Dual Grid Research Articles

Preparation and performance evaluation of heat resistant and salt resistant anionic fluid loss reducer for water‐based drilling fluid

AbstractIn this investigation, a new micro‐crosslinked anionic polymer resistant to elevated temperature and high salinity, PKDASN, was synthesized using 3‐chloropropyltriethoxysilane (KMB703), N, N‐Dimethylacrylamide (DMAM), 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS), N‐vinyl caprolactam (NVCL), and sodium (4‐vinyl phenyl)methanesulfonate (SVM) employing free radical polymerization in a water‐based solution. The structure of PKDASN was analyzed using Fourier‐transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and X‐ray photoelectron spectroscopy, while its microstructure was analyzed using scanning electron microscopy. Thermogravimetric analysis showed that the pyrolysis temperature of PKDASN was above 294°C. Adding KMB703 enables the polymer to form a dense and stable spatial network. This intensified polymer network could interact with bentonite via intermolecular force and Coulomb force and form a dual grid structure, which presents impressive stability and control of filtration in saltwater. This is mainly achieved through creating a “silane coupling layer” on the particle surface by KMB703, which facilitates the crosslinking and aggregation of the polymer, thereby reinforcing the polymer's framework. This implies that under high‐temperature conditions of 230°C, 3 wt% PKDASN can improve the filtration effectiveness of drilling fluids and exhibit resistance to 15 wt% NaCl contamination. American Petroleum Institute filtration(FLAPI) and High temperature and high pressure filtration(FLHTHP) values were 4.6 and 23.0 mL, respectively. Therefore, this investigation provides a novel approach to utilizing the designated silane agent for the advancement of filtration loss additives in drilling fluids resistant to elevated temperature and high salinity.

Dual grid energy management strategy for electric vehicles in hybrid microgrid utilizing matrix pencil method

Abstract This study introduces a cutting-edge Matrix Pencil-based Dual Grid Energy Management System (MP-DEMS) aimed at seamlessly integrating electric vehicles (EVs) into power grids while enhancing power quality (PQ) and reliability (PR). Operating within an AC-DC hybrid microgrid (HMG) framework, the MP-DEMS reduces the necessity for additional conversion devices, simplifying the integration of EVs and batteries. The core of the proposed DEMS comprises three key modules: the Wind Energy Management Module (WEMS), Smart Storage and EV Power Coordination (SS-EVPC), and Coordinated Power Conversion Control (CPCC). These modules work together to optimize energy usage, leverage renewable sources effectively, and manage EV charging/discharging schedules to minimize grid impact. An innovative aspect of the MP-DEMS is its use of Matrix Pencil-based techniques, offering several advantages over traditional Discrete Fourier Transform (DFT) methods. These advantages include swift dynamic response, resilience to voltage variations, and precise voltage phase estimation. Software simulations and Hardware-in-the-Loop (HIL-402) testing validate the efficacy of the MP-DEMS approach, showcasing enhanced power transfer capabilities, improved harmonic performance, and superior voltage/frequency regulation within EV-HMS applications. Overall, the MP-DEMS presents a promising solution for advancing the integration of EVs into microgrid systems, contributing to a more sustainable and reliable energy future.

Solar shunt active power filter based on optimized direct power control strategy with disturbance rejection principle

Introduction. This paper focuses on a renewable energy system coupled to a dual purpose power grid via a parallel active power filter for injecting photovoltaic energy into the grid and improving the power quality in the presence of the non-linear load. The novelty of the work consists in the combination of two advanced techniques – Fuzzy Logic Controller (FLC) and the optimized Anti-Windup Fractional Order Proportional-Integral Differentiator (AW-FOPID) regulator based on Particle Swarm Optimization with the Spreading Factor (PSO-SF) algorithm, applied to the improved Direct Power Control (DPC) strategy under different conditions related to climate changes and healthy or infected electrical network. Purpose. Its main role is to improve the power quality and reject the perturbations deforming the electrical network under distorted, unbalanced and balanced grid voltage conditions. Besides, the FLC is employed the Maximum Power Point Tracking (MPPT) under any weather conditions. In addition, the optimized AW-FOPID controller leads to keep the DC bus voltage at its reference value with small undershoots and overshoots in the voltage with a short response time in steady or dynamic states. Methods. The rejection of disturbances affecting the grid is offered by the improved DPC. On the other hand, an intelligent method based on fuzzy logic was used MPPT under any weather conditions. Furthermore, an AW-FOPID regulator based on PSO-SF algorithm is used to keep the DC bus voltage at its reference value with small undershoots and overshoots in the voltage, while keeping a fast response time. Results. The proposed system control is evaluated in various states of power source: distorted, unbalanced, and balanced by simulation using MATLAB/Simulink. The simulation results illustrate the effectiveness and performance of the studied control strategies. References 26, tables 8, figures 16.

A dual grid-based deep reinforcement learning and computational fluid dynamics method for flow control and its application to nucleate pool boiling

This paper presents a proposition of a dual grid (DG)-based coupled deep reinforcement learning (DRL) and computational fluid dynamics (CFD) method for active flow control. The DG-DRL-CFD method uses a dual-resolution grid, with a coarser grid for the training phase and a finer grid for the testing phase of the DRL-CFD method. Further, after a validation study for our DRL-CFD-based parallelized in-house solvers, this paper presents a performance study for a periodic suction/ejection-based drag reduction for a cylinder in a channel-confined flow. Using an immersed boundary method for CFD on a Cartesian grid, this novel DG-DRL-CFD method is shown to result in almost same accuracy (within 1%) in a substantially reduced computational time as compared to the traditional DRL-CFD method (on the finer uniform grid). Finally, using a sharp interface level set method for an axisymmetric two-phase flow, this paper presents an application of the DR-DRL-CFD method for an oscillating base plate-based enhancement of heat transfer during nucleate pool boiling. As compared to our recent CFD study-based parametric study for the nucleate pool boiling problem, the present DG-DRL-CFD method leads to a profile and frequency of plate-oscillation that results in a larger value of average Nusselt number Nuavg for the plate. The coupled DRL-CFD method leads to plate oscillation profile giving higher enhancement in Nuavg, compared to an open-loop control strategy that involves a parametric sweep involving multiple simulations.

On development of lattice-Boltzmann method based multi phase flow solver

A numerical methodology based on lattice Boltzmann and level set function is presented to simulate the two-phase flows with stringent density and viscosity ratio. Two different strategies - single grid (SGLBLS) and dual grid (DGLBLS) are used. For accurate computation of interfacial forces in DGLBLS, the level set equations are solved on a uniform grid which is twice that for lattice-Boltzmann equations. The code validation and performance of SGLBLS and DGLBLS is carried on three different problems: Young’s Laplace law, 2D rising bubble and Rayleigh–Taylor instability. The results show that the representation of the interface is more accurate in DGLBLS with significantly less mass error - establishing it as an accurate method to handle stringent density and viscosity ratio. The comparison between DGLBLS and SGLBLS shows that the DGLBLS leads to a large improvement in the accuracy of the results with only slight increase in the computational cost.

Intelligent path planning by an improved RRT algorithm with dual grid map

This research addresses the limitations of existing autonomous vehicle path planning algorithms, notably their slow processing speeds and suboptimal route efficiency. We introduce an innovative path planning algorithm that synergizes the A* algorithm with the Rapidly-exploring Random Tree (RRT) approach. This hybrid model significantly enhances route timeliness and reliability, particularly in obstacle avoidance scenarios for driverless vehicles. Our methodology employs a 'two-level map' approach, where a lower-resolution grid map is derived from a high-resolution map. Utilizing the A* algorithm on this framework, we ascertain a preliminary 'coarse path' for the navigation target. The RRT algorithm, modified to reduce the traditional redundancy associated with random uniform sampling, is then applied for probabilistic sampling within this defined area. ovel aspect of our approach is the simultaneous generation of two trees, originating from both the start and end points, guided by a target-biased strategy and dual-direction theory. This method probabilistically expands towards the node of the opposite tree, thereby enhancing both the generation speed and trajectory viability. Further refinements are made through a pruning process, optimizing the path, and employing Bezier curves for smoothing, ensuring compliance with the dynamic constraints of Ackerman chassis vehicles. Comparative analysis in complex environments demonstrates the superiority of our proposed algorithm. It outperforms traditional methods with a 400 % increase in planning speed relative to the RRT-Connect algorithm, and a 30 % reduction in average path length. Additionally, the mean curvature of routes generated by our algorithm is 19 % lower than traditional routes, underscoring significant advancements in both the timeliness and viability of the planned routes.

Smooth Operation Changeover Scheme for Dual Stage BES-SPVA Grid Coupled System

Smooth Operation Changeover Scheme for Dual Stage BES-SPVA Grid Coupled System

Two-grid finite element method with an H2N2 interpolation for two-dimensional nonlinear fractional multi-term mixed sub-diffusion and diffusion wave equation

<abstract><p>In this paper, we studied the two-grid method (TGM) for two-dimensional nonlinear time fractional multi-term mixed sub-diffusion and diffusion wave equation. A fully discrete scheme with the quadratic Hermite and Newton interpolation (H2N2) method was considered in the temporal direction and the expanded finite element method is used to approximate the spatial direction. In order to reduce computational time, a dual grid method based on Newton iteration was constructed with order $ \alpha\in(0, 1) $ and $ \beta\in(1, 2) $. The global convergence order of the two-grid scheme reaches $ O(\tau^{3-\beta}+h^{r+1}+H^{2r+2}) $, where $ \tau $, $ H $ and $ h $ are the time step size, coarse grid mesh size and fine grid mesh size, respectively. The error estimation and stability of the fully discrete scheme were derived. Theoretical analysis shows that the two grid algorithms maintain asymptotic optimal accuracy while saving computational costs. In addition, numerical experiments further confirmed the theoretical results.</p></abstract>

Dual Grid-Forming Control With Energy Regulation Capability of MMC-HVDC System Integrating Offshore Wind Farms and Weak Grids

To integrate weak onshore grids, some grid forming (GFM) control schemes taking advantage of DC voltage synchronization have been proposed for modular multilevel converter-based high-voltage direct current (MMC-HVDC) systems. In these control schemes, the sub-module (SM) capacitor energy is only used for grid synchronization. Since the SM capacitor is an energy storage device, it has the potential to actively regulate the stored energy. To fully exploit the energy management capability of MMC, a dual grid forming control scheme with energy regulation capability is presented in this paper. The proposed control scheme enables grid forming for both onshore and offshore MMC stations. Meanwhile, the capacitor energy of MMCs can be flexibly regulated to provide frequency support for the onshore grid. To verify the effectiveness of the proposed control scheme, case studies are first carried out in a point-to-point offshore wind farms (OWFs) integrated HVDC system. In addition, the frequency support performance is evaluated in a 3-area 4-machine grid integrated with two OWFs-HVDC systems. Finally, a single-terminal three-phase MMC prototype is developed to test the voltage decoupling and energy management capabilities of the proposed control strategy.

Evolution and interaction relationship of "eco-economy" dual grid pattern in Lingwu City, Ningxia, China.

Strengthening ecological network construction is an important measure to improve urban ecological environment and protect biodiversity. With Lingwu City of Ningxia as an example, based on remote sensing and social and economic data, we comprehensively analyzed the "double network" (ecological network and social and economic landscape) pattern and their relationship by using morphological spatial pattern analysis, Linkage Mapper, and improved gravity model. The results showed that land use/cover changed dramatically from 2000 to 2020 in Lingwu City. The area of sandy land and grassland decreased sharply, that of forest and construction land increased, and industrial zones expanded rapidly. The connectivity and stability of "dual network" were improved. The intensive areas of human activities were distributed in urban area, oasis agricultural areas, and Ningdong energy industrial zone. The ecological source areas and ecological corridors were mainly distributed in the middle of the nature reserve, while some extended to the other three functional areas. The transportation corridor presented an "H" pattern that was dense in oasis agricultural area and Ningdong energy industrial zone, and connected between the two regions. The "double network" were centered around their respective functional area spaces and had interwoven distributions. The trend of the "double network" changed from conflict to coordinated situation, with obvious zoning and interaction in space. The oasis agricultural area and Ningdong energy industrial area destroyed the eco-logy in the early stage and improved that in the later stage. In the future, it is necessary to strengthen the coordination between ecological protection and social and economic development, which could improve ecological quality by combining measures such as improving the quality of ecological sources and corridors, constructing ecological nodes, and repairing ecological disturbance points.

Multi-disciplinary characterization of shrinkage effects in Opalinus clay

Multi-disciplinary characterization of shrinkage effects in Opalinus clay

MoMusic: A Motion-Driven Human-AI Collaborative Music Composition and Performing System

The significant development of artificial neural network architectures has facilitated the increasing adoption of automated music composition models over the past few years. However, most existing systems feature algorithmic generative structures based on hard code and predefined rules, generally excluding interactive or improvised behaviors. We propose a motion based music system, MoMusic, as a AI real time music generation system. MoMusic features a partially randomized harmonic sequencing model based on a probabilistic analysis of tonal chord progressions, mathematically abstracted through musical set theory. This model is presented against a dual dimension grid that produces resulting sounds through a posture recognition mechanism. A camera captures the users' fingers' movement and trajectories, creating coherent, partially improvised harmonic progressions. MoMusic integrates several timbrical registers, from traditional classical instruments such as the piano to a new ''human voice instrument'' created using a voice conversion technique. Our research demonstrates MoMusic's interactiveness, ability to inspire musicians, and ability to generate coherent musical material with various timbrical registers. MoMusic's capabilities could be easily expanded to incorporate different forms of posture controlled timbrical transformation, rhythmic transformation, dynamic transformation, or even digital sound processing techniques.

Simulations of debris flow impacting on bridge pier based on coupled CFD-DEM method

In many recorded natural disasters, the floating debris was observed to contribute a lot to the destructive power of violent water against structures. To explore the impacting effects acting on the bridge pier from a debris flow in a tsunami disaster, a three-phase numerical model is used based on a Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) coupling method. The Navier-Stokes equations are adopted to describe the fluid behaviors with the Volume of Fluid (VOF) method to track the free surface, and a virtual dual grid porosity model is adopted to calculate the fluid porosity. The particles are computed by the Newton's laws and contact laws. The simulated results of single particle sedimentation, single particle floating in dam-break flow, and the settling of particles with different diameters agree well with the literature, which validate this model. The model was then employed to investigate the fluid flow with the floating particles colliding with the bridge pier using dam-break flow to simulate the tsunami bore. The results show the impacting load from the debris flow acting on the bridge pier is 295% larger than the impacting load from the flow without debris, and expose the impacting procedure.

A numerical study on breakup of a liquid jet in an axial electric field

A liquid jet injected from a nozzle stretches in the direction of the applied electric field and subsequently emits multiple droplets on pinch-off. It is hypothesized that the size and frequency of the drops can be manipulated by varying the electric field strength and flow rate, which is essential in electrohydrodynamic jet printing. Numerical simulations of the electrified jet breakup are performed using an in-house code based on the Dual Grid Level Set Method. To comprehend the impact of the electric and hydrodynamic forces, three dimensionless parameters are introduced: injection velocity (0.01≤Vinj≤0.15), Reynolds number (10≤Re≤100) and electric Bond number (0≤Boe≤30).Our results indicate the transition from dripping to micro-dripping and micro-jetting (at high Vinj) with increasing Boe. The critical Boe, at which this transition occurs, is found to escalate with an increase in Re. The stability of the micro-dripping mode is characterized by the balancing of the electrical and viscous shear stresses. Although the influence of the electric Bond number on the jet breakup length is marginal, it has a significant effect on the droplet diameter and formation frequency. A re-formulated scaling law suggests that the jet breakup length is mainly affected by injection velocity and Reynolds number.

Digital geometry on a cubic stair-case mesh

• The cubic grid Z 3 plays important role in the (digital) world. • Meshes obtained by cutting Z 3 by oblique planes can display 2d images. • The dual semi-regular grid, the rhombille tiling is an oblique cubic mesh. • Shortest path algorithm and digital distance are computed on the rhombille tiling. • The rhombille tiling can be used as a digital canvas and for RGB pixel geometry. In this paper, we investigate digital geometry on the rhombille tiling, D(6,3,6,3), that is the dual of the semi-regular tiling called hexadeltille T(6,3,6,3) tiling and also known as trihexagonal tiling. In fact, this tiling can be seen as an oblique mesh of the cubic grid giving practical importance to this specific grid both in image processing and graphics. The properties of the coordinate systems used to address the tiles are playing crucial roles in the simplicity of various algorithms and mathematical formulae of digital geometry that allow to work on the grid in image processing, image analysis and computer graphics, thus we present a symmetric coordinate system. This coordinate system has a strong relation to topological/combinatorial coordinate system of the cubic grid. It is an interesting fact that greedy shortest path algorithm may not be used on this grid, despite to this, we present algorithm to provide a minimal-length path between each pair of tiles, where paths are defined as sequences of neighbor tiles (those are considered to be neighbors which share a side). We also prove closed formula for computing the digital, i.e., path-based distance, the length (the number of steps) of a/the shortest path(s). Some example pictures on this grid are also presented, as well as its possible application as pixel geometry for color images and videos on the hexagonal grid. To create your abstract, type over the instructions in the template box below. Fonts or abstract dimensions should not be changed or altered.

Adaptive mesh axi-symmetric simulation of droplet impact with a spherical particle in mid-air

In this study, droplet-particle collisions in mid-air are numerically investigated for a wide range of collision parameters: Weber number, contact angle and droplet/particle diameter ratio (4 ≤ We ≤ 150, 20° ≤ θeqi ≤ 160°, and Ω = 1/2 and 1). To perform these simulations in an efficient manner, a simple dual grid based adaptive mesh refinement (SDG AMR) strategy is proposed and implemented in our existing multiphase flow solver. A total of 90 collision cases are systematically analyzed and are compared with results for the case of impact on a stationary particle to understand how mid-air collision characteristics are changed relative to those on a stationary target. The simulation results show that mid-air droplet-particle collision behavior is significantly different from that of droplet collision on a stationary particle, thus the impact phenomena cannot be interpreted by extrapolating collision results for a stationary target.

Analysis of a finite volume element scheme for solving the model two-phase nonequilibrium flow problem

The paper proposes a hybrid numerical method for solving a model problem of two-phase nonequilibrium flow of an incompressible fluid in a porous medium. This problem is relevant in the modern theory of the motion of multiphase fluids in porous media and has many applications. The studied model is based on the assumption that the relative phase permeabilities and capillary pressure depend not only on saturation, but also on its time derivative. The saturation equation in this problem refers to the type of convection-diffusion with a predominance of convection, which also includes a third-order term to account for the nonequilibrium effects. Due to the hyperbolic nature of the equation, its solution is accompanied by a number of difficulties that lead to the need for an appropriate choice of the solution method. In contrast to previous works, this paper uses a finite volume element method for solving the problem, the construction of which is based on integral balance equations, and an approximate solution is chosen from the finite element space. To discretize the problem, two different dual grids are used based on the main triangulation. In this paper, a number of a priori estimates are obtained which yields the unconditional stability of the scheme as well as its convergence with the second order. The advantages of the approach used include the local conservatism of the scheme, as well as the comparative simplicity of the software implementation of the method. These results are confirmed by a numerical test carried out on the example of a model problem.

Computational multifluid-structure interaction study on nucleate boiling under the effect of stationary or oscillating torus

The present numerical study characterizes nucleate boiling heat transfer in ethanol from a single nucleation site on a horizontal base plate in the presence of a fluid-immersed solid copper torus. The torus lies above the base plate, with its axis centered along the nucleation site, and it is either kept stationary or subjected to forced oscillations in the vertical direction. A sharp-interface dual grid Level Set method (SI-DGLSM)-based in-house solver is used here, in which a Level Set-based Immersed Boundary Method (LSIBM) is used to impose the boundary condition at the moving solid-fluid interfaces. For nucleate boiling in the presence of a stationary torus, enhancement in Nusselt number is observed due to thinning of the thermal boundary layer under the torus and thickening of the thermal boundary layer near the bubble. In the presence of torus oscillations, a lock-on regime is observed at optimal actuation parameters, for which the frequency of bubble departure synchronizes with the actuation frequency of the torus. A significant increase in Nusselt number is observed within the lock-on regime due to active pumping of superheated liquid towards the nucleating bubble during bubble growth. Analysis of heat flux partitioning shows that the enhancement in Nusselt number may be mainly attributed to higher sensible heat flux in the presence of torus oscillations, especially near the lock-on regime. This work demonstrates a novel way for enhancing heat transfer in the single-bubble nucleate boiling regime via externally actuated solid objects immersed in the liquid.

GCCP - NS: Grid based Congestion Control protocol with N-Sinks in a Wireless Sensor Network

Wireless Sensor Networks (WSN) have been a current trend in the research field and has many issues when there are multiple mobile sinks. Data dissemination gets critical as their locations have to be repeatedly updated and results in huge consumption of the restricted battery supply in sensor nodes. In this paper, we propose GCCP – NS, a grid based congestion control protocol with N –sinks that solves the data dissemination problem leading to congestion. We construct a dual level grid structure to trail the locations of all the source nodes that reports the information to the mobile sinks by monitoring the network in a hierarchical manner. As an added advantage, it aids in data dissemination based on query flooding from the mobile sinks using quorum based method within each cell in the grid and avoids congestion in an effective manner. Simulation results show that our proposed protocol outperforms the other schemes in terms of packet delivery ratio, energy expenditure and throughput.

A class of finite element methods with averaging techniques for solving the three-dimensional drift-diffusion model in semiconductor device simulations

Obtaining a satisfactory numerical solution of the classical three-dimensional drift-diffusion (DD) model, widely used in semiconductor device simulations, is still challenging nowadays, especially when the convection dominates the diffusion. In this work, we propose a series of finite element schemes with different types of averaging techniques to discretize the three-dimensional continuity equations. Our methods are based on the classical finite element framework, quite different from those mixed finite element/volume methods that also employ inverse averaging techniques. At first, the Slotboom variables are employed to transform the continuity equations into self-adjoint second-order elliptic equations with exponentially behaved coefficients. Then four averaging techniques, denoted with A1-A4, are introduced to approximate the exponential coefficient with its average on every tetrahedral element of the grid. The first scheme calculates the harmonic average of the exponential coefficient on a whole tetrahedron, and the other three schemes calculate the average of the exponential coefficient on each edge of a tetrahedral element. Our methods can avoid the spurious non-physical numerical oscillations and guarantee the conservation of the computed terminal currents with a terminal current evaluation approach. In fact, these methods not only maintain numerical stability but also overcome the disadvantages of some stabilization methods that cannot guarantee the conservation of the terminal currents, such as the streamline-upwind Petrov-Galerkin (SUPG) method. Moreover, the derivation of these discretization methods does not need the dual Voronoi grid as that of the finite volume Scharfetter-Gummel (FVSG) method or other mixed finite element/volume methods with inverse averaging techniques, which greatly reduces the complexity of parallel implementations of our methods. Simulations on two realistic three-dimensional semiconductor devices are carried out to test the accuracy and stability of our methods. According to numerical results, we conclude that scheme A4 can produce more accurate numerical solutions than the other three schemes, especially when the bias applied on the electrode is high. Numerical results also show that the scheme A4 is more robust than the Zlámal finite element method [1] in high-bias cases, and it also performs better than the FVSG method and a tetrahedral mixed finite element method [2] on poor-quality grids. Scheme A4 is also employed to study rich physical properties of the n-channel MOSFET.