Experimental investigation of the spatial displacements of an arc-heated plasma

Oscillations of an electric arc in a plasmatron with the fixed arc in wide ranges of currents and air flow rates have been investigated. The distribution functions of arc oscillations have been obtained for various currents, gas flow rates, and distances from a cathode.     

迷宫密封气流激振及其动力系数的研究

本文从流体力学基本方程出发,建立起一组描述在迷宫密封腔中气流流动情况的偏微分方程组,并应用特征线方法求得了其解.同时还按不同工作条件下密封腔内的压力分布,进行了迷宫装置刚度的计算.为了从实验方面也能对迷宫气流激振形成的迷宫装置的动力特性进行研究,设计并制造了一台可以在多种条件下进行试验的试验台.通过试验,测得了在不同工作条件下各密封腔内的压力分布,从而得到了以实测为基础的迷宫装置的刚度系数.实验还结合振动频谱分析,研究了各种参数对转子系统稳定性的影响.文中将实验结果与理论分析进行了比较,两者间的相符情况是令人满意的.     

Supersonic flow over cylindrical afterbodies with base bleed

Computations of supersonic flow over two cylindrical afterbodies have been made using a thin-layer Navier-Stokes base flow code. The capability to compute the base flow with base bleed at supersonic speeds has been developed and used to show the effect of mass injection on the base pressure or base drag. Solutions have been obtained for a projectile and a missile configuration having cylindrical afterbodies. Numerical results show the effect of base bleed on the near wake flow field. The rise in base pressure or reduction in base drag has been clearly predicted for various mass injection rates and comparison with experimental data shows generally good agreement.     

Uniform pulsatile flow of an incompressible liquid in a tube of parallelogram cross-section

Laminar steady and pulsatile flow in a tube of parallogram cross-section has been derived analytically for incompressible viscous liquid. Velocity profiles have been determined and the influence of various parameters, such as skew angle, side ratio and forced frequency parameter Ωa²/v have been determined. In addition the flow resistance is presented for various side ratios as a function of the skew angle.     

Stability of two-layered fluid flows in an inclined channel

A linear stability analysis of two-layer fluid flows in an inclined channel geometry has been carried out. The onset of flow transitions and the spatio-temporal characteristics of secondary flows produced by the flow instabilities have been examined. The effects of density and viscosity stratifications and surface tension on flow structures also have been investigated at various values of Froude numbers (channel inclinations). Multi-domain Chebyshev–Tau spectral methods along with MATLAB QZ eigenvalue solver are used to determine the whole spectrum of the eigenvalues and associated eigenfunctions. The neutral stability diagrams and stability boundaries are constructed for various values of flow parameters. The onset of flow transitions and flow structures predicted by linear stability analysis are compared against experimental results and they agree reasonably well. The results presented in the present paper imply that the shear mode of flow transitions is the one likely to be identified in experiments.     

流量测量中超声多普勒信号的频谱特点及其与管道中流速的关系

研究了工业测流的超声多普勒信号的频谱特点，并以此为依据分析了不同安装方式对多普勒频谱的影响，提出了不同测量环境下，应用多普勒频谱计算流速的公式及必要的修正，为提高检测准确度提供了理论依据。     

Flow diagnostics in a vortex furnace by particle image velocimetry

The internal aerodynamics of a model vortex furnace for a steam generator with a horizontal axis of flow rotation and distributed input of fuel-air mixture jets has been studied. Average characteristics of the flow velocity field in various cross sections have been determined using a digital tracer imaging (particle image velocimetry) technique. Results are compared to data obtained by the method of laser Doppler anemometry.     

Direct Blood Cell Flow Imaging in Microvascular Networks

Blood flow dynamics in microvascular networks are intimately related to the health of tissues and organs. While numerous imaging modalities and techniques have been developed to assess blood flow dynamics for various applications, their utilization has been hampered by limited imaging speed and indirect quantification of blood flow dynamics. Here, direct blood cell flow imaging (DBFI) is demonstrated that provides visualization of individual motions of blood cells over a field of 0.71 mm × 1.42 mm with a time resolution of 0.69 ms (1450 frames s⁻¹) without using any exogenous agents. DBFI enables precise dynamic analysis of blood cell flow velocities and fluxes in various vessels over a large field, from capillaries to arteries and veins, with unprecedented time resolution. Three exemplary applications of DBFI, quantification of blood flow dynamics of 3D vascular networks, analysis of heartbeat induced blood flow dynamics, and analysis of blood flow dynamics of neurovascular coupling, illustrate the potential of this new imaging technology.     

Numerical investigation of the character of the lift on a cylindrical particle in Poiseuille flow of a plane channel

The character of the lift on a cylindrical (porous and solid) particle in Poiseuille flow of a plane channel has been investigated. The lift at various values of the Reynolds number, the particle size, and its position in the flow have been calculated.     

Effect of a magnetic field on the hysteresis transitions during floating-zone crystal growth

The effect of a constant axial magnetic field on the thermosolutocapillary (TSC) convection in the floating liquid zone with an undeformed free surface under microgravity (MG) conditions has been studied. It is established that several stable flow regimes may coexist under such conditions in a certain range of parameters. The boundaries of transitions between various convection regimes under MG conditions with various Hartmann numbers have been determined. It is shown that the constant axial magnetic field suppresses TSC convection, so that the region of uncertainty decreases and shifts toward higher Marangoni numbers. The dependence of the structure and intensity of flow on the floating-zone length to radius ratio has been analyzed.     

An heuristic for configuring a mixed uni/bidirectional flow path for an AGV system

An heuristic methodology has been developed in the present work for configuring a mixed (hybrid) uni/bidirectional flow path for an AGV material handling system. The given unidirectional flow path layout, material flow intensities and vehicle travelling time matrix among various processing centres are taken as input information to this technique. A multiplicative function of material flow intensities between any two centres is used as a criterion for selectively configuring a path as a bidirectional one. The highest such product indicates that the shorter path between that pair of centres is a strong candidate for being configured as bidirectional. The heuristic has been applied to an illustrative FMS and various alternate flow path designs have been obtained. Simulation is then performed with the aim of comparing the productive potentials of the facility when it is operated on either unidirectional, or mixed uni/bidirectional, or allbidirectional flow path design alternatives. The benefits of bidirectional flows over unidirectional counterpart are significant in terms of system throughput rates and optimal AGV fleet sizes. However, traffic control becomes an important issue as vehicle interference and blocking increases with increase in bidirectionality in the network. The decision related to location and capacity planning of vehicle buffering zones is also addressed.     

A Fractal-Fractional Model for the MHD Flow of Casson Fluid in a Channel

An emerging definition of the fractal-fractional operator has been used in this study for the modeling of Casson fluid flow. The magnetohydrodynamics flow of Casson fluid has cogent in a channel where the motion of the upper plate generates the flow while the lower plate is at a static position. The proposed model is non-dimensionalized using the Pi-Buckingham theorem to reduce the complexity in solving the model and computation time. The non-dimensional fractal-fractional model with the power-law kernel has been solved through the Laplace transform technique. The Mathcad software has been used for illustration of the influence of various parameters, i.e., Hartman number, fractal, fractional, and Casson fluid parameters on the velocity of fluid flow. Through graphs and tables, the results have been implemented and it is shown that the boundary conditions are fully satisfied. The results reveal that the flow velocity is decreasing with the increasing values of the Hartman number and is increasing with the increasing values of the Casson fluid parameter. The findings of the fractal-fractional model have elucidated that the memory effect of the flow model has higher quality than the simple fractional and classical models. Furthermore, to show the validity of the obtained closed-form solutions, special cases have been obtained which are in agreement with the already published solutions.     

Heat transfer and hydraulic resistance in channels with spherical protrusions

This article presents an analytical overview of experimental studies of hydraulic resistance and heat transfer in channels with disturbed flow surfaces in the form of systems of spherical protrusions in a wide range of flow and design parameters. A uniform approach to generalization of experimental data by various authors has been developed considering differences in the geometry of heat-transfer surfaces. Uniform universal generalizing dependences have been obtained for the hydraulic resistance and heat transfer coefficients in channels with spherical protrusions.     

Identification of rheological parameters on the basis of plane strain compression tests on specimens of various initial dimensions

The work is based on the assumption that the flow stress of a material should be insensitive to the method of plastometric testing or to the size of the samples. It is generally observed, however, that various methods of testing yield different values of the flow stress. Endeavours are made to eliminate these differences and various methods of correction of the results of the tests have been developed. The particular objective of the present work is to check the capabilities of the inverse technique to obtain consistent flow stress data when this technique is applied to plane strain compression tests performed on one material with various dimensions of the specimens. The experiments included plane strain compression for specimens measuring 2.5, 5 and 10 mm initial thickness. The inverse algorithm developed by the authors was used in the investigation. Application of the inverse analysis to the interpretation of the results of these tests allowed the conclusion that the results obtained for various specimen geometries coincide very closely.This analysis has been further used for evaluation of various conventional methods for correction to account for the influence of inhomogeneity of strain and temperature.     

Charge separation of plasma flow in curvilinear magnetic field

The energy spectra of ions occurring in various charged states in a flow of titanium plasma in a steady-state vacuum arc discharge have been studied. It is established that, during the motion of this flow through a plasma transport system based on a curvilinear magnetic field, ions with different charges are spatially separated. As a result, at the system output, ions with greater charges are concentrated in the inner part of the plasma flow, so that the average charge of ions in this region is higher than that in the outer part of the flow.     

Lubrication oil pumping by utilizing vane motion in a horizontal rotary compressor

For a horizontal rotary compressor which utilizes reciprocating motion of the vane for oil supply into lubrication elements, an analytical study has been carried out on the oil pumping mechanism. Energy equation has been applied to the oil flow inside the oil-conveying pipe with oil feeding hole in the middle. Oil distributions into individual lubrication elements such as various bearing elements have also been analyzed by applying electric circuit network theory to the oil flow network. Fairly good agreement between calculations and experiments for the oil pumping rate has been obtained in a wide range of compressor speed.     

Viscous potential flow analysis of electrohydrodynamic Kelvin–Helmholtz instability with heat and mass transfer

Viscous potential flow analysis of Kelvin–Helmholtz instability with heat and mass transfer in presence of a horizontal electric field has been carried out. Stability criterion is given by a critical value of relative velocity of two fluids as well as critical value of the applied electric field. Various graphs with respect to physical parameters, such as wave-number, viscosity ratio, ratio of dielectric constants of two fluids, heat transfer coefficients have been drawn and effect of various parameters have been described.     

A novel model for vibrations of nanotubes conveying nanoflow

In this paper, we have presented an innovative model for coupled vibrations of nanotubes conveying fluid by considering the small-size effects on the flow field. By this model, we have demonstrated that ignoring the small-size effects on flow field in a nano-scale fluid-structure interaction (FSI) problem may generate erroneous results. The nanotube has been modeled by Euler-Bernoulli plug-flow beam kinematic theory, and we have formulated the small-size effects on bulk viscosity and slip boundary conditions of nanoflow through Knudsen number (Kn), as a discriminant parameter. The divergence instability phenomenon has been observed, incorporating various flow regimes for liquids and gases. We have observed that including the effect of nanoflow viscosity, is not so influential on vibration of nanotubes conveying fluid, as compared with the results of vibration of nanotubes conveying an inviscid fluid; however, incorporating the nanoflow slip-boundary conditions hypothesis changes the results drastically, as compared to continuum flow models.     

Multicomponent affinity radial flow chromatography

Radial flow chromatography can provide high volumetric flow rates with small bed pressures. It is advantageous for use in affinity chromatography in which resolution requirements can be easily achieved because of highly selective biospecific binding. In this work a general multicomponent kinetic rate model has been formulated for the simulation of various aspects of radial flow affinity chromatography. The model accounts for radial dispersion, external mass transfer, intraparticle diffusion, second-order kinetics, and reactions between soluble ligands and the macromolecules in the elution stage of affinity chromatography. The model is solved with an efficient and robust numeric procedure that uses the finite element, the orthogonal collocation, and the Gear's stiff methods. Kinetic effects have been studied and compared with mass transfer effects. The three stages of affinity chromatography—frontal adsorption, wash, and elution—have been simulated. The effects of the concentration and the affinity of the soluble ligands used in the elution stage have been discussed.     

Numerical study on the lubrication oil distribution in a refrigeration rotary compressor

For a rolling piston rotary compressor, oil supply into various lubrication elements has been analytically studied. The lubrication system, consisting of centrifugal shaft pump, radial oil feeding holes, bearings with grooves and some other sliding surfaces has been modeled by employing equivalent electric circuit network. A computer simulation program has been developed to solve the network model of the lubrication system. Its numerical solutions include total oil flow rate into the shaft inlet, oil flow rates in the main and sub journal bearings and in the eccentric bearing, and oil leakages through roller end clearances into suction and compression chambers. Validation of the numerical simulation has been made by the measurement of the total oil flow rate into the shaft. With the aid of computer simulation, parametric studies have also been carried to investigate the effects of the bearing groove shape and groove inclination angle on the bearing oil flow rates.