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Purpose: A numerical analysis is carried out to study the effect of pin fin geometry on the performance of microchannel heat sinks. Design/methodology/approach: A three-dimensional numerical analysis is carried out using the conjugate heat transfer module of COMSOL MULTIPHYSICS software. Initially, the study is carried out for a microchannel heat sink with elliptical pin fins of 500 µm fin height, and the results of the same are validated with the results obtained from the literature. Further, the effect of different pin fin shapes and pin fin heights is investigated in terms of Nusselt number and pressure drop. The analysis is carried out with different pin fin shapes viz. ellipse, circle, square and hexagon. The pin fin height for all channels is varied from 300 µm to 700 µm. The total surface area of the channel coming into contact with coolant is kept constant for different coolant inflow velocities. Findings: Higher values of Nusselt numbers are obtained for fin pins at larger height and high coolant inlet velocities. At coolant inlet velocity of 1 m/s, as pin fin height increases from 300 µm to 700 µm, the channel with circular pin fins shows a maximum increment of 66 % and elliptical pin fins shows a minimum increment of 40 % in terms of Nusselt number. A maximum value of Nusselt number observed is 21.36 with square pin fins of 700 µm fin height and a minimum of 6.03 Nusselt number with circular fins of 300 µm fin height. OriginalityOriginality/Value: This study is useful in appropriate selection of pin fin geometry for enhancing the performance of microchannel heat sink. [ABSTRACT FROM AUTHOR]

In this paper, passive planar micromixers based on circular and square mixing chambers spaced at equidistant along the length of micromixer are proposed to operate in the laminar flow regime for high mixing index. Numerical simulations are conducted to evaluate the performance of proposed micromixers by solving the Navier-Stokes equation and convection-diffusion equation. A COMSOL Multiphysics 5.0 is used for computational fluid dynamics. Numerical simulation of mixing of fluids in a micromixer with circular and square chambers in a laminar flow regime has been carried out. Four performance parameters namely, mixing index, pressure drop, pumping power, and performance index are used to evaluate different design configurations of micromixers. Analysis of mixing index based on the standard deviation of the mass fraction is carried with different constriction channel width such as 200, 250, and 300 µm for a range of Reynolds number from 0.1 to 75. The both micromixers show over 95% mixing at the exit for the range 15-75 of Reynolds number at constriction width of 200 µm. Especially, about 99% mixing is achieved at Reynolds number less than one i.e. at 0.1. The effect of Reynolds number on the pressure drop is also investigated. Thus, the proposed micromixers can be used in microfluidic systems which require fast mixing at Re less than 1 and greater than 15. [ABSTRACT FROM AUTHOR]

A multi-objective optimization approach is used to determine the optimal surface texturing parameters to improve performance of journal bearing. The numerical attempts are made using Taguchi's orthogonal array L 27 . Initially, static performance analysis is carried out for plain bearing system using thin film analysis by COMSOL Multiphysics and the results are validated with the literature. In the later part, analysis of load carrying capacity and frictional torque is carried out for different parameters of surface texturing. The bearing performance is studied for various groove parameters viz.groove location, groove height, groove width, number of grooves and spacing between grooves. Grey relational analysis is used to find an optimal set of parameters which gives maximum load carrying capacity and minimum frictional torque. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to develop an analytical approach to evaluate the influence of material uncertainties on cross-sectional stiffness properties of thin walled composite beams. Design/methodology/approach – Fuzzy arithmetic operators are used to modify the thin-walled beam formulation, which was based on a mixed force and displacement method, and to obtain the uncertainty properties of the beam. The resulting model includes material uncertainties along with the effects of elastic couplings, shell wall thickness, torsion warping and constrained warping. The membership functions of material properties are introduced to model the uncertainties of material properties of composites and are determined based on the stochastic behaviors obtained from experimental studies. Findings – It is observed from the numerical studies that the fuzzy membership function approach results in reliable representation of uncertainty quantification of thin walled composite beams. The propagation of uncertainties is also demonstrated in the estimation of structural responses of composite beams. Originality/value – This work demonstrates the use of fuzzy approach to incorporate uncertainties in the responses analytically, in turn improving computational efficiency drastically as compared to the Monte-Carlo method. [ABSTRACT FROM AUTHOR]

A structural health monitoring (SHM) methodology is developed for composite rotor blades. An aeroelastic analysis of composite rotor blades based on the finite element method in space and time and with implanted matrix cracking and debonding/delamination damage is used to obtain measurable system parameters such as blade response, loads and strains. A rotor blade with a two-cell airfoil section and family of laminates is used for numerical simulations. The model based measurements are contaminated with noise to simulate real data. Genetic fuzzy systems (GFS) are developed for global online damage detection using displacement and force-based measurement deviations between damaged and undamaged conditions and for local online damage detection using strains. It is observed that the success rate of the GFS depends on number of measurements, type of measurements and training and testing noise level. The GFS work quite well with noisy data and is recommended for online SHM of composite helicopter rotor blades. [Copyright &y& Elsevier]

A numerical analysis is carried out in this study to understand the effect of the different pin fin layouts in the microchannel heat sinks. The performance analysis is done using the conjugate heat transfer module of COMSOL Multiphysics software. Initially, a microchannel with elliptical pin fins of 500‐μm fin height in it is validated with the results from the literature. Further, the performance of microchannels with three different pin fin layouts is compared with the baseline model. The investigation is done for different coolant inflow velocities, keeping the channel and pin fin dimensions constant, and the results are presented in terms of the Nusselt number and pressure drop. The highest value of 19.287 Nusselt number is obtained for case b with a maximum inlet velocity of 1 m/s. A maximum increment of 16.8% and a minimum increment of 11.1% in the Nusselt number is observed in case d and case a, respectively, with 0.2 m/s inlet velocity. The minimum value of the pressure drop is observed in case d. From the results obtained in this study, it is concluded that a staggered pin fin orientation in the microchannel enhances the thermal performance better than inline arrangement. [ABSTRACT FROM AUTHOR]