In a PEMFC gas channel with a trapezoidal cross-section, the effect of air and water inlet velocities on water removal characteristics is numerically studied via the volume of fluid(VOF) method. When the channel wall contact angle is 60 degrees, the air inlet velocities higher than 2.5 m/s are advantageous to obtain lower GDL surface water coverage ratio(WCR). The WCR increases as the wall contact angle increases to 90 or 120 degrees due to the relatively lower surface tension force. In overall, WCR decreases as the air inlet velocity increases and WCR increases as the water inlet velocity increases.

In the paper an efficient numerical algorithm to predict the flow phenomena around the water-jet propulsion system was described. The potential-based flow analysis method was adopted to predict the velocity and the pressure on the inlet duct of the water-jet propulsion system. The method employed normal dipoles and source distributed on the solid surface such as the inlet duct and the tracked vehicle. The inlet duct and outlet open boundary surfaces were introduced where the sources and dipoles were distributed to define a closed boundary surface. The developed numerical algorithm was applied to a tracked vehicle propelled by the water-jet propulsion system with the different IVR(inlet velocity ratio). The results by the numerical analysis were compared with the experimental data in order to verify the feasibility of the proposed numerical algorithm.

The objective of this study is to determine the appropriate size of the inlet pipe diameter and thereby conduct hydraulic analysis for the Korean water distribution network. To this end, the data tables for equivalent pipe diameters and outflow rates presently employed in Korea were adopted. By incorporating the table of equivalent pipe diameters, it was found that the size of the inlet pipe diameter was overestimated, which can cause shortage of water pressure and malfunctioning or insufficiency of outflow rate in the corresponding adjacent region. However, by conducting hydraulic analysis based on the table of outflow rates, relatively reasonable flow rates were observed. Furthermore, by comparing the real demand-driven analysis (RDDA) approach and demand-driven analysis (DDA) approach toward managing the huge water demand, it was observed that DDA could not effectively respond to real hourly usage conditions, whereas RDDA (which reflects the hourly effects of inlet pipe diameter and storage tanks) demonstrated results similar to that of real water supply.

본 연구에서는 도로의 측구 부분을 수리모형으로 제작하여 빗물받이의 차집능력을 검토하였다. 측구의 유량은 도로의 차선(2-4차선) 및 빗물받이 간격(10-30m)을 고려하여 4-15l/sec의 유량을 사용하였고, 도로의 종방향 경사는 0, 2, 5, 7%를 선택하였으며, 측구의 횡경사는 4, 7, 10%를 사용하였다. 유입부의 규모는 의 4종류를 사용하였으며, 총 실험 횟수는 240회이다. 측구의 횡경사가 클수록 전체적인 빗물받이의 차집유량은 증가하였다.