Monotone scheme and boundary conditions for finite volume simulation of magnetohydrodynamic internal flows at high Hartmann number

A monotone scheme for finite volume simulation of magnetohydrodynamic internal flows at high Hartmann number is presented. The numerical stability is analysed with respect to the electromagnetic force. Standard central finite differences applied to finite volumes can only be numerically stable if the vector products involved in this force are computed with a scheme using a fully staggered grid. The electromagnetic quantities (electric currents and electric potential) must be shifted by half the grid size from the mechanical ones (velocity and pressure). An integral treatment of the boundary layers is used in conjunction with boundary conditions for electrically conducting walls. The simulations are performed with inhomogeneous electrical conductivities of the walls and reach high Hartmann numbers in three-dimensional simulations, even though a non-adaptive grid is used.

Low Reynolds number turbulence models for accurate thermal simulations of electronic components

The electronics industry and the problems associated with the cooling of microelectronic equipment are developing rapidly. Thermal engineers now find it necessary to consider the complex area of equipment cooling at some level. This continually growing industry also faces heightened pressure from consumers to provide electronic product miniaturization, which in itself increases the demand for accurate thermal management predictions to assure product reliability. Computational fluid dynamics (CFD) is considered a powerful and almost essential tool for the design, development and optimization of engineering applications. CFD is now widely used within the electronics packaging design community to thermally characterize the performance of both the electronic component and system environment. This paper discusses CFD results for a large variety of investigated turbulence models. Comparison against experimental data illustrates the predictive accuracy of currently used models and highlights the growing demand for greater mathematical modelling accuracy with regards to thermal characterization. Also a newly formulated low Reynolds number (i.e. transitional) turbulence model is proposed with emphasis on hybrid techniques.

On Reynolds number and scaling effects in microchannel flows

This paper presents a numerical study of the Reynolds number and scaling effects in microchannel flows. The configuration includes a rectangular, high-aspect ratio microchannel with heat sinks, similar to an experimental setup. Water at ambient temperature is used as a coolant fluid and the source of heating is introduced via electronic cartridges in the solids. Two channel heights, measuring 0.3 mm and 1 mm are considered at first. The Reynolds number varies in a range of 500-2200, based on the hydraulic diameter. Simulations are focused on the Reynolds number and channel height effects on the Nusselt number. It is found that the Reynolds number has noticeable influences on the local Nusselt number distributions, which are in agreement with other studies. The numerical predictions of the dimensionless temperature of the fluid agree fairly well with experimental measurements; however the dimensionless temperature of the solid does exhibit a significant discrepancy near the channel exit, similar to those reported by other researchers. The present study demonstrates that there is a significant scaling effect at small channel height, typically 0.3 mm, in agreement with experimental observations. This scaling effect has been confirmed by three additional simulations being carried out at channel heights of 0.24 mm, 0.14 mm and 0.1 mm, respectively. A correlation between the channel height and the normalized Nusselt number is thus proposed, which agrees well with results presented.

To fit in or stand out? The interaction between mortality salience, dissent and self esteem on social projection

Social projection (SP) refers to our tendency to assume that others think the same as we do, but the effect can also be used to detect the extent to which participants want to see themselves as similar to others. Simon et al (1997) found that participants informed that they were deviant increased their SP but those told that they were conformist reduced theirs. This compensatory function supports Brewer’s optimal distinctiveness which states that a balance must be struck between competing desires to feel similar and unique. In line with terror management theory, the effect was particularly apparent under conditions of mortality salience (MS). So far SP has only been examined on measures that target personal identity so this experiment developed a measure to target social identity as well. Participants were provided with either minority or majority dissent feedback, in MS or control conditions, and their SP on items relevant to personal and social identity were recorded. Results showed that group feedback only impacted upon participants SP on social identity measures and interacted with MS and self-esteem; those with high self-esteem had higher SP scores following minority dissent under conditions of mortality salience, indicating an attempt to assert their individuality. On SP measures targeting personal identity, MS and self-esteem interacted; the death prime increased SP scores for those with low self-esteem but decreased it for those with high self-esteem. Findings are interpreted in terms of TMT and optimal distinctiveness theory and their applications.