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The demand for liquid carriers, such as liquefied natural gas (LNG), has increased in recent years. One of the most common types of LNG carriers is the membrane type, which is often built by a shipyard with a prismatic tank shape. This carrier is commonly known for its effective ways to mitigate sloshing using a baffle. Therefore, this study was performed to evaluate sloshing in a prismatic tank using vertical and T-shape baffles. The sloshing was conducted with 25% and 50% filling ratios because it deals with the nonlinear free-surface flow. Furthermore, the smoothed particle hydrodynamics (SPH) was used to overcome sloshing with ratio of a baffle and water depth is 0.9. A comparison was made for the dynamic pressure with the experiment. The results show that SPH has an acceptable accuracy for dynamic and hydrostatic pressures. Baffle installation significantly decreases the wave height, dynamic pressure and hydrodynamic force. [ABSTRACT FROM AUTHOR]

In this paper numerical simulations were performed utilizing Computational fluid dynamics code Fluent to investigate the thermo-fluid performance of a wavy rectangular winglet supported fin-and-tube heat exchanger with five inline rows of circular tubes. The influence of wave height, number of waves, wary winglet length and winglet attack angle on the thermo-fluid performance of the fin-and-tube heat transfer surface has been examined under laminar flow conditions. Further the Plain and wavy rectangular winglets are placed together over different tube locations and their effect on heat transfer and flow resistance is also examined. An enhancement factor has also been discussed to summarize the overall thermo-fluid performance. The results show that increase in the wave height increase both heat transfer and pressure drop, and an optimum wave height could be decided based on the enhancement factor. It is alsofound that the increase in wavy winglet length guides the flow more effectively towards the tubes wake region. It is also observed that with increase in number of waves the heat transfer performance initially increases and then decreases as the wave pitch becomes very small. For wavy winglet supported heat exchanger the optimum attack angle is found out for maximum enhancement factor. [ABSTRACT FROM AUTHOR]

The aim of this work is to assess the effect of a nature-based solution for reducing wave heights on the Southern Romanian coast. Apart from investigating the presence of seagrass from the environmental point of view, there is also a need to assess its impact on the coastal hydrodynamics. The impact on the wave heights of a seagrass meadow located on the Southern Romanian coast, has been analyzed by means of a wave model. In this purpose, several numerical simulations have been performed, both for low and average offshore wave conditions, available from a previous wave climate study, which used a 30 years climate data set. A first set of simulations have been performed in the absence of seagrass. Then a seagrass meadow has been added to our grid and the wave model has been run in the same offshore wave conditions. The differences in computed nearshore wave heights reach around 4% for moderate energy waves. These results show that, on the Southern Romanian coast, seagrass could be regarded as an additional measure for nearshore wave attenuation. [ABSTRACT FROM AUTHOR]

In this paper, we present some wave height estimates for the two-dimensional steady periodic water waves subject to the effect of vorticity. The lower bounds of wave heights for the case of positive vorticity and negative vorticity are derived, respectively. These results are associated with the pressure data at the flat bed and velocity data on trough line, and to the pressure data at the flat bed and velocity data on crest line, respectively. Furthermore, we provide some upper bounds of wave heights, which rely on velocity and pressure data at an arbitrary intermediate depth. In addition, we show some applications of the present model. • We consider the setting of rotation flows and present some wave height estimates. • The approach is different from the setting corresponds to the case of irrotational flows. • We present some applications of the present model. [ABSTRACT FROM AUTHOR]

The paper offers a novel comparative case study on the performance of solid versus porous breakwater physically modeled under similar laboratory and wave conditions. Unidirectional waves were generated in a two dimensional laboratory flume having dimensions of 21.3 m length, 0.76 m width and 0.74 m height. Keeping still water depth of 50 cm, waves with T=1.6 sec, 1.7 sec, 1.8 sec and 2 sec were generated from a piston type wave generator. At 800 cm from the wave generator, horizontally slotted submerged breakwater of 100cm width,75cm length and 40 cm height were constructed with varying porosities of n=0.4, 0.5 and 0.6. Water level data were collected at six different locations for 12 unique run conditions. Using the measured data different hydrodynamic coefficients were calculated which include transmission co-efficient K t , reflection co-efficient, K r and wave energy loss co-efficient, K L . These co-efficient values were then, analyzed with respect to relative breakwater width (k.B), [where, k = wave number (2π/L), B = breakwater width] and porosity of breakwater. For the comparison, hydraulic performance of solid rectangular submerged breakwater of 40 cm height and 100 cm width was also reviewed which was modeled in the same laboratory under same wave condition of T=1.6,1.7 1.8 and 2.0 seconds and a still water depth of 50 cm. Experimental results from the porous breakwater and subsequent comparison of the results with solid breakwater indicate that, for transmitting less wave energy through the breakwater, maximum transmission co-efficient, K t = 0.526 was obtained for porous breakwater with the lowest porosity (n=0.4) for T = 1.6 sec whereas for the solid breakwater maximum K t = 0.5 was obtained for T=1.6 second. In terms of wave height, percentage wave height reduction was maximum 47% for porous breakwater whereas it was 68% for solid breakwater both at T=1.6 second. The hydrodynamic performance shows a significantly higher wave height reduction percentage for solid breakwater as anticipated by the physics of the interaction of the breakwater and the wave too. Besides, the position of wave breaking for different case scenario for both types of breakwater were recorded and analyzed which demonstrates that for porous breakwater waves tend to transmit through the slots and break at a certain distance beyond the breakwater whereas in case of solid breakwater, waves tend to break before or on the breakwater. [ABSTRACT FROM AUTHOR]

The stabilization process of coastal dunes is complex, involving feedback mechanisms and lag times between changes in climatic conditions, vegetation establishment and dune movement. In this study our aim was to examine changes in dune activity and in the establishment of foredunes on Moreton Island, Australia. We used historical aerial photos, satellite images and Lidar data to quantify changes in bare sand areas, dune movement rates, foredune development and coastline changes between 1944 and 2015. We used wind data (1957–2016), to quantify changes in sand drift potential (DP) and in wind directionality, and wave data (1977–2016) to examine changes in wave height and wave direction. We found that transgressive dunes on Moreton Island have started stabilizing in the early 1970s, after a series of continuous foredunes developed on the eastern coast of Moreton Island, in spite of the increase in DP values. Foredunes have started establishing in the 1960s and 1970s during a period of lower wave height and decreased wind directionality. Once established, these foredunes have diminished sand supply to the transgressive dunes, causing a phase shift in the state of dune activity on the island. Coastal dune activity should therefore be examined over time scales of several decades at least, in order to quantify trends and to understand the underlying and causes to observed processes. Understanding the factors responsible for foredune formation is important for explaining dune stabilization on Moreton Island. [ABSTRACT FROM AUTHOR]

Knowledge of design waves with long return periods forms an essential input to many engineering applications, including structural design and analysis. Such extreme or long-term waves are conventionally evaluated using observed or hindcast historical wave data. Globally, waves are expected to undergo future changes in magnitude and behavior as a result of climate change induced by global warming. Considering future climate change, this study attempts to reevaluate significant wave height (Hs) as well as average spectral wave period (Tz) with a return period of 100 years for a series of locations along the western Indian coastline. Historical waves are simulated using a numerical wave model forced by wind data extracted from the archives of the National Center for Environmental Prediction and the National Center for Atmospheric Research, while future wave data are generated by a state-of-the-art Canadian general circulation model. A statistical extreme value analysis of past and projected wave data carried out with the help of the generalized Pareto distribution showed an increase in 100-year Hs and Tz along the Indian coastline, pointing out the necessity to reconsider the safety of offshore structures in the light of global warming. [ABSTRACT FROM AUTHOR]

Coastal erosion is recession of the shoreline and loss of land area due to action of waves, currents and wind. In order to mitigate coastal erosion, submerged reef is one of the alternatives coastal protection measures provided to reduce the wave energy. Site specific coastal protections in the form of alternative cross-sections of submerged reefs have been evolved at the varying tidal range of micro to macro along the Indian Coast. The wave flume tests were conducted to ensure the hydraulic stability of different alternative cross-section of submerged reefs to withstand the design wave conditions. In order to hold the nourished sand, a series of submerged offshore reefs with sand-filled Geo-textile tubes have also been proposed at different sites. The submerged offshore reefs with sand-filled Geo-textile tubes have been provided and are performing well. The design of submerged offshore reefs through wave flume studies for the hydraulic stability and wave transmission has been discussed in this paper. [ABSTRACT FROM AUTHOR]

The bow wave generated by a ship hull that advances at constant speed in calm water is considered. The bow wave only depends on the shape of the ship bow (not on the hull geometry aft of the bow wave). This basic property makes it possible to determine the bow waves generated by a canonical family of ship bows defined in terms of relatively few parameters. Fast ships with fine bows generate overturning bow waves that consist of detached thin sheets of water, which are mostly steady until they hit the main free surface and undergo turbulent breaking up and diffusion. However, slow ships with blunt bows create highly unsteady and turbulent breaking bow waves. These two alternative flow regimes are due to a nonlinear constraint related to the Bernoulli relation at the free surface. Recent results about the overturning and breaking bow wave regimes, and the boundary that divides these two basic flow regimes, are reviewed. Questions and conjectures about the energy of breaking ship bow waves, and free-surface effects on flow circulation, are also noted. [ABSTRACT FROM AUTHOR]

To study the seismic response of floating roof storage tank with the base isolation, the floating roof is assumed as a homogeneous rigid circular plate, the vibration form of wave height is assumed as linear distribution along the radius. By the velocity potential theory, the velocity potential function of the liquid movement and the expression of base shear and overturning moment are established and by the plate vibration theory and energy principle, the motion equation for the floating roof and the motion equation for the tank system are presented, respectively. With the time history analysis, the seismic responses for the isolated floating roof storage tanks are studied. The numerical results show that the fundamental frequency of isolation is applicable to be 2 ~ 3 rad/s, while the damping ratio of isolation is O. 1. The damping rates of I , II site are better than those of III, IV site. The effects of different sites on wave height are different, and the ratio of height to diameter has little effect on the seismic response of the isolated floating roof storage tanks. [ABSTRACT FROM AUTHOR]

It was discovered in the process of manufacturing that the parameters of a fabric structure change after taking it away from the weaving loom and its stabilisation. This is probably due to the geometry of the fabric cross-section, i.e. changes in yarn cross-section projections and the fabric structure phase. Thus in this study attempts were made to make an analysis of changes in the parameters of fabrics of different raw material and the dependence on the integrated fabric structure factor ?. Similar research of the above changes had not been performed previously. However, it is very important to study them in order to identify changes in their geometric structure when the fabric structure was stabilised. [ABSTRACT FROM AUTHOR]

To study vertical steel storage tank isolation design and analysis methods, three-stage design method is used as the optimal design of base isolated for the vertical steel storage tank. In the first stage, from rigidity theory, the wave height amplification effect caused by the base isolated is considered firstly, and the wave amplification is limited to the boundaries of isolation design to adjust the frequency. In the second stage, from elasticity theory, the base shear of isolation is analyzed, and the damping effect of the base isolated is studied. In the third stage, the square and square root results of the base shear obtained by the rigid theory and the theory of elasticity are used as a design basis. In theory, the only guarantee the effect of the two effects, but also for engineering design and analysis provides a easy to understand method of analysis. The results showed that this approach to design can not only achieve the right base shear reduction, but also be capable of controlling the amplification effect of wave height. [ABSTRACT FROM AUTHOR]

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Abstract: An experimental investigation on the initiation and development of bed forms on a bed of fine silica sand was conducted under alluvial flow conditions in a laboratory flume with a diverging channel. The main aims of the study were to assess: i) the steepness of bed forms in the transition stage of development; and ii) the threshold height of wavelets (ηt ) that triggered the start of ripple development. Detailed bed profile measurements were carried out using an acoustic Doppler probe, traversed longitudinally over the sediment bed at various experimentation times. The bed form dimensions were extracted from such bed profile records and analysed for the wavelet, transition and equilibrium stages. It was found that the steepness of ripples in the transition and equilibrium stages were similar, confirming predictions of previous mathematical model simulations. A lognormal distribution fitted the wavelet length data. The wavelet threshold height was estimated as ηt ≈ 7 mm, or y+ ≈ 80 in wall units. Such a height magnitude suggested that ripple development could be triggered by the wavelets reaching the outer flow zone of a turbulent boundary layer. The ηt value obtained corresponded generally to the intersection point between two predictive equations for bed form dimensions. A formulation was developed to predict ηt as a function of the sediment grain size, which was confirmed for the fine sand used in this study. [Copyright &y& Elsevier]

During rough weather, navigation in Klaipėda port is risky because of the high wave penetration into the Klaipėda Strait from the Baltic Sea. Objectives of the present paper are to study wind and wave regimes in Klaipėda port water area and to develop the short wave propagation model at wind speeds of 15, 20 and 25 m/s and varying directions. The modelled wave parameters are significant wave height and wave disturbance coefficient. The software MIKE 21 BW (Boussinesq Wave Module) is used for the development of wave propagation model in the Klaipėda Strait. [ABSTRACT FROM AUTHOR]

When an oil spill occurs, a prompt response reduces significantly the impact. The preparedness and contingency plans are essential to identify the most appropriate technologies. Unmanned and autonomous vehicles (UAVs) is emerging as a powerful tool of strategic potential in the observation, oil tracking and damage assessment of an oil spill. The SpilLess project explored the suitability of these devices to be the first-line response to an oil spill. This work analyses the operational requirements related to environmental parameters following a two steps approach: 1) Environmental characterization from long wind and waves time series and modelling; 2) Definition of the optimal periods for operating each UAVs. We have defined the periods in which each of these facilities acts best, confirming that the operational limits of UAVs are not significantly more restrictive than the traditional operations. UAVs should be included in contingency plans as available tools to fight against oil spills. • Unmanned vehicles (UAVs) increasingly used for coastal management over the last decade. • Adaptation of UAVs as an innovative technology for helping in the spreading microbial consortia and nutrients in an oil spill. • Operational conditions analysis to define the suitability of UAVs on clean-up operations. • Broad operative windows related to wind and sea state conditions in the NW Iberia • UAVs present similar weather limitations than others classical clean-up methodologies [ABSTRACT FROM AUTHOR]