Computation of Noise from A Yawed Cylinder and Rotating Cylinder

초록

The noise sources from a rotatin ylinder were indentified to describe the blunt trailing edge moise. To compute moise from three-dimensional cross-flows over a cylinder with a yaw angle, we followed Curl's acoustic analogy for interaction of organized structures with the surface. The computed far-field noise showed peaks at Strouhal numbers ranging from 0.135 to 0.165 for the yawed cylinder flow with end-plates placed at both extremes under the yaw angle of 30° and Reynolds number of . It was observed that the slantwise shedding at angles oteher than the cylinder yaw angle is intrinsic to inclinded cylinder, with the result of shedding angles between 15°and 31°. To study the railing-edge wake thickness and unsteady lift-coefficient distribution in the span-wise direction of a rotating fan blade, the flows around rotating cylinder with 1,000 rpm were simulated and the far-field noise was exactly computed using the Ffowcs Williams and Hawkings equation with quadrupole source term. The incoming velocities and stagnant zones were continuously distributed along the cylinder, and their changes made the Strouhal sheddings to occur at different phases even at almost same Strouhal number.