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Mechanical and Aeronautical Engineering Department
 Ken Visser
  Associate Professor

  PO Box 5725
  CAMP Building 361
  T: (315) 268 7687

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 MAE Faculty

 Wind Energy Group


Renewable Energy Research

Multi-Blade Low Speed Wind Turbine Design
Experimental and numerical studies are being conducted to evaluate the impact of solidity and blade number on the aerodynamic performance of a horizontal axis wind turbine. Blade element momentum and lifting line based wake-vortex methods are being used to study optimum design and constant-chord, untwisted blades. Wind tunnel experiments on a small turbine model are being performed to compare with numerical trends. Numerical results indicated that rotors with increased solidity and blade numbers above conventional 3 bladed designs, could yield higher power coefficients, Cp, for optimum design blades and constant chord untwisted blades. The tip speed ratio at these maximum power coefficients is lower, in ranges of 3 to 4 versus 5 to 7 for most modern designs. Wind tunnel studies have demonstrated power coefficient increases with solidity for a range of solidities between 7% and 27%, but did not indicate performance improvements for changes in blade number. Increasing the pitch angle decreased the optimum tip speed ratio range significantly with a small (5% or less) change in maximum CP. Contrary to numerical predictions for the optimum design 3 bladed rotors, an increased experimental solidity increased Cp and reduced the tip speed ratio of the optimum operating point. As blade number was increased at a constant solidity of 10% from 3 to 12 blades, aerodynamic efficiency and power sharply decreased, contrary to the numerical and the flat plate experimental results. Low Reynolds numbers and wind tunnel blockage effects limit these conclusions and a full scale prototype rotor is being constructed to examine the results of the numerical and experimental studies using a side-by-side comparison with a commercially available wind turbine at the Clarkson University wind turbine test site. For a short movie (13.6 MB), click here.

Wind Turbine Wake Flow Structure
Flow visualization is being used to observe and correlate the flow field of small horizontal axis wind turbine with the measured power extracted from the wind stream. Blade pitch angle and blade number have been varied for a series of constant chord, untwisted blade configurations. The off-body flow around the rotor is visualized using smoke particles and a laser light sheet while the power generated by the turbine is measured simultaneously in the wind tunnel. It hs been observed that for a given configuration and blade pitch, the wake vortex spacing scaled inversely with blade number and tip speed ratio to indicate the point of maximum turbine performance. The best operating point, over the entire blade pitch range, was found to correlate with the tip speed ratio to the third power. For a nifty flow visualization movie (27.2 MB), click here.

MDO Studies
Efforts are underway with the Department of Electrical Engineeing to design a new generator-rotor system that optimizes the energy transfer from the aerodynamic loads to the production of electricity. Studies involve building different types of generators and interfacing them with conventional and alternative blade configurations. The Clarkson Honors and REU programs have also afforded the opportunity for undergraduates to get involved in research activities.

Publications and Reports

Jedamski, D., and Visser. K., "Computational Analysis of a Diffuser Using USM3D for Diffuser Augmented Wind Turbines" AIAA 2013-2966, 31st AIAA Applied Aerodynamics Conference, San Diego, CA, June 2013.

Bohl, D., Helenbrook, B., Kanya, B., Visser. K., Marvin, R., Mascarenhas, B., Parker, M. and Rocky, D., "Analysis and Design of a Wind Turbine with a Wind Accelerator" AIAA-2011-3814, 29th AIAA Applied Aerodynamics Conference, Honolulu, Hawaii, June 2011.

Pomeroy, B. W., and Visser, K.D.,"A Computational Study of Induced Drag Behavior for Spanwise Cambered Wings" AIAA-2010-4227, 28th AIAA Applied Aerodynamics Conference, Chicago, IL., June 2010.

Kanya, B. M., and Visser, K.D., "The Impact of Airfoil Selection on the Design of Small Horizontal Axis Wind Turbines" AIAA-2010-1583, 48th AIAA Aerospace Sciences Meeting and Exhibit, Orlando, FL., January 2010.

Moeller, M. M., and Visser, K.D., "Experimental and Numerical Studies of a High Solidity, Low Tip Speed Ratio DAWT" AIAA- AIAA-2010-1585, 48th AIAA Aerospace Sciences Meeting and Exhibit, Orlando, FL., January 2010.

Czajkowski M.F. and Visser K, "Feasibility of a Unique Wind Powered Home Heating System" , AIAA 2009-216, 47th AIAA Aerospace Conference, Orlando, January, 2009.

Rector, M. C., and Visser, K.D., "Solidity, Blade Number, and Pitch Angle Effects on a One Kilowatt HAWT", AIAA-2006-0608, 44th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV., January 2006.

M.A. Khan, S. Zorlu, R. Guan, P. Pillay, K.D. Visser, "An Integrated Design Approach for Small Grid-tied Permanent Magnet Wind Generators", IEEE Power Africa Conference and Exhibition, Johannesburg, South Africa, July 16 – 19, 2007

Rector, M. C., and Visser, K.D., "Aerodynamic Design of a Small Contra-Rotating HAWT," AIAA-2007-1371, 45th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV., January 2007.

Rector, M. C., and Visser, K.D., "Solidity, Blade Number, and Pitch Angle Effects on a One Kilowatt HAWT", AIAA-2006-0608, 44th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV., January 2006.

Khan, M.A., Pillay, P., and Visser, K.D., ≤ On Adapting a Small PM Wind Generator for a Multi-Blade, High Solidity Wind Turbine, IEEE Transactions on Energy Conversion, Vol. 20, No. 3, September 2005.

Bennington, M.A. and Visser, K.D., ≥Flow Field Characteristics of an Optimized Multi-Bladed Horizontal Axis Wind Turbine≤, 11th International Symposium on Flow Visualization, August 9-12, 2004, University of Notre Dame, Notre Dame, Indiana, USA

Duquette, M.M, Swanson, J. and Visser, K.D., ≥Solidity and Blade Number Effects on Small Horizontal-Axis Wind Turbines,≤ Wind Engineering, Vol 27, No. 4, pp. 299-316, 2003.

Humiston, C. and Visser, K.D., ≥Full Scale Results of Solidity, Blade Number and Pitch Angle, on the Aerodynamics of Small Horizontal-AxisWind Turbines,≤ Wind Energy Conference South Africa, November 2003.

Duquette, M. and Visser, K.D., ≥Numerical Implications of Solidity and Blade Number on Rotor Performance of Horizontal-Axis Wind Turbines,≤ Journal of Solar Energy Engineering, Vol. 125, No. 4, pp. 425-432, November 2003.