Some properties of the Persian Gulf outflow from field observations and some laboratory simulations

This paper investigates the behavior of a gravity current as it moves over a sill and becomes trapped at the bottom of sloped topography. To analyze this, we conducted numerous experiments varying reduced gravity, dense water volume, and rotation table frequency. The experiments cover ranges of 0.02 < Fr < 2 and 0.04 < Ro < 0.4. Three flow regimes were identified: laminar, eddy, and laminar-eddy. The eddy regime occurs when the Rossby number is less than 0.05.
The Persian Gulf outflow exhibits this gravity current behavior due to density differences between the Persian Gulf and the Oman Sea. Observational data collected by ROPME in 1992 were used to estimate outflow parameters. Reduced gravity values are estimated at 0.02 m/s² in winter and 0.015 m/s² in summer, with trapped current widths of 20 km and 24 km, respectively. The Rossby and Froude numbers are approximately 0.1 and 0.074, and the Burger number is about 1, indicating that both stratification and rotation significantly influence the outflow. Applying our experimental results to the Persian Gulf outflow shows that the experiments effectively represent the natural flow due to similar dimensionless parameters (Rossby and Froude numbers). Using empirical equations derived from the laboratory, the Nof speed (C_Nof) of the outflow was calculated as 0.7 in winter and 0.67 in summer, highlighting the strong influence of rotational effects on this flow.