The turbulent dissipation rate from PIV measurements etc15 Tracking Number 479Presentation: Session: Multiphase and non-Newtonian flows 4 Room: Room D Session start: 10:30 Fri 28 Aug 2015 Guus Bertens a.c.m.bertens@student.tue.nl Affifliation: Physics Department Eindhoven University of Technology Dennies van der Voort d.d.v.d.voort@tue.nl Affifliation: Physics Department Eindhoven University of Technology Willem van de Water w.v.d.water@tue.nl Affifliation: Physics Department Eindhoven University of Technology Topics: - Large eddy simulation and related techniques Abstract: The result of a particle-image velocimetry (PIV) measurement is a velocity field averaged over interrogation windows. This severely affects the measurement of small-scale turbulence quantities when the interrogation window size is much larger than the smallest length scale in turbulence. A direct measurement of the dissipation rate demands the measurement of gradients of the velocity field, which are now underestimated because the small-scale motion is not resolved. A popular procedure is to relate the statistical properties of the measured, but underresolved gradients to those of the true ones, invoking a large-eddy argument [3]. We show that the used proportionality constant, the Smagorinsky constant, should depend on the window overlap, on the used elements of the strain tensor, and on the way in which derivatives are approximated |