Mud flows are common phenomena in mountainous areas,which can threaten human safety and cause property losses under certain extreme circumstances.Studying the dynamic characteristics of mud flows,especially in the ver...Mud flows are common phenomena in mountainous areas,which can threaten human safety and cause property losses under certain extreme circumstances.Studying the dynamic characteristics of mud flows,especially in the vertical direction,is helpful for risk reduction and hazard mitigation.In this study,a 2D depth-resolved numerical model based on Herschel-Bulkley rheology was developed to study the vertical structures of unsteady mud flows with a free-surface.The numerical model was solved by the projection method,and the free surface of mud flows was captured through the VOF method.To fully validate this new model,a series of laboratory experiments involving dam break mud flows were conducted,and the mud flow heights,bottom pressures and envelopes of mud residuum were measured.The numerical model proposed in this study was first validated by the steady-state solution for uniform flows of Herschel-Bulkley fluid on an inclined plane.Additionally,the simulated and measured mud flow heights,bottom pressures at different x locations and envelopes with different bed slopes showed good agreement.Furthermore,the numerical results for a Herschel-Bulkley fluid dam break flow were used to validate the proposed model,which further revealed good agreements.After that,the scenarios in which mud flows impact on a structure were numerically studied,and the vertical profiles of the front velocity and impact pressure on the structure were analyzed and discussed.The results show that a plug layer was formed in the mud flow under unsteady and nonuniform flow conditions,and the impact pressure on the structure was dominated by the dynamic pressure.In addition,the vertical position with the maximum impact pressure acting on the structure was not at the bottom or the surface of the mud flows,and the normalized vertical position rose as the yield stress and consistency coefficient increase for Herschel-Bulkley fluids.展开更多
Water-rich clay to sand suspensions show a shear rate dependent flow behavior and knowledge of the appropriate rheological model is relevant for sedimentological, industrial and hydraulic studies. We present experimen...Water-rich clay to sand suspensions show a shear rate dependent flow behavior and knowledge of the appropriate rheological model is relevant for sedimentological, industrial and hydraulic studies. We present experimental rheological measurements of water-rich(40 to 60 wt%) clay to silt(population A) and silt to sand(population B) suspensions mixed in different proportions. The data evidence a shear rate dependent shear thinning-shear thickening transition. At lower shear rates, the suspensions organize in chains of particles, whereas at higher shear rates, these chains disrupt so increasing the viscosity. The viscosity, consistency and yield stress decrease as the A+B fraction decreases as the content of B particles increases. This behavior reflects the competing effects of the lubrication and frictional processes as a function of particle size and water content. Transitional flows form by the incorporation of small amounts of the finer fraction while ‘oceanic floods’ form at the estuary of rivers and the submarine debris-flows increase their velocity by incorporating water. The critical Reynolds number of the studied suspensions is ～2000±100 suggesting that the grainsize plays a major role in the laminar to turbulent transition. Our results have implications for the modeling of sediment flows and the hazard related to floods.展开更多
According to a lot of hydrological and environmental monitoring data, the condition of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is described. The occurrence and devel...According to a lot of hydrological and environmental monitoring data, the condition of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is described. The occurrence and development of soil and water loss is analyzed. The conclusion is that: (1) generally, the situation of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is light, however, soil and water loss in some regions is serious, especially in the middle reach area of the river; (2) soil and water loss in the Lancang River Mekong River (in Yunnan section, China) watershed presents developing tendency and it is mainly caused by human beings. In accordance with these results, the control measures for soil and water loss are discussed.展开更多
The simplified flow of drilling process in the soil hardening or oil rig site was experimentally investigated. Two flow models were used. One is the concentric cylinders with helical protrusion at the inner cylinder. ...The simplified flow of drilling process in the soil hardening or oil rig site was experimentally investigated. Two flow models were used. One is the concentric cylinders with helical protrusion at the inner cylinder. The other is the concentric plain wall cylinders with axial flow. The radius ratio and aspect ratio of both models are the same with 0. 65 and 48,respectively. The mud is the typical fluid seen in the soil hardening processes. We used the water and the mud for the working fluid. We used the optical PIV for the water flow measurement and echo PIV for the mud flow. In case of the water study,the dominant vortical structures appeared in both the protrusion and plain model with axial flow.In case of mud flow,the vortices shown in the water model disappeared and the push and pull-up motion by the protrusion is dominant. We believe this information can be useful to understand the flow physics of drilling process in the complex fluid flow.展开更多
Storm rainfall and severe storm rainfall can directly cause flood, and usually cause a series of secondary disasters. In mountain areas, the abrupt mud rock flow and landslide disasters motivated by storm rainfall are...Storm rainfall and severe storm rainfall can directly cause flood, and usually cause a series of secondary disasters. In mountain areas, the abrupt mud rock flow and landslide disasters motivated by storm rainfall are especially serious. So, it is negligible content to pay more attention and strengthen the study of storm rainfall secondary disasters in studying storm rainfall disaster.In the National Key Project 85-906-09,we have developed these aspects’studies, which not be ignored by some relevant sections展开更多
The continuous evaluation of the measured Stand Pipe Pressure(SPP)against a modeled SPP value in real-time involves the automatic detection of undesirable drilling events such as drill string washouts and mud pump fai...The continuous evaluation of the measured Stand Pipe Pressure(SPP)against a modeled SPP value in real-time involves the automatic detection of undesirable drilling events such as drill string washouts and mud pump failures.Numerous theoretical and experimental studies have been established to calculate the friction pressure losses using different rheological models and based on an extension of pipe flow correlations to an annular geometry.However,it would not be feasible to employ these models for real-time applications since they are limited to some conditions and intervals of application and require input parameters that might not be available in real-time on each rig.In this study,The Group Method of Data Handling(GMDH)is applied to develop a trustworthy model that can predict the SPP in real-time as a function of mud flow,well depth,RPM and the Fan VG viscometer reading at 600 and 300 rpm.In order to accomplish the modeling task,3351 data points were collected from two wells from Algerian fields.Graphical and statistical assessment criteria disclosed that the model predictions are in excellent agreement with the experimental data with a coefficient of determination of 0.9666 and an average percent relative error less than 2.401%.Furthermore,another dataset(1594 data points)from well-3 was employed to validate the developed correlation for SPP.The obtained results confirmed that the proposed GMDH-SPP model can be applied in real-time to estimate the SPP with high accuracy.Besides,it was found that the proposed GMDH correlation follows the physically expected trends with respect to the employed input parameters.Lastly,the findings of this study can help for the early detection of downhole problems such as drill string washout,pump failure,and bit balling.展开更多
基金Fundings from National Natural Science Foundation of China(Grant No.41941017 and U20A20112)Sichuan Science and Technology Program(Grant No.2021YFH0009)are gratefully acknowledged。
文摘Mud flows are common phenomena in mountainous areas,which can threaten human safety and cause property losses under certain extreme circumstances.Studying the dynamic characteristics of mud flows,especially in the vertical direction,is helpful for risk reduction and hazard mitigation.In this study,a 2D depth-resolved numerical model based on Herschel-Bulkley rheology was developed to study the vertical structures of unsteady mud flows with a free-surface.The numerical model was solved by the projection method,and the free surface of mud flows was captured through the VOF method.To fully validate this new model,a series of laboratory experiments involving dam break mud flows were conducted,and the mud flow heights,bottom pressures and envelopes of mud residuum were measured.The numerical model proposed in this study was first validated by the steady-state solution for uniform flows of Herschel-Bulkley fluid on an inclined plane.Additionally,the simulated and measured mud flow heights,bottom pressures at different x locations and envelopes with different bed slopes showed good agreement.Furthermore,the numerical results for a Herschel-Bulkley fluid dam break flow were used to validate the proposed model,which further revealed good agreements.After that,the scenarios in which mud flows impact on a structure were numerically studied,and the vertical profiles of the front velocity and impact pressure on the structure were analyzed and discussed.The results show that a plug layer was formed in the mud flow under unsteady and nonuniform flow conditions,and the impact pressure on the structure was dominated by the dynamic pressure.In addition,the vertical position with the maximum impact pressure acting on the structure was not at the bottom or the surface of the mud flows,and the normalized vertical position rose as the yield stress and consistency coefficient increase for Herschel-Bulkley fluids.
文摘Water-rich clay to sand suspensions show a shear rate dependent flow behavior and knowledge of the appropriate rheological model is relevant for sedimentological, industrial and hydraulic studies. We present experimental rheological measurements of water-rich(40 to 60 wt%) clay to silt(population A) and silt to sand(population B) suspensions mixed in different proportions. The data evidence a shear rate dependent shear thinning-shear thickening transition. At lower shear rates, the suspensions organize in chains of particles, whereas at higher shear rates, these chains disrupt so increasing the viscosity. The viscosity, consistency and yield stress decrease as the A+B fraction decreases as the content of B particles increases. This behavior reflects the competing effects of the lubrication and frictional processes as a function of particle size and water content. Transitional flows form by the incorporation of small amounts of the finer fraction while ‘oceanic floods’ form at the estuary of rivers and the submarine debris-flows increase their velocity by incorporating water. The critical Reynolds number of the studied suspensions is ～2000±100 suggesting that the grainsize plays a major role in the laminar to turbulent transition. Our results have implications for the modeling of sediment flows and the hazard related to floods.
文摘According to a lot of hydrological and environmental monitoring data, the condition of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is described. The occurrence and development of soil and water loss is analyzed. The conclusion is that: (1) generally, the situation of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is light, however, soil and water loss in some regions is serious, especially in the middle reach area of the river; (2) soil and water loss in the Lancang River Mekong River (in Yunnan section, China) watershed presents developing tendency and it is mainly caused by human beings. In accordance with these results, the control measures for soil and water loss are discussed.
基金supported by Basic Science Research Program (2013-008918)through the National Research Foundation (NRF)the Gyeongsang National University Fund for Professors on Sabbatical Leave,2015
文摘The simplified flow of drilling process in the soil hardening or oil rig site was experimentally investigated. Two flow models were used. One is the concentric cylinders with helical protrusion at the inner cylinder. The other is the concentric plain wall cylinders with axial flow. The radius ratio and aspect ratio of both models are the same with 0. 65 and 48,respectively. The mud is the typical fluid seen in the soil hardening processes. We used the water and the mud for the working fluid. We used the optical PIV for the water flow measurement and echo PIV for the mud flow. In case of the water study,the dominant vortical structures appeared in both the protrusion and plain model with axial flow.In case of mud flow,the vortices shown in the water model disappeared and the push and pull-up motion by the protrusion is dominant. We believe this information can be useful to understand the flow physics of drilling process in the complex fluid flow.
文摘Storm rainfall and severe storm rainfall can directly cause flood, and usually cause a series of secondary disasters. In mountain areas, the abrupt mud rock flow and landslide disasters motivated by storm rainfall are especially serious. So, it is negligible content to pay more attention and strengthen the study of storm rainfall secondary disasters in studying storm rainfall disaster.In the National Key Project 85-906-09,we have developed these aspects’studies, which not be ignored by some relevant sections
基金The authors would like to acknowledge the Petroleum Equipment’s Reliability and Materials Laboratory of the University of Boumerdes for their assistance throughout this study。
文摘The continuous evaluation of the measured Stand Pipe Pressure(SPP)against a modeled SPP value in real-time involves the automatic detection of undesirable drilling events such as drill string washouts and mud pump failures.Numerous theoretical and experimental studies have been established to calculate the friction pressure losses using different rheological models and based on an extension of pipe flow correlations to an annular geometry.However,it would not be feasible to employ these models for real-time applications since they are limited to some conditions and intervals of application and require input parameters that might not be available in real-time on each rig.In this study,The Group Method of Data Handling(GMDH)is applied to develop a trustworthy model that can predict the SPP in real-time as a function of mud flow,well depth,RPM and the Fan VG viscometer reading at 600 and 300 rpm.In order to accomplish the modeling task,3351 data points were collected from two wells from Algerian fields.Graphical and statistical assessment criteria disclosed that the model predictions are in excellent agreement with the experimental data with a coefficient of determination of 0.9666 and an average percent relative error less than 2.401%.Furthermore,another dataset(1594 data points)from well-3 was employed to validate the developed correlation for SPP.The obtained results confirmed that the proposed GMDH-SPP model can be applied in real-time to estimate the SPP with high accuracy.Besides,it was found that the proposed GMDH correlation follows the physically expected trends with respect to the employed input parameters.Lastly,the findings of this study can help for the early detection of downhole problems such as drill string washout,pump failure,and bit balling.
