Fluid Flow Dynamics Research Articles

Sizing and Selection of Pressure Relief Valves for High-Pressure Thermal–Hydraulic Systems

This study covers the critical concerns related to the sizing, selection, installation, maintenance, and testing of pressure safety valves (PSVs). The aim is to ensure the safety of pressurized systems, hydrostatic transmission systems, and hydraulic plants, including process plants, thermal power plants, and nuclear reactor systems. PSVs are devices that ensure the safety and reliability of pressurized vessels, lines, and systems during overpressure events. The task of selecting which PSV features are of greatest value for a specific purpose is complex—especially in the design of a high-pressure experimental thermal–hydraulic facility for hydrostatic and transient testing of the reactor system—when the systems are in the design and development phases and require qualification and demonstration to prove that they have reached a given level of technological readiness. The present study highlights the required steps for users to follow the associated rules, guidelines, and recommendations. As a part of this research, case studies are presented to help readers better understand the applicable strategy and standards. A discussion and a review of PSV performance degradation and failure are summarized to provide a better understanding of varied process applications and conditions, including fluid flow dynamics, boundary-layer formation and pressure drops, gas bubble formation and collapse, geometric configurations, inlet/outlet piping, abrupt pressure fluctuations, and acoustic resonance. Moreover, this study discusses the servicing and testing of PSVs in a multiphase pressurized system. Overall, it provides a basic overview of how PSVs ensure the safety of pressurized systems, supported by case studies and industrial practices.

NUMERICAL INVESTIGATION OF THE DYNAMICS OF MAGNETIZED CASSON FLUID FLOW OVER A PERMEABLE WEDGE SUBJECT TO DISSIPATION AND THERMAL RADIATIONS

The streamline boundary layer Casson liquid flow via wedge inspired by magnetic field effects is considered in this study. The governing laws of Casson fluid are modified by adding the effects of radiative heat flux, viscous dissipation and the surface permeability. Afterward, the model is transformed into simplified form using similarity variables and then analyzed via numerical scheme. The significant influence of the physical parameters appeared due to acting magnetic field, radiative heat flux, dissipation function and Prandtl number is specially treated for the flow behavior and thermal transfer mechanism plotted and discussed in detail. Further, tabulated results are also provided to replicate the study in future and this model is validated with the date published in open literature and it is found that these results are accurate and aligned with existing results.

Functional inequalities and strong Lyapunov functionals for free surface flows in fluid dynamics

Functional inequalities and strong Lyapunov functionals for free surface flows in fluid dynamics

Dynamic analysis of magnetorheological damper incorporating elastic ring in coupled multi-physical fields

The elastic ring assumes a multifunctional role, crucially providing support and reshaping oil-film thickness distribution in applications such as squeeze film dampers, demonstrating its practical efficacy. In this work, a magnetorheological damper (MRD) incorporating an elastic ring is proposed for the first time to improve the performance of damper. The innovative configuration of the elastic ring magnetorheological damper (ERMRD) is fabricated and integrated into a test platform of rotor system. The multi-filed coupling dynamic model of ERMRD is developed involving magnetic field interactions governed by Kirchhoff law, magnetorheological fluid flow dynamics derived from lubrication theory, and the elastic ring deformation based on thin plate theory. The intricate influence mechanisms of elastic ring and excitation current on oil-film characteristic of ERMRD, encompassing oil-film pressure, oil-film force, oil-film stiffness and damping, are investigated in detail. To substantiate the capabilities of ERMRD, it is implemented within the rotor system and a coupled dynamic model is established using Lagrange equation. This is followed by an in-depth analysis of the dynamic response using the Newmark-β method, including a comparative assessment with the conventional MRD. The results reveal that the elastic ring and excitation current influence oil-film pressure distribution in ERMRD from different perspectives, leading the oil-film force to present diverse variation characteristics. Compared to MRD, ERMRD exhibits weaker nonlinearity and superior damping performance.

Modeling soot filter regeneration process through surface-reactive flow in porous media using iterative lattice Boltzmann method

In this research, we utilized the Lattice Boltzmann Method (LBM) to model surface chemical reactions and the heat transfer occurring between gas and solid materials within porous media. Our comprehensive approach involved a detailed analysis of fluid flow dynamics, heat transfer mechanisms, and the complex behavior of reactive species. To ensure precise modeling, we employed the thermal counter-slip method to represent heat transfer and carefully chose the wet node scheme to manage surface chemical reactions and species transfer. We placed significant emphasis on methodically explaining our selected models and providing practical guidelines for their implementation, as well as establishing initial and boundary conditions. An essential part of our study was investigating the influence of specific physical parameters governing these processes, including the Péclet, Damköhler, and Prandtl numbers. Consequently, we successfully identified various combustion regimes and elucidated the roles played by chemical reaction rates, diffusion, and convection processes within each of these regimes.

An embedded microfluidic valve for dynamic control of cellular communication.

The communication between different cell populations is an important aspect of many natural phenomena that can be studied with microfluidics. Using microfluidic valves, these complex interactions can be studied with a higher level of control by placing a valve between physically separated populations. However, most current valve designs do not display the properties necessary for this type of system, such as providing variable flow rate when embedded inside a microfluidic device. While some valves have been shown to have such tunable behavior, they have not been used for dynamic, real-time outputs. We present an electric solenoid valve that can be fabricated completely outside of a cleanroom and placed into any microfluidic device to offer control of dynamic fluid flow rates and profiles. After characterizing the behavior of this valve under controlled test conditions, we developed a regression model to determine the required input electrical signal to provide the solenoid the ability to create a desired flow profile. With this model, we demonstrated that the valve could be controlled to replicate a desired, time-varying pattern for the interface position of a co-laminar fluid stream. Our approach can be performed by other investigators with their microfluidic devices to produce predictable, dynamic fluidic behavior. In addition to modulating fluid flows, this work will be impactful for controlling cellular communication between distinct populations or even chemical reactions occurring in microfluidic channels.

GPU-based molecular dynamics of fluid flows: Reaching for turbulence

Fluid dynamics is a ubiquitous problem that arises in different branches of science and industry. It is usually tackled by numerically solving continuum Navier-Stokes type equations. Molecular dynamics has been not a feasible tool to approach fluid dynamics until very recently due to its disproportional computational complexity for relevant system sizes. In this paper, we propose a new type of boundary conditions for molecular dynamics simulations of stationary fluid flows and present its possible GPU-based implementations in OpenMM and LAMMPS. We examine the performance and scalability of the proposed implementations. The benchmarking results show promising performance that makes it possible to reach turbulence in atomistic models of stationary fluid flows using modern supercomputers.

Biotransport in human phonation: Porous vocal fold tissue and fluid–structure interaction

Human phonation involves the flow-induced vibrations of the vocal folds (VFs) that result from the interaction with airflow through the larynx. Most voice dysfunctions correspond with the fluid–structure interaction (FSI) features as well as the local changes in perfusion within the VF tissue. This study aims to develop a multiphysics computational framework to simulate the interstitial fluid flow dynamics in vibrating VFs using a biphasic description of the tissue and FSI methodology. The integration of FSI and a permeable VF model presents a novel approach to capture phonation physics' complexity and investigate VF tissue's porous nature. The glottal airflow is modeled by the unsteady, incompressible Navier–Stokes equations, and the Brinkman equation is employed to simulate the flow through the saturated porous medium of the VFs. The computational model provides a prediction of tissue deformation metrics and pulsatile glottal flow, in addition to the interstitial fluid velocity and flow circulation within the porous structure. Furthermore, the model is used to characterize the effects of variation in subglottal lung pressure and VF permeability coefficient by conducting parametric studies. Subsequent investigations to quantify the relationships between these input variables, flow perfusion, pore pressure, and vibration amplitude are presented. A linear relationship is found between the vibration amplitude, pore pressure, and filtration flow with subglottal pressure, whereas a nonlinear dependence between the filtration velocity and VF permeability coefficient is detected. The outcomes highlight the importance of poroelasticity in phonation models.

Comparative Analysis of Mechanical Water Level Tank and Human Fluid Flow

Abstract Fluid flow in the human body can be modeled using a water-level tank, a commonly used mechanistic approach in mechanical engineering for fluid transport processes. Postoperative fluid data from patients undergoing cardiac surgery is used to estimate fluid flow dynamics and total body water in the human body. This simplified model provide a basic understanding of the dynamics of fluid flow processes in the human body and could aid in modeling distribution of fluids in compartments.

A hybrid Lagrangian–Eulerian particle finite element method for free‐surface and fluid–structure interaction problems

AbstractThe dynamics of fluid flows with free surfaces and interacting with highly deformable structures is a complex problem, attracting considerable attention. The Particle Finite Element Method (PFEM) is one of the various numerical methods recently proposed in the literature to simulate this type of problems. It is a mesh‐based Lagrangian approach, particularly suited for problems with fast changes in the domain topology, since the fluid boundaries and the Fluid–Structure Interaction (FSI) interface are naturally tracked by the position of the mesh nodes. However, when nonhomogeneous boundary conditions are imposed on velocities or when there are regions where the topology varies moderately, for example, in confined portions of the fluid domain characterized by fixed boundaries, an Eulerian formulation turns out to be more convenient. To exploit the advantages of both formulations, an adaptive hybrid Lagrangian–Eulerian approach is presented in this work. According to the proposed method, nodes on the fluid free‐surface and on the FSI interface are treated as Lagrangian, while the remaining nodes can be either Eulerian or Lagrangian. Furthermore, to increase the efficiency of the method, an algorithm to automatically detect runtime the transition zone between the two kinematic descriptions is devised. To validate the proposed approach, several numerical examples are developed and their results are compared to those available in the literature.

Advanced cerebrospinal fluid flow MRI findings of aqueductal stenosis caused by web.

The aqueductal web (AW) is one of the causes of aqueductus stenosis (AS). Recent advances in Magnetic resonance (MR) imaging have enabled us to better reveal the cerebrospinal fluid (CSF) flow dynamics and aqueductal anatomy. The aim of this study is to evaluate the CSF flow dynamics of patients with AW with phase contrast Magnetic resonance imaging (MRI) and compare them with the imaging findings. We evaluated 23 patients under 65-year-old age. On constructive interference in steady-state (T2 CISS) images, the width of prepontine cistern (PPC) and the width of Sylvian aqueduct (SA) were measured. Localization and number of webs were evaluated. The existence of flow at the aqueduct and the presence of spontaneous third ventriculostomy (STV) were evaluated on sagittal Sampling Perfection with Application optimized Contrast (SPACE) sequences. Of the 23 patients included in the study, 11 were male and 12 were female. The mean age was 34.02 (0.5-64). A total of 31 AWs were detected in 23 patients. Six of 23 patients (26.1%) had STV and 17 of those not. Four of 23 patients (17.4%) had aqueductal flow on SPACE sequences. The PPC distance was significantly wider in patients with STV (median: 6.7-4.5, interquartile range (IQR): 1.35, p = 0.004). In the cases where artifact secondary to flow is observed in SPACE sequences in aqueduct, the Evan index (EI) was significantly lower (median: 0.2955-0.3900, IQR: 0.03-0.14, p < 0.001). In patients with a low EI, there may be flow in the SA even if there is a web. In patients with a wide PPC distance, it is necessary to consider the presence of STV and evaluate the presence of flow with the SPACE sequences.

Spatial Characterization of Shallow Structures in the Revell Batholith Integrating Seismic Imaging Techniques

The Revell Site, located in Northwestern Ontario within the Canadian Shield, is being assessed as a potential Deep Geological Repository (DGR) for Canada’s used nuclear fuel. Effective DGR establishment requires comprehensive subsurface assessment, particularly in evaluating structural stability, hydrogeological attributes, geological composition, and geochemical properties. Key among these considerations is understanding the three-dimensional characteristics of structural features to ensure the site’s suitability for long-term containment of radioactive materials. This case study focuses on imaging and characterizing structures within the predominantly intact biotite granodiorite-tonalite host rock at the Revell Site. Borehole data reveals these structures as mostly sub-horizontal mafic intrusions, with thicknesses of up to 3.5 m. They appear either as separate, discrete entities or in stacked configurations. Despite their limited thickness, most of these intrusions exhibit discernible attributes in surface seismic images due to their distinct physical properties. Some, however, exhibit velocity variations that decrease their overall reflectivity properties. An integrative approach employing surface seismic, Vertical Seismic Profiles (VSP), and borehole data facilitates the spatial identification of over 30 of these mafic structures. This comprehensive characterization not only lays the foundational framework for future discrete fracture network models but also provides important support for simulations related to fluid flow dynamics, groundwater behavior, contaminant dispersion, and heat transport mechanisms within the Revell Site. This study underscores the critical role of in-depth subsurface characterization in ensuring the secure, long-term management of radioactive materials in DGRs.

Revealing the effects of laser beam shaping on melt pool behaviour in conduction-mode laser melting

Laser beam shaping offers remarkable possibilities to control and optimise process stability and tailor material properties and structure in laser-based welding and additive manufacturing. However, little is known about the influence of laser beam shaping on the complex melt-pool behaviour, solidified melt-track bead profile and microstructural grain morphology in laser material processing. A simulation-based approach is utilised in the present work to study the effects of laser beam intensity profile and angle of incidence on the melt-pool behaviour in conduction-mode laser melting of stainless steel 316L plates. The present high-fidelity physics-based computational model accounts for crucial physical phenomena in laser material processing such as complex laser–matter interaction, solidification and melting, heat and fluid flow dynamics, and free-surface oscillations. Experiments were carried out using different laser beam shapes and the validity of the numerical predictions is demonstrated. The results indicate that for identical processing parameters, reshaping the laser beam leads to notable changes in the thermal and fluid flow fields in the melt pool, affecting the melt-track bead profile and solidification microstructure. The columnar-to-equiaxed transition is discussed for different laser-intensity profiles.

Air Interactions of Magnetically Driven Plasma Discharges in Crossflow

Motivated by the use of magnetohydrodynamic devices in fluid dynamic flow control research, the current work experimentally studied the actuation mechanism and the resulting aerodynamic interactions of magnetically driven low-current arc-plasma discharges. The investigation was conducted in the context of boundary-layer interactions in low-speed crossflow conditions through the use of coaxial and v-shaped geometries. Time-averaged velocity field measurements showed that the toroidal region of vorticity induced by the coaxial geometry in quiescent air resulted in the formation of a horseshoe vortex in crossflow. Similarly, the v-shaped actuator resulted in the formation of streamwise vortices. The resulting boundary layers had s-shaped streamwise velocity profiles as measured in the wall-normal direction characteristic for the flow downstream of a conventional vortex generator pair, due to the three-dimensional mixing induced by coherent vortex structures. A simplified model based on intermolecular momentum transfer through collisions is proposed to explain the fundamental discharge–air interactions and the induced flowfields. These results inform the applications of various magnetically driven discharges in the field of aerodynamic flow control.

A Composite Framework Model for Transient Pressure Dynamics in Tight Gas Reservoirs Incorporating Stress Sensitivity

Natural gas is an eco-friendly energy source with low carbon emissions, making it attractive globally. Understanding gas reservoirs is crucial for sustainable extraction and optimizing potential. However, the complicated fluid flow and production dynamics within intricate gas reservoirs, particularly those characterized by abnormally high pressures and tight porous media, remain partially understood and demand further investigation. In a tight porous medium subjected to high pressure, the assumption of constant permeability is no longer valid. Consequently, a novel composite seepage model has been developed in this study, which considers the responsiveness of permeability to stress. Perturbation theory is employed to address the inherent non-linearity demonstrated by the permeability modulus. The solution of dimensionless pressure responses under constant production conditions is accomplished in the Laplace domain by implementing integral transformation methods. Overall, a comprehensive model is provided to understand the production behaviors of tight gas reservoirs. Moreover, in order to comprehend the transient flow characteristics of tight gas reservoirs, log–log plots are generated through the Stehfest numerical inversion approach, with the flow regimes categorized based on the normalized time phases of the pressure curves. Parametric investigations reveal that stress sensitivity detrimentally affects permeability, resulting in more pronounced pressure declines during the intermediate and late flow phases. The transient seepage model elaborated in this study is able to consider the pertinent formation and well parameters. These interpreted parameters bear significance in designing hydraulic fracturing operations, assessing the potential of tight gas reservoirs, and ultimately enhancing gas production. The presented model not only enhances our understanding of the behavior of horizontal wells in stress-sensitive tight gas reservoirs but also makes a valuable contribution to the broader discussion on transient flow phenomena in petroleum engineering.

Transient Thermomechanical Stress Analysis of Hot Surface Ignition Device Using Sequentially Coupled Computational Fluid Dynamics–Finite Element Analysis Approach

Abstract Energy addition using a hot surface ignition device is required for reliable ignition of aircraft compression ignition engines running on fuel variations and at altitude conditions. Thus, durability of the hot surface ignition device is crucial for application in these engines. Thermomechanical stress is one of the key parameters that determine durability, which requires an accurate prediction of the transient temperature field based on well-defined boundary conditions representing the dynamic and complex fluid flow inside engines. To meet this requirement, the present study focuses on transient thermomechanical stress analysis using a sequentially coupled computational fluid dynamics (CFD)–finite element analysis (FEA) approach to understand transient thermomechanical responses of the hot surface ignition device. A three-dimensional transient reacting flow simulation was conducted first using converge software, the results of which were exported to map thermal and pressure boundary conditions onto a structural finite element mesh. Transient thermomechanical stress analysis was performed sequentially using abaqus software utilizing the mapped boundary conditions. The results such as transient temperature history, resultant thermomechanical stress, displacement, potential failure modes, etc., were critically reviewed, which can provide helpful information for further design improvement.

On the superpropagating nonlinear waveform in critical superthermal fluid

The superthermality indices of positron (electron) contributions to the new nonlinear wave profiles characterized by the model as supersoliton, cnoidal, shocklike, and super-periodic wave propagation have been obtained in the superthermal ionosphere plasma pair. These profiles that exhibit critical behaviors are described by the modified KP equation. Furthermore, the novel solutions have been exposed and the super-solitary and period solutions are derived and explained using the Jacobi elliptic function expansion method for the Modified Korteweg–De Vries (MKdV) equation. These solutions may be useful in the space of ionosphere fluids. Indeed, the MKdV model is potent for the dynamics of fluid flow. The super propagating waves obtained under the influence of critical densities represent a source of forcing or collapsing energy waves in space plasma fluids. To check the impacts of superthermality on the progress of nonlinear formations, all the given solutions are deliberated by the superthermal factor in ionosphere fluid observations and applications.

Chemically reactive Squeezed flow of Maxwell nanofluid confined by parallel stratified walls subjected to radiative flux

This study features numerical analysis of squeezing flow within a confined parallel-wall geometry subjected to chemical reactions, magnetohydrodynamics (MHD), transpiration, double stratification, heat generation and thermal radiation. The flow formulation in this research is based on the rheological expressions of a rate type (Maxwell) fluid capturing the non-Newtonian behavior. Such consideration enables the modeling of complex fluid behavior involving both viscous and elastic responses, making it applicable to a wide range of scenarios in materials science, rheology, and fluid dynamics. In addition, the Buongiorno two-component nanofluid model is opted to model the transport equations. Equations elaborating the dynamics of fluid flow and heat-mass transport are established, taking into account the specific assumptions like the presence of a lower magnetic Reynolds number and the insignificance of viscous dissipation. Following this, these equations are transformed into a dimensionless form by introducing similarity variables. The numerical simulations are carried out utilizing the MATLAB software package, employing the bvp4c scheme. Our findings indicate a rise in horizontal and vertical velocities subjected to higher squeezing parameter, however, contrasting results are found for temperature, where an increase in squeezing parameter led to a diminution in temperature, signifying a cooling effect.

Influence of the spatial laser energy absorption on the molten pool dynamics in high-power laser beam welding

The spatial laser energy absorption inside the keyhole is decisive for the dynamic molten pool behaviors and the resultant weld properties in high-power laser beam welding (LBW). In this paper, a numerical simulation of the LBW process, considering the 3D transient heat transfer, fluid flow, and keyhole dynamics, is implemented, in which the free surface is tracked by the volume-of-fluid algorithm. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by an advanced ray-tracing method based on a localized level-set strategy and a temperature-dependent absorption coefficient. The laser energy absorption is analyzed from a time-averaged point of view for a better statistical representation. It is found for the first time that a significant drop in the time-averaged laser energy absorption occurs at the focus position of the laser beam and that the rest of the keyhole region has relatively homogeneous absorbed energy. This unique absorption pattern may lead to a certain keyhole instability and have a strong correlation with the detrimental bulging and narrowing phenomena in the molten pool. The influence of different focus positions of the laser beam on the keyhole dynamics and molten pool profile is also analyzed. The obtained numerical results are compared with experimental measurements to ensure the validity of the proposed model.

Conjugate dissipative radiative heating with thermal slipping and the entropy production on the thrust of MHD gold blood nanofluid with curvature effects

AbstractThis article analyzes the impact of conjugated dissipative radiative heat transfer with heat source/sink, thermal slip, and the transverse magnetic field on the behavior of the magnetohydrodynamic (MHD) peristaltic thrust containing ferromagnetic gold nanoparticles (AuNPs) with different shape factors through the non‐Newtionian blood flow within compliant walls tube. Entropy generation (EG) plays a prominent role in all aspects connected to thermodynamics and heat transfer aiding in the identification and reduction of system irreversibilities. The sources of irreversibility stem from dissipative friction inherent in fluid flow, the presence of a magnetic field, and the heat transfer process. The ferromagnetic gold nanoparticles (AuNPs) exhibit diverse shapes (bricks, cylinders, and platelets) and possess both magnetic and thermal attributes thereby enhancing the efficiency of heat transfer process. The peristaltic thrust drives the dynamic behavior of the gold blood nanofluid through a compliant tube. The tube walls are flexible and exhibit a curvature effects that can alter the dynamics of fluid flow. The effective Hamilton‐Crosser model is selected to express the thermal conductivity of the nanofluid. Gold blood nanofluids can be treated as incompressible, non‐Newtonian, and MHD fluid flow. The governing equations of the system are solved using the perturbation approach under the assumptions of low Reynolds numbers and long wavelength. Hybrid interactions of magnetic field, radiative heating, thermal slip, elastic wall properties, and gold nanoparticles shapes and concentrations are investigated within the gold blood nanofluid flow. The resulting graphs include the profiles of velocity, temperature distributions, EG, and irreversibility parameters under the influence of the above parameters. The findings reveal that the overall EG rises with increasing values of heat source intensity, Brinkman number, temperature difference factor, compliant wall curvature coefficient, and gold nanoparticles concentrations. Additionally, it is observed that an increase in magnetic flux strength results in the emergence of reversal flow patterns near the walls. This arises due to the augmented magnetic flux obstructing the peristaltic nanofluid flow leading to reduce streamwise velocity. Moreover, heightened magnetic flux strength causes temperature reduction for both thermal slip and non‐slip conditions. Generally, the presence of a thermal slipping parameter further enhances the distribution of temperature. In essence, the rationale and significance of this study primarily revolve around comprehending the interplay of these diverse factors with MHD peristaltic motion of gold blood nanofluid and EG. This not only furthers our theoretical understanding of complex systems but also has practical implications that can improve new technologies, processes, and medical applications. For example, in medical treatments like photothermal therapy (PPT), insights gained from this research can help in developing more effective and precise treatment methods. By understanding the impact of these factors on EG, new ways can be identified to minimize or manage system inefficiencies leading to more sustainable and optimized treatment processes. This research holds promise for application in cancer detection and treatment by employing a combination of PPT and magnetic hyperthermia. This entails dispersing AuNPs into the blood circulation through arteries and blood vessels and subsequently applying photothermal radiation and a magnetic field.