Adaptive Resolution Research Articles

Ocean Modeling with Adaptive REsolution (OMARE; version 1.0) – refactoring the NEMO model (version 4.0.1) with the parallel computing framework of JASMIN – Part 1: Adaptive grid refinement in an idealized double-gyre case

Abstract. High-resolution models have become widely available for the study of the ocean's small-scale processes. Although these models simulate more turbulent ocean dynamics and reduce uncertainties of parameterizations, they are not practical for long-term simulations, especially for climate studies. Besides scientific research, there are also growing needs from key applications for multi-resolution, flexible modeling capabilities. In this study we introduce the Ocean Modeling with Adaptive REsolution (OMARE), which is based on refactoring Nucleus for European Modelling of the Ocean (NEMO) with the parallel computing framework of JASMIN (J parallel Adaptive Structured Mesh applications INfrastructure). OMARE supports adaptive mesh refinement (AMR) for the simulation of the multi-scale ocean processes with improved computability. We construct an idealized, double-gyre test case, which simulates a western-boundary current system with seasonally changing atmospheric forcings. This paper (Part 1) focuses on the ocean physics simulated by OMARE at two refinement scenarios: (1) 0.5–0.1∘ static refinement and the transition from laminar to turbulent, eddy-rich ocean, and (2) the short-term 0.1–0.02∘ AMR experiments, which focus on submesoscale processes. Specifically, for the first scenario, we show that the ocean dynamics on the refined, 0.1∘ region is sensitive to the choice of refinement region within the low-resolution, 0.5∘ basin. Furthermore, for the refinement to 0.02∘, we adopt refinement criteria for AMR based on surface velocity and vorticity. Results show that temporally changing features at the ocean's mesoscale, as well as submesoscale process and its seasonality, are captured well through AMR. Related topics and future plans of OMARE, including the upscaling of small-scale processes with AMR, are further discussed for further oceanography studies and applications.

A pressure-dependent adaptive resolution scheme for smoothed particle hydrodynamics simulation of underwater explosion

For promoting numerical efficiency in smoothed particle hydrodynamics (SPH) simulation of underwater explosion, a pressure-dependent adaptive resolution scheme (PARS) is proposed. The approach involves dividing computation domain into several regions of different resolution and automatic splitting or merging particles in these regions. Methods are established for identifying resolution regions and for adapting particle resolutions, so that the wave front and the zone with sharp pressure variation is dynamically covered in the region of the highest resolution. Numerical examples are present to demonstrate that the proposed technique can reduce significantly the number of particles and computing time to produce solutions of adequate accuracy. The main features of shockwave propagation can be well captured using much less particles. For large scale or 3D problems, the technique can be decisive for completing a numerical simulation. Numerical examples also testified that the proposed PARS is robust and effective in capturing the complicated phenomena of wave interferences and interaction between shock wave and solid barrier.

On methodology and application of smoothed particle hydrodynamics in fluid, solid and biomechanics.

Smoothed particle hydrodynamics (SPH), as one of the earliest meshfree methods, has broad prospects in modeling a wide range of problems in engineering and science, including extremely large deformation problems such as explosion and high velocity impact. This paper aims to provide a comprehensive overview on the recent advances of SPH method in the fields of fluid, solid, and biomechanics. First, the theory of SPH is described, and improved algorithms of SPH with high accuracy are summarized, such as the finite particle method (FPM). Techniques used in SPH method for simulating fluid, solid and biomechanics problems are discussed. The δ-SPH method and Godunov SPH (GSPH) based on the Riemann model are described for handling instability issues in fluid dynamics. Next, the interface contact algorithm for fluid-structure interaction is also discussed. The common algorithms for improving the tensile instability and the framework of total Lagrangian SPH are examined for challenging tasks in solid mechanics. In terms of biomechanics, the governing equations and the coupling forces based on SPH method are exemplified. Then, various typical engineering applications and recent advances are elaborated. The application of fluid mainly depicts the interaction between fluid and rigid body as well as elastomer, while some complicated fluid-structure interaction ocean engineering problems are also presented. In the aspect of solid dynamics, galaxy, geotechnical mechanics, explosion and impact, and additive manufacturing are summarized. Furthermore, the recent advancements of SPH method in biomechanics, such as hemodynamically and gut health, are discussed in general. In addition, to overcome the limitations of computational efficiency and computational scale, the multiscale adaptive resolution, the parallel algorithm and the automated mesh generation are addressed. The development of SPH software in China and abroad is also summarized. Finally, the challenging task of SPH method in the future is summarized. In future research work, the establishment of multi-scale coupled SPH model and deep learning technology in solid and biodynamics will be the focus of expanding the engineering applications of SPH methods.

A Generic Framework for Multiscale Simulation of High and Low Enthalpy Fractured Geothermal Reservoirs under Varying Thermodynamic Conditions

We develop a multiscale simulation strategy, namely, algebraic dynamic multilevel (ADM) method, for simulation of fluid flow and heat transfer in fractured geothermal reservoirs under varying thermodynamic conditions. Fractures with varying conductivities are modeled using the projection-based embedded discrete fracture model (pEDFM) in an explicit manner. The developed ADM method allows the fine-scale system to be mapped to a discrete domain with an adaptive grid resolution via the use of the restriction and prolongation operators. The developed framework is used (a) to investigate the impacts of formulations with different primary variables on the simulation results, and (b) to assess the performance of ADM in a high-enthalpy reservoir by comparing the simulation results against those obtained from fine-scale grids. Results show that the two formulations produce similar results in the case of single-phase flow, which indicates that the molar formulation is a favorable option that can be applied to varying thermodynamic conditions. Moreover, the ADM can provide accurate solutions with only a fraction of fine-scale grids, e.g., for the studied case, the maximum error is by average 1.3 with only 42% of active cells, thereby improving the computational efficiency. This is promising for applying the developed method to field-scale geothermal systems.

МОДЕЛИРОВАНИЕ АЭРОДИНАМИЧЕСКОГО ВЗАИМОДЕЙСТВИЯ ПРИ ТРЕКОВЫХ ИСПЫТАНИЯХ ИЗДЕЛИЙ АВИАЦИОННОЙ ТЕХНИКИ

Ground track tests of modern ballistic-type aircraft products make it possible to simulate aerodynamic loads in conditions with a maximum medium density and having a significantly lower cost compared to flight tests. During track testing of products at supersonic speeds, intense vibrations of the structural elements of the movable track equipment and the product under test occur. The article deals with the processes of air flow around a rail installation moving with a high acceleration. Basic models are applied that describe the motion of a homogeneous medium at various velocities, accounting the effects of compressibility, turbulence, and heat transfer. Depending on the conditions, various flow turbulence models are used. An algorithm for numerical implementation on a rectangular grid with local adaptation and subgrid resolution of complex geometry is developed. The methodology for the numerical solution of the equations of dynamics describing the flow of a compressible gas around a curved surface is based on the integration of fluid motion and the transfer of scalar quantities in partial derivatives with respect to the volumes of computational cells-polyhedrons. Using the FlowVision software package, the simulation of the supersonic air flow around products of various shapes was performed in relation to track tests. This made it possible to determine previously unknown dependences of the coefficients of aerodynamic drag, lift force and lateral force on the speed of motion, as well as the moments of aerodynamic forces for estimating the contribution of airflow processes to the total vibration field acting on the track carriage with the product.

Directions of strategic conflict management that contribute to increasing the economic efficiency of enterprises

The article explores the areas of strategic conflict management that contribute to improving the efficiency of enterprises operating in the agro-industrial complex. There have been used methods of cognition during the study: analysis, synthesis, concretization and abstraction, classification, grouping, and others. There have been given some definitions of the terms based on the study: strategy, conflict and its elements. There have been studied the stages of conflict development at the enterprise and the main causes of the conflicts. We have compared the approaches to conflicts in the organization, developed a matrix of risks that affect the economic efficiency of the enterprise and selected the main types of interpersonal conflicts at the enterprises for the study. During the study, a direct relationship has been revealed between the frequency of occurrence of conflict situations and the economic efficiency of the enterprise, as a result of which styles of behavior have been developed for the management personnel of economic entities in case of conflict situations. The study has allowed to identify the following problems in conflict management at pilot enterprises: an increase in the number of conflicts between departments; the cause of conflicts is often connected with the shift in areas of responsibility in the performance of duties; ignoring the psychological incompatibility of employees when hiring; selection of compromise or adaptive resolution options. To eliminate the identified problems, the directions of strategic conflict management for pilot enterprises were outlined: the formation of a checklist for diagnosing conflicts; development of a conflict management matrix; use of all styles of behavior in conflict situations; timely response to the emerging conflict situation.

An Adaptive Sparse Constraint ISAR High Resolution Imaging Algorithm Based on Mixed Norm

An Adaptive Sparse Constraint ISAR High Resolution Imaging Algorithm Based on Mixed Norm

Simulation of a Particle Domain in a Continuum, Fluctuating Hydrodynamics Reservoir.

In molecular simulation and fluid mechanics, the coupling of a particle domain with a continuum representation of its embedding environment is an ongoing challenge. In this Letter, we show a novel approach where the latest version of the adaptive resolution scheme (AdResS), with noninteracting tracers as particles' reservoir, is combined with a fluctuating hydrodynamics (FHD) solver. The resulting algorithm, supported by a solid mathematical model, allows for a physically consistent exchange of matter and energy between the particle domain and its fluctuating continuum reservoir. Numerical tests are performed to show the validity of the algorithm. Differently from previous algorithms of the same kind, the current approach allows for simulations where, in addition to density fluctuations, also thermal fluctuations can be accounted for, thus large complex molecular systems, as, for example, hydrated biological membranes in a thermal field, can now be efficiently treated.

How to train your solver: Verification of boundary conditions for smoothed particle hydrodynamics

The weakly compressible smoothed particle hydrodynamics (WCSPH) method has been employed to simulate various physical phenomena involving fluids and solids. Various methods have been proposed to implement the solid wall as well as inlet and outlet boundary conditions. However, error estimation and the formal rates of convergence for these methods have not been carefully discussed or examined. In this paper, we use the method of manufactured solutions to verify the convergence properties of a variety of commonly employed solid, inlet, and outlet boundary implementations. In order to perform this study, we propose various manufactured solutions for different domains. On the basis of the convergence offered by these methods, we systematically propose a convergent WCSPH scheme along with suitable methods for implementing the boundary conditions. We also demonstrate the accuracy of the proposed scheme by using it to solve the flow past a circular cylinder. Along with other recent developments in the use of adaptive resolution, this paves the way for accurate and efficient simulation of incompressible or weakly compressible fluid flows using the SPH method.

Simulating the magnetorotational instability on a moving mesh with the shearing box approximation

ABSTRACT The magnetorotational instability (MRI) is an important process in sufficiently ionized accretion discs, as it can create turbulence that acts as an effective viscosity, mediating angular momentum transport. Due to its local nature, it is often analysed in the shearing box approximation with Eulerian methods, which otherwise would suffer from large advection errors in global disc simulations. In this work, we report on an extensive study that applies the quasi-Lagrangian, moving-mesh code arepo, combined with the Dedner cleaning scheme to control deviations from $\nabla \cdot \boldsymbol B=0$, to the problem of magnetized flows in shearing boxes. We find that we can resolve the analytical linear growth rate of the MRI with mean background magnetic field well. In the zero net flux case, there is a threshold value for the strength of the divergence cleaning above which the turbulence eventually dies out, and in contrast to previous Eulerian simulations, the strength of the MRI does not decrease with increasing resolution. In boxes with larger vertical aspect ratio we find a mean-field dynamo, as well as an active shear current effect that can sustain MRI turbulence for at least 200 orbits. In stratified simulations, we obtain an active αω dynamo and the characteristic butterfly diagram. Our results compare well with previous results obtained with static grid codes such as athena. We thus conclude that arepo represents an attractive approach for global disc simulations due to its quasi-Lagrangian nature, and for shearing box simulations with large density variations due to its continuously adaptive resolution.

LENS: Bandwidth-efficient video analytics with adaptive super resolution

Video streaming analytic pipelines are deployed widely nowadays, where in many cases videos are transmitted continuously from cameras to servers. However, video analytic accuracy highly depends on video resolution, and when bandwidth suffers only low-resolution videos can be transmitted which leads to low accuracy. The rapid development of super resolution DNNs sparks the possibility of reconstructing high-resolution videos reliably from low resolution videos, and thus boosts video analytic accuracy. However, pretrained SR models may fail to cope with dynamic video content, while introducing online learning can be efficient under this condition. In this paper, we propose a practical system, LENS, which integrates an online learning period into analytic pipelines. The experimental results show that LENS is capable of responding to video dynamics and retraining SR models for changes quickly. In summary, LENS can save bandwidth consumption by up to 87%, or achieve a higher accuracy by up to 9.6% compared with state-of-the-art methods with slight additional bandwidth.

Simulation of two successive drops impacting a heated wall by smoothed particle hydrodynamics with adaptivespatial resolution

<p indent="0mm">A numerical method for evaporating multiphase flow was developed by introducing a diffusion equation of species and a phase change model to smoothed particle hydrodynamics with adaptive spatial resolution (SPH-ASR). The method was applied to study the impact problem of two successive drops on a heated wall. The numerical method was validated against experimental results. Different factors were considered in the simulations, including drop diameter, impact velocity, wall temperature and wall inclined angle. The typical impact regimes were obtained, including spread, breakup, contact splash, rebound, and film splash. The numerical results indicated that the outcome of two drops impacting a solid wall mainly depends on the temperature and inclined angle of the wall, Weber number, and Reynolds number. Different phase diagrams of impact regimes were obtained using different parameters. A linear relationship between the critical Weber number of splash and the inclined angle of wall was obtained by data fitting.

Troposphere Delay Remote Sensing Using Single GPS Receiver

The most prominent spatially correlated errors in GNSS observations are well known to be atmospheric effects. The ionosphere and troposphere are the two main layers of the Atmosphere that cause delays in GNSS observations. A linear combination of the dual-frequency data can be used to reduce ionospheric delay. Unlike the ionospheric delay, the tropospheric delay cannot be eliminated using the same methods. The troposphere is primarily associated with GPS. The delay it causes in GPS signals is regarded as one of the primary sources of errors that must be eliminated to determine accurate positions. This paper's main purpose is to develop a new source code that can estimate the effect of tropospheric delay over any GPS station. The tropospheric delay in this proposed code is estimated utilizing sequential least-squares adjustment using a model depending on Niell Mapping Function (NMF). This model, known as the Tropospheric Delay Estimation program, was created in the MATLAB® environment (TDE). This research presents the results of tropospheric delay during DOY 2, 2020 of actual data from ten ground-based IGS stations distributed over Antarctica, China, Canada, Fiji, Russia, Greenland, and Portugal IGS stations worldwide. For validation of the proposed code results, they were compared with troposphere delay results of the International GNSS Service (IGS). Good agreement and high correlation were found between both results. In comparison to IGS, the proposed code's standard deviations range from 0.0000525 m to 0.008154 m, indicating how accurate this study is in terms of agreement of solutions provided by IGS. Finally, the MATLAB software can accurately estimate troposphere delay with an adaptable temporal resolution for GPS users.

Rigorous coupled wave analysis upgraded with combined boundary conditions method for 2D metamaterials in microwave.

We combine rigorous coupled wave analysis (RCWA) and combined boundary conditions method (CBCM) to analyze optical properties of two-dimensional periodic metamaterial grating with arbitrary shapes in microwave domain, and the adaptive spatial resolution (ASR) function is introduced to increase convergence especially for the crossed metamaterial gratings. The numerical results show that RCWA with CBCM can get the correct convergence result and distinguish the contribution of the grating lobes to the total transmission and reflection. The ASR technique improves dramatically the convergence speed of crossed grating. This method provides a more effective computational tool for the design of metamaterial grating in microwave domain.

Optimised Adjoint Sensitivity Analysis Using Adjoint Guided Mesh Adaptivity Applied to Neutron Detector Response Calculations

This article presents a new approach for the efficient calculation of sensitivities in radiation dose estimates, subject to imprecisely known nuclear material cross-section data. The method is a combined application of adjoint-based models to perform, simultaneously, both the sensitivity calculation together with optimal adaptive mesh refinement. Adjoint-based sensitivity methods are known for their efficiency since they enable sensitivities of all parameters to be formed through only two solutions to the problem. However, the efficient solutions can also be obtained by their computation on optimal meshes, here guided by goal-based adjoint approaches. It is shown that both mesh adaptivity and sensitivity can be computed by the same adjoint solution, meaning both can be performed without additional costs. A simple demonstration is presented based on the Maynard fixed-source problem where uncertainties, with respect to material cross-sections, of doses received in local regions are examined. It is shown that the method is able to calculate sensitivities with reduced computational costs in terms of memory and potentially computational time through reduced mesh size when using adaptive resolution in comparison to uniform resolution. In particular, it is the local spatial contributions to the sensitivity that are resolved more effectively due to the adaptive meshes concentrating resolution in those areas contributing the most to its value.

Unknown terrain imaging with adaptive spatial resolution using UAV

Recently, Unmanned Aerial Vehicles (UAVs), or drones equipped with advanced cameras, have introduced a major revolution in surveying wide landscapes to collect ground data very fast. Capturing images of an unknown area with the desired resolution is of utmost importance for many real-life applications. For a UAV fitted with a given camera, its altitude from the ground surface primarily determines the spatial resolution of mapping. Hence, for an uneven terrain, it is a great challenge to maneuver the UAV dynamically to capture snapshots maintaining the desired spatial resolution throughout the area. This paper proposes a novel fully-automated technique for simple nadir drones to capture images of an unknown 3D terrain satisfying a predefined spatial resolution criterion. Also, an adaptive real-time flight path planning scheme is presented to minimize the distance traversed by the drone. A detailed performance evaluation study on real terrain data shows that the proposed technique can cover almost 97−99% of the area, maintaining the specified resolution with an almost 46−59% reduction in the path length compared to the conventional techniques.

Underwater Macroplastic Detection Using Imaging Sonars

Plastic pollution in the ocean occurs mainly via riverine transport. In rivers, plastic is pervasive in sediments and in the water column. Monitoring of floating plastics in rivers is time consuming as it is usually collected using nets and classified by hand, or counted and classified visually. To make plastic detection in the water column more time- and cost-efficient, there is a need to explore remote sensing options. Here we present the results of two semi-controlled pilot tests in standing water using two imaging sonar technologies: an Adaptive Resolution Imaging Sonar (ARIS) sonar and a low-cost side-scan sonar (SSS). Additionally, the ARIS sonar was tested in flowing water at a sheltered shore channel behind a longitudinal training dam in the river Waal, Netherlands. Both technologies were able to detect 100% of the macroplastics tested in standing water. The ARIS sonar provided higher resolution images of the targets tested due to its high operation frequency detecting macroplastics down to a size of 1 cm2. The ARIS sonar detected macroplastics in the field, however, the detection decreased to 67% in flowing water. This sonar was limited to the 2D horizontal position of targets. The SSS is a low-cost option for monitoring of plastics and is integrated with CHIRP sonar technology that combines side and down imaging providing the 3D position of targets. For future monitoring, an ARIS sonar in motion or two ARIS sonars used simultaneously may provide the necessary 3D spatial information of plastic targets.

A novel ambiguity resolution model of BeiDou navigation satellite system/inertial navigation system tightly coupled for kinematic-to-kinematic precise relative positioning

The carrier-based kinematic-to-kinematic relative positioning can obtain the precise baseline between two moving stations, which greatly expands the application field of dynamic relative positioning. However, the relative positioning performance is degraded greatly with low fixation rate of ambiguity with low-cost receivers. Especially, in the complex dynamic environment, ambiguity resolution effect is influenced by the satellite signal blocked, multipath outlier, and abnormal state prediction. Aiming at the problems, a novel inertial navigation system–aided robust adaptive filtering ambiguity resolution model is proposed. In addition, a hierarchical filtering strategy is developed to eliminate ambiguity parameters in BeiDou navigation satellite system/inertial navigation system tightly coupled integrated system. Finally, the precise relative position can be calculated with the “best” ambiguity solution. Both experiments with static data and field vehicle test were carried out to evaluate the algorithm efficiency in different data configurations. The results indicate that IRAFAR-TCRP method can effectively suppress the influence of observation outliers and model prediction abnormalities, which improves the success rate of ambiguity resolution, raises the accuracy as well as the continuity of relative positioning. The success rate of ambiguity resolution with single-frequency BeiDou navigation satellite system can reach 90% in the gross error and abnormal disturbance environments and centimeter-level accuracy can be achieved.

SPH-ASR study of drop impact on a heated surface with consideration of inclined angle and evaporation

This paper studies the problem of drop impact on a heated surface by using a numerical method based on smoothed particle hydrodynamics with adaptive spatial resolution (SPH-ASR). The physical model considers the interaction and heat transfer between the liquid drop, solid wall and ambient gas, and the phase change between liquid and gas phases. The phase change process will change the particle mass and resolution. The SPH-ASR method is able to adaptively adjust the spatial resolution according to the distance to the interface between different phases. A series of numerical simulations were performed to investigate the effects of different factors on drop-wall interaction, including the drop diameter, impact velocity, liquid evaporation, wall temperature, and the inclined angle of wall. The comparison of impact regimes shows good agreement between the numerical and experimental results. The characteristics of drop impact on a heated surface were studied, particularly the drop spreading factor and mass evaporation ratio. The numerical results indicate that the maximum spreading factor and the mass evaporation ratio can be predicted as a function of dimensionless numbers.

2D rigorous coupled wave analysis with adaptive spatial resolution for a multilayer periodic structure.

We utilize the 2D modal solution of rigorous coupled wave analysis with adaptive spatial resolution to enhance the reliability of standard RCWA for multilayer gratings with metal-dielectric structures. The conversion relation in modal solutions between the Cartesian system and the transformed system is for the first time established. Based on the proposed conversion relation, the modal solution of the metal-dielectric structure obtained in the transformed system can match the boundary conditions with modal solutions of other different grating layers in the Cartesian system. Numerical results show that even for metal patches in microwave band, the above method can still achieve good convergence and is perfectly suitable for multi-layer structure calculation.