Promotie B.F.A. Wieneke: PIV

12 december 2017 12:30 - Locatie: Aula, TU Delft - Door: webredactie

Particle Image Velocimetry and its Uncertainty. Promotor: Prof.dr. F. Scarano (LR).

The fundamental properties of measured flow fields using the particle imaging velocimetry (PIV) measurement technique have been investigated. PIV processing can be analyzed using a linear filter model, i.e. assuming that the computed displacement field is the result of some spatial filtering of the underlying true flow field given a particular shape of the filter function. From such a mathematical framework, relationships are derived between the underlying filter function, wavelength response function (MTF) and response to a step function, power spectral density, and spatial autocorrelation of filter function and noise. A new definition of a spatial resolution is provided.

The most important error sources in PIV are discussed and an uncertainty quantification method based on correlation statistics is derived, showing good sensitivity to a variety of error sources. Instantaneous local velocity uncertainties are propagated for derived instantaneous and statistical quantities like vorticity, averages, Reynolds stresses and others.

A new anisotropic denoising scheme as a post-processing step is presented which uses the uncertainties comparing to the local flow gradients in order to devise an optimal filter kernel for reducing the noise without suppressing true small-scale flow fluctuations.

For Stereo-PIV and volumetric PIV/PTV, an accurate perspective calibration is mandatory. A self-calibration technique is described for planar and volumetric PIV.

Finally, an iterative method for reconstructing particles (IPR) in a volume is developed, which is the basis for the recently introduced highly accurate Shake-the-Box (STB) particle tracking method.

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