Higher order mode propagation in nonuniform circular ducts

Higher order mode propagation in a nonuniform circular duct without mean flow was investigated. An approximate wave equation is derived on the assumptions that the duct cross section varies slowly and that mode conversion is negligible. Exact closed form solutions are obtained for a particular class of converging-diverging circular duct which referred to as 'circular cosh duct.' Numerical results are presented in terms of the transmission loss for the various duct shapes and frequencies. The results are applicable to multimodal propagation, single mode propagation, and sound radiation from certain types of contoured inlet ducts, or of sound propagation in a converging-diverging duct of somewhat different shape from a cosh duct

Mode Propagation in Nonuniform Circular Ducts with Potential Flow

A previously reported closed form solution is expanded to determine effects of isentropic mean flow on mode propagation in a slowly converging-diverging duct, a circular cosh duct. On the assumption of uniform steady fluid density, the mean flow increases the power transmission coefficient. The increase is directly related to the increase of the cutoff ratio at the duct throat. With the negligible transverse gradients of the steady fluid variables, the conversion from one mode to another is negligible, and the power transmission coefficient remains unchanged with the mean flow direction reversed. With a proper choice of frequency parameter, many different modes can be made subject to a single value of the power transmission loss. A systematic method to include the effects of the gradients of the steady fluid variables is also described

Physical Acoustics

Contains research objectives and reports on two research projects.U. S. Navy - Office of Naval Research (Contract N00014-67-A-0204-0019)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-030

Physical Acoustics

Contains research objectives and summary of research.U. S. Navy - Office of Naval Research (Contract N00014-67-A-0204-0019

Physical Acoustics

Contains research objectives.U.S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-001

Physical Acoustics

Contains reports on two research projects.U. S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-001

Physical Acoustics

Contains research objectives and reports on four research projects.U.S. Navy (Office of Naval Research) under Contract Nonr-1841(42)U.S. Air Force (Air Force Cambridge Research Center, Air Research and Development Command) under Contract AF 19(604)-205

Physical Acoustics

Contains research objectives and summary of research on two research projects.U. S. Navy - Office of Naval Research (Contract N00014-67-A-0204-0019

Physical Acoustics

Contains reports on two research projects.U. S. Navy Office of Naval Research (Contract N00014-67-A-0204-0019

Physical Acoustics

Contains research objectives and reports on one research project.U. S. Navy (Office of Naval Research) under Contract Nonr-1841-(42)Joint Services Electronics Programs (U.S. Army, U.S. Navy and U.S. Air Force) under Contract DA 36-039-AMC-03200(E