Fluid-based Model Research Articles

Optimization of Traffic Flow Using Computational Fluid Dynamics and AI Algorithms

The effective administration of urban activity may be a basic challenge in contemporary city arranging, driven by the got to diminish blockage, minimize travel time, and lower natural affect. This paper presents a novel approach to optimizing activity stream through the integration of Computational Fluid Dynamics (CFD) and Artificial Insights (AI) calculations. By leveraging CFD, we demonstrate activity as a liquid, permitting for the exact reenactment of activity elements beneath different conditions. This fluid-based modeling approach captures the complexities of vehicular development and intuitive in a more nuanced way than conventional activity recreation strategies. To upgrade the viability of our CFD models, we consolidate AI calculations, counting machine learning procedures such as fortification learning and neural systems. These AI calculations analyze expansive datasets of activity designs, anticipate blockage focuses, and propose ideal activity flag timings and routing strategies. The cooperative energy between CFD and AI encourages real-time versatile activity administration, empowering the framework to reply powerfully to changing activity conditions. Our approach is approved through broad recreations and real-world case thinks about in a major metropolitan zone. The comes about illustrate noteworthy enhancements in activity stream, decreased blockage, and lower emanations. Also, the versatile nature of the AI calculations guarantees persistent optimization as activity patterns evolve over time. This investigate contributes to the developing body of information in cleverly transportation frameworks, advertising a adaptable and vigorous arrangement for urban activity administration. The integration of CFD and AI presents a effective apparatus for city organizers and activity engineers, clearing the way for more brilliant, more maintainable urban portability arrangements. Future work will investigate the integration of extra information sources, such as IoT sensors and vehicle-to-infrastructure communications, to advance upgrade the system's prescient capabilities and responsiveness.

A novel fluid-based modeling approach using extended Hybrid Petri nets for power consumption monitoring in wireless autonomous IoT devices, with energy harvesting capability and triple sleeping strategy

A novel fluid-based modeling approach using extended Hybrid Petri nets for power consumption monitoring in wireless autonomous IoT devices, with energy harvesting capability and triple sleeping strategy

Numerical study of magnetic island coalescence using magnetohydrodynamics with adaptively embedded particle-in-cell model

Collisionless magnetic reconnection typically requires kinetic treatment that is, in general, computationally expensive compared to fluid-based models. In this study, we use the magnetohydrodynamics with an adaptively embedded particle-in-cell (MHD-AEPIC) model to study the interaction of two magnetic flux ropes. This innovative model embeds one or more adaptive PIC regions into a global MHD simulation domain such that the kinetic treatment is only applied in regions where the kinetic physics is prominent. We compare the simulation results among three cases: (1) MHD with adaptively embedded PIC regions, (2) MHD with statically (or fixed) embedded PIC regions, and (3) a full PIC simulation. The comparison yields good agreement when analyzing their reconnection rates and magnetic island separations as well as the ion pressure tensor elements and ion agyrotropy. In order to reach good agreement among the three cases, large adaptive PIC regions are needed within the MHD domain, which indicates that the magnetic island coalescence problem is highly kinetic in nature, where the coupling between the macro-scale MHD and micro-scale kinetic physics is important.

Study on the Influence of Tripping Operation on Annular Transient Surge-Swab Pressure of Herschel–Bulkley Fluid

Abstract The accurate prediction of transient surge-swab pressure, during the tripping operation under a narrow pressure window, is an important premise to ensure the safety of tripping operation and drilling. Different rheological modes of drilling fluid will have a great influence on the surge-swab pressure in wellbore, while the Herschel–Bulkley mode can simulate the rheological characteristics of actual drilling fluid in a better way. Therefore, the influence of drilling fluid flow friction under different rheological modes was mainly considered according to the transient flow model. Meanwhile, the influence of pumpage on transient surge-swab pressure during tripping operation was also considered with Herschel–Bulkley fluid-based tripping operation bottomhole transient surge-swab pressure calculation model established and model verification carried out. The following research results were obtained. First, compared with the Herschel–Bulkley mode, the power-law mode and Bingham mode will overestimate the flow friction of drilling fluid. Second, the surge-swab pressure peak values of different mud systems are water-based mud > polymer mud > oil-based mud. Third, the peak value of bottomhole transient surge-swab pressure increases with the increase of drilling fluid yield value, consistency coefficient, and flow behavior index, and the influence law is similar. Fourth, the tripping velocity and pumpage will directly affect the peak value and variation rule of bottomhole transient surge-swab pressure. Herschel–Bulkley fluid-based tripping operation bottomhole transient surge-swab pressure study helps control the surge-swab pressure during tripping operations and it is of great significance for lean, safe, and efficient drilling in narrow pressure window formations.

How sheath properties change with gas pressure: modeling and simulation

Particle-in-cell simulations are used to study how neutral pressure influences plasma properties at the sheath edge. The high rate of ion–neutral collisions at pressures above several mTorr are found to cause a decrease in the ion velocity at the sheath edge (collisional Bohm criterion), a decrease in the edge-to-center density ratio (h l factor), and an increase in the sheath width and sheath potential drop. A comparison with existing analytic models generally indicates favorable agreement, but with some distinctions. One is that models for the h l factor need to be made consistent with the collisional Bohm criterion. With this and similar corrections, a comprehensive fluid-based model of the plasma boundary transition is constructed that compares well with the simulation results.

Application of the Molecular Interaction Volume Model for Calculating Activities of Elements in Ferromanganese Alloys: Mn-C, Mn-Fe, Fe-C, and Mn-Fe-C Systems

The molecular interaction volume model (MIVM) developed by Tao is a fluid-based model derived from statistical thermodynamics and fluid phase equilibria. The MIVM was applied successfully to predict each element’s activity in Mn-based alloys, namely, Mn-C Mn-Fe, and Mn-Fe-C systems. The MIVM calculated binary parameters between metals (Fe, Mn) and nonmetal (C) in Mn-Fe-C alloys, confirming a strong interaction between Fe and Mn in Mn-Fe-C alloy. The MIVM indicated that iron has a great influence on the activity of Mn and little effect on the activity of carbon. A significant advantage of MIVM is its ability to explain the experimental phenomenon in the Mn-Fe-C ternary system, whereby the predicted values are in good agreement with the experimental data, showing that this model is reliable, convenient, and economic.

Estimating key traffic state parameters through parsimonious spatial queue models

As an active performance evaluation method, the fluid-based queueing model plays an important role in traffic flow modeling and traffic state estimation problems. A critical challenge in the application of traffic state estimation is how to utilize heterogeneous data sources in identifying key interpretable model parameters of freeway bottlenecks, such as queue discharge rates, system-level bottleneck-oriented arrival rates, and congestion duration. Inspired by Newell’s deterministic fluid approximation model, this paper proposes a spatial queue model for oversaturated traffic systems with time-dependent arrival rates. The oversaturated system dynamics can be described by parsimonious analytical formulations based on polynomial functional approximation for virtual arrival flow rates. With available flow, density and end-to-end travel time data along traffic bottlenecks, the proposed modeling framework for estimating the key traffic queueing state parameters is able to systematically map various measurements to the bottleneck-level dynamics and queue evolution process. The effectiveness of the developed method is demonstrated based on three case studies with empirical data in different metropolitan areas, including New York, Los Angeles, and Beijing.

수중 폭발에 의한 함체의 비탄성 휘핑 응답에 관한 연구

The primary effect of the far-field underwater explosion (UNDEX) is the whipping of the ship hull girder. This paper aims to verify why inelastic effects should be considered in the whipping response estimations from the UNDEX simulations. A navy ship was modeled using Timoshenko beam elements over the ship length uniformly keeping the constant midship section modulus. The transient UNDEX pressure was produced using two types of the Geers-Hunter doubly-asymptotic models: compressible and incompressible fluids. Because the UNDEX model based on incompressible fluid assumption provided more increased fluid volume acceleration in the bubble phase, the incompressible fluid-based UNDEX model was adopted for the inelastic whipping response analyses. The non-linear hull girder bending moment-curvature curve was used to embed inelastic effects in the UNDEX analyses where the Smith method was applied to derive the non-linear stiffness. We assumed two stand-off distances to see more apparent inelastic effects: 40.5 m and 35.5 m. In the case of the 35.5 m stand-off distance, there was a statistically significant inelastic effect in terms of the average of peak moments and the average exceeding proportional limit moments. For the conservative design of a naval ship under UNDEX, it is recommended to use incompressible fluid. In the viewpoint of cost-effective naval ship design, the inelastic effects should be taken into account.

Differences in the thermal properties and surface temperature of prehospital antihypothermia devices: an in vitro study

BackgroundPreventing and treating hypothermia in prehospital settings is crucial. Several products have been developed to prevent heat loss and actively warm patients in prehospital settings. We compared the efficacy and...

Analytical characterization of multi-state effective discharge rates for bus-only lane conversion scheduling problem

An accurate quantification of traffic flow characteristics with and without bus-only lane is important for determining transit priority strategies. Examinations of real-world vehicle trajectory data, like those from the NGSIM dataset, found that an effective discharge rate may be discounted when merging or lane-changing behaviors are observed. To deal with this, this manuscript analytically derives the effective discharge rate of a roadway segment by considering multi-stage merging behavior and vehicular traffic kinematics near a side entrance, for optimal bus-only lane conversion. The classic fluid-based approximation model by Newell that characterizes the queuing and dissipation process is extended to a multi-state queuing analysis framework. Three effective discharge rate discount factors are explicitly derived, for bus-only lane, general-purpose lane, and mixed-traffic lane, respectively. The derived effective discharge rates are represented by mathematically-simple expressions in a closed-form, and correctly account for the effects of demand inputs, such as arrival rate and the ratio of vehicles of different types, vehicular performance (such as acceleration rate), and traffic flow characteristics (such as backward wave speed and jam density). The bus-only lane conversion scheduling problem is then formulated as an optimization model to minimize total traffic delay. Validation, using NGSIM data, showed that our model reduced the effective discharge rate estimation error significantly on both arterials and freeways. Sensitivity analysis revealed that the optimal bus-only lane scheduling time varied in response to traffic demand and vehicle ratios, and the developed optimization model was always beneficial when compared with the demand-oriented strategy.

Transient non-classical transport in the hollow cathode plume II: evaluation of models for the anomalous collision frequency

The ability of fluid-based closure models to describe the non-classical electron collision frequency in the plume of a hollow cathode is experimentally investigated. Six models—all predicated on the assumption that the non-classical collision frequency can be attributed to ion acoustic turbulence (IAT)—are considered. Experimental measurements of the time-resolved plasma properties in the cathode plume (Georgin M P, Jorns B A and Gallimore A D 2020 PlasmaSources Sci. Technol, 29 105010) are used to evaluate each closure model and compare it to experimental measurements of the effective electron collision frequency. Though more than one of the considered closures can predict the time-average behavior of the plasma in the cathode plume, it is found that only one model accurately predicts the measurements in both space and time for the cathode and operating conditions that were studied. This new highest fidelity model is derived using a single-equation approach based on modeling the average frequency of the IAT as it evolves in space and time. The implications of the success of this model are discussed in the context of the understanding of the dynamics of the IAT in the cathode plume as well as on-going fluid-based modeling efforts related to cathode plumes.

Longitudinal structure and plasma parameters of an entire DC glow discharge as obtained using a 1D fluid-based model with non-local ionization

We present a model of a direct-current glow discharge that self-consistently reproduces its full longitudinal structure and provides reliable estimates of main discharge parameters in all of its regions. The model is based on the fluid description of ions and bulk electrons and incorporates analytical formulation of non-local ionization and excitation sources induced by fast electrons. Spatial distributions of main discharge parameters obtained for the case of an extended glass tube filled with argon at 0.5 Torr show pronounced near-cathode regions—the cathode sheath, the negative glow and the Faraday dark space—as well as the autonomous positive column and the anode sheath. Formation of the second electric field reversal and the transitional region between the Faraday dark space and the positive column are revealed. This transitional region occupies a considerable fraction of the discharge tube length, over which the bulk electron temperature increases by more than an order of magnitude. Comparison of simulation results with those obtained with a 2D fluid model with the local energy approximation, as well as with experimental data taken from literature is presented. The model can be realised in most modern low-temperature plasma simulation software. The underlying physics and assumptions are discussed in detail.

Optimal Information Centric Caching in 5G Device-to-Device Communications

Device-to-Device (D2D) communications are a prominent feature of 5G systems, introduced to provide a native support to distributed services in mobile environments. D2D technologies enable straight interactions between mobile terminals without a compulsory involvement of base stations. In this manuscript, we study and propose an optimized caching strategy to content distribution on top of D2D technology, based on Information Centric Networking (ICN) principles. The rationale is that ICN architectures can provide seamless support to mobile services and decouple contents from node identifiers, thus providing a promising match with D2D requirements. To this end, a novel fluid-based model in proposed hereby that catches the interplay between ICN functionalities, D2D requirements, and 5G specifications. Then, based on this model, an optimal content replication problem is formulated, encompassing caching overhead and system load. Additionally, this problem is thoroughly analyzed to prove that it has an optimal solution with time threshold form. A practical algorithm $\varsigma ^*$ -OCP is further proposed in order to implement the optimal caching control in realistic environments. Finally, a massive simulation campaign is carried out to test the proposed algorithm in comparison to state-of-the-art solutions.

Elasto-acoustic response damping performance of a smart cavity-coupled electro-rheological fluid sandwich panel

The transient vibroacoustic response mitigation of a rectangular sandwich panel with an adaptive electro-rheological fluid core layer, and backed by a hard-walled reverberant rectangular parallelepiped acoustic enclosure, is investigated. The problem is analyzed in a multidisciplinary framework that involves the thin sandwich electro-rheological fluid-based plate model, the 3D wave equation for the acoustic enclosure domain, the first-order Kelvin–Voigt viscoelastic model for the electro-rheological fluid core material, the pertinent structure–fluid compatibility relation, and the inherently robust sliding mode control strategy. The generalized Fourier expansion method is utilized to set up the fully coupled system equations in the state–space domain, and the fourth-order Runge-Kutta time marching technique is then utilized to compute both uncontrolled and controlled coupled system responses in three basic external loading configurations. It is found that increasing the cavity depth has a substantial restraining effect on the overall sound pressure response levels, while the electro-rheological fluid-panel displacement response amplitudes experience only moderate reductions. Also, a purely passive electro-rheological fluid-based system is observed not to be very effective for vibroacoustic response suppression of the cavity-coupled structural system, while the overall success of the applied sliding mode control methodology in reasonable reduction of both panel displacement and sound pressure time response amplitudes is demonstrated. Furthermore, the control system authority with regard to the acoustic cavity pressure (panel displacement) is found to moderately (slightly) decrease as the cavity depth increases. Limiting cases are considered and accuracy of the suggested analytical model is checked against the output of an FEM package as well as with the accessible literature results. Moreover, the main components of a prospective experimental platform for verifying the performance of proposed vibroacoustic control system are briefly described.

Numerical Simulation of Evaporating Two-Phase Flow in a High-Aspect-Ratio Microchannel with Bends

Despite the demand for high-performance, two-phase cooling systems, high-fidelity simulations of flow boiling in complex microchannel geometries remains a challenging numerical problem. We conduct a first-principles-based simulation of an evaporating two-phase flow in a high-aspect-ratio microchannel with bends using a volume of fluid-based numerical model. For the case shown, the lower horizontal section of the microchannel has a constant flux of 20 W/cm2 applied to the wetted wall area (heat flux at the base of 133 W/cm2); HFE-7100 vapor and liquid enter the channel at 2 m/s. The three-dimensional channel geometry requires a refined near-wall numerical mesh to resolve thin liquid film flow features. The recently developed saturated-interface-volume phase change model (Int J Heat Mass Trans 93:945-956, 2016) is implemented for prediction of mass and energy exchange across the liquid-vapor interface at a low computational cost (~80 hr; 6-core parallelization on Intel Xeon E3-1245V3). The model reveals transport details including the interface shape and fluid velocity and temperature fields. The interfacial temperature remains fixed at saturation with smooth velocity contours near the interface. The highest evaporation flux is located in the thin liquid film region near the heated wall.

Blood-based and urinary prostate cancer biomarkers: a review and comparison of novel biomarkers for detection and treatment decisions.

The diagnosis of prostate cancer (PCa) is currently based on serum PSA testing and/or abnormal digital rectal examination and histopathologic evaluation of prostate biopsies. The main drawback of PSA testing is the lack of specificity for PCa. To improve early detection of PCa more specific biomarkers are needed. In the past few years, many new promising biomarkers have been identified; however, to date, only a few have reached clinical practice. In this review, we discuss new blood-based and urinary biomarker models that are promising for usage in PCa detection, follow-up and treatment decision-making. These include Prostate Health Index (PHI), prostate cancer antigen 3 (PCA3), four-kallikrein panel (4K), transmembrane protease serine 2-ERG (TMPRSS2-ERG), ExoDx Prostate Intelliscore, SelectMDx and the Mi-Prostate score. Only few head-to-head studies are available for these new fluid-based biomarkers and/or models. The blood-based PHI and urinary PCA3 are two US Food and Drug Administration-approved biomarkers for diagnosis of PCa. In the second part of this review, we give an overview of published studies comparing these two available biomarkers for prediction of (1) PCa upon prostate biopsy, (2) pathological features in radical prostatectomy specimen and (3) significant PCa in patients eligible for active surveillance. Studies show opposing results in comparison of PHI with PCA3 for prediction of PCa upon initial and repeat prostate biopsy. PHI and PCA3 are able to predict pathological findings on radical prostatectomy specimen, such as tumor volume and Gleason score. Only PHI could predict seminal vesicle invasion and only PCA3 could predict multifocality. There is some evidence that PHI outperforms PCA3 in predicting significant PCa in an active surveillance population. Future research should focus on independent validation of promising fluid-based biomarkers/models, and prospective comparison of biomarkers with each other.

A multi-species 13-moment model for moderately collisional plasmas

Fluid-based models of collisional transport in multi-species plasmas have typically been applied to parameter regimes where a local thermal equilibrium is assumed. While this parameter regime is valid for low temperature and/or high density applications, it begins to fail as plasmas enter the collisionless regime and kinetic effects dominate the physics. A plasma model is presented that lays the foundation for extending the validity of the collisional fluid regime using an anisotropic 13-moment fluid model derived from the Pearson type-IV probability distribution. The model explicitly evolves the pressure tensor and heat flux vector along with the density and flow velocity to capture dynamics usually restricted to kinetic models. Each particle species is modeled individually and collectively coupled through electromagnetic and collisional interactions.

Volume of fluid-based numerical modeling of condensation heat transfer and fluid flow characteristics in microchannels

The present work proposes a numerical model for the simulation of condensation heat transfer and fluid flow characteristics in a single microchannel. The model was based on the volume of fluid approach, which governed the hydrodynamics of the two-phase flow. The condensation characteristics were governed by the physics of the phenomena and did not include any empirical expressions in the formulation. The conventional governing equations for conservation of volume fraction and energy were modified to include source terms that accounted for the mass transfer at the liquid–vapor interface and the associated release of latent heat, respectively. A microchannel having characteristic dimension of 100μm was modeled using a two-dimensional computational domain. The working fluid was R134a and the vapor mass flux at the channel inlet ranged from 245 to 615kg/m2s. The channel wall was maintained at a constant heat flux ranging from 200 to 800kW/m2. The predictive accuracy of the numerical model was assessed by comparing the two-phase frictional pressure drop and Nusselt number with available empirical correlations in the literature. A reasonably good agreement was obtained for both parameters with a mean absolute error of 8.1% for two-phase frictional pressure drop against a recent universal predictive approach, and 16.6% for Nusselt number against an available correlation. Further, a qualitative comparison of various flow patterns against experimental visualization data also indicated a favorable agreement.

Demonstration of Anisotropic Fluid Closure Capturing the Kinetic Structure of Magnetic Reconnection

Collisionless magnetic reconnection in high-temperature plasmas has been widely studied through fluid-based models. Here, we present results of fluid simulation implementing new equations of state for guide-field reconnection. The new fluid closure accurately accounts for the anisotropic electron pressure that builds in the reconnection region due to electric and magnetic trapping of electrons. In contrast to previous fluid models, our fluid simulation reproduces the detailed reconnection region as observed in fully kinetic simulations. We hereby demonstrate that the new fluid closure self-consistently captures all the physics relevant to the structure of the reconnection region, providing a gateway to a renewed and deeper theoretical understanding of reconnection in weakly collisional regimes.

Broadband propagation and photoacoustic time reversal imaging using k-space methods

Numerical, time domain, models of broadband acoustic propagation using k-space methods will be described and applied to the problem of image reconstruction in photoacoustic imaging. k-space methods are a subset of time-stepping pseudospectral methods, which use FFTs to calculate field gradients, with an additional correction to make the solutions exact in the homogeneous case. Furthermore, they are closely related to a number of methods in the mathematical, engineering and physical sciences literature, including non-standard finite difference schemes, exponential integrators, wavenumber domain reverse time migration, and wave propagator models developed to solve the time-dependent Schroedinger equation. These connections will be discussed and used to illuminate the advantages of the k-space approach for large scale modelling of broadband acoustic waves. To illustrate the method, a fluid-based k-space model will be applied to the inverse acoustic initial value problem encountered in tomographic photoacoustic imaging. It is well known that this can be solved, in the linear case, using a time-reversed numerical model. Extensions from this basic case to absorbing and non-linear media will be explored.