Experimental and numerical investigation of the gap flow between a pusher and a barge in deep and shallow water

Abstract

The flow in the gap between a pusher boat and a barge of a conventional inland waterway convoy was experimentally and numerically investigated to gain insight into the complex flow pattern and to provide benchmark data for validation of an adequate turbulence model. Two water depths were considered, corresponding to deep water and moderately shallow water conditions. Both cases highlighted the extremely unsteady non-uniform flow pattern in the gap. The collected data were subsequently used to assess a numerical method based on solving the Reynolds-averaged Navier–Stokes (RANS) equations and the Improved Delayed Detached Eddy Simulation (IDDES) technique. Generally, our numerical predictions compared favorably to the experimental data; however, the IDDES method proved to be more accurate, especially in the prediction of the velocity field in the gap region. The IDDES technique was then used to analyze the flow in water depth to draft ratios h/T of 2.14, 1.5, and 1.2. At h/T=1.2, comparatively larger recirculation zones and a massive increase in resistance were observed. Additionally, to quantify the influence of the gap between pusher and barge on resistance in shallow waters, we modified our model by simply covering the gap and then analyzing this modified model by carrying out an additional simulation at h/T=1.2. Covering the gap reduced the overall longitudinal hydrodynamic force acting on the convoy by about 6.5 %.