University of Illinois Urbana-Champaign

Measurement of instantaneous Eulerian acceleration fields by particle-image accelerometry: Methods and accuracy

Christensen, Kenneth T.; Adrian, Ronald J.

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https://hdl.handle.net/2142/267

Description

Title
Measurement of instantaneous Eulerian acceleration fields by particle-image accelerometry: Methods and accuracy
Author(s)
  • Christensen, Kenneth T.
  • Adrian, Ronald J.
Issue Date
2001-12
Keyword(s)
  • boundary layers
  • convection
  • environmental effects
  • experimental fluid mechanics
  • geophysical fluid dynamics
  • microfluidics
  • multiphase flows
  • particulate flows
  • turbulence physics
Abstract
Acceleration is a fundamental quantity in fluid mechanics because it reflects the sum of all forces (pressure and viscous) present within the flow. However, measurements of acceleration have been difficult to achieve relative to the ease with which fluid velocity can be measured. A particle-image accelerometer (PIA) has been developed to measure Eulerian acceleration fields by time-differencing successive measurements of the Eulerian velocity field as measured by particle-image velocimetry (PIV). The measurements can also be made in uniformly translating frames. With current video camera technology, it is often not possible to measure the two velocity fields with a time separation sufficiently small enough to permit accurate finite difference approximation of the time derivative. A two-CCD-camera system has been developed to alleviate this limitation. Polarization filtering is utilized to separate the particle images viewed by each camera. The polarization filtering is achieved using cross-polarized light-sheets and a polarization filter just upstream of the imaging optics of the cameras. In this manner, PIV measurements can be achieved easily at time delays several orders of magnitude smaller than the shutter-time of the CCD cameras. The accuracy of the acceleration measurements is determined by numerical finite differencing errors and random noise and bias errors associated with the measurement of velocity. These errors, and methods of compensating for them, are studied.
Publisher
Department of Theoretical and Applied Mechanics (UIUC)
Series/Report Name or Number
TAM Reports 991
ISSN
0073-5264
Type of Resource
text
Language
en
Permalink
http://hdl.handle.net/2142/267

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Technical Reports - Theoretical and Applied Mechanics (TAM) PRIMARY
TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.