Field Characteristics Research Articles

Numerical Simulation of the Unsteady Airwake of the Liaoning Carrier Based on the DDES Model Coupled with Overset Grid

The wake behind an aircraft carrier under heavy wind condition is a key concern in ship design. The Chinese Liaoning ship’s upturned bow and the island on the deck could cause serious flow separation in the landing and take-off area. The flow separation induces strong velocity gradients and intense pulsations in the flow field. In addition, the sway of the aircraft carrier caused by waves could also intensify the flow separation. The complex flow field poses a significant risk to the shipboard aircraft take-off and landing operation. Therefore, accurately predicting the wake of an aircraft carrier during wave action motion is of great interest for design optimization and recovery aircraft control. In this research, the aerodynamic around an aircraft carrier (i.e., Liaoning) was analyzed using the computational fluid dynamics technique. The validity of two turbulence models was verified through comparison with the existing data from the literature. The upturned bow take-off deck and the right-hand island were the main areas where flow separation occurred. Delayed detached eddy simulation (DDES), which combines the advantages of LES and RANS, was adopted to capture the full-scale spatial and temporal flow information. The DDES was also coupled with the overset grid to calculate the flow field characteristics under the effect of hull sway. The downwash area at 15° starboard wind became shorter when the hull was stationary, while the upwash area and turbulence intensity increased. The respective characteristics of the wake flow field in the stationary and swaying state of the ship were investigated, and the flow separation showed a clear periodic when the ship was swaying. Comprehensive analysis of the time-dependent flow characteristic of the approach line for fixed-wing naval aircraft is also presented.

Numerical simulation of flow field characteristics and pollutant transport under different ventilation modes

Numerical simulation of flow field characteristics and pollutant transport under different ventilation modes

Study on the Influence of Chord Length and Frequency of Hydrofoil Device on the Discharge Characteristics of Floating Matter in Raceway Aquaculture

To investigate the influence of the chord length and frequency of an oscillating hydrofoil device on the discharge characteristics of floating particulate matter, in this study, we take raceway aquaculture as an example and systematically compare and analyze the flow field characteristics of the hydrofoil device with different chord lengths and frequencies, as well as the sewage discharge performance of the raceway based on Computational Fluid Dynamics (CFD). The results indicate that in the particulate matter discharge process of raceway aquaculture, when the chord length and motion frequency of the hydrofoil device are 0.1 W (W is the width of the raceway) and 1.0 Hz, respectively, the anti-Karman vortex streets produced by the hydrofoil device are less affected by the wall, the flow field is the most uniform, the particulate matter discharge performance is the best, and the final floating particulate matter discharge rate reaches up to 99.09%. Adjusting the chord length of the hydrofoil can effectively ameliorate flow field reflux issues, enhancing the uniformity and flow performance of the flow field. When the chord length is 0.1 W, the uniformity of the flow field is optimal. When the chord length is 0.2 W, the flow performance of the flow field is superior. Increasing the frequency enhances the flow performance of the flow field, with an average increase of 0.1 Hz in motion frequency leading to a 19.42% improvement in the average velocity at the outlet. Based on this, we recommend the use of a hydrofoil device with a chord length of 0.1 W and a motion frequency of 1.0 Hz in the raceway aquaculture system to achieve optimal particulate matter discharge performance, providing a theoretical basis and practical guidance for using hydrofoil devices to improve the efficiency of floating particulate matter treatment in raceway aquaculture environments.

Interplay between music and mathematics in the eyes of the beholder: focusing on differing types of expertise

This study explored the unique connections between music and mathematics as perceived by four groups of experts: professional mathematicians and musicians, as well as teacher educators in these two fields. Using 2 × 2 study design, we studied four groups of participants, comprising theorists and educators from various Israeli universities. During semi-structured interviews, the study participants were asked about their views on the connections between mathematics and music. This study proposes a model of experts’ conceptions of the connection between mathematics and music, which is of descriptive and explanatory power. that reveals differences between the four groups of experts. Theoreticians in both disciplines highlighted Mathematics as a key tool for music analysis and creation. Musical educators emphasized the role of music as a tool for learning mathematics. All the study participants, independently of the field of their expertise, value structure, beauty, sense of wonder, freedom and creative thinking as characteristics of both fields. Additionally, all the experts hold conceptions of the importance of integrating music and mathematics into various discipline. This study opened new doors for future research wherein utilization of experts’ insights to craft integrated study modules of music and mathematics can be explored, a pursuit that carries substantial significance.

Electromagnetic wave propagation in Eddington-inspired Born–Infeld gravity space-time with topological defects

In this study, we focus on examining the characteristics of electromagnetic fields within a curved space-time background under the framework of Eddington-inspired Born–Infeld (EiBI) gravity, in the presence of a global monopole. We derived Maxwell’s vacuum field equations in this curved spacetime and obtained a set of linear differential equations for the electric and magnetic fields. After decoupling these equations, we solved for the analytical solutions of both the electric and magnetic fields using special functions. We then extended our analysis to the same EiBI-gravity framework, this time incorporating a cosmic string. Following a similar approach, we derived the first-order differential equations governing the electric and magnetic fields and obtained their analytical solutions using special functions. Our findings demonstrate significant influences of the global monopole, cosmic string, and the Eddington parameters on the behavior of electromagnetic waves in this curved space-time configuration with topological defects, resulting in notable deviations from the Minkowski flat space case.

Insights into the Mechanisms of Single-Photon and Two-Photon Excited Surface Enhanced Fluorescence by Submicrometer Silver Particles.

Surface enhanced fluorescence (SEF) based on noble metal nanoparticles is an effective means to achieve high sensitivity in fluorescence detection. Currently, the physical mechanism behind enhanced fluorescence is not fully understood. This paper measures the fluorescence signals of Dihydroporphyrin f methyl ether (CPD4) under both single-photon and two-photon excitation based on submicrometer silver particles with rough morphologies, achieving enhancement factors of 34 and 45 times, respectively. On this basis, by combining the radiative field characteristics produced by the silver particles, a stimulated radiation model of molecules is established to elucidate the changes in the molecular photophysical process when influenced by silver particles. Moreover, the fluorescence lifetime of the molecules was measured, showing that the presence of silver particles induces an increase in the molecular radiative decay rate, causing the fluorescence lifetime to decay from 3.8 ns to 3 ns. The results indicate that the fluorescence enhancement primarily originates from the submicrometer silver particles' enhancement effect on the excitation light. Additionally, the fluorescence signal emitted by the molecules couples with the silver particles, causing the local surface plasmon resonances generated by the silver particles to also emit light signals of the same frequency. Under the combined effect, the fluorescence of the molecules is significantly enhanced. The findings provide a theoretical foundation for understanding the fluorescence enhancement mechanism of silver particles, adjusting the enhancement effect, and developing enhanced fluorescence detection devices based on submicrometer silver particles, holding significant practical importance.

A Brief Review on the Emerging Role of Bacterial Pigments: From Industrial Uses to Novel Therapeutic Applications

Pigments produced by microorganisms are in high demand due to their safe, non-toxic, and biodegradable characteristics in both industrial and pharmaceutical fields. Using bacteria for pigment production offers several advantages, such as a short life cycle and ease of genetic modification. Numerous studies have highlighted that soil bacteria significantly contribute to the production of coloured pigments as secondary metabolites. Bacterial pigments are well-known for their antimicrobial, antioxidant, and anticancer properties, offering new therapeutic opportunities for the development of novel drugs. However, compared to fungal pigments, most bacterial pigments are still in the research and development stage. Hence, efforts to intensify bacterial pigment production are essential to make them readily available on the market at a low cost for various applications. This review article sheds light on bacterial pigments and their various applications based on the data available in the literature.

Implementation of a Highly Mobile UAVs Direction Finding Complex Using Virtual Magnetic Dipoles

Relevance. In the context of the development of modern broadband communication systems, the task of performing direction finding of signals using highly mobile direction finding systems (UAVs) is becoming especially urgent. They impose restrictions on the size of antenna elements and the distance between them, which leads to an increase in the mathematical error of the bearing. Problem statement. The paper sets the task of considering the possibility of increasing the direction finding accuracy of a highly mobile complex by using virtual magnetic dipole technology. A feature of this method is the minimization of distortions introduced by the carrier body into the characteristics of the measured field. To measure the field characteristics, as well as their partial components, vector antenna elements were used. Goal of the work is to study the characteristics of a radio direction finding complex using virtual magnetic dipole methods in conditions of distortions introduced by the carrier body. As an example, cases of direction finding of differently polarized waves, taking into account the influence of radomes of antenna elements, assessment of the maximum resolution accuracy, as well as noise stability are considered. The finite element method implemented in DS CST Studio Suite 2024 was used in the modeling. Result. During the research, a plane wave with different bearings fell on a UAV with a direction finding complex, which made it possible to carry out the most accurate research. The results of the work also include the creation of a model of a radio direction finding complex, which can be installed on a small UAV, providing high accuracy of wave direction finding in passive mode.The novelty of the method used lies in the application of methods for the formation of virtual magnetic dipoles based on the measured characteristics of the distorted electric field. New to this work are modeling cases that are associated with noise suppression, the influence of antenna element housings, as well as assessment of the maximum resolution accuracy.Practical significance of the work lies in the creation of a model of a radio location system based on vector antenna elements, which are used to measure the characteristics of the electromagnetic field with subsequent direction finding based on the magnetic field.

Research on the Collection Characteristics of a Hydraulic Collector for Seafloor Massive Sulfides

Ore collection is very important in deep-sea mining for seafloor massive sulfide (SMS). In view of the characteristics of SMS ores produced by mechanical crushing, which contain coarse particles and a wide particle size distribution, in-depth research on the collection process with a device combining a rotary crushing head and a flat suction mouth was conducted. In this paper, solid–liquid two-phase flow in the hydraulic collection process with a drum rotation is carried out using the computational fluid dynamics-discrete element method (CFD-DEM), and the flow field characteristics and particle motion characteristics are analyzed. The results indicate that particles with a maximum diameter of 20 mm can be effectively collected when the suction velocity is 3 m/s. The collection process of SMS mainly goes through three stages: particle disturbance start-up, partial particle influx, and stable collection. In addition, the appropriate drum speed facilitates the collection of SMS ore. Finally, the correctness of the numerical method was assessed using similarity experiments. This work can be used to guide the design of underwater mining equipment.

Innovative configurations for heat sink integrated with piezoelectric fans

Piezoelectric (PE) fans are gradually replacing conventional axial flow fans in the field of heat dissipation for microelectronics due to small size and high efficiency. However, the flow characteristic of PE fans was seldom considered when arranging heat sink fins, which could not utilize the fans’ advantages. Here, the design of fin arrangement based on the transient flow field generated by the vibration of dual PE fans in the channel was calculated and analyzed by CFD simulation and dynamic grid technology. Four zones with different flow field characteristics were found: Zones 1 and 4 which located inlet and outlet of the channel were Parallel flow zone. Zone 2 with vortices corresponds to the area ranges from the waist of blades to middle section of the channel was Multiple vortices flow zone. Zone 3 with high-speed vortices and jet flows corresponds to the area ranges from middle section of the channel to halfway downstream of blades region was Diffuse flow zone. Innovative configurations of heat sinks where fins arranged at the inlet and surrounding blades were designed according to the flow field characteristics: the loss of high-speed airflow to the inlet was prevented effectively and heat dissipation in the downstream heat sinks was dispersed by fins arranging in Parallel flow zone and Multiple vortices flow zone. The development and merging of high-speed vortices were strengthened by the inhomogeneous pin-fins arranging in Diffuse flow zone. The optimal coordination between the velocity field and the temperature gradient field among innovative configurations was found based on the field coordination analysis. Heat transfer performance was enhanced by new designs where the average temperature compared to conventional heat sink with PE fans was reduced by 16.7°. Our work provided a new fins arrangement to achieve uniform temperature distribution and high heat transfer performance for heat sink integrated with PE fans and would benefit the application in thermal management of high power devices integrated with PE fans.

Numerical analysis on flow field characteristics and particle deposition distributions of DPF channels with different lengths based on lattice Boltzmann method

The pore scale model considers the porous structure and can fundamentally elucidate the filtration dynamics inside the DPF. In this paper, a developed two-dimensional pore scale model based on lattice Boltzmann method is adopted. A new determination method for soot particle threshold value is proposed. Flow field characteristics along different streamlines are analyzed. Particle cluster distributions and their effects are analyzed. The results show for streamlines close to the porous wall, the inlet contraction pressure drop and the outlet channel pressure drop account for a higher proportion and dominate the total pressure drop. It is necessary to focus on reducing the resistance along the last 1/5 of total outlet channel length. Near the particle deposition area, inlet channel pressures increase and outlet channel pressures decrease, creating a low-pressure area. Soot particles tend to deposit in the middle part of the channel when considering the effect of particle dynamic deposition.

Observation of tapered multicore fibers based on Nb2CTx for humidity sensing: Experiment and DFT simulation investigations

Recent advancements in the area of human healthcare monitoring and medical diagnosis have sparked a revived interest in humidity sensors. Nb2CTx, characterized by its multilayered structure, large specific surface area, and plentiful hydrophilic groups, actively absorbs a sufficient quantity of water molecules. In this work, the sensing capability and mechanism of water molecules are investigated under different proportions of functional group distribution on the surface of Nb2CTx MXene employing plane-wave based density functional theory calculations, and the provided models can offer guiding principles for the experimental preparation of the highly sensitive humidity sensor based on Nb2CTx. To verify the effectiveness of the model, Nb2CTx material is coated on a Tapered Three-Core Fiber (TTCF), and the high evanescent field characteristics of the sensor are utilized to further improve its performance. As the relative humidity (RH) increased from 35 % to 75 %, the transmitted spectra exhibited a redshift with a sensitivity of 22pm/% RH. Within the relative humidity range of 75 % to 95 %, the Nb2CTx coating heightened water molecule absorption, resulting in a more pronounced redshift in the transmitted spectra. This phase manifests a maximum humidity sensitivity of 299pm/% RH. Noteworthy advantages of this sensor include its uncomplicated structure, cost-effectiveness, and robust stability, rendering it highly suitable a wide variety of potential applications in fields such as biology, chemical and health processing.

Study on Wind Farm Flow Field Characteristics Based on Boundary Condition Optimization of Complex Mountain Numerical Simulation

The accurate prediction of the flow field characteristics of complex mountains is of great practical significance for the development and construction of wind farms, but it is not yet fully understood. The main purpose of this study is to propose a method for the study of flow field characteristics under complex mountain conditions, which can optimize the boundary conditions required for numerical simulation through the wind acceleration ratio and, at the same time, couple the numerical simulation and wind measurement data to reflect the real mountain flow field distribution. The results show that the proposed method has good applicability in complex mountain wind farms, can reproduce the real flow field distribution, and has a certain practical value. Wind speed distribution and turbulence intensity are greatly affected by boundary conditions such as wind speed and wind direction and are also affected by the shielding effect brought by terrain changes. The contrast between 120° and 150° wind direction is more obvious. When the incoming wind moves to the top of a mountain or the ridgeline, it will form a low-speed wake area behind it, resulting in reduced wind speed, increased turbulence intensity, and an unstable flow field.

Fully-Coupled Electric-Thermal-Flow Modeling and Investigation of Dynamic Thermal-Ledge Behavior in Aluminum Electrolysis Cell

Aluminum electrolysis cells (AECs) require effective thermal regulation to operate flexibly alongside renewable energy sources. Prior to implementing thermal regulation strategies, it is essential to predict the dynamic variations in the thermal field and ledge characteristics of a full-scale cell. This study introduces a transient electro-thermal-flow coupling model for a full-scale AEC, aimed at investigating the interactions between ledge distribution and various operational fields, including thermal, electric, and flow fields. The model facilitates the calculation and assessment of the dynamic properties of the ledge and thermal balance under ±15% flexible current variations. Results indicate that during a current increase, ledge melting predominantly occurs in the electrolyte layer, while ledge solidification is primarily observed in the metal layer during a current reduction. Regions with a thicker ledge and faster velocity tend to melt more during current increases and are less likely to return to their original shape and thickness during current reductions, complicating the rapid restoration of thermal equilibrium. To achieve uniform ledge distribution and real-time adaptation to flexible current variations, it is recommended to install distributed cooling devices on the sides of the AEC to enable differential ledge regulation at various locations.

Squeezing characteristics of cavity field in dynamic Casimir effect

The dynamic Casimir effect refers to the phenomenon of photons generated in a cavity with periodically vibrating wall. The Hamiltonian of the dynamic Casimir effect includes the square term of the photon creation (annihilation) operator, which connects to the squeezing light. Here we discuss in detail the squeezing characteristics of the cavity field in the dynamic Casimir effect. When the cavity wall is driven classically, semi classical theory is adopted; When cavity wall vibration needs to be described by phonons, full quantum theory is used. The squeezing properties of the light field are different according to these two theory. In semi classical theory, the squeezing properties depend on the system parameter |B/A|. When |B/A|>1, the squeezing value changes periodically, and the squeezing weakens as |B/A| increases. When |B/A|<1, it is necessary to use optimized squeezing value to measure squeezing, which shows steady value of −0.25. In full quantum theory, we find that the squeezing of the cavity field weakens as the initial average phonon number decreases. This is because the smaller the average phonon number, the more pronounced the quantum properties of cavity wall vibration. During evolution, phonons and photons become entangled, disrupting the squeezing of the cavity field. The quantum properties of phonons have a negative impact on the squeezing of the light field. We also found that in full quantum theory, the optimized squeezing value should be used to better describe the squeezing, and the maximum squeezing can be achieved by controlling the initial average phonon number of the cavity wall without photon divergence. Most studies focus on resonance frequency, so the innovation points of this paper are of the large detuning frequency.. This work has significance for a deeper understanding of the quantum properties of the cavity field in the dynamic Casimir effect, and helps to generate squeezing microwaves using the parameter dynamic Casimir effect.

Study on the influence of high-temperature thermochemical nonequilibrium effects on the flow field characteristics around shaped wing

With advances in research on hypersonic vehicles, the precise simulation of the effects of thermochemical non-equilibrium has become increasingly important in their design. In light of this, this study explores the influence of high-temperature thermochemical non-equilibrium on the characteristics of the flow field around the hypersonic wings of an aircraft. We initially conducted a numerical simulation by using the model of flow through a cylinder to validate the accuracy and reliability of an 11-species gas model in representing high-enthalpy flow fields. Subsequently, a systematic analysis was conducted on the impact of thermochemical nonequilibrium effects on the temperature, pressure, and enthalpy distribution in the flow field around a symmetric diamond wing under different Mach numbers and angles of attack. The research results indicated that the deeper reason behind the differing thermochemical nonequilibrium effects in the flow field at various Mach numbers lies in the distinct distribution of enthalpy of the air components at different locations, which provided a new perspective for understanding flow field variations from the standpoint of enthalpy. It is disclosed that the thermochemical non-equilibrium significantly altered the characteristics of the flow field, particularly at high Mach numbers and angles of attack, with a significant impact on the aerodynamic parameters of both the windward and the leeward sides of the wing. Through explaining the mechanisms of thermochemical non-equilibrium under flow fields with different structures, this study provides a theoretical foundations for and a fresh perspective on the design of hypersonic vehicles.

Experimental study of rotating direction for dual-axial swirlers on the flow field and combustion characteristics of aero-engine combustor

The flow field structure for aero-engine combustor is one of the most important factors for combustion performance. To investigate how the rotating direction of dual-axial swirlers affects the flow field and combustion characteristics, particle image velocimetry (PIV) experiments were conducted in the primary combustion and intermediate zones. Additionally, planar laser induced fluorescence (PLIF) was used to map the distribution of kerosene and OH in the primary combustion zone. The results show that the swirling jets in co-swirl exhibit greater jet momentum, resulting in a longer primary recirculation zone and a larger deflection angle of the primary jets. This ultimately leads to a higher recirculation rate compared to counter-swirl. The primary jets define the boundary of the flow field structure. The rotating direction primarily affects the flow field structure upstream of the primary jets, exerts a relatively weaker influence on the intermediate zone, which is mainly affected by the deflection direction of the primary jets, and essentially has no impact on the dilution jets. Co-swirl has a relatively stable flow field than counter-swirl, whereas the flow field in counter-swirl is more chaotic, featuring a greater number of vortex cores in the primary recirculation zone. The coupling between the primary and swirling jets affects the mass transfer direction in the intermediate zone, which is reflected in the fact that the mass transfer is from top-left to bottom-right in co-swirl, while it is in the opposite direction in counter-swirl. OH is predominantly found in the swirling shear layers, the primary and secondary combustion zones, whereas kerosene is mainly concentrated in the shear layers of swirling jets. The kerosene distribution in co-swirl shows a larger and more concentrated expansion angle compared to counter-swirl. In contrast, the OH distribution downstream of counter-swirl is broader, with more intense combustion due to enhanced kerosene decomposition and fuel-air mixing. The smaller primary recirculation zone in counter-swirl forces the primary combustion zone to extend downstream, leading to a more intense reaction in the secondary recirculation zone.

The Research on Self-Excited Oscillating Jet Cleaning Technology

Abstract Self-oscillating nozzles have gained wide popularity due to their ability to generate powerful impact forces, long-range projection, and concentrated, stable jets in applications such as water-jet drilling and rust removal. However, the nozzle’s efficient operation relies heavily on specific structural designs and operational parameters, which necessitates further indepth research. By studying the characteristics of self-excited oscillating pulse cavitation jet within the nozzle cavity structure. Analyzing the evolution characteristics of internal flow field. Solving optimization problems in a targeted manner. The purpose of this study is to reveal the resonance principle behind the self-excited oscillation of nozzle. It also explores the regularities of the effects that the cavity diameter has on jet performance, ultimately seeking to find the optimal configuration of nozzle structure and operating conditions.

Acoustic fields to levitate big water drops

Abstract In this report, we described the main characteristics of acoustic fields allowing the levitation of big water drops. A numerical study is presented for different configurations of levitators and their associated acoustic fields. It is shown that an emitter different to a piston-type source, for instance, a circular plate excited in its center, vibrating at its first axisymmetric eigenmode can produce an acoustic field with improved levitation capabilities.

Study on the evolution of heterogeneous double-cavity induced by near-wall and the fluctuation characteristics of load field

It is well known that the collapse of heterogeneous multi-cavity near the wall will induce the fluctuation of the load field. To address this problem, the Lattice Boltzmann Method (LBM) is applied to model the three-phase coupling between gas-liquid-solid. The objective is to investigate the evolution of heterogeneous double bubbles and the spatial-temporal distribution characteristics of wall loads induced near the wall. In this study, the pseudopotential Multi-Relaxation-Time Lattice Boltzmann Model (MRT-LBM) and the Carnahan-Starling Equation of State (C-S-EOS) with an extended format for the external force term are used. The effects of the distance of the bubble to the wall, the pressure differences between the inside and outside of the bubble, and the relative size of the bubble on the dynamic evolution and the load distribution characteristics of heterogeneous multi-bubbles near the wall are investigated in order to determine the influence of these factors. Under a two-dimensional pressure field, the collapse process of double cavitation bubbles is visualized. Through the flow field, the morphological changes of the cavitation bubble collapse near the wall are also described. Various parameters are found to have an influence on the evolution of double cavitation bubbles near the wall and the resulting load field. The study employs the Lattice Boltzmann Method and the Potential Model for the analysis of the heterogeneous bubble collapses in the near wall region.