The paper discusses the neural-analytical model for the analysis and optimization of fixtures, suitable for clamping of thin-wall products likely to undergo deformation due to clamping and cutting forces during machining. A programme FIXAN has been worked out for the evaluation of fixturing scheme, for the calculation of the optimum magnitude and positioning of clamping forces required to enable the workpiece to be safely clamped during machining. The model is suitable for the analysis of fixtures intended for fixing of prismatic and cylindrical products. The model takes into consideration the friction occurring between the workpiece and the fixture components. The described procedure ensures a reduction in the time of fixture planning and prevention of defects and deformation during the machining process.

    Stability characteristics of a thin conducting liquid film flowing down, on a non-conducting plane in the presence of the electromagnetic field is investigated under the assumption of a small magnetic Reynolds number. A surface evolution equation is derived by using the long-wave approximation method. A linear and non-linear stability analysis of the evolution equation shows that the magnetic field stabilizes the flow whereas the electric field stabilizes or destabilizes the flow depending on its orientation with the flow. It is found that both the subcritical instability and supercritical stability are possible in a finite amplitude regime. Two critical Hartmann numbers M_c and M_c>(M_c) are observed for subcritical and supercritical zones respectively. The existence of a subcritical unstable zone may be ruled out when M_c>M_c which is independent of other parameters whereas supercritical and explosive zones are possible till M_c<M_c which depends on flow parameters.

    An analysis is performed to study the transient free convection flow of a viscous incompressible fluid past a semi-infinite inclined plate with viscous dissipation. The dimensionless governing equations are unsteady, coupled and non-linear integro partial differential equations. An analytical method fails to give a solution. Hence an implicit finite difference scheme of Crank-Nicolson method is employed. The effect of the dissipation parameter on the velocity, temperature, skin friction and Nusselt number are studied in detail. It is observed that greater viscous dissipative heat causes a rise in the temperature irrespective of the Prandtl number.

    The impact of the gas density difference on formation of flow patterns of fluids of different density was analysed. Physical modelling of a non-isothermal laminar flow of a gas mixture in a vertical epitaxial reactor chamber was carried out and the model flow was visualised. Visualisation studies, performed using a smoke method, confirmed that the stability of a gas interface determines the flow pattern in the chamber. The Rayleigh-Taylor instability occurs in the flow through a reactor, which, together with the Kelvin-Helmholtz instability and with the superposition of convection flows on the principal flow, shapes the flow pattern in the whole reactor chamber. On the basis of results of visualisation studies, the possibility of making the flow through a vertical reactor stable was indicated if the inlet guide apparatus is applied and the flow direction is reversed.

    Based on the Brinkman model (BM) with the assumption that the pressure gradient across the porous region is an unknown function, the effects of viscous shear stresses upon the squeezing-film motion in porous annular disks are considered. Using the Brinkman equations and applying the continuity conditions at the interface for the velocities, shear stresses and pressures, two coupled modified Reynolds equations governing the squeeze-film pressure are obtained. The film pressure equation is solved and applied to evaluate the load-carrying capacity and the height-time relationship. According to the results obtained, the BM predicts quite a different squeezing action to those derived by the slip-flow model (SFM) and the Darcy model (DM). Comparing with the SFM, the viscous shear effects of the BM increase the load-carrying capacity and the response time. But, these trends are reversed as compared to the DM. On the whole, the effects of viscous shear stresses are more pronounced for moderate-value permeability parameters and a higher-value radius ratio. A design example for porous annular disks is also illustrated for engineering applications.

    An investigation is carried out to study theoretically the stability of a fluid-saturated anisotropic porous medium, heated from below, for the case of a time-periodic wall temperature/gravitational field. The Darcy model is employed and only the infinitesimal disturbance are considered. A method based on a small amplitude of the modulation is used to compute the critical values of the Rayleigh number and wave number. The shift in the critical Rayleigh number is calculated as a function of the frequency of the modulation, the Prandtl number, the porous parameter, and the anisotropy parameter. We found that it is possible to advance or delay the onset of convection by proper tuning of the frequency of modulation of the wall temperature or by the gravity modulation. The temperature modulation is shown to give rise to both subcritical and supercritical motions whereas gravity modulation always leads to subcritical motions. It is also found that the low-frequency thermal/gravity modulation and the small anisotropy parameter have a significant effect on the stability of the system.

    A free vibration analysis of isotropic plates is investigated in this paper. A sixteen node sub-parametric element having thirty-six degrees of freedom is developed for this purpose. The transverse displacement and bending rotations are taken as independent field variables. The polynomials used to express these variables are of the same order. The entire formulation is made based on the first-order shear deformation theory (FSDT). The rotary inertia is included in the consistent mass matrix for the analysis. Isotropic plates with different thickness ratios, aspect ratios and boundary conditions are analyzed. The results show an excellent agreement with the available published analytical results.

    The effect of radiative transfer on the onset of thermal convection in a ferromagnetic fluid layer bounded by two parallel plates and heated from below is considered using Goody's approach. The fluid between the plates absorbs and emits thermal radiation. The Milne-Eddington approximation is employed in obtaining the initial static state. Considering infinitesimal perturbations, the critical magnetic Rayleigh number is obtained using the Rayleigh-Ritz method. It is found that radiation inhibits the onset of convection in both the transparent and opaque media. Further, the opaque medium is shown to release heat for convection more slowly than the transparent medium. It is also found that radiation affects the cell size at the onset of convection in the case of transparent medium only. The results have implications in energy conversion devices and in smart material applications.

    Dams in many countries including India were primarily designed on the basis of approximate hand calculation based method. A frequent occurrence of floods due to a failure of such dams and embankments clearly points to the need of a review of the procedure of dam analysis methodologies and to suggest a reasonably accurate one. The paper is a limited effort for the same, based on three Indian dams. As a very preliminary step of the whole plan of checking the safety of Indian dams, an analysis of three dams having similar features as that of Chirpatia Dam (Rajasthan), an earthen embankment dam, Koyna Dam (Maharastra), a concrete gravity dam and the earthen embankment surrounding Ash Pond of Bakreswar Thermal Power Project (West Bengal), have been carried out with the help of two-dimensional and three-dimensional finite element discretisation under static loading conditions. The result is then compared with the corresponding results obtained from a conventional hand calculation based on approximate gravity method of analysis. The comparison of the results exhibited a considerable increase in compressive stresses in two-dimensional finite element analysis with respect to what is obtained in the conventional hand calculation based approximate gravity method. Both of these methods considered an in-plane stress distribution along a cross-section of the dam and hence, could not recognize any possibility of stress generation perpendicular to the cross-section. In this context, a three-dimensional study reveals that considerable stresses may generate even in the longitudinal direction of a dam that is generally ignored in hand calculation based gravity method of analysis and two-dimensional analysis due to the assumption of the two-dimensional nature of the problem. A rigorous finite element analysis also shows that even tensile stress may generate under static loading conditions which can hardly be predicted from the conventional method. It is also observed that hand calculation based on slip-circle method and two-dimensional analysis cannot adequately recognize the possibility of shear failure at many points in the body of the dam though their vulnerability due to itself and so it is necessary to point out by a rigorous three-dimensional modeling and analysis. Thus, the study suggests the unavoidable necessity of three-dimensional analysis for a safe design of dams.

    The combined effects of thermal radiation flux, thermal conductivity, Reynolds number and non-Darcian (Forcheimmer drag and Brinkman boundary resistance) body forces on steady laminar boundary layer flow along a vertical surface in an idealized geological porous medium are investigated. The classical Rosseland one-dimensional diffusion approximation is implemented in the energy equation to avoid solving the general integro-differential equation for radiative transfer. Pseudo-similarity transformations are invoked and the resulting highly coupled and non-linear set of ordinary differential equations for momentum and energy equations are solved numerically using a well-tested and highly accurate shooting Runge-Kutta quadrature with a Merson-Gill algorithm. It is shown that the dimensionless velocity functions generally increase with rising radiation parameter and the Prandtl number, and the dimensionless temperature functions decrease as the non-Darcian body forces decrease. It is also shown that the dimensionless temperature functions rise in magnitude with rising radiation parameter and the Prandtl number but are depressed by lowered non-Darcian resistance parameter and rising Reynolds number. Generally radiation is seen to substantially boost the overall heat transfer.

    This paper presents a closed form solution for a transient free convective flow of a viscous and incompressible fluid in a vertical channel due to symmetric heating of channel walls. The Laplace transform technique has been used to obtain the expression for the velocity and temperature fields by solving the governing differential equations. The influence of the physical parameters on the velocity field, skin-friction, rate of heat transfer and volumetric flux of the fluid are carefully analysed. A correlation between the steady state time and the Prandtl number has been developed. It is observed that the nature of correlation is linear when the Prandtl number is greater than one while cubic for the Prandtl number is less than one.

    The study of dynamics of packages of mass m delivered from a conveyor to a smooth circular ramp of radius r is important in transport technology and engineering dynamics. The present paper is devoted to reanalysing this problem since the inclusion of frictional forces results in an integro-differential equation that in general needs the utilisation of Neumann-series. The integro-differential equation thus obtained is transformed into a first order differential equation that can easily be solved analytically.