Kazuki Aoyama

The cavitation around a butterfly valve occurs because of the large flow separation behind the valve body and the interference of the flow from the nozzle side and the flow from the orifice side. To avoid this cavitation, the installation of perforated plates behind the valve are proposed in this study. From the experimental results, the cavitation noise can be reduced by the perforated plates. It was confirmed by the numerical analysis that the holes of the plates were helpful for pressure recovery behind the valve body. Butterfly valves are widely used in industry because of their compactness and simple construction. Many kinds of anti-cavitation valves have been proposed, however, those are relatively expensive and the structures are complicated. The installations of perforated plates are very easy and very effective in practical use.

This paper deals with the aerodynamic interference between two vehicles which are running in close proximity and are subjected to crosswind. Measurements of the aerodynamic drag, side force and yawing moment were performed at different wind angles and longitudinal and lateral distances between two vehicles. In crosswind, extreme proximity between the vehicles ahead and behind provides several peaks of aerodynamic drag, side force and yawing moment acting on the vehicles. When one vehicle passes the other one in crosswind, the large variation in these forces and moment leads to the danger of driving. Numerical results by the CFD show a good agreement with experimental ones. They reveal that the aerodynamic drag is influenced by airflow behind the other vehicle, and that the side force and the yawing moment are also influenced by complicated airflow structure due to the aerodynamic interference between two vehicles.