Abstract: Turbulent flows generated by double-layer transverse oscillation grids are used to study the turbulence characteristics of pure fresh water and salt water stratified with different salinity gradients. Time variations in turbulence and salinity are measured simultaneously using an acoustic Doppler velocimeter and a multi-channel micro-salinity meter that was designed in our laboratory. This paper focuses on an analysis of the effects of salinity stratification on turbulent characteristics such as root mean square velocity, turbulence intensity, and turbulent kinetic energy spectrum. The results show that the stratification suppresses turbulences and weakens turbulence intensity, and a larger salinity gradient leads to more suppression of turbulences. A dimensionless stratification parameter is defined to represent the stratification degree of a water body under oscillating grid turbulences. Our analysis reveals the turbulence suppression rate increases as this parameter is increased, and a relationship between them is obtained through data fitting.

Key words: salinity, stratification, turbulence characteristic, oscillating grid, micro salinity sensor