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1.
F. A. Bykovskii E. F. Vedernikov 《Journal of Applied Mechanics and Technical Physics》2000,41(1):35-43
A vortex structure of an air flow with a characteristic size of vortices comparable with the primary vortex size was observed
in a vortex chamber of planar-radial geometry for the first time. The vortex component of the flow velocity along the chamber
radius and its axis was calculated.
Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1, pp. 41–49, January–February, 2000. 相似文献
2.
M. Boileau S. Pascaud E. Riber B. Cuenot L. Y. M. Gicquel T. J. Poinsot M. Cazalens 《Flow, Turbulence and Combustion》2008,80(3):291-321
An extension of the large eddy simulation (LES) technique to two-phase reacting flows, required to capture and predict the
behavior of industrial burners, is presented. While most efforts reported in the literature to construct LES solvers for two-phase
flow focus on Euler–Lagrange formulation, the present work explores a different solution (‘two-fluid’ approach) where an Eulerian
formulation is used for the liquid phase and coupled with the LES solver of the gas phase. The equations used for each phase
and the coupling terms are presented before describing validation in two simple cases which gather some of the specificities
of real combustion chamber: (1) a one-dimensional laminar JP10/air flame and (2) a non-reacting swirled flow where solid particles
disperse (Sommerfeld and Qiu, Int. J. Multiphase Flow 19(6):1093–1127, 1993). After these validations, the LES tool is applied to a realistic aircraft combustion chamber to study both a steady flame
regime and an ignition sequence by a spark. Results bring new insights into the physics of these complex flames and demonstrate
the capabilities of two-fluid LES. 相似文献
3.
A mathematical model of the supersonic combustion chamber of a hydrogen/air hypersonic ramjet is proposed. The model is developed
on the basis of a “burn-out curve”, that is, the dependence of the combustion efficiency on the longitudinal coordinate and
the design features of the chamber. The burn-out curve, which describes the mixing and burning of hydrogen and air, is assumed
to be known from previous numerical and experimental studies of these processes under supersonic flow conditions. Other physical
and chemical processes which take place in the combustion chamber, such as excitation of internal molecular degrees of freedom,
hydrogen and oxygen dissociation, OH and NO formation, etc., are assumed to be equilibrium.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 146–154, January–February,
1997.
The work was carried out with the support of the Russian Foundation for Fundamental Research (project No. 93-013-17514). 相似文献
4.
A. Eidelman T. Elperin N. Kleeorin A. Markovich I. Rogachevskii 《Experiments in fluids》2006,40(5):723-732
Coherent large-scale circulations of turbulent thermal convection in air have been studied experimentally in a rectangular box heated from below and cooled from above using Particle Image Velocimetry. The hysteresis phenomenon in turbulent convection was found by varying the temperature difference between the bottom and the top walls of the chamber (the Rayleigh number was changed within the range of 107–108). The hysteresis loop comprises the one-cell and two-cells flow patterns while the aspect ratio is kept constant (A=2–2.23). We found that the change of the sign of the degree of the anisotropy of turbulence was accompanied by the change of the flow pattern. The developed theory of coherent structures in turbulent convection (Phys Rev E 66:1–15, 2002, Boundary-Layer Meteorol, 2005) is in agreement with the experimental observations. The observed coherent structures are superimposed on a small-scale turbulent convection. The redistribution of the turbulent heat flux plays a crucial role in the formation of coherent large-scale circulations in turbulent convection. 相似文献
5.
Ultrasound thermometry in transparent and opaque fluids 总被引:1,自引:0,他引:1
We have exploited the temperature dependence of sound velocity to measure the thermal fields in transparent and opaque fluids. A chamber containing glycerol undergoing Rayleigh–Bénard convection was probed with an ultrasound transducer operating in the pulse-echo mode. The times-of-flight for the ultrasound pulse to traverse the fluid at several transducer locations were converted into a temperature profile that is in qualitative agreement with simultaneous thermochromic liquid crystal visualization of the flow pattern. Temperature profiles in a mercury-filled stainless steel chamber have also been obtained, both for quiescent and turbulent flows, thereby validating the ultrasound thermometry concept for opaque fluids as well. 相似文献
6.
A numerical study of mixed convection in a vertical channel filled with a porous medium including the effect of inertial forces
is studied by taking into account the effect of viscous and Darcy dissipations. The flow is modeled using the Brinkman–Forchheimer-extended
Darcy equations. The two boundaries are considered as isothermal–isothermal, isoflux–isothermal and isothermal–isoflux for
the left and right walls of the channel and kept either at equal or at different temperatures. The governing equations are
solved numerically by finite difference method with Southwell–Over–Relaxation technique for extended Darcy model and analytically
using perturbation series method for Darcian model. The velocity and temperature fields are obtained for various porous parameter,
inertia effect, product of Brinkman number and Grashof number and the ratio of Grashof number and Reynolds number for equal
and different wall temperatures. Nusselt number at the walls is also determined for three types of thermal boundary conditions.
The viscous dissipation enhances the flow reversal in the case of downward flow while it counters the flow in the case of
upward flow. The Darcy and inertial drag terms suppress the flow. It is found that analytical and numerical solutions agree
very well for the Darcian model.
An erratum to this article is available at . 相似文献
7.
V. K. Kedrinskii 《Journal of Applied Mechanics and Technical Physics》2009,50(2):309-317
The dynamics of state of the crystallite-containing magma is studied within the framework of the gas-dynamic model of bubble
cavitation. The effect of crystallites on flow evolution is considered for two cases: where the crystallites are cavitation
nuclei (homogeneous-heterogeneous nucleation model) and where large clusters of crystallites are formed in the magma in the
period between eruptions. In the first case, decompression jumps are demonstrated to arise as early as in the wave precursor;
the intensity of these jumps turns out to be sufficient to form a series of discrete zones of nucleation ahead of the front
of the main decompression wave. Results of experimental modeling of an explosive eruption with ejection of crystallite clusters
(magmatic “bombs”) suggest that a cocurrent flow of the cavitating magma with dynamically varying properties (mean density
and viscosity) transforms to an independent unsteady flow whose velocity is greater than the magma flow velocity. Experimental
results on modeling the flow structure during the eruption show that coalescence of bubbles in the flow leads to the formation
of spatial “slugs” consisting of the gas and particles. This process is analyzed within a combined nucleation model including
the two-phase Iordansky-Kogarko-van Wijngaarden model and the model of the “frozen” field of mass velocities in the cavitation
zone.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 2, pp. 167–177, March–April, 2009. 相似文献
8.
V. A. Mal'tsev S. A. Novopashin A. L. Perepelkin 《Journal of Applied Mechanics and Technical Physics》1999,40(6):1057-1060
The effect of the flow character in the plenum chamber of a nozzle on the high-frequency boundary of the spectrum of fluctuations
at the boundary of a supersonic, strongly underexpanded jet of nitrogen exhausted from a circular sonic nozzle into the ambient
space was experimentally studied. The Reynolds number in the plenum chamber of the nozzle with a given throat area was varied
by changing the diameter of the subsonic region. The high-frequency boundary of the spectrum of turbulent fluctuations was
evaluated on the basis of two-point correlation functions of time. The technique for measurement of these functions was based
on molecular scattering of light. Radiation of two pulse lasers with a controlled delay between the pulses was used as a source
of light. It follows from experimental results that the high-frequency boundary of the spectrum of turbulent fluctuations
and the spectrum itself vary significantly depending on the Reynolds number of the flow in the plenum chamber.
Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 69–72, November–December, 1999. 相似文献
9.
At liquid–gas or liquid–liquid interfaces thermocapillary or Marangoni convection develops in the presence of a temperature
or concentration gradient along the interface. This convection was not paid much attention up to now, because under terrestrial
conditions it is superimposed by the strong buoyancy convection. In a microgravity environment, however, it is the remaining
mode of natural convection. During boiling in microgravity it was observed at subcooled conditions. Therefore the question
arises about its contribution to the heat transfer. Thus the thermocapillary convection was intensively studied at single
gas bubbles in various liquids both experimentally and numerically. Inside a temperature gradient chamber, the overall heat
transfer around single bubbles of different volume was measured with calorimetry and the liquid flow with PIV and LDV. In
parallel to the experiment, a 2-dimensional mathematical model was worked out and the coupled heat transfer and fluid flow
was simulated with a CV-FEM method both under earth gravity level and under microgravity. The results are described in terms
of the dimensionless Nusselt-, Peclet-, Marangoni-, Bond- and Prandtl-number.
Received on 23 August 1999 相似文献
10.
S. B. Dorofeev A. V. Bezmelnitsin V. P. Sidorov J. G. Yankin I. D. Matsukov 《Shock Waves》1996,6(2):73-78
Large scale experiments (50 m3) have been carried out on the initiation of detonation by means of a jet of hot combustion products. The effects of hydrogen
concentration (18–30% vol.), jet orifice diameter (100–400 mm), and the mixture composition in constant volume explosion chamber
(25–50%) were investigated. Both high enough hydrogen concentration and large enough jet size are necessary for detonation
initiation. The minimum values are within the ranges of 20 to 25% vol. H2, and of 100 to 200 mm correspondingly. A minimum ratio of jet size and mixture cell width 12–13 is required for detonation
initiation. 相似文献
11.
A. N. Shiplyuk V. M. Aniskin V. A. Seleznev V. Ya. Prinz A. A. Maslov R. S. Matvienko 《Journal of Applied Mechanics and Technical Physics》2009,50(3):454-458
Aerodynamic experiments with arrays of conducting microtubes are performed, and their electric properties are determined.
Sensitivity of microtubes located on the model surface to disturbances of the gas flow is revealed. It is demonstrated that
such microtubes can be used both for registration of disturbances being introduced and as disturbance generators.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 112–117, May–June, 2009. 相似文献
12.
A single piston capillary rheometer was modified by the addition of a second chamber with a restricting valve (developed at
the Polymer Centre, Zlín, Czech Republic), which provides backpressure and increasing the pressure in the melted material
during the flow through the die. The Carreau–Yasuda model was employed to fit the measured viscosity data and determine the
temperature and pressure coefficients for polyolefin based binder and its compounds with carbide powder. Both temperature
and pressure sensitivity coefficients are largely dependent on the structure of a polymer, which should be taken into account
for binder-formation’s development. Increasing the loading level of the powder in the compound diminishes the pressure sensitivity
of their flow properties. 相似文献
13.
14.
H.G. Hornung 《Shock Waves》1998,8(1):11-21
The inviscid equations of motion for the flow at the downstream side of a curved shock are solved for the shock–normal derivatives.
Combining them with the shock–parallel derivatives yields gradients and substantial derivatives. In general these consist
of two terms, one proportional to the rate of removal of specific enthalpy by the reaction, and one proportional to the shock
curvature. Results about the streamline curvature show that, for sufficiently fast exothermic reaction, no Crocco point exists.
This leads to a stability argument for sinusoidally perturbed normal shocks that relates to the formation of the structure
of a detonation wave. Application to the deflection–pressure map of a streamline emerging from a triple shock point leads
to the conclusion that, for non–reacting flow, the curvature of the Mach stem and reflected shock must be zero at the triple
point, if the incident shock is straight. The direction and magnitude of the gradient at the shock of any flow quantity may
be written down using the results. The sonic line slope in reacting flow serves as an example. Extension of the results –
derived in the first place for plane flow – to three dimensions is straightforward.
Received 12 February 1997 / Accepted 10 June 1997 相似文献
15.
The objective of this study relates to the numerical simulation of the free surface during the two-dimensional flow and solidification
of aluminum in the horizontal cylinder and mold cavity of the high pressure die casting HPDC machine with cold chamber. The
flow is governed by the Navier–Stokes equations (the mass and the momentum conservations) and solved in the two phase’s liquid
aluminum and air. The tracking of the free surface is ensured by the VOF method. The equivalent specific heat method is used
to solve the phase change heat transfer problem in the solidification process. Considering the displacement of the plunger,
the geometry of the problem is variable and the numerical resolution uses a dynamic grid. The study examines the influence
of the plunger speed on the evolution of the interface aluminum liquid–air profile, the mass of air imprisoned and the stream
function contours versus time. Filling of a mold is an essential part of HPDC process and affects significantly the heat transfer
and solidification of the melt. For this reason, accurate prediction of the temperature field in the system can be achieved
only by including simulation of filling in the analysis. 相似文献
16.
A. P. Makasheva A. Zh. Naimanova 《Journal of Applied Mechanics and Technical Physics》2008,49(3):391-399
Results of a numerical study of three-dimensional supersonic jets propagating in a cocurrent flow are described. Averaged
parabolized Navier-Stokes equations are solved numerically on the basis of a developed scheme, which allows calculations in
supersonic and subsonic flow regions to be performed in a single manner. A jet flow with a cocurrent flow Mach number 0.05
⩽ M∞ ⩽ 7.00 is studied, and its effect on the structure of the mixing layer is demonstrated. The calculated results are compared
with available experimental and numerical data.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 54–63, May–June, 2008. 相似文献
17.
The hydrodynamics of processes occurring in explosion of condensed explosives in air is considered. The physical model, computation
technique, and results of simulation of a two-dimensional hydrodynamic flow arising in explosion of cylindrical charges are
discussed. In this case, the explosions are considered at some distance above the ground. To close the gas-dynamics equations,
the Jones–Wilkins–Lee equation of state is used. The results of calculation allow one to obtain a detailed space–time pattern
of the arising flow and to study the origination, propagation, and subsequent attenuation of shock waves. Cylindrical charges
of the same mass but with different diameter-to-length ratios are considered. It is shown that the charge shape can render
essential influence on dynamics of flow and the parameters of shock waves (in the near and medium fields of explosion). 相似文献
18.
This paper reports the first large eddy simulation (LES) of a self-excited oscillating triangular jet (OTJ) issuing from a
fluidic nozzle that consists of a small triangular orifice inlet followed by a large circular chamber and an orifice outlet.
The case simulated is identical to that measured experimentally by England et al. (Exp Fluids 48(1):69–80, 2010). The present prediction agrees well with the previous measurement. The simulation reveals that the central oscillating jet
exhibits axis-switching in the cross-section and rotates by 60° approximately over a downstream distance of x = 0.5D (chamber diameter). Three strong longitudinal vortices occur associated with the three vertices of the inlet triangle. These
vortices strongly interact with the central jet and also the surroundings, in the region at x/D ≤ 1, and appear to merge finally with the outer secondary swirling flow. These observations are consistent with the deduction
from previous experiments. 相似文献
19.
Numerical simulation of blood flow and interstitial fluid pressure in solid tumor microcirculation based on tumor-induced angiogenesis 总被引:1,自引:0,他引:1
Gaiping Zhao Jie Wu Shixiong Xu M. W. Collins Quan Long Carola S. König Yuping Jiang Jian Wang A. R. Padhani 《Acta Mechanica Sinica》2007,23(5):477-483
A coupled intravascular–transvascular–interstitial fluid flow model is developed to study the distributions of blood flow
and interstitial fluid pressure in solid tumor microcirculation based on a tumor-induced microvascular network. This is generated
from a 2D nine-point discrete mathematical model of tumor angiogenesis and contains two parent vessels. Blood flow through
the microvascular network and interstitial fluid flow in tumor tissues are performed by the extended Poiseuille’s law and
Darcy’s law, respectively, transvascular flow is described by Starling’s law; effects of the vascular permeability and the
interstitial hydraulic conductivity are also considered. The simulation results predict the heterogeneous blood supply, interstitial
hypertension and low convection on the inside of the tumor, which are consistent with physiological observed facts. These
results may provide beneficial information for anti-angiogenesis treatment of tumor and further clinical research.
The project supported by the National Natural Science Foundation of China (10372026). 相似文献
20.
A. Yu. D’yachenko V. I. Terekhov N. I. Yarygina 《Journal of Applied Mechanics and Technical Physics》2006,47(5):671-678
The process of vortex formation in a cavity with inclined walls, which has a moderate aspect ratio, is experimentally studied,
and the distribution of pressure coefficients is measured. The angle of inclination of the side walls ϕ is varied from 30
to 90°. It is found that the flow in the cavity becomes unstable in the range of inclination angles ϕ = 60–70°. Flow reconstruction
occurs, which substantially alters the surface-temperature and static-pressure distributions. Large changes in these characteristics
and their nonuniform distributions for these angles are observed across the cavity on its frontal wall and on the bottom.
For small angles (ϕ = 30 and 45°), the pressure on the rear wall drastically increases, which leads to a small increase in
pressure averaged over the entire cavity surface.
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Translated from PrikladnayaMekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 68–76, September–October, 2006. 相似文献