Experiments in Fluids

, 57:138 | Cite as

Combined density gradient and velocity field measurements in transient flows by means of Differential Interferometry and Long-range \(\varvec{\upmu }\)PIV

  • S. Kordel
  • T. Nowak
  • R. Skoda
  • J. Hussong
Research Article


In the present study, Long-range Microparticle Image Velocimetry (\(\upmu\)PIV) and Differential Interferometry (DI) are combined in a novel manner to enable both velocity and depth-integrated density gradient field measurements using the same laser pulse for both recordings. In the present work, temperature-driven boundary layer flows could be successfully determined to an accuracy of \(\Updelta T=0.17\,\hbox {K}\) with a spatial resolution of \(405\,\upmu \hbox {m}\) for interference and \(101\,\upmu \hbox {m}\) for \(\upmu\)PIV measurements. The DI measurements are refraction compensated, and both temperature and velocity fields are compared with results from numerical simulations.


Particle Image Velocimetry Particle Tracking Velocimetry Refractive Index Gradient Velocity Field Measurement Brass Plate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols


Fringe orientation angle

\(\bar{\rho }\)

Depth-averaged density


Divergence angle of Wollaston Prism


Standard deviation

\(\delta _{ref}\)

Deviation related to reference density gradient

\(\eta ,\zeta\)

Cartesian coord. aligned with reference fringes


Wavelength of light



\(\Updelta S\)

Fringe shift

\(\Updelta x\)

Distance along x-axis

\(\Updelta x_{r}\)

Refraction-induced light ray shift

\(\Updelta y\)

Distance along y-axis


Measurement volume thickness


Neighbouring light ray distance


Interframing time


Focal length


Laser intensity


Gladstone Dale constant


Distance between test section and lens


Nusselt number




Homogeneous fringe spacing








Distance between Wollaston prism and focal point



This research was financially supported by DFG (HU 2264/1-1).


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Chair of Fluid MachineryRuhr-University BochumBochumGermany

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