This study aims to determine the characteristics of fluid flow through root canal irrigation using positive and negative pressure methods used CFD (Computational Fluid Dynamic) software by modeling root canals and needle insertion in the root canals. This modeling used a steady flow, an incompressible flow, and uniform flow at the inlet side, and the roughness of the root canal wall surface is neglected (smooth wall). The open-ended needle with different insertion lengths applied for each method with a flow rate of 0.2 mL/s or about 6.63 m/s and the Reynolds number is 1376 (Laminar). The fluid has 2.5% of NaOCl with the density of 1060 kg/m 3 and 0.001 Pa.s of fluid viscosity. After considering factors such as velocity, dynamic pressure, and wall shear stress in both methods, a greater velocity value in the apical region is determined by using a positive pressure method. Meanwhile, the negative pressure method shows the ability to lift higher due to shear stress, which is more evenly distributed upwards. However, both methods are qualified for irrigation replacement in the apical region.
The coal-based steam power plant accounts for the largest electricity generation in Indonesia. Disruption in operation mostly caused by a failure of a component of the system and considered a serious problem and must be prevented. Failure can be originated from operations as well as the design. In the present work, a root cause study was performed on failure elbow in the steam line from the high-pressure heater (HPH) to the deaerator. The failure occurred only after 5 years of operation. The analysis was started with a visual examination, material verification, microstructural investigation, thickness measurement, and computational modelling. The analysis and simulation study showed that the failure of the elbow caused by two-phase flow where steam quality was compromised. The recommendation was to examine the HPH and to find possible leaks of the waterside to the steam side in the HPH system.
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