This paper concerns with the basic investigations on the wet chemical etching of semiconductors. First, a method to observe the etched cross-section of aluminum layer is developed. It is applied to the observation for the cross-section of a test piece etched in a quiescent etchant. The observation successfully makes clear the time variation for the geometry of the etched cross-section, and elucidates the effects of the resist width on the geometry. Secondly, the numerical simulation for the etching process is performed. The simulated geometry of the etched cross-section is confirmed to agree with the observed result, indicating that the present numerical simulation is effectively used to predict the geometry of the etched cross-section.

Poly-silicon deposition rate profiles on silicon wafers in several temperatures around 873 K along axial direction in commercial low-pressure chemical vapor deposition (LPCVD) reactor were investigated by both experiments and numerical simulations considering coupled computational fluid dynamics (CFD) and chemical reactions. While the chemical reaction processes of poly-silicon film deposition is a complicated system with a huge number of elementary reactions, we could successfully simulate the experimental results with a simplified 2-step surface reaction model of SiH4. Simulated film deposition rate profiles along the axial direction of reactor were in good agreement with experimental results, and the 2-step reaction model was proved to be a good tool for the numerical simulation of poly-silicon deposition process in commercial reactor.

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In the aspect of water-environments, the studies on wind waves are very important regarding transport phenomena in atmosphere, lakes and sea. Dispersion phenomena in water under wind waves have been studied by many researchers, but they have taken notice of only surface layer beneath the free surface. The purpose of this study is to elucidate the diffusion in the surface layer and the lower layer as well. Visualization of dye diffusion and velocity field measurements by means of PIV and 2D-electro magnetic velocity meters were performed. The mechanisms of dye diffusion between the surface and the lower layers are different. In the surface layer, the diffusion can be estimated well by using Taylor's turbulent diffusion theory. In the lower layer, however, we found that the diffusion is like the chaotic mixing. To investigate qualitative feature of the chaotic mixing under wind waves, a mathematical model represented by the superposition of a periodic array of vortices and stationary water waves was proposed. The coexistence of free surface waves and large-scale vortices causes chaotic advection of fluid particles. This phenomenon will induce strong mixing of water in the lower layer even if the turbulent intensity in this layer is small.

This paper describes prediction of aeroacoustics from a rotating machinery fan using compressible Large Eddy Simulation (LES). The fan is installed semi-opened space located between the fan cover and the body of rotating machinery such as a electric motor. The fan distributes air from the fan cover intake onto the cooling fins. The Reynolds number of the rotating fan is 9 × 105; its Mach number is approximately 0.1. Under the low Mach number regime, hybrid computational aeroacoustics (hybrid CAA) method, which is solved turbulent flow and acoustics separately, is generally used. However, we used a direct CAA method because interaction between pressure fluctuation from the turbulence and sound propagation should be considered. For the direct CAA method approach, compressible Navier–Stokes equations are solved. Density is calculated from the ideal gas law. To compute turbulence phenomena, LES is used as the turbulence model. The Dynamic Smagorinsky Model is used for the subgrid scale. The sound propagation speed is approximately 10 times faster than the flow speed. Therefore, the numerical schemes, time step, and computational grids size were evaluated with line sound source in the two-dimensional domain as a fundamental study to determine the numerical schemes. Subsequently we evaluated the sound pressure level with the electric motor fan, which is an experimental structure. Through verification of the direct CAA model, we obtained the following results. (1) The predicted pressure fluctuation spectra show good agreement with the experimentally obtained spectra. Specifically, the blade passing frequency (BPF) and trend of the pressure fluctuation decay in the inertial turbulence subrange were predicted. (2) The predicted sound pressure spectra also show good agreement with BPF. Specifically, the acoustic mode and broadband turbulence noise level were predicted.