Airflow simulation using computational fluid dynamics in a complex terrain: the consideration of wind speed, turbulent intensity and inflow angle

Abstract

This paper presents an investigation of airflow over a rugged mountain to find suitable locations for wind
turbines. The investigation considers turbulent intensity and inflow angle in addition to wind speed. The area
of interest is the mountain around the upper reservoir of Lamtakong Jolabha Vadhana Hydro Power Plant,
Nakhon Ratchasima, Thailand. The Lamtakong Wind Turbine Power System is located near the reservoir. Due
to the ruggedness of the site, according to the angle of slopes, the existing turbines may be experiencing
airflow with high turbulent intensity and non-zero inflow angle. This study uses Computational Fluid Dynamics
(CFD) and Wind Atlas Analysis and Application Program (WAsP) to simulate airflow. CFD is used in the final
analysis to quantify turbulent intensity and inflow angle. The turbulence model is used, while the roughness
height and roughness constant are tuned according to the ground cover. Detailed examinations of cases
show that the highest wind speeds do not always occur at the mountain’s peaks. High turbulent intensity
leads to the exclusion of locations on the lee side of the mountain, where it reaches 18%. The inflow angles
are high on the upwind side of the mountain and can go up to 20 degrees. It is found that the slopes affect
the inflow angles but they do not dictate the inflow angles. Finally, the results of the highest peak suggest that
most suitable turbine spot is approximately 60 m downwind from the point of highest wind speed. The power
density reduces from 515.3 W/m2 to 502.6 W/m2 at 60 m hub-height. Thus, to achieve a zero inflow angle,
turbines may have a power output reduction but they will experience lower turbulence and uneven loading.