PDF Publication Title:
Text from PDF Page: 009
AN EXPLORATION OF RADIAL FLOW ON A ROTATING BLADE IN RETREATING BLADE STALL 2013 The same characteristic is also observed in the vorticity plots where the point of separation moves toward the trailing edge as the radial station of the measurement plane moves outboard. The nonlinear effect of the tip vortex in delay of separation was observed at approximately 50 mm and less from the tip of the blade (r/R ≈ 0.92). The instantaneous separation line mimics the general trend of Fig. 11, but the line is not smooth as discrete vortices develop within and convect from the separated region as discussed in the section on Radial Flow. This was also illustrated in Raghav et al. (Ref. 19) for a wing in cross-flow. Conclusions 1) In the separated flow over a rotor blade in retreating stall condi- tions, the radial velocity along the blade develops a sharp jet-like profile pointing radially outward. 2) Discrete vortical structures occur in the separated flow field imme- diately above the blade, similar to those breaking off a shear layer. 3) The strongest rms velocity fluctuation in the flow field is near the peak of the radial velocity profile, indicating that the source of vorticity of the discrete structures is the radial jet shear layer rather than the freestream at the upper edge of the separated flow. 4) The discrete vortical structures are observed to “jump” or “peel” off the blade and carry away roughly 30% of the vorticity in the shear layer between the radial jet and the blade surface. 5) The ensemble averaged radial velocity profile data show that the averaged peak radial velocity decreases with increasing radial distance at a given chordwise location, contrary to what would be expected in the absence of the formation and breakup of the discrete vortical structures. 6) From the above, it is concluded that the breaking away of the discrete structures is the mechanism responsible for suppressing the growth of radial jet. 7) Order of magnitude comparisons show that the radial jet develop- ment is strength limited by the breakup into discrete structures, and the discrete structures themselves are first-order phenomena in the flow field of the rotor blade in retreating blade stall. These flow characteristics may have significant effects on the evolution of lift and pitching moment of the blade during retreating blade stall. Appendix: Equations Defining Dynamic Similarity Parameters 1) Tip speed ratio (TSR) was defined as the ratio of local blade speed to the inplane component of velocity to the rotor: The angle of attack for the wind turbine blade (αw) and the rotor setup (αr ) are then defined as Vn αiw = arctan V (A5) tw αw = αiw − αpw (A6) αir = arctan Vi (A7) Vtr whereVtr isthetangentialcomponentofvelocitytothebladeintherotor setup: αr = αpr − αir (A8) 2) Angle of attack: r TSR=V (A1) c Vn =Vw(1−ao)cosγ (A2) where ao is a factor that accounts for deceleration of wind due to wind turbine operation (induced velocity): Vc = Vw sin γ (A3) The tangential component of velocity to the blade is a function of the azimuth angle and defined as Vtw =r+Vcsinψ (A4) 022005-9 3) Reduced frequency (ψ = 270◦): ωf c = where ωf = for a teetering rotor. k = 2U c = 2(r−U∞) c/2r (A9) (1 − U∞/r) Acknowledgments The authors gratefully acknowledge support of this work through a grant from the Army Research Office. Dr. Frederick Ferguson is the technical monitor. Valuable input from Professor Marilyn Smith is grate- fully acknowledged. Assistance in conducting the experiment by Dustin Teuscher and Felipe Ortega and in data reduction by Akshaya Srivastava is greatly appreciated. References 1 McCroskey, W., Dynamics—The 1976 Freeman Scholar Lecture,” Journal of Fluids En- gineering, Vol. 99, (1), 1977, pp. 8–39. 2Carr, L., McAlister, K., and McCroskey, W., “Analysis of the De- velopment of Dynamic Stall Based on Oscillating Airfoil Experiments,” NASA TN D-8382, 1977. 3McCroskey, W., Carr, L., and McAlister, K., “Dynamic Stall Ex- periments on Oscillating Airfoils,” AIAA Journal, Vol. 14, (1), 1976, pp. 57–63. 4McCroskey, W., McAlister, K., Carr, L., Pucci, S., Lambert, O., and Indergrand, R., “Dynamic Stall on Advanced Airfoil Sections,” Journal of the American Helicopter Society, Vol. 26, (3), 1981, pp. 40–50. 5McCroskey, W., McAlister, K., Carr, L., and Pucci, S., “An Exper- imental Study of Dynamic Stall on Advanced Airfoil Sections. Volume 1: Summary of the Experiment,” NASA TM 84245, 1982. 6Lorber, P., “Dynamic Stall of Sinusoidally Oscillating Three- Dimensional Swept and Unswept Wings in Compressible Flow,” Amer- ican Helicopter Society 48th Annual Forum Proceedings, Washington, DC, June 3–5, 1992. 7Carta, F., “Dynamic Stall of Swept and Unswept Oscillating Wings,” UTRC Technical Report ADP005010, 1985. 8Koga, D., and Eaton, J., “Active Control of Unsteady and Separated Flow Structures,” AFOSR TR 89-1210, 1989. 9Larsen, J., Nielsen, S., and Krenk, S., “Dynamic Stall Model for Wind Turbine Airfoils,” Journal of Fluids and Structures, Vol. 23, (7), 2007, pp. 959–982. “Some Current Research in Unsteady FluidPDF Image | Radial Flow Rotating Blade Retreating Blade Stall
PDF Search Title:
Radial Flow Rotating Blade Retreating Blade StallOriginal File Name Searched:
JAHS_Radial Flow.pdfDIY PDF Search: Google It | Yahoo | Bing
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
IT XR Project Redstone NFT Available for Sale: NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Be part of the future with this NFT. Can be bought and sold but only one design NFT exists. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Turbine IT XR Project Redstone Design: NFT for sale... NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Includes all rights to this turbine design, including license for Fluid Handling Block I and II for the turbine assembly and housing. The NFT includes the blueprints (cad/cam), revenue streams, and all future development of the IT XR Project Redstone... More Info
Infinity Turbine ROT Radial Outflow Turbine 24 Design and Worldwide Rights: NFT for sale... NFT for the ROT 24 energy turbine. Be part of the future with this NFT. This design can be bought and sold but only one design NFT exists. You may manufacture the unit, or get the revenues from its sale from Infinity Turbine. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Supercritical CO2 10 Liter Extractor Design and Worldwide Rights: The Infinity Supercritical 10L CO2 extractor is for botanical oil extraction, which is rich in terpenes and can produce shelf ready full spectrum oil. With over 5 years of development, this industry leader mature extractor machine has been sold since 2015 and is part of many profitable businesses. The process can also be used for electrowinning, e-waste recycling, and lithium battery recycling, gold mining electronic wastes, precious metals. CO2 can also be used in a reverse fuel cell with nafion to make a gas-to-liquids fuel, such as methanol, ethanol and butanol or ethylene. Supercritical CO2 has also been used for treating nafion to make it more effective catalyst. This NFT is for the purchase of worldwide rights which includes the design. More Info
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
Infinity Turbine Products: Special for this month, any plans are $10,000 for complete Cad/Cam blueprints. License is for one build. Try before you buy a production license. May pay by Bitcoin or other Crypto. Products Page... More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |