Jul 9 – 13, 2017
Monona Terrace Community and Convention Center
US/Central timezone

Visualization of grid-generated turbulence in He II using PTV

Jul 11, 2017, 4:15 PM
15m
Madison Ballroom BC

Madison Ballroom BC

Speaker

Brian Mastracci (Florida State University, National High Magnetic Field Laboratory)

Description

Due to its low viscosity, cryogenic He II has potential use for simulating large-scale, high Reynolds number turbulent flow in a compact and efficient apparatus. To realize this potential, the behavior of the fluid in the simplest cases, such as turbulence generated by flow past a mesh grid, must be well understood. We have designed, constructed, and commissioned an apparatus to visualize the evolution of turbulence in the wake of a mesh grid towed through He II. Visualization is accomplished using the particle tracking velocimetry (PTV) technique, where µm-sized tracer particles are introduced to the flow, illuminated with a planar laser sheet, and recorded by a scientific imaging camera; the particles move with the fluid, and tracking their motion with a computer algorithm results in a complete map of the turbulent velocity field in the imaging region. In our experiment, this region is inside a carefully designed He II filled cast acrylic channel measuring approximately 16 x 16 x 330 mm. One of three different grids, which have mesh numbers M = 3, 3.75, or 5 mm, can be attached to the pulling system which moves it through the channel with constant velocity up to 500 mm/s. The consequent motion of the solidified deuterium tracer particles is used to investigate the energy statistics, effective kinematic viscosity, and quantized vortex dynamics in turbulent He II.

Primary author

Brian Mastracci (Florida State University, National High Magnetic Field Laboratory)

Co-author

Dr Wei Guo (Florida State University, National High Magnetic Field Laboratory)

Presentation materials