Time-Supersampling 3D-PIV Measurements by Vortex-in-Cell Simulation

Time-Supersampling 3D-PIV Measurements by Vortex-in-Cell Simulation

Schneiders, J.F.G.

Dwight, R.P. (mentor)
Scarano, F. (mentor)

Aerospace Engineering

Aerodynamics

2014-02-12

Measurement rate limitations of time-resolved 3D-3C velocity measurements by tomographic PIV limit application of the technique to small measurement volumes and low speed flows (~10 m/s). To reduce the challenging repetition rate requirements historically set by the Nyquist criterion, in the present thesis work a novel method is proposed, combining PIV measurements with numerical simulation of the vorticity transport equation using a hybrid vortex particle discretization. The principle of the time-supersampling method is that the spatial information available by the measurements can be leveraged to increase the temporal-resolution. The solution of the governing equations is based on the Vortex-in-Cell (VIC) method and the unsteady numerical simulation of the temporal evolution of the measured flow is applied within the 3D measurement domain. Both forward and backward time-integration is performed between pairs of consecutive measurements. The accuracy of the proposed time-supersampling method is studied with two experimental datasets obtained from time-resolved tomographic PIV measurements: a turbulent wake, and a circular jet. The results are compared to linear interpolation, advection-based supersampling, and measurement data at high sampling rate. In both flows the ability to reconstruct detailed temporal dynamics from data sampled at a rate far below the Nyquist frequency is demonstrated. The study demonstrates that measurement rate requirements can be strongly reduced when the measurements are super-sampled with the proposed time-supersampling method, thereby extending the range of application of tomographic PIV. In addition, an alternative application of the approach in the field of noise reduction and application to instantaneous measurements is illustrated. The latter can on the one hand allow for a significantly improved predictor for fluid trajectory correlation methods and on the other hand when validated can pose a radically simplified approach for calculation of the instantaneous and unsteady pressure field from single tomographic PIV snapshots, in comparison to multi-pulse systems.

Tomographic PIV
Navier-Stokes
Particle Image Velocimetry
CFD
Vortex-in-Cell
Turbulence
Unsteady
Temporal resolution
Data Assimilation

http://resolver.tudelft.nl/uuid:2e3c46fa-175d-4580-a176-8f6c8c5425e9

Student theses

master thesis

(c) 2014 Schneiders, J.F.G.