Possible Methods for Removing Small Airborne Particles from the Flow in the 5-Metre Pressurized Low-Speed Wind Tunnel

摘要

Because of the size and complexity of the 5-metre wind tunnel, its use raises problems of erosion of wind-tunnel models which have not been encountered with other low-speed facilities. Two methods for removal of small particles have been investigated. They are: (1) the use of fine mesh fabric screens as filters; and (2) by aerodynamic separation at the corners of the tunnel circuit. (The latter investigation involves the computation of the trajectories of particles in a turning flow.) The results show that particles smaller than 0.3 mm cannot be filtered out within the practicable pressure drop limitations of the tunnel circuit. However, small particles have a sufficiently high probability of striking the concave surfaces of the corner vanes that if grease or some other retentive material were applied the particles could be quickly removed from the circuit. This latter method is being kept in reserve for the 5-metre tunnel, since physical means such as sweeping and vacuum cleaning have so far seemed to give adequate results. After lengthy shutdowns for maintenance of the 8 ft by 8 ft tunnel at RAE Bedford, the lower parts of the corner vanes of that tunnel are coated with a suitable grease to remove small airborne particles. (Author)