Towards an absolute scale for adhesion strength of ship hull microfouling

Abstract

In-water ships' hull cleaning enables significant fuel savings through removal of marine fouling from surfaces. However, cleaning may also shorten the lifetime of hull coatings, with a subsequent increase in the colonization and growth rate of fouling organisms. Deleterious effects of cleaning would be minimized by matching cleaning forces to the adhesion strength of the early stages of fouling, or microfouling. Calibrated waterjets are routinely used to compare different coatings in terms of the adhesion strength of microfouling. However, an absolute scale is lacking for translating such results into cleaning forces, which are of interest for the design and operation of hull cleaning devices. This paper discusses how such forces can be determined using computational fluid dynamics. Semi-empirical formulae are derived for forces under immersed waterjets, where the normal and tangential components of wall forces are given as functions of different flow parameters. Nozzle translation speed is identified as a parameter for future research, as this may affect cleaning efficacy.

Nanotechnology-Based Antimicrobial and Antiviral Surface Coating Strategies

“…The adhesion of microbes on material surfaces is of critical importance in different areas such as marine fouling on ship hulls, the food and beverage industry and the biocontamination of medical devices [122][123][124]. Bacteria bond on a solid surface and they generate colonies and then biofilms, which promote the development of pathogenic infections [123].…”

Ship hull in-water cleaning and its effects on fouling-control coatings

“…The present setup differs from previous water-in-air jet designs (Swain and Schultz 1996;Finlay et al 2002;Cass e et al 2007), as the present results are instead obtained using an immersed water jet. This setup enables application of semi-empirical formulae for estimation of wall surface forces, which are based on geometrical parameters and fluid properties (Oliveira et al 2019).…”

“…Besides avoiding sample desiccation, an immersed jet enables the estimation of wall surface forces from empirical formulae. Thus, for immersed non-cavitating waterjets, stagnation pressure p s (N m À2 ) and maximum wall shear stress s w, max (N m À2 ) are estimated as (Oliveira et al 2019):…”

“…where q is seawater density (kg m À3 ), u 0 is the mean seawater velocity through the nozzle (m s À1 ), H is the nozzle standoff distance (m), Re is the Reynolds number based on nozzle inner diameter D (m), and r is the radial distance from the jet impingement (m). These formulae were derived for immersed jets (Oliveira et al 2019), and therefore do not apply to water-in-air jets used in previous studies (Swain and Schultz 1996;Finlay et al 2002). The selected nozzle was a 38-mm long pipe nozzle, with an inner diameter D ¼ 1.6 mm and a contraction ratio of 7:1 (Nordson EFD, RI, USA).…”

Correlation Studies of Indigenous Biofilm Forming Bacteria for Resistance Against Selected Metals, Antibiotics and Dyes Degradation

“…Different substrates including various plant cells, natural fresh or aquatic organizations, tooth coating and living tissues/surfaces are analyzed for their biofilm formation. Moreover, bacterial biofilms are also reported on hospital implanted health devices, piping system of water and different surfaces of ships/hulls (Khatoon et al, 2018;Chan et al, 2019;Oliveira et al, 2019). Bacterial biofilm formation is a survival mechanism for the bacterial cells; it offers protection against various factors including different toxins and antibiotics.…”