Acoustic-velocity measurement across the diameter of a liquid-metal column

Present techniques for measuring sound velocity in liquid metals have been limited by the use of transducers which cannot survive in extreme-temperature conditions. These methods also require relatively long measurement times. An optical noncontacting method has been developed which may be used for extremely short experimental times and very high temperatures and pressures. This technique is being incorporated into an isobaric-expansion apparatus in which a 1-mm-diam wire sample in a high-pressure argon-gas environment is resistively heated to melt within a time period of only a few microseconds. Before instability of the liquid column occurs, thermal expansion, enthalpy and temperature are measured. The addition of the sound-velocity measurement permits a more complete determination of the thermophysical properties of the liquid metal.     

Effect of the plenum-chamber diameter on the turbulent characteristics of a supersonic jet

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.     

Affecting the phase split at a large diameter T-junction by using baffles

Current research has expanded on the existing database by conducting air–water experiments in a 0.125 m regular T-junction and a 0.125/0.076 m reduced T-junction. Inserts, cut to 30° and 45°, protruded from the side arm into the main pipe of the junction at different protrusion depths and their effect on the two-phase flow phase split at the junction measured. Depending on the approaching flow regime, inserts placed at the junction were seen to either enhance the partial phase separation occurring at the T-junction or promote a more equal flow split between the two downstream arms.     

Eigenoscillations near a plate in a channel

Acoustic eigenoscillations of a gas near a plate in a rectangular channel, i.e., the eigenfrequency of oscillations as a function of the chord length and the position of the plate in the channel, and the form of the eigenfunctions are studied in a two-dimensional formulation. A mathematical model of eigenoscillations near a plate in a channel has been proposed and substantiated, and the dependence of the eigenfrequency of oscillations on the geometric parameters is studied numerically with the use of this model. Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 2, pp. 78–90, March–April, 1998.     

Hydromagnetic flow in a rotating channel

The steady flow in a parallel plate channel rotating with an angular velocity Ω and subjected to a constant transverse magnetic field is analysed. An exact solution of the governing equations is obtained. The solution in the dimensionless form contains two parameters: the Hartmann number, M ², and K ² which is the reciprocal of the Ekman number. The effects of these parameters on the velocity and magnetic field distributions are studied. For large values of the parameters, there arise thin boundary layers on the walls of the channel.     

Magnetohydrodynamic entrance flow in a channel

A MHD entrance flow in a channel is studied in the Prandtl approximation. It is shown that consistency with the approximation requires an appropriate change in the boundary conditions which hold for the original, unsimplified equations. The correct boundary conditions are established and used to repete the numerical calculations in a few cases studied by other authors with the unmodified boundary conditions. In the cases here considered the numerical differences do not amount in practice to more than 10%, though they grow with increasing Hartmann number. Gabinete de Aplicaciones Nucleares de O.P. and Centro Coordinado de Fisica (C.S.I.C.-U.A.M.). Present address: Departamento de Física, Facultad de Ciencias, Universidad Autónoma de Madrid.     

Numerical simulation of the nanoparticle diameter effect on the thermal performance of a nanofluid in a cooling chamber

The thermal performance of a nanofluid in a cooling chamber with variations of the nanoparticle diameter is numerically investigated. The chamber is filled with water and nanoparticles of alumina (Al₂O₃). Appropriate nanofluid models are used to approximate the nanofluid thermal conductivity and dynamic viscosity by incorporating the effects of the nanoparticle concentration, Brownian motion, temperature, nanoparticles diameter, and interfacial layer thickness. The horizontal boundaries of the square domain are assumed to be insulated, and the vertical boundaries are considered to be isothermal. The governing stream-vorticity equations are solved by using a secondorder central finite difference scheme coupled with the mass and energy conservation equations. The results of the present work are found to be in good agreement with the previously published data for special cases. This study is conducted for the Reynolds number being fixed at Re = 100 and different values of the nanoparticle volume fraction, Richardson number, nanofluid temperature, and nanoparticle diameter. The results show that the heat transfer rate and the Nusselt number are enhanced by increasing the nanoparticle volume fraction and decreasing the Richardson number. The Nusselt number also increases as the nanoparticle diameter decreases.     

Gas flow in a bent channel

The results are given of experimental investigations of flow of gas (air) in a curvilinear cylindrical channel. Patterns of the streamlines near the wall and the separation region were obtained by blowing cold air through a transparent model. In an investigation of the flow of hightemperature gas, in which an electric arc heater was used to supply the thermal energy, the profiles of the total pressure and the stagnation temperature were measured at different sections of the channel. It was found that the deformation of the profiles after the bend ends earlier for the hot gas than for the cold. The heat flux increases sharply after the bend.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 154–157, September–October, 1981.I thank A. B. Vatazhin for helpful discussions.     

Density-stratified Sadovskii flow in a channel

Stably density-stratified and nonstratified flows in a channel past a pair of symmetrical closed-streamline vortices on the channel axis are considered. The numerical results obtained cover the whole range of subcritical stratification and eddy lengths. An asymptotic solution for a very long closed-streamline region is found. The results can be used directly in the asymptotic theory of separated flows at high Reynolds number. Sadovskii flows are plane potential inviscid flows past a pair of closed-streamline regions of uniform vorticity. The flow velocity may be discontinuous at the boundary of the closed-streamline region. The analysis below is restricted to the specific case of continuous velocity distribution, so that the Bernoulli constant jump at the eddy boundary is zero. Unbounded nonstratified flows of this kind were studied in [1, 2]. Calculations of the corresponding channel flow were restricted to relatively wide channels. Closely related problems were also considered in [3, 4].Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.4, pp. 118–123, May–June, 1993.     

Two-fluid oscillatory flow in a channel

The validity of Navier's partial slip condition is investigated by studying the oscillatory flow in a coated channel. The two-fluid model is used to solve the unsteady viscous equations exactly. Partial slip is experienced by the core fluid. It is found that Naviers condition does not hold for an unsteady core fluid.     

Aeolian tones of a plate in a channel

The conditions of the onset of aeroacoustic resonance phenomena near a plate in a gas flow in a rectangular channel are studied theoretically and experimentally in a two-dimensional formulation. The eigenfrequency as a function of the plate's chord and its position in the channel, the shape of the eigenfunctions, and the effect of the Mach number of the basic gas flow versus the eigenfrequencies and eigenfunctions and the mechanism of self-excited oscillations are determined. A mathematical model by means of which the dependence of the resonance phenomena on the geometrical parameters of the structure were performed is proposed and substantiated. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 2, pp. 69–77, March–April, 1998.     

The penetration of a jet into a channel

The method of S. A. Chaplygin [1], as generalized by S. V. Fal'kovich [2] to the case of a few characteristic velocities, is used to solve the two-dimensional problem of the penetration of a subsonic jet of compressible fluid flowing at an angle from a slit into a stream of the same fluid bounded by parallel walls. The problem is solved for the case of an incompressible fluid by passing to the asymptotic limit. Using the tables of [3] the compression coefficient is calculated for a stream of gas merged with an incompressible fluid.     

Lifetime of a narrow channel in a liquid

Lifetime determination is considered for a narrow channel in a liquid collapsing in response to gravitational and capillary forces. Working formulas are derived to relate the lifetime to the properties of the liquid and the channel parameters. The calculations are compared with experiments on the effects of a focused high-power electron beam acting on a liquid and solid.Translated from Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 121–129, January 1974.     

Numerical investigation of the shape of a laminar flame in a channel

The method of numerical integration of the nonstationary two-dimensional equations describing the essentially subsonic motions of a reacting gas is used to investigate the characteristics of the shape and structure of the flame front propagating in a plane closed channel. It is shown that at fairly high Reynolds numbers a two-humped front shape (tulip), caused by the development of hydrodynamic flame instability, is formed.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 67–73, May–June, 1994.     

Induced flow close to the entry of a jet into a channel

The flow investigated here appears as a result of the ejecting action of a turbulent jet in conditions when a jet, after emerging from a cylindrical nozzle, impinges into a gas flow channel. Such conditions occur in gas distribution systems. A review of the investigations of flows induced by jets and the solution of a number of problems are contained in [1]. A distinctive feature of the problem investigated below is the stronger development of local characteristics and the specific flow geometry, and also its spatial inhomogeneity. The method of integral transforms is used and formulas for determining the velocity about the nozzle and the flow in the vicinity of jet entry into the gas channel are obtained.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 126–133, January–February, 1976.The author thanks T. Kh. Sedel'nikov for valuable suggestions.     

Arrival of a shock wave at the expanding part of a channel

In this paper the flow of an ideal gas, observed with the arrival of a shock wave at the expanding part of a channel is discussed. It proposes a scheme of the flow approximately modeling the complex of discontinuities arising in this case.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 191–193, November–December, 1978.     

On the dispersion of a solute in oscillating flow through a channel

The paper presents an exact analysis of the dispersion of a solute in an incompressible viscous fluid flowing slowly in a parallel plate channel under the influence of a periodic pressure gradient. Using a generalised dispersion model which is valid for all times after the solute injection, the diffusion coefficientsK _i (τ)(i=1,2,3,…) are determined as functions of timeτ when the initial distribution of the solute is in the form of a slug of finite extent. The second coefficientK ₂(τ) gives a measure of the longitudinal dispersion of the solute due to the combined influence of molecular diffusion and nonuniform velocity across the channel cross-section. The analysis leads to the novel result thatK ₂(τ) consists of a steady partS and a fluctuating partD ₂(τ) due to the pulsatility of the flow. It is shown thatS increases with increase inλ (the amplitude of pressure pulsation) for small values ofω (the frequency of the pulsation). But for largeω, S decreases with increase inλ. It is also found that for fixedλ, there is very little fluctuation inD ₂(τ) forω=1, butD ₂(τ) shows fluctuation with large amplitude whenω slightly exceeds unity. The amplitude ofD ₂(τ) then decreases with further increase inω. Thus the variation of bothS andD ₂(τ) withω is non-monotonic. Finally,? _m , the average concentration of the solute over the channel cross-section is determined for various values ofλ andω.