Changes In Water Depth Research Articles

Modeling Operations in System-Level Real-Time Control for Urban Flooding Reduction and Water Quality Improvement—An Open-Source Benchmarked Case

Advancements in smart sensing and control technologies enable urban drainage engineers to retrofit stormwater storage facilities with real-time control devices for mitigating stormwater in-site overflow, downstream flooding, and overloaded total suspended solids (TSS) in drainage pipes. While the smart technology can improve the performance of the static drainage systems, coordinatively controlling multiple valve and gate operations poses a significant challenge, especially at a large-scale watershed. Using a benchmark stormwater model located at Ann Arbor, Michigan, USA, we assessed the impact of different real-time control strategies (local individual downstream control and system-level multiple control) on balancing flooding mitigation at downstream outlets and TSS reduction at upstream storage units, such as detention ponds. We examined changes in peak water depth, outflow, and TSS as indicators to assess changes in water quantity and quality. The results indicate that system-level control can reduce peak water depth by up to 7.3%, reduce flood duration by up to 34%, and remove up to 67% of total suspended solids compared with a baseline uncontrolled system, with the outflow from upstream detention ponds being the most important hydraulic indicator for control strategy rule set-up. We find that system-level control does not always outperform the individual downstream controls, particularly in alleviating flooding duration at some downstream outlets. With urban growth and a changing climate, this research provides a foundation for quantifying the benefits of real-time control methods as an adaptive stormwater management solution that addresses both water quantity and quality challenges.

Reduction in wave shoaling over a linear transition bottom using a porous medium

Wave shoaling, which involves an increase in wave amplitude due to changes in water depth, can damage shorelines. To mitigate this damage, we propose using porous structures such as mangrove forests. In this study, we use a mathematical model to examine how mangroves, acting as a porous breakwater, can reduce wave shoaling amplitude. Shallow water equations are used as the governing equations and are modified to account for the presence of porous media. To measure the wave reduction generated by the porous media, the wave transmission coefficient is estimated using analytical and numerical approaches. The separation of variables method and the staggered finite volume method are utilized for each approach, respectively. The numerical results are then validated against the previously obtained analytical solutions. We then vary the friction and porosity parameters, influenced by the presence and extent of porous media, to evaluate their effectiveness in reducing wave shoaling.

Study on the Characteristics of Tidal Current Velocity in Estuarine and Bay Areas

Abstract In estuarine and bay regions, reciprocating tidal currents frequently constitute the predominant hydrodynamic forces. Nonetheless, there exists a paucity of research concerning the hydrodynamic characteristics under intricate tidal conditions. This study employs tidal current data collected from nine sites within the Yellow River Estuary and Hangzhou Bay to examine the periodic characteristics of tidal currents, the vertical velocity distribution, and the attributes of ebb and flood peak velocities. The study revealed that the Yellow River Estuary and Hangzhou Bay predominantly exhibit nearly symmetrical reciprocating tidal currents. Nevertheless, certain regions within Hangzhou Bay also demonstrate asymmetrical tidal currents. The vertical velocity distribution throughout various phases of a single tidal cycle generally adheres to the characteristics described by the SOULSBY distribution. The peak velocities of ebb and flood tides are correlated with the rate of change in water depth (hm/tm), and an equation for calculating these peak velocities has been derived through fitting data.

Flow measurement mechanism and hydraulic characteristics analysis of the airfoil weir-orifice facility in a rectangular channel

ABSTRACT Experimental studies and numerical simulations are conducted on the airfoil weir-orifice facilities to find a flow measurement and control device with a stable combined outflow form and good hydraulic performance. The orifice height under the weir is changed by adjusting the chord length and rotation angle of the weir. This paper uses three airfoil weir-orifice facilities for comparative study. The facilities have three flow forms under different rotation angles and flow conditions. Orifice discharge in combined outflow form is related to weir crest height but not upstream water depth. Flow formulas for three discharge forms are derived using dimensional analysis and incomplete self-similarity theory. The results show that the relative error of the formula is within ±6.34%. The Froude number is less than 0.4 under all working conditions; the critical submerged range is between 0.7 and 0.95; and under the premise of the unified weir crest height, the head loss decreases with the increased orifice height. The hydraulic jump location analysis yields the airfoil weir-orifice facility under the combined outflow as a submerged orifice outflow, and the hydraulic jump energy cancelation efficiency under the same flow condition is consistent with the upstream water depth change trend.

Numerical Investigation of Oblique Currents’ Effects on the Hydrodynamic Characteristics of Ships in Restricted Waters

The influence of oblique currents in narrow and shallow channels causes the fluid flow around ships to become complex. To analyze the hydrodynamic characteristics of a ship in such channels, it is essential to examine the influence of oblique currents on the ship’s hydrodynamic characteristics. In this study, current direction, ship speed, current speed, and water depth were identified as determinants affecting the hydrodynamic characteristics of a ship. Numerical simulations were conducted on a large oil tanker to investigate the effects of these factors on the ship’s hydrodynamic characteristics. The viscous fluid flow was modeled using the unsteady Reynolds-averaged Navier–Stokes (URANS) equations in conjunction with the k-ε turbulence model. The URANS equations were discretized using the finite volume method. The numerical results indicate substantial differences in the hydrodynamic characteristics of ships under oblique current conditions compared to still-water conditions. At a current direction of β = −45°, the direction of the sway force is consistent with that of still water’s sway force, which is an attractive force. The yaw moment at β = −45° changes from a bow-out moment under still-water conditions to a bow-in moment. Conversely, at a current direction of β = 45°, the sway force shifts from an attractive force under still-water conditions to a repulsive force. The yaw moment acts as a bow-out moment, which is consistent with that observed in still-water conditions. Furthermore, the influence of hydrodynamic characteristics on a ship varies significantly with changes in ship speed, current speed, and water depth. To ensure the safe navigation of ships, it is essential to develop and apply comprehensive strategies and countermeasures that account for practical conditions.

In-situ valve opening response of eastern oysters to estuarine conditions

High-frequency recordings of valve opening behavior (VOB) in bivalves are often used to detect changes in environmental conditions. However, generally a single variable such as temperature or the presence of toxicants in the water is the focus. A description of routine VOB under non-stressful conditions is also important for interpreting responses to environmental changes. Here we present the first detailed quantitative investigation of the in-situ VOB of eastern oysters (Crassostrea virginica) to environmental variables typically not considered stressful. The VOB of eight individuals was monitored for seven weeks in a Louisiana estuary. We examined the relationships between VOB metrics (variance in mean % max opening among oysters, the probability of an oyster being closed, and the rate of valve closure), and temperature, salinity, chlorophyll-a (chl-a) concentration, the rate of change in those environmental variables, and the rate of change in water depth. Relationships were analyzed through statistical models including rates of change over 0, 0.25, 1-, 6-, 12-, and 24-hours. All the responses were best explained by the 12-hour time step model. The interaction effect between salinity and the rate of change of salinity had the greatest impact on variance in oysters’ behavior. Oysters closed faster at higher salinities and were more likely to be closed at lower chl-a concentrations. Significant interactions were found between many environmental variables, indicating a high level of complexity of oyster behavior in the natural environment. This study contributes to a better understanding of the impact of environmental conditions on oyster behavior and can help inform predictive tools for restoration initiatives and fisheries practices.

Spatial heterogeneity in nutrient utilization during the end-Devonian ocean anoxic event: a case study of the Western Canada sedimentary basin

The Devonian-Carboniferous (D-C; 359 Ma) boundary is marked by widespread deposition of organic-matter-rich black shales associated with the Hangenberg mass extinction event. The Exshaw Formation spans the D-C boundary in the Western Canada Sedimentary Basin (WCSB) and includes the basal Exshaw Shale deposited under broadly anoxic waters. The sediments at the base of the Exshaw Shale were deposited synchronously during a transgressive event across the WCSB, spanning the geographic variability of the basin. The variable Corg content of the shale was affected by local nutrient upwelling and paleotectonic features impacting water depth and circulation. To characterize the link between paleogeography and nutrient cycling, geographic (N = 20 locations) and stratigraphic (N = 6 locations) trends of δ13Corg and δ15Nbulk were examined throughout the WCSB, representing a range of depositional settings. The δ15Nbulk values range between 0.0 and 6.3‰ and δ13Corg from −29.5 to −26.8‰. Phytoplankton production in focused upwelling zones acquired a relatively 15N-depleted signature through isotopic fractionation during nutrient assimilation, and the residual nutrient pool was 15N-enriched. The advection of surface waters away from the location of upwelling supported additional phytoplankton growth and the deposition of sediments with higher δ15N values. The stratigraphic sections include black laminated and burrowed mudrock sequences that record changes in paleoredox conditions, water depth, and tectonism over time. Up-core from the base of the Exshaw, the Corg content decreases and simultaneously δ15Nbulk increases, suggesting a decrease in eutrophic conditions. Variable δ13Corg and δ15Nbulk trends demonstrate that there is no “type” isotopic profile spanning the D-C boundary in the WCSB.

The regressive surface of marine erosion generated by tides: A case study from a Pleistocene tidal sand ridge sequence, Calabria, Southern Italy

AbstractThe regressive surface of marine erosion is a key stratigraphic discontinuity used to identify episodes of forced regression in marine strata. Typically, it marks the base of shallow‐marine (e.g. shoreface and deltaic) deposits eroding over relatively deeper‐water (e.g. shelf and prodelta) lithofacies. While well‐documented in marginal‐marine areas, its occurrence in offshore or strait settings dominated by tidal currents is less understood. This study investigates lower Pleistocene outcrops in the Plio‐Quaternary Siderno Basin, Calabria, southern Italy, where tidal sand ridges developed in a Mediterranean strait. High‐resolution drone images reveal a basinward‐dipping basal surface marking the onset of tidally dominated sedimentation. This discontinuity separates underlying shelf fines from overlying cross‐stratified, tidal bioclastic/siliciclastic arenites, indicating a prolonged period of marine regression in a strait setting. The stratal architecture of the ridges shows cross‐strata aggradation in up‐dip sections, transitioning down‐dip into balanced aggrading/prograding strata, and further basinward into markedly prograding deposits. These features are interpreted to reflect an initial phase of normal regression, evolving into forced regression. This latter stage is characterised by a progressive deepening of the basal discontinuity, causing more erosional effects on the underlying beds, with a vertical basinward fall of about 60 m over 2 km. Internal foreset geometry (two‐dimensional vs. three‐dimensional cross strata) and their vertical and lateral repetition indicate stages of equilibrium and disequilibrium for tidal bedforms, reflecting varying current speeds and water depth changes. The regressive surface of marine erosion here is formed by tidal currents, rather than waves, suggesting a new type of sequence stratigraphic discontinuity associated with tide‐dominated settings.

Climate change in the Canary/Iberia upwelling region: the role of ocean stratification and wind

The Canary/Iberia region (CIR), part of the Canary Current Upwelling System, is well-known for its coastal productivity and crucial role in enriching the oligotrophic open ocean through the offshore transport of the upwelled coastal waters. Given its significant ecological and socio-economic importance, it is essential to assess the impact of climate change on this area. Therefore, the goal of this study is to analyze the climate change signal over the CIR using a high-resolution regional climate system model driven by the Earth system model MPI-ESM-LR under RCP8.5 scenario. This modelling system presents a regional atmosphere model coupled to a global ocean model with enough horizontal resolution at CIR to examine the role of the upwelling favourable winds and the ocean stratification as key factors in the future changes. CIR exhibits significant latitudinal and seasonal variability in response to climate change under RCP8.5 scenario, where ocean stratification and wind patterns will play both complementary and competitive roles. Ocean stratification will increase from the Strait of Gibraltar to Cape Juby by the end of the century, weakening the coastal upwelling all year long. This increase in stratification is associated with a freshening of the surface layers of the North Atlantic. However, modifications in the wind pattern will play a primary role in upwelling source water depth changes in the southernmost region of the CIR in winter and in the north of the Iberian Peninsula in summer. Wind pattern changes are related to the intensification of the Azores High in winter and to a deepening of the Iberian thermal low in summer months.

A study of the temperature distribution in the OTEC cold water pipe using a heat and mass transfer approach

Abstract The difference between sea water temperature at a depth of around 1000 m and sea water temperature at sea level is generally used as a parameter in the design of Ocean Thermal Energy Conversion (OTEC). In practice, electricity generation is determined by the difference between the temperature of the cold seawater coming out of the Cold Water Pipe (CWP) and the temperature of the seawater at the surface. The temperature of cold sea water increases due to heat transfer experienced by cold sea water flowing through the CWP, which comes into contact with surrounding sea water which has a higher temperature. This in turn provides a lower actual temperature difference, and therefore reduces the design power capacity. However, many previous studies did not consider these lower temperature differences. This may be acceptable for cases with practically small heat transfer such as CWP with low thermal conductivity combined with good insulation used in 1000 m CWP vertical floating systems. Unfortunately, this may not be the case for many of OTEC’s proposed alternative sites, which are located on land systems that require CWP lengths of five km or more. This raises the need for careful investigation to determine the temperature of the sea water coming out of the CWP, where it is necessary to calculate the temperature distribution of the cold sea water flowing through the CWP. This paper aims to estimate the temperature distribution of cold sea water flowing through the CWP and the increase in temperature of cold sea water leaving the CWP. Analysis based on the principles of mass and heat transfer was carried out in this research, where modelling was carried out numerically using a finite volume approach. For the case considered, the change in sea water temperature at CWP from depth to the surface occurs 1-3°C, which is the accumulation of each change in sea water depth. The results of this research illustrate that designing an OTEC system with a long CWP must consider the temperature distribution of cold sea water flowing through the CWP to produce a more realistic design.

Deep learning-based fishing ground prediction for albacore and yellowfin tuna in the Western and Central Pacific Ocean

Tuna is a crucial economic fish species in the ocean, and the research on predicting the location of tuna fishing grounds has always been a key issue in deep-sea fisheries. Tuna, being a highly active fish that moves vertically in the ocean, is extremely sensitive to changes in marine environmental factors. This study aimed to investigate the impact of environmental factors and water depth changes on the accuracy of tuna fishing ground prediction. To achieve this, convolutional neural networks (CNNs) were utilized to train datasets using four key environmental factors - concentration of chlorophyll-a (CHLa), seawater temperature (ST), concentration of dissolved molecular oxygen (Oxy), and seawater salinity (SS) - at various depths ranging from 0 to 300 meters. A binary classification fishing ground prediction model for high and low yield areas of albacore and yellowfin tuna in the Western and Central Pacific Ocean was constructed. The goal was to identify the optimal fishing ground prediction model trained under these conditions and to explore the potential impact of environmental factors and water depth on the prediction accuracy of the model. The data used in this study included information from the Western and Central Pacific Ocean albacore and yellowfin tuna fisheries from 2003 to 2016, along with corresponding environmental data, which were used as the training and validation sets. The fishing data and environmental data from 2017 were then utilized as the test set to develop fishing ground prediction models for the two fish species. The results indicate that using convolutional neural networks to construct fishing ground prediction models is indeed feasible, and spatio-temporal information plays a significant role in optimizing predicting models for tuna fishing ground. Among the models developed for the same fish species using the four marine environmental factors at different depths, the model based on CHLa at each depth was found to be the most effective, while the model constructed using Oxy at the same depth performed the worst. Furthermore, the albacore fishing ground prediction model demonstrated significantly higher efficacy compared to the yellowfin tuna fishing ground prediction model when using the same marine environmental factors. It was also observed that the accuracy of fishing ground prediction models for the same species varied depending on water depth, even when based on the same marine environmental factors. These findings highlight the importance of considering both environmental factors and water depth in predicting tuna fishing grounds accurately.

Transient behavior of a plate partially immersed in the fluid subjected to impact loadings: Theoretical analysis and experimental measurements

This study aimed to investigate the transient behavior of a rectangular plate partially in contact with fluid subjected to a dynamic external force. To this purpose, a theoretical model was developed to analyze vibration characteristics and transient wave propagation. Based on superposition method, the dry mode shapes and natural frequencies of the plate under vacuum could be obtained. The dry mode shapes were treated as the fundamental function to construct the wet mode that describes the vibration behavior of the fluid-plate coupled system. The velocity potential and fluid pressure within a finite tank due to the plate deflection were derived using an equation governing the incompressible fluid. Based on the relationship between dry mode shape and wet mode shape, the fluid-plate coupled system's wet mode shape and resonant frequency could be determined from the frequency response function. Applying the normal mode method, the transient displacement of plate and fluid pressure can be obtained by solving a system of non-homogeneous differential equations. The theoretical predictions were verified by finite element method (FEM) and experimental measurements. Experiments were conducted using piezoelectric film sensors (polyvinylidene fluoride, PVDF) to measure the force history induced by a steel ball impact to quantitatively analyze the transient response. The comparison results proved that the theoretical predictions and experiments were in good agreement, including the transient responses of the displacement and in-plane strain of a plate partially submerged in the fluid. The results indicate that changes in water depth can induce resonance frequency shifts and wet mode shape distortions, which also illustrate that the vibrational properties of wet modes affect transient behavior. The proposed transient solution demonstrates an analytical approach that connects the physical significance of the dynamic behavior of the fluid-plate coupled system in time and frequency domains; it provides a connection between the transient behaviors and vibration characteristics.

Sediment resuspension and transport in the offshore subaqueous Yangtze Delta during winter storms

Storm-induced episodic sediment redistribution in coastal systems can reshape geomorphic bodies, disrupt ecosystems, and cause economic damage. However, cold-wave-storm-induced hydrodynamic changes and residual sediment transport in large, exposed subaqueous deltas, such as the Yangtze Delta, are poorly understood because it is typically expensive and difficult to obtain systematic field data in open coast settings during storm events. We conducted a successful field survey of waves, currents, changes in water depth, and turbidity at a station (time-averaged water depth of 20 m) in the offshore subaqueous Yangtze Delta over 10 days during winter, covering two storms and two fair-weather periods. During the storm events, strong northerly winds drove southward longshore currents (~0.2 m/s) and resulted in increased wave height and sediment resuspension, thereby leading to massive southward sediment transport. In contrast, both southward and northward transports were limited during the fair-weather periods. A better understanding of the storm-induced sediment transport can be obtained by using an approximately half-day lag in sediment transport behind wind force, given the time needed to form waves and longshore drift, the inertia of water motion, and the slow settling velocity of fine-grained sediment. Our results directly support previous findings of southward sediment transport from the Yangtze Delta during winter, which is deposited in the Zhejiang–Fujian mud belt in the inner shelf of the East China Sea. In addition, the southward sediment transport from the Yangtze Delta occurs mainly during episodic storm events, rather than during the winter monsoon, and winter storms dominate over typhoons in driving southward sediment transport from the delta. This study highlights the importance of storms, especially during winter storms, in coastal sediment redistribution, which is of particular significance when considering the projected increase in storm intensity with global warming.

Water depth affects submersed macrophyte more than herbivorous snail in mesotrophic lakes.

Water depth (WD) and snail abundance (SA) are two key factors affecting the growth of submersed aquatic plants in freshwater lake ecosystems. Changes in WD and SA drive changes in nutrients and other primary producers that may have direct or indirect effects on submersed plant growth, but which factor dominates the impact of both on aquatic plants has not been fully studied. To investigate the dominant factors that influence aquatic plant growth in plateau lakes, a one-year field study was conducted to study the growth of three dominant submersed macrophyte (i.e., Vallisneria natans, Potamogeton maackianus, and Potamogeton lucens) in Erhai Lake. The results show that, the biomass of the three dominant plants, P.maackianus, is the highest, followed by P.lucens, and V.natans is the lowest. Meanwhile, periphyton and snails attached to P.maackianus are also the highest. Furthermore, WD had a positive effect on the biomass of two submersed macrophyte species of canopy-type P.maackianus and P.lucens, while it had a negative effect on rosette-type V.natans. Snail directly inhibited periphyton attached on V.natans and thereby increasing the biomass of aquatic plants, but the effect of snails on the biomass of the other two aquatic plants is not through inhibition of periphyton attached to their plants. The dominant factors affecting the biomass of submersed macrophyte in Erhai Lake were determined, as well as the direct and indirect mechanisms of WD and snails on the biomass of dominant submersed macrophyte. Understanding the mechanisms that dominate aquatic plant change will have implications for lake management and restoration.

Response of Functional Traits of Aquatic Plants to Water Depth Changes under Short-Term Eutrophic Clear-Water Conditions: A Mesocosm Study.

Aquatic plants play a key role in the structuring and functioning of shallow lake ecosystems. However, eutrophication often triggers shifts in plant communities and species diversity, especially in the early stages when the water is still clear. Additionally, water depth is an important factor regulating aquatic plant communities. We conducted a 50-day mesocosm study to investigate how water depth (50 cm and 100 cm) affected the functional traits (vertical expansion versus horizontal colonisation) of 20 aquatic plants under eutrophic clear-water conditions. Among the selected species, the submerged plants Hydrocotyle vulgaris and Limnophila indica exhibited higher plant height or biomass in deeper water, while the emergent plants Myriophyllum aquaticum showed the opposite trend. Additionally, Ludwigia peploides subsp. stipulacea exhibited better vertical growth than the remaining species, and the submerged species Vallisneria denseserrulata had better horizontal colonisation. There was a positive correlation between plant height and rhizome length, indicating the absence of a trade-off between vertical growth and horizontal expansion. Our findings suggest an overall resilience of aquatic plants to varying water depths within our study range and highlight the importance of analysing functional traits when selecting appropriate species in freshwater ecosystem restoration, particularly in the face of climate change-induced water depth fluctuations.

Design, fabrication, and evaluation of a novel highly sensitive tuning fork pressure sensor for precise liquid level measurement

This article investigates the under-explored potential of utilizing a thin stainless-steel diaphragm coupled with a quartz tuning fork sensor for liquid depth measurements. The focus is on monitoring molten salt fluid levels in nuclear reactors and concentrated solar power systems. Addressing a literature gap, the research explores cantilever-type configurations of a double-ended quartz tuning fork resonator, with a no-load resonance frequency of 17.37 kHz, on thin stainless-steel diaphragms for fluid depth measurement at room temperature. As the fluid depth increases, hydro-static pressure acting on a 20 μm diaphragm causes deflection, bending a tuning fork. The resulting change in resonance frequency correlates with fluid depth. Experimental setups assess the tuning fork’s sensitivity to strain and bending, revealing strain sensitivity of 7.83 Hz/μ strain (450.78 ppm/μ strain) and bending sensitivity of 0.09 Hz/μm (5.18 ppm/μm). The pressure sensor assembly, tested in a water tank, exhibits a sensitivity of −0.28 Hz/mm (−16.12 ppm/mm) in a single cantilever-type configuration. Despite a limited linear range, it effectively measures water depth changes as small as 0.7 mm. Exploring a double cantilever-type configuration yields a sensitivity of 0.07 Hz/mm (4.03 ppm/mm) with a broader linear range. The article discusses the reasons for opposite sensitivity and highlights the advantages of each configuration. Beyond molten salt level monitoring, the technology’s applications may extend to fluid depth and pressure measurements in industrial and domestic settings.

Performance Assessment Of Two Active Absorption Systems In A Large Wave Flume

The quality of most coastal or ocean laboratory experiment depends on the accuracy, uniformity and stability of the generated waves. Generation of waves in the laboratory seems simple, but it should consider the spatio-temporal variability of the wave profile. As they propagate, waves interact with the boundaries, i.e. changes in water depth, lateral walls, test specimens, instrument supporting structures, passive absorbers, etc., as well as with varying hydrodynamic conditions (wave-induced currents, wave-wave interactions, or nonlinear energy transfer, among others). Reflected, scattered and radiated waves may propagate back to the wave generator and reflect back. Re-reflections from the wave generator may be a non-realistic representation of the intended wave field, to the extent that the total energy content in the testing facility may increase significantly and uncontrollably. Theoretically, for weakly nonlinear unidirectional waves propagating over a relatively small number of wavelengths, and as long as the still water depth and facility width does not change, the wave properties should remain constant in space and time, which can be identified as the uniformity and stability of the waves. Under these conditions, nonuniform or unsteady wave properties can be associated to an inadequate selection of the wave theory (Airy, Stokes n-order, Cnoidal, Stream Function, etc., e.g. Fenton 1999), the approximation of the wave generation technique (first or second order, nonlinear - see e.g. Mohtat et al., 2020), formation of wave instabilities (e.g. Benjamin-Feir, 1967), wave reflection, scattering or radiation, and the performance of the active wave absorption system. It can be said that the performance of the active wave absorption control system is one of the responsible factors that can affect directly the quality of the generated waves. Many laboratories have implemented different passive and active wave absorption systems, but the performance on the uniformity and stability of the generated waves, as well as the performance of the active wave absorption system used, have not been assessed in a systematic way, and related published data and information is quite scarce, with few interesting exceptions, e.g. (Lykke-Andersen, 2016; Spinneken 2010; Schäffer and Skourup 1996). However, a direct comparison among the different available active wave absorption control systems is still missing. This paper presents a thorough experimental study on the performance assessment of two different active wave absorption control systems (MTS and Awasys7) as a means to establish the quality of the experiment in terms of the uniformity (space) and stability (time) of generated wave parameters (descriptors) in the laboratory.

Distributed Optical Fibre Sensing for High Space‐Time Resolution Ocean Velocity Observations: A Case Study From a Macrotidal Channel

AbstractDespite significant recent technological advances, oceanographic observations on horizontal scales of meters to a few kilometres prove challenging. Exploiting legacy seafloor cables presents a disruptive prospect to address this gap, as it may provide low‐cost sustained observations with high space‐time resolution, enabled through novel opto‐electronic interrogation of optical fibers within the cables. Here, we demonstrate this approach in a renewable tidal energy cable embedded within a region with a strong barotropic tide. By making remote measurements continuously over 12 hr, we obtain the distributed differential strain experienced by 2 km of offshore cable from a diverse range of oceanic flow processes, with an along‐cable resolution of 2.04 m. We successfully identify: (a) nearshore wave breaking and its modulation by changes in water depth; (b) along‐cable tidal velocity, shown to be linearly related to the differential strain; and (c) high‐frequency motions consistent with 3‐dimensional turbulent processes, either of natural origin or from flow‐cable interaction. These inferences are supported by nearby conventional measurements of water depth and velocity.

Stability analysis of roadbed under flood scouring

Soil roadbed along the river suffers from water erosion at the bottom and collapse at the top under flood scouring, which leads to the suspension of upper pavement slab. In order to ensure the safety of soil roadbed along the river, this study explored the development mechanism of soil roadbed damage by flood in actual cases, and proposed the evolution process of instability under roadbed scouring. The stability law of roadbed along the river under flood scouring was analyzed, and the stability safety factor was corrected to analyze the sensitivity of water depth, flow rate, river bending angle and stability safety factor K in working conditions. The sensitivity of width and height of soil roadbed after flood scouring to water depth, flow velocity, river bending angle was investigated. Moreover, numerical simulation was carried out to determine the displacement nephogram and maximum shear stress nephogram of soil roadbed along the river under the conditions of road surface and roadbed load, vehicle loading or constant change of water depth. By comparing the above theories and engineering cases, the water damage mechanism of soil roadbed along the river was further verified.

Research on the Optimization of Multibeam Bathymetry Survey Line Layout Based on Simulated Annealing Algorithm

Multibeam bathymetry systems are widely used in water depth measurement, and their principle is based on the propagation characteristics of sound waves in water. The system has multiple advantages, such as high resolution, high accuracy, wide measurement range, automated mapping, and high efficiency. This study is based on the propagation characteristics of sound waves in water and utilizes a multibeam bathymetry system for water depth measurement, focusing on key issues such as coverage width, survey path, and seawater depth. Based on a two-dimensional plane model, the direction of the emitted beams from the measurement vessel and the relationship with seafloor slope angles are considered. The key parameter calculation model of the multibeam bathymetry system is established using the sine theorem and cosine theorem. To enhance the analysis accuracy, the calculation model is extended to three dimensions, incorporating more factors that have a significant impact on the measurement, such as the slope angle along the survey lines and changes in water depth. In practical applications, the survey lines are set to run in a north-south direction, and a greedy algorithm is used to ensure complete coverage of the measurements. Taking into account the complex seafloor topography, the fitted lines are used to represent the seafloor slopes. The multi-objective programming model is transformed into an unconstrained single-objective programming problem for further optimization. By solving the problem using simulated annealing algorithm, the optimized solution provides specific values for the spacing between adjacent survey lines, total track length, missed coverage rate of the surveyed area, and duplicate measurement coverage, enabling the optimal utilization of multibeam bathymetry systems in oceanic surveys.