Effect of tube ovalling on pressure wave propagation speed.
For physiological and other flows it is often assumed that the pressure pulse wave speed is given by the classic Moens-Korteweg expression and this may be used, for example, to assist in the determination of in vivo blood vessel wall incremental Young's modulus. A number of physical factors affecting the value of this wave speed have been reviewed in the literature, but the effect of slight ovalling of the tube cross-section is rarely mentioned. The analysis for a tube of elliptic cross-section shows that even a very small degree of ovalling can cause quite substantial reductions in Young mode wave propagation velocities compared with the classic Moens-Korteweg expression. Bending-induced changes in cross-section shape with internal pressure increase the apparent elasticity of the tube wall. Experimental confirmation is provided by waterhammer wave speed measurements in a copper tube that has been ovalled by coiling. Even though the Young mode is not dominant in this case, as it would be for a physiological case, the measured wave speed is quite clearly less than the Moens-Korteweg theory and it can be shown that the small degree of measured tube ovality explains this.
Anderson
A
A
Department of Mechanical, Materials and Manufacturing Engineering, University of Newcastle upon Tyne.
Johnson
G R
GR
D001783:Blood Flow Velocity; D004548:Elasticity; D006439:Hemodynamics / Q000502:physiology*; D008955:Models, Cardiovascular; D011312:Pressure; D013314:Stress, Mechanical