Volumetric flow prediction using multiple plane particle image velocimetry
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Abstract
This thesis presents an approach to predicting a 3-dimensional, 3-component
velocity field of a fluid
ow that possesses a homogeneous dimension. At the
core of this approach is the technique of stochastic estimation, which is commonly
used to combine a small number of instantaneous measurements with
previously acquired statistical data, to produce a prediction of the flow over
a large number of locations. In the proposed technique, particle image velocimetry
(PIV) is used to provide measurements for the stochastic estimation
procedure, and the statistical stationarity along the homogeneous dimension of the flow is exploited to extend the use of stochastic estimation to provide a
full volumetric prediction.
The first section concerns the prediction performance of stochastic estimation.
It is shown how the traditional approach to stochastic estimation is
equivalent to ordinary least squares (OLS) regression. The properties of OLS,
previously unconsidered in stochastic estimation literature, are presented, and
shown to have a number of practical uses in the design and implementation
of stochastic estimation procedures. Several alternative approaches to flow
prediction are selected for further study, and their performance is compared
in a series of trials, based on data from a numerically simulated channel flow.
The newly-introduced biased techniques are shown to outperform or equal the accuracy of the stochastic estimation techniques across the entire range of
parameters under investigation.
The second section introduces the proposed volumetric prediction technique.
A proof of concept is obtained using volumetric data from the simulated
channel flow, and the resulting predictions show excellent quantitative
and qualitative agreement with the original data. The predicted vortex ring
data compares favourably with previous theoretical and experimental studies,
and visualisation of the volumetric data appears to show the existence of
secondary vortical structures around the outside of the ring core, which have
previously only been observed in numerical simulations