Search results

A comparison of the accuracy of the central discretization scheme with artificial dissipation and the upwind flux‐difference TVD scheme has been made for the compressible Navier‐Stokes equations for high Reynolds number flows. First, a comparison is made on two one‐dimensional model problems. Then the schemes are compared on flat plate boundary layer flow. It is shown that a central scheme basically has poor accuracy due to the isotropic nature of the artificial dissipation. An upwind scheme decomposes the flow into different components and adapts the dissipation to the velocity of the components. The associated ansitropic dissipation results in a good accuracy. It is further discussed how a central discretization scheme with artificial dissipation can be improved at the expense of the same complexity of an upwind scheme.

This study aims to discuss the effect of carbon nanotubes (CNTs) on the mechanical properties of acrylonitrile–butadiene–styrene (ABS) composites fabricated by additive manufacturing (AM). Insight into the energy-dissipation mechanisms introduced and/or enhanced by the addition of CNTs is presented in this study.

ABS/CNT filaments were fabricated with different concentrations of CNTs. Using a fused deposition modeling approach, unidirectional specimens were printed using a MakerBot Replicator 2X (MakerBot Industries, Brooklyn, NY, USA). Specimens were tested under static and dynamic conditions, with the loading coinciding with the printing direction, to determine elastic modulus, strength and viscoelastic properties.

A CNT reinforcing effect is evident in a 37 per cent increase in elastic modulus. Likewise, the strength of the composite increases by up to 30 per cent with an increase in weight fraction of CNTs. At low dynamic strain amplitudes (0.05 per cent), a correlation between dissipated strain energy of the butadiene phase and strength of the composite is found such that less dissipation, from constraint of the butadiene particles by the CNTs, leads to higher strength of the composite. At higher dynamic strains, the presence of a high concentration of CNT leads to increased energy dissipation, with a maximum measured value of 24 per cent higher loss factor compared to baseline specimens. Because the trend of the composite behavior is similar (with a higher absolute value) to that of neat ABS, this study’s results indicate that well-established polymer/CNT dissipation mechanisms (such as stick-slip) are not significant, but that the CNTs amplify the dissipation of the ABS matrix by formation of crazes through stress concentrations.

This study provides knowledge of the dissipation behavior in additively manufactured ABS/CNT composites and provides insight into the expansion to new printable materials for dynamics applications.

Aiming at the characteristics of large stiffness, low ductility, and poor energy dissipation capacity of cross-laminated timber (CLT) shear wall, a method of opening vertical joints and adding low-yield dampers in CLT shear wall is proposed to improve its energy dissipation capacity and ductility.

The finite element model of CLT shear walls with low-yield dampers and dampers assembly was established by ABAQUS. The structural shape of low-yield dampers that meet the requirements of vertical joints in CLT shear walls is studied by numerical analysis. The influence of the number and position of low-yield dampers on the energy dissipation of the shear wall system is studied.

The results show that the low-yield damper with diamond openings should be used in the CLT shear wall, and the energy dissipation effect is the best when the CLT shear wall is uniformly covered with low-yield dampers. After the uniform arrangement of four groups of low-yield steel dampers, the energy consumption of the CLT shear wall increases by 75.38%, and the ductility increases by 13.22%.

There are few studies on replacing connectors between shear walls with low-yield steel dampers, and rectangular soft steel dampers are prone to stress concentration and poor deformation capacity. Therefore, this paper establishes the model of perforated low-yield damper and CLT and makes numerical analysis to determine the opening form, geometric parameters of low-yield damper, and the optimal layout scheme in CLT shear wall.

Isotropic artificial dissipation is added to the Navier‐Stokes equations along with a correction term which cancels the artificial dissipation term in the limit when the mesh size is zero. For a finite mesh size, the correction term replaces the artificial viscosity terms with hyperviscosity terms, i.e., with an artificial dissipation which depends on the fourth derivatives of the velocity. Hyperviscosity more effectively suppresses the higher wave number modes and has a smaller effect on the inertial modes of the flow field than does artificial viscosity. This scheme is implemented using the finite element method and therefore the required amount of dissipation is determined by analysing the discretization on a finite element. The scheme is used to simulate the flow in a driven cavity and over a backward facing step and the results are compared to existing results for these cases.

The paper aims to build a finite element simulation model for pilling of polyester hairiness on the fabric to study the effects of hairiness performance on pilling and reveal pilling mechanisms.

The finite element simulation model of pilling of polyester hairiness was established by ABAQUS. Polyester hairiness was treated as elastic thin rod, which was divided by two-node linear three-dimensional truss element. The effects of hairiness elastic modulus, hairiness friction coefficient and hairiness diameter on frictional dissipation energy, strain energy and kinetic energy produced by pilling have been studied. The analysis solution values were compared with the finite element simulation results, which was used to verify finite element simulation.

The paper provides new insights about how to reveal pilling mechanisms of polyester hairiness with different performance. Comparing finite element simulation results with analysis solutions shows that the fitness is greater than 0.96, which verifies finite element simulation. Larger hairiness elastic modulus gives rise to higher friction dissipation energy and strain energy of hairiness but lower kinetic energy. Increasing friction coefficient enhances friction dissipation and strain energy of hairiness. However, kinetic energy decreases with the increase of friction coefficient. Hairiness diameter also has an important effect on hairiness entanglement and pilling. Increasing hairiness diameter can decrease friction dissipation energy but enhance strain energy and kinetic energy.

Finite element simulation was verified by analysis solutions. The solutions include friction dissipation energy, strain energy and kinetic energy, which cannot measured b experiment. Therefore, researchers are encouraged to simulate pilling to obtain pilling grades, which be compared with experiment results.

Pilling of polyester hairiness was simulated by ABAQUS. This method makes pilling process visualization, and pilling mechanisms was revealed from non-linear dynamics.

The purpose of this paper is to analyze the thermal shock response on the deformation of circular hollow cylinder in a thermodynamically consistent manner.

The investigation is carried out under the light of generalized thermoelasticity theory with energy dissipation. In order to obtain the analytical expressions of the components of stress and strain fields, appropriate integral transform technique is adopted and the salient features are emphasized.

It has been observed that the existence of energy dissipation can minimize the development of the stress components into the cylindrical wall. Since more amount of heat is propagate into the medium in a short period of time consequently, the medium deformed in a high rate in presence of energy dissipation. Two special phenomena are also revealed in the particular cases.

The numerical simulated results are demonstrated through a numerous diagrams and some important observations are explained. This work may be helpful for those researchers who are devoted on several types of heat or fluid flow into the pipeline made with anisotropic solids.

Delay and power dissipation are the two major design constraints in very large scale integration (VLSI) circuits. These arise due to millions of active devices and interconnections connecting this gigantic number of devices on the chip. Important technique of repeater insertion in long interconnections to reduce delay in VLSI circuits has been reported during the last two decades. This paper deals with delay, power dissipation and the role of voltage‐scaling in repeaters loaded long interconnects in VLSI circuits for low power environment.

Trade off between delay and power dissipation in repeaters inserted long interconnects has been reviewed here with a bibliographic survey. SPICE simulations have been used to validate the findings.

Optimum number of uniform sized CMOS repeaters inserted in long interconnects, lead to delay minimization. Voltage‐scaling is highly effective in reduction of power dissipation in repeaters loaded long interconnects. The new finding given here is that optimum number of repeaters required for delay minimization decreases with voltage‐scaling. This leads to area and further power saving.

The bibliographic survey needs to be revised in future, taking the various other aspects of VLSI interconnects viz. noise, cross talk extra into account.

The paper is of high significance in VLSI design and low‐power high‐speed applications. It is also valuable for new researchers in this emerging field.

The unsteady natural convection flow of a viscous dissipative fluid along a semi‐infinite vertical plate subjected to periodic surface temperature oscillation is investigated.

An electrical‐network model based on the Network Simulation Method is developed to solve the governing equations. The accuracy and effectiveness of the method are demonstrated.

The increasing of the viscous dissipation and the decreasing in the Prandtl number lead to a decrease in Nusselt number and an increase in the local skin‐friction. Also, it is found that the oscillations of the Nusselt number and of the local skin‐friction depend on the frequency and amplitude of the oscillating surface temperature. For Pr = 1,000 and ε = 0.005 (realistic case) the effect of the viscous dissipation is appreciable at large distances from the leading edge.

The inclusion of viscous dissipation in the energy equation, except of the theoretical interest, has applications in very special cases, for example, gases at very low temperature and also for high Prandtl number liquids.

The influence of the non‐uniformity of wall temperature on the heat transfer by natural convection along of the plate together with the viscous dissipation of the fluid are analysed by means of a new numerical technique based on the electrical analogy.

This paper aims to obtain the optimal wire sizing of buffered global interconnects and to investigate the impact of weight factor on the optimized system performance for various technology nodes.

The width and spacing of interconnects are optimized under two scenarios, and corresponding optimum line width is determined by minimizing the value of power‐delay product which is defined as a figure of merit (FOM). Based on the results, the impact of weight factor on the optimized system performance, such as delay and power dissipation per unit length, is analyzed for various technology nodes.

The analytical expressions of the optimum width are derived under two scenarios. Better FOMs can be achieved for the S=W scenario, but the wireability of the chip degrades considerably. The optimized delay increases with the increasing of weight factor, while the optimized power dissipation decreases with it. For a given weight factor, smaller latency and less power dissipation can be achieved for the S=W case.

The analytical expressions of the optimum width of interconnects are given, and a comprehensive study of the impact of weight factor on the optimized results under two scenarios is presented.

The purpose of this paper is to apply the boundary element method (BEM) to Stokes flow between eccentric rotating cylinders, considering the case when viscous dissipation plays a significant role and determining the Nusselt number as a function of cylinder geometry parameters.

The problem is described by the equation of motion of Stokes flow and an energy equation with a viscous dissipation term. First, the velocity field and the viscous dissipation term were determined from the momentum equation. The determined dissipation of energy and the constant temperature on the cylinder walls are the conditions for the energy equation, from which the temperature distribution and the heat flux at the boundary of the cylinders are determined. Numerical calculations were performed using the author’s own computer program based on BEM. Verification of the model was carried out by comparing the temperature determined by the BEM with the known theoretical solution for the temperature distribution between two rotating concentric cylinders.

As the ratio of the inner cylinder diameter to the outer cylinder diameter (r1/r2) increases, the Nusselt number increases. The angle of inclination of the function of the Nusselt number versus r1/r2 increases as the distance between the centers of the inner and outer cylinders increases.

The computational results may be used for the design of slide bearings and viscometers for viscosity testing of liquids with high viscosity where viscous dissipation is important. In the work, new integral kernels were determined for BEM needed to determine the viscous dissipation component.