Author(s): Papakonstantis Ilias; Kampourelli Maria; Christodoulou George
Linked Author(s): Ilias Papakonstantis, George Christodoulou
Keywords: Turbulent jets; Buoyant jets; Negative buoyancy; Dilution; Inclination angle; Initial height of rise; Final height of rise
Abstract: This paper presents new experimental results of an on-going experimental and computational study on inclined turbulent jets with negative buoyancy in a homogeneous and calm environment. The initial height of rise which is reached by the jet at the initiation of the flow and the final height of rise which is observed at steady state, are measured for four different discharge angles, namely φ= 45o, 60o, 75o and 90o to the horizontal. The experiments are carried out in a large tank 3. 0 m long x 1. 5 m wide x 1. 0 m deep, filled with tap water. The dense jet consists of a saltwater solution, with density difference 2% – 3. 5% higher than ambient. The jet is colored with red dye and its evolution is recorded by means of a video camera. The densimetric Froude number at the source ranges between 20 and 60 whereas the Reynolds number at the source is generally higher than 6000 to ensure that the flow is fully turbulent. A new technique is employed for correcting the observed heights, as important errors maybe introduced due to the location of the grid, the position of the camera and the water refraction. Results are given in non-dimensional form for the initial and final height of rise confirming earlier theoretical considerations. Simple expressions are given for the computation of the initial and final height of rise in terms of the densimetric Froude number and the nozzle diameter. The effect of the inclination angle on the height of rise is investigated. The initial height of rise is found to increase with increasing the inclination angle to the horizontal up to φ=90ο, whereas the final height of rise increases with increasing angle and then decreases with a maximum value near φ=75ο. Finally, the experimental results are compared to those of previous investigations.
Year: 2007