Dae-hyun Wei

Linear instability analysis was performed to investigate the origin of the self-sustained oscillations, at St=O(0.1), which have been widely reported in backward-facing step flows. Parametric studies, based on local stability analysis of a family of time-average velocity profiles modeling those observed in recirculating flows, show that the frequency of the absolute mode is determined primarily by the shear layer thickness, and the growth rate of the absolute mode is controlled by the amount of

We use ab initio computations to investigate the effect of filler ions on the properties of ${\text{CoSb}}_{3}$ skutterudites. We analyze global and local structural effects of filling, using the Ba-filled system as an example. We show that the deformation of Sb network induced by the filler affects primarily nearest neighboring Sb sites around the filler site as the soft Sb rings accommodate the distortion. Rearrangement of Sb atoms affects the electronic band structure and we clarify the effec

We present the electron-phonon averaged via Gaussian process regression (EPA-GPR) method, in which the electron-phonon coupling matrix is represented as a function of two energies and is in turn modeled as a Gaussian process. The EPA-GPR method can be used as an efficient method to estimate thermoelectric properties of materials for fast-screening applications, comparable to the original electron-phonon averaged (EPA) method and the electron-phonon averaged via moving-least-squares (EPA-MLS) met

Thermoacoustic instability in premixed combustors occurs occasionally at multiple frequencies, especially in configurations where flames are stabilized on separating shear layers that form downstream of sudden expansions or bluff bodies. While some of these frequencies are related to the acoustic field, others appear to be related to shear flow instability phenomena. It is shown in this paper that shear flows can support self-sustained instabilities if they possess absolutely unstable modes. The

Thermoelectric modules can convert thermal energy into electrical energy or vice versa, and they are becoming increasingly popular in numerous cooling applications. A thermoelectric cooler has no moving parts and may potentially serve as a maintenance-free and noise-free refrigerator with a long life span. According to previous studies, it is important to optimize thermal resistance of the thermoelectric module in a thermoelectric cooling system. Inappropriate thermal matching degrades the perfo

Power generation characteristics of a sandwich-type thermoelectric generator in which the heat source is embedded into thermoelectric elements are investigated. Our previous work on a similar concept only considered a uniform heat source distribution inside thermoelectric elements. In this work, the effect of the spatial distribution of a heat source is examined. In particular, the effect of the concentration of heat source near the one end, that is, the hot end, is intensively studied as a pote