A large number of submarine landslides with different scales have been identified in the canyon area of the submarine pipeline route of Liwan 3-1 gas field. There is still much chance that submarine slope failures wou...A large number of submarine landslides with different scales have been identified in the canyon area of the submarine pipeline route of Liwan 3-1 gas field. There is still much chance that submarine slope failures would happen, and the following mass movement would present great risk to the submarine pipeline. In view of this, a numerical prediction method based on Eulerian-Eulerian two-phase flow model is introduced to simulate the mass movement of potential submarine landslides. The sliding soil and ambient water are respectively simulated by Herschel-Bulkley rheology model and Newtonian fluid model. The turbulence is simulated using the k-e model. Compared with both the experiment data and Bing result, the two-phase flow model shows a good accuracy, and its result is more close to the actual situation; the dynamic coupling between soil and ambient water can be effectively simulated and the phenomena of hydroplaning and head detachment can be obtained. Finally, the soil movement of a potential submarine landslide is simulated as an example, according to the seismic profile in the canyon area. The result shows that the hydroplaning occurs during the movement process. The runout distance calculated by the two-phase flow model is 877 m, which is 27.1% larger than the Bing result. However, the peak front velocity of soil is relative small, with a maximum value of 8.32 m/s. The Bing program with a simple and rapid process can be used for a preliminary evaluation, while the two-phase flow model is more appropriate for an accurate assessment.展开更多
Hydroplaning speed can be affected by pavement texture depth,thickness of water film,tire pressure and tread depth.In this study,to understand the influence of pavement texture on the hydroplaning speed,a new lab-scal...Hydroplaning speed can be affected by pavement texture depth,thickness of water film,tire pressure and tread depth.In this study,to understand the influence of pavement texture on the hydroplaning speed,a new lab-scale apparatus has been designed and manufactured.The lack of proportion between linear movement of vehicle shaft and the wheel rotation was found to be a good index to determine hydroplaning threshold.A 5%drop in the ratio of wheel-to-axle rotation has been assumed as an index to determine hydroplaning threshold.Based on the measures,a simplified model was developed that is able to predict the hydroplaning speed depending on pavement's texture characteristics.The results indicated that a 77%increase in mean texture depth cause 9%increase in hydroplaning threshold speed.展开更多
To investigate the influence of wet conditions on vehicle braking behavior,a numerical-analytical method was proposed for the simulation of tire hydroplaning and frictional energy dissipation. First, a finite element ...To investigate the influence of wet conditions on vehicle braking behavior,a numerical-analytical method was proposed for the simulation of tire hydroplaning and frictional energy dissipation. First, a finite element model of tire hydroplaning was established using the coupled EulerianLagrangian method,including a pneumatic tire model and a textured asphalt pavement model. Then,the frictional force on the tire-pavement interface at different speeds was calculated by the model. Based on vehicle braking mechanism and frictional energy dissipation,a calculation method for braking distance was proposed based on a three-stage braking process. The proposed method was verified by comparing the calculated hydroplaning speed and braking distance with field test results.Then,vehicle braking distances and wet friction coefficients were calculated under different conditions. The results show that thinner water film,a more complex tread pattern and higher tire inflation pressure all contribute to the vehicle braking performance; moreover, the pavement texture has obvious influence on vehicle braking behavior,especially at a high speed. The proposed method shows great effectiveness in predicting vehicle braking behavior on wet asphalt pavements.展开更多
The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon ...The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon called hydroplaning.Although a lot of numerical investigations into hydroplaning have been conducted,only a few have considered the impact of the runway permeability.Hence,computational problems,such as excessive distortion and computing efficiency decay,may arise with such numerical models when dealing with the thin water film.This paper presents a numerical model comprising of the tire,water film,and the interaction with the runway,applying a mathematical model using the smoothed particle hydrodynamics and finite element(SPH-FE)algorithm.The material properties and geometric features of the tire model were included in the model framework and water film thicknesses from 0.75 mm to 7.5 mm were used in the numerical simulation.Furthermore,this work investigated the impacts of both surface texture and the runway permeability.The interaction between tire rubber and the rough runway was analyzed in terms of frictional force between the two bodies.The SPH-FE model was validated with an empirical equation proposed by the National Aeronautics and Space Administration(NASA).Then the computational efficiency of the model was compared with the traditional coupled Eulerian-Lagrangian(CEL)algorithm.Based on the SPH-FE model,four types of the runway(Flat,SMA-13,AC-13,and OGFC-13)were discussed.The simulation of the asphalt runway shows that the SMA-13,AC-13,and OGFC-13 do not present a hydroplaning risk when the runway permeability coefficient exceeds 6%.展开更多
This paper investigates the effect of initial volume fraction on the runout characteristics of collapse of granular columns on slopes in fluid. 2-D sub-grain scale numerical simulations are performed to understand the...This paper investigates the effect of initial volume fraction on the runout characteristics of collapse of granular columns on slopes in fluid. 2-D sub-grain scale numerical simulations are performed to understand the flow dynamics of granular collapse in fluid. The discrete element method（DEM） technique is coupled with the lattice Boltzmann method（LBM）, for fluid-grain interactions, to understand the evolution of submerged granular flows. The fluid phase is simulated using multiple-relaxation-time LBM（LBM-MRT） for numerical stability. In order to simulate interconnected pore space in 2-D, a reduction in the radius of the grains（hydrodynamic radius） is assumed during LBM computations. The collapse of granular column in fluid is compared with the dry cases to understand the effect of fluid on the runout behaviour. A parametric analysis is performed to assess the influence of the granular characteristics（initial packing） on the evolution of flow and run-out distances for slope angles of 0 °, 2.5°, 5 ° and 7.5 °. The granular flow dynamics is investigated by analysing the effect of hydroplaning, water entrainment and viscous drag on the granular mass. The mechanism of energy dissipation, shape of the flow front, water entrainment and evolution of packing density is used to explain the difference in the flow characteristics of loose and dense granular column collapse in fluid.展开更多
Inspired by the idea that bionic non-smooth surfaces(BNSS)can reduce water flow resistance,the application of BNSS resistance reduction method in grooves surface of antiskid tire tread pattern has been investigated fo...Inspired by the idea that bionic non-smooth surfaces(BNSS)can reduce water flow resistance,the application of BNSS resistance reduction method in grooves surface of antiskid tire tread pattern has been investigated for increasing hydroplaning velocity of tire by using computational fluid dynamics(CFD)simulation.Three kinds of BNSS(riblet,convex dome,and dimple concave)are arranged in tire tread grooves to study the water flow resistance effects in grooves with non-smooth characteristics.A tire-water coupled model is established and CFD technique is applied to simulating hydroplaning.The simulation results show that BNSS grooves can reduce water flow resistance and increase mean flow rate by disturbing the eddy movement in boundary layers.The drag forces of riblet and dimple surface are lower and drainage capacity is higher than those of smooth surface under the same void space on tread pattern,but it is not in dome.BNSS is a good way to promote antiskid performance without increasing additional groove space;extra tire-road noise production is therefore avoided due to groove space enlargement.展开更多
基金The National Natural Science Foundation of China under contract No.41206058the National Science and Technology Major Project of China under contract No.2011ZX05056-001-02the Scientific Research Fund of the First Institute of Oceanography,State Oceanic Administration under contract No.GY0213G25
文摘A large number of submarine landslides with different scales have been identified in the canyon area of the submarine pipeline route of Liwan 3-1 gas field. There is still much chance that submarine slope failures would happen, and the following mass movement would present great risk to the submarine pipeline. In view of this, a numerical prediction method based on Eulerian-Eulerian two-phase flow model is introduced to simulate the mass movement of potential submarine landslides. The sliding soil and ambient water are respectively simulated by Herschel-Bulkley rheology model and Newtonian fluid model. The turbulence is simulated using the k-e model. Compared with both the experiment data and Bing result, the two-phase flow model shows a good accuracy, and its result is more close to the actual situation; the dynamic coupling between soil and ambient water can be effectively simulated and the phenomena of hydroplaning and head detachment can be obtained. Finally, the soil movement of a potential submarine landslide is simulated as an example, according to the seismic profile in the canyon area. The result shows that the hydroplaning occurs during the movement process. The runout distance calculated by the two-phase flow model is 877 m, which is 27.1% larger than the Bing result. However, the peak front velocity of soil is relative small, with a maximum value of 8.32 m/s. The Bing program with a simple and rapid process can be used for a preliminary evaluation, while the two-phase flow model is more appropriate for an accurate assessment.
文摘Hydroplaning speed can be affected by pavement texture depth,thickness of water film,tire pressure and tread depth.In this study,to understand the influence of pavement texture on the hydroplaning speed,a new lab-scale apparatus has been designed and manufactured.The lack of proportion between linear movement of vehicle shaft and the wheel rotation was found to be a good index to determine hydroplaning threshold.A 5%drop in the ratio of wheel-to-axle rotation has been assumed as an index to determine hydroplaning threshold.Based on the measures,a simplified model was developed that is able to predict the hydroplaning speed depending on pavement's texture characteristics.The results indicated that a 77%increase in mean texture depth cause 9%increase in hydroplaning threshold speed.
基金The National Natural Science Foundation of China(No.51378121,51778139)
文摘To investigate the influence of wet conditions on vehicle braking behavior,a numerical-analytical method was proposed for the simulation of tire hydroplaning and frictional energy dissipation. First, a finite element model of tire hydroplaning was established using the coupled EulerianLagrangian method,including a pneumatic tire model and a textured asphalt pavement model. Then,the frictional force on the tire-pavement interface at different speeds was calculated by the model. Based on vehicle braking mechanism and frictional energy dissipation,a calculation method for braking distance was proposed based on a three-stage braking process. The proposed method was verified by comparing the calculated hydroplaning speed and braking distance with field test results.Then,vehicle braking distances and wet friction coefficients were calculated under different conditions. The results show that thinner water film,a more complex tread pattern and higher tire inflation pressure all contribute to the vehicle braking performance; moreover, the pavement texture has obvious influence on vehicle braking behavior,especially at a high speed. The proposed method shows great effectiveness in predicting vehicle braking behavior on wet asphalt pavements.
基金The work described in this paper is supported by the National Natural Science Foundation of China(Grant Nos.52278455 and 52311530685)the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(21SG24)+1 种基金the International Cooperation Project of Science and Technology Commission of Shanghai Municipality(No.22210710700)the Fundamental Research Funds for the Central Universities.
文摘The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon called hydroplaning.Although a lot of numerical investigations into hydroplaning have been conducted,only a few have considered the impact of the runway permeability.Hence,computational problems,such as excessive distortion and computing efficiency decay,may arise with such numerical models when dealing with the thin water film.This paper presents a numerical model comprising of the tire,water film,and the interaction with the runway,applying a mathematical model using the smoothed particle hydrodynamics and finite element(SPH-FE)algorithm.The material properties and geometric features of the tire model were included in the model framework and water film thicknesses from 0.75 mm to 7.5 mm were used in the numerical simulation.Furthermore,this work investigated the impacts of both surface texture and the runway permeability.The interaction between tire rubber and the rough runway was analyzed in terms of frictional force between the two bodies.The SPH-FE model was validated with an empirical equation proposed by the National Aeronautics and Space Administration(NASA).Then the computational efficiency of the model was compared with the traditional coupled Eulerian-Lagrangian(CEL)algorithm.Based on the SPH-FE model,four types of the runway(Flat,SMA-13,AC-13,and OGFC-13)were discussed.The simulation of the asphalt runway shows that the SMA-13,AC-13,and OGFC-13 do not present a hydroplaning risk when the runway permeability coefficient exceeds 6%.
基金the Cambridge Commonwealth, Overseas Trust and the ShellCambridge-Brazil collaboration for the financial support to pursue this research
文摘This paper investigates the effect of initial volume fraction on the runout characteristics of collapse of granular columns on slopes in fluid. 2-D sub-grain scale numerical simulations are performed to understand the flow dynamics of granular collapse in fluid. The discrete element method（DEM） technique is coupled with the lattice Boltzmann method（LBM）, for fluid-grain interactions, to understand the evolution of submerged granular flows. The fluid phase is simulated using multiple-relaxation-time LBM（LBM-MRT） for numerical stability. In order to simulate interconnected pore space in 2-D, a reduction in the radius of the grains（hydrodynamic radius） is assumed during LBM computations. The collapse of granular column in fluid is compared with the dry cases to understand the effect of fluid on the runout behaviour. A parametric analysis is performed to assess the influence of the granular characteristics（initial packing） on the evolution of flow and run-out distances for slope angles of 0 °, 2.5°, 5 ° and 7.5 °. The granular flow dynamics is investigated by analysing the effect of hydroplaning, water entrainment and viscous drag on the granular mass. The mechanism of energy dissipation, shape of the flow front, water entrainment and evolution of packing density is used to explain the difference in the flow characteristics of loose and dense granular column collapse in fluid.
基金Colleges and Universities in Jiangsu Province Pans to Graduate Research and Innovation,China(No.CXLX13_676)Jiangsu Province Six Talents Peak Project,China(No.2011A031)
文摘Inspired by the idea that bionic non-smooth surfaces(BNSS)can reduce water flow resistance,the application of BNSS resistance reduction method in grooves surface of antiskid tire tread pattern has been investigated for increasing hydroplaning velocity of tire by using computational fluid dynamics(CFD)simulation.Three kinds of BNSS(riblet,convex dome,and dimple concave)are arranged in tire tread grooves to study the water flow resistance effects in grooves with non-smooth characteristics.A tire-water coupled model is established and CFD technique is applied to simulating hydroplaning.The simulation results show that BNSS grooves can reduce water flow resistance and increase mean flow rate by disturbing the eddy movement in boundary layers.The drag forces of riblet and dimple surface are lower and drainage capacity is higher than those of smooth surface under the same void space on tread pattern,but it is not in dome.BNSS is a good way to promote antiskid performance without increasing additional groove space;extra tire-road noise production is therefore avoided due to groove space enlargement.
