Abstract

The influence of surface roughness on the acoustic spectrum in a pulsing restricted flow is investigated over a range of roughness sizes and flow conditions. Four different roughness scenarios are introduced, ranging from smooth to a relative roughness of 0.0486 based on hydraulic diameter. These span three different restriction severities ranging from moderate (56% restricted) to severe (82% restricted) based on the American Society of Echocardiography rating of aortic stenosis. The influence of restriction and roughness on the distribution of energy in the acoustic spectrum is evaluated, showing that enhanced roughness correlates with higher frequencies (150–300 Hz) becoming prominent in the spectrum. This trend follows with increasing restriction. As the Reynolds number changes, the spectral shape is not significantly affected, but the relative amount of energy in frequencies greater than 150 Hz does increase. A measure of frequency coupling is investigated by calculating the bicoherence for these cases, providing another quantitative assessment of the data. As more roughness is introduced, frequency coupling diminishes across all restrictions and Reynolds numbers. This new metric may provide a way of assessing the roughness of an internal flow through non-invasive means.

This content is only available via PDF.
You do not currently have access to this content.