertheless, at such low Re , the increase in airfoil thickness results in considerable increase in form drag, due to trailing edge separation, while simple flat plates outperform conventional airfoils for Re lower than 50,000 [36].…”

Section: Xfoil Resultsmentioning

confidence: 99%

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Low Reynolds airfoil family for small horizontal axis wind turbines based on RG15 airfoil

et al. 2020

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The present study introduces a low Reynolds number (Re) airfoil family for the entire blade span of small wind turbines, aiming to reduce the effects related to laminar separation, improve startup response and meet acceptable levels of structural integrity. Six airfoils of varying relative thickness were designed by increasing the thickness distribution of RG15 airfoil up to 50% and adopting a rounded trailing edge with a diameter equal to 1% of the chord length. The aerodynamic performance of RG15 family was initially evaluated by means of XFOIL code at several low Reynolds numbers ranging from 60,000 to 300,000 and angles of attack between − 6° and 14°. XFOIL analysis revealed that increasing relative thickness leads to the reduction of maximum lift-to-drag ratio (C L ∕C D ) . However, this percentage reduction decreases with increasing Re. The maximum reduction in maximum C L ∕C D was found at 60,000 Re for the thickest airfoil of RG15 family. Conversely, a growth of maximum lift coefficient (C L ) was observed by increasing relative thickness. Besides, a Reynolds-Averaged Navier-Stokes (RANS) analysis was also conducted at 300,000 Re to get additional information on the flow characteristics. Comparisons between the XFOIL and RANS data were performed. The results of RANS simulations were generally in accordance with those of XFOIL. However, notable over-estimations of drag coefficient (C D ) were detected. The behavior of the recirculation area behind the rounded trailing edge and that of the separation bubble near the leading edge for different values of relative thickness and angle of attack was examined. Thickening of the airfoils was found to have a beneficial impact on the appearance of separation bubbles, while no significant effect of the rounded trailing edge on C L and C D was observed.

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Section: Xfoil Resultsmentioning

confidence: 97%

Section: Xfoil Resultsmentioning

confidence: 99%

Low Reynolds airfoil family for small horizontal axis wind turbines based on RG15 airfoil

et al. 2020

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“…This deprivation in performance is again caused by the failure of the shear layer to reattach. A detailed numerical work [15] done to appreciate the aerodynamics performance of numerous airfoils at low Reynolds numbers.…”

Section: Fig1: Flight Speed Versus Chord Reynolds Number [1]mentioning

confidence: 99%

Numerical Analysis of Protrusion Effect over an Airfoil at Reynolds Number -105

Bodavula¹,

GUVEN²,

Yadav³

2019

IJRTE

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Need of micro aerial vehicles and Unmanned AirVehicles is increasing due to military, defense and civilian requirements. These vehicles fly at very small Reynolds numbers and have to move in confined spaces with a bare minimum speed, to achieve high lift coefficient is the main concern. The main focus of this research paper is to carry out the computational analysis and study the unsteady flow over NACA0012 airfoil with right angle triangular protrusion at the Reynolds number 10 5 . The location of the protrusion is 0.05c, with three different heights of protrusion 0.005c, 0.01c, and 0.02c, normal to the surface of the airfoil. Geometric modeling and grid generation are created using the ICEM CFD software and numerical analysis carried out using CFD Software at various angle of attacks ranging from 0 0 to 16 0 with 2 0 intervals. Numerical validation has done and compared. The results obtained from the research work is recommend that for smaller protrusions the lift and drag coefficients are unaffected in the low angle of attacks while the lift characteristic is significantly improved at the higher angle of attacks.Numerical Analysis of Protrusion Effect over an Airfoil at Reynolds Number -10 5 2584 Fusion Technologies, advanced nuclear methods. He has written over 50 papers, 30 opinion articles and 4 books on future of space technology and nuclear technology. Dr. Guven has taught wide range of courses and he is coordinator in an Experimental Nanosatellite project.

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“…These broad areas of applications over which airfoils are employed presents a significant challenge to engineers in terms of required airfoil performance. Thus numerous airfoil designs have been analyzed at a wide range of operating conditions is the Reynolds number for different aerodynamic performances [3][4][5]. One of the challenging design and aerodynamic analysis of airfoils is at low Reynolds numbers.…”

Section: Introductionmentioning

confidence: 99%

Comparing the Effect of Different Turbulence Models on The CFD Predictions of NACA0018 Airfoil Aerodynamics

Khan¹,

Bashir²,

Baig³

et al. 2020

CFDL

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The analysis of aerodynamic forces on two-dimensional airfoils and flow phenomena associated with different Reynolds number has been widely investigated for aerospace vehicles and wind turbines. Various numerical methods have been used with different turbulence models, and the discrepancy in flow physics differs between each model. This work presents the numerical analysis of the aerodynamic performance of NACA 0018 airfoil using different turbulence models. The Computational Fluid Dynamics (CFD) solver, Ansys Fluent, is used for this numerical study. The available experimental data of NACA 0018 airfoil is used for comparing numerical outputs, and the difference in the lift, drag, and pressure coefficients are evaluated, respectively. Structured meshing is employed for all the investigated models for the analysis for lift and drag coefficients using four different turbulence models. Measurements of aerodynamic coefficients and surface pressures are recorded for a range of Re=0.8x10 5 to Re=0.3x10 6 and angles of attack (0° to 18°). The SST k-omega model provided the best lift coefficient predictions for low angles of attack Results also indicate that the flow separation regions and reattachment locations can be predicted by the Transition k-klω model.

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Basic Understanding of Airfoil Characteristics at Low Reynolds Numbers (104–105)

Cited by 251 publications

References 10 publications

Low Reynolds airfoil family for small horizontal axis wind turbines based on RG15 airfoil

Low Reynolds airfoil family for small horizontal axis wind turbines based on RG15 airfoil

Numerical Analysis of Protrusion Effect over an Airfoil at Reynolds Number -105

Comparing the Effect of Different Turbulence Models on The CFD Predictions of NACA0018 Airfoil Aerodynamics

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