Numerical Output Research Articles

Hazard consistent record selection procedures accounting for horizontal and vertical components of the ground motion: Application to liquid storage tanks

AbstractA methodology is proposed to enable state‐of‐the‐art record selection using ground motion components in all three principal loading directions. Relying on the well‐established Conditional Spectrum approach, its fundamental concepts are extended to ensure hazard consistency when the vertical ground motion component is considered along with the horizontal ones. To this end, different record selection techniques are employed, spanning sets of ground motion records with and without vertical motions, as well as with and without vertical ground motion hazard consistency. To demonstrate the effect that each record set can potentially have on a structure, an unanchored liquid storage tank is adopted as a case study, because of the vertical uplift motion it can exhibit, even under the application of horizontal loading only. A reduced‐order structural model is employed to generate the numerical output via multi‐stripe analysis, thus enabling the evaluation of the pertinent record selection approaches. Focusing on uplift and compressive meridional stress, response ratios and response hazard curves are extracted. It is shown that although the vertical ground motion component only mildly affects uplift, its effect on compressive meridional stress, on average, amplifies the response by a factor of 1.8 for moderate intensities and 2.8 for higher ones. Accounting for hazard consistency in the vertical component appears to be important for the case at hand, as it reveals notable discrepancies in the mean annual frequency of exceedance for the response parameters examined.

Preliminary validation of an innovative stress sensor for the Structural Health Monitoring of masonry buildings

Structural Health Monitoring (SHM) of existing masonry constructions is a challenging topic widely studied by the scientific community. In this paper, the use of a low-cost Capacitive Stress Sensors (CSSs) is investigated as an effective tool for the detection of the compression state level in mortar joints of masonry structures. The study is conducted by means of Finite Element (FE) simulations aimed at reproducing the mechanical response of a prototype of innovative CSS, recently patented, subjected to compression forces typical of masonry buildings under serviceability conditions. The constitutive behaviour of the sensor is validated against the results of a pilot laboratory test on a mortar cylindrical specimen endowed with CSSs and LVDTs and then subjected to cyclic uniaxial compression. The FE model is built in order to simulate the capacitive sensor embedded within the mortar material; therefore, a correlation analysis is performed by comparing the numerical stress-strain output of the sensor and the experimental results. The validation procedure shows that the numerical results are in good agreement with the records obtained by the LVDTs. Moreover, the FE model is used for developing a parametric analysis aimed at highlighting the effects of mortar stiffness and strength on the efficacy of the SHM performed by the CSSs and the optimal serviceability configurations are accordingly identified.

On the Deep Western Boundary Current Separation and Anticyclone Genesis off Northeast Brazil

AbstractThe Deep Western Boundary Current (DWBC) is the main component of the deep limb of the Atlantic Meridional Overturning Circulation (AMOC). Off northeast Brazil, the DWBC breaks up into southwestward‐propagating anticyclones. In this study, we investigate the breakup mechanism with hydrographic observations, eddy‐resolving numerical model outputs, and theory. Here, we present a quasi‐synoptic map of geostrophic velocities and stream function at the DWBC core level between 2.5°S and 11°S. We observe, in horizontal distributions of velocities, that the DWBC breakup site is linked to a topographic feature of the Brazilian continental margin centered at 8°S: the Pernambuco Plateau (PP). Moreover, both observations and model outputs hint at a possible DWBC separation near the PP preceding anticyclone genesis. We test, with three different theories from the literature, whether or not the DWBC separates at 8°S. The results of the tests converge to indicate that the DWBC undergoes a local and intermittent inertial separation while contouring the PP. Downstream of its separation at the plateau, the DWBC sheds eddies similarly to previously reported laboratory experiments. In addition, a regional analysis of energy transfer shows that barotropic instability significantly contributes to the anticyclones growth between 8°S and 13°S. Analysis of the energy budget and separation of waters related to the AMOC pathways into the basin interior provide a better understanding for later studies about heat fluxes and ventilation in the deep tropical South Atlantic.

Using Artificial Neural Networks to Couple Satellite C-Band Synthetic Aperture Radar Interferometry and Alpine3D Numerical Model for the Estimation of Snow Cover Extent, Height, and Density

This work presents a new approach for the estimation of snow extent, height and density in complex orography regions, which combines differential interferometric synthetic-aperture-radar (DInSAR) data and snowpack numerical model data through artificial neural networks (ANNs). The estimation method, subdivided into classification and estimation, is based on two artificial neural networks trained by a DInSAR response model coupled with Alpine3D snow cover numerical model outputs. Auxiliary satellite training data from satellite visible-infrared MODIS imager as well as digital elevation and land cover models are used to discriminate wet and dry snow areas. For snow cover classification the ANN-based estimation methodology is combined with fuzzy-logic and compared with a consolidated decision threshold approach using C-band SAR backscattering information. For snow height and density estimation, the proposed methodology is compared with an analytical inverse method and two model-based statistical techniques (linear regression and maximum likelihood). The validation is carried out in Central Apennines, a mountainous area in Italy with an extension of about 104 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and peaks up to 2912 m, using in situ data collected between December 2018 and February 2019. Results show that the ANN-based technique has a snow cover area classification accuracy of more than 80% when compared MODIS maps. Estimation bias and root mean square error are equal to about 0.5 cm and 20 cm for snow height and to 5 kg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and 80 kg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> for snow density. As expected, worse results are associated to low DInSAR coherence between two repeat passes and to snow melting periods.

SEMI-ANALYTICAL VIEW OF TIME-FRACTIONAL PDES WITH PROPORTIONAL DELAYS PERTAINING TO INDEX AND MITTAG-LEFFLER MEMORY INTERACTING WITH HYBRID TRANSFORMS

This paper focuses on the theoretical and computational investigation of the innovative nonlinear time-fractional PDEs incorporating the Caputo and Atangana–Baleanu fractional derivatives in the Caputo context using the [Formula: see text]-homotopy analysis transform method (HATM). The expected strategy employs a combination of [Formula: see text]-HATM and the Jafari transform with the assistance of Caputo and Atangana–Baleanu fractional derivative operators to obtain the methodology permits of PDEs with proportional delay. The fractional operators are employed in this research to demonstrate how crucial they are in generalizing frames involving singular and nonsingular kernels. The proposed series of solutions are closely in agreement with an exact solution. Several important challenges can be addressed to illustrate the validity of the proposed method. The outcomes of the proposed framework are displayed and assessed using numerical and graphical outputs. Furthermore, the results of our suggested strategy were compared to earlier outcomes. The proposed method requires less computation and has significantly better performance. Finally, the analysis shows that the enhanced technique is both reliable and meticulous when evaluating the impact of nonlinearities in science and technology.

Gdzie publikujesz, politologu? Wpływ reformy ewaluacji nauki w Polsce na międzynarodowy prestiż polskich nauk o polityce

The article aims to diagnose how Polish political science is internationally recognized, and how this recognition has changed during the last period of research evaluation (2017–2021). For this purpose, several quantitative indicators from the 2013–2016 and 2017–2021 evaluations were analyzed: the number of publications, place of publication, the impact of both the journal and the article. The hypotheses assume that in 2017–2021, the numerical output of Polish political science works indexed in international databases increased significantly. Still, when it comes to the impact of the Polish academy on global political science, it remains weak. The data provided in the SciVal program was used for the analysis. Articles were selected from the Scopus database, specifically from the “Politics &amp; International Studies” collection. The results of the conducted research confirm the assumptions formulated in the hypotheses.

NUMERICAL INVESTIGATIONS OF A SWIRLING TWO-PHASE AIR-WATER UPWARD FLOW IN STRAIGHT AND CONVERGENT VERTICAL PIPE

In this study, a numerical study is presented to analyze the flow parameters such as longitudinal and transverse velocities, hydrodynamic pressure, and volume fraction inside a vertical pipe. A vertical ascending swirl flow is established with the specified boundary conditions and compared between straight and convergent geometry pipes. Normalized film thickness is found to vary between 0.4 and 0.6, where the numerical output data from the present study resemble wire-mesh sensor data from literature. Convergent pipe flow includes the variation of hydrodynamic pressure thereby affecting the slug and bubble flow region. Longitudinal and transverse velocities are plotted against time and compared at the three inspection planes near the inlet, mid-portion, and outlet, respectively. In order to understand the effectiveness of rotational effect of gas and liquid phases, the vorticity components are studied. Parameters such as Q-criterion and vortex stretching term indicate the straining and shearing flow near the peripheral and core regions. The temporal volume fraction variation at the output section indicates the increase in the output liquid yield of convergent pipe outlet by 17&amp;#37;.

Computational Treatment of Magnetohydrodynamic Micropolar Fluid Flow Through Porous Medium Over an Exponentially Stretching Sheet with Heat Sink and Chemical Reaction Effects

The purpose of this research is to look into the magnetohydrodynamic boundary layer flow of Maxwell fluid across an exponentially stretching sheet with chemical reaction, and radiation impacts, that involves a heat sink. The PDE governing equation is converted to an ODE governing system. A Successive Linearization Method is then used to solve the system numerically. Graphically, the numerical outputs of, temperature, concentration profiles, and velocity are displayed. The results of several parameters are explored and examined. The numerical outcomes for the skin friction coefficient, local Nusselt number, Deborah number, local Sherwood number, and porosity are reported and analyzed. Based on the results, many characteristics have a considerable effect on fluid flow profiles. The reaction rate parameter had a significant impact on the concentration profile and the thickness of the boundary layer dropped as the reaction rate parameter was increased. The analyses’ findings were compared to those of previous studies and found to be in great agreement.

Free vibrations of all assemblies related to coupled hyperboloidal–cylindrical shells

For the first time, Natural Frequencies (NFs) associated with three groups of the coupling of a hyperboloidal (H) shell with a cylindrical (CY) shell, entitled Coupled Hyperboloidal–Cylindrical Shells (CHCSs), are discovered in this article. Correspondingly, General Three-Dimension Shell Theory (GTDST) is combined with the First-order Shear Deformation Theory (FSDT) to obtain the core relationships associated with the CHCSs. Followingly, the Governing Differential Motion Equations (GDMEs) referenced to the CHCSs are determined by employing Hamilton’s principle. Next, a well-arranged procedure branded the Generalized Differential Quadrature Method (GDQM) is considered to discretize the GDMEs, Boundary Equations (BEs), and Coupling Equations (CEs) associated with the CHCSs. Later, the NFs corresponding to the CHCSs are found by implementing the eigenvalue determination related to the discretized GDMEs. Because there is no examination regarding the NFs associated with these types of CHCSs in the literature, the outputs regarded in the present procedure are compared with the results related to the FEM-based process. It should be mentioned that the maximum error obtained is less than 0.4%. Based on this, the numerical outputs related to this examination can be employed as a benchmark for future investigations. Terminally, to consider the effect of all geometrical measures on the NFs corresponding to the CHCSs, several examples are developed.

PARAMETERS RATIONALIZATION OF THE THIN-WALLED ANCHORED RETAINING WALLS

One of the priority areas of theoretical research in the field of building structures is to reduce their own weight at a given resource - rationalization. There is a certain number of building structures in which the form and nature of the external load are interdependent. The most striking representative are the structures that perceive lateral pressure from bulk material - retaining walls. From the above review of modern scientific research aimed at finding rational parameters of retaining walls, it follows that the authors, as a rule, describe the cantilever retaining wall by a finite number of parameters and the reduction of its own weight or cost of the structure was taken as the target function. In this case, the load on the structure does not change. The idea underlying this work is that the structure of the retaining wall and the soil backfill, which holds it, is considered as a single system. In this system, the configuration of the structure determines the nature and magnitude of lateral pressure distribution. The sequence of actions to solve the problem of searching for a rational configuration of the structure leads to the division of the curved foam wall into a finite number of linear sections. The anchor support is represented in the form of an additional concentrated force applied at the anchor fixing point. In the work the dependences between the attributes of the stress-strain state of the structure and the system of angles of inclination of the sections are constructed. The configuration of the anchor and retaining wall, which will minimize the potential deformation energy of the system, is found within the framework of the BEA method. Using the numerical output data, the validity of the proposed method is demonstrated. The realization of calculations is reduced to the search for the extremum of the objective function of n variables where the potential deformation energy acts as a functionb and the combination of angles of inclination of the system's breakdown sections as variables. The solution of the problem is implemented by the conjugate gradient method. as a result of calculations, an image of the structure is obtained that minimizes the introduced criterion. Keywords: retaining walls, deformation energy, curved surfaces, rationalization.

Evaluation of low-level jets in the southern Baltic Sea: a comparison between ship-based lidar observational data and numerical models

Abstract. In contrast to fixed measuring devices, ship-based lidar systems provide highly reliable wind observations within extensive regions. Therefore, this kind of reference dataset provides a great potential for evaluating the performance of mesoscale numerical models in resembling mesoscale flow phenomena such as low-level jets – essential for an optimal development and operation of wind turbines. This paper presents a comparison between numerical output data from two state-of-the-art numerical datasets (ERA5 and NEWA) and the ship-mounted lidar measurements from the NEWA Ferry Lidar Experiment. The comparison was performed along the route covered by the vessel, as well as in specific locations within this route, to better understand the capabilities and limitations of the numerical models to precisely resemble the occurrence and main properties of low-level jets (LLJs) in different locations. The findings of this study show that the non-stationary nature of ship-based lidar measurements allows evaluating the accuracy of the models when retrieving jets' characteristics and occurrence under different temporal and spatial effects. Numerical models underestimate the occurrence of LLJs, and they struggle to accurately describe their main characteristics, with a particularly large underestimation of the falloff. The found results are to be seen in relation to the characteristics of the observations, such as the data availability, the time–position relation of the selected vessel's route, or the profile height limitation, as well as the features of the jets, with a particular relevance of core height and falloff. Additionally, the results illustrate the temporal and spatial shift between the LLJ events detected by the measurements and the models and the potential benefit of considering such deviations when studying LLJs' climatology through numerical modes.

The Suitability of UAV-Derived DSMs and the Impact of DEM Resolutions on Rockfall Numerical Simulations: A Case Study of the Bouanane Active Scarp, Tétouan, Northern Morocco

Rockfall simulations constitute the first step toward hazard assessments and can guide future rockfall prevention efforts. In this work, we assess the impact of digital elevation model (DEM) resolution on the accuracy of numerical rockfall simulation outputs. For this purpose, we compared the simulation output obtained using 1 m, 2 m and 3 m resolution UAV-derived DEMs, to two other models based on coarser topographic data (a 5 m resolution DEM obtained through interpolating elevation contours and the Shuttle Radar Topographic Mission 30m DEM). To generate the validation data, we conducted field surveys in order to map the real trajectories of three boulders that were detached during a rockfall event that occurred on 1 December 2018. Our findings suggest that the use of low to medium-resolution DEMs translated into large errors in the shape of the simulated trajectories as well as the computed runout distances, which appeared to be exaggerated by such models. The geometry of the runout area and the targets of the potential rockfall events also appeared to be different from those mapped on the field. This hindered the efficiency of any prevention or correction measures. On the other hand, the 1m UAV-derived model produced more accurate results relative to the field data. Therefore, it is accurate enough for rockfall simulations and hazard research applications. Although such remote sensing techniques may require additional expenses, our results suggest that the enhanced accuracy of the models is worth the investment.

A SPATIAL CAUSAL ANALYSIS OF WILDLAND FIRE-CONTRIBUTED PM2.5 USING NUMERICAL MODEL OUTPUT.

Wildland fire smoke contains hazardous levels of fine particulate matter (PM2.5), a pollutant shown to adversely effect health. Estimating fire attributable PM2.5 concentrations is key to quantifying the impact on air quality and subsequent health burden. This is a challenging problem since only total PM2.5 is measured at monitoring stations and both fire-attributable PM2.5 and PM2.5 from all other sources are correlated in space and time. We propose a framework for estimating fire-contributed PM2.5 and PM2.5 from all other sources using a novel causal inference framework and bias-adjusted chemical model representations of PM2.5 under counterfactual scenarios. The chemical model representation of PM2.5 for this analysis is simulated using Community Multiscale Air Quality Modeling System (CMAQ), run with and without fire emissions across the contiguous U.S. for the 2008-2012 wildfire seasons. The CMAQ output is calibrated with observations from monitoring sites for the same spatial domain and time period. We use a Bayesian model that accounts for spatial variation to estimate the effect of wildland fires on PM2.5 and state assumptions under which the estimate has a valid causal interpretation. Our results include estimates of the contributions of wildfire smoke to PM2.5 for the contiguous U.S. Additionally, we compute the health burden associated with the PM2.5 attributable to wildfire smoke.

A Modern Approach to a Stability-Based Definition of the Tropopause

Abstract Definition of the tropopause has remained a focus of atmospheric science since its discovery near the beginning of the twentieth century. Few universal definitions (those that can be reliably applied globally and to both common observations and numerical model output) exist and many definitions with unique limitations have been developed over the years. The most commonly used universal definition of the tropopause is the temperature lapse-rate definition established by the World Meteorological Organization (WMO) in 1957 (the LRT). Despite its widespread use, there are recurrent situations where the LRT definition fails to reliably identify the tropopause. Motivated by increased availability of coincident observations of stability and composition, this study seeks to reexamine the relationship between stability and composition change in the tropopause transition layer and identify areas for improvement in a stability-based definition of the tropopause. In particular, long-term (40+ years) balloon observations of temperature, ozone, and water vapor from six locations across the globe are used to identify covariability between several metrics of atmospheric stability and composition. We found that the vertical gradient of potential temperature is a superior stability metric to identify the greatest composition change in the tropopause transition layer, which we use to propose a new universally applicable potential temperature gradient tropopause (PTGT) definition. Application of the new definition to both observations and reanalysis output reveals that the PTGT largely agrees with the LRT, but more reliably identifies tropopause-level composition change when the two definitions differ greatly. Significance Statement In this study we provide a review of existing tropopause definitions (and their limitations) and investigate potential improvement in the definition of the tropopause using balloon-based observations of stability and atmospheric composition. This work is motivated by the need for correct identification of the tropopause to accurately assess upper-troposphere–lower-stratosphere processes, which in turn has far-reaching implications for our understanding of Earth’s radiation budget and climate. The result of this research is the creation of a new, universally applicable stability-based definition of the tropopause: the potential temperature gradient tropopause (PTGT).

The generation mechanism of cold eddies and the related heat flux exchanges in the upper ocean during two sequential tropical cyclones

The impacts of two sequential tropical cyclones (TCs), Kyarr and Maha, [from October 24 to November 06, 2019, over the Arabian Sea (AS)] on upper ocean environments were investigated using multiple satellite observations, Argo float profiles and numerical model outputs. To obtain a realistic TC strength, the Weather Research and Forecasting (WRF) model was used to reproduce Kyarr and Maha. During Kyarr and Maha, three distinct cold patches were observed at the sea surface with a maximum sea surface cooling of approximately 5°C. The comparison between WRF model simulation results and ERA5 wind field showed that the WRF model simulation indicated high simulation accuracy with respect to the SST decrease in the AS under the influence of Kyarr and Maha’s wind stress curls. Meanwhile, concentration of chlorophyll a (chl-a) and positive relative vorticity of sea surface also appeared in the three cold patch areas. Through the use of eddy detection algorithms, three mesoscale cold cyclonic eddies were identified along the track of TC Kyarr, and the locations of these cold eddies were highly correlated with three obvious negative sea surface height anomalies (SSHAs). The radii of the three cold eddies were 69 km, 50 km, and 41 km. With a focus on the thermodynamic responses of the three cold eddy fields to Kyarr and Maha, the central regions of the three cold eddies were explored. The central regions of the three cold eddies exhibited relatively shallow mixed-layer depths (MLDs) and low mixed-layer temperatures (MLTs). The depth integrated heat (DIH) content was also calculated to explore the heat flux exchanges occurring in different layers in the upper 200 m of the centre of each eddy. The results showed that DIH in each eddy centre varied by one order of magnitude, accounting for between 127.3 MJ m-2 and 1220.0 MJ m-2 of heat loss. This study suggests that the effect of long forcing time on intense positive wind stress curls can produce upwelling caused by Ekman response, which is the main influencing factor of the three cold eddies generation mechanism. At the same time, the positive relative vorticity injected into the sea surface also has some contribution. TC-induced vertical mixing and upwelling (strengthened by unstable structures inside the cold eddies) cause substantial redistribution of the DIH, and related heat flux exchanges at different layers occur in the eddy fields.

Development and Dynamics of Sediment Waves in a Complex Morphological and Tidal Dominant System: Southern Irish Sea

With the recent push for a transition towards a climate-resilient economy, the demand on marine resources is accelerating. For many economic exploits, a comprehensive understanding of environmental parameters underpinning seabed morphodynamics in tidally-dominated shelf seas, and the relationship between local and regional scale sediment transport regimes as an entire system, is imperative. In this paper, high-resolution, time-lapse bathymetry datasets, hydrodynamic numerical modelling outputs and various theoretical parameters are used to describe the morphological characteristics of sediment waves and their spatio-temporal evolution in a hydrodynamically and morphodynamically complex region of the Irish Sea. Analysis reveals sediment waves in a range of sizes (height = 0.1 to 25.7 m, and wavelength = 17 to 983 m), occurring in water depths of 8.2 to 83 mLAT, and migrating at a rate of 1.1 to 79 m/yr. Combined with numerical modelling outputs, a strong divergence of sediment transport pathways from the previously understood predominantly southward flow in the south Irish Sea is revealed, both at offshore sand banks and independent sediment wave assemblages. This evidence supports the presence of a semi-closed circulatory hydrodynamic and sediment transport system at Arklow Bank (an open-shelf linear sand bank). Contrastingly, the Lucifer–Blackwater Bank complex and associated sediment waves are heavily influenced by the interaction between a dominant southward flow and a residual headland eddy, which also exerts a strong influence on the adjacent banner bank. Furthermore, a new sediment transfer system is defined for offshore independent sediment wave assemblages, whereby each sediment wave field is supported by circulatory residual current cells originating from offshore sand banks. These new data and results improve knowledge of seabed morphodynamics in tidally-dominated shelf seas, which has direct implications for offshore renewable developments and long-term marine spatial planning.

Numerical Solutions on Reiner–Philippoff (RP) Fluid Model with Velocity and Thermal Slip Boundary Condition

Non-Newtonian fluid model was created against the Newton’s Law of viscosity where the viscosity is no more constant and dependent on the shear rate. The existing such fluid can be found in many industrial claims especially in food manufacturing, lubrication, biomedical flows and oil and gas. Besides, the used of non-Newtonian fluid occurs in mining industry where the slurries and muds are often handled. There are many models on non-Newtonian fluid available in literature where some of them capture the specific properties. The Reiner–Philippoff (RP) fluid model is considered in this endeavour due to the capabilities of the model which can be acted in three different family of fluid which are viscous, shear thickening and the shear-thinning. Mathematical model is constructed using continuity, momentum and energy equations where in form of partial differential equations (PDEs). The complexity of the proposed model is abridged by deduced the equations into ordinary differential equations (ODEs) by adopting similarity variables before the computation is done by bvp4c function drive in MATLAB software. To ratify the validity of the proposed model as well as numerical outputs, the comparative study is performed and it found to be in very strong agreement under limiting case where the present model is condensed to be identical with the reported model previously. The consequences of pertinent parameters on fluid’s characteristics are analyzed in details through the plotted graphic visuals and tabular form.

MATHEMATICAL AND COMPUTATIONAL INVESTIGATION OF THREE STRAIN DYNAMIC TRANSMISSION NETWORK MODEL OF THE ZOONOTIC COVID-19 EPIDEMIC

The COVID-19 epidemic, commonly known as the coronavirus flu epidemic, is a worldwide COVID-19 epidemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The new virus was discovered in December 2019 during an epidemic in Wuhan, China. In our suggested model, we have focused on the relationship between the reservoir, the mediator, and the individual during the transmission of the coronavirus. To better understand, how an infection spreads from a natural reservoir to a mediator and finally to a person, we have built a model that includes twelve ordinary differential equations with effective parameters. In this study, we have provided boundedness, non-negative solution, disease-free and endemic equilibrium point, stability analysis for the equilibrium points, sensitivity analysis, basic reproduction number, and numerical simulation. The epidemic indicator fundamental reproduction number is derived from the largest eigenvalue of the next-generation matrix. To establish the numerical output of the model, it was assessed if the new incidence of symptomatic and asymptomatic infections, deaths, and isolations under quarantined situations was larger than the existing incidence. A major goal of this study is to curtail COVID-19 from spreading through natural reservoirs to human via intermediate hosts.

The numerical re-creation of experimentally generated nonlinear irregular wave fields using a time-reversal approach

Physical model testing in irregular waves is often used to assess performance, and validate numerical models, of offshore structures and platforms, yet the full phase-resolved experimental conditions including reflections and correct nonlinearity are seldom replicated numerically. This results in uncertainty in numerical model validation, particularly when considering extremes. Herein we assess a time-reversal approach for the accurate numerical replication of experimentally generated wave fields. Fifteen irregular sea states, including steep and breaking cases, are generated in two large laboratories in the UK and replicated numerically using the time-domain nonlinear potential flow code OceanWave3D. Through statistical, temporal, and spatial analysis, the method is demonstrated to be effective at re-creating sea states with a wide range of steepness, bandwidth, and duration, in two very different laboratories. Typical values of the coefficient of determination between experimental and numerical surface elevations, r2, averaged over all measurement locations exceed 0.9 and are significantly larger than the alternative replication approaches assessed. The resulting numerical model outputs, when used as inputs to hydrodynamic models of offshore systems, will provide an improved level of validation, subsequently reducing uncertainty in both hydrodynamic model performance and platform design. The method is also naturally suited to replicating measured ocean data for conditions that can be approximately modelled as two-dimensional.

Simulating the Chesapeake Bay Breeze: Sensitivities to Water Surface Temperature

Abstract Simulations of Chesapeake Bay breezes are performed with varying water surface temperature (WST) datasets and formulations for the diurnal cycle of WST to determine whether more accurate depictions of water surface temperature improve prediction of bay breezes. The accuracy of simulations is measured against observed WST, inland wind speed and temperature, and in simulations’ ability to detect bay breezes via a detection algorithm developed for numerical model output. Missing WST data are found to be problematic within the Weather Research and Forecasting (WRF) Model framework, especially when activating the prognostic equation for skin temperature, sst_skin. This is alleviated when filling all missing WST values with skin temperature values within the initial and boundary conditions. Performance of bay-breeze prediction is shown to be somewhat associated with the resolution of the WST dataset. Further, model performance in simulating WST as well as in simulating the Chesapeake Bay breeze is improved when diurnal fluctuations of WST are considered via the sst skin option. Prior to running simulations, model performance in simulating the bay breeze can be accurately predicted through the use of a simple formulation.