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Full-Text Articles in Engineering
A Time-Resolved Method For Nonlinear Ultrasonic Measurements, Stephen D. Holland, Wolfgang Sachse
A Time-Resolved Method For Nonlinear Ultrasonic Measurements, Stephen D. Holland, Wolfgang Sachse
Stephen D. Holland
We describe a time-resolved method for measuring nonlinear ultrasonic phenomena. Current approaches rely on a narrowband measurement of harmonic generation to identify and characterize nonlinearity. Concomitant with these techniques is poor time resolution. We address this limitation with a hybrid narrowband/broadband approach that provides simultaneous time resolution and harmonic isolation for the measurement of weak nonlinearites. We discuss applications and present demonstrative results showing harmonic generation both in water and at a dry contact aluminum-aluminum interface.
Statistical Modeling Of Sprays Using The Droplet Distribution Function, Shankar Subramaniam
Statistical Modeling Of Sprays Using The Droplet Distribution Function, Shankar Subramaniam
Shankar Subramaniam
The theoretical foundations of a statistical spray modeling approach based on the droplet distribution function ~ddf!, which was originally proposed by Williams @Phys. Fluids 1, 541 ~1958!#, are established. The equation governing the ddf evolution is derived using an alternative approach. The unclosed terms in the ddf evolution equation are precisely defined, and the regime of applicability of current models is discussed. The theory of point processes is used to rigorously establish the existence of a disintegration of the ddf in terms of a spray intensity, which is the density of expected number of spray droplets in physical space, and …
Rough Wall Modification Of Two-Layer K-E, Paul A. Durbin, G. Medic, J.-M. Seo, J. K. Eaton, S. Song
Rough Wall Modification Of Two-Layer K-E, Paul A. Durbin, G. Medic, J.-M. Seo, J. K. Eaton, S. Song
Paul A. Durbin
A formulation is developed to apply the two-layer k-ε model to rough surfaces. The approach involves modifying the ℓv formula and the boundary condition on k. A hydrodynamic roughness length is introduced and related to the geometrical roughness through a calibration procedure. An experiment has been conducted to test the model. It provides data on flow over a ramp with and without surface roughness.