Measurement of laminar,transitional and turbulent pipe flow using Stereoscopic-PIV |
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Authors: | C W H van Doorne J Westerweel |
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Institution: | (1) J.M. Burgers Center for Fluid Dynamics, Laboratory for Aero- and Hydrodynamics, Delft University of Technology, Leeghwaterstraat 21, 2628 CA Delft, The Netherlands;(2) Present address: Shell Global Solutions International BV, P.O. Box 38000, 1030 BN Amsterdam, The Netherlands |
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Abstract: | Stereoscopic particle image velocimetry (SPIV) is applied to measure the instantaneous three component velocity field of pipe
flow over the full circular cross-section of the pipe. The light sheet is oriented perpendicular to the main flow direction,
and therefore the flow structures are advected through the measurement plane by the mean flow. Applying Taylor’s hypothesis,
the 3D flow field is reconstructed from the sequence of recorded vector fields. The large out-of-plane motion in this configuration
puts a strong constraint on the recorded particle displacements, which limits the measurement accuracy. The light sheet thickness
becomes an important parameter that determines the balance between the spatial resolution and signal to noise ratio. It is
further demonstrated that so-called registration errors, which result from a small misalignment between the laser light sheet
and the calibration target, easily become the predominant error in SPIV measurements. Measurements in laminar and turbulent
pipe flow are compared to well established direct numerical simulations, and the accuracy of the instantaneous velocity vectors
is found to be better than 1% of the mean axial velocity. This is sufficient to resolve the secondary flow patterns in transitional
pipe flow, which are an order of magnitude smaller than the mean flow. |
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