A fluxional force-generated sound reducing device

摘要

Fine fibers 5 are planted on a surface of an object 1 moving relative to a fluid or on an inside surface of a pipe or duct 2 conveying a fluid therethrough at a portion which comes into contact with the fluid. 1) When a turbulent flow from the upstream side collides with the surface covered with the fibers, the fibers 5 function as a cushion so as to soften the vortexes and reduce pressure fluctuations. 2) The boundary layer near the surface may easily be transformed into a turbulent flow by the fine fibers 5 so that the flow becomes less spatially correlated. Further, when any generated turbulent flow passes by, pressure fluctuations can be reduced by the fibers. 3) Each fiber is very fine and soft, and therefore does not exerts any reaction forces (or any pressure fluctuations) against the flow. As a result, the sound arising when the flow collides with the fibers is extremely softened.