Flow and heat transport in slotted channels with obstacles

We study the flow conditions in narrow channels with obstacles of various shapes at small and moderate Reynolds numbers. The observed flow conditions are compared with experimental data on heat transfer in a channel with obstacles.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 115–118, January–February, 1971.     

Structure of a supersonic jet of an argon-helium mixture in a vacuum

Results of an experimental investigation of barodiffusion processes in supersonic jets of argon and helium mixtures by using an electron beam are presented.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 158–163, September–October, 1970.     

The use of precision castings in the three-dimensional photoelastic analysis of threaded tubular connections

A new, room-temperature formulated, epoxy-resin system with superior stress-freezing photoelastic properties is presented. The ease of producing relatively large, high-quality, precision castings is discussed. Stress-optical, rheological, and mechanical properties are given. Cylindrical tubes joined by integrally cast Stub Acme and American Standard rolled thread profiles with typical geometric parameters are loaded in tension and analyzed using the stressfreezing method. Results are presented for surface axial stress distributions for the wall surfaces opposite the threaded profiles. Additionally, the fillet stress distribution for the first engaged thread as a function of the distance along the thread helix from the location of initial contact is presented. Comparison with a finite-element analysis is given. Paper was presented at the 1983 SEM Spring Conference on Experimental Mechanics held in Cleveland, OH on May 15–19.     

Single-phase natural circulation in a tilted square loop

Natural circulation of water in a tilted square loop of circular cross-section is studied in this paper. Heating is by an electrical resistance and cooling through a heat exchanger. Heating and cooling are at opposite sides of the square loop. The natural convection flow is determined experimentally as a function of the heating flux and the tilt angle. Multiplicity of steady-state velocities is experimentally confirmed.

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Einphasiger Naturumlauf in einem geneigten quadratischen Loop

Zusammenfassung In dem Aufsatz wird der Naturumlauf von Wasser in einem geneigten quadratischen Loop mit Rohren kreisförmigen Querschnittes behandelt. Die Beheizung erfolgt über einen elektrischen Widerstand und die Kühlung über einen Wärmetauscher. Heizung und Kühlung sind auf den gegenüberliegenden Seiten des quadratischen Loops angeordnet. Der Naturumlauf wird experimentell als Funktion des Wärmestromes und des Neigungswinkels bestimmt. Es wird die Vielfältigkeit von stationären Geschwindigkeiten experimentell bestätigt.

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Nomenclature Q input heat flow - V fluid velocity - V _m maximum fluid velocity - tilt angle - _c critical tilt angle - T temperature difference     

Evaporation and condensation growth of a droplet in a vapor-gas medium for arbitrary knudsen numbers

In this paper, a study is made of the weak isothermal and nonisothermal evaporation of a particle, taking account of thermodiffusion, for arbitrary Kn numbers, evaporation-condensation coefficient , vapor concentration c, and arbitrary potential of intermolecular interaction.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 131–137, July–August, 1985.     

Evaluation of the energy efficiency of heat addition upstream of the body in a supersonic flow

Criteria for evaluating the energy efficiency of heat addition upstream of the body in a supersonic gas flow are obtained. Based on the functional objectives of flying vehicles and the thermodynamic model of the process, estimates are obtained for missile and aircrafttype vehicles. The minimum Mach numbers at which heat addition upstream of the body is reasonable are evaluated. The increase in the flight range in the cruising regime for an aircrafttype vehicle and on the active trajectory for a missiletype vehicle is evaluated. Estimates for fuel economy in launching an aerospace plane into an Earth orbit are given. It is shown that a significant part of the fuel should be spent on producing energy for gas heating in order to obtain a noticeable effect. The minimum necessary efficiency" of conversion of the fuel energy into the gasheating energy is evaluated.     

Can People Predict Chaotic Sequences?

Previous studies suggesting that people predict chaotic sequences better than chance have not discriminated between sensitivity to nonlinear determinism and facilitation using autocorrelation. Since prediction accuracy declines with increases in the look-ahead window in both cases, a decline in prediction accuracy does not imply chaos sensitivity. To overcome this problem, phase-randomized surrogate time series are used as a control. Such series have the same linear properties as the original chaotic sequence but contain no nonlinear determinism, i.e. chaos. In the experimental task, using a chaotic Hénon attractor, participants viewed the previous eight days temperatures and then predicted temperatures for the next four days, over 120 trials. The control group experienced a sample from a corresponding phase-randomized surrogate series. Both time series were linearly transformed to provide a realistic temperature range. A transformation of the correlation between observed and predicted values decreased over days for the chaotic time series, but remained constant and high for the surrogate series. The interaction between the days and series factors was statistically significant, suggesting that people are sensitive to chaos, even when the autocorrelation functions and power spectra of the control and experimental series are identical. Implications for the psychological assessment of individual differences in human prediction are discussed.     

A new micromechanical formulation of martensite kinetics driven by temperature and/or stress

Summary Martensitic transformation behavior of alloys is studied under the arbitrary action of a thermal and/or a triaxial mechanical load-stress state by solving a transformation kinetic equation presented recently by the same authors. Numerical and analytical solutions reveal that the transformation behavior is almost path-independent. Lines of constant volume fraction of martensite are nearly parallel in the stress-temperature plane. Some new analytical formulae for martensitic transformation kinetics are presented.

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Eine neue mikromechanische Formulierung der Martensit-Kinetik unter Temperatur- und/order Spannungsbelastung

Übersicht Es wird das Verhalten der martensitischen Umwandlung von Legierungen unter beliebiger thermischer und/oder dreiachsiger mechanischer Spannungsbelastung untersucht, indem eine neue Gleichung der Umwandlungskinetik gelöst wird. Diese Gleichung wurde vor kurzem von denselben Autoren vorgestellt. Die numerischen und die analytischen Lösungen zeigen, daß das Transformationsverhalten nahezu pfadunabhängig ist. Die Linien gleicher Volumsfraktion von Martensit sind nahezu parallel im Spannungs-Temperatur-Diagramm. Es werden auch einige neue analytische Formeln für die Umwandlungskinetik von Martensit präsentiert.

     

On boundedness of the motions of weakly connected nonlinear systems

Conclusions A general theorem on the boundedness of motions of weakly connected systems is established based on the Lyapunov function method and a comparison principle. Sufficient conditions for uniform boundedness contain the condition of sign-determinacy of a special matrix. A problem on the uniform ultimate-boundedness of motion of a nonlinear system with weak linear bonds is solved as an example.Institute of Mathematics, Academy of Sciences of the Ukraine, Kiev. Kiev University, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 29, No. 3, pp. 68–73, March, 1993.