In the hydraulic transporting process of cutter-suction mining natural gas hydrate, when the temperature-pressure equilibrium of gas hydrate is broken, gas hydrates dissociate into gas. As a result, solid-liquid two-p...In the hydraulic transporting process of cutter-suction mining natural gas hydrate, when the temperature-pressure equilibrium of gas hydrate is broken, gas hydrates dissociate into gas. As a result, solid-liquid two-phase flow(hydrate and water) transforms into gas-solid-liquid three-phase flow(methane, hydrate and water) inside the pipeline. The Euler model and CFD-PBM model were used to simulate gas-solid-liquid three-phase flow. Numerical simulation results show that the gas and solid phase gradually accumulate to the center of the pipe. Flow velocity decreases from center to boundary of the pipe along the radial direction. Comparison of numerical simulation results of two models reveals that the flow state simulated by CFD-PBM model is more uniform than that simulated by Euler model, and the main behavior of the bubble is small bubbles coalescence to large one. Comparison of numerical simulation and experimental investigation shows that the values of flow velocity and gas fraction in CFD-PBM model agree with experimental data better than those in Euler model. The proposed PBM model provides a more accurate and effective way to estimate three-phase flow state of transporting gas hydrate within the submarine pipeline.展开更多
Catfish （Pangasianodon hypophthalmus） farming along Mekong river and Bassac river depends heavily on water quality of the two rivers, whereas water quality of these rivers are affected by the waste of aquaculture ac...Catfish （Pangasianodon hypophthalmus） farming along Mekong river and Bassac river depends heavily on water quality of the two rivers, whereas water quality of these rivers are affected by the waste of aquaculture activities, agricultural production, industrial and municipal waste. This report analyzes the monitoring data on Mekong river, Bassac river and adjacent waterways in the period of 2011-2012, focusing on parameters of organic pollution to assess the current quality of these two rivers. Based on the results, the water quality in the river-head was generally better than in the middle and at the end of the river, and the quality of water of the Mekong river was better than Bassac river. In terms of time, water quality in July was considered the best in all the basins. At adjacent natural rivers and canals, ammonia levels increased and exceeded the Vietnamese standard in April, and BOD values were also much higher compared to two major rivers. The results of the model also showed that the levels of pollution index of the Mekong and Bassac river were very low （1.33 and 1.47）, and the values （Y） in the canals were higher （1.63-1.67） but still in permitted level. Therefore, the water quality of the Mekong and Bassac river in the period 2011-2012 was generally still quite good.展开更多
Large-sczde structure of river flow is the main driving force for bed erosion-deposition and bank delbrmation. The structure shapes and retains a corresponding hydraulic geometry form. Therefore, the most stable flow ...Large-sczde structure of river flow is the main driving force for bed erosion-deposition and bank delbrmation. The structure shapes and retains a corresponding hydraulic geometry form. Therefore, the most stable flow structure is the probable natural river plane formation. Natural coordinate transformation and perturbation methods were adapted to deform the governing equations of sine-generated river basic flow and disturbance flow independently. The stability and retention of perturbation waves were analyzed in our model to explain why meandering rivers followed a certain type of tqow path. Computation results showed that all types of perturbation waves in meandering rivers were most stable when the meandering wave number was about 0.39-0.41. We believe that this type of stable flow structure shaped a certain meandering river. The statistical average length-width ratios of Yalin, Habib and da Silva and Leopold and Wolman somewhat confirmed our most stable river mean- dering wave number. In some ways, meandering rivers always tend to diminish internal turbulence intensity.展开更多
基金Project(51375498) supported by the National Natural Science Foundation of China
文摘In the hydraulic transporting process of cutter-suction mining natural gas hydrate, when the temperature-pressure equilibrium of gas hydrate is broken, gas hydrates dissociate into gas. As a result, solid-liquid two-phase flow(hydrate and water) transforms into gas-solid-liquid three-phase flow(methane, hydrate and water) inside the pipeline. The Euler model and CFD-PBM model were used to simulate gas-solid-liquid three-phase flow. Numerical simulation results show that the gas and solid phase gradually accumulate to the center of the pipe. Flow velocity decreases from center to boundary of the pipe along the radial direction. Comparison of numerical simulation results of two models reveals that the flow state simulated by CFD-PBM model is more uniform than that simulated by Euler model, and the main behavior of the bubble is small bubbles coalescence to large one. Comparison of numerical simulation and experimental investigation shows that the values of flow velocity and gas fraction in CFD-PBM model agree with experimental data better than those in Euler model. The proposed PBM model provides a more accurate and effective way to estimate three-phase flow state of transporting gas hydrate within the submarine pipeline.
文摘Catfish （Pangasianodon hypophthalmus） farming along Mekong river and Bassac river depends heavily on water quality of the two rivers, whereas water quality of these rivers are affected by the waste of aquaculture activities, agricultural production, industrial and municipal waste. This report analyzes the monitoring data on Mekong river, Bassac river and adjacent waterways in the period of 2011-2012, focusing on parameters of organic pollution to assess the current quality of these two rivers. Based on the results, the water quality in the river-head was generally better than in the middle and at the end of the river, and the quality of water of the Mekong river was better than Bassac river. In terms of time, water quality in July was considered the best in all the basins. At adjacent natural rivers and canals, ammonia levels increased and exceeded the Vietnamese standard in April, and BOD values were also much higher compared to two major rivers. The results of the model also showed that the levels of pollution index of the Mekong and Bassac river were very low （1.33 and 1.47）, and the values （Y） in the canals were higher （1.63-1.67） but still in permitted level. Therefore, the water quality of the Mekong and Bassac river in the period 2011-2012 was generally still quite good.
基金supported by the National Natural Science Foundation of China(Grant Nos.51279124,50979066,51009105)the Natural Science Foundation of Tianjin(Grant No.12JCQNJC05600)
文摘Large-sczde structure of river flow is the main driving force for bed erosion-deposition and bank delbrmation. The structure shapes and retains a corresponding hydraulic geometry form. Therefore, the most stable flow structure is the probable natural river plane formation. Natural coordinate transformation and perturbation methods were adapted to deform the governing equations of sine-generated river basic flow and disturbance flow independently. The stability and retention of perturbation waves were analyzed in our model to explain why meandering rivers followed a certain type of tqow path. Computation results showed that all types of perturbation waves in meandering rivers were most stable when the meandering wave number was about 0.39-0.41. We believe that this type of stable flow structure shaped a certain meandering river. The statistical average length-width ratios of Yalin, Habib and da Silva and Leopold and Wolman somewhat confirmed our most stable river mean- dering wave number. In some ways, meandering rivers always tend to diminish internal turbulence intensity.
