Cody Beckemeyer Advisors: Junkun Ma Cris Koutsougeras ET 494 Fall 2013

Comparison to Horizontal Axis Wind Turbine Vertical Axis Wind Turbines can be placed independently of wind direction, perfect for places that the wind changes daily Gearbox and generator are able to be placed near the ground, so they are easier to be maintained than HAWT VAWT have lower rotational speed and lower tip speed ratio therefore higher torque is involved HAWT have higher tip speed ratio and coefficient of performance Cp, but have lower torque VAWT have either low or insignificant starting torque so the rotor must be brought up to speed by either a small generator as a motor or a small secondary rotor

Three Blade Turbine With Pivoting Airfoils

NACA0012 Airfoil

Angle of Attack Θ - It is the angle between the chord line of the blade and the relative wind or the direction of the air flow - changes due to the variation of the relative velocity - Rotating the blade will alter the angle of attack.

Driving Force Pressure on the surface of the airfoil creates the force that drives the rotation of the system.

Comsol Multiphysics Comsol was used to get the initial pressures over the surface of the airfoil. 2D modeling of the airfoil in a simulated wind tunnel at 5 m/s and standard atmospheric pressure. Rotating the airfoil through 360 degrees allowed me to find the pressure at any given angle of attack.

Comsol Multiphysics

Distributed Pressure Pressure is distributed over each individual segment. Using this, Net Pressure can be calculated.

Equal pressure distribution minimum pressure

Calculating Concentrated Pressure Each segment has a distributed pressure, but the concentrated pressure is the key to calculating net Pressure.

X and Y magnitudes Net pressure is found using the obtained x and y magnitudes of pressure with Pythagorean Theorem.

Pressure with attack angle at 30˚

Torque Is The Key To Motion Calculating the torque generated on the support arm at any given angle allows us to adjust the angle of attack so that maximum efficiency is achieved.

Support arm in motion As the support arm begins to move from its original position, an angle alpha Will be created. This angle is used to calculate torque as the length of the Support arm “changes”

Lift and Drag - As both the magnitude and orientation change the resultant force Fr changes - The resultant force is composed of both normal component Fn and tangential component Ft

Calculations Gathered 131 X coordinates and 131 Y coordinates compose the surface of the foil. Using the difference between each and its corresponding coordinate, I found the length of each segment and used this in conjunction with the distributed pressure for a concentrated pressure. The concentrated pressure is calculated into the X and Y magnitudes that compose it. Summation of these components led to finding the net pressure via magnitude formulae(Pythagorean theorem). Once the net pressures are obtained, using the length of the supporting arm, torque can be calculated by T=Fd

Torque Generated

VAWT Project – Cody Beckemeyer