Study of vibration and its effect on health of the motorcycle rider

The motorcycle riders are subjected to extreme vibrations due to the vibrations of its engine, improper structural design of the motorcycle and the bad road conditions. The literature review reveals that the vibrations are most hazardous to the health if it exceeds the limit. The experiments were conducted to measure the magnitude of the vibrations acting on the rider during motorcycle riding under various road conditions. Experimental values of accelerations and frequencies which are beyond permissible limits according to the literature confirm that vibration certainly affects health of the motorcycle rider

Effects of Coriolis force and different basic temperature gradients on Marangoni ferroconvection

The effect of Coriolis force and different forms of basic temperature gradients on the onset of Marangoni ferroconvection in a horizontal layer of ferrofluid is investigated theoretically. The lower boundary is assumed to be rigid-isothermal, while the upper free boundary on which the surface tension acts is non-deformable and insulating to temperature perturbations. The Galerkin technique is used to obtain the critical stability parameters. It is shown that convection sets in as oscillatory motions provided that the Prandtl number is less than unity. A mechanism for suppressing or augmenting Marangoni ferroconvection by rotation, nonlinearity of magnetization and different forms of basic temperature gradients is discussed in detail. It is found that the inverted parabolic temperature profile indicates a reinforcement of stability, whereas the step function temperature profile indicates a diminution of stability. Comparisons of results between the present and the existing ones are made under the limiting conditions and good agreement is found

Effect of Cubic Temperature Profiles on Ferro Convection in a Brinkman Porous Medium

The effect of cubic temperature profiles on the onset ferroconvection in a Brinkman porous medium in presence of a uniform vertical magnetic field is studied. The lower and upper boundaries are taken to be rigid-isothermal and ferromagnetic. The Rayleigh-Ritz method with Chebyshev polynomials of the second kind as trial functions is employed to extract the critical stability parameters numerically. The results indicate that the stability of ferroconvection is significantly affected by cubic temperature profiles and the mechanism for suppressing or augmenting the same is discussed in detail. It is observed that the effect of Darcy number magnetic number and nonlinearity of the fluid magnetization parameter is to hasten, while an increase in the ratio of viscosity parameter and Biot number is to delay the onset of ferroconvection in a Brinkman porous medium. Further, increase in and decrease in is to decrease the size of the convection cells

On the stability of natural convection in a porous vertical slab saturated with an Oldroyd-B fluid

The stability of the conduction regime of natural convection in a porous vertical slab saturated with an Oldroyd-B fluid has been studied. A modified Darcy�s law is utilized to describe the flow in a porous medium. The eigenvalue problem is solved using Chebyshev collocation method and the critical Darcy�Rayleigh number with respect to the wave number is extracted for different values of physical parameters. Despite the basic state being the same for Newtonian and Oldroyd-B fluids, it is observed that the basic flow is unstable for viscoelastic fluids�a result of contrast compared to Newtonian as well as for power-law fluids. It is found that the viscoelasticity parameters exhibit both stabilizing and destabilizing influence on the system. Increase in the value of strain retardation parameter � 2 portrays stabilizing influence on the system while increasing stress relaxation parameter � 1 displays an opposite trend. Also, the effect of increasing ratio of heat capacities is to delay the onset of instability. The results for Maxwell fluid obtained as a particular case from the present study indicate that the system is more unstable compared to Oldroyd-B fluid. © 2016, Springer-Verlag Berlin Heidelberg

Non-darcian Effects on Double Diffusive Convection in a Sparsely Packed Porous Medium

The linear and non-linear stability of double diffusive convection in a sparsely packed porous layer is studied using the Brinkman model. In the case of linear theory conditions for both simple and Hopf bifurcations are obtained. It is found that Hopf bifurcation always occurs at a lower value of the Rayleigh number than one obtained for simple bifurcation and noted that an increase in the value of viscosity ratio is to delay the onset of convection. Non-linear theory is studied in terms of a simplified model, which is exact to second order in the amplitude of the motion, and also using modified perturbation theory with the help of self-adjoint operator technique. It is observed that steady solutions may be either subcritical or supercritical depending on the choice of physical parameters. Nusselt numbers are calculated for various values of physical parameters and representative streamlines, isotherms and isohalines are presented

Linear and Weakly Nonlinear Triple Diffusive Convection in a Couple Stress Fluid Layer

The effect of couple stresses on linear and weakly nonlinear stability of a triply diffusive fluid layer is investigated. Several departures not observed either in singly or doubly diffusive couple stress fluid layer have been identified while analyzing the linear stability of the problem. In contrast to the doubly diffusive couple stress fluid system, oscillatory convection is found to occur even if the diffusivity ratios are greater than unity. The presence of couple stress is to increase the threshold value of solute Rayleigh number beyond which oscillatory convection is preferred. Moreover, disconnected closed oscillatory neutral curves are identified for certain choices of physical parameters indicating the requirement of three critical values of Rayleigh number to specify the linear stability criteria instead of the usual single value. Besides, heart-shaped oscillatory neutral curves are also found to occur in some cases and the effect of couple stress parameter on some of these unusual behaviors is analyzed. A weakly nonlinear stability analysis is performed using modified perturbation technique and the stability of steady bifurcating non-trivial equilibrium solution is discussed. Heat and mass transfer are calculated in terms of Nusselt numbers and the influence of various physical parameters on the same is discussed in detail

Stability of natural convection in a vertical dielectric couple stress fluid layer in the presence of a horizontal AC electric field

The combined effect of couple stresses and a uniform horizontal AC electric field on the stability of buoyancy-driven parallel shear flow of a vertical dielectric fluid between vertical surfaces maintained at constant but different temperatures is investigated. Applying linear stability theory, stability equations are derived and solved numerically using the Galerkin method with wave speed as the eigenvalue. The critical Grashof number Gc, the critical wave number ac and the critical wave speed cc are computed for wide ranges of couple stress parameter  Λc, AC electric Rayleigh number Rea and the Prandtl number Pr. Based on these parameters, the stability characteristics of the system are discussed in detail. The value of Prandtl number at which the transition from stationary to travelling-wave mode takes place is found to be independent of AC electric Rayleigh number even in the presence of couple stresses but increases significantly with increasing Λc. Moreover, the effect of increasing Rea is to instill instability, while the couple stress parameter shows destabilizing effect in the stationary mode but it exhibits a dual behavior if the instability is via travelling-wave mode. The streamlines and isotherms presented demonstrate the development of complex dynamics at the critical state