Reynolds number effect in a problem of sound generation by round and truncated cylinder streamlined by turbulent flow

Central Aerohydrodynamic Institute (TsAGI) Zhukovsky Str. 1, Zhukovsky, Moscow region 140180, Russia

Abstract

Well-known situation when bluff body is streamlining by turbulent flow is considered. Recently obtained experimental results for cylinder and role of small quadrupole sources in the wake are discussed. They appear to be strongly connected with the dipole sources located on the cylinder. Interference leads to surprising picture of the resulting sound field detected in experiment: equivalent dipole sources are located in the wake zone far downstream from the cylinder. The understanding of the effect of dipole abnormal shift helps to elaborate the modi¦ed cylinder (truncated cylinder) con¦gurations which are considered. These con¦gurations present attractive variant of airframe noise control where control realized by self-tuning of reflected signal leading to suppression of uncompensated dipoles.