Fluid In Tank Research Articles

Dynamic performance investigations of a full-scale unanchored thin-walled steel fluid storage tank via shake table tests

Theoretical models proposed in the literature and seismic design codes make the basis of analysis and the design procedures of fluid storage tanks. These models are derived based on many simplified and approximate assumptions. Under realistic conditions, however, different factors cause violation of these assumptions, causing the fluid flow and fluid–structure interaction (FSI) to diverge from theories. In this research work, 38 swept-sine tests and 63 seismic ground motions were applied to a full-scale highly flexible unanchored thin-walled stainless steel fluid tank. The experimental natural frequencies of the system for three different aspect ratios of 2.1, 2.8, and 3.5 were calculated and compared with the theoretical ones. Damping ratios for different modes were calculated using the half-power bandwidth analysis. Experimental results revealed discrepancies between the theoretical and experimentally detected natural frequencies, especially for the convective mode. Closer matches were found for the aspect ratios of 2.8 and 3.5, for the impulsive mode. Acceleration amplification factors at different heights of the shell were calculated which showed a nonlinear behaviour with a descending trend from the base to the mid-height and then an ascending one towards the fluid surface. Maximum acceleration amplification factor occurred at the surface of the fluid. The axial strains around the base are maximum and decrease bi-linearly towards the upper heights of the shell. Effects of the input excitation frequency content over the structural responses of the system were examined. Frequency characteristics of the input excitation considerably affected the maximum acceleration amplification factors and axial strains in the shell.

N-Acyl Homoserine Lactone Production by the Marine Isolate, Dasania marina.

Dasania marina (isolate SD1D, with 98.5% sequence similarity to Dasania marina DMS 21967 KOPRI 20902) is a marine bacterium that was isolated from ballast tank fluids as part of a biofilm study in 2014. Our previous work indicated that although this strain produced no detectable biofilm, it was the only isolate to produce N-acyl homoserine lactones (AHLs) in assays using the broad-range reporter strain, Agrobacterium tumefaciens KYC55. The goal of the current study was to determine the types of AHL molecules produced by the D. marina isolate using gas chromatography-mass spectroscopy (GCMS) and C4- to C14-AHL as standards. A time course assay indicated that the D. marina strain produced the highest level of AHLs at 20 h of growth. When extracts were subjected to GCMS, detectable levels of C8- and C10-AHL and higher levels of C12-AHL were observed. Interestingly, several biofilm-forming isolates obtained from the same source also produced detectable amounts of several AHLs. Of the isolates tested, a strain designated SD5, with 99.83% sequence similarity to Alteromonas tagae BCRC 17571, produced unstable biofilms, yet detectable levels of C6-, C8-, C10- and C12-AHL, and isolate SD8, an Alteromonas oceani S35 strain (98.85% sequence similarity), produced robust and stable biofilms accompanied by detectable levels of C8- and C12-AHL. All isolates tested produced C12-AHL at higher levels than the other AHLs. Results from this study suggest that quorum sensing and biofilm formation are uncoupled in D. marina. Whether the suite of AHLs produced by this isolate could modulate biofilm formation in other strains requires further study.

Development and assessment of a floating photovoltaic-based hydrogen production system integrated with storage options

The integrated system approach utilized in the current study represents an innovative approach to harnessing solar energy through a floating photovoltaic-based integrated plant featuring a diverse array of energy storage options. As part of this research, a solar energy system integrating both floating and concentrating solar technologies was designed at the specified site. Despite the constraints presented by the cold temperature at the chosen location, particularly during the winter months when solar irradiation is restricted, strategies are employed, such as exploiting the high albedo effect caused by the freezing of the water body, optimizing the application of solar radiation, and assuring the system's resilience and energy efficiency. Floating photovoltaic and concentrated solar panels are integral components of this advanced system, which is supplemented by underground hot and cold storage units, underground hydro-pumped storage, a multi-effect desalination system with freshwater storage, a lithium bromide absorption cooling system, and an alkaline electrolysis system for hydrogen and oxygen storage. This comprehensive energy strategy includes diverse storage and production technologies. The thermodynamic analyses and assessments employing the Engineering Equation Solver and the System Advisor Model provide some quantitative performance evaluations. The study considers time-dependent operational characteristics, illustrates the water withdrawal rates, energy and exergy efficiencies of the heating space temperature, inverter efficiency, GHI irradiance, mass, and volume values of the heat transfer fluid in both hot and cold tanks within thermal energy storage, annual cooling generation over a year, power production, hydropower storage, and hydrogen storage over a year. The system's concentrated solar panels are projected to generate an annual AC output of 180.79 GWh, with a yearly water usage of 14,055 m3, while floating panels are predicted to provide 7000 kWh with a 0.85 performance ratio. The overall energy efficiency of the current system is determined to be 51.76 %, and the exergy efficiency is found to be 55.41 %, respectively. Optimizing energy efficiency, utilizing diverse storage solutions, and utilizing aquatic environments minimizes environmental impact, and time-dependent analysis enhances perceptions of performance throughout different times and circumstances.

Static analysis and contact angle hysteresis study of bubbles in Chinese space station tank models under different gravity effects

In most space shuttle fuel tanks, a central column is used to secure the Propellant Management Devices. This study focuses on the distribution of fluids in such tanks. Microgravity experiments are conducted on the Chinese Space Station, and annular bubbles surrounding the central column have been observed for the first time. An in-depth study is carried out on the distribution and profile of these bubbles using perturbation methods and the Young–Laplace equation. Theoretical values for the gas–liquid interface morphology of annular bubbles under different gravity levels are obtained and compared with numerical simulation results, showing substantial agreement. The phenomenon of contact angle hysteresis of bubbles under gravity conditions was studied through simulation and theoretical analysis. Detailed analysis of the characteristics of contact angle hysteresis and corresponding drag resistance using the Wenzel model was carried out. Based on this, a numerical calculation program based on the shooting method was developed to obtain the morphology of the same bubble under different gravities. Furthermore, it was found that the theoretical maximum Bond number for circular bubbles suspended on the central column is 2, and it was observed that bubbles with equilibrium contact angles closer to 90° exhibit greater upward displacement of their centroids under varying gravity, providing theoretical support for bubble management in aerospace engineering.

A multiple-timing analysis of temporal ratcheting

We develop a two-timing perturbation analysis to provide quantitative insights on the existence of temporal ratchets in an exemplary system of a particle moving in a tank of fluid in response to an external vibration of the tank. We consider two-mode vibrations with angular frequencies ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\omega $$\\end{document} and αω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha \\omega $$\\end{document}, where α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} is a rational number. If α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} is a ratio of odd and even integers (e.g., 21,32,43\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ frac{2}{1},\\,\ frac{3}{2},\\,\ frac{4}{3}$$\\end{document}), the system yields a net response: here, a nonzero time-average particle velocity. Our first-order perturbation solution predicts the existence of temporal ratchets for α=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha =2$$\\end{document}. Furthermore, we demonstrate, for a reduced model, that the temporal ratcheting effect for α=32\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha =\ frac{3}{2}$$\\end{document} and 43\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ frac{4}{3}$$\\end{document} appears at the third-order perturbation solution. More importantly, we find closed-form formulas for the magnitude and direction of the induced net velocities for these α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} values. On a broader scale, our methodology offers a new mathematical approach to study the complicated nature of temporal ratchets in physical systems.Graphic abstract

Fuzzy System to Control a Liquid Mixing Tank

This paper aims to develop a fuzzy system to control the level and temperature of a fluid in a mixing tank by dynamically adjusting the flow rates of cold and hot liquids. The system involves a temperature and level loop, with the control variables being the rates of cold water and hot water flow, while also considering the outlet flow from the reservoir as a disruptive factor. The main goal of this control strategy is to maintain the liquid level and temperature within specified reference values. The system is a multivariable process that uses a fuzzy control system to develop a technique that, based on the state variables, can adapt the controller to achieve optimal control performance. In the development of this application, some linear controllers were tested, each implemented around specific regions within the phase plane. The designed controllers are then employed in conjunction with the fuzzy system to evaluate the system’s state variables. Therefore, an interpolation of these linear controllers is conducted, allowing for their application in a nonlinear system, with the aim of enhancing control performance near the boundaries between regions. The results show that the fuzzy approach is promising and provides convergence to the reference values of the liquid level and temperature in the mixing tank.

Experimental and numerical simulation of a storage tank connected to a flat-plate solar collector

In this study, the thermo--hydrodynamic behaviour of the heat transfer fluid in a storage tank connected to a domestic solar collector is investigated. In order to do this, a numerical simulation of the fluid inside the storage tank is performed using Ansys Fluent. The numerical results are then compared with experimental measurements, taken from a new design of a flat-plate solar collector, showing a good agreement.

Field experiment on performance of water source heat pump using underground rainwater tank as heat source

Research on heat sources for various heat pump (HP) systems is ongoing worldwide to achieve carbon neutrality and mitigate global warming. In this study, a rainwater (RW) tank HP (RWHP) using an underground RW tank as a heat source and heat sink was installed in an actual building and evaluated for its potential to provide cooling during the summer season. The water temperature of RW tank, the inlet and outlet fluid temperature, and the power consumption were measured. Using the collected data, the thermal stability of the RW tank and the performance of the RWHP were analyzed. In addition, the effect of the water level of the RW tank and precipitation was analyzed. As a result, the RW tank functioned as the heat sink for the HP during the cooling season. If the water level in the RW tank and the moisture content of the surrounding ground are high because of precipitation, the water temperature in the tank can be maintained at a relatively stable level. The coefficient of performance (COP) and system COP (COPsys) ranged 2.41–3.38 and 1.80–2.50, respectively. When the rainwater temperature in the RW tank increased, the COP and COPsys tended to decrease. Through this study, the data necessary for optimization through future mathematical modeling was collected. Also, the basic mechanisms of the temperature distribution of the RW tank and the performance of the RWHP were identified. Additionally, the operation method and means for improving the system were determined to increase the energy efficiency and broaden the applicability of the system.

Microbial Communities in Model Seawater-Compensated Fuel Ballast Tanks: Biodegradation and Biocorrosion Stimulated by Marine Sediments

Some naval vessels add seawater to carbon steel fuel ballast tanks to maintain stability during fuel consumption. Marine sediments often contaminate ballast tank fluids and have been implicated in stimulating fuel biodegradation and enhancing biocorrosion. The impact of the marine sediment was evaluated in model ballast tank reactors containing seawater, fuel (petroleum-F76, Fischer–Tropsch F76, or a 1:1 mixture), and carbon steel coupons. Control reactors did not receive fuel. The marine sediment was added to the reactors after 400 days and incubated for another year. Sediment addition produced higher estimated bacterial numbers and enhanced sulfate reduction. Ferrous sulfides were detected on all coupons, but pitting corrosion was only identified on coupons exposed to FT-F76. Aerobic hydrocarbon-degrading bacteria increased, and the level of dissolved iron decreased, consistent with the stimulation of aerobic hydrocarbon degradation by iron. We propose that sediments provide an inoculum of hydrocarbon-degrading microbes that are stimulated by dissolved iron released during steel corrosion. Hydrocarbon degradation provides intermediates for use by sulfate-reducing bacteria and reduces the level of fuel components inhibitory to anaerobic bacteria. The synergistic effect of dissolved iron produced by corrosion, biodegradable fuels, and iron-stimulated hydrocarbon-degrading microbes is a poorly recognized but potentially significant biocorrosion mechanism.

Cutting Fluid pH Value Maintenance in CNC Machine by Arduino Nano

Cutting fluid plays an important role in machining operations like milling, drilling, reaming, etc. In production industry such as automobile industries, aerospace industries, etc., soluble cutting fluids are mainly used for machining operations. The maximum service life of the cutting fluid is about 3 to 4 months in that industry, when they mixed with water, the cutting fluid will get dried out or converted into vapour due to heat generation and due to friction between the cutting tool and the components. The repeated use of cutting fluid for machining operations, the chemical and physical property of the cutting fluid will be changed. The proper mixing ratio of cutting fluid can be done with the help of Arduino nano device and valves, sensors. Automatic cutting fluid filling process can be done by proper Arduino coding. In the present study, the pH sensor is used to detect the pH level of cutting fluid and the Solenoid valves are electromagnetic valves, these valves are used to maintain the proper flow of cutting fluid and water mixture ratio, whenever the cutting fluid pH value differs from the fixed value, the pH sensor will indicate in Arduino nano. The mixing of cutting fluid and water is carried out by stirrer mechanism, which is attached at just above the cutting fluid tank. Control valve is used to control the flow of cutting fluid during the machining operation. The electric signal from touch sensor will stops automatically, when the cutting fluid in the tank reaches its maximum limit. In this paper, cutting fluid pH value is maintained automatically by Arduino nano device for CNC Machine in industries is discussed.

Encapsulation of radioactive stainless-steel corrosion products sludge in aluminum using hot isostatic pressing process and treatment suitability assessment

Sludge powder with stainless-steel corrosion products generated from the long-term contaminated-waste fluid tank of a nuclear power plant was compressed into a cylindrical shape by a hydraulic press at room temperature. The cylindrical sludge was wrapped in molten Al in a carbon crucible and cooled and hardened at room temperature. Subsequently, the encapsulated sludge was heated and compressed by the hot isostatic pressing (HIP) process. The Al capsule was melted and separated from the cylindrical solidified sludge. In solidified sludge, the leachability indices of Co, Fe, Cr, and Ni were 17.5 ± 0.0736, 13.4 ± 0.0952, 11.2 ± 0.0952, and 16.9 ± 0.0739, respectively. This satisfies Korea's criterion for the disposal of solidified radioactive waste, which is a leachability index of more than 6.

Comparative Analysis of Mechanical Water Level Tank and Human Fluid Flow

Abstract Fluid flow in the human body can be modeled using a water-level tank, a commonly used mechanistic approach in mechanical engineering for fluid transport processes. Postoperative fluid data from patients undergoing cardiac surgery is used to estimate fluid flow dynamics and total body water in the human body. This simplified model provide a basic understanding of the dynamics of fluid flow processes in the human body and could aid in modeling distribution of fluids in compartments.

Complex-geometry simulations of transient thermoelasticity with the Shifted Boundary Method

We propose a formulation of the Shifted Boundary Method, an immersed/embedded/unfitted boundary method, for transient thermo-elasticity problems characterized by very complex geometries. With an extensive set of numerical experiments, we demonstrate that the SBM performs accurately and robustly, even when the geometry is represented in stereolithography format (STL, or Standard Tessellation Language) with gaps and overlaps. We conclude with a thermoelastic analysis of an advanced fluid tank design, obtained with topology optimization methodologies and a candidate for additive manufacturing processes. This final example represents what is foreseen as the typical application of the SBM in the context of the simulation of additively manufactured components.

An Eulerian based geometry conforming grid-block dynamic mesh refinement for the lattice Boltzmann method

An algorithm for a three-dimensional fine-grid block encompassing a moving solid body using a multi-relaxation time model of the lattice Boltzmann method is proposed and developed. In this numerical framework, a geometry-conforming fine block shifts a coarse lattice unit as the object translates by same amount. The effective utilization of higher-order spatial interpolation has been demonstrated in place of the commonly used low-order temporal interpolation in traditional grid refinement techniques within the lattice Boltzmann method. The successful application of this method has been showcased through three distinct cases: the settling of a solid sphere in a fluid tank under the influence of gravity, hovering motion of an elliptic airfoil, and the “clap and fling” motion of an insect wing. In this regard, various interpolation schemes based on the location of nodes in the overlapping zones of fine and coarse block are discussed. In addition, two cases were evaluated, case 1 where distributions are interpolated and case 2 where macroscopic variables are directly interpolated. It was observed that both interpolations gave same computational accuracy for low Reynolds number [∼O(102)]. However, as Re is increased [∼O(103)], direct interpolation of macroscopic variables proved erroneous and resulted in a large deviation in fluid forces and is not recommended. The geometry-conforming dynamic mesh refinement results in a substantial decrease in computation time, approximately 90%, along with a memory reduction of about 80% compared to the fully refined counterpart.

Natural-Language-Processing-Enabled Quantitative Risk Analysis of Aerial Wildfire Operations

Aerial wildfire operations are high risk and account for a large number of firefighter deaths. The increasing intensity of wildfires is driving a surge in aerial operations, as well as interest to improve system safety and performance. In this work, wildfire aviation mishaps documented using the Aviation Safety Communiqué (SAFECOM) system are analyzed using a previously developed framework for hazard extraction and analysis of trends. Hazards and specific failure modes are extracted from the narrative data in SAFECOM forms using natural language processing techniques. Metrics for each hazard (including the frequency, rate, and severity) are calculated. We examine whether these metrics change over time and whether they are related to metadata, such as region and aircraft type. The results of the hazard analysis are presented in a risk matrix, identifying the highest and lowest risk hazards based on the rate of occurrence and average severity. The analysis of all SAFECOM reports indicated that the jumper operations hazards were classified as high risk; whereas the hydraulic fluid malfunctions, bucket or tank failures, retardant loading and jettison failures, prescribed burn operations, cargo letdown failures, and severe weather were classified as serious risk. However, when applied to a specific operational scenario, risk levels change across hazards.

Numerical Simulation of a Partly Filled Rectangular Tank with Fuel Oil

Sloshing refers to a certain kind of fluid movement that changes as it progresses. It possesses properties that are both nonlinear and exceedingly unpredictable, and these properties affect the tank wall. This effect may lead to structural wear, which in turn can cause the tank to fail. Benzene and gasoil liquids are used to test the effect of sloshing liquid and accompanying pressure on the wall tank caused by the baffles in partially full fluid tanks. To attain this, modeling of the interaction between fluid and structure is justified using the finite element analysis while the ANSYS Fluent is used to do the simulation. Specifically, the analysis enables us to anticipate the pressure that is being exerted on the shield, the influence of sloshing on the grounding point forces, and the size of the sloshing waves. The pressure distribution over time indicates a reduction of pressure on the tank wall as a result of utilising a vertical baffle if compared to the case of a tank wall without a baffle. The usage of vertical shields allows for around 20% of the greatest contact energy to be deflected, which is attributed to the potential of generating turbulence and vortices by the baffle.

Solar energy harvesting from the photovoltaic/thermal (PV/T) pavement: Energy performance analyses and comparison considering ground influence

Under the carbon neutrality targets, the easy-installation low-investment photovoltaic (PV) technology is vital, while the limited urban rooftop area and high building façade cost limit the onsite PV installation. Thus, harvesting solar energy from the road, namely pavement-integrated photovoltaic/thermal (PIPV(T)) technology, is promising. The 2D finite element PIPV(T) models are proposed and verified through the field test within 3% (cell temperature) and 7% (PV output) mean absolute percentage error. The parametric analyses on system designs (water tank volume, water velocity, water inlet temperature), weather conditions (solar irradiance, wind velocity), and ground boundary condition influence are conducted. The water inlet temperature acts as a minor factor, while tank volume and fluid velocity are crucial, i.e., a 32.76% thermal efficiency increase for a 125 L tank volume increase. Results show that over 0.2 L/s water flow rate is recommended for a 100 L water tank, and the solar irradiance increase adds to the thermal efficiency to 41.47% under 1000 W/m2 with 11.38% ground influence. The annual system performances for southern and northern metropolises are compared, with water tank variation considered. Results show that a small water tank leads to high temperature and low system thermal efficiency at 9.3% and 12.17% in Hong Kong and Beijing.

Thermodynamic analysis of novel one-tank liquid gas energy storage system based on ammonia-water mixture fluid

Given the growing focus on energy storage systems, liquid gas energy storage (LGES), which is globally applicable, is being rapidly developed. However, the liquefaction issue of efficiently liquefying the working fluid within LGES remains a significant constraint on its development. In this study, the ammonia-water mixture is used as the working fluid in LGES to address the liquefaction issue, and the number of storage tanks is reduced to one to improve the energy density. Two different one-tank liquid ammonia-water mixture energy storage systems (one-tank LAWES) are proposed and compared. Configuration 1# (C1) features a simple condenser, whereas configuration 2# (C2) incorporates a modified liquefaction process that is similar to some LGES systems. The energy and exergy performances of these two configurations are evaluated and compared. The parametric sensitivity analysis is conducted, and the relationship between the one-tank LGES and Carnot Battery is discussed. The results show that C1 with a simple condenser has better performance, and its roundtrip efficiency and energy density under baseline condition are 48.65 % and 55.03 kWh∙m−3, respectively. Moreover, based on the exergy analysis, thermal energy storage unit 2 is the first priority for improvement in both configurations. The ammonia concentration of the fluid in the storage tank has a slightly positive effect on the roundtrip efficiency of C2, whereas it has a slightly negative effect on the roundtrip efficiency of C1. The one-tank LGES is a Carnot Battery because electricity is stored as thermal exergy rather than mechanical energy.

BEM modeling for the hydrodynamic analysis of the perforated fish farming vessel

As the aquaculture industry progresses from coast to deep sea, the higher strength requirement for aquaculture infrastructure has promoted the rapid development of fish farming vessels. To consider the interaction between waves and floating aquaculture systems, the hydrodynamic and seakeeping performances of the perforated fish farming vessel are studied by using an efficient numerical method, which combines porous theory and potential flow theory. The linear pressure drop porous condition is incorporated into the potential flow boundary conditions. The submerged porous shell of negligible thickness is represented by a dipole distribution to construct a boundary element method (BEM) modeling the wave interactions with a fish farming vessel. A perforated fish farming vessel with openings on the sidewalls is taken for an example, and the effects of the openings and other important factors such as the opening ratio of the metal net and the number of openings on the motion response, wave load, and hydrodynamic coefficients are analyzed by numerical stimulation. The variation of the opening ratio is represented by the discharge coefficient. The natural frequencies of the modified fish farming vessel are significantly altered, and an improved seakeeping performance is exhibited, especially in terms of the roll, because of wave energy dissipation by the porous shell. The added mass and damping in the low frequency range significantly change due to the effect of tank fluid, which decreases as the discharge coefficient and the number of openings increase. With the increases in the discharge coefficient and the number of openings, the hydrodynamic coefficients of heave increase, with a lower natural frequency. The wave loads of surge, heave, and pitch exhibit a fluctuating behavior within a certain frequency range and become pronounced with the effect of tank fluid increases. The spectral analysis results indicate a better performance of the perforated vessel in the extreme sea state, making it feasible for offshore operations.

Resonant triad interactions of gravity waves in cylindrical basins

We present the results of a theoretical investigation into the existence, evolution and excitation of resonant triads of nonlinear free-surface gravity waves confined to a cylinder of finite depth. It is well known that resonant triads are impossible for gravity waves in laterally unbounded domains; we demonstrate, however, that horizontal confinement of the fluid may induce resonant triads for particular fluid depths. For any three correlated wave modes arising in a cylinder of arbitrary cross-section, we prove necessary and sufficient conditions for the existence of a depth at which nonlinear resonance may arise, and show that the resultant critical depth is unique. We enumerate the low-frequency triads for circular cylinders, including a new class of resonances between standing and counter-propagating waves, and also briefly discuss annular and rectangular cylinders. Upon deriving the triad amplitude equations for a finite-depth cylinder of arbitrary cross-section, we deduce that the triad evolution is always periodic, and determine parameters controlling the efficiency of energy exchange. In order to excite a particular triad, we explore the influence of external forcing; in this case, the triad evolution may be periodic, quasi-periodic or chaotic. Finally, our results have potential implications on resonant water waves in man-made and natural basins, such as industrial-scale fluid tanks, harbours and bays.