Measurements of Air Concentration and Velocities in a Free Falling Water Jet

The prediction of air entrainment in a free falling water jet (two-phase flow) is affected by large uncertainties. A current research project at the Vienna University of Technology is dealing with this phenomenon by means of experimental tests and CFD-calculations. The experimental investigation was conducted in order to measure the air concentration in such a free falling jet using a fibre-optic probe. The velocity was measured with a high speed camera. The tests were performed on a jet which exits a circular pipe with a diameter of 40 mm. The air concentration was measured transversally at several distances away from the nozzle exit. The test results should provide a data basis for CFD-calculations of the air entrainment in a further research step