Simulating propeller and Propeller-Hull Interaction in OpenFOAM

University essay from KTH/Marina system

Abstract:

This is a master’s thesis performed at the Department of Shipping and Marine Technology research group in Hydrodynamics at Chalmers University of Technology and is written for the Center for Naval Architecture at the Royal Institute of Technology, KTH.In order to meet increased requirements on efficient ship propulsions with low noise level, it is important to consider the complete system with both the hull and the propeller in the simulation.OpenFOAM (Open Field Operation and Manipulation) provides different techniques to simulate a rotating propeller with different physical and computational properties. MRF (The Multiple Reference Frame Model) is, perhaps, the easiest way but is a computationally efficient technique to model a rotating frame of reference. The sliding grid techniques provide the more complex way to simulate the propeller and its surrounding region, rotating and interpolate on interface for transient effects. AMI, Arbitrary Mesh Interface, is a sliding grid implementation which is available in the recent versions of OpenFOAM, introduced in the official releases after v2.1.0.In this study, the main objective is to compare these two techniques, MRF and AMI, to perform the open water characteristics of the propeller with the Reynolds-Averaged Navier-Stokes equation computations (RANS) and study the accuracy in parallel performance and the benefits of each approach.More specifically, a self-propelled ship is simulated to study the interaction between the hull and propeller. In order to simplify and decrease the computational complexity the free surface is not considered. The ship under investigation is a 7000 DWT chemical tanker which is subject of a collaborative R&D project called STREAMLINE, strategic research for innovative marine propulsion concepts. In self-propelled condition, the transient forces on the propeller shall be evaluated. This study investigates the results of the experimental work with advanced CFD for accurate analysis and design of the propulsion. In this thesis, all simulations are conducted by using parallel computing. Therefore, a scalability analysis is studied to find out how to affect the average computational time by using different number of nodes.

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