Fluid Dynamic Principles to Generate Axial Induction P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Basic Methods of Solid Fluid Interactions to Extract Wind Power ……

Mechanical Power Extraction :The fundamental Aerodynamic Phenomena The type of aerodynamic forces used for generation of change in tangential velocity across a rotor greatly influences the actual power developed by a wind turbine. All bodies exposed to an airflow experience an aerodynamic force. The components of which are defined as aerodynamic drag (in the direction of flow), and as aerodynamic lift (at a right angle to the direction of flow}. The real power coefficients obtained vary greatly in dependence on whether aerodynamic drag or aerodynamic lift is used for power generation. A significant enhancement in power generation can be achieved in lift machines when compared to and drag machine. This is due to the fact that much higher relative wind velocities can be achieved with lift machines.

Basic Principle of Changing Angular Momentum Lift driven WT Drag driven WT

Drag Translator Drag results from the relative velocity between the wind and the device. The power extracted by an elementary drag is the product of the drag force and the translation velocity.

Simple Drag Device The simplest type of wind energy conversion can be achieved by means of pure drag surfaces. The air impinges on the surface A with velocity V0. The instantaneous power capture P from the aerodynamic drag D, and the velocity Vblade with which it moves is expressed as : V0 Define coefficient of drag:

Capacity of Drag Device Instantaneous Power Developed by a drag device Average Power Developed by a drag device

Power Coefficient of A Drag Wind Turbine The instantaneous power coefficient Maximum instantaneous power coefficient Define Blade Speed Ratio,  Condition for maximum value of CPmax,

Efficient Drag devices The aerodynamic drag coefficient of a concave surface curved against the wind direction can hardly exceed a value of 1.3. V0 vr

Cup anemometer V0 +Vb R V0 V0-Vb

Maximum Torque Generated by A Cup Anemometer

Selection of Cup Geometries

Instantaneous Drag Coefficient  

Cup Anemometer as An Wind Speed Measuring Devices-1

Cup Anemometer as An Wind Speed Measuring Devices-2 

Cup Anemometer as An Wind Speed Measuring Devices-3 

Savonius Rotor Wind Turbine

Creative Designs

Lift Devices

Lift Based Blade in Wind Turbine

Flow past an airfoil