In this work, we investigate experimentally and numerically the hydrodynamics induced by a bubble plume introduced at the centre of a rectangular tank through a needle single point sparger. The gas-liquid flow in such systems is inherently unsteady. Particle Image Velocimetry (PIV) was used to experimentally determine the transient velocity fields in the system. For this gas-liquid flow system, both the fluctuating and mean liquid velocities were determined experimentally by 3D and 2D PIV. The behavior of the system was simulated in FLUENT 6.3.26 using a two fluid Euler-Lagrangian model with a constant bubble size of 5 mm. Water is treated as the continuous phase and the gas bubbles are treated as the dispersed phase. The motion of the bubbles renders the flow turbulent and this effect is captured by the standard k-ε turbulence model. In addition to this, the prediction obtained using laminar model is compared with turbulent model. The temporal prediction of the flow field is compared with experimental observations. For the case of centre injection of bubbles, we conclude that the velocity at a point does show sustained periodic oscillations in time. © 2010 American Institute of Physics.