The robustness of the cathodic protection systems utilized for offshore wind monopile foundations... more The robustness of the cathodic protection systems utilized for offshore wind monopile foundations depends on the surface condition of the steel as well as the environmental conditions. This study investigated how preexisting biofouling and corrosion products on vertical uncoated steel surfaces extending from the intertidal zone to the buried zone affected the cathodic protection requirements when impressed current cathodic protection (ICCP) was applied under tidal conditions. The comparative results between initially clean and previously fouled and corroded panel sets showed that the fouling and corrosion products increased both the initial and mean current densities. They also altered the composition, slowed the formation, and reduced the protective properties of cathodic chalks during nine weeks of deployment in seawater at Port Canaveral, Florida.
Biofouling is problematic for the shipping industry and can lead to functional and financial setb... more Biofouling is problematic for the shipping industry and can lead to functional and financial setbacks. One possible means of biofouling prevention is the use of ultraviolet-C (UVC) light. Previous studies have investigated UVC with marine coatings, but the synergistic effect with color and surface material, specifically reflectance, has yet to be determined. This study comprised three parts: UVC and color (red vs. white), UVC and reflectance (stainless steel vs. polycarbonate), and UVC and exposure intervals (weekly intervals and 10 min intervals). There was no variance in the biofouling communities for colored surfaces when exposed to 254 nm UVC. Reflectance studies demonstrated that the surface material plays a role in biofouling settlement. Stainless steel panels had significantly greater macrofouling settlement than polycarbonate, specifically among encrusting bryozoan, tubeworms, and tunicate communities. Panels of both surface materials exposed to indirect UVC significantly di...
The majority of ships are coated with antifouling paint. These coatings can fail to completely pr... more The majority of ships are coated with antifouling paint. These coatings can fail to completely protect from fouling due to mismatches between paint type and duty cycle, the presence of biocide tolerant fouling organisms, improperly applied, old or damaged paint, etc. Grooming antifouling coatings can provide a solution. Five commercially available antifouling coatings were applied to panels. Half of the replicates were groomed weekly, the other half were immersed and allowed to freely foul, undisturbed. Photographs were taken and panels were visually assessed monthly. Over the period of two years, all the undisturbed panels became fouled with a diverse community of macrofouling organisms including encrusting and arborescent bryozoans, barnacles, tube worms, oysters, tunicates and more. The groomed panels remained clean of macrofouling for an extended period of time, up to two years depending on the coating. Cover of biofilm was also low on groomed panels. Grooming was effective at m...
Submitted for the DFD15 Meeting of The American Physical Society Characterization of floating ele... more Submitted for the DFD15 Meeting of The American Physical Society Characterization of floating element balance for field panel testing 1 J. TRAVIS HUNSUCKER, HARRISON GARDNER, GEOFFREY SWAIN, Center for Corrosion and Biofouling Control, Florida Institute of Technology-Multiple experiments were performed to investigate and characterize the uncertainty and bias of a through-hull flush mounted floating element balance designed to measure the hydrodynamic drag forces of biofouling and marine coatings on 25 x 30 cm test panels. The instrument is located in a wet well on the aft portion of a 27' Chris Craft Commander. Testing occurs over a series of speeds ranging from a Froude number of 0.50-2.20 on calm days (force 3 or less) in waters along the central east coast of Florida. Recent modifications have been made to the instrumentation in an effort to improve the overall accuracy of the system. This study compares frictional drag measurements of the floating element balance to those obtained using the Clauser chart and Preston tube methods for a smooth surface. Boundary layer velocity profiles are examined to understand the nature of the flow over the testing section. Roughness function values for 60 and 220 grit sandpaper were calculated from data obtained using the floating element balance. These values were compared with previous work to examine the overall bias of the methodology. Repeat measurements for a smooth panel were analyzed to characterize the overall uncertainty in the system.
Philosophical Transactions of the Royal Society B: Biological Sciences, 2019
Concerns about the bioaccumulation of toxic antifouling compounds have necessitated the search fo... more Concerns about the bioaccumulation of toxic antifouling compounds have necessitated the search for alternative strategies to combat marine biofouling. Because many biologically essential minerals have deleterious effects on organisms at high concentration, one approach to preventing the settlement of marine foulers is increasing the local concentration of ions that are naturally present in seawater. Here, we used surface-active borate glasses as a platform to directly deliver ions (Na + , Mg 2+ and BO 4 3− ) to the adhesive interface under acorn barnacles ( Amphibalanus ( =Balanus ) amphitrite ). Additionally, surface-active glasses formed reaction layers at the glass–water interface, presenting another challenge to fouling organisms. Proteomics analysis showed that cement deposited on the gelatinous reaction layers is more soluble than cement deposited on insoluble glasses, indicating the reaction layer and/or released ions disrupted adhesion processes. Laboratory experiments showe...
Dendritic polyglycerols (PGs) were grafted onto surfaces using a ring-opening polymerization reac... more Dendritic polyglycerols (PGs) were grafted onto surfaces using a ring-opening polymerization reaction and the fouling-release properties against marine organisms were determined. The coatings were characterized by spectroscopic ellipsometry, contact angle goniometry, ATR-FTIR and stability tests in different aqueous media. A high resistance towards the attachment of different proteins was found. The PG coatings with three different thicknesses were tested in a laboratory assay against the diatom Navicula incerta and in a field assay using a rotating disk. Under static conditions, the PG coatings did not inhibit the initial attachment of diatoms, but up to 94 % of attached diatoms could be removed from the coatings after exposure to a shear stress of 19 Pa. Fouling-release was found to be enhanced if the coatings were sufficiently thick. The excellent fouling-release properties were supported in dynamic field-immersion experiments in which the samples were continually exposed to a shear stress of 0.18 Pa.
Langmuir : the ACS journal of surfaces and colloids, Jun 7, 2016
The influence of zwitterionic self-assembled monolayers on settlement and removal of algae was st... more The influence of zwitterionic self-assembled monolayers on settlement and removal of algae was studied. The monolayers were constructed either from zwitterionic thiols or from solutions of positively and negatively charged thiols. The cationic component was composed of quaternary ammonium terminated thiols and the anionic component contained sulfate or carboxylate termination. During assembly, all surfaces showed a strong tendency for equilibration of the surface charge. Settlement and adhesion assays with zoospores of Ulva linza and the diatom Navicula incerta, and field tests of the initial surface colonization revealed the relevance of charge equilibration for the biological inertness of the prepared surfaces.
The preparation of this type of polymer has been described previously (Ekin and Webster 2006). Th... more The preparation of this type of polymer has been described previously (Ekin and Webster 2006). The cyclic siloxane monomer, D4 (50 g), and benzyltrimethylammonium hydroxide solution (0.13
The application of a proactive grooming program to manage the fouling control coatings applied to... more The application of a proactive grooming program to manage the fouling control coatings applied to ship hulls provides an opportunity to address the climate crisis, invasive species and the discharge of biocides into the marine environment. A large percentage of the total power required to propel a ship is to overcome the viscous drag created between the hull and the water. The powering penalty due to increases in coating roughness and the development of biofouling are well documented. In addition, poorly maintained fouling control coatings may lead to the transportation of invasive species. In-water hull cleaning is therefore an important part of ship operations; however, this is typically implemented as a reactive measure when fouling reaches a critical level and requires powerful machinery which damages the coatings, creates unwanted discharge and in many locations the discharge will require capture and disposal. Ship hull grooming is being developed as a proactive method to manag...
Barnacle adhesion measurements provide an excellent method of assessing the foul release characte... more Barnacle adhesion measurements provide an excellent method of assessing the foul release characteristics of non‐toxic surfaces. This paper describes both tensile and shear force methods that have been developed for field applications. Selected data are presented and the results discussed with respect to the variables that affect the observed adhesion values.
Abstract Oyster populations in many coastal areas have decreased as a result of overharvesting an... more Abstract Oyster populations in many coastal areas have decreased as a result of overharvesting and habitat degradation. In order to help restore oyster populations and natural water filtration, many restoration efforts utilize plastic mesh to reseed oyster reefs. However, plastics do not break down or mineralize in seawater, instead they break down into smaller and smaller pieces eventually becoming what is termed microplastics. One alternative may be the use of a cathodically protected steel which develops a mineral accretion layer and enhances calcareous marine growth. In order to test the efficacy of this material for oyster restoration and its ability to promote oyster growth, a field experiment was designed to compare it to traditional plastic mats at three locations. At all sites, the steel mats were able to promote the recruitment of oysters at a rate equal to or greater than the plastic mats. The amount of mineral accretion and the total number of oysters present on the mats were dependent on the environmental and ecological conditions of the test site. The steel mats were easy to work with, provided sufficient oyster settlement, and gain in weight over time. This makes them an attractive alternative to plastic oyster restoration mats, with implications for creating artificial reefs or living shorelines.
A proof-of-concept study was designed to investigate using an Ultraviolet C (UVC) lamp mounted on... more A proof-of-concept study was designed to investigate using an Ultraviolet C (UVC) lamp mounted on a hull-crawling remotely operated vehicle (ROV) to prevent biofouling on a ship hull. A wheeled cart with a UVC lamp was built to expose two large test panels to UVC. The test panels were coated with an ablative copper antifouling and a silicone fouling release coating, and these were immersed in seawater at Port Canaveral, Florida. Three exposure frequencies (once a week, twice a week, and three times a week) and two dosages (8 and 16 s of UVC exposure) were tested. UVC was effective at preventing biofilm growth during the first 2 weeks of UVC treatment but was unable to prevent increased fouling growth as time progressed. It appears that an increase in UVC intensity and duration of exposure would be needed to prevent fouling growth especially during high-fouling seasons or that UVC exposure would need to be combined with another fouling prevention practice, such as mechanical wiping, ...
Grooming is a proactive method to keep a ship's hull free of fouling. This approach uses a fr... more Grooming is a proactive method to keep a ship's hull free of fouling. This approach uses a frequent and gentle wiping of the hull surface to prevent the recruitment of fouling organisms. A study was designed to compare the community composition and the drag associated with biofilms formed on a groomed and ungroomed fouling release coating. The groomed biofilms were dominated by members of the Gammaproteobacteria and Alphaproteobacteria as well the diatoms Navicula, Gomphonemopsis, Cocconeis, and Amphora. Ungroomed biofilms were characterized by Phyllobacteriaceae, Xenococcaceae, Rhodobacteraceae, and the pennate diatoms Cyclophora, Cocconeis, and Amphora. The drag forces associated with a groomed biofilm (0.75 ± 0.09 N) were significantly less than the ungroomed biofilm (1.09 ± 0.06 N). Knowledge gained from this study has helped the design of additional testing which will improve grooming tool design, minimizing the growth of biofilms and thus lowering the frictional drag force...
Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Model silicone foul-release coatings with controlled molecular architecture were evaluated to det... more Model silicone foul-release coatings with controlled molecular architecture were evaluated to determine the effect of compositional variables such as filler loading and crosslink density on pseudobarnacle attachment strength. Pseudobarnacle adhesion values correlated with ...
A combinatorial workflow for developing organic surface coatings has been developed. The workflow... more A combinatorial workflow for developing organic surface coatings has been developed. The workflow is uniquely designed to prepare and evaluate marine coatings that prevent biofouling on the hulls of ships. A critical component of the workflow is the high throughput screening of settlement and ease of removal of marine organisms from coating surfaces. Methods have been developed to directly and indirectly quantify marine bacterial biofilm growth and retention. Correlations have been developed between these high throughput bioassays and results from ocean testing.
The role of hydrodynamic wall shear stresses on the development of the fouling community structur... more The role of hydrodynamic wall shear stresses on the development of the fouling community structure and resulting frictional drag were examined using a commercially available fouling release coating. Immersed test panels were exposed to three different hydrodynamic treatments, one static and two dynamic (corresponding to an estimated wall shear stress of 7.0 and 25.5 Pa). The drag of the panels was measured in a hydrodynamic test chamber at discrete time intervals over 35 days. The fouling community composition on the static panels was significantly different from the organisms observed on the dynamic panels. Despite different fouling community composition, the drag forces measured on the panels were very similar. This suggests that the frictional drag of low form and soft fouling communities are similar and that there may be a stepwise increase in frictional drag associated with the presence of mature calcareous organisms.
The robustness of the cathodic protection systems utilized for offshore wind monopile foundations... more The robustness of the cathodic protection systems utilized for offshore wind monopile foundations depends on the surface condition of the steel as well as the environmental conditions. This study investigated how preexisting biofouling and corrosion products on vertical uncoated steel surfaces extending from the intertidal zone to the buried zone affected the cathodic protection requirements when impressed current cathodic protection (ICCP) was applied under tidal conditions. The comparative results between initially clean and previously fouled and corroded panel sets showed that the fouling and corrosion products increased both the initial and mean current densities. They also altered the composition, slowed the formation, and reduced the protective properties of cathodic chalks during nine weeks of deployment in seawater at Port Canaveral, Florida.
Biofouling is problematic for the shipping industry and can lead to functional and financial setb... more Biofouling is problematic for the shipping industry and can lead to functional and financial setbacks. One possible means of biofouling prevention is the use of ultraviolet-C (UVC) light. Previous studies have investigated UVC with marine coatings, but the synergistic effect with color and surface material, specifically reflectance, has yet to be determined. This study comprised three parts: UVC and color (red vs. white), UVC and reflectance (stainless steel vs. polycarbonate), and UVC and exposure intervals (weekly intervals and 10 min intervals). There was no variance in the biofouling communities for colored surfaces when exposed to 254 nm UVC. Reflectance studies demonstrated that the surface material plays a role in biofouling settlement. Stainless steel panels had significantly greater macrofouling settlement than polycarbonate, specifically among encrusting bryozoan, tubeworms, and tunicate communities. Panels of both surface materials exposed to indirect UVC significantly di...
The majority of ships are coated with antifouling paint. These coatings can fail to completely pr... more The majority of ships are coated with antifouling paint. These coatings can fail to completely protect from fouling due to mismatches between paint type and duty cycle, the presence of biocide tolerant fouling organisms, improperly applied, old or damaged paint, etc. Grooming antifouling coatings can provide a solution. Five commercially available antifouling coatings were applied to panels. Half of the replicates were groomed weekly, the other half were immersed and allowed to freely foul, undisturbed. Photographs were taken and panels were visually assessed monthly. Over the period of two years, all the undisturbed panels became fouled with a diverse community of macrofouling organisms including encrusting and arborescent bryozoans, barnacles, tube worms, oysters, tunicates and more. The groomed panels remained clean of macrofouling for an extended period of time, up to two years depending on the coating. Cover of biofilm was also low on groomed panels. Grooming was effective at m...
Submitted for the DFD15 Meeting of The American Physical Society Characterization of floating ele... more Submitted for the DFD15 Meeting of The American Physical Society Characterization of floating element balance for field panel testing 1 J. TRAVIS HUNSUCKER, HARRISON GARDNER, GEOFFREY SWAIN, Center for Corrosion and Biofouling Control, Florida Institute of Technology-Multiple experiments were performed to investigate and characterize the uncertainty and bias of a through-hull flush mounted floating element balance designed to measure the hydrodynamic drag forces of biofouling and marine coatings on 25 x 30 cm test panels. The instrument is located in a wet well on the aft portion of a 27' Chris Craft Commander. Testing occurs over a series of speeds ranging from a Froude number of 0.50-2.20 on calm days (force 3 or less) in waters along the central east coast of Florida. Recent modifications have been made to the instrumentation in an effort to improve the overall accuracy of the system. This study compares frictional drag measurements of the floating element balance to those obtained using the Clauser chart and Preston tube methods for a smooth surface. Boundary layer velocity profiles are examined to understand the nature of the flow over the testing section. Roughness function values for 60 and 220 grit sandpaper were calculated from data obtained using the floating element balance. These values were compared with previous work to examine the overall bias of the methodology. Repeat measurements for a smooth panel were analyzed to characterize the overall uncertainty in the system.
Philosophical Transactions of the Royal Society B: Biological Sciences, 2019
Concerns about the bioaccumulation of toxic antifouling compounds have necessitated the search fo... more Concerns about the bioaccumulation of toxic antifouling compounds have necessitated the search for alternative strategies to combat marine biofouling. Because many biologically essential minerals have deleterious effects on organisms at high concentration, one approach to preventing the settlement of marine foulers is increasing the local concentration of ions that are naturally present in seawater. Here, we used surface-active borate glasses as a platform to directly deliver ions (Na + , Mg 2+ and BO 4 3− ) to the adhesive interface under acorn barnacles ( Amphibalanus ( =Balanus ) amphitrite ). Additionally, surface-active glasses formed reaction layers at the glass–water interface, presenting another challenge to fouling organisms. Proteomics analysis showed that cement deposited on the gelatinous reaction layers is more soluble than cement deposited on insoluble glasses, indicating the reaction layer and/or released ions disrupted adhesion processes. Laboratory experiments showe...
Dendritic polyglycerols (PGs) were grafted onto surfaces using a ring-opening polymerization reac... more Dendritic polyglycerols (PGs) were grafted onto surfaces using a ring-opening polymerization reaction and the fouling-release properties against marine organisms were determined. The coatings were characterized by spectroscopic ellipsometry, contact angle goniometry, ATR-FTIR and stability tests in different aqueous media. A high resistance towards the attachment of different proteins was found. The PG coatings with three different thicknesses were tested in a laboratory assay against the diatom Navicula incerta and in a field assay using a rotating disk. Under static conditions, the PG coatings did not inhibit the initial attachment of diatoms, but up to 94 % of attached diatoms could be removed from the coatings after exposure to a shear stress of 19 Pa. Fouling-release was found to be enhanced if the coatings were sufficiently thick. The excellent fouling-release properties were supported in dynamic field-immersion experiments in which the samples were continually exposed to a shear stress of 0.18 Pa.
Langmuir : the ACS journal of surfaces and colloids, Jun 7, 2016
The influence of zwitterionic self-assembled monolayers on settlement and removal of algae was st... more The influence of zwitterionic self-assembled monolayers on settlement and removal of algae was studied. The monolayers were constructed either from zwitterionic thiols or from solutions of positively and negatively charged thiols. The cationic component was composed of quaternary ammonium terminated thiols and the anionic component contained sulfate or carboxylate termination. During assembly, all surfaces showed a strong tendency for equilibration of the surface charge. Settlement and adhesion assays with zoospores of Ulva linza and the diatom Navicula incerta, and field tests of the initial surface colonization revealed the relevance of charge equilibration for the biological inertness of the prepared surfaces.
The preparation of this type of polymer has been described previously (Ekin and Webster 2006). Th... more The preparation of this type of polymer has been described previously (Ekin and Webster 2006). The cyclic siloxane monomer, D4 (50 g), and benzyltrimethylammonium hydroxide solution (0.13
The application of a proactive grooming program to manage the fouling control coatings applied to... more The application of a proactive grooming program to manage the fouling control coatings applied to ship hulls provides an opportunity to address the climate crisis, invasive species and the discharge of biocides into the marine environment. A large percentage of the total power required to propel a ship is to overcome the viscous drag created between the hull and the water. The powering penalty due to increases in coating roughness and the development of biofouling are well documented. In addition, poorly maintained fouling control coatings may lead to the transportation of invasive species. In-water hull cleaning is therefore an important part of ship operations; however, this is typically implemented as a reactive measure when fouling reaches a critical level and requires powerful machinery which damages the coatings, creates unwanted discharge and in many locations the discharge will require capture and disposal. Ship hull grooming is being developed as a proactive method to manag...
Barnacle adhesion measurements provide an excellent method of assessing the foul release characte... more Barnacle adhesion measurements provide an excellent method of assessing the foul release characteristics of non‐toxic surfaces. This paper describes both tensile and shear force methods that have been developed for field applications. Selected data are presented and the results discussed with respect to the variables that affect the observed adhesion values.
Abstract Oyster populations in many coastal areas have decreased as a result of overharvesting an... more Abstract Oyster populations in many coastal areas have decreased as a result of overharvesting and habitat degradation. In order to help restore oyster populations and natural water filtration, many restoration efforts utilize plastic mesh to reseed oyster reefs. However, plastics do not break down or mineralize in seawater, instead they break down into smaller and smaller pieces eventually becoming what is termed microplastics. One alternative may be the use of a cathodically protected steel which develops a mineral accretion layer and enhances calcareous marine growth. In order to test the efficacy of this material for oyster restoration and its ability to promote oyster growth, a field experiment was designed to compare it to traditional plastic mats at three locations. At all sites, the steel mats were able to promote the recruitment of oysters at a rate equal to or greater than the plastic mats. The amount of mineral accretion and the total number of oysters present on the mats were dependent on the environmental and ecological conditions of the test site. The steel mats were easy to work with, provided sufficient oyster settlement, and gain in weight over time. This makes them an attractive alternative to plastic oyster restoration mats, with implications for creating artificial reefs or living shorelines.
A proof-of-concept study was designed to investigate using an Ultraviolet C (UVC) lamp mounted on... more A proof-of-concept study was designed to investigate using an Ultraviolet C (UVC) lamp mounted on a hull-crawling remotely operated vehicle (ROV) to prevent biofouling on a ship hull. A wheeled cart with a UVC lamp was built to expose two large test panels to UVC. The test panels were coated with an ablative copper antifouling and a silicone fouling release coating, and these were immersed in seawater at Port Canaveral, Florida. Three exposure frequencies (once a week, twice a week, and three times a week) and two dosages (8 and 16 s of UVC exposure) were tested. UVC was effective at preventing biofilm growth during the first 2 weeks of UVC treatment but was unable to prevent increased fouling growth as time progressed. It appears that an increase in UVC intensity and duration of exposure would be needed to prevent fouling growth especially during high-fouling seasons or that UVC exposure would need to be combined with another fouling prevention practice, such as mechanical wiping, ...
Grooming is a proactive method to keep a ship's hull free of fouling. This approach uses a fr... more Grooming is a proactive method to keep a ship's hull free of fouling. This approach uses a frequent and gentle wiping of the hull surface to prevent the recruitment of fouling organisms. A study was designed to compare the community composition and the drag associated with biofilms formed on a groomed and ungroomed fouling release coating. The groomed biofilms were dominated by members of the Gammaproteobacteria and Alphaproteobacteria as well the diatoms Navicula, Gomphonemopsis, Cocconeis, and Amphora. Ungroomed biofilms were characterized by Phyllobacteriaceae, Xenococcaceae, Rhodobacteraceae, and the pennate diatoms Cyclophora, Cocconeis, and Amphora. The drag forces associated with a groomed biofilm (0.75 ± 0.09 N) were significantly less than the ungroomed biofilm (1.09 ± 0.06 N). Knowledge gained from this study has helped the design of additional testing which will improve grooming tool design, minimizing the growth of biofilms and thus lowering the frictional drag force...
Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Model silicone foul-release coatings with controlled molecular architecture were evaluated to det... more Model silicone foul-release coatings with controlled molecular architecture were evaluated to determine the effect of compositional variables such as filler loading and crosslink density on pseudobarnacle attachment strength. Pseudobarnacle adhesion values correlated with ...
A combinatorial workflow for developing organic surface coatings has been developed. The workflow... more A combinatorial workflow for developing organic surface coatings has been developed. The workflow is uniquely designed to prepare and evaluate marine coatings that prevent biofouling on the hulls of ships. A critical component of the workflow is the high throughput screening of settlement and ease of removal of marine organisms from coating surfaces. Methods have been developed to directly and indirectly quantify marine bacterial biofilm growth and retention. Correlations have been developed between these high throughput bioassays and results from ocean testing.
The role of hydrodynamic wall shear stresses on the development of the fouling community structur... more The role of hydrodynamic wall shear stresses on the development of the fouling community structure and resulting frictional drag were examined using a commercially available fouling release coating. Immersed test panels were exposed to three different hydrodynamic treatments, one static and two dynamic (corresponding to an estimated wall shear stress of 7.0 and 25.5 Pa). The drag of the panels was measured in a hydrodynamic test chamber at discrete time intervals over 35 days. The fouling community composition on the static panels was significantly different from the organisms observed on the dynamic panels. Despite different fouling community composition, the drag forces measured on the panels were very similar. This suggests that the frictional drag of low form and soft fouling communities are similar and that there may be a stepwise increase in frictional drag associated with the presence of mature calcareous organisms.
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Papers by Geoffrey Swain