Recent Development in the Cremer Impedance: Concept Extension, Experimental Analysis and Numerical Validation

摘要

Recent development in the Cremer impedance concept is summarized in this paper. To begin with, the so-called 'exact' Cremer impedance or solution for single-lined rectangular ducts that is 'exact' in the low frequency range is derived and experimentally analyzed. The 'plug' flow assumption is used in the derivation. Surprisingly, the exact solution has a negative real part in the low frequency range. To investigate the validity of the low frequency result, especially the negative resistance, two numerical analyses are carried out. The effect of boundary layers on the Cremer impedance and the low frequency merging patterns are investigated. In addition, the concept is further extended to double-lined rectangular ducts.