Rafael M. Digilov

Capillary Rise of a Non-Newtonian Power Law Liquid: Impact of the Fluid Rheology and Dynamic Contact Angle

The impact of non-Newtonian behavior and the dynamic contact angle on the rise dynamics of a power law liquid in a vertical capillary is studied theoretically and experimentally for quasi-steady-state flow. An analytical solution for the time evolution of the meniscus height is obtained in terms of a Gaussian hypergeometric function, which in the case of a Newtonian liquid reduces to the Lucas-Washburn equation modified by the dynamic contact angle correction. The validity of the solution is checked against experimental data on the rise dynamics of a shear-thinning cmc solution in a glass microcapillary, and excellent agreement is found.

Prediction of surface properties of metals from the law of corresponding states

Abstract The schema, previously developed by the author, for the prediction of surface tension of liquid metals (LM) from the corresponding states (CS) principle has been extended to solid metals (SM). As in the case of LM, the reduced formula for surface tension of SM has been obtained by scaling e and a characterizing the interatomic potential, with the melting point Tm(0) at atmospheric pressure and the atomic volume Ω sm 2/3 (0) T m at the melting point as macroscopic parameters. CS rules derived for the surface tension, its temperature derivatives, and also the specific surface energy are discussed and compared with the experimental data and with the counterpart rules for LM. It is shown that pressure dependence of the surface tension can be described by pressure dependence of the scaling parameters Tm(p) and Ω m (p) .

Modeling of temporally complex breathing patterns during Pd-catalyzed CO oxidation

A mathematical model is formulated to account for experimental infrared thermography observations of spatiotemporal patterns during catalytic oxidation of CO over Pd supported on a glass-fiber disk-shaped cloth in a continuous reactor with feed flowing perpendicular to and through the disk. The model predicts the following observed features: (a) The sustained pattern that the system exhibits is a breathing motion in which a hot spot expands and contracts continuously. This motion emerges due to the imposed cold-edge boundary condition and a qualitative analysis of the experiments supports this suggestion and rules out other mechanisms. (b) The emerging temporally complex patterns can be classified as mixed-mode oscillations with a large relaxation-type conversion peak superimposed with several smaller peaks. (c) The mathematical mechanism that accounts for the change in the number of smaller peaks with varying operating conditions (the reactor temperature) could be characterized as period adding. The math...

Flexural Vibration Test of a Beam Elastically Restrained at One End: A New Approach for Young’s Modulus Determination

A new vibration beam technique for the fast determination of the dynamic Young modulus is developed. The method is based on measuring the resonant frequency of flexural vibrations of a partially restrained rectangular beam. The strip-shaped specimen fixed at one end to a force sensor and free at the other forms the Euler Bernoulli cantilever beam with linear and torsion spring on the fixed end. The beam is subjected to free bending vibrations by simply releasing it from a flexural position and its dynamic response detected by the force sensor is processed by FFT analysis. Identified natural frequencies are initially used in the frequency equation to find the corresponding modal numbers and then to calculate the Young modulus. The validity of the procedure was tested on a number of industrial materials by comparing the measured modulus with known values from the literature and good agreement was found.

Trouton's rule for the law of corresponding states

Troutons empirical rule for the entropy of vaporization is shown to follow from the similarity of the potential function of molecular interaction, hence is associated with the law of corresponding states. This fact explains the deviations from the rule for different groups of substances.

Development of e-health network for in-home pregnancy surveillance based on artificial intelligence

The goal of the project is a telemedicine network of smart in-home monitoring systems for outpatient pregnancy surveillance to ensure early detection of pregnancy complications and fetal pathologies, as well as ubiquitous information support of pregnancy care both antenatal and intrapartum.

Flexural vibration test of a cantilever beam with a force sensor: fast determination of Young's modulus

We describe a simple and very inexpensive undergraduate laboratory experiment for fast determination of Youngs modulus at moderate temperatures with the aid of a force sensor. A strip-shaped specimen rigidly bolted to the force sensor forms a clamped–free cantilever beam. Placed in a furnace, it is subjected to free-bending vibrations followed by a fast Fourier transform for identifying the resonant frequency, whereby Youngs modulus is calculated from the Euler–Bernoulli beam model. Room temperature moduli obtained for a series of diverse industrial materials (stainless steel, copper, aluminium, Perspex, wood and getinax) are in excellent agreement with the available literature data. The temperature dependence of Youngs modulus for stainless steel measured over the 300–600 K interval is analysed.

Catalytic spatiotemporal thermal patterns during CO oxidation on cylindrical surfaces: Experiments and simulations

Dynamics of spatiotemporal thermal patterns during the catalytic CO oxidation over Pd supported on a glass-fiber catalytic cloth rolled into a tube of 20 mm diameter and 80 mm length has been studied in a continuous flow reactor by IR thermography. A specially designed aluminum mirror built in the reactor provided image of the entire surface of the horizontally held catalytic tube. With flow in the main axial direction and through the tube surface, we observed periodic motions of a pulse, which was born downstream and propagated upstream. The temperature pulse motion was accompanied by conversion oscillations of CO2. With flow in the main axial direction, parallel to the surface, we observed a stationary hot zone after an oscillatory transient. These patterns can be simulated with a plug-flow-reactor-like heterogeneous reactor model that incorporates previously determined kinetic and transport parameters.

The shape function of a free-falling laminar jet: Making use of Bernoulli's equation

The shape function of a laminar liquid jet issuing from a circular orifice and falling vertically in air under gravity is analyzed. The diameter of the jet is observed to decrease with the axial distance from the nozzle. The governing equation for variation of the jet radius with the axial coordinate is derived from a modified Bernoullis law, including the interfacial energy density and viscous losses. The analytical solution found in terms of dimensionless group numbers agrees well with experimental data.

Mass-controlled capillary viscometer for a Newtonian liquid: viscosity of water at different temperatures.

The operation principle of the mass-controlled capillary viscometer is presented for a Newtonian liquid. The derived equation for the temporal changes of the mass in a liquid column draining under gravity through a discharge capillary tube accounts self-consistently for the inertial convective term associated with the acceleration effect. The viscosity of water measured at different temperatures using the new approach is in good agreement with literature data.