Numerical Domains Research Articles

Evaluation of drag coefficients under medicane conditions: Coupling waves, sea spray and surface friction

This work represents an initial step toward the coupled ocean-atmosphere-aerosols modeling of severe storms in the Mediterranean basin. This is realized extending the classical Charnock formulation of surface roughness over sea and consequently the determination of air-sea momentum fluxes in numerical models. To improve the forecast of severe Mediterranean storm systems, like the so-called Medicanes, it is essential to consider the wave-state and sea spray effects on the sea surface roughness explicitly. This is implemented in the present work by coupling the third-generation WAVEWATCH III model (WWIII) and the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) model configured with the Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) aerosol package. The communication between the two models is realized through an offline coupling scheme, which utilizes a regridding algorithm between the numerical domains of the two models. In this context, the wave peak frequency is passed from WWIII to WRF-Chem model permitting the calculation of the wave-age and the sea spray source functions as well as the modification of the overseas drag coefficients. Two different surface roughness parameterizations are tested and compared with ERA5 reanalysis data from the ECMWF - Copernicus Climate Change Service. A single case study is performed considering the cyclone Rolf that occurred between 5 and 9 November 2011 in the western Mediterranean basin. It is considered one of the longest-lasting and most intense tropical-like cyclones in the Mediterranean with more than 48-h occurrence of tropical-like features and a wind speed peak reaching 30 m s−1 in its mature phase. The role of sea spray is evaluated considering two basic strategies, namely the limited-saturation layer approach and the “sea spray force” on the momentum balance. It is demonstrated that (i) the formulation based on the limited-saturation layer approach is better suited for describing the drag in the cyclonic region, where velocities are highest and consequently there is a very high concentration of sea-spray spume droplets; (ii) the momentum drag level-off at the highest wind speed. Our results give a contribution on the understanding of the air-sea flux parameterizations for a range of wind speed above 25–35 m s−1, indicating that sea-spray generation should be accounted for in coupled numerical models for ocean and atmosphere.

Identification of Failure Regions for Programs With Numeric Inputs

Failure region, where failure-causing inputs reside, has provided many insights to enhance testing effectiveness of many testing methods. Failure region may also provide some important information to support other processes such as software debugging. When a testing method detects a software failure, indicating that a failure-causing input is identified, the next important question is about how to identify the failure region based on this failure-causing input, i.e., Identification of Failure Regions (IFR). In this paper, we introduce a new IFR strategy, namely Search for Boundary (SB), to identify an approximate failure region of a numeric input domain. SB attempts to identify additional failure-causing inputs that are as close to the boundary of the failure region as possible. To support SB, we provide a basic procedure, and then propose two methods, namely Fixed-orientation Search for Boundary (FSB) and Diverse-orientation Search for Boundary (DSB). In addition, we implemented an automated experimentation platform to integrate these methods. In the experiments, we evaluated the proposed SB methods using a series of simulation studies and empirical studies with different types of failure regions. The results show that our methods can effectively identify a failure region, within the limited testing resources.

Review on numerical techniques applied in impulse hydro turbines

Abstract Impulse turbines are widely used in hydropower plants around the world due to their high efficiency in a larger operating range compared to reaction turbines. State of the art Pelton turbines can give over 90% efficiency at the designed operation load. However, there lies a possibility of improving the efficiency at off design condition for these turbines by optimizing the design of the nozzles, runner and/or housing. Prediction of the performance of the turbines by numerical techniques allows a quicker design optimization and at a much lower cost. In the case of impulse turbines, the use of CFD is limited by the complex nature of the flow, interaction of the jets, water/air mixture and interference of water after the impact on the successive buckets. Unlike reaction turbines, where the performances of the turbines could be studied through time-independent analysis to some extent, transient simulations are inevitable for the impulse turbines. Moreover, need for the multiphase models add to the overall complexities of CFD. Some recent development includes the use of Lagrangian scheme, which has reduced the computational efforts significantly. In the conventional Eulerian schemes, it is found that the numerical domains are usually simplified, either by using symmetry (half bucket) or rotational periodicity options. With the development of the computational capacity, some recent studies have also performed full turbine’s simulation, using nearly 50 million mesh elements. The design optimizations are performed on the shapes of the bucket, jet, deflectors as well as the turbine’s casings. However, validation of the numerical solutions remains a challenging topic with the quality of the mesh being used currently. Nevertheless, progresses in the numerical techniques and computing power within the last 15 years have strengthened the prospects of utilizing CFD and FEM as primary tools for validating and optimizing the design of the impulse turbines.

Numerical Simulation of River Inflows in Rijeka Bay Coastal Area

In this paper, a model of water flow in the Porto Baroš has been developed, which is the part of the Rijeka coastal area, for the purpose of its renovation and conversion. For numerical simulation purposes, the depth of the seabed of Port was previously performed, based on which the geometry and numerical domain of Port were made. By conducting the flow simulation, the analysis was carried out, after which the analyses of the conceptual solutions with the introduction of the pipe discharge were performed with the aim of reducing the water pollution of the Porto Baroš area. Port geometry will be made in commercial SMS software and numerical domains and simulations in OpenFOAM open-source software.

Optimisation and Management of Energy Generated by a Multifunctional MFC-Integrated Composite Chassis for Rail Vehicles

With the advancing trend towards lighter and faster rail transport, there is an increasing interest in integrating composite and advanced multifunctional materials in order to infuse smart sensing and monitoring, energy harvesting and wireless capabilities within the otherwise purely mechanical rail structures and the infrastructure. This paper presents a holistic multiphysics numerical study, across both mechanical and electrical domains, that describes an innovative technique of harvesting energy from a piezoelectric micro fiber composites (MFC) built-in composite rail chassis structure. Representative environmental vibration data measured from a rail cabin have been critically leveraged here to help predict the actual vibratory and power output behaviour under service. Time domain mean stress distribution data from the Finite Element simulation were used to predict the raw AC voltage output of the MFCs. Conditioned power output was then calculated using circuit simulation of several state-of-the-art power conditioning circuits. A peak instantaneous rectified power of 181.9 mW was obtained when eight-stage Synchronised Switch Harvesting Capacitors (SSHC) from eight embedded MFCs were located. The results showed that the harvested energy could be sufficient to sustain a self-powered structural health monitoring system with wireless communication capabilities. This study serves as a theoretical foundation of scavenging for vibrational power from the ambient state in a rail environment as well as to pointing to design principles to develop regenerative and power neutral smart vehicles.

Uma proposta de articulações entre Álgebra Vetorial e GeoGebra

Neste trabalho, apresentamos algumas produções oriundas de um minicurso realizado em um evento direcionado a licenciandos e professores de matemática da Educação Básica. Destarte que, apenas estudantes realizaram inscrição nesta atividade. A proposta do minicurso constituiu-se a partir de um estudo do trânsito entre as diferentes representações vetoriais nos domínios numérico, algébrico e geométrico, subsidiado pelo software GeoGebra, com o intuito de apontar caminhos para a instauração de pressupostos do emergente Paradigma de Questionamento do Mundo, cujos pilares se assentam no despertar de uma visão prospectiva que se opõe ao Paradigma de Visitação de Obras. Nesta perspectiva, tomamos como aporte teórico a Teoria Antropológica do Didático – TAD, a qual possui um dos fundamentos centrado nas análises das atividades didáticas matemáticas em torno de uma modelação praxeológica pontual, por meio da interação entre os blocos prático e teórico. As atividades foram planejadas e desenvolvidas contemplando-se tarefas que geralmente são tratadas em aulas ou avaliações sobre a teoria de vetores no plano, objetivando-se apontar direções para integrar o software às aulas que abordam a álgebra vetorial. Em termos de resultados, identificamos que os participantes abandonaram a postura estática e coadjuvante imposta no modelo tradicional de ensino e assumiram um papel protagonista nas atividades desenvolvidas, tanto no ambiente “papel lápis” quanto no âmbito virtual, contribuindo, desta forma, com a formação de futuros professores de matemática que questionem e não apenas visitem obras.

Framework for progressive adaption of FE mesh to simulate generative manufacturing processes

Many conventional Finite Element (FE) simulations are based on predefined numerical domains. This creates challenges with the nature of dynamic manufacturing processes, where components are gradually produced in time. Although, conventional element (de-)activation technique is hesitantly used to simulate such processes, functionality of the proposed framework herein allows to append new elements to the existing elements. The aim of the framework is to reproduce the progress of the real process within a dynamically growing numerical domain. The dynamic mesh generation and its implementation are briefly presented and a simulation of a mesh build up for a WAAM process is shown.

Local knot method for 2D and 3D convection–diffusion–reaction equations in arbitrary domains

In this paper, a novel local knot method (LKM) is presented to solve the 2D and 3D convection–diffusion–reaction equations in arbitrary domains. Contrary to the traditional boundary knot method, the proposed scheme requires the nodes not only on the boundary but also inside the domain. For each node, we can find a local subdomain containing a certain number of neighboring nodes. Utilizing the non-singular general solution of differential operator and the known boundary conditions, a sparse linear system is established to approximate the solutions at all nodes over the physical domain. The present LKM is a local meshless method with the merits of being mathematically simple, numerically accurate and easy to large-scale computation. Two numerical examples, involving 2D and 3D complicated domains, are provided to illustrate the effectiveness and accuracy of the new methodology.

Fire behaviour of ecological soil–cement blocks with waste incorporation: Experimental and numerical analysis

The main goal of this study is to assess the behaviour of soil–cement blocks with incorporation of organic wastes. The problem of waste accumulation exists worldwide and has become a concern in today’s society, leading to enormous environmental damage. One of the possibilities for reducing their environmental impact is the reuse of these wastes in new materials. However, incorporating waste changes the mechanical, physical and thermal properties of the new material. In order to evaluate the potential use of waste in blocks composition, laboratory tests were conducted and the results were analysed. This article presents the fire behaviour of ecological soil–cement blocks with waste incorporation. Therefore, an experimental programme was performed using samples of wall panel with soil–cement blocks. The wall specimen under fire conditions was also analysed by a non-linear transient finite element numerical model, in time and temperature domains, and the numerical and experimental temperature fields were compared.

Reasoning with words: A hedge algebra linguistic cognitive map approach

SummaryIn this article, we introduce a method for reasoning with words based on hedge algebra using linguistic cognitive map. Our model consists of set of vertices and edges with value to be linguistic variables which are constrained by linguistic lattice. We figure out relationship between numeric and linguistic domain for fuzzifying data. We also prove convergence theorem on learning method for linguistic cognitive map.

Uncertainty Quantification

Uncertainty quantification (UQ) is concerned with including and characterising uncertainties in mathematical models. Major steps comprise proper description of system uncertainties, analysis and efficient quantification of uncertainties in predictions and design problems, and statistical inference on uncertain parameters starting from available measurements. Research in UQ addresses fundamental mathematical and statistical challenges, but has also wide applicability in areas such as engineering, environmental, physical and biological applications. This workshop focussed on mathematical challenges at the interface of applied mathematics, probability and statistics, numerical analysis, scientific computing and application domains. The workshop served to bring together experts from those disciplines in order to enhance their interaction, to exchange ideas and to develop new, powerful methods for UQ.

Numerical simulation of transpiration cooling experiments in supersonic flow using OpenFOAM

Transpiration cooling applied to modern ceramic matrix composite materials is an interesting concept for thermal protection of future aerospace applications. Therefore, reliable and accurate numerical tools for the simulation of transpiration cooling processes in complex flow situations and for complex porous geometries are needed. In this study, we present a fully coupled OpenFOAM solver and discuss the choice of suitable interface conditions as well as the coupling of numerical domains at the transpired surface. Additionally, a modified turbulence boundary condition for transpiration through low-porosity materials is proposed. The numerical solver is then applied to validation test cases with a flat and a double-wedge porous sample under blowing ratios up to $$F_{\text{Air}} = 0.75\%$$. The corresponding experiments with Carbon/Carbon samples were performed at the ITLR Hot Gas Facility at supersonic steady-state conditions, i.e. $${\text{Ma}} = 2.5$$ and $$T_{t} = 500\;{\text{K}}$$. The simulation results are in good overall agreement with the experimental data for both test cases while capturing the influences of blowing ratio, as well as variations of the external flow field and in the heat flux distribution. Temperature predictions for the sample surface, within the porous wall, and in the downstream wake region show a good conformity to measurements, whereas deviations are observed in the direct wake. Based on the complementary insights provided by the numerical results, aspects such as the coolant through-flow behaviour as well as the sample’s internal temperature distribution and heat conduction are analysed.

A generating and absorbing boundary condition for dispersive waves in detailed simulations of free-surface flow interaction with marine structures

The boundaries of numerical domains for free-surface wave simulations with marine structures generate spurious wave reflection if no special measures are taken to prevent it. The common way to prevent reflection is to use dissipation zones at the cost of increased computational effort. On many occasions, the size of the dissipation area is considerably larger than the area of interest where wave interaction with the structure takes place. Our objective is to derive a local absorbing boundary condition that has equal performance to a dissipation zone with lower computational cost. The boundary condition is designed for irregular free-surface wave simulations in numerical methods that resolve the vertical dimension with multiple cells. It is for a range of phase velocities, meaning that the reflection coefficient per wave component is lower than a chosen value, say 2%, over a range of values for the dimensionless wave number kh. This is accomplished by extending the Sommerfeld boundary condition with an approximation of the linear dispersion relation in terms of kh, in combination with vertical derivatives of the solution variables. For this article, the boundary condition is extended with a non-zero right-hand side in order to prevent wave reflection, while, at the same time, at the same boundary, generating waves that propagate into the domain. Results of irregular wave simulations are shown to correspond to the analytical reflection coefficient for a range of wave numbers, and to have similar performance to a dissipation zone at a lower cost.

Mountain‐Block Recharge: A Review of Current Understanding

AbstractMountain‐block recharge (MBR) is the subsurface inflow of groundwater to lowland aquifers from adjacent mountains. MBR can be a major component of recharge but remains difficult to characterize and quantify due to limited hydrogeologic, climatic, and other data in the mountain block and at the mountain front. The number of MBR‐related studies has increased dramatically in the 15 years since the last review of the topic was conducted by Wilson and Guan (2004), generating important advancements. We review this recent body of literature, summarize current understanding of factors controlling MBR, and provide recommendations for future research priorities. Prior to 2004, most MBR studies were performed in the southwestern United States. Since then, numerous studies have detected and quantified MBR in basins around the world, typically estimating MBR to be 5–50% of basin‐fill aquifer recharge. Theoretical studies using generic numerical modeling domains have revealed fundamental hydrogeologic and topographic controls on the amount of MBR and where it originates within the mountain block. Several mountain‐focused hydrogeologic studies have confirmed the widespread existence of mountain bedrock aquifers hosting considerable groundwater flow and, in some cases, identified the occurrence of interbasin flow leaving headwater catchments in the subsurface—both of which are required for MBR to occur. Future MBR research should focus on the collection of high‐priority data (e.g., subsurface data near the mountain front and within the mountain block) and the development of sophisticated coupled models calibrated to multiple data types to best constrain MBR and predict how it may change in response to climate warming.

The Permeability of Columnar Jointed Lava

AbstractColumnar jointed lava is an important facies in many geothermal reservoir systems. The permeability of jointed lavas is dominated by the contribution from fracture networks. We use a scaling for the permeability of a set of fractures in a solid or porous mass and extend this to arrays of hexagonal intercolumn fractures. To validate our analytical results, we create numerical domains with relevant geometries and extract system‐scale permeability using the LBflow lattice‐Boltzmann fluid flow simulation tool. Finally, we model the cooling contraction of columns to extend our results so that they predict the permeability with time after lava emplacement. Importantly, we use these results to estimate the range of permeabilities typical of columnar joints that form during cooling from high temperature and are preserved in the crust at moderate to low temperatures.

Preoperative opioid use in patients undergoing shoulder surgery.

Opioids are commonly used to manage pain from acute injury or chronic degenerative diseases. The objective of this study was to assess the prevalence of preoperative opioid use in patients undergoing shoulder surgery and the clinical factors associated with preoperative opioid use. This was an analytical cross-sectional study of 175 patients undergoing shoulder surgery at an urban hospital from June 2015 to June 2017. Multivariable regression models were used to determine independent associations. Fifty-three patients reported preoperative opioid use, which was significantly associated with primary procedure performed (Current Procedural Terminology [CPT]), higher body mass index (BMI), unemployment, lower income, smoking, higher American Society of Anesthesiologists score, greater number of previous surgeries, higher comorbidity burden, and decreased expectations to exercise and do recreational activities (p < 0.05). Preoperative opioid use was independently associated with worse scores on the: Numeric Pain Scale, ASES, IPAQ, and PROMIS domains of Physical Function, Pain Interference, and Social Satisfaction (p < 0.05). More than one in four patients reported preoperative opioid use. Several health measures, including worse pain, function, and social satisfaction were independently associated with preoperative opioid use. These findings suggest that orthopaedic surgeons need to identify patients using opioids preoperatively in order to effectively establish and execute a plan for pain management, which may include weaning off opioids prior to surgery, managing psychological distress, and optimizing coping strategies.Level of Evidence: III.

Individual differences in parietal and frontal cortex structure predict dissociable capacities for perception and cognitive control

Capacity limits in perception can lead to failures of awareness in situations that overload capacity, resulting in various phenomena of ‘inattentional blindness’. In contrast, capacity limits in cognitive control over attention by working memory lead to increased processing of irrelevant distractors (reduced inattentional blindness). Here, using Voxel-Based Morphometry combined with Principal Components Analysis, we establish distinct brain-structural correlates of perceptual capacity, dissociable from those of cognitive control. Perceptual capacity was measured as the principal component accounting for variance across tasks of multiple object tracking, change blindness and rapid visual enumeration (i.e. ‘subitizing’). Cognitive control capacity was measured as the principal component underlying performance of three different complex working memory span tasks (involving spatial, semantic and numerical domains). Volumetric differences in the right Inferior Parietal Lobule (IPL) were predictive of individual differences in perceptual capacity, while volumetric differences in left Middle Frontal Gyrus (MFG) (as well as lateral frontal and posterior cingulate cortex in a non-parametric analysis) were predictive of individual differences in cognitive control capacity. IPL remained a significant predictor of perceptual capacity when controlling for variance accounted for by cognitive control capacity and vice versa for the neural correlates of cognitive control. These results suggest that perceptual and cognitive control capacities represent dissociable and lasting, trait-like attributes which can be predicted from distinct signatures in regional grey matter.

Hierarchical Analysis of Loops With Relaxed Abstract Transformers

Numerical computation is often involved in software of embedded control systems, cyber-physical systems, artificial neural network systems, big data processing systems, etc. Automatically discovering numerical loop invariants is fundamental for checking the safety of such software. Abstract interpretation provides a framework to automatically discover sound invariants but which may be not precise enough due to over-approximations. One major source of precision loss is due to the limited linear expressiveness of most widely used numerical abstract domains and the widening operation. This becomes more serious when analyzing all variables simultaneously as a whole for programs that involve nonlinear behaviors. Based on the observation that the dependency among variables in a loop can be hierarchical, in this article, we propose a hierarchical static analysis to analyze a loop by utilizing relaxed abstract transformers. The main idea is to first partition all variables involved in a loop into different hierarchical layers, then compute invariants over the variables layer by layer in a bottom-up manner. During the iterative process, the computed invariants over lower layer variables are then used to relax transfer functions when analyzing the higher layer variables. One benefit of our method lies in that it can generate linear invariants to soundly enclose nonlinear behaviors in a loop. Finally, we present encouraging experimental results on benchmark programs involving nonlinear behaviors.

A hybrid method for ship response coupled with sloshing in partially filled tanks

An efficient hybrid numerical method was developed to study wave-induced ship response coupled with sloshing-induced compressible fluid response in partially filled tanks of a 138,000 m3 liquefied natural gas carrier at zero speed in regular head and beam waves. A nonlinear boundary element Rankine source code, solving the incompressible incident flow field, accounted for the nonlinear stationary forward speed problem and the weakly nonlinear seakeeping problem. A Reynolds-averaged Navier-Stokes equations solver, computing the compressible sloshing flow in tanks, considered the associated discontinuous numerical domains of coupled simulations. Grid sensitivity studies were performed. Comparative available experimental model test measurements of ship response and free surface sloshing elevations in tanks validated the numerical method. Further investigations regarding the influence of wave steepness and tank fill levels on sloshing were performed. Results demonstrated that liquid sloshing in tanks had a large influence on ship surge and roll responses but hardly effected ship heave motions.

Advanced Driving Behavior Analytics for an Improved Safety Assessment and Driver Fingerprinting

The recent computerizations of cars, together with the development of sensor technologies and car communication devices have transformed the cars into wealthy sources of information. The analysis of data generated continuously by cars can contribute greatly in improving driving safety and drivers comfort. Even though different analytical solutions have emerged recently, there still exist some important issues in driving safety that we assume were poorly addressed, as well as diverse mathematical methodologies whose application in driving behavior analysis is to be investigated. In this paper, we developed a methodology to process and analyze car-generated data, with focus on two analysis goals: 1) automatic verification of drivers’ behavior conformity to traffic rules; and 2) visualization and comparison of drivers’ behaviors. The proposed methodology is divided into three steps. At first, the abstraction using numerical domains is used to reduce the size of the generated data. Then, the probabilistic graphical models (Probabilistic Automata, and Labeled Directed Graphs) combined with a machine-learning algorithm are used for building a formal model of the driver behavior. Finally, two indepth analyses are carried out by applying automatic model checking and graph matching techniques. Early experimental results point out that the design of numerical domains considered influences hugely the analysis results.