Acoustic quasi-modes in slowly varying cylindrical tubes

Waveguide Simulation of Non-Cylindrical Acoustic Tubes

Acoustic modes in a duct with slowly varying impedance and non-uniform mean flow and temperature

Noise from the auxiliary power unit (APU) is becoming an increasingly important aircraft design constraint because of the noise exposure during ground operations (“ramp-noise”). Reduction of noise may be achieved by liners in the exhaust duct. In this paper, we will consider the propagation of sound through the APU exhaust duct, which is typically straight with an axially varying liner depth, a...

Very Slowly Varying Functions

A real-valued function f of a real variable is said to be (p-slowly varying ((p-s .v.) if limn_ . rp (x) [ f (x + a) f (x)] = 0 for each a. It is said to be uniformly 9-slowly varying (u . (P-s .v .) if limn-. . sup, e r rp(x) ; f (x-a) f (x)I =0 for every bounded interval I. It is supposed throughout that rp is positive and increasing . It is proved that if w increases rapidly enough, then eve...

Navier-Stokes Flow in Cylindrical Elastic Tubes

Analytical expressions correlating the volumetric flow rate to the inlet and outlet pressures are derived for the time-independent flow of Newtonian fluids in cylindrically-shaped elastic tubes using a one-dimensional Navier-Stokes flow model with two pressure-area constitutive relations. These expressions for elastic tubes are the equivalent of Poiseuille and Poiseuille-type expressions for ri...

On Slowly Varying Stokes Waves

ON SLOWLY VARYING STOKES WAVES by VINCENT HWA-HING CHU In this thesis investigations are made on the theory of a train of slowly modulated gravity waves propagating over uneven bottom topography. The primary object is to study the interplay of amplitude dispersion the frequency dispersion in waves on the surface of water where the depth is not too shallow compared to a typical wave length. The ...