Spreading of round dense jets impinging on a horizontal bottom

The radial spreading of density currents arising from the impingement of submerged round turbulent dense jets on a horizontal bottom is investigated. Experiments were conducted for spreading due to (i) the return on the bottom of negatively buoyant jets discharged upwards at four different angles, namely 45°, 60°, 75° and 85° to the horizontal and (ii) the impingement of positively buoyant jets discharged horizontally or vertically downwards to the bottom from a submerged nozzle. The jet fluid was colored saltwater solution issuing at a constant rate in a calm freshwater ambient and the spreading was recorded by means of a video camera. For the inclined negatively buoyant jets and the vertical positively buoyant ones the outer visual boundary of the density current is found to be almost circular. The radial distance from the impingement point to the outer boundary is estimated and found to correlate with time to a power of about 1/2, indicating a balance between buoyancy and drag forces. The radial distance is normalized by time and by the initial or local jet flow parameters and its variation with the discharge angle and the densimetric Froude number is presented.