05/18 - 05/22/2015 Joel Mobley and Cecille Labuda give talks at ASA 169 in Pittsburgh.

Joel Mobley and Cecille Labuda gave talks at the 169th Meeting of the Acoustical Society of America.  Joel's talk was Hot Topics in Physical Acoustics and Cecille's talk was Direct Visualization of Shear Waves in Viscoelastic Fluid Using Microspheres.  The talk abstracts are below.

 

Hot Topics in Physical Acoustics. Joel Mobley

From the astronomical to the molecular, acoustics is central to phenomena across a vast spectrum of length scales. This talk provides an overview of recent developments in physical acoustics across the size continuum, while looking more in depth in three areas. At the larger end of the scale, the generation of the infrasound by cyclonic storms is considered, specifically looking at the infrasonic signatures that can be used to track and characterize these systems. At intermediate length scales, advances in acoustic metamaterial (AM) research are examined. Specific examples will include energy-harvesting metasurfaces and soft matter systems. Moving to the small end of the scale, phoxonic crystals (PxC) are discussed. PxC’s possess both optical and acoustic band gaps and can be used to trap light and sound together, enhancing the strength of acousto-optic interactions.

 

Direct visualization of shear waves in viscoelastic fluid using microspheres. Cecille Labuda, Connor M. Tierney, E. G. Sunethra K. Dayavansha and Joseph R. Gladden.

Wormlike micellar fluids are viscoelastic and can thus support shear waves. Shear waves in 500 mM CTAB-NaSal micellar were visualized by seeding the fluid with microspheres. This method was compared to visualization by observation of birefringence patterns induced by fluid strain in response to shear stresses. Shear speeds measured using both techniques were consistent. Particle displacement was observed to be a sinusoidal function of time and displacement amplitude decreased quadratically with distance from the source. This supports the possibility of using particle amplitude measurements as a measure of attenuation even at low fluid concentration where birefringence visualization techniques fail.