Experimental characterization of air-entrainment in a plunging jet

This paper presents a detailed experimental study of a plunging jet on a free liquid surface. An experimental characterization facility is designed and constructed for generating a vertical round water jet impinging on a free surface of a pool. The experimental analysis focuses on the jet penetration depth, its relation to impact velocity Vj and free jet falling length Lj. The results obtained are compared with previous studies. The flowmap for four different regimes, in terms of impact jet velocity is obtained. The details of the two-dimensional velocity field below the pool liquid free surface under a no-entrainment regime, are obtained using Particle Image Velocimetry (PIV) and reveal the spatial extent of the entrained region. The initial impact process and air cavity features are also investigated and compared with previous semi-theoretical results.