The thermal instability of Walters' (model B') fluid in a porous medium is considered in the presence of a uniform vertical magnetic field to include the effect of Hall currents. For the case of stationary convection, the magnetic field has the stabilizing effect on the system, whereas the Hall currents have destabilizing effect on the system. The porous medium permeability has both stabilizing and destabilizing effects on the system depending on the Hall parameter M. The kinematic viscoelasticity has no effect on stationary convection. The kinematic viscoelasticity and magnetic field (and corresponding Hall currents) introduce oscillatory modes in the system, which were nonexistent in their absence. The sufficient conditions for the non-existence of overstability are also obtained.
The thermal instability of electrically conducting Rivlin-Ericksen elastico-viscous fluid in porous medium is considered to include the Hall current in the presence of a vertical magnetic field. For the stationary convection, the Rivlin-Ericksen elastico-viscous fluid behaves like a viscous (Newtonian) fluid. The Hall current and medium permeability are found to have destabilizing effect, whereas the magnetic field has a stabilizing effect on the thermal instability problem for stationary convection. A sufficient condition for the non-existence of overstability is obtained.
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The problem of thermal convection in a Kuvshiniski viscoelastic fluid in a porous medium in the presence of suspended particles is considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, a Kuvshiniski fluid behaves like a Newtonian fluid and the medium permeability and the suspended partic1es have destabilizing effects on the system. Graphs have been plotted by giving numerical values to the parameters to depict the stability characteristics. The principle of exchange of stabilities is found to be satisfied.
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Rozważa się niestabilność termiczną par ciernych. Szczególną uwagę poświęcono niestabilności termicznej, która może być odpowiedzialna za zużycie zmęczeniowe. Przedstawiono badania doświadczalne niestabilności termosprężystej. Omówiono inne postacie niestabilności termicznej, między innymi niestabilność spowodowaną zależnością współczynnika tarcia od temperatury, reakcje tribochemiczne oraz zmiany sposobu tarcia.
EN
Thermal instability of friction pairs is considered. Particular attention is given to the thermoelastic instability which can be responsible for fatigue wear. Experimental study of thermoelastic instability is reported. Other modes of thermal instability are discussed, among them instabilities caused by temperature dependence of coefficient of friction, tribochemical reactions, or change in friction mode.
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The problem of thermal instability of compressible, electrically conducting couple-stress fluid in the presence of a uniform magnetic field is considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the compressibility, couple-stress and magnetic field postpone the onset of convection. Graphs have been plotted by giving numerical values to the parameters to depict the stability characteristics. The principle of exchange of stabilities is found to be satisfied. The magnetic field introduces oscillatory modes in the system that were non-existent in its absence. The case of overstability is also studied wherein a sufficient condition for the non-existence of overstability is obtained.
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The thermal instability of a layer of a Rivlin-Ericksen elastico-viscous fluid permeated with suspended particles in a porous medium acted on by a uniform magnetic field is considered. For stationary convection, the Rivlin-Ericksen elastico-viscous field behaves like a Newtonian fluid. The magnetic field is found to have a stabilizing effect, whereas suspended particles and medium permeability have a destabilizing effect for the case of stationary convection. The magnetic field introduces oscillatory modes in the systems, which were non-existent in its absence.
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