TUG-HYDRO-Design:

Viscous Multi-Body Hydrodynamics for Offshore-Tugs in Seaway

Background

The objective of the BMWi-sponsored project TUG-Design is the establishment of a simulation environment that is suited for observing hydrodynamic performance of tug boats. The quintessence of this project is to consider the behaviour and the characteristics of the ship operating in seaway while taking into account the interaction with other bodies (e.g. other tugs, floating platforms), which is important for the assessment of the offshore capability of a tug. For this purpose methods for parametric design description, together with viscous hydrodynamic simulation and static analysis should be developed and combined for practical application.

Methodology

Existing method for viscous calculation will be further developed. FreSCo⁺ will be used for this purpose, which is an in-house CFD-code for viscous calculation based on Reynolds-averaged Navier-Stokes (RANS) equations.

The research areas include:

Seaway Boundary Conditions

For the efficient and flexible computation of the behaviour of floating bodies in seaway environment, the central focus is on the further development of the multi-phase solver FreSCo⁺. To this a module for the coupling between a far-field solution of the pouring wave field and the viscous RANS-solution of the ship's near-field should be refined with regard to industrial applications. Therefore manoeuvring bodies at sea with time-varying encounter-angles can be simulated.

Tug boat operating in rough sea condition

Viscous Multi-Body Hydrodynamics

For the calculation of the hydrodynamic interaction of ships operating nearby, an efficient and implicit coupling of overlapping grids will be implemented. This technique provides the basis for the hydrodynamic optimization of tugs. Furthermore forces of ropes and fenders will be considered in the ship motion simulation.

Multi-body interaction is key to Dynamic Positioning (DP) and handling

Propeller Model

A propeller-model will be established which captures the effect of cycloidal propeller by means of volume forces arising from profile characteristics under dynamic loading. This method is recommended due to its robustness and the expected performance of handling the stretched and unswept cycloidal propeller blades.

Cycloidal propeller to be modelled using coefficient model with overset grid