Seawater Spray Research Articles

Study on Performance of PVA Fiber Reinforced Concrete Exposed for 10 Years to Seawater Spray

Study on Performance of PVA Fiber Reinforced Concrete Exposed for 10 Years to Seawater Spray

Fragmentation of the “bag-breakup” type as a mechanism of the generation of sea spray at strong and hurricane winds

Experiments on generation mechanisms of sea water spray under hurricane wind were performed using shadow illumination high-speed video recording from several camera positions. Classification of fragmentation mechanism leading to generation of spray was conducted. Statistics of the events causing generation of spray was studied. A phenomenological model was developed based on the methods of statistical physics to describe the “bag-breakup” generation mechanism. The function of spray generation was conducted on this basis, which describes well the experimental data obtained under hurricane winds in the natural and laboratory conditions.

Enhancement of heat removal rate of high mass flux spray cooling by sea water

The main obligation in achieving high cooling rates in case of spray cooling at high surface temperature is the occurrence of film boiling phenomenon. Although the high mass flux spray reduces the film boiling affect, still, the heat transfer rate is not significant and hence, this process needs to be enhanced. In the absence of any information on the heat transfer augmentation technique, the present work deals with the enhancement of high mass flux spray cooling at very high initial plate temperature by using sea water. The sea water spray cooling process increases the heat removal rate by creating high heat transfer area for the droplet evaporation and by reducing the vapour pressure of vapour film on the hot plate. The cooling ability of the sea water spray is compared with the coolants (salt added water, surfactant added water and surfactant and salt added water) which partially depict the properties of sea water. For the experimental investigation, spray cooling was conducted at 900°C initial surface temperature on a 6mm thick AISI 304 steel plate (100×100mm) by using sea water and also aforesaid coolants at different concentrations. The surface heat flux and surface temperature have been predicted using the solution of the Inverse Heat Conduction Problem (IHCP). For the understanding of heat transfer mechanism, the properties of coolants (contact angle, thermal conductivity, density, specific heat and mass diffusivity) at different concentrations and spray behaviour (droplet diameter, spray pressure, droplet velocity and spray impingement density) at different flow rates were measured. The physical properties of the coolant reveal that the contact angle decreases with the increasing salt concentration up to 0.1M and further increment in salt concentration enhances the contact angle. From the thermal properties of the coolant, it is observed that thermal diffusivity in sea water is higher than salt added water. The sea water spray cooling asserts that the heat removal rate increases with the increasing percentage of sea water in the mixture of seawater and pure water due to the salt deposition on the hot surface. However, the achieved heat removal rate is lower than that of salt added water due to the comparatively less amount of salt deposition in case of sea water spray. Furthermore, the combined effect of the salt deposition and lowering of vapour pressure in vapour film phenomena produce better heat removal rate than the pure water and surfactant and salt added water. In comparison between sea water and surfactant added water spray cooling, the former produces higher heat removal rate because of the dominance of salt deposition phenomenon over the lowering of contact angle property. In case of sea water spray, the achieved critical heat flux (1.55MW/m2) is 1.3 times that of pure water (1.2MW/m2); moreover, the enhanced critical heat flux is obtained at 170°C higher surface temperatures. In addition to the above, the enhancement by NaCl added water spray is almost 1.6 times that of pure water. Due to the above mentioned favourable conditions for the fast cooling, the maximum cooling rates of 115°C/s and 135°C/s are achieved with sea water and NaCl added water sprays, respectively.

Discussion/comments regarding “Sea spray icing phenomena on marine vessels and offshore structures: Review and formulation” by A.R. Dehghani-Sanij, S.R. Dehghani, G.F. Naterer, Y.S. Muzychka☆

The purpose of this discussion is to demonstrate how the formula for the liquid water content in wind-generated seawater spray presented by Dehghani-Sanij et al. (2017) in conjunction with available wind speed statistics can be used to estimate the wind-generated seawater spray. Results are exemplified based on mean wind speed statistics for the Northern North Sea and the North Atlantic.

Major impact of volcanic gases on the chemical composition of precipitation in Iceland during the 2014–2015 Holuhraun eruption

AbstractThe Holuhraun eruption in 2014–2015 was the largest in Iceland for more than 200 years. It resulted in emissions of large quantities of volcanic gases into the atmosphere (11 megaton (Mt) SO2, 0.1 Mt HCl, and 0.05 Mt HF). During the eruption the volcanic gases had major effects on F, SO4 and to a lesser extent Cl concentrations in precipitaxtion throughout Iceland, effects not observed in recent decades. The concentrations of F, Cl, and SO4 (n = 705) reached values of 444 µm 12,270 µm, and 17,324 µm during the eruption and were on average ~20 times higher for F and SO4 and much lower for Cl compared to preeruption times. The concentrations of major cations (Si, Na, K, Ca, Mg, Al, and Fe) (n = 151) in the precipitation were taken as having originated from seawater spray and dissolution of rock dust and aerosol. Based on the mixing model developed here, it is demonstrated that the source of the enrichment of F and SO4 was indeed the volcanic gas emissions with >60–100 mol % of SO4 and F in the precipitation originated from volcanic gas, whereas the Cl originated mostly from seawater spray, making the volcanic gas input of Cl relatively less important than for F and SO4. The results showed that large volcanic eruptions can have major effects on atmospheric chemistry and impact the composition of precipitation.

Chloride Diffusivity and Life Prediction of Cracked RC Beams Exposed to Different Wet-Dry Ratios and Exposure Duration

Effects of crack width, wet-dry ratio, and exposure duration of wet-dry cycles on chloride ingress of RC beams were experimentally studied. Crack widths of 40, 70, 90, and 120 microns were, respectively, induced by three-point flexural loading and four wet-dry ratios (seawater spraying 1 d in one wet-dry cycle) of 1 : 3, 1 : 7, 1 : 11, and 1 : 15 were selected. Chloride contents of RC beams were tested every 32 d (or 16 d) of wet-dry cycles. Results show that chloride content increased significantly when crack width was larger than 90 microns and wet-dry ratio was 1 : 3, and it increased slightly when crack width was 120 microns and wet-dry ratio was 1 : 7, 1 : 11, and 1 : 15. The chloride content on steel bar surface became the largest when crack width was less than 90 microns and wet-dry ratio was 1 : 7, and while crack width was equal to or greater than 90 microns and wet-dry ratio was 1 : 3, it was the largest. Based on the testing results, chloride diffusion model and prediction model of residual service life of RC beams were suggested considering combined effects of crack width and exposure duration. The predicted residual service lives were corresponding well with experimental results and they decreased as crack width increased.

Assessing causes of quality deterioration of groundwater in Puttalam, Sri Lanka, using isotope and hydrochemical tools

ABSTRACTExtensive extraction of groundwater has resulted in deterioration of the groundwater quality in the Puttalam area in the northwestern coastal zone of Sri Lanka. This situation led us to carry out the present comprehensive study based on environmental isotopic (18O, 2H, 3H) and geochemical evaluation to understand the root cause for water quality deterioration. The isotopic data suggest that the surface water and shallow groundwaters are subjected to intensive evaporation and, as a result, increase in their salinity. Deep groundwater of the area is mostly recharged by direct infiltration of rainwater and at few places by nearby surface water bodies. The salinity increase of deep groundwater depends on the specific hydrogeological zones and would be due to dissolution of salts which are precipitated in soil through the seawater spray over the time, dissolution of minerals in geological matrix and leaching of salts from salterns. The quality of the deep groundwater is relatively good in the granitic gneiss zone and nearby areas outside the sedimentary aquifer. There is no evidence from isotope and hydrogeochemical evaluation for seawater intrusion into groundwater in the Puttalam area.

Chapter 21 Hydrogeology of São Miguel Island, Azores: a review

Abstract Groundwater is the main source of water supply on São Miguel. Groundwater abstraction (25 hm 3 a −1 ) relies almost exclusively on springs discharging from perched aquifers. A total of 1100 springs (1.5 springs/km 2 ) are located on São Miguel, mainly in the Água de Pau and the Furnas–Povoação groundwater bodies. Only 26 wells have been drilled, distributed principally in the west-central zone. Specific capacity ranges between 0.49 and 100 l (s m) −1 (median=1.11 l (s m) −1 ), while transmissivity ranges between 5.98×10 −4 and 1.22×10 −1 m 2 s −1 (median=1.35×10 −3 m 2 s −1 ). Groundwater is predominantly of the Na-Cl and Na-HCO 3 types and electrical conductivity in springs ranges from 36 to 440 μS cm −1 (median=152 μS cm −1 ), which is lower than in wells (211–9670 μS cm −1 ; median=515 μS cm −1 ). These values result from seawater spray, a CO 2 soil contribution and limited dissolution of primary silicate minerals from volcanic rocks. In the case of wells, seawater intrusion may also influence electrical conductivity. One of the main problems in groundwater quality is total and faecal coliform microbial contamination. A pollution risk map constructed for São Miguel as a whole showed that risk in the majority of the groundwater bodies is only very low to moderate.

Weathering processes in volcanic tuff rocks of the "Rupe di Coroglio" (Naples, southern Italy): erosion-rate estimation and weathering forms

The present work shows the preliminary data on the erosion rate estimation and weathering forms on the outcrop of the Neapolitan Yellow Tuff along the Rupe di Coroglio (Naples, southern Italy). This pyroclastic complex shows abundant alveolar and tafoni forms mostly related to salty seawater and salt spray processes that affect the western portion of the Posillipo hill. In this coastal environment, weathering forms such as alveolar, honeycombs or tafoni are very common producing from small to large deep cavities, development of which produces landslide phenomena. This area has been protected by consolidation interventions such as barrings, retaining walls and anchored structures. After 30 years from first interventions of consolidation, has been observed that some cables of the anchored structures protrude from rock escarpment with values between 5 and 12 cm. Based on these values an average erosion rate of 1.6÷4 mm/year was estimated.

Responses of Kyllinga peruviana Lam. to Sea Water Spray

Response of Kyllinga peruviana Lam. to salt spray was studied to have an insight into the ecophysiological adaptations underlying the responses. Plants were exposed to foliar salt spray at: two sprays per week (2SS), four sprays per week (4SS) or six sprays per week (6SS), while those sprayed with de-ionized water served as control (CSS). Salt spray did not affect plant survival but had negative effect on growth. The growth parameters decreased except stem girth, which increased significantly in plants sprayed with seawater. Fresh and dry mass of plant parts were significantly lower under seawater treatment than in control. Total biomass, the relative growth rate and leaf total chlorophyll decreased while the root: shoot ratio increased under seawater application. Air-borne salt reduced plant xylem water potential but increased stem succulence for ion dilution. Salt spray accumulated Na+ and Cl- in the aerial parts, resulting in an increased total nutrient and percentage ash content, which culminated in ion toxicity. Salt spray reduced uptake of some essential nutrients but increased N in the aerial parts of seawater-treated plants showing the presence of salt-related nitrogen compounds for osmotic adjustment. Significantly higher values were obtained for Na: K in plants exposed to salt spray than in the control. It led to reduction in stomata density and number of stomata per leaf by as much as 42.86% and 80.42% respectively at 6SS. Air-borne salt caused necrotic damage on the leaf with increasing application level. Generally, salt spray had no effect on the root growth. Kyllinga peruviana tolerates sea water spray by the development of some adaptations to withstand salt-related stress associated with the strandline environment.

Vegetative growth, mineral change, and fruit quality of ‘Fuji’ tree as affected by foliar seawater application

Extensive researches have been conducted over the decades to investigate the effects of seawater on many crop plants either by irrigation or foliar spray in an attempt to enhance the yield and quality. The purpose of this study was to quantitatively determine the effects of different foliar seawater sprays on vegetative growth, fruit quality and yield of eight-year-old ‘Fuji’/M.9 apple trees. A field experiment was conducted using two different concentrations of seawater (100 or 50-fold dilution) starting from 130 DAFB (days after full bloom) at 5-day intervals between the treatments. Foliar seawater sprays to ‘Fuji’ tree led to increased levels of fruit soluble solids along with higher activities of sucrose phosphate synthase (SPS) (EC 2.4.1.14), sucrose synthase (SS) (EC 2.4.1.13) and neutral invertase (EC 3.2.1.26). In addition, a significant increase in anthocyanin concentration was observed, especially when ‘Fuji’ trees were sprayed three times with 50-fold diluted seawater. Foliar seawater sprays also resulted in increases in Na+ concentration and K+/Ca2+ ratio in fruit. In contrast to fruit, the levels of N, Na+, K+, Mg2+ in leaves remained unchanged regardless of different seawater treatments. Moreover, foliar seawater sprays did not affect the vegetative growth since leaf area, leaf fresh weight, shoot elongation, and chlorophyll content did not differ significantly from those of control plants. The results suggest that foliar seawater treatments could be useful for improving fruit quality without affecting the yield.

ステンレス鋼の海洋環境におけるすきま腐食挙動

Exposure tests of various stainless steels have been conducted for 10 years with actual sea water. Corrosion resistance of each stainless steel under marine environments was evaluated by two types of tests which were atmospheric corrosion test and seawater spray test. The test results showed that spraying sea water enhanced the proceeding of corrosion. It has been proved that the super austenitic stainless steels defined by Pitting Resistance Equivalent (PRE=%Cr+3.3×%Mo+16×%N) over 40 have excellent corrosion resistance. The corrosion mechanism in this environment was basically estimated as crevice corrosion between the specimen surface and condensed substance originated from adhered chloride ions. In addition, microbes contained in sea water were considered to enhance the corrosion progress.Repassivation potential for crevice corrosion measurements were further carried out for Cl- ion to understand the corrosion mechanism assuming the critical potential of 500mV accounting for the existence of microbes. The obtained curves well support the exposure test results; the steel grades with PRE values over 40 were proved not to corrode under the present test conditions including temperature and Cl- ion concentrations. As a conclusion, the corrosion behavior of stainless steels can be explained by repassivaition potential for crevice corrosion considering microbes.

Weathering and Degradation Assessment of Rock Properties at the West Stone Pagoda, Gameunsaji Temple Site, Korea

The West Stone Pagoda at Gameunsaji Temple Site constructed in the 7th century is mainly composed of dark grey dacitic tuff bearing small numerous dioritic xenoliths. These xenoliths resulted in small holes due to differential weathering process from the host rocks. Physical strength of the pagoda was decreased due to weathering and damage caused by petrological, biological and coastal environmental factors. The southeastern part of the pagoda was extremely deteriorated that the rock surface showed exfoliation, fracture, open cavity, granular decomposition of minerals and salt crystallization by seawater spray from the eastern coast. The stone blocks were intersected by numerous cracks and contaminated by subsequent material such as cement mortar and iron plates. Also, the pagoda was colonized by algae, fungi, lichen and bryophytes on the roof rock surface and the gaps between the blocks. As a result of ultrasonic test, the rock materials fell under Highly Weathered Grade (HW) or Completely Weathered Grade (CW). Thus, conservational intervention is essentially required to prevent further weakening of the rock materials.

An experimental investigation on seawater SO2 scrubbing for marine application

A seawater spray scrubber was set up and tested with focus to desulfurization of marine engine exhaust gas. Experimental tests were carried out simulating typical exhaust conditions of a marine diesel engine burning heavy fuel oil and using real seawater. Different flue gas flow rates, seawater flow rates, and SO2 concentrations were tested. Liquid‐to‐gas ratios were in the range 1–10 × 10−3. A comparison between seawater and distilled water was also carried out to elucidate the effect of seawater alkalinity. In all conditions, the liquid phase was analyzed for alkalinity, pH, and sulfate content before and after the tests. Finally, the spray droplet size distribution was measured as a function of liquid flow rate.Experimental results indicated that seawater performed better than distilled water, by exploiting its inherent alkalinity. The desulfurization performance was improved by increasing the liquid flow rate and the gas residence time and by decreasing the SO2 concentration. SO2 capture efficiencies up to 93% were measured under the present operating conditions. The experimental data were further compared with calculations performed with an available model for SO2 absorption in fall‐down droplets within a simple plug‐flow reactor. Model calculations were carried out by using all parameters' values as measured in the present experimental campaign. Model results well fit the experimental data, even if a slight underestimation of the desulfurization efficiency is reported. The likely reasons are the assumed plug flow of gas as well as the neglected contribution to SO2 capture by water film falling at the wall. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1179–1186, 2013

Efficacy of high-pressure seawater spray against colonial tunicate fouling in mussel aquaculture: inter-annual variation

Invasive species such as ascidians have negative effects on aquaculture operations worldwide. Prince Edward Island, Canada, in particular has seen high fouling levels of non-native tunicates including the colonials Botryllus schlosseri and Botrylloides violaceus. Previous research indicated that high-pressure seawater spraying of mussel socks fouled with colonials is an effective mitigation strategy. Those results, however, were based on a year (2009) with unseasonably low water temperatures at the beginning of the colonial tunicate growing season in June and July; therefore, we repeated part of that study in the following year (2010) to determine whether typical (warm) early season water temperature affected tunicate fouling levels and how both treatment efficacy and fouling effect on mussel productivity differed between the two years. In 2010, Botryllus schlosseri fouling (in terms of biomass) was four-fold higher than in the colder year (2009), reaching an average biomass of 600-800 g per full-length mussel sock (up to 2.4 m long), but it still did not affect mussel productivity. B. violaceus was also present on mussel socks, but only in very low amounts (<50 g per mussel sock), so that results for this species were inconclusive. Highpressure water spraying was at least as effective in 2010 as in 2009 at removing B. schlosseri tunicate fouling from mussel socks, though in 2010, treatment also negatively affected mussel productivity by reducing mussel biomass by 30% in the frequently (5×) treated group. Considering these results along with the potential risk of increased tunicate spread (through fragmentation) and the cost of treatment, frequent application of high-pressure water spray is unnecessary.

Effects of Wave-Dissipating Blocks on Reduction of Salinity in the Air Generated at a Vertical Breakwater Based on Field Observations

At Waku fishing port in Yamaguchi Prefecture, Japan, which has a vertical breakwater at the mouth of the port, wave-dissipating blocks were installed in front of the breakwater to reduce the sea water spray generated at the breakwater. To clarify the effect of wave-dissipating blocks on the reduction of the salinity in the air, a large number of field observations were conducted at the port in the winter seasons from 2005 to 2011; the run-ups of the splash (heights and frequency), the wind (velocity and direction) and the salinity concentrations in the air were measured at about 30 observation points. The data obtained before and after the construction showed that the violent run-up of splash was efficiently blocked by fully covering the vertical breakwater with the wave-dissipating blocks. Consequently, the salinity in the air was also drastically reduced.

Fluoride content in drinking water supply in São Miguel volcanic island (Azores, Portugal)

High fluoride contents in the water supply of the city of Ponta Delgada, located in the volcanic island of São Miguel (Azores, Portugal) have been reported. Dental fluorosis in São Miguel has been identified and described in several medical surveys. The water supply in Ponta Delgada consists entirely of groundwater. A study was carried out in order to characterize the natural F-pollution of a group of springs (30) and wells (3), that are associated to active central volcanoes of a trachytic nature. Two springs known for their high content in fluoride were sampled, both located in the central volcano of Furnas.The sampled waters are cold, ranging from slightly acidic to slightly alkaline (pH range 6.53–7.60), exhibiting a low electrical conductivity (springs range 87–502μS/cm; wells range 237–1761μS/cm), and are mainly from the Na–HCO3, Na–HCO3–Cl and Na–Cl–HCO3 water types. Results suggest two main trends of geochemical evolution: silicate weathering, enhanced by CO2 dilution, and seawater spraying. Fluoride contents range between 0.17mg/L and 2mg/L, and no seasonal variations were detected. Results in the sources of the water supply system are lower than those of the Furnas volcano, which reach 5.09mgF/L, demonstrating the effect of F-rich gaseous emanations in this area. Instead, the higher fluoride contents in the water supply are mainly due to silicate weathering in aquifers made of more evolved volcanic rocks.

Ice Adhesion Tests on Pliable Polymer Sheets for Protection Against Sea-Water Spray Icing

Heavy sea-water spray icing is a major problem in the maintenance of lighthouses situated in northern harbors facing the Sea of Japan. Moreover, low ice adhesion materials or anti-icing coatings are ineffective over long periods. In this study, we have investigated the characteristics of saline ice adhesion on hydrophilic and hydrophobic pliable polymer sheets that can be used to envelop and thereby protect small lighthouses. We conducted experiments in cold room laboratories, and further, we verified the deicing conditions. Ice adhesion strength tests using fresh water indicated that a highly hydrophobic surface exhibited lower adhesion strength than other test materials. The results of saline ice adhesion tests at −20°C indicated that the adhesion strength decreases very rapidly as the salinity increases for all materials; this trend was particularly remarkable in case of superhydrophilic materials. The water spray icing tests were verified by experiments conducted using an ice model basin. Wet growth of ice occurred on all test specimens including the highly hydrophobic sheets. Furthermore, the initial icing depended significantly on the hydrophobic or hydrophilic surface properties. The icing on the hydrophobic surface was characterized by the formation of vertical streaks of ice; irregular projections could be observed on the ice surface. On the other hand, a thin fluid flow was formed on superhydrophilic surfaces. Exfoliation of pieces of the sheet ice was often observed during the initial growth. Deicing could be easily performed for both pliable polymer sheets. A combination of low ice adhesion property and rapid distortion was effective for the deicing of sea-water spray icing.

Large-scale spatial variability of major ions in the atmospheric wet deposition along the China–Antarctica transect (31°N–69°S)

ABSTRACTTwenty-two atmospheric wet deposition samples were collected along the large-scale transect from China to Antarctica, and the major ion components as well as their sources were analysed. It is the first time that chemical composition variation of precipitation has been investigated on such a large-scale transect. The results show that the precipitations exhibit near-neutral pH on the average. On the whole, ionic levels on an equivalent basis are presented as Cl−>Na+>Mg2+>>Ca2+>K+>>, and ionic contents of rainfall are generally higher compared with values of snowfall. Ionic concentrations vary greatly on the study transect, and the values of the Northern Hemisphere are relatively higher. Both enrichment factor and principal component analyses reveal that Cl−, Na+, K+ and Mg2+ are mainly related to sea salt, namely, the marine source. The good correlations between marine-sourced ions and wind speed indicate that seawater sprays are important sources of precipitation ions. Land-based sources, for example, human activities, are the primary sources of , and Ca2+. partly originates from sea salt, but anthropogenic and biogenic sources are also important contributors. Backward trajectories illustrate well the different main sources and transport routes of the precipitation ions.

PRACTICAL MEASURES AGAINST SEA SALT PARTICLES FROM AN EXISTING VERTICAL WALL

At Waku fishing port, facing to Japan Sea, in Yamaguchi prefecture, Japan, a vertical type breakwater was constructed in front of the mouth of the port to protect the inside against incoming waves about 10 years ago. Residents in the area have been troubled with heavy seawater spray and much smaller sea salt particles caused at the breakwater by sever waves and strong winds ever since. To reduce the generation of and the damage from the seawater spray and the sea salt particles, three different types of measures were proposed: (a) covering the breakwater with wave dissipating blocks, (b) construction of a low crested offshore breakwater some distance ahead of the breakwater, and (c) construction of an artificial reef some distance ahead of the breakwater. Laboratory experiments using a wave flume with a wind tunnel were conducted to compare the effects of suppressing the water spray generation. The results of the comparative experiments showed that the covering with the wave dissipating blocks (Plan (a)) is the most effective means.