Hydrodynamic Model Research Articles

How is cardiac output controlled in a Fontan circulation: an update.

After creating a Fontan circuit, control of the circulation is shifted from the upstream ventricle to the newly created Fontan portal system. This review aims to illustrate that the customary laws of biventricular cardiac output no longer apply and explain why standardized cardiac failure treatment regimens have little or no effect on a failing Fontan patient. A Fontan circulation is, in effect, a circulation in series regulated by the basic rules of any hydrodynamic circuit. A formula is developed that elucidates how flow through the critical bottleneck, and therefore, the whole circuit is controlled. The critical bottleneck in a hydrodynamic model is the prime determinant of flow and obscures other (less critical) bottlenecks. Once relieved, control of flow shifts to the next most significant bottleneck. The available options for improving flow in a hydrodynamic model are identical to those applicable to any dam: tackle the obstruction (the most impactful approach), push harder upstream (the easiest action), or pull/suck more downstream of the bottleneck (the least efficient strategy). In the early stages, the Fontan neo-portal circulation plays a pivotal role in the pathophysiology. The ventricle has little effect and only has an impact at a late stage. The Fontan formula in the present article stands as a valuable tool, aiding physicians in comprehending the pathophysiological and hydrodynamic intricacies of the Fontan circuit within the context of everyday clinical practice.

A hybrid data assimilation and machine learning approach for enhancing operational forecasting in 2D hydrodynamic models

ABSTRACT Data assimilation (DA) integrates observations to enhance model predictions, but its benefits can rapidly decay during forecast for models heavily influenced by boundary conditions. To extend forecast accuracy, we combine machine learning (ML) with DA in a hybrid approach. We utilize ML to create synthetic point observations, which are assimilated into the model and thus propagated to other positions and model variables. In a case study, we apply the approach to a tidal estuary hydrodynamic model using a long short-term memory (LSTM) network for ML forecasts and the Ensemble Kalman Filter (EnKF) for assimilation. Hereby, physical consistency and spatial representation of water levels in the estuary are maintained. Our results from 100 forecast runs show significant improvements: over 40% accuracy increase in forecasts up to 4 h ahead, and a >5% error reduction at 9 h compared with a traditional numerical model without assimilation.

An axial elastic deformation of ceramets on elastohydrodynamic lubrication of wavy-tilt-dam mechanical face seals

Purpose This paper aims to investigate the lubrication characteristics of siliconized graphite with a wavy-tilt-dam (WTD) pattern applied to the hydrodynamic face seals. Design/methodology/approach It focuses on two friction pairs, carbon graphite versus tungsten carbide (CG-TC) and siliconized graphite versus siliconized graphite (SG-SG), through a three-dimensional elastic hydrodynamic lubrication numerical model that integrates finite difference method and finite element method. The consequence of axial elastic deformation of sealing pair materials on film thickness, film pressure, cavitation and sealing performance for a WTD mechanical face seal under full working conditions of ΔP = 0.8, 5.3 and 15.8 MPa are analyzed theoretically. Findings The nuclear hydrodynamic WTD face seal generates a convergent gap and exhibits a dual-characteristic behavior of hydrodynamic and hydrostatic effects under various ΔP. Compared to the CG-TC, the SG-SG shows a lower minimum film thickness, decreasing by 3.9%, 17.3% and 35.1%. The flow leakage rate decreases by 47.8%, 52.1% and 75.4%. In addition, the film stiffness increases by 46.8%, 49.8% and 97.8%. Thus, the SG-SG better deals with the dynamic tracking problem, and the sealing performance is stable. The strength and hardness of siliconized graphite enhance WTD sealing performance and improve cavitation control in high-pressure applications. Originality/value The lubrication characteristics of the siliconized graphite with a WTD pattern could inform the future design of hydrodynamic shallow groove wavy seals in boiler feedwater engineering implements under high-pressure conditions for the nuclear power industry. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2024-0382/

Dynamic Response Simulation for a Novel Single-Point Mooring Gravity-Type Deep-Water Net Cage Under Irregular Wave and Current

This study investigated the structural response characteristics of a novel single-point mooring gravity-type deep-water (SPM-GDW) net cage under irregular waves and currents. A hydrodynamic numerical model of the cage was created and validated through model experiments. Based on the validated cage model, the structural response characteristics such as cage motion response, mooring line forces, and floating collar stress were studied, considering the actual operating conditions in the target sea area. The response time history curves, wave height time history, and spectral density statistics were studied and compared. The results showed that the heave motion of the cage was consistent with wave elevation in the vertical direction and mainly influenced by wave conditions. The surge motion of the cage was closely related to the current, with a significant lag effect compared to wave elevation motion. Low-frequency loads under the combined action of waves and currents had a significant impact on the surge motion of the cage. In addition, the mooring line tension and pontoon stress were closely related to the wave elevation, with peak values of tension and stress occurring almost simultaneously with the peak wave elevation. However, the pontoon stress exhibited high-frequency response characteristics while satisfying the wave frequency response trend. It was found that the flow velocity had a significant impact on the spectral density of mooring line tension and pontoon stress in the low-frequency range, with an increase in spectral density values as the flow velocity increased. The structural response characteristics identified in this study provide a computational basis for the optimized design and analysis of single-point mooring gravity-type deep-water cages.

Coupling HEC-RAS and AI for River Morphodynamics Assessment Under Changing Flow Regimes: Enhancing Disaster Preparedness for the Ottawa River

Despite significant advancements in flood forecasting using machine learning (ML) algorithms, recent events have revealed hydrological behaviors deviating from historical model development trends. The record-breaking 2019 flood in the Ottawa River basin, which exceeded the 100-year flood threshold, underscores the escalating impact of climate change on hydrological extremes. These unprecedented events highlight the limitations of traditional ML models, which rely heavily on historical data and often struggle to predict extreme floods that lack representation in past records. This calls for integrating more comprehensive datasets and innovative approaches to enhance model robustness and adaptability to changing climatic conditions. This study introduces the Next-Gen Group Method of Data Handling (Next-Gen GMDH), an innovative ML model leveraging second- and third-order polynomials to address the limitations of traditional ML models in predicting extreme flood events. Using HEC-RAS simulations, a synthetic dataset of river flow discharges was created, covering a wide range of potential future floods with return periods of up to 10,000 years, to enhance the accuracy and generalization of flood predictions under evolving climatic conditions. The Next-Gen GMDH addresses the complexity and limitations of standard GMDH by incorporating non-adjacent connections and optimizing intermediate layers, significantly reducing computational overhead while enhancing performance. The Gen GMDH demonstrated improved stability and tighter clustering of predictions, particularly for extreme flood scenarios. Testing results revealed exceptional predictive accuracy, with Mean Absolute Percentage Error (MAPE) values of 4.72% for channel width, 1.80% for channel depth, and 0.06% for water surface elevation. These results vastly outperformed the standard GMDH, which yielded MAPE values of 25.00%, 8.30%, and 0.11%, respectively. Additionally, computational complexity was reduced by approximately 40%, with a 33.88% decrease in the Akaike Information Criterion (AIC) for channel width and an impressive 581.82% improvement for channel depth. This methodology integrates hydrodynamic modeling with advanced ML, providing a robust framework for accurate flood prediction and adaptive floodplain management in a changing climate.

Effects of Climate Change on the Estimation of Extreme Sea Levels in the Ayeyarwady Sea of Myanmar by Monte Carlo

Comprehensive understanding and prediction of storm surge are vital for coastal hazard mitigation and prevention. To estimate extreme sea levels in the Ayeyarwady Sea of Myanmar, where long-term tidal data are unavailable, a hydrodynamic model capable of simulating storm surge, along with the Monte Carlo method for generating synthetic cyclones, was utilized. The effectiveness of this modeling approach in the Ayeyarwady seas was confirmed through validation against tidal levels and storm surges. After analyzing 17 selected historical cyclones, a synthetic cyclone history comprising 354 events was developed. Simulations driven by the generated cyclones were subsequently conducted. Based on the simulation results, the 50-year, 100-year, 200-year, and 1000-year sea levels at the research station were estimated to be 4.43 m, 4.83 m, 6.06 m, and 7.24 m, respectively. With a 10% intensification of cyclones and a sea level rise of 310 mm, these four vital parameters were predicted to be 5.03 m, 5.48 m, 6.95 m, and 8.43 m. The results of this study confirmed the significant effects of cyclone intensification and sea level rise. Moreover, the results provide valuable scientific insights for flood management and engineering design in the Ayeyarwady Sea of Myanmar.

Wind‐driven hydrodynamic and depositional patterns in shallow lakes: An exploratory modelling approach based on an archetypal case of Lake Hulun

ABSTRACTLake Hulun, the fifth‐largest lake in China, is a shallow lake (water depth <10 m) with typical wave‐dominated landforms developed around the shoreline, with a semi‐enclosed bay located in its southern corner. This novel study aims to understand wind‐driven hydrodynamics and its related depositional patterns in the data‐sparse Lake Hulun. To achieve this, a series of numerical simulations were conducted with a hydrodynamic and sediment transport model. The simulated hydrodynamic patterns are greatly influenced by wind direction shifts but are subject to little impact from wind speed changes which act mainly to accelerate flow. By varying the location and depth of the deepest part of the lake, this study reveals that the location of the depth centre has little impact on the overall hydrodynamic pattern of wind‐driven waterbodies. When the wind direction is perpendicular to the long‐axis shore, currents around the short‐axis shore flow in a direction that follows the wind direction. This study considers the wind‐induced longshore currents that are oblique to the long‐axis shore as the main driving force in transporting sediments along the shore and erosion of the shoreline. The formation of semi‐closed bays in both Lake Hulun, together with its nearby sister lake – Lake Buir – are attributed to the north‐west prevailing wind direction. Further exploratory simulations confirmed that prevailing winds tend to induce parallel distributed submerged sediment accumulations in the nearshore zone, challenging the notion of sediment accumulation solely in deep water zones. This study provides valuable insights into the hydro‐sedimentary dynamics in wind‐driven waterbodies, offering a process‐based perspective and contributing to current understanding of the palaeogeography of ancient lake systems.

Designing climate-resilient sustainable drainage system (SuDS) for mass rapid transit (MRT) development: A hydrodynamic modelling approach

The progressive industrialisation and urbanisation of urban areas have significantly altered hydrological factors such as terrain, imperviousness, and surface flow. These developments, accompanied by increased traffic congestion and carbon emissions, contribute to climate change. Consequently, implementing Mass Rapid Transit (MRT) systems is crucial for alleviating traffic congestion and reducing carbon emissions globally. However, the changes in urban hydrology following development, combined with increased rainfall due to climate change, exacerbate risks of flooding, erosion, and sedimentation for the MRT development and surrounding low-lying areas. Therefore, researching urban drainage systems under climate change conditions for MRT development is essential. This study utilised 1D/2D hydrodynamic modelling and simulation to investigate the performance of an existing MRT drainage system designed with a control-at-source concept and a new sustainable drainage system incorporating infiltration engineering and flow-retarding techniques, including porous layers and a bioecological system to mitigate urban flooding erosion and sedimentation. The results show that the new sustainable drainage system, featuring permeable pavements and bioretention facilities, effectively integrates 30% of the MRT-developed land typology without requiring additional land acquisition, which is cost-effective and practical for mitigating major flooding and reducing total suspended solids, thereby controlling erosion and sedimentation.

Temperature Dependence of Membrane Viscosity of Ternary Lipid GUV with Lo Domains.

In the cell membrane, it is considered that saturated lipids and cholesterol organize liquid-ordered (Lo) domains in a sea of liquid-disordered (Ld) phase, and proteins relevant to cellular functions are localized in the Lo domains. Since the diffusion of transmembrane proteins is regulated by the membrane viscosity, we investigate the temperature dependence of the membrane viscosity of the ternary GUV composed of the saturated lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), the unsaturated lipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol (CHOL) to understand the effect of the phase separation on the membrane viscosity using microinjection technique. In the microinjection method, membrane viscosity is estimated by comparing the flow pattern induced on a spherical membrane with a hydrodynamic model. For phase-separated GUVs, the flow pattern is visualized by the motion of the domains. In this study, we developed a method to visualize the flow patterns of homogeneous GUVs above the phase separation temperature by using beads attached to the GUVs. We succeed to measure the membrane viscosity of ternary GUVs both above phase separation temperature and in the phase-separated region and find that the membrane viscosity decreases dramatically by the phase separation. In the phase-separated region, i.e., GUV with Lo domains, the membrane viscosity is determined by that of the Ld phase, ηLd, and show weak temperature dependence compared with that of the DOPC single component GUV, which is a main component of the Ld phase. We revealed that the Moelwyn-Hughest (MH) model which takes into account the effects of the membrane composition, viscosity of pure component and interaction between components well describes the obtained membrane viscosity of the ternary GUV both above phase separation temperature and in the phase-separated region. The drastic decrease of the membrane viscosity by the phase separation plays an important role in regulating the mobility of constituents in multi-component membranes.

A coupled two-dimensional–three-dimensional hydrodynamic model for simulating flood wave evolution in reservoirs and riverbeds

The geometric scale of real reservoirs is immense, and their boundaries are intricate. Consequently, two-dimensional numerical simulations of the entire reservoir cannot accurately capture the three-dimensional flow characteristics in localized regions. Conversely, comprehensive three-dimensional simulations are often unfeasible due to the substantial computational resources they demand. This paper proposes a two-dimensional-three-dimensional coupled hydrodynamic model by combining a two-dimensional shallow water model and a three-dimensional free surface model based on the Lattice Boltzmann Method. The model introduces algorithms that establish unified requirements for computational parameters, ensure the conservation of physical quantities at the interface, and facilitate the inversion of two-dimensional data to three-dimensional formats, as well as the integration of three-dimensional data into two-dimensional formats. The model was applied to meticulously simulate the evolution of flood waves resulting from dam breaches over uneven riverbeds. Through theoretical analysis and experimental comparisons, a detailed examination of the conservation and coherence of physical quantities at the interface was conducted, thereby validating the accuracy of the proposed approach. Finally, the large-scale evolution of wave surges in a riverbed hydropower station reservoir was simulated, effectively demonstrating the capability to address practical hydrodynamic challenges. Additionally, the discussion highlights the computational savings achieved by this model relative to conventional three-dimensional simulations, establishing a foundation for its application in real-world engineering cases.

A coupled and parallel peridynamics–SPH modeling and simulation of buried explosion induced soil fragmentation and cratering

In this work, we develop a coupled peridynamics (PD) and smoothed particle hydrodynamics (SPH) model for simulating soil fragmentation, ejection, and cratering under buried explosions. Specifically, the non-ordinary state-based PD theory describes the dynamic response of soil, while the SPH method governs the motion of the explosive gas products. A stable and efficient coupling algorithm for data transfer between PD and SPH is adopted. To accurately capture soil behaviors under blast loading, we propose a modified Drucker–Prager plasticity model incorporating an additional high-pressure compaction equation of state (EoS). Additionally, a parallel code using the OpenMP algorithm is developed for the coupled PD–SPH model to handle large-scale, long-duration soil explosions. PD–SPH predictions are compared with two sets of well-designed centrifugal model tests. The gravitational effect is considered in the simulation to replicate the true physical process of buried explosions in soil. It is found that the coupled PD–SPH model successfully captures the entire physical process of soil fragmentation, ejection, and cratering induced by buried explosions. The predicted soil ejection and cratering morphologies, as well as quantitative results such as ejection speed, ejection height, and crater diameter, align well with the test results. Furthermore, the results indicate that the gravitational effect significantly influences the soil ejection and cratering processes. With increased gravitational acceleration, the soil ejection height and crater size decrease markedly.

Multi-scale influences on Escherichia coli concentrations in shellfish: From catchment to estuary.

Sustainability of bivalve shellfish farming relies on clean coastal waters, however, high levels of faecal indicator organisms (FIOs, e.g. Escherichia coli) in shellfish results in temporary closure of shellfish harvesting beds to protect human health, but with economic consequences for the shellfish industry. Active Management Systems which can predict FIO contamination may help reduce shellfishery closures. This study evaluated predictors of E. coli concentrations in two shellfish species, the blue mussel (Mytilus edulis) and the Pacific oyster (Crassostrea gigas), at different spatial and temporal scales, within 12 estuaries in England and Wales. We aimed to: (i) identify consistent catchment-scale or within-estuary predictors of elevated E. coli levels in shellfish, (ii) evaluate whether high river flows associated with rainfall events were a significant predictor of shellfish E. coli concentrations, and the time lag between these events and E. coli accumulation, and (iii) whether operation of Combined Sewer Overflows (CSO) is associated with higher E. coli concentrations in shellfish. A cross-catchment analysis gave a good predictive model for contamination management (R2=0.514), with positive relationships between E. coli concentrations and river flow (p=0.001), turbidity (p=0.002) and nitrate (p=0.042). No effect was observed for catchment area, the number of point source discharges, or agricultural land use type. 64% of all shellfish beds showed a significant relationship between E. coli and river flow, with typical lag-times of 1-3 days. Detailed analysis of the Conwy estuary indicated that E. coli counts were consistently higher when the CSO had been active the previous week. In conclusion, we demonstrate that real-time river flow and water quality data may be used to predict potential risk of E. coli contamination in shellfish at the catchment level, however, further refinement (coupling to fine-scale hydrodynamic models) is needed to make accurate predictions for individual shellfish beds within estuaries.

Modelled Water Temperature Patterns and Energy Balance of a Threatened Coastal Lagoon Ecosystem

ABSTRACTCoastal water temperatures control physical, chemical, and biological processes and are expected to rise due to future changes in freshwater temperature and flow rates, heat exchange with the warming atmosphere, and thermal interactions with a changing ocean. However, the thermal sensitivity of transitional, coastal water bodies to climate change remains poorly understood, due partly to a lack of knowledge on present‐day thermal controls in these settings. Accordingly, we applied a coastal hydrodynamic model (MIKE 3 FM), with a coupled thermal module to simulate hydrodynamics and water temperature variability in the Basin Head lagoon, a federally protected coastal ecosystem in the Canadian province of Prince Edward Island. Field data from the lagoon were used to calibrate and assess the numerical model, while atmospheric, oceanic, and hydrologic data were used to form the thermal and hydrodynamic boundary conditions. The model successfully reproduced tidal water level oscillations as well as diurnal and semi‐diurnal (tidal) temperature fluctuations. Model results show longitudinal, cross‐shore, and vertical thermal variability within the lagoon, including pronounced thermal variability near the bed and near the inlet due to tidal pumping. Model results and field data highlight the thermal sensitivity of the lagoon during heat waves; however, distinct cold‐water plumes at freshwater inputs (springs and groundwater‐dominated streams) persisted, with temporally averaged temperatures in these zones up to 18 °C colder than the ambient lagoon. Although, these freshwater inflows can dominate local energy budgets, the surface heat fluxes, especially shortwave radiation, exert the dominant control on the lagoon‐wide energy budget. Collectively, the model findings emphasise the interacting effects of atmospheric, hydrologic, and oceanic forcing on the spatiotemporal patterns of water temperatures in this threatened coastal ecosystem.

Quantify the Compound Effects caused by the interactions between inland river system and coastal processes in Hurricane Coastal Flooding through Controlled Hydrodynamic Modeling Experiments

Quantify the Compound Effects caused by the interactions between inland river system and coastal processes in Hurricane Coastal Flooding through Controlled Hydrodynamic Modeling Experiments

Enhancing overall performances of large constructed wetlands using an integrated approach of numerical simulation and response surface method--Taking Bagong hybrid CWs as an example.

Constructed wetlands (CWs) with low carbon properties represented an effective approach for treating low-polluted water and improving water quality. Here, a research scheme was proposed to achieve maximum operation benefits of the large-scale CWs through parameter identification, operation simulation, evaluation, and analysis of the water quality process. Based on the two-dimensional water hydrodynamic model coupling with the Eco-Lab water quality module (with nutrients), simulation for Bagong hybrid CWs was successfully conducted. Variables were estimated using response surface design (RSD), and the values of model parameters were calibrated in accordance with central combination design (CCD) experiments. Ten key parameters in the water quality process affecting the overall pollutant removal of CWs were identified, and the water quality model of the CWs could be replicated well with the actual situation within the 95% confidence interval. The water purification effect of the CWs under five different influent flow conditions was simulated, and the maximum hydraulic loading (0.036m3·(m-2·h-1)) of the CWs was determined with the effluent water quality to meet the design requirements. The integrated method could effectively enhance the efficiency of parameter calibration and significantly reduce the simulation workload. The results of pollutants migration and transformation under different influent conditions could provide a universally applicable and valid method in engineering applications, and process a promising application prospect.

SN 2018is: A low-luminosity Type IIP supernova with narrow hydrogen emission lines at early phases

We present a comprehensive photometric and spectroscopic study of the Type IIP supernova (SN) 2018is. The V band luminosity and the expansion velocity at 50 days post-explosion are -15.1±0.2 mag (corrected for A_V=1.34 mag) and 1400 km s^-1, classifying it as a low-luminosity SN II. The recombination phase in the V band is shorter, lasting around 110 days, and exhibits a steeper decline (1.0 mag per 100 days) compared to most other low-luminosity SNe II. Additionally, the optical and near-infrared spectra display hydrogen emission lines that are strikingly narrow, even for this class. The Fe ii and Sc ii line velocities are at the lower end of the typical range for low-luminosity SNe II. Semi-analytical modelling of the bolometric light curve suggests an ejecta mass of ∼8 M_⊙, corresponding to a pre-supernova mass of ∼9.5 M_⊙, and an explosion energy of ∼0.40 times 10^51 erg. Hydrodynamical modelling further indicates that the progenitor had a zero-age main sequence mass of 9 M_⊙, coupled with a low explosion energy of 0.19 times 10^51 erg. The nebular spectrum reveals weak O i λλ6300,6364 lines, consistent with a moderate-mass progenitor, while features typical of Fe core-collapse events, such as He i C i and Fe i are indiscernible. However, the redder colours and low ratio of Ni to Fe abundance do not support an electron-capture scenario either. As a low-luminosity SN II with an atypically steep decline during the photospheric phase and remarkably narrow emission lines, SN 2018is contributes to the diversity observed within this population.

Innovations in Wave Energy: A Case Study of TALOS-WEC’s Multi-Axis Technology

The technologically advanced learning ocean system—wave energy converter (TALOS-WEC) project addresses the urgent need for sustainable and efficient energy solutions by leveraging the vast potential of wave energy. This project presents a pioneering approach to wave energy capture through its unique multi-axis and omnidirectional point absorber design. Featuring a fully enclosed power take-off (PTO) system, the TALOS-WEC harnesses energy across six degrees of freedom (DoFs) using an innovative internal reaction mass (IRM) mechanism. This configuration enables efficient energy extraction from the relative motion between the IRM and the hull, aiming for energy conversion efficiencies ranging between 75–80% under optimal conditions, while ensuring enhanced durability in harsh marine environments. The system’s adaptability is reflected in its versatile geometric configurations, including triangular, octagonal, and circular designs, customised for diverse marine conditions. Developed at Lancaster University, UK, and supported by international collaborations, the TALOS-WEC project emphasises cutting-edge advancements in hydrodynamic modelling, geometric optimisation, and control systems. Computational methodologies leverage hybrid frequency-time domain models and advanced panel codes (WAMIT, HAMS, and NEMOH) to address non-linearities in the PTO system, ensuring precise simulations and optimal performance. Structured work packages (WPs) guide the project, addressing critical aspects such as energy capture optimisation, reliability enhancement, and cost-effectiveness through innovative monitoring and control strategies. This paper provides a comprehensive overview of the TALOS-WEC, detailing its conceptual design, development, and validation. Findings demonstrate TALOS’s potential to achieve scalable, efficient, and robust wave energy conversion, contributing to the broader advancement of renewable energy technologies. The results underscore the TALOS-WEC’s role as a cutting-edge solution for harnessing oceanic energy resources, offering perspectives into its commercial viability and future scalability.

Analysis and improvement of human stability in floodwaters through numerical simulation with SPH-DEM model

This study improves the formulae for determining the incipient velocity of sliding and toppling instability through force analysis. It introduces a self-adjusting posture parameter to make the approach applicable to actual human subjects. In addition, a novel concept of critical water depth is proposed to classify the type of instability. The smoothed particle hydrodynamics model, coupled with the discrete element method, is employed to simulate the instability scenarios of human bodies. Through the validated fluid–structure interaction model, the influence of critical factors on human stability is investigated, including the friction coefficient, height, mass, and body postures. The developed formulae are corroborated with experimental data about actual human subjects. The incipient velocity formula for toppling instability in a bending posture is introduced, previously overlooked in the literature. The results contribute new insights into the instability criterion for individuals in floodwaters and offer additional strategies to enhance human stability.

Mixed Layer Depth Measurement in Coastal Waters Utilizing Atmospheric Muons

Abstract Mixed Layer (ML) in Oceans are defined as the less dense upper region of the water column where turbulent mixing occurs and water exhibits almost uniform density profile. Mixed Layer Depth (MLD) is the depth of this region and shows diurnal and seasonal fluctuations as well as spatial variations in different regions of water. The determination of MLD is an important indicator for climate change in bodies of water and the novel method proposed here would allow for a continuous monitoring of MLD. Atmospheric muon count is proportional to the density of water which can be measured by counting muons at the bottom and comparing with a shore based or buoy based muon counter. Combining this measurement with Sea Surface Temperature (SST) and Sea Surface Salinity (SSS) data from earth observing satellites, daily mean MLD can be estimated with an accuracy of 3% for down to 60m depth. In order to determine MLD from muon count difference between surface and bottom detectors, a new method was introduced to calculate MLD using average density of water column. A Geant4 model made to show the validity and limitations of the method. Unlike open ocean, the system can measure MLD in shallow coastal waters where muon count at the bottom is enough for daily based measurements. The proposed method can provide continuous in situ measurement of MLD in coastal shallow waters and this data can be used to provide boundary conditions for hydrodynamic and ecosystem models.

Study of Hydrologic Connectivity and Tidal Influence on Water Flow Within Louisiana Coastal Wetlands Using Rapid-Repeat Interferometric Synthetic Aperture Radar

The exchange of water, sediment, and nutrients in wetlands occurs through a complex network of channels and overbank flow. Although optical sensors can map channels at high resolution, they fail to identify narrow intermittent channels colonized by vegetation. Here we demonstrate an innovative application of rapid-repeat interferometric synthetic aperture radar (InSAR) to study hydrologic connectivity and tidal influences in Louisiana’s coastal wetlands, which can provide valuable insights into water flow dynamics, particularly in vegetation-covered and narrow channels where traditional optical methods struggle. Data used were from the airborne UAVSAR L-band sensor acquired for the Delta-X mission. We applied interferometric techniques to rapid-repeat (~30 min) SAR imagery of the southern Atchafalaya basin acquired during two flights encompassing rising-to-high tides and ebbing-to-low tides. InSAR coherence is used to identify and differentiate permanent open water channels from intermittent channels in which flow occurs underneath the vegetation canopy. The channel networks at rising and ebbing tides show significant differences in the extent of flow, with vegetation-filled small channels more clearly identified at rising-to-high tide. The InSAR phase change is used to identify locations on channel banks where overbank flow occurs, which is a critical component for modeling wetland hydrodynamics. This is the first study to use rapid-repeat InSAR to monitor tidal impacts on water flow dynamics in wetlands. The results show that the InSAR method outperforms traditional optical remote sensing methods in monitoring water flow in vegetation-covered wetlands, providing high-resolution data to support hydrodynamic models and critical support for wetland protection and management.