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1
Content available remote Zastosowanie konwekcji cieplnej do określania kierunku przepływu dwuwymiarowego
Jamróz P.
Prace Instytutu Mechaniki Górotworu PAN
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2017
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T. 19, nr 1
35--43
PL
W artykule przedstawiono badania nad możliwością wykorzystania zjawiska konwekcji cieplnej do określania kierunku przepływów. Rozwiązanie takie mogłoby znaleźć zastosowanie w warunkach pomiarów przepływów cechujących się niskimi wartościami prędkości i fluktuacjami kierunku. W oparciu o przedstawioną ideę pomiaru opracowano prototypowy czujnik wyposażony w cienkie włókna termorezystancyjne pozwalające na określanie chwilowych wartości temperatury i wykonano badania laboratoryjne na stanowisku do pomiarów charakterystyk kątowych czujników termoanemometrycznych.
EN
The article presents studies on the use convective heat for determination the air fl ow direction. This solution could be applied in case of two-dimensional fl ows measurements, characterized by low velocity range and fl ow direction fl uctuations. Based on described idea of measurement, a prototype sensor was developed. The sensor was equipped with eight temperature probes made of the very thin (5 μm diameter) wires. The laboratory tests were performed using the modernised measurement stand dedicated to determine of anemometers sensors characteristic.
2
Content available Global stability for thermal convection in a couple-stress fluid with temperature and pressure dependent viscosity
Choudhary S. S., Bharti P. K.
Studia Geotechnica et Mechanica
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2013
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Vol. 35, nr 3
85--102
EN
We show that the global nonlinear stability threshold for convection in a couple-stress fluid with temperature and pressure dependent viscosity is exactly the same as the linear instability boundary. This optimal result is important because it shows that linearized instability theory has captured completely the physics of the onset of convection. It has also been found that the couplestress fluid is more stable than the ordinary viscous fluid and then the effect of couple-stress parameter (F) and variable dependent viscosity (Γ) on the onset of convection is also analyzed.
3
Content available Triple- diffusive convection in a micropolar ferrofluid in the presence of rotation
Chand S.
International Journal of Applied Mechanics and Engineering
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2013
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Vol. 18, no. 2
307--327
EN
This paper deals with the theoretical investigation of the triple-diffusive convection in a micropolar ferrofluid layer heated and soluted below subjected to a transverse uniform magnetic field in the presence of uniform vertical rotation. For a flat fluid layer contained between two free boundaries, an exact solution is obtained. A linear stability analysis theory and normal mode analysis method have been employed to study the onset convection. The influence of various parameters like rotation, solute gradients, and micropolar parameters (i.e., the coupling parameter, spin diffusion parameter and micropolar heat conduction parameter) on the onset of stationary convection has been analyzed. The critical magnetic thermal Rayleigh number for the onset of instability is also determined numerically for sufficiently large value of the buoyancy magnetization parameter M1 (ratio of the magnetic to gravitational forces). The principle of exchange of stabilities is found to hold true for the micropolar fluid heated from below in the absence of micropolar viscous effect, microinertia, solute gradient and rotation. The oscillatory modes are introduced due to the presence of the micropolar viscous effect, microinertia , solute gradient and rotation, which were non-existent in their absence. In this paper, an attempt is also made to obtain the sufficient conditions for the non-existence of overstability.
4
Content available remote Thermal convection in a compressible Walters' (model b') elastico-viscous dusty fluid with hall currents
Vikrant, Kumar V., Jaimala
International Journal of Applied Mechanics and Engineering
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2011
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Vol. 16, no 4
1189-1203
EN
A compressible Walters' (Model B') elastico-viscous dusty fluid layer heated from below in the presence of a vertical magnetic field to include the effect of Hall currents is considered. For the case of stationary convection, Walters' (Model B') elastico-viscous fluid behaves like an ordinary Newtonian fluid. The Hall currents and dust particles are found to have a destabilizing effect on the thermal convection, whereas compressibility and the magnetic field are found to have a stabilizing effect on the thermal convection. The viscoelasticity and magnetic field (and hence the Hall currents) introduce oscillatory modes in the system, which were non-existent in their absence. Graphs are also plotted for the critical Rayleigh number and various parameters by giving some numerical values to the parameters
5
Content available remote Thermal convection in a Walters' (model B') elastico-viscous dusty fluid in hydromagnetics with the effect of compressibility and rotation
Kumar V., Aggarwal A. K., Kumar S.
International Journal of Applied Mechanics and Engineering
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2010
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Vol. 15, no 1
51-62
EN
A compressible, electrically conducting Walters'B' elastico-viscous fluid heated from below in the presence of a magnetic field and rotation is considered. At stationary convection, Walters' (Model B') elastico-viscous fluid behaves like a Newtonian fluid and compressibility, rotation are found to have a stabilizing effect whereas the suspended particles have a destabilizing effect on the thermal convection and magnetic field has a stabilizing effect under certain conditions. The presence of magnetic field and rotation introduces oscillatory modes in the system which were non-existent in their absence. Graphs have also been plotted by giving some numerical values to the parameters.
6
Simulation of thermal convection depending on the angle between gravity force and temperature gradient
Jopek H.
Systems : journal of transdisciplinary systems science
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2006
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Vol. 11, nr 1
29-34
EN
In this papers the influence of the angle between the gravity force and the temperature gradient on the convection process is studied and simulated. Free convection is the kind of heat transfer in which the fluid's motion is caused by the volume forces, usually by the gravity force but also due to centrifugal forces or magnetic field's forces. The differences of temperature around the body are connected to differences of density and consequently buoyant force appears. For that reason, in the equations of motion the volume force is substituted by the expression representing the difference in specific weight and bouyancy which is proportional to the difference of density. It is a very common phenomenon that the convection appears in the film of fluid between the surfaces of two different temperatures
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