Proposal of Wind Tunnel for Spinning Body Using Magnetic Suspension

A wind-tunnel system for spinning body is proposed to measure hydrodynamic forces acting on the body. In the proposed system, the body is suspended and rotated by electromagnets. The forces are measured from the control signal for suspension. An experimental apparatus is fabricated to demonstrate the feasibility. In the apparatus, eight electromagnets are placed around the wind-tunnel. A photo sensor using four lens and phototransistors was manufactured for detecting three-dimensional positions of the body. In the experiment, stable suspension and three-dimensional positioning of the body were achieved. Spinning of the body was realized by superimposing two-phase AC signals on the control signal. The fluid drag force was measured from the control input of PID controller. It was ascertained that the drag force increases as the flow velocity increases.