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@conference{Rotte2017,

title = {On the Turbulence Modelling for an Air Cavity Interface},

author = {Rotte, G. and Kerkvliet, M. and Van Terwisga, T.J.C.},

url = {http://www.marin.nl/web/Publications/Publication-items/On-the-Turbulence-Modelling-for-an-Air-Cavity-Interface.htm},

year  = {2017},

date = {2017-10-03},

booktitle = {20th Numerical Towing Tank Symposium (NuTTS), Wageningen, The Netherlands},

abstract = {The use of air lubrication techniques can significantly reduce a ship’s fuel consumption. One of the most promising techniques applicable to ships is the external air cavity technique. An external cavity is created beneath the ship’s hull with the help of a cavitator, which is located directly upstream of an air injection point (figure 1a). The cavitator is extended in the span-wise direction and typically has a rectangular or triangular cross section. It is used to separate the mean water flow from the hull, thereby providing a stable air layer. Air cavity applications are claimed to lead to propulsive power reduction percentages of 10-20% by reducing the ship’s frictional drag. However, a complete understanding of the influence that the ship’s hull form has on the relevant twophase flow physics and thereby also on the length and stability of the air cavities is still lacking. This inability to predict the air cavity characteristics hampers the application of air cavity techniques in the shipping industry. Multiphase CFD methods can help us to gain a better understanding of the relevant physics.

This article aims to link the physical modelling of the relevant phenomena to their numerical modelling, with an emphasis on the modelling of the re-entrant jet mechanism with a RaNS turbulence model. The article is based on the available literature in the public domain and on knowledge gained from research projects carried out at Delft University of Technology and at the Maritime Research Institute Netherlands (MARIN).},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{Negrato2017b,

title = {Analysis of Hydrofoil Cavitation using Proper Orthogonal Decomposition},

author = {Negrato, C., Van Terwisga, T.J.C. and Bensow, R.},

url = {http://www.marin.nl/web/Publications/Publication-items/Analysis-of-Hydrofoil-Cavitation-using-Proper-Orthogonal-Decomposition.htm},

year  = {2017},

date = {2017-10-03},

booktitle = {20th Numerical Towing Tank Symposium (NuTTS), Wageningen, The Netherlands},

abstract = {Cavitation is the change of phase from liquid to vapor when the pressure falls below the saturation pressure. For marine propellers, occurrence of cavitation is accepted on modern designs. However, there is a need to keep cavitation under control, because its extent can influence propeller efficiency, as well as lead to undesired phenomena such as increased noise and erosion. To understand the dynamics of cavitation, researchers often focus on cavitation on simpler geometries, such as hydrofoils. In this work, the test case consists on a two dimensional NACA0015 hydrofoil. The results from a viscous flow simulation are considered here; the scope is to gain additional insight into cavitation dynamics in a regime of cavity shedding, by applying a Proper Orthogonal Decomposition (POD) technique. POD is used for analysis of experimental data or CFD results and relies on the approximation of the flow field by a linear combination of basis functions which are representative of flow structures.

This paper provides a description of the numerical setup and the basic theoretical background for POD and shows the outcome of orthogonal decomposition for two scalar fields: the vapor volume fraction and the pressure coefficient.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}