Title:	Scale resolved flow simulations in ship hydrodynamics
DNr:	SNIC 2022/5-35
Project Type:	SNIC Medium Compute
Principal Investigator:	Rickard Bensow <rickard.bensow@chalmers.se>
Affiliation:	Chalmers tekniska högskola
Duration:	2022-02-01 – 2023-02-01
Classification:	20303
Keywords:

Abstract

There are several complex problems in ship hydrodynamics that require detailed information on the flow field, thus necessitating the use of scale resolved modelling approaches. The large spatial scales of a ship or underwater body are however such that the complete problem can not yet be treated. We will here look at a few limited problems where advanced simulation methodologies are needed to advance the understanding. The first concerns the flow over a rough surface. Already a new built vessel has a somewhat rough surface as the hull paint can not be applied completely smoothly, and the problem gets worse as wear and fouling deteriorates the surface. Wall-modelled LES will be performed for a series of test cases for non-equilibrium boundary layers developed within an international working group on this topic. The objectives are both to jointly improve understanding of the flow development as well as develop better models for flow modelling over rough surfaces. The second concerns simulation of hydroacoustic characteristics of underwater bodies and their radiated sound. Canonical building block flows will be studied, both in terms of flow dynamics and scales as well as the radiated sound, primarily using resolved LES. The objectives are to develop guidelines for choice of simulation approaches, problem set-up, and mesh resolution requirements for these types of problems. A third concern relates to cavitation nuisance, such as hull pressure pulses and radiated noise. Here, the detailed cavity dynamics in a marine propulsion system needs to be resolved in the simulation and the transient pressure field on the ship structure and in the surrounding fluid is sampled and analysed. Demanding DES or WMLES are needed for the full ship configuration, resolving the internal structure of the developing cavities on the propeller blades as well as the trailing tip vortex cavitation. Funding for the research comes from the Chalmers Areas of Advance, the Swedish Transportation Agency, Kongsberg Maritime Sweden AB, the Swedish Defense Material Administration (FMV) and Saab Dynamics. This project expands on the activities in the previous project (SNIC 2021/5-61) by the third activity, where a new PhD student will start using the project. The (WM)LES activities related to non-equilibrium boundary layer flows will also be intensified during the spring of 2022.