Mechanism for the anomalously long range of a “hard laminar flame”

An explanation is given for the anomalously long range of a type of laminar flame which has been termed a “hard laminar flame.” A model of an isobaric laminar jet with a given bulk energy release is used to show that the unusual properties of the flame are determined by its two-layer structure. The outer hot sheath stabilizes the flow as a whole and creates conditions for extended axial flow of the cold gas mixture. Pis’ma Zh. Tekh. Fiz. 24, 61–65 (May 12, 1998)     

Convective heat transfer in air flow around a cylinder at low Reynolds numbers

The principal objective of the present work is to conduct investigations leading to a more complete explanation of heat-transfer processes on the external wall of a heated cylinder in laminar axial flow around it under high pressures. Investigations are aimed at determination of the limits of existence of mixed convection, explanation of the influence of free convection on the disturbances of heat transfer during laminar flow of a medium, and final explanation of intensification of heat-transfer processes occurring in a flow at high pressures. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 6, pp. 163–169, November–December, 2005.     

Numerical simulation of the hemodynamics and biomechanics of the arterial system

A mathematical model of blood flow in arterial vessels with account for the nonstationary character of the laminar flow and the time-varying pressure drop is considered. The viscosity of blood is assumed to obey a power law. The rheological properties of the walls of arterial vessels are described by i) the Voigt—Kelvin model, ii) the standard-body model, and iii) the three-component Voigt—Kelvin model. As a result of numerical simulation, flow-pressure characteristics of various arteries are obtained.     

On the interaction of a vortex pair and a vortex ring with a flat shield

The approximate method of calculation of nonstationary flow in the interaction of a vortex pair and a vortex ring with a parallel and respectively perpendicular flat shield is presented. It is shown that these primary vortices induce transverse wall flow on the shield in the ideal-fluid approximation; in this flow, with allowance for the fluid’s viscosity, a boundary layer is generated which represents vortex flow with sign opposite to that of the primary vortices. Boundary-layer separations occur on the portion of the shield with a positive longitudinal pressure gradient. Secondary flows interact with the primary ones due to which the flow is rearranged; the transverse displacement of the initial vortex pair with a loop-shaped trajectory of its motion is observed in the plane problem, whereas the formation of ascending flow along the axis of the vortex ring is observed in the axisymmetric problem. The effect found in the latter case in laminar and turbulent regimes of flow is confirmed for the laminar regime by experiment and by the data of numerical simulation of Navier–Stokes and Reynolds equations.     

Surface Oscillations of an Electromagnetically Levitated Droplet

The natural oscillation frequency of freely suspended liquid droplets can be related to the surface tension of the material, and the decay of oscillations to the liquid viscosity. However, the fluid flow inside the droplet must be laminar to measure viscosity with existing correlations; otherwise the damping of the oscillations is dominated by turbulent dissipation. Because no experimental method has yet been developed to visualize flow in electromagnetically levitated oscillating metal droplets, mathematical modeling can assist in predicting whether or not turbulence occurs, and under what processing conditions. In this paper, three mathematical models of the flow: (1) assuming laminar conditions, (2) using the k−ɛ turbulence model, and (3) using the RNG turbulence model, respectively, are compared and contrasted to determine the physical characteristics of the flow. It is concluded that the RNG model is the best suited for describing this problem when the interior flow is turbulent. The goal of the presented work was to characterize internal flow in an oscillating droplet of liquid metal, and to verify the accuracy of the characterization by comparing calculated surface tension and viscosity values to available experimental results.     

Deposition of solid particles in laminar boundary layer on a flat plate

Results are given of experimental and theoretical investigation of deposition of small solid particles on the surface of a flat plate under conditions of vertical laminar boundary layer. The present investigation is aimed at qualitatively and quantitatively estimating the effect made by the parameters of two-phase flow of the “gas—solid particles” type and by the adhesive properties of particles and surface on the deposition of particles on the plate surface. The flow velocity is 1.5 and 3 m/s. In so doing, the value of Reynolds number along the plate does not exceed 10⁵. Synthetic corundum powders with average sizes of 12, 23, and 32 μm are used as the dispersed phase of two-phase flow. The mass concentration of particles in the flow is 0.01 kg/m³. A flat plate of stainless steel is used as the object of investigation. The distributions of gas velocity and concentration of particles within the boundary layer are measured using laser optical diagnostics. The number of particles deposited along the plate surface is measured by the gravimetric method. The adhesive properties of the “particle-surface” pair are studied using the centrifugal method of detachment of particles from the surface. Logarithmic-normal dependences of the number of adhesion of particles on the force of detachment are obtained. The hydrodynamic parameters of two-phase flow in the vicinity of the plate surface are calculated using the model of two-phase laminar boundary layer. The mathematical expression is suggested for the calculation of the magnitude of deposition of solid particles along the surface of a flat plate, which includes the special features of hydrodynamics of flow, the adhesive properties of the particles and surface, and the probabilistic pattern of the process of entrapment of particles by the surface.     

Interphase mass transfer between liquid-liquid counter-current flows. II. Mass transfer kinetics

A theoretical analysis of mass-transfer kinetics based on the method of similarity variables for a liquid-liquid counter-current flow has been made. The numerical results obtained for the mass-transfer rate (Sherwood number) in the case of a laminar boundary layer with a flat interphase are compared with analogous results for a co-current flow. The ratio between the mass-transfer rate and the energy dissipation in the boundary layer is determined. The advantages of the co-current flow due to lower energy losses compared with the case of the counter-current one are shown. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 86–90, July–August, 2007.     

Numerical simulation of viscous flow around a system of bodies on the basis of the Navier-Stokes equations in stream function-vorticity variables

A method of numerical solution of the Navier-Stokes equations in stream function-vortex-pressure variables is suggested to be used in simulating a nonstationary, nonsymmetric flow of a laminar incompressible viscous stream around a pair of rotating cylinders in a channel. Results of calculations which illustrate application of the method under different conditions of flow around bodies are presented. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 118–125, September–October, 2006.     

Numerical simulation of a viscous separation flow around a rotating circular cylinder

Results of numerical solution of Navier-Stokes equations in stream function-vortex variables for a nonstationary laminar flow around a circular cylinder with a rotational degree of freedom are presented. The cases of definite, free, and inertial rotation of the indicated cylinder were considered. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 75–81, May–June, 2006.     

Mathematical simulation of a nonstationary thermal field in the “well-being-drilled–rocks” system

A mathematical model and results of calculation of a nonstationary thermal field in the process of drilling a well in rocks having different thermophysical properties, with a laminar mode of flow of the drilling mud, are considered. The distributions of temperature over the well bore in different drilling regimes are given. It is shown that when the drilling is stopped, the temperature anomalies in the well are preserved for 24–48 h in the intervals of alive beds. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 85–85, September–October, 2006.     

Dynamics of the viscous interaction of a ring vortex with a flat screen

A separation turbulent flow has been mathematically simulated on the basis of numerical solution of nonstationary Navier-Stokes equations for determining the dynamics of viscous interaction of a ring vortex with a flat screen. The problem was solved for an axisymmetric turbulent flow at Reynolds numbers falling within the range 10⁵–10⁷. On the basis of the calculation data obtained, the interaction of a ring vortex with a turbulent flow induced on the screen and with the secondary ring vortices was investigated. The data obtained are in qualitative agreement with the analogous data obtained by other authors with the use of the discrete-vortex method and the boundary-layer theory as well as with the available experimental and calculation data obtained for a laminar flow. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 1, pp. 184–190, January–February, 2008.     

Stability of thermocapillary convection and regimes of a fluid flow acted upon by a standing surface wave

It has been established that, in the case where a standing surface wave acts on a thermocapillary-convection flow in a cylindrical volume, there arises an oscillating-convection zone between the laminar and turbulent regimes of flow. It is shown that the boundary between these regimes is determined by the amplitude δ and the number of periods n of the standing wave and is practically independent of the Marangoni number and the oscillation frequency of this wave. At n = 2, in the range 0.004 < δ < 0.006, the parameters of the fluid cease to oscillate. The mechanisms by which the thermocapillary convection in closed volumes loses its stability are discussed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 108–115, September–October, 2007.     

Novel water flow facility in france range extension to low flow rates (10 000 ml/h down to 1 ml/h)

In order to extend the French water flow calibration range, LNE-CETIAT is on progress to build a new reference for flow rate measurements ranging from 10 000 ml.h⁻¹ down to 1 ml.h⁻¹. This new facility based on a gravimetric principle will enable calibration with water temperature between 10 °C and 50 °C. Flow is regulated by the combined use of a tightly regulated “upstream” pressure (0,1 to 10 bar) and the use of capillaries under laminar flow. The expected relative uncertainty for the water flow rate is 0.1 % with a coverage factor k = 2 (95% confidence). The paper described the design and the ongoing implementation of this new calibration facility.     

Heat transfer to an ascending laminar flow of hydrocarbons under supercritical pressure conditions

Some results of experimental investigations of heat transfer of n-heptane in a laminar forced flow under the conditions of supercritical pressures are presented, and equations to estimate the intensity of heat transfer under viscous and viscous-gravitational conditions are suggested. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 91–95, July–August, 2006.     

Interphase mass transfer between liquid-liquid counter-current flows. I. Velocity distribution

A theoretical analysis of liquid-liquid counter-current flow in laminar boundary layers with a flat interphase based on the similarity-variables method has been made. The numerical results for the velocity distribution in both phases are obtained. The dissipation energy in a boundary layer is found and the results corresponding to counter-current and co-current flows are compared. The comparison shows significant differences in the dissipation energy values in the cases of co-current and counter-current flows. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 80–85, July–August, 2007.     

Two-fluid pressure-driven channel flow with wall deposition and ageing effects

Two-fluid, stratified pressure-driven channel flow is studied in the limit of small viscosity ratios. Cases are considered in which the core fluid undergoes phase separation that results in the ‘precipitation’ of a distinct phase and the formation of a wall layer; these situations are common in the oil industry where ‘fouling’ deposits are formed during the flow. The thickness of this layer increases as a result of continual deposition through Stefan-like fluxes, which are related to the phase behaviour of the core fluid through a chemical equilibria model that treats the fluid as a bi-component mixture. The deposit also undergoes an ‘ageing’ process whereby its viscosity increases due to the build-up of internal structure; the latter is modelled here via a Coussot-type relation. Lubrication theory is used in the wall layer and an integral balance in the core fluid wherein inertial effects are important. By choosing appropriate semi-parabolic velocity and temperatures closures for the laminar flow in the channel core, and a closure relation for the wall layer rheology, evolution equations are derived that describe the flow dynamics. In the presence of ageing but absence of deposition, it is demonstrated how the time-varying deposit rheology alters the wave dynamics; for certain parameter ranges, these effects can give rise to the formation of steep waves and what appears to be finite-time ‘blow-up’. With both ageing and deposition, the spatio-temporal evolution of the deposit is shown together with the increase in the deposition rate with increasing temperature difference between the wall and the inlet.     

Excitation of self-oscillations in flow past a surface with a recess and the possibility of preventing them

The results of experimental investigations of acoustic radiation initiated by hydrodynamic perturbations at the inlet to a cavity on a surface with a stream flowing past it are analyzed. A comparison is made between the processes of formation of large-scale hydrodynamic vibrations in a shear flow shed from the leading edge of the junction of the recess with the surface past which a stream flows and the processes in the region of transition from a laminar boundary layer on the surface of a wing to a turbulent one. The advisability of division of the flow inhomogeneity in the zone of the junction in order to prevent or weaken self-oscillations in the flow is estimated. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 3, pp. 148–154, May–June, 2007.     

Experimental Investigation of a Bubbly Two-Phase Flow in an Open Capillary Channel under Microgravity Conditions

The study of a bubbly laminar two-phase flow in an open capillary channel under microgravity conditions was conducted aboard the sounding rocket, Texus-45. The channel geometry, the liquid (FC-72) and the experimental conditions were chosen based on an analysis for application toward liquid management in space. The channel consists of two parallel plates that were b = 25 mm wide and separated by a distance of a = 10 mm. The flow along the length l = 80 mm is bounded by a free surface on one side and a plate on the opposite side. Bubbles are injected at the inlet of the capillary channel via six capillary tubes. The features of the gas injection were chosen with regard to the required bubble size, the injection frequency, and the gas and liquid flow rates. Different liquid and gas flow rates were tested leading to a volumetric quality ranging between 0.07 and 0.11. The experimental results show the interaction among bubbles and with the liquid free surface.     

Effect of gel formation on the process of laminar continuous-flow ultrafiltration

We investigate the process of ultrafiltration with gel formation in laminar flow in a plane channel in the case of nonideal selectivity of the membrane. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 1, pp. 166–172, January–February, 1998.     

Rise of a Single Bubble in Ascending Laminar Flow: Slip Velocity and Wall Friction

An experimental study has been made of the motion of single bubbles in ascending laminar flow in a vertical pipe. An electrodiffusion procedure has been used for visualization of wall friction in passage of a single bubble. Time realization of friction stress is considered as the structure frozen-in into the flow and moving along the flow together with the bubble. The experiments have revealed the complex structure of wall-friction stress, which corresponds to different components of interaction of the bubble with the wall. The evolution of these components as a function of the Reynolds numbers of the bubble and the pipe is discussed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 129–135, July–August, 2005.