Modeling and Analysis

The wind turbine tower and ground are not included in the flow model. The mesh generation is a difficult task due to large variation in size particularly near the edges and the twist at every section of airfoil. The flow domain is selected according to the diameter of the rotor. To use a multiple rotating frame of reference the domain is meshed in two parts: one near the rotor blade and other for the flow field. A fine mesh is generated near the blade in the domain 1.7 m upstream the rotor and 1.5 m downstream with 14.5 m diameter. The complete flow domain is cylindrical a size 5D in upstream (142 m), 10D in downstream (284m) and 2.5D diameter. Appropriate boundary conditions were given for the Moving wall rotor blade, velocity inlet and outlet, Rotating with rotor blade velocity for the air in the small domain and non-viscous outer walls. The wind turbine rotor was analyzed for range of velocities from 6 to 15 m/s.

Axial velocity distribution in the wake behind the rotor

Conclusion

At designed velocity of 10 m/s the pressure and flow velocity contours are plotted at the rotor plane, it was observed that the pressure on one side of the blade is positive and other side is negative. It was observed that the values of pressure away from the blade tend to become zero. When moving near the blade in suction side, the value of negative pressure increases. On the other hand, on the pressure side the positive pressure increases near the bade and become maximum at the edge of the blade. While moving radially outward the axial velocity decreases and reaches to the limit of inlet axial velocity. At the tip of the blade the velocity is very high due to the higher negative value of axial flow factor. Here the axial velocity is higher than the inflow wind velocity which appears in the form of negative value of inflow factor. When the wake rotation is introduced, the tangential component of the rotor wake flow produces an increase of its kinetic energy which has to be compensated for by an additional fall in the static pressure. The tangential induction factor a' is zero upstream of the rotor, where the flow is assumed not to rotate