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Periodic flow of a second grade fluid due to the disks executing non-torsional oscillations in an orthogonal rheometer under the influence of a magnetic field

Ersoy H. Volkan

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 3

62--71

EN

The present paper studies the periodic flow of a second grade fluid generated by non-torsional oscillations of the disks rotating in the eccentric form under the application of a magnetic field. Subsequent to the rotational motion of the disks at a common angular velocity about two vertical axes, they perform oscillations horizontally in a symmetrical manner. The exact analytical solutions are derived for both the velocity field and the tangential force per unit area exerted on one of the disks by the fluid. Special attention is paid to the influence of the applied magnetic field and it is investigated how the magnetic field controls the flow when the frequency of oscillation is less than or equal to or greater than the angular velocity of the disks. It is found that the application of the magnetic field leads to thinner boundary layers developed on the disks and the changes in the values of the shear stress components which represent the tangential force exerted on the disks occur at larger amplitude.

2

Dynamical study of Lyapunov exponents for Hide's coupled dynamo model

Alresheedi Teflah, Allahem Ali

Demonstratio Mathematica

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2021

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Vol. 54, nr 1

189--195

EN

In this paper, we introduced the Lyapunov exponents (LEs)as a significant tool that is used to study the numerical solution behavior of the dynamical systems. Moreover, Hide’s coupled dynamo model presents a valuable dynamical study. We simulate the convergence of the LEs of the model in three cases by means of periodic flow, regular flow, and chaos flow. In addition, we compared these cases in logic connections and proved them in a mathematical way.

3

Temperature estimating method for exhaust gases in valveless pulsejet engine

Trzeciak Adrian, Gieras Marian

Combustion Engines

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2020

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R. 59, nr 3

3--9

EN

The article describes the problem of measuring the temperature in a pulse combustion chamber. The object of the study is a valveless pulsejet. The problem is analysed on the example of exhaust gases temperature measurement. The measurement in these conditions requires the use of a sensor resistant to large changes in gas velocity and temperature and at the same time with adequatly low inertia. This excludes the use of fast and precise yet thin, resistant wire sensors or ultrafast thin film thermocouples. Finally, a temperature measurement system based on sheated thermocouples was chosen. During each test the thermocouple has its own temperature which is different from the medium temperature. In order to properly determine the measured temperature of flowing media it is necessary to take the sensor time characteristics into account. In this article the iteration method is proposed to solve this problem.

4

Analysis of pressure behavior in a temperature controlled molecular dynamic flow

Najafi H. R., Karimian S. M. H.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 3

881--892

EN

Thermo-fluid properties are required for numerical modeling of nano/micro devices. These properties are mostly obtained from results of molecular dynamics (MD) simulations. Therefore, efforts have been put in developing methods for numerical evaluation of fluid properties, such as pressure. In this paper, the pressure behavior in a controllable nanochannel flow is investigated. The nanoflow field is created by imposing a gradient of a macroscopic property such as temperature. Details of the pressure calculation method in a molecular system and its sensitivity to the approximations made are described first. The effect of temperature rise in a uniform flow on the pressure field is studied next. Then, in the flow under a fixed mean velocity condition, the effect of temperature gradient as a controllable property on the pressure field of nanoflow is studied. Velocity, pressure and molecular density of nanoflows with various temperature gradients and different temperature levels are investigated as well. It has been found that the temperature level at which the temperature gradient is imposed, is important. A fixed temperature gradient will not always lead to the same pressure gradient at different temperature levels. Furthermore, quite interestingly, it is observed that at a fixed temperature gradient, with the variation of mean velocity the pressure field also varies.

5

Exact solution of MHD mixed convection periodic flow in a rotating vertical channel with heat radiation

Singh K. D.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 3

853--869

EN

Magnetohydrodynamic (MHD) mixed convection flow of a viscous, incompressible and electrically conducting fluid in a vertical channel is analyzed analytically. A magnetic field of uniform strength is applied perpendicular to the planes of the channel walls. The fluid is acted upon by a periodic variation of the pressure gradient in the vertically upward direction. The temperature of one of the plates is non-uniform and the temperature difference of the walls of the channel is high enough to induce heat transfer due to radiation. The fluid and the channel rotate in unison with an angular velocity about the axis normal to the plates of the channel. An exact analytical solution of the problem is obtained. Two cases of small and large rotation have been considered to assess the effects of different parameters involved in the flow problem. The velocity field, the amplitude and the phase angle of the shear stress are shown graphically and discussed in detail. During analysis it is found that the flow problem studied by Makinde and Mhone (2005) is incorrect physically and mathematically.