Cage Deformation Research Articles

In situ measurements and simulations of a net cage in currents

Accurate predictions of net cages’ deformation under current loads are vitally important for the welfare of stocked fish and the safety of cage structures. In this study, a scaled cage model was deployed at a fish farm. The incoming flow profile was measured through an Acoustic Doppler Current Profiler (ADCP) with high resolution in the depth direction, and the flow inside the cage was measured through an Acoustic Doppler Vector (ADV). Pressure tags were applied to capture the lifting of the cage under varying current conditions. The incoming flow velocity shows a good correlation with the lifting of the cage, and in general the rate of the cage being lifted by the flow increases with flow speed. However, the flow speed measured inside the cage is much less correlated to the upstream flow and cage deformation. Numerical cage models consisting of truss elements were developed; two flow reduction factors r = 0.9 and 0.8 derived from empirical formulas and measurements inside cages in previous studies were applied. The numerical model with r = 0.8 can predict the cage deformation well, with most relative deviations in the depth directions being less than 15%. The study indicates the feasibility of applying pressure tags with high precision to estimate current-induced cage deformation in situ, especially when a cage is experiencing obvious deformation.

The impact of alcohol and ammonium fluoride on pressure-induced amorphization of cubic structure I clathrate hydrates.

We have investigated pressure-induced amorphization (PIA) of an alcohol clathrate hydrate (CH) of cubic structure type I (sI) in the presence of NH4F utilizing dilatometry and x-ray powder diffraction. PIA occurs at 0.98GPa at 77K, which is at a much lower pressure than for other CHs of the same structure type. The amorphized CH also shows remarkable resistance against crystallization upon decompression. While amorphized sI CHs could not be recovered previously at all, this is possible in the present case. By contrast to other CHs, the recovery of the amorphized CHs to ambient pressure does not even require a high-pressure annealing step, where recovery without any loss of amorphicity is possible at 120K and below. Furthermore, PIA is accessible upon compression at unusually high temperatures of up to 140K, where it reaches the highest degree of amorphicity. Molecular dynamics simulations confirm that polar alcoholic guests, as opposed to non-polar guests, induce cage deformation at lower pressure. The substitution of NH4F into the host-lattice stabilizes the collapsed state more than the crystalline state, thereby enhancing the collapse kinetics and lowering the pressure of collapse.

Numerical Simulation of Net Cage and an Alternative Method to Estimate the Remaining Volume

Abstract The deformation caused by waves and current in an aquatic environment significantly impacts the remaining volume of a net cage. Its fluctuations in magnitude could pose a potential threat to the well-being of cultivated species. There is a critical need for a simple, cost-effective solution to monitor cage deformation in real-time. This study proposes a depth-based method, utilizing just two depth meters attached to the cages floating collar and tube sinker, to estimate the remaining volume. Compared to the experimental measurements from previous studies, this method demonstrates satisfactory accuracies. Under current-only and waves-current conditions, the estimation differences are around 11.6% and 23%, respectively. In contrast, when compared to commonly used volume-based methods, the differences are approximately 1.8% and 9.5%. Despite a tendency for overestimation when the mean cross-sectional area deviates from the original top or bottom area of the cage, this method remains a feasible alternative. Its practicality highlights its potential as an efficient means of monitoring cage deformation.

CH3 CN@open-C60 : An Effective Inner-Space Modification and Isotope Effect Inside a Nano-Sized Flask.

Despite several small molecules being encapsulated inside cage-opened fullerene derivatives, such species have not considerably affected the structures and properties of the outer carbon cages. Herein, we achieved an effective inner-space modification for an open-cage C60 derivative by insertion of a neutral CH3 CN molecule into the cavity. The CH3 CN@open-C60 thus obtained showed an enhanced polarity, thus affording an easy separation from a mixture containing the empty cage by column chromatography on silica gel, without the preparative HPLC that was needed for previous cases. The less negative reduction potentials with respect to those of empty cage reflect the decreased energy level of the LUMO, which is supported by the DFT calculations. NMR spectroscopy, single-crystal X-ray analysis, and theoretical calculations revealed that both the presence of the encapsulated CH3 CN and cage deformation caused by the CH3 CN play an essential role in the change of the electronic properties. Furthermore, the favored binding affinity of deuterated acetonitrile CD3 CN with internal C60 surface is discussed.

Towards a holistic digital twin solution for real-time monitoring of aquaculture net cage systems

Digital twins and relevant concepts are being applied in a wide variety of ways, and they are of most use when an actual real-world physical system or process (a physical twin) is changing over time and when measurement data correlated with this change can be captured. In this work, a digital twin model was implemented for real-time monitoring of aquaculture net cage systems, which is notoriously challenging because of several difficult-to-measure properties, such as forces on and deformation of the flexible netting structures, waves and flow field alterations around the cage and complex stiffness behaviour of the mooring elements made by fibre ropes. These properties were set to be adaptable according to the resultant outputs, such as cage responses and mooring loads that were continuously compared with the measurement data obtained from remote monitoring sensors. In this way, real-time sensor data were assimilated into the numerical simulation model for representing the actual net cage system. No dedicated sensors were used for fish monitoring, but the fish behavioural responses to current, wave and cage deformation were modelled according to relevant field observational data. A wireless sensor network has also been tested for the digital twin implementation, which was found to be suitable for practical uses in fish farms.

A novel test rig for the investigation of roller–cage impacts of a needle roller bearing

Collisions between a roller and its cage result in crack initiation and propagation, leading to the fracture of the cage bridge. The impact forces applied to a needle roller-bearing cage bridge can change the cage’s strain distribution, which is related to the relative speed of the roller and cage. In this work, a needle roller-bearing roller–cage impact test rig was built to quantify cage strain and investigate the effects of speed on roller–cage impact forces. On the cage bridge, three crack sizes were machined and put on the needle roller-bearing roller–cage impact test rig. The strain was measured by a strain gauge positioned on the cage. An encoder measured the shaft speed. The effects of impact speed and crack size on roller–cage impact force and cage deformation were investigated.

Breast asymmetry classification and diagnostics

Breast asymmetry is a polyetiological condition, which may be caused by congenital characteristics, developmental abnormalities, hormonal changes, traumas or surgery. The estimation of breast symmetry should be performed by the plastic surgeon while planning the augmentation or reduction mammoplasty as well as reconstructive surgery. Breast asymmetry is a widespread condition, according to some reports, it can be found in more than half of women. Anthropometric methods, as well as radiology methods, are used to diagnose and estimate breast asymmetry. There are many classification systems of breast asymmetry. The first ones were based on breast appearance or etiology of asymmetry, while modern classifications combine morphologic and etiologic principles. Today there is no conventional diagnostic protocol for breast asymmetry, where it would be listed, which breast parameters should be measured during breast asymmetry estimation. The first attempts were made in the middle of the XX century. Works of Penn, Smith and Westreich are considered to be basic in this field. Generally, relationships between major breast soft-tissue reference points (nipple, areola, submammary fold, lateral border) and bone structures (breastbone, jugular notch, clavicle) are estimated.Mathematic formulas for counting breast volume depending on its linear measurements were developed as well. Nowadays the importance of skeleto-muscular system state (the presence of scoliosis or rib cage deformation) estimation is emphasized, while these conditions can also cause breast asymmetry.

Waves and currents decrease the available space in a salmon cage.

Due to increasing demand for salmon and environmental barriers preventing expansion in established sites, salmon farmers seek to move or expand their production to more exposed sites. In this study we investigate the effects of strong currents and waves on the behaviour of salmon and how they choose to use the space available to them. Observations are carried out in a site with strong tidal currents and well mixed water. Using video cameras and echo sounders, we show that salmon prefer to use the entire water column, narrowing their range only as a response to cage deformation, waves, or daylight. Conversely, salmon show strong horizontal preference, mostly occupying the portions of the cage exposed to currents. Additionally, waves cause salmon to disperse from the exposed side of the cage to the more sheltered side. Even when strong currents decrease the amount of available space, salmon choose to occupy the more exposed part of the cage. This indicates that at least with good water exchange, the high density caused by limited vertical space is not so aversive that salmon choose to move to less desirable areas of the cage. However, the dispersal throughout the entire available water column indicates that ensuring enough vertical space, even in strong currents, would be beneficial to salmon welfare.

Numerical Analysis toward the Effects of Fish Cage Deformation on Flow Field

Numerical Analysis toward the Effects of Fish Cage Deformation on Flow Field

RELIABILITY ANALYSIS OF ROLLING BALL BEARINGS CONSIDERING THE BEARING RADIAL CLEARANCE AND OPERATING TEMPERATURE

The aim of the research conducted in this particular paper was related to a comprehensive reliability analysis of SKF 626 Open Deep Groove ball bearings, conducted under controlled laboratory conditions. The experimental research consisted of: measurements of radial internal clearance (RIC) in ball bearings, measurement methods for the detection of bearing operating temperature and rolling element bearing wear, complete with the cage deformation of the the damaged bearing, the failure of which was revealed after the examination. The inspected SKF 6206 open deep groove ball bearings operating under laboratory conditions – simulated the model of dynamic behavior under real conditions by using the crankshaft of an air compressor. The results of research conducted based on the inspected samples of rolling bearings, showed that there was a significant dependence of the predictors of internal radial clearance on operating bearing temperature. Out of five test samples of rolling bearings, there was only one rolling ball bearing detected to be with failure after the bearing inspection. The examination of the damaged bearing revealed the final radial clearance value of 0.045 mm, i.e. operating temperature of 75 °C.

Vibration-based diagnostics of electrical engineering complexes motors over 40 kW

A vibration-based diagnostics method of large-power 1JAH5 (Siemens) DC motors over 660 kW used in paper machines is proposed in the article. When studying vibration spectrograms it was found that 8 Hz frequency shock loads considerably prevail over vibration, which corresponds to this motor rotor speed. The cause of vibration initiation generated by the motor rotor spinning was determined by theoretical methods. Vibration on the one hand appears as a result of bearings wear accompanied by bearing cage deformation and their shaft spinning axes reciprocal displacement, and on the other hand, by shaft eccentricity radii enhancement which causes dynamic loads increase affecting bearing units. The authors of the paper have come to the conclusion that in order to lower vibration of the motor it is necessary to replace the bearings with the new ones, the former due to a long-term service (over 30 years), vibration and shock load effects having exhausted their life span.

Model tests and full-scale sea trials for drag force and deformation of a marine aquaculture net cage

In this study, we investigated the hydrodynamic characteristics of marine aquaculture net cages used for farming silver salmon (Oncorhynchus kisutch). Two sets of experiments were conducted: model-scale testing, which was used to measure the drag force and deformation of a model net cage at different current velocities, and full-scale testing, which involved a sea trial at a silver salmon farm site. In the sea trial, an acoustic wave and current meter was deployed to record the current velocities around the net cage, and the cage deformation was estimated from the several vertical positions of net using 13 depth sensors. The precision of estimating the cage deformation using only the depth information was evaluated by comparing the estimated cage deformation with that determined from the images in model-scale testing. Comparing the model-scale and full-scale testing results showed that only the bottom netting was found to be deformed under lower water currents. The trends observed for the drag force, cage deformation, and cross-section area estimated from the depth data in full-scale testing were generally consistent with those converted from the model-scale testing using Tauti's similarity law. However, the drag force values of a full-scale net cage converted from the model-scale testing were higher than those estimated from the depth data in the full-scale testing. In contrast, the converted cross-sectional areas from model-scale testing were smaller than the estimated values in full-scale testing. In future, the cage deformation should be examined under higher current velocities, and the drag force should be measured in the full-scale testing to validate the results of the model-scale testing and the hydrodynamic model.

Cation Dynamics and Structural Stabilization in Formamidinium Lead Iodide Perovskites.

The vibrational dynamics of pure and methylammonium-doped formamidinium lead iodide perovskites (FAPbI3) has been investigated by high-resolution neutron spectroscopy. For the first time, we provide an exhaustive and accurate analysis of the cation vibrations and underlying local structure around the organic moiety in these materials using first-principles electronic-structure calculations validated by the neutron data. Inelastic neutron scattering experiments on FAPbI3 provide direct evidence of the formation of a low-temperature orientational glass, unveiling the physicochemical origin of phase metastability in the tetragonal structure. Further analysis of these data provides a suitable starting point to explore and understand the stabilization of the perovskite framework via doping with small amounts of organic cations. In particular, we find that the hydrogen-bonding interactions around the formamidinium cations are strengthened as a result of cage deformation. This synergistic effect across perovskite cages is accompanied by a concomitant weakening of the methylammonium interactions with the surrounding framework.

Biofouling Impacts and Toxicity of Antifouling Agents on Marine Environment: A Qualitative Study.

Biofouling from microorganisms, plants, barnacles, mussels or algae is a major problem for marine structures. Fouling leads to increased fuel costs due to increased frictional resistance on ships, and reduces reserve buoyancy of floating offshore structure, in addition to causing cage deformation and structural fatigue, impacting endurance of materials. The intrusion of invasive aquatic species (IAS) to new environments by ships is identified as a major threat to the world’s oceans. Marine fouling affects most manmade surfaces immersed in the sea, resulting in substantial losses. Anti-fouling paints tackle this problem to a certain extent. Extensive research is in progress in the antifouling technologies in maritime sector, with new products in compliance with International Maritime Organisation (IMO) regulations being developed. The most efficient solution to minimise fouling is to make surfaces unsuitable for settlers, coating them with Antifouling (AF) Paints containing toxic compounds. Most AF agents had Tributyltin (TBT), and has been phased out by IMO since 2008 due to harmful effect on environment. However, use of TBT in AF paints is not prohibited, though has been restricted in several countries. The environmental problems by biofouling and toxicity of existing and alternative Anti-Fouling techniques are reviewed in this paper. Further, various ship hull cleaning technologies commercially available including afloat cleaning are also introduced.
 Keywords— Biofouling, TBT, Antifouling (AF), IAS, IMO, AFS, Alternatives

Experimental investigation on the fluid–structure interaction of a flexible net cage used to farm Pacific bluefin tuna (Thunnus orientalis)

Resource protection of Pacific bluefin tuna (Thunnus orientalis) fish catching has become stringent over the past years. Meanwhile, tuna farming in Japan, the largest consumer of this fish, using a circular flexible net cage is continuously growing as a promising business. A stable aquaculture production of tuna can be achieved by understanding the characteristics, such as a clean environment and space in the net cage and flow inside and near the circular flexible net cage. We measured the drag force, cage deformation, and flow field inside and around a scaled net cage model composed of different bottom weights under various incoming current speeds in a flume tank. Results indicated that the drag force and cage volume increased and decreased, respectively, with the bottom weight. Owing to the significant deformation of the flexible net cage, a complex fluid–structure interaction occurred and a strong negative correlation between the drag force and cage volume was obtained. Furthermore, an area where the current speed was often reduced was identified. The intensity of this reduction depended on the incoming current speed. However, in particular cases, this reduction did not occur, or a local acceleration of the fluid was observed. In this work, the depth data of several positions on the net cage were also analyzed to verify if it could be used to estimate the cage volume. The findings of this study can be used to understand and design optimal flexible net cage structures, which can be used for modern aquaculture.

How caged salmon respond to waves depends on time of day and currents.

Disease, pest control, and environmental factors such as water quality and carrying capacity limit growth of salmon production in existing farm areas. One way to circumvent such problems is to move production into more exposed locations with greater water exchange. Farming in exposed locations is better for the environment, but may carry unforeseen costs for the fish in those farms. Currents may be too strong, and waves may be too large with a negative impact on growth and profit for farmers and on fish welfare. This study employed two major fish monitoring methods to determine the ability of Atlantic Salmon (Salmo salar) to cope with wavy conditions in exposed farms. Echosounders were used to determine vertical distribution and horizontal preference of fish during different wave and current conditions as well as times of day. Video cameras were used to monitor shoal cohesion, swimming effort, and fish prevalence in locations of interest. The results indicate complex interacting effects of wave parameters, currents, and time of day on fish behaviour and vertical distribution. During the day, hydrodynamic conditions had stronger effects on vertical distribution than during the night. In weak currents, fish generally moved further down in taller waves, but stronger currents generally caused fish to move upwards regardless of wave conditions. Long period waves had unpredictable effects on vertical distribution with fish sometimes seeking deeper water and other times moving up to shallower water. It is unclear how much the cage bottom restricted vertical distribution and whether movement upwards in the water columns was related to cage deformation. In extreme cases, waves can reach below the bottom of a salmon cage, preventing fish from moving below the waves and cage deformation could exacerbate this situation. Farmers ought to take into consideration the many interacting effects on salmon behaviour within a cage as well as the potential for cage deformation when they design their farms for highly exposed locations. This will ensure that salmon are able to cope when storms and strong currents hit at the same time.

Tide-induced changes in marine fish cage-shape cause changes in swimming behavior of cultured chub mackerel (Scomber japonicus)

We performed field measurements of the behavioral changes in cultured chub mackerel (Scomber japonicus) caused by tide-induced changes in the shapes of their small-sized tetragonal fish cages. The field measurements were conducted in two separate periods: neap tide, a period in which the shape of the fish cages was stable; and spring tide, a period in which the fish cages are significantly deformed, which was expected to have significant influences on fish behavior. In the spring tide, the cages were deformed greatly by the moving water, with different water velocities affecting the cages to different degrees; the volume loss was estimated at 4.9% and 7.3% for v = 0.114 m/s and v = 0.221 m/s, respectively. The fish exhibited significantly different behaviors between the neap tide and spring tide. During the neap tide, the fish remained in the lower part of the cage, but during the spring tide they made frequent upward and downward movements, and their horizontal distribution changed significantly due to the changes in the shape of the cage. The cage deformation during the spring tide greatly influenced the swimming behavior of fish.

Fluid-structure interaction analysis of a collapsible axial flow blood pump impeller and protective cage for Fontan patients.

Limited donor organs and alternative therapies have led to a growing interest in the use of blood pumps as a treatment strategy for patients with single functional ventricle. The present study examines the use of collapsible and flexible impeller, cage, and diffuser designs of an axial blood pump for Fontan patients. Using one-way fluid-structure interaction (FSI) studies, the impact of blade deformation on blood damage and pump performance was investigated for flexible impellers. We evaluated biocompatible materials, including Nitinol, Bionate 80A polyurethane, and silicone for flow rates between 2.0-4.0L/min and rotational speeds of 3000-9000rpm. The level of deformation experienced by a cage and diffuser made of surgical stainless steel (control), Nitinol, andBionate 80A polyurethane was also predicted using one-way FSI. The fluid pressure on the surface of the impeller, cage, and diffuser was determined using computational fluid dynamics (CFD), and then, the surface pressure was exported and used to investigate the impeller, cage, and diffuser deformation using finite element analysis. Finally, deformed impeller geometries were imported into the CFD software to determine the implication of deformation on pressure generation, blood damage index, and fluid streamlines. It was found that rotational speed, and not flow rate, is the largest determinant of impeller deformation, occurring at the blade trailing edges. The models predicted the maximum impeller deformation for Nitinol to be 40nm, Bionate 80A polyurethane to be 106μm, and silicone to be 2.8mm, all occurring at 9000rpm. The effects of silicone deformation on performance were significant, particularly at speeds above 5000rpm where a decrease in pressure generation of more than 10% was observed. Despite this loss, the pressure generation at 5000rpm exceeded the level required to alleviate Fontan complications. A blood damage estimation was performed and levels remained low. The effect of significant impeller deformation on blood damage was inconsistent and requires additional investigation. Cage and diffuser geometries made of steel and Nitinol deformed minimally but Bionate 80A experienced unacceptable levels of deformation, particularly in the free-flow case without a spinning impeller. These results support the continued evaluation of a flexible, pitch-adjusting, axial-flow, mechanical assist device as a clinical therapeutic option for patients with dysfunctional Fontan physiology.

Typical hydrodynamic models for aquaculture nets: A comparative study under pure current conditions

The net is regarded as the most critical component in marine aquaculture facilities as it is the only barrier which protects the environment from fish escapes. Accurate predictions of the net cage deformation and drag force on the nets are needed, both for ensuring fish welfare and for dimensioning of the mooring system. Thus, an appropriate hydrodynamic model is essential. In practice, two types of hydrodynamic force models, i.e., the Morison type and the Screen type, are commonly used to calculate the hydrodynamic forces on nets. Application of the models depends on the underlying structural model and the availability of data. A systematic review of hydrodynamic models is therefore undertaken to compare the models and various parameterisations, in aid of model selection during the design. In this study, eleven commonly used hydrodynamic models, i.e., five Morison models and six Screen models, are reviewed comprehensively, and implemented into a general finite element (FE) solver for dynamic simulations. Sensitivity studies on different current velocities, inflow angles and solidities of the nets are carried out. Moreover, different wake effects are also considered in numerical simulations. The numerical results from different models are compared against existing experimental data under pure current conditions. Suggestions for selection of suitable hydrodynamic models are provided, based on the model comparison.

Orthogonal superposition rheometry of model colloidal glasses with short-ranged attractions

Attractive colloidal glasses are unique as their dynamical arrest is a combination of entropic crowding effects and energetic bonds formation. When such systems are subjected to flow, their dynamics are activated in a way which differs from hard-sphere glasses that melt through a “convective cage release mechanism.” Here, we investigate the microscopic dynamics by measuring the relaxation spectrum during flow using orthogonal superposition rheometry. A small amplitude oscillatory strain is imposed perpendicularly to a steady shear flow, and superposition moduli are measured. Brownian dynamic simulations are utilized complementary to extract the moduli from mean-squared displacements using the generalized Stokes–Einstein relation. At low Péclet number, a crossover frequency between elastic and viscous moduli is detected, representing the relaxation time associated with shear-induced particles escape from their frustration (localization) under flow. For the repulsive glass, this is related to shear-induced cage renewal of particles. For attractive glasses, however, when particles escape their localized length (bonds), they move with no further hindrance with the escape time, which is independent of attraction strength and interestingly faster than that in the repulsive glass. This is attributed to particle localization at shorter length scales due to bonding. At high Péclet, a second low frequency crossover is observed and a low frequency elastic dominated response emerges. This elastic response may originate from slow relaxation of hydroclusters or be a consequence of more intricate nature of superposition moduli. At high frequencies, both orthogonal moduli increase relative to quiescent state due to shear-induced cage deformation, which slows down in-cage dynamics.