Abstract: Eighteen experimental cases for the buoyant plume were conducted in linearly stratified saltwater. The particle image velocimetry (PIV) technique was used to acquire flow fields of plumes in high spatial and temporal resolutions. A new formula for maximum transported mass of buoyant plumes in stratified fluids was proposed. The process for entrainment and mass transport of plumes were analyzed quantitatively. Results show that the entrainment coefficient αe increases gradually along the jetting direction from the source, fluctuates at 0.11 from 0.3Zmax to 0.5Zmax (Zmax is the maximum penetration distance) and then decreases gradually to negative. The buoyant plume which entrains ambient fluids from the plume stem is transported to －Zmax along the jetting direction and its vertical mass flux reaches the maximum at about －0.65Zmax. The mixed plume finally spreads to surroundings at the neutral buoyancy layer. The maximum transported mass is determined by the buoyancy flux, the buoyancy frequency and the environment density at the same level. The calculation error due to pseudo turbulence caused by variations of the refractive index within the stratified fluid is about 3%, so the influence of refractive index is negligible.

Key words: buoyant plume, linear stratification, particle image velocimetry (PIV), maximum transported mass, pseudo turbulence