Water Cages Research Articles

Rapid formation of carbon dioxide hydrate governed by the natural nano-clay for effective carbon dioxide capture

Gas hydrate can separate and capture enormous carbon dioxide (CO2) only using water cages. Capturing CO2 in hydrate form is viewed as a green and effective technology to reduce the global CO2 emission. However, the sluggish kinetics and high cost of kinetics promotors of CO2 hydrate formation limited the application of hydrate-based CO2 capture technology. Here, we used the nano-clay prepared by cheap natural clay to promote the formation kinetics of CO2 hydrate. At the low concentration range, the formation period of CO2 hydrate in the two-dimensional nano-clay dispersion was significantly shorter than that of the one-dimensional nano-clay dispersion. The induction time (5 min) obtained in vermiculite nanoflakes dispersion was shorter than most solid promotors of CO2 hydrate formation kinetics in reported works. Besides, we found that the water molecules near the negatively charged two-dimensional nano-clay surface were more likely to form the cage-like structure than those around the one-dimensional nano-clay surface. The similar hydrogen-bonded structure of the cage-like water with CO2 hydrate made them favorable for the CO2 hydrate formation. These results shed light on the design of the effective kinetics promotors of CO2 hydrate and contribute to develop the hydrate-based CO2 capture technologies.

Interactions between small organic molecules and water measured using pressure perturbation calorimetry

Aqueous liquid mixtures play a critical role in many biological and chemical processes. Solutes including sugars, sugar alcohols, carboxylic acids, alcohols and acetone can affect the hydrogen-bonded structure of water and this can be measured using pressure perturbation calorimetry (PPC). In binary water–solute mixtures, Δ(∂CP/∂P)T is a measure of the structure of the water component. At low alcohol concentrations, negative Δ(∂CP/∂P)T values are consistent with clathrate-like water cages around the alkyl moieties. Conversely, when solutes hydrogen bond with water it interferes in the formation of “ice-like” water and is observable as a positive Δ(∂CP/∂P)T. The Δ(∂CP/∂P)T at increasing concentrations of ethanol, acetone and acetic acid in water displayed very different behaviors. Ethanol–water mixtures had three distinct concentration dependent phases; the first, with ethanol surrounded by water molecules, followed by the ethyl groups self-associating breaking the clathrate-like cages, and the ethanol–water network displacing all of the bulk water. Acetic acid–water mixtures display nonlinearity in Δ(∂CP/∂P)T versus acetic acid concentration consistent with acetic acid self-interaction which interferes with acetic acid capacity to disrupt water structure. Acetone-water mixtures display linearity in Δ(∂CP/∂P)T versus acetone concentration which is consistent with acetone’s inability to hydrogen bond with other acetone molecules. The lack of negative Δ(∂CP/∂P)T values in acetic acid-water and acetone-water mixtures suggests there is sufficient self-association between these solutes to prevent clathrate-like water cage formation. PPC can provide invaluable insight into the behavior of aqueous binary mixtures.

Discovery of the final primitive Frank-Kasper phase of clathrate hydrates.

In weakly bound materials such as water, one of the three primitive Frank-Kasper (FK) phases, the Z phase, is long absent due to the relatively unstable framework. The Z phase in clathrate hydrate, which is known as the HS-I structure, has now been found by precise tuning of the molecular guest structure. In the crystal structure, the never stabilized combination water cage of two 15-hedra and two 14-hedra formed with its original symmetries, providing sufficient gas capacity to the 12-hedral cages. With the discovery of the final FK clathrate hydrate, guest design now enables engineering of weak interactions in any mix of the three, illuminating how to leverage properties of clathrates in the broadest sense.

Understanding the structures and interactions in gaseous mixtures of water-alcohol by high-resolution infrared spectroscopy

Interactions of water and chemical or bio-compound have a universal concern and have been extensively studied. For spectroscopic analysis, the complexity and the low resolution of the spectra make it difficult to obtain the spectral features showing the interactions. In this work, the structures and interactions in gaseous water and water-alcohol mixtures were studied using high-resolution infrared (HR-IR) spectroscopy. The spectral features of water clusters of different sizes, including dimer, trimer, tetramer and pentamer, were observed from the measured spectra of the samples in different volume concentrations, and the interactions of water and methanol/ethanol in the mixtures were obtained. In the analysis, a method based on principal component analysis was used to separate the overlapping spectra. In water-alcohol mixtures, when water is less, water molecules tend to interact with the OH groups on the exterior of the alcohol aggregate, and with the increase of water, a water cage forms around the aggregates. Furthermore, the ratio of the molecule number of methanol in the aggregate to that of water in the cage is around 1:2.3, and the ratio for ethanol is about 1:3.2.

Unveiling the effect of H2S concentration in CH4 hydrate formation and growth: A molecular dynamics study

We used molecular dynamics method to simulate the formation and growth of CH4 hydrates with different concentrations of H2S. At the large scale of simulation time, 10000 ns, it is unlikely to form hydrates at 10 MPa and 260 K if there are only CH4 and water; and if there was a small proportion of H2S in the gas, hydrates would easily form. When the molar concentration of H2S in the gas is 1 %, the formed hydrate is unstable and will eventually disintegrate, leaving the box in a two-phase state of gaseous and liquid. In contrast, at molar concentrations of 5 % or higher of H2S, hydrate formation is accelerated, and the hydrate will grow continuously. However, it is not structure I type as expected. These views are supported by the changes in F3 and F4 order parameters, numbers of different cage types, and the number of water molecules belonging to different states. Moreover, since the formation of hydrates is an energy reduction process, we can easily develop inhibitors targeted at hydrates in actual production and gas transportation. According to IGMH analysis, only van der Waals interactions occur between gas molecules inside the cages and the water cage.

Physical breakdown of CH4 hydrate under stress: a molecular dynamics simulation study

As a solid energy source, CH4 hydrate will inevitably break down physically as the result of geological movement or exploitation. Here, the molecular dynamics method was employed to simulate the uniaxial-deformation behavior of structure I (sI type) CH4 hydrate under stress. The stress increases regardless of whether the hydrate is stretched or squeezed, and other physical parameters also changed, such as hydrate cage numbers, order parameters, and the number of water molecules. A noticeable difference is observed between the two systems. Upon stretching, the stress immediately recovers to 0 GPa once the hydrate is completely stretched apart. During the squeeze process, the stress is ultimately not zero since solid and liquid are always in contact. When the hydrate is stretched apart, about 5% of water molecules change from solid to liquid, about 7.8% of CH4 molecules lose their shelter and become free due to the disintegration of water cages. While in the squeezing process, large cages (51262) are crushed more easily than small cages (512); in the end, about 93.5% of large cages and 73% of small cages are crushed, and approximately 87.5% CH4 is released from the cages. In mining CH4 hydrates, caution must be exercised, as if the hydrates break as a result of stress, a large release of CH4 may pose a security risk.

Chemical Approach to Control Hydrate in Offshore Gas Production Facilities

- Hydrate formation presents a significant operational challenge in offshore oil and gas production, primarily due to the potential formation of hydrate plugs which obstruct fluid flow, thereby posing serious flow assurance risks. Additionally, these solid, crystalline, icelike structures, composed of low molecular weight gases (such as methane, ethane, and propane) encapsulated in hydrogen-bonded water cages, can aggregate into larger masses capable of damaging or rupturing pipelines. Such formations typically occur under the high-pressure and low-temperature conditions prevalent in subsea flowlines and cold-weather operations. This study employs the Prosper simulation software to model these complex thermodynamic and hydrodynamic conditions and to predict the effective dosages of chemical inhibitors required to prevent hydrate formation. Specifically, our simulations suggest optimal dosages of 35% wt. methanol (MeOH) and 45% wt. monoethylene glycol (MEG) for gas stream 1, and 22% wt. MeOH and 33% wt. MEG for gas stream 2. Based on these findings, we advocate the use of Prosper simulation software as a predictive tool for the strategic administration of hydrate inhibitors in offshore gas production facilities. This research contributes to the ongoing development of chemical strategies for hydrate management, providing a basis for improved safety and efficiency in hydrocarbon extraction processes.

Large-cage occupation and quantum dynamics of hydrogen molecules in sII clathrate hydrates.

Hydrogen clathrate hydrates are ice-like crystalline substances in which hydrogen molecules are trapped inside polyhedral cages formed by the water molecules. Small cages can host only a single H2 molecule, while each large cage can be occupied by up to four H2 molecules. Here, we present a neutron scattering study on the structure of the sII hydrogen clathrate hydrate and on the low-temperature dynamics of the hydrogen molecules trapped in its large cages, as a function of the gas content in the samples. We observe spectral features at low energy transfer (between 1 and 3meV), and we show that they can be successfully assigned to the rattling motion of a single hydrogen molecule occupying a large water cage. These inelastic bands remarkably lose their intensity with increasing the hydrogen filling, consistently with the fact that the probability of single occupation (as opposed to multiple occupation) increases as the hydrogen content in the sample gets lower. The spectral intensity of the H2 rattling bands is studied as a function of the momentum transfer for partially emptied samples and compared with three distinct quantum models for a single H2 molecule in a large cage: (i) the exact solution of the Schrödinger equation for a well-assessed semiempirical force field, (ii) a particle trapped in a rigid sphere, and (iii) an isotropic three-dimensional harmonic oscillator. The first model provides good agreement between calculations and experimental data, while the last two only reproduce their qualitative trend. Finally, the radial wavefunctions of the three aforementioned models, as well as their potential surfaces, are presented and discussed.

Molecular Dynamic Simulation Study on Replacement of Methane Hydrates with Carbon Dioxide Under Different Temperatures, Pressures, and Concentrations of Ethylene Glycol.

In order to alleviate the world energy resources crisis, the research and development of natural gas hydrates has a very important economic value and strategic significance. The CH4-CO2 replacement method can not only achieve geological storage of carbon dioxide but also more effectively mine natural gas hydrates. Based on molecular dynamics theory and the properties of natural gas hydrates, this paper delves into the replacement of methane hydrate with carbon dioxide under different temperatures, pressures, and concentrations of ethylene glycol (EG). We established a CO2-Hydrate model and three CO2/EG-Hydrate models with different concentrations of EG, and we simulated the radial distribution function (RDF), mean square displacement (MSD), and relative density distribution of each particle in the system in different conditions. The higher the temperature, the more unstable the methane hydrates are, and the methane hydrates are more prone to decomposition. Compared with 280 and 290 K, the temperature of 270 K is more favorable for carbon dioxide molecules to enter the hydrate layer and form carbon dioxide hydrates. The changes in pressure have little impact on the decomposition of methane hydrates, the rupture of water cages of methane hydrates, and the number of carbon dioxide molecules entering the hydrate layer under temperatures of 280 K and pressures of 1, 4, and 7 MPa. But overall, a pressure of 1 MPa is more conducive for carbon dioxide molecules to enter the hydrate layer and form carbon dioxide hydrates. Adding EG to CO2 molecules can inhibit the decomposition of methane hydrates. However, the higher the concentration of EG, the faster the decomposition of methane hydrates. The degree of fracture of the water cages in methane hydrates is greater under pure CO2 conditions. Adding EG to CO2 molecules is more conducive for CO2 molecules to enter the hydrate layer and form carbon dioxide hydrates. This review is of great significance to improve the mining efficiency and CO2 storage efficiency of the replacement of natural gas hydrates with CO2.

Precision Aquaculture: A Way Forward for Sustainable Agriculture

The escalating demands for food, fiber, energy, and water due to swift population growth have underscored the necessity for the sustainable utilization of natural resources. The advent of precision farming tools and machinery since the 1990s has markedly enhanced productivity and optimized the employment of inputs in aquaculture. The burgeoning connectivity in rural regions and its improved integration with data from sensor systems, remote sensors, equipment, and smartphones have paved the way for innovative concepts in Digital Aquaculture. Automation is the most effective strategy to manage situations, augment productivity, and reduce manufacturing costs. Biosensors are deployed to control unidentified sensor-based remotely and guided aerial vehicles to apply chemicals or fertilizers while monitoring water quality. A sophisticated aeration system manages the concentration of dissolved oxygen. Another critical aspect is the administration of feeding and automatic biomass estimation. Robotics and automatic feeders are employed in ponds and cages to minimize feed wastage and the Feed Conversion Ratio (FCR), with these tools being dependent on the behaviour of the organisms and the water condition. Post-harvest, farmers acquire information on biomass estimation to attain optimal yield. The most vital element is the automatic monitoring of the health and welfare management of the organism to detect any challenging situations or early signs of anomalies. An underwater surveillance system, a camera-based visual system, collects data on water quality, organism activity, feeding, cage biofouling, and net cleaning. Automation is poised to shape the future of the aquaculture industry to make the nations agriculture sustainable.

Female tilapia, Oreochromis sp. mobilised energy differently for growth and reproduction according to living environment

This study was conducted to investigate the energy mobilisation preference and ionoregulation pattern of female tilapia, Oreochromis sp. living in different environments. Three different treatments of tilapia as physiology compromising model were compared; tilapia cultured in recirculating aquaculture system (RAS as Treatment I—RAS), tilapia cultured in open water cage (Treatment II—Cage) and tilapia transferred from cage and cultured in RAS (Treatment III—Compensation). Results revealed that tilapia from Treatment I and III mobilised lipid to support gonadogenesis, whilst Treatment II tilapia mobilised glycogen as primary energy for daily exercise activity and reserved protein for growth. The gills and kidney Na+/K+ ATPase (NKA) activities remained relatively stable to maintain homeostasis with a stable Na+ and K+ levels. As a remark, this study revealed that tilapia strategized their energy mobilisation preference in accessing glycogen as an easy energy to support exercise metabolism and protein somatogenesis in cage culture condition, while tilapia cultured in RAS mobilised lipid for gonadagenesis purposes.

The influence of ionic liquids with heterocyclic cations on CO2 hydrates formation

Kinetic characteristics of CO2 hydrates formation in the presence of eight ionic liquids with heterocyclic cations and [PF6]- anion were experimentally investigated here. It is found that the imidazolium ionic liquids with short substituted alkyl chains can inhibit CO2 hydrates formation. Increasing the alkyl chain length can alleviate the nucleation inhibition effect, and 1-hexadecyl-3-methylimidazolium hexafluorophosphate([C16mim][PF6]) with a concentration of 10 wt% even shows a slight promotion effect comparing to the pure water. In contrast, adding pyrrolidinium, piperidinium and pyridinium ionic liquids increases the nucleation temperatures, shortens the induction times and enhances the CO2 consumption. Based on DFT calculations and MD simulations, it is inferred that the strong binding energy between H2O and 1-ethyl-imidazolium hexafluorophosphate([Emim][PF6]) plays a main role on its inhibition behavior during CO2 hydrates formation. The H2O-H2O RDF curves of N-butyl pyridinium hexafluorophosphate([OPy][PF6]), N-butyl-N-methylpiperidinium hexafluorophosphate([PP14][PF6]) and N-butyl-N-methylpyrrolidinium hexafluorophosphate([PY14][PF6]) aqueous systems exhibit three peaks which become intensified and narrow with time, while [Emim][PF6]-containing system only has a single peak due to its strong interaction with water and thus inhibits the water-water attraction. In addition, RDF peaks of H2O–[PF6]- become weak gradually with time, implying that the anion [PF6]- does not engage in the structures of water cages.

Encapsulation of charged halogens by the 512 water cage.

This study focuses on the encapsulation of the entire series of halides by the 512 cage of twenty water molecules and on the characterization of water to water and water to anion interactions. State-of-the-art computations are used to determine equilibrium geometries, energy related quantities, and thermal stability towards dissociation and to dissect the nature and strength of intermolecular interactions holding the clusters as stable units. Two types of structures are revealed: heavily deformed cages for F- indicating a preference for microsolvation, and slightly deformed cages for the remaining anions indicating a preference for encapsulation. The primary variable dictating the properties of the clusters is the charge density of the central halide, with the most severe effects observed for the F- case. For the remaining halides, the anion may be safely viewed as a sort of "big electron" with little local disruptive power, enough to affect the network of non-covalent hydrogen bonds in the cage, but not enough to break it. Gibbs energies for dissociation either into cavity and halide or into water molecules and halide suggest that, in a similar way as to methane clathrate, a more weakly bonded complex that has been detected in the gas phase, all halide containing clathrate-like structures should be amenable to experimental detection in the gas phase at moderate temperature and pressure conditions.

Novel vermiculite/tannic acid composite aerogels with outstanding CO2 storage via enhanced gas hydrate formation

Gas hydrate-based CO2 storage, using only water cages, provides an environmentally friendly and energy-efficient solution to reduce greenhouse gas emissions. However, the sluggish formation kinetics of gas hydrate is hindered by the limited reaction interfaces, thereby impeding the practical utilization of hydrate-based greenhouse gas storage. Herein, we reported a novel strategy to fabricate natural vermiculite and tannic acid composite aerogels as the effective substrates for boosting CO2 hydrate formation. The results show that the formation kinetics of CO2 hydrate in the aerogels exhibits composition dependence and an outstanding CO2 storage capacity of 130.1 v/v (corresponding to 0.114 mol CO2/mol water). Inverse gas chromatography was used to analyze the surface energy and its components of the aerogels. Raman spectra and nuclear magnetic resonance were used to unravel the water molecule assembly and states. The CO2 uptake capacity can be further improved by compressing the aerogel to 75 % of the original volume, showing an impressive storage capacity of 146.8 v/v. The as-made aerogels demonstrated outstanding cycle stability and short induction time for CO2 hydrate formation. The results of this study pave the way for designing effective CO2 hydrate promoters and facilitating promising CO2 capture and storage technologies via gas hydrate.

Molecular simulation of imperfect structure I CO2 hydrate growth in brine.

In order to investigate the viability of carbon dioxide (CO2) storage in seawater, molecular dynamics techniques were employed to study the dynamic evolution of CO2 hydrate in saline water. The simulation was conducted under specific conditions: a temperature of 275 K, a pressure of 10 MPa and a simulated marine environment achieved using a 3.4 wt% sodium chloride (NaCl) solution. The total simulation time was 1000 ns. The results of the simulation indicate that the pre-existence of CO2 hydrate crystals as seeds leads to rapid growth of CO2 hydrate. However, analysis of the F3 and F4 order parameters reveals that the hydrate does not meet the standard values of the perfect structure I (sI) type, confirming the existence of an imperfect structure during the simulation. Additionally, the changes in the number of different phase states of water molecules during the hydrate growth process shows that there are always some liquid water molecules, which means some water molecules fail to form solid water cages. Further investigation suggests that the presence of Na+ and Cl- hampers the hydrogen bonds between water molecules, resulting in incomplete cage structures. By analyzing the density variations in the system, it is observed that CO2 hydrate, with a density of around 1.133 g cm-3, forms rapidly, surpassing the average density of seawater. This density increase facilitates the efficient and swift containment of CO2 on the seabed, thereby supporting the feasibility of the CO2 storage theory.

Influence of stocking density and environmental factors on the expression of insulin-like growth factors in cage-reared butter catfish (Ompok bimaculatus, Bloch 1794) within a large reservoir ecosystem.

In vertebrates, insulin-like growth like factors (IGFs) play an important role in growth and other physiological processes. The GH-IGF axis is considered a valuable tool to monitor fish growth performance. Herein, we report the molecular characterization of igf-1, igf-2, and β-actin transcripts and relative expression of igf-1 and igf-2 in the liver and muscle tissue of cage-reared butter catfish, Ompok bimaculatus, in response to different stocking densities (T1, 15 fingerlings m-3; T2, 25 fingerlings m-3; and T3, 35 fingerlings m-3) over 180days of culture duration. The length of the partial amplified transcript sequence of Obigf-1, Obigf-2, and Obβ-actin was 325, 438, and 924bp, respectively. Phylogenetically, Obigf-1 and Obigf-2 were closely clustered with catfishes, viz., Clarias magur, Bagarius yarrelli, and Silurus asotus. The expression of igf-1 was significantly downregulated in the liver at higher densities after 120days as biomass in the cages increased, while igf-2 expression did not change with the stocking densities over the culture period. Cortisol concentration was significantly elevated in T3 groups post 150days of the culture period and correlated negatively with the expression of igf-1 (p < 0.05) and igf-2 (p > 0.05). Environmental parameters, pH, TDS, hardness, conductivity, and alkalinity showed a significant positive correlation with hepatic IGF expression. Our study indicates that the liver-derived igf-1 plays a more important role in the regulation of growth in response to culture density in the species studied, and thus, igf-1 can be used effectively as a biomarker for growth. Furthermore, this study will help in planning a proper harvest schedule and optimize the culture practices of O. bimaculatus in an open water cage system.

Atomistic-geometry inspired structure-composition-property relations of hydrogen sII hydrates

Gas hydrates are crystalline inclusion compounds formed by trapping gas molecules inside water cages at high pressures and low temperatures. Hydrates are promising materials for hydrogen storage, but their potential depends on understanding their mechanical properties. This work integrates density functional theory (DFT) simulations with a geometry-inspired composite material model to explore the bulk moduli of structure II hydrogen hydrates subjected to pressure loads of − 0.2 to 3 GPa, representative of the hydrogen hydrate formation conditions. Our findings reveal that structure II hydrate comprises a bi-continuous composite of small and large cages with nearly equal volume fractions. The bulk modulus increases with rising pressure but decreases with increasing composition. Notably, these results align closely with the ideal laws of mixtures, especially at low pressures and compositions, where cage interactions are minimal. This integrated DFT-laws of mixtures methodology provides a key database for fast estimation of hydrate mechanical properties without costly computations.

Understanding why constant energy or constant temperature may affect nucleation behavior in MD simulations: A study of gas hydrate nucleation.

Molecular dynamics simulations have been widely used in exploring the nucleation behavior of many systems, including gas hydrates. Gas hydrates are ice-like solids in which gas molecules are trapped in water cages. During hydrate formation, a considerable amount of heat is released, and previous work has reported that the choice of temperature control scheme may affect the behavior of hydrate formation. The origins of this effect have remained an open question. To address this question, extensive NVE simulations and thermostatted (NPT and NVT) simulations with different temperature coupling strengths have been performed and compared for systems where a water nanodroplet is immersed in a H2S liquid. Detailed analysis of the hydrate structures and their mechanisms of formation has been carried out. Slower nucleation rates in NVE simulations in comparison to NPT simulations have been observed in agreement with previous studies. Probability distributions for various temperature measures along with their spatial distributions have been examined. Interestingly, a comparison of these temperature distributions reveals a small yet noticeable difference in the widths of the distributions for water. The somewhat reduced fluctuations in the temperature for the water species in the NVE simulations appear to be responsible for reducing the hydrate nucleation rate. We further conjecture that the NVE-impeded nucleation rate may be the result of the finite size of the surroundings (here the liquid H2S portion of the system). Additionally, a local spatial temperature gradient arising from the heat released during hydrate formation could not be detected.

Adsorption behaviors for clathrate hydrates of CO2 with mixed gases

Here, the preference and adsorption capacities of guest molecules in the sI and sII hydrate of water cages when CO2 + H2S, CO2 + SO2 and CO2 + N2O gas mixture form hydrates are simulated by using grand canonical Monte Carlo and molecular dynamics hybrid simulations method. The results indicate that SO2 prefers to occupy large cages, H2S prefers small cages for CO2 + H2S and CO2 + SO2 and N2O exhibits little preference between small or large or cages of CO2 + N2O sI hydrates, respectively. The abundance ratio shows hydrate can effectively achieve the separation of flue gases. Moreover, the thermodynamics calculation results show that the impurity gases H2S, SO2 and N2O favors the formation of CO2 hydrate. The stability CO2 + H2S, CO2 + SO2 and CO2 + N2O sI hydrates is higher compared to the stability of sII hydrates. The phase equilibrium analysis provides clear evidence that enclathration of H2S and SO2 molecules into the water cages of the hydrate structure plays a crucial role in stabilizing the hydrate lattices. The findings of this study suggest that removal of certain flue gas impurities is not required during the replacement of CH4 in hydrate form with the CO2 gas. The current investigation provides theoretical background for executing replacement of CH4 in hydrate form with the CO2 gas.

Hydrodynamic Response Analysis of a Fixed Aquaculture Platform with a Horizontal Cylindrical Cage in Combined Waves and Currents

Biofouling on net cages adversely affects structural safety and the growth of aquacultural fish. Therefore, a novel fixed aquaculture platform with a rotatable horizontal cylindrical cage is proposed in this study, which is convenient for the cleaning of biofouling. Based on ANSYS, the numerical model of the fixed aquaculture platform was established. The response results of the strain, acceleration, and displacement of the structure under the combined action of waves and currents at three typical attack angles were calculated. The effects of water depth and cage rotation on the hydrodynamic response of the structure are discussed. The results show that the strain, acceleration, and displacement of the cage increase with the increase in wave height; however, the change with the wave period is not obvious. The direction perpendicular to the long axis of the cage is the most unfavorable load direction. The acceleration of each position increases with the increase in water depth; however, the strain response has the opposite trend. When the rotation constraint of the horizontal cylindrical cage is released, the acceleration of the cage is larger than that when the cage is fixed. The rotation of the cage has a tiny effect on the structural strain and load acting on the structure.