Visualization of grid-generated turbulence in He II using PTV

Cryogenic Engineering Conference 2017

材料科学;物理学

Mastracci, B.^1,2 ; Guo, W.^1,2

National High Magnetic Field Laboratory, Florida State University, 1800 E Paul Dirac Drive, Tallahassee

FL

32310, United States^1

Department of Mechanical Engineering, Florida State University, 2525 Pottsdamer Street, Tallahassee

FL

32310, United States^2

关键词: Constant velocities;    Energy statistics;    Grid-generated turbulence;    High Reynolds number;    Particle tracking velocimetry;    Quantized vortex;    Scientific imaging;    Turbulent velocity fields;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/278/1/012081/pdf
DOI  :  10.1088/1757-899X/278/1/012081

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

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 × 16 × 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 600 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.