A NUMERICAL STUDY ON THE PROPAGATION OF SOUND THROUGH CAPILLARY TUBESWITH MEAN FLOW

As a first step toward the acoustic analysis of catalytic converters i n automotive exhaust systems, wave propagation through a capillary tub e with steady flow is dealt with. Using the general formulations of co nservation equations with non-isentropic conditions based on the low r educed frequency solution, the linearised governing equations are solv ed by the recursive use of numerical methods. No initial assumptions a re imposed on the shape of axial velocity profiles and the radial velo city fluctuation is also included in the analysis. Characteristics of the forward and backward propagating acoustic waves are investigated u nder the influence of steady flow and the calculation is performed up to high shear wave numbers. The characteristics of hydrodynamic waves are also investigated when steady flow is present. The application lim its of the previous work are demonstrated as the shear wave number inc reases. The numerical method is applied to the prediction of the trans mission loss of a stack of capillary tubes with and without mean flow considering the effects of radial components and the calculated result s agree reasonably well with experimental ones. (C) 1996 Academic Pres s Limited