title: Schlieren visualization of ultrasonic standing waves in mm-sized chambers for ultrasonic particle manipulation.
abstract: BACKGROUND
  For the design and characterization of ultrasonic particle manipulation devices the pressure field in the fluid cavity is of great interest. The schlieren method provides an optical tool for the visualization of such pressure fields. Due to its purely optical nature this experimental method has got some unique advantages compared to methods like particle tracking.
  
  
  RESULTS
  A vertical schlieren setup and an investigation with the same of a mm-sized chamber used to agglomerate particles are presented here. The schlieren images show a two-dimensional representation of the whole pressure distribution recorded simultaneously with a good resolution in time. The gained description of the pressure field is shown to be in agreement with a numerical simulation. Thermal effects as well as streaming effects are shown.
  
  
  CONCLUSIONS
  The results show the great potential of schlieren visualization to investigate ultrasonic particle manipulation devices. Visualized are pressure fields, acoustic streaming, temperature effects and effects caused by fluid volumes of different density.
authors.affiliation: Department of Mechanical and Process Engineering, Institute of Mechanical Systems, ETH Zurich, Tannenstrasse 3, Zurich, Switzerland. dirk.moeller@imes.mavt.ethz.ch
authors.forename: Dirk
authors.initials: D
authors.lastname: Möller
authors.forename: Nicolas
authors.initials: N
authors.lastname: Degen
authors.forename: Jurg
authors.initials: J
authors.lastname: Dual
mesh_terms: D000162:Acoustics; D003198:Computer Simulation; D055620:Optical Phenomena; D010316:Particle Size; D011312:Pressure; D013997:Time Factors; D014465:Ultrasonics / Q000295:instrumentation* / Q000379:methods*