Multimode Pulsations In The Axisymmetric Cavern At Supersonic Flow

Experimental study results of flow structure and pressure pulsation spectral characteristics of axisymmetric cavern at supersonic flow with Mach number 2 is presented. Multimode pulsation existence is observed. Different modes dominate in different time moments. Maximum of one mode amplitude correspond to minimum value of another. Mode tuning nature is incidental. Time of one mode existence is much more than one of mode oscillation period. It is determine that pulsation mode exist in the form of toroidal and helical disturbances. Numerical calculation results qualitative reproduce multimode fluctuation and corresponded to experimental data

Analysis of the Particles’ Movement Over the Flat and Profiled Rotating Discs surface in the Velocity Layer of the Viscous Gas

Experiments on the rotating in the air cones with vertex angle β = 120º and flat disc shown that on frequencies Ω ≥ 2.5 hertz exists a qualitative difference in movement for the particles with diameters d ≈ 1 mm and d ≈ 0.1 mm. The particles with d ≈ 0.1 mm move in the near-surface region, the particles with d ≈ 1 mm jump up to 3 cm. Comparison of the spherical and aspheric (ellipsoid with axles d, d and 4 /3 d) particles' kinematics moving shown the inevitability of the large particles jump occurrence. Large particles come to self-oscillation regime by reason of periodically appearance of the Magnus force. Small particles are localized in the velocity layer

Origin of «Plasma», or The History of a Word

The period of plasma physics formation as a science is mythologized. Even the birthday of plasma physics and the parentage of the word «plasma» are disputed. On the eve of 80th anniversary of the paper, where the electrically neutral region of the gas discharge has been named plasma for the first time, it is noteworthy separating the truth from archaeological stratifications.

Modeling Of The Alloying Substances Distribution In The Melt During Pulsed Induction Heating Of The Substrate

Under study is the applicability of the high-frequency electromagnetic field impulse for metal heating and melting with a view to its subsequent alloying. The processes of heating, phase transition, heat and mass transfer in the molten metal, solidification of the melt are considered with the aid the proposed mathematical model. The substrate surface is covered with a layer of alloying substances. The distribution of the electromagnetic energy in the metal is described by empirical formulas. Melting and solidification of the metal is considered at the Stephan’s approximation. The flow in the liquid is described by the Navier – Stokes equations in the Boussinesq approximation. According to the results of numerical experiments, the flow structure in the melt and distribution of the alloying substances was evaluated versus the characteristics of induction heating

The Features Of The Film Flow Of Liquid Nitrogen Over The Corrugated Plates With Combined Microtexture

Experimental results on hydrodynamics of cryogenic liquid film flow over the surface of the single elements of the structured packing are presented. Based on the comparison of experimental data, the effect of microtexture form, diameter of the holes on the zones of liquid film spreading over a corrugated surface is shown for different values of the film Reynolds number. It is shown that the presence of combined microtexture (with the periodic change in its direction at the height of the sheet) leads to a better spreading of the liquid nitrogen film on the surface of the corrugated perforated sheet. Analysis of experimental data shows that the presence of the periodic zones with vertical orientation of the microchannels on the sheets with the combined microtexture provides the greater flow of liquid through the holes compared to the sheet having the horizontal direction of microtexture. The use of smaller holes, while maintaining the same total area occupied by holes, at the small degree of irrigation also leads to increasing size of the wetting zones on the sheet with combined microtexture.

Precision Four-Quadrant Current Source Vch-500-12r For Superconducting Solenoids

A precision controllable bidirectional current source 0-500A for superconducting solenoids used in particle physics experiments has been proposed. This article discusses the operation principle of the designed device including a 40-kHz voltage conversion with subsequent synchronous rectification and an approach to energy recuperation from large inductive loads. It also presents some circuit designs aimed at reducing switching losses and increasing the overall efficiency. Current instability for 8 hours of continuous operation is no more than 0.01 % of the normal current.

Tuneling Spectroscopy Study Of The Local Conductivity Features Of The Solid State Surface

The procedure of the scanning tunneling spectroscopy experiments on the base of air multimicroscope SMM2000T is developed. Highly oriented pyrolytic graphite single crystal was chosen as model sample. Proposed approach allows investigation of the local nonuniformity of the surface properties. The statistical confirmed difference of volt-ampere curves recorded over pyrolytic graphite terrace and steps determined by the structure features is shown

Physical Base Of Associated Layer Model Applied To Nanofluid Viscosity Description

The paper presents the mechanistic model for explaining the experimental data on the nanofluids viscosity, which is based on the assumption about the layer of liquid on the nanoparticles surface, which associates with them the mechanical solid inclusions. This allows us to supplement the Batchelor formula with the parameter whose selection allows us to fit it with the experimental data. Independent methods of estimating the associated layer thickness from experimental data are also presented. Its value is ~ 10 nm, which is in agreement with the papers on the flows of fluids in thin hydrophilic quartz capillaries. The physical cause of this layer formation is supposed in the structuring action of the nanoparticles surface, which is expressed in the ordering of the water molecules dipole momentum directions in the near-surface layers. This leads to the difference in the optical properties of the adjacent to the particles water layers and the bulk water, which allows one to explain the fundamentally different results of measuring the dimensions of nanoparticles in a liquid by various optical methods, both among themselves and in comparison with the nanoparticles specific surface. The methods of direct influence on the particles size distribution are also proposed which can allow us to verify the assumption (on which the considered associated layer mechanistic model essentially relies) of the possibility to group different nanopowders and introducing into the group a general parameterized function of the particle size distribution.

New Type Of Medium – Gases With High Concentration Of Nanoparticles

The article gives an overview of the works, the results of which indicate the necessity of posing the problem of describing new types of continuous media containing large concentrations of nanoscale particles. The importance of this problem is underlined for understanding modern technological processes in which nanopowders of various nature are formed, and in the form of nanoparticles whose concentration reaches significant values is increasingly used. Examples of practically important flows of powder materials are considered. The concept of a new continuous medium with a high concentration of nanoparticles is proposed, and the «hot-anemometric method» is applied.

Investigation Of The Air Flow In Heated Highly Porous Cellular Materials

Measurements of air filtration rate through the highly porous cellular materials in the presence of heating a porous material were carried out. A new measurement technique was developed and data of the dependence of the filtration rate of the temperature of air passing through the porous material were obtained with different pore size and in wide range Reynolds number. The experimental data were compared with the results of numerical modeling of the airflow in the porous samples, based on skeletal model of the cellular-porous material.