Pouring time into space

Pouring time into space

Schneiders, J.F.G.
Azijli, I.
Scarano, F.
Dwight, R.P.

Aerospace Engineering

Aerodynamics, Wind Energy & Propulsion

2015-12-31

A method is proposed to reconstruct instantaneous velocity from time-resolved tomographic PTV, employing both instantaneous velocity and velocity material derivative. This improves upon current techniques by not only including penalization of velocity divergence, but also requiring consistency with the temporal derivative of the PTV particle tracks. Hence the procedure is christened as pouring time into space. The aim of the proposed technique is to increase spatial resolution of tomographic PTV in cases where it is limited by the seeding concentration. An inverse problem is solved to find the velocity field that minimizes a cost function including next to instantaneous velocity and its divergence, also the velocity material derivative. The velocity and its material derivative are related through the vorticity transport equation and the problem is minimized using the L-BFGS algorithm, where gradients are evaluated efficiently using an adjoint implementation of the method. The procedure is assessed numerically using results from a simulated PTV experiment in a turbulent boundary layer from DNS, and experimentally using tomographic PIV measurements in a jet flow. Both the numerical and experimental assessment show that the proposed technique yields improved accuracy of the velocity field in between the measured points over penalization of divergence only, thereby demonstrating that the temporal information available in time-resolved tomographic PTV can be leveraged to increase reconstruction quality of instantaneous velocity.

http://resolver.tudelft.nl/uuid:9ee747d8-637a-4074-81fa-b00da14e723b

11th International Symposium on Particle Image Velocimetry, PIV15, Santa Barbara, CA, USA, September 14-16 2015; Authors version

Institutional Repository

conference paper

(c) 2015 The Author(s)