Date of Award
Master of Science In Mechanical Engineering Degree
Dr. Maryam Younessi Sinaki
This study presents a mathematical modeling of behavior of a wind deflecting structure having trap doors supported by gravity hinges. The function of the trap doors is to be fully closed at low wind speeds (under 6.1 m/s), thereby increasing the wind speed, and directing the air flow to a pair of roof top wind turbines (1.3 kW nameplate rating). With wind speeds higher than 6.2 m/s the trap doors will start to open, letting the air move though the structure rather than directing the air flow to the turbines. The opening and closing of the trap doors take place with the help of gravity hinges. Under high-speed wind conditions, the follower of the gravity hinge climbs up the cam surface. As long as the wind speed stays high, the trap door stays open. When the wind speed falls below a prescribed value, the force of gravity acting on the trap doors is a restoring force to bring the trap door into its closed configuration. This study includes the drag force calculations on the trap doors, the torque created by this drag force in an analysis to examine the opening and closing behavior of the trap door under various wind speed conditions. Under the closed trap door position, wind velocity analysis was performed in order to demonstrate the intended function of the wind deflecting structure for amplifying the natural wind speed. A detailed static analysis of the gravity hinge was performed to examine the condition of opening of the trap doors under high wind conditions. A series of parametric studies were performed to demonstrate the behavior of trap doors under low and high wind speed conditions. A gravity hinge of a 5-degree incline was iv considered in this study and the analysis shows the trap doors stay closed for wind speeds of 6.2 m/s and below. Furthermore, the analysis shows that the trap door is fully open for wind speeds above 18 m/s. A range of friction coefficient between 0.01 and 0.1 was considered acting on the components of the gravity hinge.
Moss, Andrew M.d., "Analysis of A Gravity Hinge System For Wind Deflecting Structures of Roof Top Wind Turbines." (2021). ETD Archive. 1275.