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Optical Materials
Published in Christoph Gerhard, Optics Manufacturing, 2018
After plaining, the fourth and last essential step of glass manufacturing, cooling, is performed. Generally, the cooling procedure of a melt directly impacts the nature of the resulting solid. During the cooling of crystalline solids (for example, metals), a well-defined crystallization temperature Tc is found as shown in Figure 3.7. This temperature indicates the beginning of crystallization and thus the transition from the liquid to the solid state. In contrast, glasses feature not a crystallization temperature but rather a certain temperature range where the transition from the liquid to the plastic state occurs during the cooling of the glass melt.3 Glasses can thus be referred to as supercooled liquids. The transition from the liquid to the plastic state is described or quantified by the glass transition temperature Tg (glass transition point). This characteristic temperature is determined by the linear extrapolation of the cooling curve as shown in Figure 3.7.
Polymers
Published in Andrea Chen, Randy Hsiao-Yu Lo, Semiconductor Packaging, 2016
Andrea Chen, Randy Hsiao-Yu Lo
The glass transition temperature (Tg) represents the softening point of an adhesive. To measure that transition point, a differential scanning calorimetry (DSC) test system shows the peak exothermic reaction temperature for a given polymer system. Further information on DSC is given in Section 6.2 and in Appendix B.
Reynolds Stress Turbulence Modelling with γ Transition Model
Published in International Journal of Computational Fluid Dynamics, 2022
Naina Pisharoti, John Webster, Stefano Brizzolara
The freestream conditions for T3-series flat plates given in Table 1 were taken from the ERCOFTAC experimental flat plate cases (Savill 1993). The table suggests that all the T3-series flat plates experience fairly high freestream turbulence intensities which leads to bypass transition. The transition point moves downstream as the turbulence intensity decreases. Figure 4(b–d) shows a good agreement of the current model with experimental data. For the T3A (Figure 4(b)) and T3B (Figure 4(c)) cases, the turbulent region values are approximated by SSG/LRR-ω-γ more accurately compared to other transition models. The point of transition, that is the point where the slope of the skin-friction coefficient begins to increase, is predicted well for T3A and T3A- (Figure 4(d)) compared to the other two transition models which tend to predict it upstream of the actual point.
SPH Viscous Flow Around a Circular Cylinder: Impact of Viscous Formulation and Background Pressure
Published in International Journal of Computational Fluid Dynamics, 2021
Majority of the studies focuses on two and three-dimensional flows around a circular cylinder due to being geometrically simple, yet involving regions such as the boundary layer, shear layers and the wake that are prone to instability. Instability characteristics of the flow field has been reported to be in a close relationship with Reynolds number. An increase in Reynolds number is observed to result in amplified three-dimensional disturbances creating streamwise and spanwise vortices within the near wake, which causes far wake to experience transition from laminar to a turbulent state, as convected downstream. Further increase in Reynolds number is noticed to speed up the transition and move the transition point towards the cylinder (Cardell 1993).
Heat transfer and temperature effects on a dimpled NACA0012 airfoil with various angles of attack
Published in International Journal of Ambient Energy, 2018
P. Booma Devi, V. Paulson, V. Madhanraj, Dilip A. Shah
This graph denotes the relation between the drag coefficient and the angle of attack. The lift coefficient peaked and the drag coefficient also increased when the stall increased. The experimental drag coefficient data are lower than the predicted data. This overprediction of drag was expected. Meanwhile, actual airfoil has laminar flow over the forward half. In the turbulence models, it cannot calculate the transition point from laminar to turbulent, and the boundary layer is turbulent over its length. The viscous boundary layer has less energy than the turbulent boundary layer (Figure 4).