Quantification of Turbulence in Cryogenic Liquid Pool Using High Speed Flow Visualization

When a cryogenic liquid is released on water, turbulence is generated in the cryogenic liquid pool due to rapid vaporisation. This turbulence is characterized as interfacial turbulence occurring due to thermal convection in water-cryogen interface.  The quantification of turbulence in the cryogenic liquid pool, when it comes in contact with water, is an important step in determining the amount of vapor produced from the cryogenic liquid pool. The current study focusses on the measurement of liquid phase turbulence using high speed flow visualization. An experiment is conducted by releasing different amounts of liquid nitrogen instantaneously on water. A high speed camera is operated at a frame speed of 5000 frames/second and a shutter speed of 1/6000 seconds to provide a visual record of the interfacial physics.  A frame by frame capture of the advective transport of cryogenic vapor bubble traversing through the liquid is captured and reconstructed using image processing softwares to obtain information on velocity components. The numerical results obtained from image processing are used to determine the turbulence parameters like turbulent intensity, turbulent kinetic energy and eddy dissipation rate. The qualitative results provide information on the wavy structures called ‘thermals’ which is characteristic of turbulent convection. The thermals are found to act as catalyst in increasing heat transfer and turbulence between water and cryogenic pool. In addition to it, the turbulence parameters are found to be dependent on the height of cryogenic liquid. The current study enhances the understanding of the nature of turbulence and its magnitude for implementing in source term modelling of LNG releases on water.