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The sustainability risk of Ho Chi Minh City, Vietnam, due to saltwater intrusion
Minh Thien Ngo,Jae Min Lee,Hyun A Lee,우남칠 한국지질과학협의회 2015 Geosciences Journal Vol.19 No.3
Groundwater is important for domestic, industrial, and agricultural uses in Ho Chi Minh City, Vietnam. As the city has developed in a coastal environment, the issue of the fresh water supply must be solved for continuous development. The aim of this study was to quantitatively estimate the risk of groundwater salinization in the Ho Chi Minh area due to saline water intrusion into the main coastal aquifer (the Upper Pliocene aquifer) based on field monitoring data, and to evaluate the sustainability of the city with respect to groundwater resources. From the national monitoring database, water level data were obtained for the last 10 years (2000 to 2009), and a total of 33 hydrogeochemical and isotope data sets were obtained from the aquifer. The sustainability of Ho Chi Minh City with respect to the groundwater supply was quantitatively evaluated at an aquifer scale using groundwater sustainability indicators (GWSIs) suggested by the UNESCO/IAEA/IAH Working Group. The results indicated that groundwater in the southern region, part of the western region, and the area along the Saigon riverside was of poor quality, with very high total dissolved solids (>1,000 mg/L) and high concentrations of Cl and Fe, exceeding the World Health Organization’s drinking water guidelines. The Br:Cl ratios and the δ2H and δ18O values of the samples indicated that the salinization of groundwater resulted mainly from mixing with seawater over a long period. During 2004–2009, the saline boundary moved inland, with the farthest distance reaching ~3.2 km. The long-term abstraction of groundwater, which has been much greater than its recharge capability, is probably causing the decline in water level (in 39% of the aquifer area), the degradation of groundwater quality (in 62% of the area), and the continuously expanding saline water intrusion (by 7.4% in 5 years). Thus, for the sustainable development of Ho Chi Minh City, in addition to passive measures to regulate over-pumping and pollution controls, active measures should be considered to prevent further seawater intrusion and to increase groundwater recharge through artificial recharge or better management of aquifer recharge (MAR).
Tu Thien Ngo,Hoang Minh Khoa Nguyen,Dong-Wook Oh 대한설비공학회 2020 대한설비공학회 학술발표대회논문집 Vol.2020 No.6
The main objective in the present study is to investigate the additive behavior inside a mixture of carbon fibers and polydimethylsiloxane (PDMS) flowing in an orifice channel. The numerical simulation is carried out by ANSYS FLUENT software. The track of extensional rate and shear rate of fibers along the additive path in the channel is studied. Experiment and numerical simulation results are in good agreement. The ratio between extensional rate and absolute of shear rate represents as the angular orientation in the flow direction was performed and developed in this study.
Tu Thien Ngo,Hoang Minh Khoa Nguyen,Dong-Wook Oh 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.11
This study aimed to perform the additive behavior inside a mixture of carbon fibers and polydimethylsiloxane (PDMS) flowing in a channel. Numerical simulation was done by ANSYS FLUENT software. The non-Newtonian fluid model was applied in this study to simulate the rheology inside the mixture flow. The viscosity reduces as the shear rate increases due to the shear-thinning non-Newtonian characteristic. The shear rate distribution of non-Newtonian and Newtonian fluid within the injection molding were analyzed. The ratio of extensional rate and shear rate were studied to predict the additive orientation during the injection molding of polymer composites.
Nguyen Minh Phu,Vo Tuyen,Tu Thien Ngo 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7
The paper presents the effect of the Reynolds number, relative roughness height and relative roughness pitch on the heat transfer and pressure loss in a solar air heater. A novel absorber plate with metal shavings from the turning of a steel shaft is employed to reduce the cost of production and to be available for the manufacturing industry. The parameters studied ranged from 5000 to 25000 for the Reynolds number, from 4.7 to 9.4 for the relative roughness pitch (P/e) and from 0.26 to 0.43 for the relative roughness height (e/D h ). The results show that there are some characteristics that differ from the published studies. The optimum e/D h is 0.35 to obtain the highest thermo-hydraulic performance parameter, and the parameter increases with a decrease in P/e. Within the scope of the study, the maximum thermo-hydraulic performance parameter is approximately 1.5. The correlations between the Nusselt number and the friction factor are developed based on the experimental data. The results from the correlations and from the experimental data are fairly in agreement.
Computational fluid dynamics analysis for basement ventilation in case of a fire
웬반합,Trinh Thi Minh Nguyen,Phu Minh Nguyen,Tu Thien Ngo 한국마린엔지니어링학회 2020 한국마린엔지니어링학회지 Vol.44 No.4
The basement parking lot, which provides a certain number of car spaces for users, is an effective solution for parking in crowded cities. The required ventilation system design is generally based on the number of air changes per hour, provided by local authority standards. An appropriately designed ventilation system plays an important role in ensuring a safe environment for people in case of a fire. This study aims to establish the smoke spread behavior and tenability criteria for a car fire in a basement parking lot with a small area of 2,700 m2, by using Autodesk computational fluid dynamics 2019 software. The car-fire growth rate was assumed to be a low t-squared curve. For numerical analysis, a steady-state fire was adopted at the sixth minute of the curve. The completely developed heat release rate of the car fire was 4 MW. Two common ventilation systems–a ductwork system and a combined impulse and ductwork system–were used for the simulation. The ventilation system was designed to extract 10 air changes per hour. The results suggested that the two ventilation systems guarantee a safe route for evacuation through the ramp. Besides, the ductwork ventilation system performs better at preventing the smoke from spreading, as compared to the combined ventilation system, during 6 min after ignition.