An experimental investigation into the surface and hydrodynamic characteristics of marine coatings with mimicked hull roughness ranges

Abstract

There are limited scientific data on contributors to the added drag of in-service ships, represented by modern-day coating roughness and biofouling, either separately or combined. This study aimed to gain an insight into roughness and hydrodynamic performance of typical coatings under in-service conditions of roughened ships' hull surfaces. Comprehensive and systematic experimental data on the boundary layer and drag characteristics of antifouling coating systems with different finishes are presented. The coating types investigated were linear-polishing polymers, foul-release and controlled-depletion polymers. The data were collected through state-of-the-art equipment, including a 2-D laser Doppler velocimetry (LDV) system for hydrodynamic data in a large circulating water tunnel. Three coating systems were first applied on flat test panels with 'normal' finishes in the first test campaign to represent coating applications under idealised laboratory conditions. In order to address more realistic roughness conditions, as typically observed on ships' hulls, 'low' and 'high' roughness densities were introduced into the same types of coating, in the second test campaign. The data collected from the first test campaign served as the baseline to demonstrate the effect on the surface roughness and hydrodynamic drag characteristics of these coating types as a result of 'in-service' or 'severely flawed' coating application scenarios. Data collected on coatings with a range of in-service surface conditions provided a basis to establish correlation between the surface roughness characteristics and hydrodynamic performance (roughness function). The findings of the study indicate that the estimations of drag penalties based on well-applied, relatively smooth coating conditions underestimate the importance of hull roughness, which although undesirable, is commonplace in the world's commercial fleet.

A Fundamental Study on Measurement of Hull Roughness

“…As such, studies in relation to hull roughness have been performed using various approaches. Experimental approaches are mainly based on basin experiments using a plate ([4]- [5]). In recent years, there have been an increasing number of studies on ships using numerical simulation methods ([6]- [15]).…”

Advanced Numerical Method for Determining the Wetted Area of Container Ships for Increased Estimation Accuracy of Copper Biocide Emissions

“…Increase in resistance and effective power depending on the type of AF coating and speed. Source: Adapted and modified on the basis of [12].…”

“…In all coatings, the aim is to achieve a controlled release of biocide molecules from the polymer matrix (so called binder), while the release mechanisms themselves differ. Although the coating release mechanisms have been elucidated and explained [10][11][12], estimates of total AF biocide emissions from cargo vessels engaged on commercial ocean-going routes are still largely based on the researchers' estimates. Observing several container vessels of various classes (designed in the period from 1990 to 2006), it is clear that the draft of vessels increases the least (given the depth limit on navigation routes and terminals), and that neither the length nor beam increases linearly.…”

Review and historical overview of experimental facilities used in hull coating hydrodynamic tests

“…The findings of this study indicated that the estimations of drag penalties based on well-applied, relatively smooth coating conditions underestimate the importance of hull roughness. 36 Figure 1 shows the schematic of BL test setup used by Yeginbayeva 35 for her experiments. As it can be seen from the schematic drawing, test bed is used, first, to accelerate the flow in the measuring section of the ECT, secondly, to allow the standard UNEW’s flat testing panels (L = 0.6 m and W = 0.22 m) illustrated as red to be fitted on it for BL experiments.…”