Numerical simulation of dynamic-stall suppression by tangential blowing

Towne, Matthew C.

doi:10.2514/6.1994-184

Cited by 2 publications

(5 citation statements)

References 36 publications

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“…In a previous numerical study by Towne,3 nearly tangential blowing was applied at a series of locations along the airfoil upper surface to assess the effect of slot position on DSV suppression. Based upon this work and the suction experiment of Karim and Acharya, 2 the comparison between suction and blowing was conducted for a single slot position of width 0.00717c at x/c = 0.05.…”

Section: Resultsmentioning

confidence: 99%

“…An extensive grid study was conducted on mesh sizes ranging from 203 to 505 points in the £ direction (circumferential) and 101 to 301 points in the 17 direction. 3 Each grid was applied to a physical domain that extends nominally 30 chord lengths away from the airfoil. The current results were obtained on a 361 x 201 grid that had minimum £ and 77 spacings of 0.000082 and 0.00005c, respectively.…”

Section: Numerical Methodologymentioning

confidence: 99%

“…However, 6-degreeof-freedom time histories of model motions have recently become available via a computerized, optically-based data acquisition system known as the Spin Tunnel Model Space Positioning System (MSPS). 3 Using the equations of motion coupled with these time histories, a simple procedure for estimating the moment coefficients about all three body axes during a spin that may or may not be oscillatory is developed. The method used in this Note is similar to that proposed by Neihouse et al 1 for determining the moments of a spinning airplane from flight-test data.…”

Section: Introductionmentioning

confidence: 99%

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Numerical study of alternate forms of dynamic-stall-vortex suppression

Towne

Buter

1995

Journal of Aircraft

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Nomenclature C h C (t , C m = lift, drag, and moment coefficients C M = blowing coefficient, rhjVj/q^c c = chord M = Mach number rhj = mass flow rate of jet, pjSVj sin q x = dynamic pressure, \pJJL Re ( = chord Reynolds number, U^clvŝ = slot width t + = nondimensional time, tUJc U^ = freestream velocity Vj = velocity of jet jc, y = coordinates of moving reference frame attached to airfoil a = angle of attack a h = onset angle of attack (blowing or suction) v = dynamic viscosity f, j] = transformed coordinates p = density 4> = jet blowing angle, 10 deg H + = nondimensional pitch rate, a>c/UÎ ntroduction A TTEMPTS have been made by numerous researchers toharness the large aerodynamic forces temporarily generated on a streamlined body rapidly pitched beyond its steady stall angle of attack. Dynamically pitched airfoils exhibit maximum lift coefficients two or three times the static maximum lift. 1 Uncontrolled, the ensuing unsteady motion results in dynamic stall. The dynamic stall phenomenon arises in several applications: wind turbine blades, helicopter rotor blades, jet engine compressor blades, and rapidly pitched airfoils. The current study compares and contrasts two approaches to dynamic stall suppression: 1) suction and 2) nearly tangential blowing, applied in the vicinity of the leading edge of a NACA 0015 airfoil.Dynamic stall suppression via leading-edge suction and leading-edge tangential blowing focuses on the removal of low momentum fluid that accumulates along the airfoil upper surface as it is pitched upward. Specifically, as the airfoil is pitched up, the adverse pressure gradient along the upper surface promotes the forward propagation of reverse-flowing fluid into the leading-edge region. The thickening of this low momentum fluid region near the leading edge ultimately forces an upward displacement and "kinking" of the feeding shear layer. The kinking of this shear layer marks the initial formation of the dynamic stall vortex. Suction experiments by Karim and Acharya 2 demonstrated that the key to dynamicstall-vortex-formation suppression is to remove fluid from underneath the leading-edge-originating shear layer at the same rate as the reverse-flowing-fluid-pooling accumulation rate. Results by Towne 3 verify their findings numerically and demonstrate that tangential blowing applied upstream and/or in this pooling region is also effective in eliminating the low momentum region, and hence, in delaying dynamic stall vortex (DSV) formation.The flow regime of interest is one of low speed and low Reynolds number. A compressible Navier-Stokes code developed by Visbal to numerically investigate dynamic stall 4 -5 is used. The nominal flow and pitch-rate conditions are M= 0.2, Re c = 2.4 x 10 4 , and H+ -0.2. Numerical MethodologyThe strong conservation law form of the two-dimensional compressible Navier-Stokes equations are cast in an inertial frame of reference using a general time-dependent coordinate transformation to account for the motion of the body. Closure of the system is provided by the per...

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Section: Resultsmentioning

confidence: 99%

Section: Numerical Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical study of alternate forms of dynamic-stall-vortex suppression

Towne

Buter

1995

Journal of Aircraft

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“…Pitching airfoil simulations for each blowing condition were initialized from transient, static (airfoil) solutions (=0˚) having a minimum of 10 domain flow though periods, the time it takes a single particle to traverse the computational domain (55). For low Re flow, the solution about a NACA airfoil at zero- is periodic due to TE edge vorticity and resultant stagnation point oscillations (151). However, although the processes that characterize DS are known to be independent of airfoil starting position () (152), the timing of dynamic stall development depends on the initial position of the TE wake and thus has an impact on the aerodynamic loading variation with AoA (151).…”

Section: Dynamic Model Initializationmentioning

confidence: 99%

“…For low Re flow, the solution about a NACA airfoil at zero- is periodic due to TE edge vorticity and resultant stagnation point oscillations (151). However, although the processes that characterize DS are known to be independent of airfoil starting position () (152), the timing of dynamic stall development depends on the initial position of the TE wake and thus has an impact on the aerodynamic loading variation with AoA (151). Thus, for each condition, a minimum of three pitch cycles were completed to establish a time-periodic solution, and the solutions reported reflect the fourth pitch cycle airfoil characteristics (from rest).…”

Section: Dynamic Model Initializationmentioning

confidence: 99%

Aerodynamic Response of a Pitching Airfoil with Pulsed Circulation Control for Vertical Axis Wind Turbine Applications

Panther¹

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Vertical Axis Wind Turbines (VAWTs) have experienced a renewed interest in development for urban, remote, and offshore applications. Past research has shown that VAWTs cannot compete with Horizontals Axis Wind Turbines (HAWTs) in terms of energy capture efficiency. VAWT performance is plagued by dynamic stall (DS) effects at low tip-speed ratios (), where each blade pitches beyond static stall multiple times per revolution. Furthermore, for <2, blades operate outside of stall during over 70% (plus) year sabbatical, and the unhesitant welcome on my return. You know who you are. I love and appreciate you all more than you will ever know. I would like to thank my family for their support for the duration of this process, especially Uma, Pap, and Noni for their dependability and endless (and affordable) daycare services for Bode. I would particularly like to thank my Mom and Dad for unbounded support and encouragement to get me here. I would also like to especially thank Jess for her own selfless and enduring support, patience, and love while I completed this final degree. I could not have finished this without her behind me. There should be an honorary degree for such people. A small army of people made sacrifices to complete this project, but unfortunately only one person gets the credit. Finally, I would like to thank Bode Odie, the dinosaur boy, for unknowingly motivating me with constant laughter, innocence, curiosity, and love. Thank You. v

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Numerical simulation of dynamic-stall suppression by tangential blowing

Cited by 2 publications

References 36 publications

Numerical study of alternate forms of dynamic-stall-vortex suppression

Numerical study of alternate forms of dynamic-stall-vortex suppression

Aerodynamic Response of a Pitching Airfoil with Pulsed Circulation Control for Vertical Axis Wind Turbine Applications

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