bluuebunny/crossref_metadata_2025 huggingface dataset:
Neural network module for tuning an atomic force microscope in the study of photonic crystal films
Authors: Panfilova E V , Ibragimov A R , Mozer K V
Published: August 2020

The article describes the use of neural network algorithms for setting the modes of investigation of photonic crystal films by tapping mode of atomic force microscopy. The photonic crystal thin films and monolayers obtained from colloidal suspensions by methods of sedimentation, centrifugation, vertical deposition, electrophoresis, and Langmuir-Blodgett are studied in this work. Study of films growth kinetics revealed that many factors were critical for reproducible deposition of the structure. To obtain high-quality images of samples, it is very important to get rid of artifacts and correctly configure the scanning parameters. To solve these problems it was proposed to use neural network algorithms. They allow to choose individual settings for each sample. We got acceptable results using a multilayer perceptron with one hidden layer.
Blister-based laser-induced forward transfer of 1D and 2D carbon nanomaterials
Authors: Dezhkina M.A. , Komlenok M.S. , Pivovarov P.A. , Rybin M.G. , Arutyunyan N.R. , Popovich A.F. , Obraztsova E.D. , Konov V.I.
Published: August 2020

The possibility of laser printing of single-walled carbon nanotubes (SWCNTs) and graphene via blister-based laser-induced forward transfer technique is demonstrated. Laser radiation with optimized fluence, that is absorbed in a thin aluminium film, causes its local evaporation and blistering without rupture, which leads to the ejection of carbon nanomaterial from the donor to the receiving substrate. The use of preliminary cutting of the donor layer into square pixels allows printing SWCNTs while maintaining their shape. Raman analysis indicates the transfer of carbon nanomaterials without significant degradation.
Generation of sub cycle terahertz pulses via coherent control of nonlinear medium by femtosecond pulses
Authors: Arkhipov R M , Arkhipov M V , Pakhomov A V , Babushkin I , Demircan A , Morgner U , Rosanov N N
Published: August 2020

In this paper, we revise our recent advances in study of high-efficient methods of sub cycle THz pulse generation and control of their wave shape. These methods are based on coherent control of low frequency oscillations in nonlinear medium excited by infrared femtosecond pulses. Our results showed the possibility of sub – and few-cycle pulse formation of controllable wave shapes: half-cycle, rectangular and triangular and single-cycle ones in THz, XUV and optical ranges.
In vitro investigation of laser-induced microgrooves on titanium surface
Authors: Veiko V P , Karlagina Yu Yu , Egorova E E , Zernitskaya E A , Kuznetsova D S , Elagin V V , Zagaynova E V , Odintsova G V
Published: August 2020

We developed a surface design that imitates the osteon structure of human bone tissue to improve the bio-integration of a titanium implants. Two types of subcellular-sized microgrooves were formed on VT6 (analogue 6Al-4V) titanium surface by laser processing: closed and open microgrooves. An in vitro study of the proliferation of human bone marrow mesenchymal stem cells on the formed structures was carried out, osteogenic differentiation was studied.
Choosing the optimal parameters of reconstruction for the shape sensor based on multicore spun optical fiber
Authors: Bronnikov K A , Wolf A A , Dostovalov A V , Babin S A
Published: August 2020

Multicore optical fibers are widely used for developing compact shape sensors for various applications. The accuracy of such sensors strongly depends on the resolution of the measured data. In this paper, we analyze the influence of the number of sensing points on the error and mean time of reconstruction of the multicore fiber shape. A criterion on the choice of this parameter is given considering the impact on the performance.
Blueshifts of high-order harmonic generation in crystalline silicon subjected to intense femtosecond near-infrared laser pulse
Authors: Obreshkov Boyan , Apostolova Tzveta
Published: August 2020

We present the generation of high order harmonics in crystalline silicon subjected to intense near-infrared 30fs laser pulses. The harmonic spectrum extends from the near infrared to the extreme ultraviolet spectral region. Depending on the pulsed laser intensity, we distinguish two regimes of harmonic generation: (i) perturbative regime: electron-hole pairs born during each half-cycle of the laser pulse via multiphoton and tunnel transitions are accelerated in the laser electric field and gain kinetic energy; the electron-hole pairs then recombine in the ground state by emitting a single high-energy photon. The resultant high harmonic spectrum consists of sharp peaks at odd harmonic orders. (ii) non-perturbative regime: the intensity of the harmonics increases, their spectral width broadens and the position of harmonics shifts to shorter wavelengths. The blueshifts of high harmonics in silicon are independent on the harmonic order which may be helpful in the design of continuously tunable XUV sources.
Study of the functioning time of aluminosilicates for the formation of hydrophobic surfaces
Authors: Barón G C , Montaño A M , González C P
Published: August 2020

The modification of surfaces for the creation of hydrophobic materials has grown in recent years due to the wettability properties that can be obtained, in this process the chemical environment of the surface is modified. In the case of aluminosilicates, surfaces are generally considered polar, so it is of great interest to create hydrophobic surfaces through the functionalization process, obtaining low wettability; hydrophobicity is determined when a surface comes in contact with a drop of an organic component and contact angles greater than 90 ° are obtained. The present work describes the results of the study of the contact time between aluminosilicate surfaces and a siloxane as a functionalizing agent, to determine the optimal time in which hydrophobic surfaces are obtained. The results show that after 3 hours of contact between the surface and the functionalizing agent, a surface with a contact angle of 106° is generated, due to the heterogeneous surface of the functionalizing agent that is generated in the aluminosilicate because of the polymerization reaction.
Geopolymer derived from bentonite: Structural characterization and evaluation as a potential sorbent of ammonium in waters
Authors: Jaimes J E , Montaño A M , González C P
Published: August 2020

In this work, a Colombian sodium bentonite geopolymer, montmorillonite type, activated with commercial sodium silicate, was synthesized for its later use as sorbent material of ammonium cations in leached waters from soils treated with PINAL, an ammonia-based herbicide of glufosinate used to eradicate the use of illicit crops. The raw material and geopolymer obtained are characterized by the Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy technique, to determine the structural difference between the bonds created during the geopolymerization process, as well as to know the transformation of the crystalline phases of the material. Through this analysis and study of dispersion spectroscopy, it was possible to establish the effect of the eliminated ammonium cation on the structure of the geopolymeric material and propose a sorption mechanism, in addition, an improvement in the removal capacity of these ions from the geopolymeric material was observed.
Evaluation of the rheological properties in solution and molten state of hyperbranched polyester polyols obtained of first and second generation
Authors: Murillo E A
Published: August 2020

The hyperbranched polyesters have gain great attention since these materials have smallest hydrodynamic dimensions, high functionality, good solubility and they may be modified for obtaining compounds for specific applications. There are few reports about the rheological properties on the solution and molten state of the hyperbranched polyesters polyols obtained of the first and second generation, especially those prepared from dimethyl propionic acid and pentaerythritol. Thus, the aim of this study is to evaluate the rheological properties in solution and molten state of these materials. Furthermore, the hydrodynamic dimensions by dynamic light scattering by using dimethyl formamide and dimethyl sulfoxide as solvents also were analyzed. The hydrodynamic dimensions on volume of the hyperbranched polyesters polyols obtained of second generation by using dimethyl formamide as solvent were greater than those of first generation, but the behavior was different when was used dimethyl sulfoxide as solvent. Furthermore, these materials exhibited aggregations. The rheological behavior in solution showed that all samples exhibited lowest viscosity and a Newtonian region between 1 and 60 s−1, then this behavior changed to shear thickening. By rheological analysis in molten state was evidenced a shear-thinning behavior to these materials.
Simulating hydrodynamics in a Rushton turbine at different stirring velocities applied to non-Newtonian fluids
Authors: Gelves G
Published: August 2020

In this work, gas-liquid hydrodynamics of a Rushton turbine was studied using Computational Fluid Dynamics. Different stirring conditions commonly used in fungal culture applications are simulated. Several scenarios are predicted related to gas-liquid mass transfer limitation. The above, reflected by low air dispersion reached and bubble size determinations caused by the non-Newtonian rheology, leading the process to obtain kLa values only in the order of 30 h−1 at high, stirring speeds. However, the high-power consumption in fungal culture in agitated tank bioreactors can be disadvantages in large-scale prototypes applied in non-Newtonian fluids. These Findings shown in this research should be considered as a primary criterion for optimizing mass transfer problems in large scale fungal culture applications.
Mathematical model of physical process of heat transfer in liquid crystal
Authors: Nolasco C , Velascos Burgos B M , Cadena Morales J J
Published: August 2020

The process of heat transfer by conduction is relevant in different context of engineering and sciences. An example of this situation is confirmed by the study of the thermal properties of liquid crystal sheets to measure the effects of heat transfer on metal surfaces. The aim of this work is to establish a mathematical model by numerical methods to determine the physical process of heat transfer in liquid crystal. For the data acquisition, an experiment that measures thermal properties on an aluminum plate was designed. We proceed to propose a mathematical model that uses the Laplace equation. Also, we proceed to calculate the solution of the equation by the finite difference method and then make a comparison with the analytical solution and the experimental data.
Web services selection a perspective of computational physics
Authors: Adarme M A , Jimeno M A , Puerto E G
Published: August 2020

Concerning computational physics, web services are conceived as mathematical units that are experienced in different systems that offer service composition. Due to the exponential growth of web services and their deployment on cloud platforms, quality of service parameters have now become an essential factor when searching for and selecting services that must satisfy specific non-functional requirements of a user application. A variety of service components are highly configurable and are dynamic scenarios because a significant number of services can meet these requirements. This work analyzes the systemic perspective of approaches for the selecting and searching of web services that have specifications of optimization strategies based on the configurable quality of service parameters with test scenarios in cloud environments that have a considerable number of services as input. The study shows that policies based on artificial intelligence and related areas are the ones with the most significant convergence, and the approaches analyzed to give a perspective of future work aimed at strategies based on automatic learning.
Application of virtual technologies for the representation of physical phenomena in maintenance tasks
Authors: Dueñas Ramírez L M , Villegas López G A , Chamat Torres C P
Published: August 2020

Maintenance during industrial development has evolved, always seeking the in-depth study of the physical phenomena that occur in the elements and systems that have suffered functional failures. Maintenance has been adapted to each challenge presented. The progress and development of computer science have opted for the massive use of information and communication technologies that support industrial processes, generating new possibilities in maintenance management and operation. These tools could contribute to improving the efficiency of maintenance processes, taking into account that these costs represent a third of the total production cost in an organization. This work seeks to identify the evolution of these technological tools in the applications that they have had in representing the physical phenomena of maintenance management. This research also seeks to establish the minimum requirements that these tools must consider in their applications and uses. Considering the appropriation of these technologies in Colombia, in order to determine where the country is in terms of development and technological use, being important information for the recognition of the scenario and decision-making that prevail in a competitive Colombian industry world level.
Determination of connective heat transfer coefficients in an intermittent kiln
Authors: Guerrero Gómez G , Vera Duarte L E , Noriega Sánchez C J
Published: August 2020

The determination of heat transfer coefficients are parameters of great importance when evaluating thermal losses in a system. Therefore, the present work reports the convective heat transfer coefficients in different positions of a rectangular kiln for the production of artisanal ceramic materials, located in Ocaña, Norte de Santander, Colombia, from which the heat losses present in the were determined. As a result, a virtual instrument was designed for temperature acquisition, using a data acquisition card, as well as a chassis and thermocouples generating a temperature report and their respective temperature profiles. The determination of heat transfer coefficients are parameters of great importance when evaluating thermal losses in a system. The energy supplied by the fuel is 51.21 kJ and the energy loss in the walls and floor of the brick kiln is 17.67 kJ, which represents 34.51% of the energy supplied. The thermal gradient in the kiln is not homogeneous, affecting the quality of the products. This will be avoided by building the walls with refractory materials.
Physical-thermal straw properties advantages in the design of a sustainable panel-type construction system to be used as an architectural dividing element
Authors: Díaz Fuentes C X , Pérez Rojas M C , Mancilla J J
Published: August 2020

The walls in architecture determine the energy behavior of a home, the physical and thermal properties of the building elements are capable of controlling the energy transfer of to the interior, avoiding dependence on artificial cooling systems, which increase energy consumption. The research takes advantage of the physical-thermal attributes of straw, considering its use as a material, presenting sustainable constructive solutions for the walls configuration in rural houses with a warm tropical climate. The proposed design starts from identifying the properties of materials with a low carbon footprint such as straw, wood, cardboard, which are viable due to their low weight and easy obtaining. The result is the modular design of the EcoStraw panel that consists of a compressed straw matrix, embedded in a module whose function is to isolate the heat conduction between the interior and exterior, a modular and wooden support structure with the aim of giving structural stability in the stack and a cardboard laminate lining that acts as an interior closing surface. The constructive solution can be industrialized, economical and with a low impact on the environment.
Design of a high precision mechanical linear system for the study of the variables involved in the gas metal arc welding process
Authors: Lázaro Plata J L , Sánchez Rincón C S , Regino Ubarnes F J
Published: August 2020

The gas metal arc welding process is studied because of its high productivity and low cost. One of the drawbacks of this process is achieving repeatability of the welding seams. This article shows the design of a linear mechanical system that provided a high precision in the trajectory of the base platform. Three important factors were investigated such as platform speed, the main stresses present and the manufacturing material. A descriptive type methodology was used which consisted of conducting the study as a discrete particle system. The optimum conditions for the efficiency of its operation were a linear velocity of 1.44 mm/s, maximum shear stress in the power screw of 283.57 kPa, which was calculated by means of static analysis to determine as the material of medium carbon steel of type AISI 1040, which due to its ductility, facilitated the machining of the power screw. This provided a mechanical efficiency of 30.9%. The kinematic calculations of the system were made with standardized elements found on the market.
Testing stabilization of high-plasticity clays used in sloping terrain by adding sodium silicate
Authors: Flórez-Góngora C H , Garzón-Peña A T , Molina-Giraldo R D
Published: August 2020

High-plasticity clays can be stabilized by the addition of a small percentage of sodium silicate. Sixteen mixtures of 4000 g with different concentrations of sodium silicate at difference percentage were designed, to which were carried out physical, mechanical and chemical characterization tests that allowed to analyze the behavior at intervals of time. Physical, mechanical and chemical properties of the soil were evaluated. Using stabilization with sodium silicate in high plasticity clays, changes in the physical, mechanical, and chemical parameters of the soil were achieved. Having satisfactory results with 3% saturation, optimal concentration, at time intervals of 2 days and 1 month; Then as time passes the soil tries to return to its initial properties, which establishes that the concentration of the Silicate and its effect on the physical and mechanical properties of the soil should be checked over a longer time interval. Studying the physical, mechanical, and chemical parameters of high plasticity clays by adding multiples mixtures of sodium silicate contributes to the understanding of the soil behavior on the pressure condition.
Assessing wind and solar resources. Case study: department of Norte de Santander, Colombia, stage 1
Authors: Serpa Jimenez A M , Mogollon G , Gallardo Pérez H J
Published: August 2020

Renewable sources used to produce energy has gained momentum due to its environmental benefits and economic feasibility. Colombia has been part of the global tendency to develop non-conventional renewable technologies such as wind and solar and integrate those technologies into the energy matrix of the country. However, the lack of understanding of the wind and solar resources in some areas of the country including the department of Norte de Santander, Colombia, has limited the deployment of these technologies and the development of new projects. This research proposes an approach to assess wind and solar resources in the department of Norte de Santander, Colombia. Also, this paper discusses the physics behind the generation of energy from wind and solar sources and the contributions required from different backgrounds to help in the wide deployment of solar and wind energy. In this first stage, a rough technical concept is developed, and the proposed sites are selected based on publicly available maps of low resolution presenting average irradiance and wind speed, and proximity to electricity transmission infrastructure. The areas selected have a global horizontal irradiance ranging from 4.0 kWh/m2 to 5.0 kWh/m2 and wind speeds between 4.0 m/s and 6.0 m/s at 10.0 m height on average in a year.
Numerical Analysis of Inner Flow Loss Evolutions in a Low-Aspect Ratio Transonic Compressor Rotor at Windmilling Conditions
Authors: Li Da
Published: August 2020

This paper conducts a detailed numerical investigation to study the evolutions of flow topology and aerodynamic losses in a low-aspect ratio compressor rotor operating from freewindmill condition (near stall point) to highly loaded windmill condition (near choke point). Firstly, a simplified numerical calculation method based on energy transfer between rotor blade and working fluid is employed to capture the windmill points at low rotational speeds. Then, the influences of windmill on tip leakage loss are analyzed. At windmilling conditions, the tip leakage flow travels across the clearance from suction to pressure side and causes blockages near the pressure surface in the casing end-wall region, which is quite different from the flow phenomenon at freewindmill conditions. Finally, the influences of windmill on flow separations are investigated. In tip region, with the rotor operating from freewindmill to highly loaded windmill condition, the flow separation switches from suction surface separation to pressure surface separation, and both the intensity and size are increased. Unlike near the tip, the hub separations always appear on the suction surface and a radial growth is observed near the trailing edge at the highly loaded windmilling condition, which is not presented at both the near stall and windmill points.
Research on overflow diffusion characteristics of dredger
Authors: Shao Mingqi , Wang Jin , Ding Xuewen
Published: August 2020

Dredging engineering is widely used in port and waterway construction, water conservancy facilities construction, environmental protection dredging, land reclamation, subsea tunnel excavation and deep-sea mining, among which drag suction dredger is an important tool for dredging operation. During the process of its construction, the mud overflow process is an important link to realize the mud treatment of excavation. According to the actual engineering conditions, the loading and overflow process is an important part of the treatment of excavated slurry. With the increasing requirements of environmental protection, the related ecological pollution caused by dredging has become a hot spot today, and the diffusion of overflow slurry is one of the sources of pollution generated by dredging suction dredgers. Therefore, combining with actual engineering conditions, this paper adopts the theory of computational fluid dynamics (CFD) to study the diffusion characteristics, diffusion range, and influencing factors and proposes construction strategies to reduce its pollution impact.
Aero-thermal-elastic Coupled Simulations of An Air-cooled Turbine with an FDM solver
Authors: Guo Zhaoyuan , Wang Qiang , Dong Ping , Jiang Yuting
Published: August 2020

The aero-thermal-elastic coupled simulations of an air-cooled turbine vane were carried out by a developed coupled solver, HIT3D, employing the finite difference method. The pressure on the vane surface and the temperature in the solid vane were obtained by the coupled heat transfer simulation, then the single-way aero-elastic and thermal-elastic analysis on the turbine vane were performed. It shows that the predicted profile temperature employing the transition model agrees well with the measured one, the blade deformation caused by aerodynamic force is negligible, and that the greater thermal deformation and thermal stress locate at the blade leading edge pressure side and at the blade trailing edge, as the result of the strong temperature gradient and the constraint at the vane endwalls.
Study of a quantitative characterization parameter “oil and gas producing efficiency” of the producing degree of reserves in the developed area
Authors: Dai Jinyou , Wang Rui
Published: August 2020

Implementing the producing degree of reserves in the developed area is of great significance for timely understanding of oil and gas development trends in the developed area, and then taking targeted adjustment measures to improve oil and gas producing efficiency. On the basis of the analysis of different scale pore percolation capacity of reservoir and the study of four kinds of porosity (connected porosity, effective porosity, flowing porosity, filling porosity) and their corresponding calculation models of oil saturation, a quantitative characterization parameter - “oil and gas producing efficiency” of the producing degree of reserves in the developed area is proposed, and its theoretical discussion and case analysis are carried out. Research shows: 1) Oil and gas producing efficiency is the ratio of the reserves involved in percolation to geological reserves in the developed area of the oilfield, which is finally expressed as the ratio of the product of the flowing porosity and the original oil saturation of the flowing pores to the product of the connected porosity and the original oil saturation of the connected pores. 2) Reservoir flowing porosity and the original oil saturation of flowing pores are a function of displacement power, while the original oil saturation of connected pores is a function of reservoir forming power. Therefore, the oil and gas producing efficiency is essentially a coupling function of displacement power and reservoir forming power. 3) When the displacement power is greater than the reservoir forming power, the oil and gas will be fully developed, and the oil and gas producing efficiency will be 1; when the displacement power is less than the reservoir forming power, the oil and gas will be partially developed, and the oil and gas producing efficiency will be less than 1. 4) The calculation examples of X oilfield in Ordos Basin show that the connected porosity is 11.2%, the original oil saturation of the connected pores is 57.1%, the flowing porosity is 5.32%, the oil and gas producing efficiency is 0.832, and the oil and gas are partially developed. If the oil and gas are to be fully developed, the production pressure difference can be increased from 4.1MPa to 6.2MPa. 5) The study of oil and gas producing efficiency deepens the understanding of reserves producing status in the developed area of the oilfield, and has guiding significance for the targeted production adjustment and production pressure difference optimization of the oilfield.
Numerical investigations on influence of spacing of tidal current turbine array
Authors: An Qi , Wu Shuang , Liu Yanjun
Published: August 2020

In order to maximize the energy extraction potential from the marine resource, the primary task is to improve the power generation efficiency of multi-unit turbine arrays. There are many factors that affect the power generation efficiency of hydro turbine arrays. This paper mainly studies the influence of the effects of array structure parameters on the flow structure of the near-wake flow field and the energy utilization. The numerical simulation results are compared with the experimental data to verify the reliability of the numerical model. The double-row staggered arrangement of the turbine array is selected, and the size of the array structure parameter, the horizontal distance Dx and the vertical distance Dy, is changed to calculate a series of working conditions. The analysis of the results shows that when the horizontal distance Dx is 2.5RD and the vertical distance Dy is 2RD, the energy efficiency of the turbine array will reach the highest.
Research on the Pulsed Eddy Current Sensor of the Crack Depth of Turbine Disk
Authors: Xia Liu , Liu Lihui , Chen Dixiang
Published: August 2020

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Investigation of store separation characteristics by leading edge spoilers before supersonic cavity
Authors: Cui Pengcheng , Li Bin , Tang Jing , Chen Jiangtao , Li Huan , Mingsheng Ma
Published: August 2020

The internal cavity is widely used on new generation aircraft. However, there are some new aerodynamic and acoustic issues accompanied with the internal cavity. Store separation is a challenge when separated from a high-speed cavity, the store usually generates nose-up pitch moment due to the separated flow and large static pressure gradient, which is a threat to store separation safety. Leading edge spoiler is an effective passive flow control method to improve the store separation characteristics, however the effects of varisized leading edge spoiler on store separation characteristics are still unknown. In this paper, a parameterized leading edge spoiler model is established to investigate the store separation characteristics by leading edge spoilers flow control before supersonic cavity, a small aspect ratio fly-wing aircraft and a simplified store model are employed to simulate the store separation characteristics. Numerical results show that the leading edge spoiler lifts the shear layer and significantly changes the pressure distribution inside the cavity, which makes the store a nose down pitch angle during separation. The height of leading edge spoiler greatly influences the store separation characteristics for it changes the shear layer and vortex structure. The angle of spoiler and the gas between spoiler and aircraft also have great effects on store separation, larger angle and smaller gas lead to less nose-up angle.
The Point Interpolation Method for Static Analysis Using Quadratically Consistent Three-Point Integration Scheme
Authors: Chen Huihui , Jia Cheng , Gu Ying , Zhou Yujie , Ge Ziyu
Published: August 2020

The element free Galerkin method (EFG) is much interest in recent years due to its merits of only node information needed in constructing shape functions and high precision. However, its low computational efficiency becomes a technical issue in the simulation of realistic problems. To develop a more efficient and accurate method, the point interpolation method using quadratically consistent three-point integration scheme (PIM-QC3) is proposed, based on consistency framework for meshfree nodal shape function and its derivatives. And the shape functions along with corrected nodal derivatives at integration points, adopt quadratic basis, meet the differentiation of the approximation consistency (DAC) and the discrete divergence consistency (DDC). In addition, they possess Kronecker delta property and could enforce displacement boundary conditions simply. The T6-Scheme is utilized for node selection in constructing approximation, to avoid the singular moment matrix and make the computation of shape functions simple. Numerical results show the excellence of the proposed method in accuracy and efficiency of all tested methods. Specially, it is more efficient than three-point integration scheme based on element-free Galerkin method. The research in this paper could provide an efficient and reliable tool for analysis of engineering structure.
Quasi-static single bubble formation behaviour: interaction with adjacent induced flow structure
Authors: Zhao Ziwei , Hu Jun , Yu Yong
Published: August 2020

Single bubble formation behaviours which develops from submerged nozzle under the quasi-static mode in stagnant deionized water in a rectangular column are studied. Bubble formation behaviours are captured by a digital high-speed camera and information of the induced adjacent flow field is synchronously obtained via the particle image velocimetry (PIV) system. Interactions of induced bubble adjacent flow patterns with bubble formation behaviours are investigated at each stage of a three-stage bubble formation model. Results indicate that recirculation of the continuous phase near the bubble base accelerates rapid detachment of the bubble and the dynamic pressure variation in the liquid induced by bubble behaviours is the main reason why such flow pattern appears.
High-order simulation solving Navier-Stokes equations with Spalart–Allmaras turbulence model
Authors: Yang Li , Yue Lianjie , Zhang Qifan , Zhang Xinyu
Published: August 2020

The goal of this paper is to implement an accurate and robust solver for compressible Navier-Stokes equations coupled with the Spalart–Allmaras model, which possesses the capability of shock-capturing and predication of boundary layer and separated flow. In a given stencil width, a WENO-Z scheme equipped with Roe flux difference split method is used to calculate the inviscid flux, and central differencing scheme for the viscous terms are employed. The explicit Runge-Kutta is adopted for the temporal discretization. The simulation results of selected cases are given to verify the validation of the solver.
Measurements of velocity and droplet sizing in industrial applications using non-invasive laser systems
Authors: Lai W.T. , Zhang Xin , Yan T. , Xu D.
Published: August 2020

Many industrial applications involve the measurements of the velocity and size for the design of the products. Examples of such products are kitchen ventilator, water pump, household appliances and industrial oriented nozzles for fire suppression and paint. In the area of industrial safety, validation of the face mask for leakage is also an important aspect of the mask design. Fire suppression, paint nozzle, and mask filter are items which we encounter and rely on in our daily life. The design of products of those items to provide the best and optimal outcome is a critical aspect of the research and development in many industries. This paper covers two laser based techniques, Phase Doppler Particle Analyzer (PDPA) and Particle Image Velocimetry (PIV), for the design of fire suppression nozzles, paint nozzles, and N95 filter mask. The results of velocity profiles and droplet size distributions provided the critical information to evaluate the design and to allow corrections of deficiency in the process. Both the PDPA and PIV are non-invasive laser based techniques which introduce no disturbance to the flow and particle fields to be measured, giving the true representation of the measurement results.
Review of effects the rear spoiler aerodynamic analysis on ground vehicle performance
Authors: Deng Zhaowen , Yu Sijia , Gao Wei , Yi Qiang , Yu Wei
Published: August 2020

Recently reduce in fuel consumption and concern regarding the ground vehicle safety, automotive engineers are faced with the immediate task of introducing more efficient aerodynamic performance vehicles. Hence, the rear spoiler attached on the ground vehicle was presented. Rear spoiler is a device commonly found on road vehicle for improving their aerodynamic performance. Review on the research effects of the rear spoiler aerodynamic analysis on ground vehicle performance is reported in this paper. This review intends to enhance the stability and safety by attaching the rear spoiler on ground vehicle. The review mainly focus on aerodynamic analysis and control of the rear spoiler for different types ground vehicle in term of improving vehicle performance. Researches carried out by a number of researchers with regard to analyze and control the rear spoiler of ground vehicle and their effect on ground vehicle performance. Aerodynamic analysis i.e. computational fluid dynamics(CFD), design optimization, drag coefficient (Cd
) and lift coefficient (Cl
) and control methods i.e. passive control and active control had been reviewed. Meanwhile, progressive research on the rear spoiler aerodynamic analysis was observed due to its flexibility for wide range of application in the different type vehicles.
Feature Extraction from Turbulent Channel Flow of Moderate Reynolds Number via Composite DMD Analysis
Authors: Li Binghua , Mena Jesús Garicano , Zheng Yao , Valero Eusebio
Published: August 2020

In this contribution, we described a Dynamic Mode Decomposition (DMD) analysis of a turbulent channel flow database at a moderate friction Reynolds number Reτ
≈ 950. More specifically, a composite-based DMD analysis was conducted, employing hybrid snapshots assembled by skin friction Cf
(tk
) and either instantaneous Reynolds stress

(

u

′

v

′

(

x

→

;

t

k

)

)

or streamwise velocity fluctuation

(

u

′

(

x

→

;

t

k

)

)

fields. The DMD modes thus obtained were sorted according to its relevance to the Cf
: less than 2% of the modes suffice to reconstruct accurately either the streamwise velocity or the Reynolds stress profiles near the wall. Furthermore, we aim to extend our preliminary work on the analysis of the turbulent database, by considering snapshots encompassing a larger spatial subdomain and covering a longer temporal span. However, this study involved data matrices significantly larger than that one, which the memory footprint of this problem exceeds a typical workstation. Accordingly, we have resorted to the parallel, memory distributed DMD algorithm as a reinforcement. With this enhanced composite DMD algorithm, flow features of moderate and even large turbulent channel problems could be identified and characterized.
Research on Influence of Angle of Deflector on Air Flow in Spray Area Based on Numerical Simulation
Authors: Hao Guangfa , Zhang Chengliang , Sun Kang , Li Lei , Zhou Jun
Published: August 2020

The movement and distribution of the airflow field of the sprayer are very important for the distribution and penetration of the droplets. It is the focus and difficulty of the research to find the airflow field distribution of the fan outlet that matches the parameters of the canopy of the fruit tree. In order to study the influence of the angle change of the deflector of the orchard air-driven sprayer on the three-dimensional spatial distribution of the external air velocity field, this paper numerically simulated the external flow field based on computational fluid dynamics. The spray requirements of different fruit tree crown shapes were analyzed. The ICEM CFD software was used to model the external flow field. In order to improve the calculation efficiency, the model was divided into mixed grids. The k-ε turbulence model and Fluent solver are used for numerical solution. The flow fields of different deflectors are analyzed, and the influence of different positions and different sizes of deflector angles on the external flow field is determined.
Research on the Influence of the Deflector Angle on the Droplet Trajectory Based on the CFD Discrete Phase Model
Authors: Hao Guangfa , Zhang Chengliang , Sun Kang , Li Lei , Zhou Jun
Published: August 2020

In order to investigate the effect of the air deflector sprayer deflector angle on the droplet drift, this paper based on the particle tracking technology of the discrete phase model of CFD, studied the characteristics of droplets at different positions of the deflector angle. In this paper, six groups of nozzles are set at the air outlet in the cuboid calculation area with the conditions of 4000mm × 2000mm × 3300mm. Under the same wind conditions, the sprayer’s deflector changes and the droplet motion characteristics are analyzed. The results show that the droplets are accelerated by the high-speed airflow, and the velocity gradually becomes smaller as the distance increases. The speed is stable at a position close to the canopy of the fruit tree, and the speed is roughly between 8m / s-15m / s, which is almost the same as the wind speed delivered.
Numerical simulation of support interference characteristics on a low-aspect ratio flying-wing model
Authors: Zhang Yaobing , Li Bin , Cui Pengcheng , Zhou Naichun , Wu Xiaojun
Published: August 2020

The flying-wing aircraft is a promising concept for the mid or long-term commercial aviation due to its excellent performance in aerodynamic and structure, which has been studied by a number of investigators both experimentally and computationally. However, the conditions in wind-tunnel testing do not necessarily reflect those observed in free flight, the support structure interference is an important factor to affect experimental data collected from wind tunnels. Support interference characteristics of a flying-wing model from subsonic to supersonic speed is investigated by numerical simulation methods. Results show that grid convergence is obtained with the series of grids, which implies that the solutions are in the asymptotic range. The support has a relatively small effect on aerodynamic characteristics of flying-wing aircraft at low speed while has a relatively large effect on drag at transonic speed and supersonic speed.
Stochastic Characteristic Analysis of Lid-Driven Cavity Flow
Authors: Zhang Chao , Zhao Hui , Hu Xingzhi , Chen Jiangtao
Published: August 2020

The stochastic characteristic of lid-driven cavity flow under the condition of Re=100 is investigated in this paper by a non-intrusive polynomial chaos method. The lid-driven velocity and viscosity coefficient are assumed to be two independent stochastic input variables with Gaussian distributions. The velocities at every grid points are the response of interest and no longer deterministic but stochastic. Their stochastic characteristics are represented by Hermite polynomials with interaction effects between two input variables considered. The statistical results, including mean value, variance and the relative contribution of each input variable to the variance of outputs are analysed. It is found that the variance of velocity shows similar structures with its magnitude of mean value and the correlation coefficient is larger than 0.96. The nearly linear correlation coefficient shows that the lid-driven velocity is the main factor affecting the velocity distribution and the influence of viscosity coefficient on most regions is unimportant. The analysis of stochastic flow field helps understand the inherent mechanism in the lid-driven cavity flow.
Study of underwater vehicle’s bubbly wake caused by side exhausting
Authors: Wang Yun , Xu Jun , Dong Liang , Gu Wei
Published: August 2020

The bubbly wake characteristics of the underwater vehicle are the basic of wake homing techniques. The bubbly wake of the underwater vehicle caused by the side exhausting is simulated based on the Mixture model and the Multiple Reference Frames technology. The results show that due to the side exhausting of the underwater vehicle, a wake with lots of bubbles appears in the sailing through area. The bubbly wake of the underwater vehicle lasts for a long time. As a result, the bubbly wake can be observed in the area far away from the underwater vehicle, which is signification enough to be detected by the bubbly wake detector. Besides, the bubbly wake characteristics for the cases of the underwater vehicle with/without the propeller are much different.
Numerical Simulation of Internal Flow Field and Structural Optimum Design for the diesel engine SCR Catalytic Converter
Authors: Gao Wei , Wang Shaofei
Published: August 2020

A three-dimensional model and finite element model of the diesel engine SCR catalytic converter were established by using ANSYS software. The numerical simulation of the internal flow field for the diesel engine SCR catalytic converter was performed. The results show that the pressure loss of the catalytic converter is larger and the velocity distribution in the front of substrate is nonuniform. On this base, the effects of the diameters and lengths of the substrate on the catalytic converter’s internal flow field characteristic were studied. The results show that when the substrate’s length increases, the pressure loss increases and the velocity distribution uniformity in the front of substrate becomes worse. When the diameter of substrate increases, the pressure loss decreases and the velocity distribution uniformity in the front of substrate becomes better. Therefore, the structure of catalytic converter was optimized. Through the optimization of the structure, the velocity distribution in the front of substrate is more uniform. The passing capacity of substrate is increased. The conversion efficiency of catalytic converter is improved. The back pressure is reduced.
A numerical study of the anti-icing heat load for a three-dimensional aircraft wing
Authors: Ni Zhangsong , Liu Senyun , Zhang Jun , Wang Mao , Wang Zixu
Published: August 2020

In the design stage of an anti-icing system for an aircraft, the heat load on a protection surface must be correctly calculated. In this study, the heat load calculation method for an aircraft wing model was analyzed. The calculation process was presented and the correctness of the method was validated using existing published experimental data. And the effect of variation of incoming flow speeds, flight altitudes, and temperatures on the surface heat-load distribution was given. The results show that the heat load is mainly located at the leading edge of the wing. The maximum value of the heat load can reach 3500w/m2 and the closer to the tip of the wing, the larger the heat load value will be. The heat load curve has a trough in the middle and two shoulders at each side. The range of the non-zero region and the amplitude of the heat load is in proportion to the flow speed. However, the variation of altitude has a non-obvious effect on the heat load results. As the temperature rises, the amplitude of the heat load increases, but the distribution characteristic of the curve remains the same.
Comparative Study on the Aerodynamic Characteristics of Flame Stabilizer Employing Supersonic Jet and Subsonic Jet Based on Numerical Method
Authors: Li Ziwan , Varsegov V. , Yuan Yixiang
Published: August 2020

To compare the aerodynamic characteristics of flame stabilizer by supersonic jet and flame stabilizer by subsonic jet, this article studies the size and length/width ratio of recirculation zone, size of jet trajectory at both supersonic and subsonic jet under the same geometry and boundary conditions in the ANSYS Fluent software program. The result shows that under supersonic jet the size, length/width ratio of recirculation zone and size of jet trajectory are bigger than under subsonic jet. Due to the size of recirculation zone is related to the burning range, that means using supersonic jet as a flame stabilizer can enlarge the stable burning range of a combustion chamber. It would make a big difference when the jet flame stabilizer apply to the gas turbine aircraft engine.