Fluid Elements Research Articles

Stochastic Lagrangian wall deposition model for RANS prediction of deposition in turbulent gas–solid flows

In industrial-scale Reynolds Averaged Navier–Stokes (RANS) simulations, a wall-modeled approach is often employed, specifically choosing a dimensionless wall-cell height much greater than one. However, in gas–solid flows, a coarse description of the boundary layer may lead to inaccurate results in terms of particle dispersion and deposition. In this study, we conducted an investigation on stochastic RANS dispersion models with deposition on smooth walls using a wall-modeled approach. These models were applied to turbulent channel flows in both vertical and horizontal orientations. The modeling approach involved the adoption of the Euler–Lagrange formalism and the RANS k−ϵ turbulence model in OpenFOAM®. To assess particle behavior first, a simple homogeneous isotropic stationary turbulence (HIST) case was examined. Fluid elements were also tracked in an inhomogeneous turbulence for dispersion analysis. These tests gave the good formulation for the dispersion model to be used for particle tracking coupled with turbulent channel flow simulation. However, the deposition results in turbulent channel using such stochastic dispersion model in the wall-cell were found to be consistently overestimated across various scenarios for low-inertia particles. To address these limitations arising from the coarse description of the boundary layer, we examined, implemented, and evaluated a Lagrangian stochastic wall deposition model. The activated deposition model demonstrated good agreement with experimental data.

FSI Modeling and simulation analysis of superimposed valves in flow state of hydraulic shock absorbers*

Abstract This study, through rigorous bench testing, has identified the pivotal parameters influencing the oil flow state within the shock absorber. Based on the Reynolds number parameter model, a reduced parameter model was established, incorporating the number of holes in the throttle valve, their diameters, and the diameters of the piston and piston rod as fundamental parameters. To ensure the model’s precision, this study developed high-accuracy solid and fluid finite element models, defined specific time steps for both laminar and turbulent flows along with their respective numerical methods, and executed a detailed Fluid-Structure Interaction (FSI) finite element simulation analysis. The findings indicate that fluid-structure interaction simulation accurately captures the shock absorber oil’s flow states across laminar, transitional, and turbulent phases, identifying the maximum Reynolds number position, with the simulation’s velocity-specific results aligning closely with the parameter model, showing a maximum deviation of 22%, a minimum of 2%, and an overall average error of 9.1%.

A case study of the Yanshanian fluorite mineralization in South China: Fluid inclusion, element and isotope geochemistry and zircon U-Pb geochronology of the Kantian fluorite deposit in southern Jiangxi Province

The Yanshanian events have led to the development of South China as a unique granite province globally. Within South Jiangxi, numerous metallic and non-metallic deposits have a close association with Mesozoic granite formations. The Kantian fluorite deposit, a newly discovered non-metallic deposit in southern Jiangxi Province, is one such deposit that is linked to Mesozoic granites. The orebody at the Kantian fluorite deposit is identified as occurring in veined structures within the silicification fracture zone of Mesozoic granites, with strict control exerted by fault systems. Fluorite ore can be classified into two categories based on the amount of quartz and fluorite. The first category is the fluorite quartz type, which has a higher amount of quartz than fluorite. The second category is quartz fluorite type, which has more fluorite than quartz. Among these two categories, the quartz fluorite type is precipitated during the primary mineralization stage. Through the analysis of fluid inclusions within the fluorite, it was determined that the homogenization temperature is relatively low, ranging from 133 to 236℃. The fluid inclusions also display low salinity (0.18–3.39 wt% NaCl eqv.) and low density (0.75–0.96 g/cm3). Laser Raman spectroscopy revealed that the primary components of the fluid inclusions are H2O, with minor C3H6. Isotope analysis indicated δDVSMOW values of fluorite ranging from −61.9 ‰ to −54.8 ‰ (average −59.8 ‰), while δ18OVSMOW values varied from 1.3 ‰ to 3.1 ‰ (average 2.0 ‰). This study presents chronological, petrological and geochemical data that suggest several processes. The metallogenic age is 135.6 ± 0.7 Ma. The mineralizing fluids were identified to the NaCl-H2O system, with heated meteoric water identified as the primary source; The ore-forming materials originated from the granite, and water–rock interactions are proposed as the primary mechanism for fluorite precipitation. Based on a tectonic setting characterized by stretching, which is closely linked to the subduction of the Pacific plate, we proposed a model for the Kantian fluorite deposit.

Alkali and alkaline earth elements in follicular fluid and the likelihood of diminished ovarian reserve in reproductive-aged women: a case‒control study

BackgroundImbalances in alkali elements (AEs) and alkaline earth elements (AEEs) cause reproductive disorders. However, it remains unclear whether AEs/AEEs in follicular fluid have a relationship with the serious reproductive disorder known as diminished ovarian reserve (DOR).MethodsA nested case‒control study was carried out in China. Follicular fluid samples from 154 DOR patients and 154 controls were collected and assessed for nine AEs/AEE levels. Both the mixed and single effects of the elements on DOR were estimated with a Bayesian kernel machine (BKMR) and logistic regressions.ResultsThe DOR group had higher median concentrations of Li, Na, and K in follicular fluid (all P values < 0.05). The logistic regression showed that compared with their lowest tertile, the high tertiles of K [OR:2.45 (1.67–4.43)], Li [OR: 1.89 (1.06–3.42)], and Cs [OR: 1.97 (1.10–3.54)] were significantly associated with the odds of DOR. The BKMR model reported that the DOR likelihood increased linearly across the 25th through 75th percentiles of the nine-AE/AEE mixture, while the AE group contributed more to the overall effect.ConclusionThis study revealed an association in which the likelihood of DOR increased with higher overall concentrations of AE/AEEs in follicular fluid. Among the nine detected elements, K, Li, and Cs exhibited significant individual associations with DOR. We provide new clues for the environmental factors on female fertility decline.Trial registrationRetrospectively registered.

On the evidence of helico-spiralling recirculation within coherent cores of eddies using Lagrangian approach

Oceanic eddies exhibit remarkable coherence and longevity compared to other transient features in the surrounding flow. They possess the ability to transport properties over extensive distances while maintaining their material identity intact. The Lagrangian Coherent Structure (LCS) framework has proven effective in capturing these coherent eddies, where they display a solid-body-like rotation. Although various LCS approaches have been employed to investigate different facets of coherent eddies, a comprehensive understanding of their three-dimensional structures and internal dynamics remains elusive. This study aims to advance our comprehension of coherent eddies’ structural characteristics and delve into the precise nature of their internal dynamics by utilizing the Lagrangian Averaged Vorticity Deviation approach. Two eddies, one cyclonic and the other anti-cyclonic, were chosen from a high-resolution simulation carried out in the Bay of Bengal using the Regional Ocean Modeling System (ROMS). The findings unveil that these eddies have three-dimensional coherent cores resembling gently tapered cones that are broader at the surface and gradually narrow towards the bottom. Intriguingly, the dynamically coherent core of these eddies exhibits simultaneous upwelling and downwelling while maintaining their volumes during advection due to persistent material coherence. The three-dimensional trajectories followed by the fluid parcels inside the coherent core are helical. Their two-dimensional horizontal projections show alternating spiral bands of upwelling and downwelling which are the manifestations of Vortex Rossby Waves. These observations lead to a conceptual framework of a three-dimensional helico-spiralling recirculation pattern within the coherent cores of eddies.

Influence of Unbalance and Differential Pressure on the Stability of Vertical Rotor-Seal System

Abstract The rotordynamic (RD) fluid force generated in fluid elements such as seals in turbomachinery affects the stability of turbomachinery and causes shaft vibrations. Various studies have been conducted to clarify the effects of seals on the stability of rotor systems. Many studies have investigated the rotor dynamics of horizontal rotating shaft systems, considering the RD fluid force generated in the seals, and in these studies, the stability of horizontal rotating shaft systems has been assessed via eigenvalue analysis using RD coefficients. However, few studies have analyzed vertical rotating shaft systems. The dynamic behavior of vertical rotating shafts differs significantly from that of horizontal rotating shafts because the weight of the rotor does not act on the seal in a vertical rotating shaft system. Vertical rotating shaft systems are generally prone to instability because of the fluid film whirl, and the amplitude of the shaft whirl tends to be large. When the amplitude is large, the RD fluid force cannot be linearized around the equilibrium point using RD coefficients. Therefore, destabilization and stabilization phenomena that appear in vertical rotating shaft systems cannot be predicted using eigenvalue analysis. Fluid–structure interaction (FSI) analysis that considers the interaction between the shaft vibration and the RD fluid force generated in seals is required to predict such phenomena. This study used FSI analysis to investigate the effects of unbalance and differential pressure on the stability of a vertical rotating shaft system subjected to RD fluid force generated in the seal.

Two-phase flow-induced vibration of tilted curved bi-directional functionally graded nanopipe in supersonic airflow

Flow-induced vibration is known as a prevalent phenomenon in various industries. As a result of the flow, dynamic fluid forces are generated, which lead to the excitation of the system. Multiphase flow, found commonly in both natural and industrial settings, including industrial plants, is a significant source of noise and vibration. In the two-phase flow, as a particular case of multiphase flow, flow configuration plays a major role in the system’s traits. Despite recent advancements in flow-induced vibration, it is still considered an unresolved topic. This research develops a new multi-physics simulation for the stability study of a two-directional functionally graded tilted curved cylindrical nanopipe conveying a liquid-gas two-phase flow. Nonlocal stress–strain gradient theory (NSGT) with two size-dependent parameters (nonlocal and length scale) is presented to simulate the current nanostructure. Newton’s second law has been employed to govern the resultant forces that act on a control volume at a differential fluid element of fluid. Hiring the finite element (FE) approach alongside the generalized differential quadrature role (GDQR), both the eigenvector and eigenvalue problems are presented for analyzing the characteristics of the nanosystem under various situations. An exhaustive parametric analysis is also provided to make clear the role of varied parameters such as velocity of fluid flow, aerodynamic pressure, air yaw angle, and gas volume fraction coefficient on the system’s fundamental frequency.

Analysis of r - Adaptive coupling adaptive time integration strategy in FEM of seismic liquefaction

In seismic finite element analysis of saturated soils, the challenges primarily reside in liquefaction and the large deformation of soil induced by strong earthquakes. Traditional updated Lagrangian methods may result in severe mesh distortion after updating the spatial configuration of nodes. To address this issue, this study develops an r - adaptive approach based on a solid - fluid coupling finite element method (FEM) platform to mitigate mesh distortion problems. This technique optimizes mesh nodes without altering the overall topology, thereby maintaining mesh integrity. However, enhancing mesh accuracy comes at the expense of increased computational costs. To alleviate high computational expenses, this study couples two types of adaptive time stepping techniques, based on mixed error and displacement history curvature, with mesh adaptation. Through verification on two typical dynamic liquefaction models of saturated soil on embankment and subway station, this technique effectively balances the relationship between computational accuracy and costs.

ИЗУЧЕНИЕ МАКРО- И МИКРОЭЛЕМЕНТНОГО СОСТАВА РОТОВОЙ ЖИДКОСТИ ПРИ ПРОВЕДЕНИИ ПРОФЕССИОНАЛЬНОГО ОТБЕЛИВАНИЯ ЗУБОВ

Aesthetic dentistry is one of the up-to-date trends in dentistry. There are a lot of methods targeted at eliminating discoloration, including teeth whitening. The dentist’s task is to choose the optimal whitening system. Patients, especially those who work in hazardous industries, are also interested in getting a snowwhite smile. The authors have conducted a comparative assessment of the effectiveness of a chemical activation system with a 37% concentration of hydrogen peroxide (USA) with a chemical activation system with a 35% concentration of carbamide peroxide (Russia). Changes in the chemical composition of oral fluid were revealed after the professional whitening procedure. The subject of the study is the chemical composition of oral fluid. The goal is to study the chemical composition of oral fluid during teeth whitening procedures. Methodology. The studies were carried out on the basis of the Department of Therapeutic Dentistry of the Federal State Budgetary Educational Institution of Higher Education “Privolzhsky Research Medical University” of the Ministry of Health of Russia, Autonomous Non-Profit Organization “Center for Biotic Medicine” of Dr. A.V. Skalny, State budgetary institution of the Ryazan region “Dental Clinic No. 1” (Ryazan). The study involved 50 patients of both sexes from 23 to 45 years old, who were employees of an aircraft repair plant in Ryazan. Patients were divided into two groups. A chemical study of oral fluid was performed for 50 people before teeth whitening and for 15 people, in the control group, after teeth whitening. Results. Determined macro- and micro elements differed in quantitative content between the studied groups. Comparing the obtained data of the concentration of elements in saliva with the results of the work of other researchers, we can conclude that there is a scattering in the results according to the literature, possibly due to the different “microelement” status of the regions in which the sample donors live. Conclusions. The results of the study demonstrate that both whitening systems have a pronounced effect on the chemical composition of the oral fluid, while the system based on 37% hydrogen peroxide led to a greater degree of normalization of the level of chemical elements in the oral fluid.

From Streamline to Pathline: Visualizing Particle Trajectories Under Changing Velocity Fields

Summary Monitoring of subsurface fluid motion is critical for optimizing hydrocarbon production and CO2 sequestration. Streamlines are frequently used to visualize fluid flow; however, they provide only an instantaneous snapshot of the velocity field and do not offer an exact representation of fluid movement under varying field conditions. In contrast, pathlines are constructed by tracking individual particles within the fluid, enabling us to trace the movement of these particles as they traverse through changing velocity fields. Pathline is the trajectory that an individual fluid particle follows in the reservoir. It can be thought of as “recording” the path of a fluid element in the flow field for a given time interval. Pathlines are distinct from streamlines which represent a snapshot of the velocity field at a given instant. The direction the path takes is determined by the streamlines at a specific instant. To start with, streamlines are traced based on the grid face fluxes of finite-difference simulation. Streamline tracing continues till the time of flight equals the current time. The endpoints of the current streamlines become the starting points for the next tracing period. Thus, our formulation incorporates changing flow fields, and the process is repeated for each time interval until the end. The proposed injection monitoring method is tested using a 3D field-scale model with complex geologic features to demonstrate its power and utility. The pathlines were compared with streamlines, as well as the water saturation distribution. Three scenarios are tested: a constant well schedule, a changing well schedule with partial shut-in, and a changing well schedule with a whole field cessation. Results indicate that the pathline provides a more accurate swept volume, consistent with saturation distribution. The robustness of our algorithm and implementation is demonstrated with a complex embedded discrete fracture model (EDFM) to visualize flow patterns in discrete facture network. Pathlines display the fluid flow across fractures and are subsequently used to explore the sweep efficiency and the well connectivity.

Non‐conservation and conservation for different formulations of moist potential vorticity

AbstractPotential vorticity (PV) is one of the most important quantities in atmospheric science. In the absence of dissipative processes, the PV of each fluid parcel is known to be conserved, for a dry atmosphere. However, a parcel's PV is not conserved if clouds or phase changes of water occur. Recently, PV conservation laws were derived for a cloudy atmosphere, where each parcel's PV is not conserved but parcel‐integrated PV is conserved, for integrals over certain volumes that move with the flow. Hence a variety of different statements are now possible for moist PV conservation and non‐conservation, and in comparison to the case of a dry atmosphere, the situation for moist PV is more complex. Here, in light of this complexity, several different definitions of moist PV are compared for a cloudy atmosphere. Numerical simulations are shown for a rising thermal, both before and after the formation of a cloud. These simulations include the first computational illustration of the parcel‐integrated, moist PV conservation laws. The comparisons, both theoretical and numerical, serve to clarify and highlight the different statements of conservation and non‐conservation that arise for different definitions of moist PV.

Ядерно-физическая медицинская элементология как раздел медицинской радиологии

Purpose: Medical elementology and its subsection nuclear physics medical elementology, as the most important areas of biomedical science, are still insufficiently included in the arsenal of medical radiology as a fundamental basis for the development and use of new methods for diagnosing and treating various diseases, including oncological ones. For the successful establishment of nuclear physics medical elementology as a new scientific discipline, it is necessary to develop a clear methodology for its further development. Results: The definition of the subject of research and the main postulates of medical elementology is given. The close interrelation of knowledge about the content and metabolism of chemical elements, as well as their radioactive and stable isotopes, with the needs of medical radiology is shown. The following areas of research are considered: 1) The use of chemical elements, as well as their radioactive and stable isotopes in medicine; 2) Visualization of organs and tissues, as well as in vivo determination of the content of chemical elements in them; 3) Nuclear physical methods for determining chemical elements in samples of tissues and fluids of the human body in solving oncological problems; 4) The role of chemical elements in calculating absorbed doses during radiotherapy; 5) The use of nuclear physical methods in the formation of groups at increased risk of cancer. A range of modern nuclear physics analytical methods acceptable in clinical practice and as an adequate research tool is outlined. The need for the integrated use of nuclear physics analytical technologies to obtain reference values ​​for the content of chemical elements in various organs, tissues and fluids of the human body in normal and various pathological conditions, as well as to organize the strictest quality control of measurements and unify methodological approaches is demonstrated. The modern possibilities of using the achievements of nuclear physics medical elementology in solving the problems of medical radiology are determined and the priorities for the future are outlined. Conclusion: The steady development of nuclear physical methods of chemical elements analysis and their implementation in medicine is constantly expanding the scope of possibilities of medical elementology. The development of this area will certainly make a significant contribution to the future successes of medical radiology.

Risk of Trace Element Imbalance in Cases of Occupational Allergic Diseases

Introduction: The relevance of the study is attributed to the lack of knowledge of the mechanisms of development and specifics of the clinical picture of occupational allergic diseases. Objective: To establish the levels of essential trace elements in biological substrates of patients with occupational allergies. Materials and methods: In 2014–2018, we analyzed zinc and copper levels in urine, blood serum, and lymphocytes of patients with occupational allergic skin and respiratory diseases by the atomic absorption method. Relative risk was calculated using a four-field contingency table. Results: In patients with work-related allergic contact dermatitis and bronchial asthma, zinc and copper concentrations in blood serum increased while urinary excretion of these elements decreased. Quantitative patterns of the concentrations of trace elements in body fluids of the patients with skin and respiratory allergies were unidirectional compared to the reference group. Relative risk values showed that lower levels of copper in urine and zinc in blood serum and lymphocytes, as well as higher serum copper indicated the risk of trace element imbalance in the body. Conclusion: The risk of trace element imbalance due to occupational allergic diseases is associated with impaired copper and zinc balance. Our findings prove that the levels of microelements are additional factors that aggravate the course of occupational allergic disorders.

Regular reflection of shock waves in steady flows: viscous and non-equilibrium effects

Numerical analysis of a steady monatomic gas flow about the point of the regular reflection of a strong oblique shock wave from the symmetry plane is conducted with the Navier–Stokes–Fourier (NSF) equations, the regularized Grad 13-moment (R13) equations and the direct simulation Monte Carlo (DSMC) method. In contrast to the inviscid solution to this problem completely defined by the Rankine–Hugoniot (RH) relations, all three models predict a complicated flow structure with strong thermal non-equilibrium and a long wake with flow parameters not predicted by the RH relations. The temperature $T_y$ related to thermal motion of molecules in the direction normal to the symmetry plane has a maximum inside the reflection zone while in a planar shock wave the maximum is observed for the $T_x$ temperature. The R13 equations predict these features much better than the NSF equations and are in good agreement with the benchmark DSMC results. An analysis of the flow with the conservation equations was conducted in order to evaluate the effects of various processes on a fluid element moving along the symmetry plane. In contrast to the shock wave where effects of viscosity and heat conduction are one-dimensional with zeroth net contribution to the fluid-element energy across the shock, the flow across the zone of the shock reflection is dominated by two-dimensional effects with positive net contribution of viscosity and negative contribution of heat conduction to the fluid-element energy. These effects are believed to be the main source of the wake with parameters deviating from the RH values.

Splitting the spacetime: a systematic analysis of foliation dependence in cosmic averaging

It is a fundamental unsolved question in general relativity how to unambiguously characterize the effective collective dynamics of an ensemble of fluid elements sourcing the local geometry, in the absence of exact symmetries.In a cosmological context this is sometimes referred to as the averaging problem.At the heart of this problem in relativity is the non-uniqueness of the choice of foliation within which the statistical properties of the local spacetime are quantified,which can lead to ambiguity in the formulated average theory. This has led to debate in the literature on how to best construct and view such a coarse-grained hydrodynamic theory.Here, we address this ambiguity by performing the first quantitative investigation of foliation dependence in cosmological spatial averaging. Starting from the aim of constructing slicing-independent integral functionals (volume, mass, entropy, etc.) as well as average functionals (mean density, average curvature, etc.) defined on spatial volume sections, we investigate infinitesimal foliation variations and derive results on the foliation dependence of functionals and on extremal leaves.Our results show that one may only identify fully foliation-independent integral functionals in special scenarios, requiring the existence of associated conserved currents.We then derive bounds on the foliation dependence of integral functionals for general scalar quantities under finite variations within physically motivated classes of foliations.Our findings provide tools that are useful for quantifying, eliminating or constraining the foliation dependence in cosmological averaging.

Peak Acceleration Distribution on the Surface of Reef Islands under the Action of Vertical Ground Motion

This paper adopts the fluid–structure coupling algorithm based on the acoustic fluid element, the fluid dynamic artificial boundary, and the consistent viscoelastic artificial boundary of solid media to establish a finite element model of the dynamic interaction of the reef-island–seawater system. Then, a numerical simulation of the seismic response of the reef-island site is carried out to study the seismic ground motion distribution patterns of the reef–seawater site and the reef-island–lagoon site. The innovation of this article is that the influence of reef–island topography and fluid–structure coupling is considered in the analysis when vertical ground motion is input. The results show that the slope angle of the bottom layer has a significant influence on the peak ground acceleration distribution and peak size on the island slope surface and the reef platform. For high-frequency input motion, a smaller reef platform width will induce a larger peak acceleration response on the reef platform. Seawater has a significant suppressive effect on vertical ground acceleration. The more high-frequency components of the input bedrock motion, the more obvious this suppression effect will be. The existence of the lagoon will amplify the maximum peak acceleration on the reef platform. According to the calculation results, lagoon terrain can amplify the maximum horizontal and vertical peak accelerations on the reef platform by about 19 and 6 times relative to the free-field results, respectively.

The dynamics of accretion flows near to the innermost stable circular orbit

ABSTRACT Accretion flows are fundamentally turbulent systems, yet are classically modelled with viscous theories only valid on length scales significantly greater than the typical size of turbulent eddies in the flow. We demonstrate that, while this will be a reasonable bulk description of the flow at large radii, this must break down as the flow approaches absorbing boundaries, such as the innermost stable circular orbit (ISCO) of a black hole disc. This is because in a turbulent flow large velocity fluctuations can carry a fluid element over the ISCO from a finite distance away, from which it will not return, a process without analogy in conventional models. This introduces a non-zero directional bias into the velocity fluctuations in the near-ISCO disc. By studying reduced random walk problems, we derive a number of implications of the presence of an absorbing boundary in an accretion context. In particular, we show that the average velocity with which a typical fluid element crosses the ISCO is much larger than is assumed in traditional theories. This enhanced velocity modifies the thermodynamic properties of black hole accretion flows on both sides of the ISCO. In particular, thermodynamic quantities for larger ISCO stresses no longer display pronounced cusps at the ISCO in this new formalism, a result with relevance for a number of observational probes of the intra-ISCO region. Finally, we demonstrate that these extended models reproduce the trans-ISCO behaviour observed in GRMHD simulations of thin discs.

Evolution of the Angular Momentum of Molecular Cloud Cores in Magnetized Molecular Filaments

The angular momentum of molecular cloud cores plays a key role in the star formation process. However, the evolution of the angular momentum of molecular cloud cores formed in magnetized molecular filaments is still unclear. In this paper, we perform 3D magnetohydrodynamics simulations to reveal the effect of the magnetic field on the evolution of the angular momentum of molecular cloud cores formed through filament fragmentation. As a result, we find that the angular momentum decreases by 30% and 50% at the mass scale of 1 M ⊙ in the case of weak and strong magnetic field, respectively. By analyzing the torques exerted on fluid elements, we identify the magnetic tension as the dominant process for angular momentum transfer for mass scales ≲3 M ⊙ for the strong magnetic field case. This critical mass scale can be understood semianalytically as the timescale of magnetic braking. We show that the anisotropy of the angular momentum transfer due to the presence of a strong magnetic field changes the resultant angular momentum of the core only by a factor of 2. We also find that the distribution of the angle between the rotation axis and the magnetic field does not show strong alignment even just before the first core formation. Our results also indicate that the variety of the angular momentum of the cores is inherited from the difference in the phase of the initial turbulent velocity field. The variety could contribute to the diversity in size and other properties of protoplanetary disks recently reported by observations.

An interface tracking, finite volume code for modeling axisymmetric implosion of a rotating liquid metal liner with free surface

We present Integrated System Model-hydrodynamics (ISM-hydro)—an interface tracking, finite volume code for modeling a shaped implosion of a rotating, initially cylindrical, fluid shell (liner) with a free surface. The code is a novel implementation of the mixed Lagrangian–Eulerian approach, applied to a compressible fluid in an axisymmetric geometry described by cylindrical coordinates (r, ϕ, z). In ISM-hydro, a structured quadrilateral mesh follows fluid elements in the r-direction (radially Lagrangian) and is fixed in the z-direction (axially Eulerian). This approach accurately captures the motion of the liner's free surface, making it an interface tracking method. Using this mesh, we derive a finite volume discretization of the axisymmetric Euler equations for a rotating compressible fluid that has an exact balance of kinetic energy. An extensive comparison between ISM-hydro and the open-source software OpenFOAM is presented; results for different test cases show very good agreement in simulated implosion trajectories and flow fields. ISM-hydro is the purely hydrodynamic component of the Integrated System Model (ISM), a framework developed at General Fusion (GF) for comprehensive predictive modeling of GF's magnetized target fusion (MTF) scheme, where an imploding rotating liquid metal liner compresses a magnetized plasma target to fusion conditions. Among advantages of the code is its speed: a full implosion simulation with a coarse mesh takes on the order of one minute on a single core while preserving high accuracy. This makes ISM-hydro a valuable tool for the design optimization of GF's MTF machines.

Enhanced Estimation of Clamping-Force for Automotive EMB Actuators Using a Switching Extended State Observer

The automotive intelligence and electrification require the braking system to cooperate with the controller to achieve regenerative and active braking functions. Hence, the range and driving safety of the electric vehicles are improved. Electromechanical Brake (EMB) systems completely abandon the fluid and hydraulic elements and replace the traditional hydraulic braking system with a wire harness and electromechanical parts. The braking torque adjustment is achieved entirely by controlling the four-wheel EMBs. At present, reliability and fault tolerance are the key technical issues associated with EMBs. To eliminate the need of any clamping-force sensor due to its vulnerability and high cost, in this paper, a switching extended state observer (SESO) is presented to provide rapid force estimation with higher precision. The substrates of the internal linear and nonlinear structures have been unified into a single form by using an equivalent gain method. The SESO is effective to detect the initial contact between the braking disk and pad by estimating the load torque. It is experimentally verified that the developed force sensorless control strategy is accurate and superior to the existing techniques.