The current research of tire aerodynamics mainly focus on the isolated and simplified tread tire.Compared with the real complex pattern tire,the tread pattern structure and deformed profile of a loaded tire has a grea...The current research of tire aerodynamics mainly focus on the isolated and simplified tread tire.Compared with the real complex pattern tire,the tread pattern structure and deformed profile of a loaded tire has a greatly influence on tire aerodynamic drag.However,the mechanisms of the isolated loaded tires with different tread patterns effects on the aerodynamic drag are subjects worthy of discussion.The purpose of this study is to experimentally and compu-tationally investigate the aerodynamic characteristics of three tires 185/65 R14 with different patterns under loaded.A wind tunnel test model was first established using three-dimensional(3D)printing with a ratio of 1:1,and the pres-sure coefficients C_(p) of the three tires with different patterns are measured.The paper then conducted computational fluid dynamics(CFD)simulations for analyzing the pressure and flow characteristics.The accuracy of CFD simulation is verified by comparing the simulation results with the test results of pressure coefficients C_(p),and they are of good consistency.While,the general analysis of pressure coefficients C_(p) results of the three tires indicates high-pressure area on the windward surface,and occurrence of low-pressure area on the leeward surface,the pressure coefficients C_(p) of all three tires decreased firstly and then increased along in the air flow direction.The authors finally analyzed the effect of tread patterns on the flow field around the tire and revealed the differences between flow characteristics and aerodynamic drag.The results show that,angle of tire lateral groove has great effect on the flow field characteristics such that;the more the angle of lateral groove agrees with the air flow direction,the less the flow separation and flow vortices,and a minimum observable aerodynamic drag.The research provides a guidance for the design of low aerodynamic drag tires,and helps to illustrate the impact of tire aerodynamics on the car body in the future.展开更多
When a horizontal well is drilled through the natural gas hydrate(NGH)strata with different abundance,the NGH-bearing solid debris tends to lead to the deposit and adhesion of solid particles in the lateral sections a...When a horizontal well is drilled through the natural gas hydrate(NGH)strata with different abundance,the NGH-bearing solid debris tends to lead to the deposit and adhesion of solid particles in the lateral sections and consequently cuttings carrying is not smooth.In this paper,the critical return rate model of drilling fluid in the case of cuttings rolling(normal drilling)and saltation(pump off for sand settling)under NGH adhesion in the laterals was established according to the force and migration laws of cuttings under the condition of multiphase flow in a horizontal well and the particle migration theory.Then,numerical simulation was conducted and the influential factors and migration laws of cuttings starting in the case of normal drilling and pump off were analyzed.And the following results were obtained.First,the critical starting flow rate decreases with the rise of NGH abundance and it is higher when the NGH adhesion is taken into account.Besides,the higher the NGH abundance,the greater the effect of NGH adhesion.Second,the critical starting flow rate increases with the rise of drilling cuttings particle size when the NGH abundance is less than 85%;and it decreases with the rise of drilling cuttings particle size when the NGH abundance is more than 85%.Third,the critical starting flow rate decreases with the rise of drilling fluid density and viscosity.And fourth,under the same conditions,the critical return rate for saltation is about 1.28 times that for rolling.It is suggested that the rolling model should be adopted for the normal drilling while the saltation model for the recycle after pump-off sand settling.The research results are of great significance to the optimization of NGH drilling parameters and the reduction of drilling safety risks.展开更多
车轮损伤严重影响地铁列车轮对的服役寿命,为分析地铁不同客流量的列车对车轮损伤的影响规律,以地铁B型车为研究对象,建立车辆轨道系统动力学模型并计算全局接触参数,采用Archard磨耗模型仿真分析车轮磨耗特征,采用Kik-Piotrowski模型...车轮损伤严重影响地铁列车轮对的服役寿命,为分析地铁不同客流量的列车对车轮损伤的影响规律,以地铁B型车为研究对象,建立车辆轨道系统动力学模型并计算全局接触参数,采用Archard磨耗模型仿真分析车轮磨耗特征,采用Kik-Piotrowski模型模拟轮轨接触,在UM RCF of Rails模块分析不同客流荷载下滚动接触疲劳的变化规律。结果表明车轮磨耗和滚动接触疲劳受客流荷载的影响,客流荷载越大,磨耗和滚动接触疲劳值也随之增大;C型曲线下,客流荷载对1、4位车轮轮缘和踏面磨耗速率影响都要大于2、3位车轮;直线上车轮磨耗速率受客流荷载影响呈现由慢到快随后变缓的趋势;客流荷载的变化不会使车轮疲劳损伤区域发生变化且直线车轮损伤范围比曲线车轮要大。该结论为后期地铁列车车轮维修提供了理论基础。展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.52072156,51675240)Jiangsu Provincial Youth Fund of China(Grant No.KB20160528)+1 种基金Jiangsu Provincial Six Talents Summit Program of China(Grant No.JXQC-011)Jiangsu University Senior Talents Startup Fund(Grant No.1291120046).
文摘The current research of tire aerodynamics mainly focus on the isolated and simplified tread tire.Compared with the real complex pattern tire,the tread pattern structure and deformed profile of a loaded tire has a greatly influence on tire aerodynamic drag.However,the mechanisms of the isolated loaded tires with different tread patterns effects on the aerodynamic drag are subjects worthy of discussion.The purpose of this study is to experimentally and compu-tationally investigate the aerodynamic characteristics of three tires 185/65 R14 with different patterns under loaded.A wind tunnel test model was first established using three-dimensional(3D)printing with a ratio of 1:1,and the pres-sure coefficients C_(p) of the three tires with different patterns are measured.The paper then conducted computational fluid dynamics(CFD)simulations for analyzing the pressure and flow characteristics.The accuracy of CFD simulation is verified by comparing the simulation results with the test results of pressure coefficients C_(p),and they are of good consistency.While,the general analysis of pressure coefficients C_(p) results of the three tires indicates high-pressure area on the windward surface,and occurrence of low-pressure area on the leeward surface,the pressure coefficients C_(p) of all three tires decreased firstly and then increased along in the air flow direction.The authors finally analyzed the effect of tread patterns on the flow field around the tire and revealed the differences between flow characteristics and aerodynamic drag.The results show that,angle of tire lateral groove has great effect on the flow field characteristics such that;the more the angle of lateral groove agrees with the air flow direction,the less the flow separation and flow vortices,and a minimum observable aerodynamic drag.The research provides a guidance for the design of low aerodynamic drag tires,and helps to illustrate the impact of tire aerodynamics on the car body in the future.
基金Project supported by the National Major R&D Program“New technology for test of marine natural gas hydrates through solid fluidization”(No.2016YFC0304008)the Key Program of National Natural Science Foundation of China“Theory and key issues for measurement and control of managed pressure drilling”(No.51334003).
文摘When a horizontal well is drilled through the natural gas hydrate(NGH)strata with different abundance,the NGH-bearing solid debris tends to lead to the deposit and adhesion of solid particles in the lateral sections and consequently cuttings carrying is not smooth.In this paper,the critical return rate model of drilling fluid in the case of cuttings rolling(normal drilling)and saltation(pump off for sand settling)under NGH adhesion in the laterals was established according to the force and migration laws of cuttings under the condition of multiphase flow in a horizontal well and the particle migration theory.Then,numerical simulation was conducted and the influential factors and migration laws of cuttings starting in the case of normal drilling and pump off were analyzed.And the following results were obtained.First,the critical starting flow rate decreases with the rise of NGH abundance and it is higher when the NGH adhesion is taken into account.Besides,the higher the NGH abundance,the greater the effect of NGH adhesion.Second,the critical starting flow rate increases with the rise of drilling cuttings particle size when the NGH abundance is less than 85%;and it decreases with the rise of drilling cuttings particle size when the NGH abundance is more than 85%.Third,the critical starting flow rate decreases with the rise of drilling fluid density and viscosity.And fourth,under the same conditions,the critical return rate for saltation is about 1.28 times that for rolling.It is suggested that the rolling model should be adopted for the normal drilling while the saltation model for the recycle after pump-off sand settling.The research results are of great significance to the optimization of NGH drilling parameters and the reduction of drilling safety risks.
文摘车轮损伤严重影响地铁列车轮对的服役寿命,为分析地铁不同客流量的列车对车轮损伤的影响规律,以地铁B型车为研究对象,建立车辆轨道系统动力学模型并计算全局接触参数,采用Archard磨耗模型仿真分析车轮磨耗特征,采用Kik-Piotrowski模型模拟轮轨接触,在UM RCF of Rails模块分析不同客流荷载下滚动接触疲劳的变化规律。结果表明车轮磨耗和滚动接触疲劳受客流荷载的影响,客流荷载越大,磨耗和滚动接触疲劳值也随之增大;C型曲线下,客流荷载对1、4位车轮轮缘和踏面磨耗速率影响都要大于2、3位车轮;直线上车轮磨耗速率受客流荷载影响呈现由慢到快随后变缓的趋势;客流荷载的变化不会使车轮疲劳损伤区域发生变化且直线车轮损伤范围比曲线车轮要大。该结论为后期地铁列车车轮维修提供了理论基础。
