Fluid Dynamic Processes Research Articles

Coupling immersed boundary method with wall function for high Reynolds number compressible flows on adaptive Cartesian grids

In this paper, a high Reynolds number compressible flow simulation method based on the immersed boundary method (IBM) is developed on the adaptive Cartesian grids to address two problems: one is the ability of large-scale Cartesian grid generation, and the other is the resolution of thin shear layers. For the former, an efficient automatic parallel generation method of adaptive Cartesian grids is proposed based on the k-d tree theory. The method has good parallel scalability and computational efficiency, e.g., the generation of 1.41 × 109 cells by 2048 cores takes only 0.40 min. For the latter, an IBM-wall function coupling method is designed to simulate geometrical configurations with high Reynolds numbers in the parallel framework. Numerical experiments show that the presented method can yield results consistent with the use of body-fitted grids. In conclusion, the presented method can realize a fully automatic simulation of high Reynolds number compressible flows, significantly reducing the labor cost in the computational fluid dynamics process, and can improve the accuracy and efficiency of engineering applications.

Prediction of the Temperature Field Development in Large Heat Storage Tanks for Integration in Network Simulation

Integrating an increasing amount of renewable energy into district heating systems requires thermal energy storages. For the planning and operation of the whole system valid and powerful storage models are essential for implementation in e. g. thermo-hydraulic network simulations and operational optimisation tools. The modelling of large tank thermal energy storages (TTES) up to 60,000 m³ can be insufficient by using a simple energy balance model as it does not provide information about the temperature profile. The detailed model called FreeTTES is capable of predicting the temperature distribution inside a large atmospheric TTES. This model simplifies fluid dynamic processes by assuming horizontal homogeneity and analyses them only in vertical direction. The analytical fluid mechanics approach is combined with numerical, measurement data-based approaches. The validation of the model is performed using DTS (distributed temperature sensing) data

Research progress of jet washing technology and its exploratory decoking application in delayed coking process

Abstract Considering the distinctive features of the delayed coking process and taking into account various particulate matter control technologies, the feasibility of using jet washing technology to remove coke powder from process gas is explored. The performance of scrubbers is heavily reliant on the quality of atomization, which in turn is influenced by liquid jet breakup. Due to the multiple interactions of various instabilities involved in jet breakup, as well as the short duration and small scale of this process, it is challenging to observe experimentally. Therefore, the specific fluid dynamics processes are not yet clear. In recent years, extensive research has been conducted on research methods, jet breakup modes, jet breakup characteristics, and jet breakup mechanisms. However, there is a lack of comprehensive review work summarizing these research advancements. This article aims to provide a comprehensive overview to facilitate jet scrubber designers’ systematic understanding of progress in jet breakup research. Furthermore, it discusses the significance of studying confined spaces for jet breakup with the objective of providing valuable insights for designing and optimizing delayed coker.

Ratcheting fluid pumps: Using generalized polynomial chaos expansions to assess pumping performance and sensitivity

A large diversity of fluid pumps is found throughout nature. The study of these pumps has provided insights into fundamental fluid dynamic processes and inspiration for the development of micro-fluid devices. Recent work by Thiria and Zhang [Appl. Phys. Lett. 106, 054106 (2015)] demonstrated how a reciprocal, valveless pump with a geometric asymmetry could drive net fluid flow due to an impedance mismatch when the fluid moves in different directions. Their pump's geometry is reminiscent of the asymmetries seen in the chains of contractile chambers that form the insect heart and mammalian lymphangions. Inspired by these similarities, we further explored the role of such geometric asymmetry in driving bulk flow in a preferred direction. We used an open-source implementation of the immersed boundary method to solve the fluid-structure interaction problem of a viscous fluid moving through a sawtooth channel whose walls move up and down with a reciprocal motion. Using a machine learning approach based on generalized polynomial chaos expansions, we fully described the model's behavior over the target 3-dimensional design space, composed of input Reynolds numbers (Rein), pumping frequencies, and duty cycles. Scaling studies showed that the pump is more effective at higher intermediate Rein. Moreover, greater volumetric flow rates were observed for near extremal duty cycles, with higher duty cycles (longer contraction and shorter expansion phases) resulting in the highest bulk flow rates.

Conservation laws for a perturbed resonant nonlinear Schrödinger equation in quantum fluid dynamics and quantum optics

Conservation laws for a perturbed resonant nonlinear Schrödinger equation in quantum fluid dynamics and quantum optics

A MATLAB/Simulink model of a parallel hybrid PEMFC/battery powertrain for passenger cars

Abstract The transition towards sustainable transportation solutions needs the development of efficient and environmentally friendly propulsion systems. Among these, Proton Exchange Membrane Fuel Cells (PEMFCs) seem to be a promising solution for sustainable powertrain design. This study presents the development of a MATLAB/Simulink model for a parallel hybrid FC/battery system representative of a passenger car, including all the auxiliary components and sub-systems. The model incorporates electrochemical, heat transfer, and fluid dynamic processes to accurately simulate the dynamic PEMFC stack and system behaviour. By implementing user-defined initial and boundary conditions, the model offers flexibility in simulating real-world scenarios, allowing the investigation of system performance under different environmental and dynamic driving conditions, as prescribed by the latest homologation protocols. Additionally, it accounts for the membrane degradation, which is a critical aspect affecting long-term durability, performance, and efficiency. Furthermore, a Graphic User Interface (GUI) has been developed to simplify the input of the main parameters, embedding the model in a user-friendly yet comprehensive tool designed for students, researchers, and engineers to evaluate the realizability of these efficient technologies. The intrinsic adaptability to model any FC/battery power system under a generic time-varying load constitutes an additional valuable point of the presented study to enable engineering progress, advancing the energy transition via sustainable powertrain solutions.

Modeling of Explosive Pingo-like Structures and Fluid-Dynamic Processes in the Arctic Permafrost: Workflow Based on Integrated Geophysical, Geocryological, and Analytical Data

Understanding the mechanisms responsible for the origin, evolution, and failure of pingos with explosive gas emissions and the formation of craters in the Arctic permafrost requires comprehensive studies in the context of fluid dynamic processes. Properly choosing modeling methods for the joint interpretation of geophysical results and analytical data on core samples from suitable sites are prerequisites for predicting pending pingo failure hazards. We suggest an optimal theoretically grounded workflow for such studies, in a site where pingo collapse induced gas blowout and crater formation in the Yamal Peninsula. The site was chosen with reference to the classification of periglacial landforms and their relation to the local deformation pattern, according to deciphered satellite images and reconnaissance geophysical surveys. The deciphered satellite images and combined geophysical data from the site reveal a pattern of periglacial landforms matching the structural framework with uplifted stable permafrost blocks (polygons) bounded by eroded fractured zones (lineaments). Greater percentages of landforms associated with permafrost degradation fall within the lineaments. Resistivity anomalies beneath pingo-like mounds presumably trace deeply rooted fluid conduits. This distribution can be explained in terms of fluid dynamics. N–E and W–E faults, and especially their junctions with N–W structures, are potentially the most widely open conduits for gas and water which migrate into shallow sediments in the modern stress field of N–S (or rather NEN) extension and cause a warming effect on permafrost. The results obtained with a new workflow and joint interpretation of remote sensing, geophysical, and analytical data from the site of explosive gas emission in the Yamal Peninsula confirm the advantages of the suggested approach and its applicability for future integrated fluid dynamics research.

Laser induced spark ignition of a gaseous methane–oxygen model rocket combustor

Laser induced spark ignition of a gaseous methane–oxygen model rocket combustor

Deep learning models for air quality forecasting based on spatiotemporal characteristics of data

The distribution of air-borne pollutants is governed by complex fluid dynamics processes involving convection and diffusion. The process is further affected by the characteristics of emission sources, meteorological parameters, socioeconomic factors, and land use patterns. Compared to deterministic and probabilistic air quality forecasting methods, data driven modeling of air quality parameters can address the large degree of freedom in air quality influencing parameters as well as offer interpretability and understanding of air pollutants' distribution at an increased spatial and temporal resolutions. This study focuses on the citywide prediction of air quality index (AQI) based on observations of pollutant concentrations, meteorological parameters, and spatiotemporal data. The study area includes Ansan city in South Korea, which has been observed as a hotspot for high concentrations of particulate matter. The air quality and meteorological were collected from 16 monitoring stations located in Ansan city. A detailed spatiotemporal analysis was performed to investigate the correlation between AQI records at the air quality monitoring stations. Based on strong spatiotemporal correlations observed between stations, several deep learning (DL) models were proposed, and their performance was investigated for different scenarios. It was observed that the selection of appropriate DL models should be based on (1) understanding of the underlying fluid dynamics process that control pollutant distribution and (2) spatiotemporal characteristics of data. Additionally, the complexity of DL models does not always guarantee the accuracy of the forecasts, and simple models can give good performance if the predictors are selected carefully to reflect the underlying physical process.

The dynamics of champagne cork popping revisited through high-speed schlieren imaging and computational fluid dynamics simulations

Cork popping represents a rich and complex fluid dynamics process, involving up to three phases (liquid, gas, and solid), three main chemical compounds (ethanol, water, CO2), and a moving cork gradually opening the bottle and blocking the fast progression of the expanding gas. In this work, we used high-speed, high-sensitivity schlieren imaging setups to provide a fresh perspective on this dynamical phenomenon. Our experimental results are systematically compared and interpreted on the basis of new computational fluid dynamics simulations. Our combined experimental and numerical works confirm the establishment of two supersonic expansions during cork popping from a champagne bottle.

Computational Fluid Dynamics Process for Front Windshield Mist Deposition and Its Subsequent Demisting

<div>A vehicle’s heating, ventilation, and air-conditioning system plays a dual role in passenger thermal comfort and safety. The functional aspects of safety include the front windshield demist and deicing feature of the system. The thin-film mist is a result of condensation of water vapor on the inner side of the windshield, which occurs at low ambient temperatures or high humidity. This mist deposition depends on the air saturation pressure at the front windshield. Indian regulation AIS-084 defines the experimental setup for testing, which encompasses both the mist deposition and its subsequent demist process. This regulation mandates testing, which occurs at a later stage of product development. This performance validation can be performed using a three-dimensional computational fluid dynamics approach.</div> <div>Current work summarizes the simulation process for both the mist deposition and the subsequent demisting phenomenon. The complexity of the flow physics is captured via the transient multiphase fluid flow phenomenon subjected to buoyancy effects. This phenomenon is simulated using the Eulerian wall film approach. The wall film deposition of the mist is modeled via species transport. Further, the near-wall thermal effects of surface conduction and heat transfer are simulated by modeling shell conduction layers. Vapor diffusion and relative humidity inside the cabin are modeled using a user-defined function. The process correlation is achieved for two categories of vehicles to establish the process efficacy and robustness. Moving ahead, a design of experiments (DOE) is planned to mitigate the need to simulate mist deposition. The DOE is planning to incorporate deviations in both the input airflow conditions and the imposed ambient conditions. The results from DOE point toward factors that might cause deviations in simulation results with respect to the test. Importantly, the study concludes that the uniform initial thickness assumption of the mist layer can be used for subsequent demist analysis.</div>

Constructing Rainfall Threshold for Debris Flows of a Defined Hazardous Magnitude

Debris flow can cause damage only when its discharge exceeds the drainage capacity of the prevention engineering. At present, most rainfall thresholds for debris flows mainly focus on the initiation of debris flow and do not adequately consider the magnitude and drainage measures of debris flows. These thresholds are likely to initiate numerous warnings that may not be related to hazardous processes. This study proposes a method for calculating the rainfall threshold that is related to a defined level of debris flow magnitude, over which certain damage may be caused. This method is constructed by using the transient rainfall infiltration analysis slope stability model (TRIGRS) and the fluid dynamics process simulation model (MassFlow). We first use the TRIGRS model to analyze slope stability in the study area and obtain the distribution of unstable slopes under different rainfall conditions. Afterward, the MassFlow model is employed to simulate the movement process of unstable slope units and to predict the depositional processes at the mouth of the catchment. Lastly a rainfall threshold is constructed by statistically analyzing the rainfall conditions that cause debris flows flushing out of the given drainage ditch. This method is useful to predict debris flow events of a hazardous magnitude, especially for areas with limited historical observational data.

Levenberg-Marquardt technique analysis of thermal and concentration storage in cone-disk apparatus with neural network-enhancement

Levenberg-Marquardt technique analysis of thermal and concentration storage in cone-disk apparatus with neural network-enhancement

Experimental and Numerical Investigation of Effect of Inclination on sCO2 Heat Transfer in a Circular Pipe

Abstract Supercritical carbon dioxide (sCO2) can be utilized as a working fluid in various thermal systems including large-scale power cycles; portable power production units, centralized coolant systems, and standalone cooling devices. However, the lack of accurate prediction tools such as heat transfer coefficient correlations and insufficient research studies about the mechanisms controlling heat transfer processes are hindering its practical realization for key energy and cooling systems. The overall objective of this study is to extend fundamental knowledge about heat transfer and fluid dynamic processes in conduits pertinent to sCO2 with an emphasis on flow direction and inclination effects. This paper presents the study on effects of gravity, buoyancy on sCO2 flow at temperatures near and away from the pseudo-critical temperature. The experimental setup consists of a high temperature and pressure sCO2 heat transfer loop and flow testing facility. Recently, researched sCO2 heat exchangers can have tubes oriented at different angles such as 45 deg or 90 deg to horizontal. For optimized design of efficient and cost-effective turbomachinery components utilizing sCO2 as the heat transfer fluid, an understanding of convective heat transfer inside a tube/pipe is equally as important as external heat transfer. This paper presents an experimental and numerical study on sCO2 heat transfer at various inclinations with angles ranging from 0 deg (horizontal) to 90 deg (vertical) along with upward and downward flow direction with different inlet temperatures. Thermocouple-based temperature measurement is utilized at multiple locations within the test section axially and circumferentially to study the temperature distributions on the tube surface. Computational fluid dynamics (CFD) simulations have been performed using ANSYS Fluent to complement experimental data. The CFD and experiment have been analyzed against the well-known Gnielinski Nusselt number correlation.

Projection–Subtraction X-ray Imaging Scheme for Studying Fast Fluid-Dynamics Processes in Porous Media

Projection–Subtraction X-ray Imaging Scheme for Studying Fast Fluid-Dynamics Processes in Porous Media

Computational Fluid Dynamics and Its Potential Applications for the ENT Clinician.

This article is an examination of computational fluid dynamics in the field of otolaryngology, specifically rhinology. The historical development and subsequent application of computational fluid dynamics continues to enhance our understanding of various sinonasal conditions and surgical planning in the field today. This article aims to provide a description of computational fluid dynamics, the methods for its application, and the clinical relevance of its results. Consideration of recent research and data in computational fluid dynamics demonstrates its use in nonhistological disease pathology exploration, accompanied by a large potential for surgical guidance applications. Additionally, this article defines in lay terms the variables analyzed in the computational fluid dynamic process, including velocity, wall shear stress, area, resistance, and heat flux.

Web Application for Mathematical Modeling of Unsteady Oil Flow in Porous Medium

Introduction. The analysis and interpretation of hydrodynamic research data are based on theoretical models and computational algorithms. Despite the demand for this topic, numerous issues related to unsteady fluid flows in oil reservoirs still require solutions. Therefore, mathematical setting of problems related to the account of unsteady fluid flow, the development of effective numerical methods and algorithms, their solution using modern web technologies are pressing. This study is aimed at developing a web application for mathematical modeling of the process of fluid filtration in single- porosity reservoirs when conducting a hydrodynamic study at a production well.Materials and Methods. To solve the problem, the methods of continuum mechanics and computational mathematics were applied. A model of oil flow in a single-porosity reservoir was presented. Python and JavaScript programming languages were used in the development of the application. The calculation results were stored in a relational database implemented using PostgreSQL tools.Results. A new web application has been developed for modeling the oil filtration process in single- porosity reservoirs. It is applicable for studying fluid dynamic processes and can be used to predict flowrates, production and calculation of optimal well operation modes.Discussion and Conclusion. The developed web application provides for building pressure and temperature fields in the reservoir near a flowing and shut-in production well and at various distances from it. This information makes it possible to urgently assess the duration of hydrodynamic studies, as well as to regulate the operation of wells. The application can be deployed in an existing network infrastructure and use all the functionality by connecting to a remote server. It is optimized for use on various platforms and has broad prospects for further development.

A two-phase pure slurry model for planetary cores: one-dimensional solutions and implications for Earth's F-layer

We develop and analyse a continuum model of two-phase slurry dynamics for planetary cores. Mixed solid–liquid slurry regions may be ubiquitous in the upper cores of small terrestrial bodies and have also been invoked to explain anomalous seismic structure in the F-layer at the base of Earth's liquid iron core. These layers are expected to influence the dynamics and evolution of planetary cores, including their capacity to generate global magnetic fields; however, to date, models of two-phase regions in planetary cores have largely ignored the complex fluid dynamics that arises from interactions between phases. As an initial application of our model, and to focus on fundamental fluid dynamical processes, we consider a non-rotating and non-magnetic slurry comprised of a single chemical component with a temperature that is tied to the liquidus. We study one-dimensional solutions in a configuration set up to mimic Earth's F-layer, varying gravitational strength$R$, the solid/liquid viscosity ratio$\lambda _{\mu }$and the interaction parameter$K$, which measures friction between the phases. We develop scalings describing behaviour in the limit$R \gg 1$and$\lambda _{\mu } \gg 1$, which are in excellent agreement with our numerical results. Application to Earth's core, where$R \sim 10^{28}$and$\lambda _{\mu } \sim 10^{22}$, suggests that a pure iron slurry F-layer would contain a mean solid fraction of at most 5 %.

Fluid Dynamics of Airtanker Firefighting

Airtanker firefighting is the most spectacular tool used to fight wildland fires. However, it employs a rudimentary large-scale spraying technology operating at a high speed and a long distance from the target. This review gives an overview of the fluid dynamics processes that govern this practice, which are characterized by rich and varied physical phenomena. The liquid column penetration in the air, its large-scale fragmentation, and an intense surface atomization give shape to the rainfall produced by the airtanker and the deposition of the final product on the ground. The cloud dynamics is controlled by droplet breakup, evaporation, and wind dispersion. The process of liquid deposition onto the forest canopy is full of open questions of great interest for rainfall retention in vegetation. Of major importance, but still requiring investigation, is the role of the complex non-Newtonian viscoelastic and shear-thinning behavior of the retardant dropped to stop the fire propagation. The review describes the need for future research devoted to the subject.

Prospects for the oil and gas potential of the zone of abnormally high reservoir pressures in the Yamalo-Nenets Autonomous Okrug assuming deep fluid dynamics

In Western Siberia, the zone of abnormally high reservoir pressures (AHRP) covers an area of more than 500 thousand km2 in the north of the basin. It begins with a clay layer above the Achimov formation of Neocomian sandy-silty formation, covers the Achimov formation, Upper–Lower Jurassic, Triassic and partially Paleozoic and is subject to tectonic control, which indicates the deep origin of this phenomenon. Gas-pressure, or gas-dynamic, theory of AHRP, proposed by K.A. Anikiev in the 70s of the 20th century, allows us to assess the prospects for oil and gas content of the AHRP zone higher than it is commonly-accepted. Analysis of the results of previously completed geological exploration work on the deep horizons of the Yamalo-Nenets Autonomous Okrug indicates that their relatively low efficiency (50–60%) is associated with the insufficiently high quality of well operations, primarily cementing, which is also due to the influence of AHRP. In all wells drilled to deep horizons, direct signs of oil and gas potential were obtained and cementing defects were identified. It is concluded that deep fluid-dynamic processes (active, pressure degassing of the Earth’s interior) are responsible both for the saturation of reservoir rocks with hydrocarbons and for the dynamics of their filling (ultra-high pressures and velocities), which determine the main characteristics of reservoir rocks. Recognition of a deep source of hydrocarbons will not only make it possible to fundamentally increase the resource base of the AHRP zone, but will also require a revision of ideas about the formation and structure of hydrocarbon deposits in this zone and the petrophysical substantiation of their models. However, to realize the unique hydrocarbon potential of the AHRP zone, it is necessary, first of all, to improve the quality of deep wells construction and appropriate information content.