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Abstrak :
The fluid flow pattern in a thermoacoustic resonator is an important characteristic that affects the performance of the thermoacoustic refrigerator. The main factor that affects the flow and subsequently the heat transfer processes between the oscillating fluid and the stack walls is the geometry of the stack unit, especially related to the stack thickness and stack separation. In this paper, a two-dimensional numerical simulation of the inviscid fluid flow around the stack unit in a quarter wavelength resonator is carried out by using the continuity, Navier-Stokes, energy and ideal gas equations. These equations are solved using the perturbation method and the finite difference method. Three cases of different stack plate thickness are investigated: negligible, 0.4 mm and 0.8 mm thicknesses, respectively. The stack separation has also been varied for the 0.4 mm thickness, within and beyond that recommended by previous studies. Results show that vortices and streaming are always present, more significantly with the thicker plates. Concentrated vortices in the thick plate case stay longer than those with the thinner plate. They contribute to the high heat transfer rate as shown by the temperature profiles.

Abstrak :
Persamaan BPS memudahkan untuk melakukan pemecahan numerik suatu sistem dengan topological defects. Salah satu cara untuk mendapatkan persamaan BPS adalah dengan menggunakan First-Order Formalism. Untuk mendapatkan persamaan BPS dan potensial yang dapat menghasilkan persamaan BPS tersebut dari sistem dengan Alice strings, digunakan formalisme tersebut. Kemudian, hasil dari formalisme tersebut diaplikasikan untuk model-model tertentu yang memvariasikan model utama (yang mempunyai medan gauge SU (2) dan U (1) dan satu medan skalar) dengan hanya menggunakan satu medan gauge SU (2) atau menambahkan medan skalar doublet. ...... The BPS equations are very useful when used for solving fields in a system with topological defects. A more systematic method of finding the equations is by using the First-Order Formalism. This First-Order Formalism is used for models containing Alice strings to obtain their BPS equations potentials required for those equations to exist. The models used are a model containing both SU (2) and U (1) gauge fields, a model with only one U (1) gauge field and a model containing both SU (2) and U (1) gauge fields with an additional doublet scalar field.