Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 5 Articles
In this research, a two-way coupling of discrete phase model is developed in order to track\nthe discrete nature of aluminum oxide particles in an obstructed duct with two side-by-side obstacles.\nFinite volume method and trajectory analysis are simultaneously utilized to solve the equations\nfor liquid and solid phases, respectively. The interactions between two phases are fully taken into\naccount in the simulation by considering the Brownian, drag, gravity, and thermophoresis forces.\nThe effects of space ratios between two obstacles and particle diameters on different parameters\ncontaining concentration and deposition of particles and Nusselt number are studied for the constant\nvalues of Reynolds number (Re = 100) and volume fractions of nanoparticles (�¦ = 0.01). The obtained\nresults indicate that the particles with smaller diameter (dp = 30 nm) are not affected by the flow\nstreamline and they diffuse through the streamlines. Moreover, the particle deposition enhances as\nthe value of space ratio increases. A comparison between the experimental and numerical results\nis also provided with the existing literature as a limiting case of the reported problem and found in\ngood agreement...
The identification of the mechanical parameters of the viscoelastic core layer is of great\nsignificance for the modeling and damping design of the constrained layer damping (CLD) composite\nstructure. In this study, based on the measured frequency vibration response of a CLD plate, an inverse\napproach was developed to identify the aforementioned parameters. Then, on the basis of considering\nboth the viscoelastic material damping and the remaining equivalent viscous damping, the equation\nof motion of the CLD plate under base excitation was established and a method to obtain the vibration\nresponse was also presented. Further, a matching calculation based on sensitivity was proposed, to\nachieve the identification of the mechanical parameters. Finally, a CLD aluminum plate with a ZN_1\nviscoelastic core layer was chosen to demonstrate the proposed method. In addition, the identification\nresults were also introduced into the vibration response analysis and the rationality of the identified\nparameters were verified by comparing the vibration responses obtained by theoretical calculations\nand the experiment....
A novel method for designing a seven-bar linkage based on the optimization of centrodes is presented in this paper. The proposed\nmethod is applied to the design of a pure-rolling cutting mechanism, wherein close interrelation between the contacting lines\nand centrodes of two pure-rolling bodies is formulated and the genetic optimization algorithm is adopted for the dimensional\nsynthesis of the mechanism. The optimization is conducted to minimize the error between mechanism centrodes and the expected\ntrajectories, subject to the design requirements of the opening distance, the maximum amount of overlap error, and peak value of\nshearing force. An optimal solution is obtained and the analysis results show that the horizontal slipping and standard deviation\nof the lowest moving points of the upper shear blade have been reduced by 78.0% and 80.1% and the peak value of shear stress\ndecreases by 29%, which indicate better cutting performance and long service life....
This study analyzes the modeling and dynamics of a novel passive multi-degree-of-freedom\n(MDOF) vibration isolation platform which can achieve a significant isolation effect. Symmetrical\nscissor-like structures (SLSs) are utilized in the proposed MDOF isolation platform as the supporting\nand isolation elastic components. Based on the mathematical modeling and theoretical analysis of the\nMDOF vibration isolation system with SLSs, the effects of structural parameters and joint friction on\nthe stiffness and damping properties are investigated. It is shown that due to geometric relations\nwithin the SLSs, the natural frequencies can be reduced via adjusting structural parameters of the\nSLS for different direction vibration isolation. Theoretical and experimental results show that the\nSLS isolation platform can achieve much better loading capacity and vibration isolation performance\nsimultaneously by only using linear passive components because of the MDOF adjustable stiffness\nproperty. Therefore, with low cost and energy consumption, the proposed novel isolation platform\ncan improve the vibration suppression in various engineering practices....
In this paper, laminar forced convection of CuO nanofluid is numerically investigated\nin sudden expansion microchannel with isotherm walls and different\nexpansion ratios (ER). An Eulerian two-fluid model is considered to simulate\nthe nanofluid flow inside the microchannel and the governing mass,\nmomentum and energy equations for both phases are solved using the finite\nvolume method. Eulerian-Eulerian two-phase model is very efficient because\nof considering the relative velocity and temperature of the phases and the nanoparticle\nconcentration distribution. In solving the flow equations for both\nphases, the SIMPLE algorithm is modified for the coupling of the velocity and\npressure and the continuity equations for both phases are combined in order\nto create the pressure correction equations. However, the Eulerian-Eulerian\nmodeling results show higher heat transfer enhancement in comparison to\npure water, so that for a 2% copper-water nanofluid, it has been observed a\n35% increase of the heat transfer. The heat transfer enhancement increases\nwith increase in Reynolds number and nanoparticle volume concentration,\nwhile the pressure drop increases only slightly. An investigation of the expansion\nratio of microchannel shows that the average Nusselt number increases\nwith decrease in expansion ratio as well as with increase in Reynolds number.\nAlso, the Bifurcation has been occurred in higher Reynolds number that is\ndifferent for each expansion ratio of the microchannel....
Loading....