The present research investigates the hydrodynamic forces and moments and the flow pattern near the hull of an escort tug at steady oblique flow conditions. An escort tug is modelled and numerical simulations have been carried out using a commercial RANS solver. In the simulations, the viscous flow field is calculated by the finite volume method, adapting the k-ε turbulence model. Free surface is modeled using the Volume of Fluid (VOF) approach for calm water condition. The hull is assumed fixed in space with an even keel. Grid dependency studies are conducted to obtain insight into the reliability and accuracy of the results. Flow velocities around the escort tug as well as integral variables are computed at different Froude numbers and compared to the corresponding measurement data available in the public domain. The measurements was completed using a Planar Motion Mechanism (PMM) apparatus to measure the resistance, side force and yaw moment of the tug hull. Additionally, the velocity distributions on the upstream and downstream sides of the tug were measured by Particle Image Velocimetry (PIV).
The measurements and simulations have been completed at one draft, and at 15°, 30° and 45° inflow conditions. A reasonable agreement has been obtained between the predicted axial and lateral forces and the corresponding measurements. The flow pattern and the velocity distribution at different drift angle are comparable with the measurements. The variation of the pattern of flow separation at the suction side of the hull at different yaw angle is also analyzed and presented.
Numerical analysis of unsteady hydrodynamic performance of pump-jet propulsor in oblique flow
