Sayavur I. Bakhtiyarov

Measurement of liquid metal viscosity by rotational technique

The rotational measurement technique has been developed to measure the dynamic viscosity of liquid metals. A special procedure is accomplished to eliminate both end and eccentricity effects. The technique was calibrated and tested with liquids of known rheology. The apparent viscosity of low melting alloy composite is measured by means of the technique.

Electrical and thermal conductivity of A319 and A356 aluminum alloys

A rotational contactless inductive measurement technique has been used to measure the electrical resistivity of A319 and A356 aluminum alloys at both solid and liquid states. The method is based on the phenomena that when a conducting material rotates in a magnetic field, circulating eddy currents are induced and generate an opposing torque, which is proportional to the electrical conductivity of the material. The technique was checked and calibrated with pure aluminum where considerable electrical resistivity data exist in the literature. Wiedemann-Franz-Lorenz law was used to estimate the thermal conductivity of A319 and A356 aluminum alloys in liquid state.

Numerical modeling and experimental verification of mold filling and evolved gas pressure in lost foam casting process

A simple mathematical model is developed to describe a lost foam casting process. Different aspects of the process, such as liquid metal flow, transient heat transfer, foam degradation and gas elimination were incorporated into this numerical model. Fluid velocity, temperature distribution within molten metal and pressure building-up in the mold cavity are predicted as a function of filling time and filling height. The model was verified by comparison of the predicted velocity profiles, temperature fields and back-pressures with the experimental data conducted in this work. Both coated and uncoated foam patterns were used in experimental part of this study. A good agreement between the predictions and the experimental data was found.

Flow of drilling fluids in eccentric annuli

The effect of pipe eccentricity on the flow of well bore fluids in annuli is investigated both analytically and experimentally. The expression for azimuthal velocity as a function of the eccentricity ratio and rheological parameters of the fluid was obtained analytically using a linear fluidity model. Velocity profiles were measured for a Newtonian glycerol/water mixture and a non-Newtonian oil field spacer fluid in eccentric annuli using the stroboscopic flow visualization method. Measured velocity profiles in the eccentric annulus compare well to analytical predictions.

Analysis of Air Flow in Single Nozzle Air-Jet Filling Insertion: Corrugated Channel Model

Air flow in air jet weaving machines is complicated: it is unsteady, turbulent, and can be compressible or incompressible depending on the velocity. A separated flow model is developed to simulate air flow through the guide channel, which is half open and corrugated. Subsonic air flow in the guide channel is investigated as a simplified model of air flow in a single nozzle air-jet filling insertion system. The drag coefficient in the guide channel and propelling force acting on the yarn are calculated. Theoretical predictions of drag coefficient and propelling force are in good agreement with ex perimental data obtained for the same conditions.

Electrical conductivity measurements in liquid metals by rotational technique

The rotational contactless inductive measurement technique has been developed to measure the electrical conductivity of liquid metals. This method is based on the phenomena when a conductor material rotates in a magnetic field, circulating eddy currents are induced and generate a damping torque proportional to the electrical resistivity of the material. The technique was tested to measure the conductivity of five conductors and one low melting composite (LMA-158).

Fluid displacement in a horizontal tube

Abstract The displacement of Newtonian fluids by non-Newtonian fluids in a horizontal cylindrical tube has been investigated both theoretically and experimentally. Theoretical expressions for the breakthrough time, a function of the constitutive constants of the fluids and of the flow parameters and geometry, are derived when the displacing fluids are either of the inelastic viscous or viscoelastic type. The dynamics of the displacement process is studied experimentally using the photometric method and an oil field spacer fluid and glycerol-water mixtures as the displacing and displaced fuids, respectively. The ratio of the zero shear viscosities of the displacing and displaced fluids plays a crucial role when the displacing fluid is characterized either by a viscoelastic or a viscoinelastic structure. The density ratio of the displacing and displaced fluids is close to one in our experiments as it may be in most field operations. We show that characterization of this type of spacer fluid by a viscoelastic model at moderate pressure gradients will not lead to good predictions of the breakthrough time when the viscosity of the displaced crude is much smaller than that of the displacing spacer fluid, that is, for high values of the zero shear viscosity ratios which may be desirable for high efficiency displacement processes.

Fraction Solid Measurements on Solidifying Melt

A new indirect method to measure fraction solid in molten metals is presented. The method is based on the phenomena that when a metal sample (solid or liquid) rotates in a magnetic field (or the magnetic field rotates around a stationary sample), circulating eddy currents are induced in the sample, which generate an opposing torque related to amount of solid phase in a solidifying melt between the liquidus and solidus temperatures. This new technique is applied for measuring fraction solid on commercial A319 aluminum alloy. The solidification curves obtained by the proposed method at different cooling rates are in good agreement with predictions made by the Scheil model.

Numerical Simulation of Steady Liquid-Metal Flow in the Presence of a Static Magnetic Field

We describe a novel approach to the mathematical modeling and computational simulation of fully three-dimensional, electromagnetically and thermally driven, steady liquid-metal flow. The phenomenon is governed by the Navier-Stokes equations, Maxwells equations, Ohms law, and the heat equation, all nonlinearly coupled via Lorentz and electromotive forces, buoyancy forces, and convective and dissipative heat transfer. Employing the electric current density rather than the magnetic field as the primary electromagnetic variable, it is possible to avoid artificial or highly idealized boundary conditions for electric and magnetic fields and to account exactly for the electromagnetic interaction of the fluid with the surrounding media. A finite element method based on this approach was used to simulate the flow of a metallic melt in a cylindrical container, rotating steadily in a uniform magnetic field perpendicular to the cylinder axis. Velocity, pressure, current, and potential distributions were computed and compared to theoretical predictions.

An Inductive Technique for Electrical Conductivity Measurements on Molten Metals

A computer-controlled rotational technique to measure the electrical resistivity of solid and molten metals was developed. The electrical resistivities of pure metals (aluminum, indium, lead, and tin) and the low-melting point alloy LMA-158 in the solid and liquid states were measured. The results also show that there is a linear relationship between electrical resistivity and temperature in both the solid and the liquid states of the test materials. Good agreement was found between the experimental data and predictions from the literature. The data were used to estimate the temperature coefficients of electrical resistivity of test specimens over a wide range of temperatures including the melting point of the metals. Good agreement between experimental data and predictions made by previous researchers for the temperature coefficients was achieved.