Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 5 Articles
In this work, the fluid mechanics performance of four different contraction wall shapes has\nbeen studied and compared side-by-side by computational simulation, and the effect of contraction\ncross-sectional shape on the flow uniformity at the contraction exit has been included as well.\nA different contraction wall shape could result in up to an extra 4% pressure drop of a closed-loop\nwind tunnel, and the contraction wall shape has a stronger influence on the pressure loss than the\ncontraction cross-sectional shape. The first and the second derivatives from different wall shape\nequations could provide a hint for qualitatively comparing the flow uniformity at the contraction\nexits. A wind tunnel contraction with an octagonal shape provides not only better fluid mechanics\nperformance than that with a circular or a square cross-sectional shape, but also lower manufacturing\ncosts. Moreover, a smaller blockage ratio within the test section can be achieved by employing an\noctagonal cross-sectional shape instead of a circular cross-sectional shape under the same hydraulic\ndiameter circumstance. A wind tunnel contraction with an octagonal cross-sectional shape is\nrecommended to be a design candidate....
Wire coating process is a continuous extrusion process for primary insulation of conducting\nwires with molten polymers for mechanical strength and protection in aggressive environments.\nNylon, polysulfide, low/high density polyethylene (LDPE/HDPE) and plastic polyvinyl chloride\n(PVC) are the common and important plastic resin used for wire coating. In the current study,\nwire coating is performed using viscoelastic third grade fluid in the presence of applied magnetic\nfield and porous medium. The governing equations are first modeled and then solved analytically by\nutilizing the homotopy analysis method (HAM). The convergence of the series solution is established.\nA numerical technique called ND-solve method is used for comparison and found good agreement.\nThe effect of pertinent parameters on the velocity field and temperature profile is shown with\nthe help of graphs. It is observed that the velocity profiles increase as the value of viscoelastic\nthird grade parameter �² increase and decrease as the magnetic parameter M and permeability\nparameter K increase. It is also observed that the temperature profiles increases as the Brinkman\nnumber Br, permeability parameter K, magnetic parameter M and viscoelastic third grade parameter\n(non-Newtonian parameter) �² increase....
In chemical engineering applications, the operation of condensers and evaporators can be\nmade more efficient by exploiting the transport properties of interfacial waves excited on the interface\nbetween a hot vapor overlying a colder liquid. Linear theory for the onset of instabilities due to heating\na thin layer from above is computed for the Marangoniââ?¬â??BÃ?©nard problem. Symbolic computation\nin the long wave asymptotic limit shows three stationary, non-growing modes. Intersection of two\ndecaying branches occurs at a crossover long wavelength; two other modes co-exist at the crossover\npointââ?¬â?propagating modes on nascent, shorter wavelength branches. The dispersion relation is then\nmapped numerically by Newton continuation methods. A neutral stability method is used to map the\nspace of critical stability for a physically meaningful range of capillary, Prandtl, and Galileo numbers.\nThe existence of a cut-off wavenumber for the long wave instability was verified. It was found that\nthe effect of applying a no-slip lower boundary condition was to render all long waves stationary.\nThis has the implication that any propagating modes, if they exist, must occur at finite wavelengths.\nThe computation of 8000 different parameter sets shows that the group velocity always lies within 12\nto 23\nof the longwave phase velocity....
A bivariate spectral homotopy analysis method (BSHAM) is extended to solutions of systems of nonlinear coupled partial\ndifferential equations (PDEs). The method has been used successfully to solve a nonlinear PDE and is now tested with systems. The\nmethod is based on a new idea of finding solutions that obey a rule of solution expression that is defined in terms of the bivariate\nLagrange interpolation polynomials. The BSHAM is used to solve a system of coupled nonlinear partial differential equations\nmodeling the unsteady mixed convection boundary layer flow, heat, and mass transfer due to a stretching surface in a rotating\nfluid, taking into consideration the effect of buoyancy forces. Convergence of the numerical solutions was monitored using the\nresidual error of the PDEs. The effects of the flow parameters on the local skin-friction coefficient, the Nusselt number, and the\nSherwood number were presented in graphs....
An axial oscillation tool is proved to be effective in solving problems associated with high\nfriction and torque in the sliding drilling of a complex well. The fluidic axial oscillation tool, based on\nan output-fed bistable fluidic oscillator, is a type of axial oscillation tool which has become increasingly\npopular in recent years. The aim of this paper is to analyze the dynamic flow behavior of a fluidic\naxial oscillation tool with the absence of a throttling plate in order to evaluate its overall performance.\nIn particular, the differences between the original design with a throttling plate and the current\ndefault design are profoundly analyzed, and an improvement is expected to be recorded for the latter.\nA commercial computational fluid dynamics code, Fluent, was used to predict the pressure drop\nand oscillation frequency of a fluidic axial oscillation tool. The results of the numerical simulations\nagree well with corresponding experimental results. A sufficient pressure pulse amplitude with a low\npressure drop is desired in this study. Therefore, a relative pulse amplitude of pressure drop and\ndisplacement are introduced in our study. A comparison analysis between the two designs with and\nwithout a throttling plate indicates that when the supply flow rate is relatively low or higher than\na certain value, the fluidic axial oscillation tool with a throttling plate exhibits a better performance;\notherwise, the fluidic axial oscillation tool without a throttling plate seems to be a preferred alternative.\nIn most of the operating circumstances in terms of the supply flow rate and pressure drop, the fluidic\naxial oscillation tool performs better than the original design....
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