变道超车过程的CFD数值模拟研究
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摘要
伴随着机械制造技术的快速发展和高速公路数量的提高,汽车高速行驶的时间比率大大增加;同时随着汽车保有量的飞速提高,汽车在路面上的行驶工况也越来越复杂,经常会出现超车、会车、队列行驶等情况。当汽车在高速超车时,车身周围流场不断急剧变化,车身周围的空气流场间也产生强烈的气动干扰,致使车辆所受的六分力不断的变化,进而造成车辆发生偏移和转移,严重影响车辆行驶时的稳定和安全。我国每年高速公路碰撞事故中与高速超车有关的占很大比例,给国家和人民的生命财产带来了极大的损失。因此研究汽车高速超车过程中的空气动力学特性具有非常重要的意义。
国际上对汽车直道超车过程的空气动力学特性一直十分重视,但是针对变道超车过程的空气动力学特性的研究还尚未展开。到目前为止,已经先后有很多家知名大学和研究机构应用CFD模拟方法对直道超车过程进行了仿真分析,但大部分CFD模拟方法都采用的是不连续网格方法。本文基于Ahmed汽车简化模型,采用重叠网格和不连续网格两种方法分别对直道超车过程的外部流场进行了数值仿真。通过比较在此过程中的主超车与被超车的阻力系数、升力系数的变化规律以及车身表面压强系数分布情况,验证了重叠网格应用于超车过程外部流场数值仿真上的适用性和准确性。并分析了重叠网格方法的计算原理和目前存在的问题,提出了解决此问题的方法。
在此基础上,本文进一步的开创性的应用重叠网格方法实现了变道超车过程的外部流场数值仿真,通过分析主超车与被超车的阻力系数、升力系数、侧向力系数的关系与变化规律,揭示了在变道超车过程中,两车外部流场相互干扰作用的变化规律。
本文通过以上计算和分析,指出了重叠网格方法在汽车外流场仿真模拟方面的潜力,并为解决实际车型的变道超车等问题提出了简便实用的方法,具有一般指导意义。
With the rapid development of mechanical manufacturing technology and increase of the numbers of highways, the time of high-speed running has been greatly increased and the driving conditions become more complex. When the cars are overtaking at a high speed, the flow fields around the car body will change constantly and produce a strong aerodynamic interference. It will result the constant changing of the six-pitch forces and cause shifts of vehicles, which seriously affect the stability and security of the vehicles. The annual collisions of automotive have a large proportion of overtaking with a high speed in china. Therefore, the research of aerodynamic characteristics during the high speed overtaking is very important and meaningful.
Many famous universities and research institutes have finished the calculation and simulation of overtaking by CFD (Computational Fluid Dynamics) analysis process, but so far the most of the CFD calculation methods are based on discontinuous mesh method. The overset mesh and discontinuous mesh will be used respectively on the numerical simulation of the external flow field of overtaking in line based on the Ahmed model. In this process, the applicability and accuracy of overset mesh method in simulating the automotive external flow field are proved by comparing the variation of the aerodynamic coefficient and the distribution of body surface pressure. The principle and the problems of the calculation of the overset mesh method are pointed out, and the solving ways are analyzing too.
Thus, the overset mesh method is used to finish the numerical simulation of the external flow field of overtaking by switching lines for the first time. The variation law of the aerodynamic interference is researched by the analysis of the variation of the aerodynamic coefficient and the effects to the safety are analyzed.
These calculations show the potential of the overset mesh method to solve the problems such as overtaking by switching lines and provide a way to solve such problems of the actual vehicles.
国际上对汽车直道超车过程的空气动力学特性一直十分重视,但是针对变道超车过程的空气动力学特性的研究还尚未展开。到目前为止,已经先后有很多家知名大学和研究机构应用CFD模拟方法对直道超车过程进行了仿真分析,但大部分CFD模拟方法都采用的是不连续网格方法。本文基于Ahmed汽车简化模型,采用重叠网格和不连续网格两种方法分别对直道超车过程的外部流场进行了数值仿真。通过比较在此过程中的主超车与被超车的阻力系数、升力系数的变化规律以及车身表面压强系数分布情况,验证了重叠网格应用于超车过程外部流场数值仿真上的适用性和准确性。并分析了重叠网格方法的计算原理和目前存在的问题,提出了解决此问题的方法。
在此基础上,本文进一步的开创性的应用重叠网格方法实现了变道超车过程的外部流场数值仿真,通过分析主超车与被超车的阻力系数、升力系数、侧向力系数的关系与变化规律,揭示了在变道超车过程中,两车外部流场相互干扰作用的变化规律。
本文通过以上计算和分析,指出了重叠网格方法在汽车外流场仿真模拟方面的潜力,并为解决实际车型的变道超车等问题提出了简便实用的方法,具有一般指导意义。
With the rapid development of mechanical manufacturing technology and increase of the numbers of highways, the time of high-speed running has been greatly increased and the driving conditions become more complex. When the cars are overtaking at a high speed, the flow fields around the car body will change constantly and produce a strong aerodynamic interference. It will result the constant changing of the six-pitch forces and cause shifts of vehicles, which seriously affect the stability and security of the vehicles. The annual collisions of automotive have a large proportion of overtaking with a high speed in china. Therefore, the research of aerodynamic characteristics during the high speed overtaking is very important and meaningful.
Many famous universities and research institutes have finished the calculation and simulation of overtaking by CFD (Computational Fluid Dynamics) analysis process, but so far the most of the CFD calculation methods are based on discontinuous mesh method. The overset mesh and discontinuous mesh will be used respectively on the numerical simulation of the external flow field of overtaking in line based on the Ahmed model. In this process, the applicability and accuracy of overset mesh method in simulating the automotive external flow field are proved by comparing the variation of the aerodynamic coefficient and the distribution of body surface pressure. The principle and the problems of the calculation of the overset mesh method are pointed out, and the solving ways are analyzing too.
Thus, the overset mesh method is used to finish the numerical simulation of the external flow field of overtaking by switching lines for the first time. The variation law of the aerodynamic interference is researched by the analysis of the variation of the aerodynamic coefficient and the effects to the safety are analyzed.
These calculations show the potential of the overset mesh method to solve the problems such as overtaking by switching lines and provide a way to solve such problems of the actual vehicles.
引文
[1]傅力敏.汽车空气动力学数值计算[M].北京:北京理工大学出出版社, 2000.
[2]傅力敏,贺宝琴,吴允柱等.汽车超车过程的空气动力特性研究[J].空气动力学学报, 2007, 25(3): 351-356.
[3]谷正气.汽车空气动力学[M].北京:人民交通出版社, 1999.
[4]陈振明.微型客车外流场数值模拟[D].重庆:重庆交通大学, 2008.
[5] White R G S. A Rating Method for Assessing Vehicle Aerodynamic Drag coefficients[J]. MIRA-Rep, 1967, (11): 12-15.
[6]赛伯里尔斯基著,杨尊正,邹仲贤译.汽车空气动力学[M].北京:人民交通出版社, 1984.
[7] Zabat M, Frascaroli S, Browand F. Drag Measurements on 2,3&4 Car Platoons[C]. SAE Paper, 1994-04-21, Detroit, 1994.
[8] Tsuei L, Savas O. A Wind Tunnel Investigation of the Transient Aerodynamic Effects on a Four-Car Platoon during Passing Maneuvers[C]. SAE Paper, 2001-01-0875, Detroit, 2001.
[9] Telionis D P, Fahrner C J, Jones G S. An experimental study of highway aerodynamic interference[J]. Journal of Wind Engineering and Industrial Aerodynamics, 1979, (5): 113-125.
[10] Azim A F, Gawad A F. A Flow Visualization Study of the Aerodynamic Interference Between Passenger Cars[C]. SAE Paper, 2001-01-0355, Detroit, 2001.
[11] Yamamoto S, Yanagimoto K, Fukuda H, et al. Aerodynamic influence of a passing vehicle on the stability of the other vehicles[C]. JSAE, 4-18-1-39, Tokyo, 1997.
[12] Gillieron P, Noger C. Contribution to the analysis of transient aerodynamic effects acting on vehicles[C]. SAE Paper, 2004-01-1311, Detroit, 2004.
[13] Corin R J, He L, Dominy R G. A CFD investigation into transient aerodynamic forces on overtaking road vehicle models[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2008, 96: 1390-1411.
[14]谷正气.大客车模型的气动特性研究[J].客车技术与研究, 1996, 18(2): 69-72.
[15]傅立敏,蔡国华.降低国产轿车阻力的风洞试验研究[J].空气动力学学报, 1998, 16(2): 147-153.
[16]欧阳鸿武,张志沛,高延令.轿车外流场的二维数值模拟[[J].汽车工程, 1997, 19(5): 302-306.
[17]梁德旺,秦毅.汽车气动力计算[J].南京航空航天大学学报, 1998, 30(2): 207~210.
[18]张奇.高速车辆车头改进的空气动力学特性研究[D].南京:南京航空航天大学, 2006.
[19]范土杰,王开春.国产新型轿车空气动力特性的三维仿真计算[J].汽车工程, 2000, 22(5): 293-295.
[20]邓亚东,江贤军.电动客车外形设计与外流场数值仿真[J].武汉理工大学学报, 2003, 25(1): 61-64.
[21]傅立敏,贺宝琴,吴允柱等.汽车超车过程的空气动力特性研究[J].空气动力学学报, 2007, 25(3): 351-356.
[22]吴允柱,贺宝琴,傅立敏.车速对超车车辆瞬态气动特性的影响[J].吉林大学学报, 2007, 37(5): 1009-1013.
[23]张世村.超车过程流场瞬态数值模拟分析[D].长春:吉林大学, 2006.
[24]张英朝,李杰,李玉虎等.轿车会车时气动特性的数值模拟[J].江苏大学学报, 2008, 29(2): 119-122.
[25]张建立,张国忠. CFD在汽车空气动力学中的应用[J].沈阳大学学报, 2006, 18(4): 15-18.
[26]许华舫.空气动力学基础[M].北京:北京航空学院出版社, 1987.
[27]倪冬香.乘员舱内流场数值模拟理论基础与方法[D].上海:上海交通大学, 2010.
[28]宋振寰,朱炳哲.计算流体力学在模拟汽车外流场研究方面的发展状况[J].汽车科技, 2002, (1): 5-7.
[29] Ogawa S, Kamioka T, Geroge A R. Review of Aerodynamic Noise Prediction Using CFD[C]. SAE Paper, 1999-01-1126, Warrendale, 1999.
[30] Uchida K, Okumura K. Aerodynamic Noise Simulation Based on Lattice Boltzmann Method[C]. SAE Paper, 1999-01-1127, Warrendale, 1999.
[31] Lee M, Lee J, Kim D. Reduction of Aeolian Noise from Roof Rack Crossbars Using Asymmetric Cross-Section Geometry[C]. SAE Paper, 2002-01-1275, Warrendale, 2002.
[32] Strachan R K, Knowles K, Lawson N J. A CFD and Experimental Study of an Ahmed Reference Model[C]. SAE Paper, 2004-01-0442, Warrendale, 2004.
[33]傅立敏,扶原放.轿车并列行驶湍流特性的数值模拟[J].吉林大学学报, 2005, 35(4): 358-362.
[34]阎超.计算流体力学方法及应用[M].北京:北京航空航天大学出版社, 2006.
[35]王福军.计算流体动力学分析[M].北京:清华大学出版社, 2004.
[36]吴德铭,郜冶.实用计算流体力学[M].哈尔滨:哈尔滨工程大学出版社, 2006.
[37]周正贵.计算流体力学基础理论与实际应用[M].南京:东南大学出版社, 2008.
[38]张国强,吴家鸣.流体力学[M].北京:机械工业出版社. 2006.
[39] Emmerich S J, McGrattan K B. Applications of a Large Eddy Simulation model to study room airflow[J]. ASHRAE Transaction, 1998, 104: 1128-1140.
[40] Launder B E, Spalding D B. The numerical computation of turbulent flow[J]. Computer Method in Applied Mechanics and Engineering, 1974, (3): 269-289.
[41] Victor Y, Orszag S A. Renormalization group analysis of turbulence, I basic theory[J]. J of Scientific Computing, 1986, (1): 1-51.
[42] Raedt H D, Michielsen K, Kole J S. Solving the Maxwell equations by the Chebyshev method: a one-step finite difference time domain algorithm[J] . IEEE transactions on antennas and propagation, 2003, 51(11): 3155- 3157.
[43]陈作斌.计算流体力学及应用[M].北京:国防工业出版社. 2003.
[44] Jameson A, Schmidt W, Turkel F. Numerical Solution of the Euler Equations by Finite Volume Methods Using Rung-Kutta Time - Stepping Schemes[C]. AIAA Paper, Palo Alto, 1981.
[45] Stein L R, Gentry R A, Hirt C W. Computational simulation of transient blast loading on three-dimensional structure[J]. Computer Methods in Applied Mechanics and Engineering, 1977, (11): 57-74.
[46] Cockburn B, Karniadakis G E, Shu C W. Discontinuous Galerkin Methods[J], Lecture Notes inComputational Science and Engineering, 2000, (11): 1-19.
[47] Koomullil R, Soni B, Singh R. A comprehensive generalized mesh system for CFD applications[J]. Mathe and Computers in Simulation, 2008, 78: 605-617.
[48] Fares E. Unsteady flow simulation of the Ahmed reference body using a lattic Boltzmann approach[J]. Computers & Fluids, 2006, 35: 940-950.
[49]张世村.超车过程流场瞬态数值模拟分析[D].长春:吉林大学, 2006.
[50] Sumitani K, Shinohara T. Research on Aerodynamic Noise around Automobiles[C]. JSAE, 948035, Tokyo, 1994.
[51]曾闽山,田冬玲,郭吉民.一种基于格网划分的高效Delaunay三角网格化算法[J].网络与通信, 2006, (3): 127-130.
[52]李春开,庞明勇.基于八叉树的四面体网格生成算法[J].微计算机信息, 2010, 26(3): 174-175.
[53] Craft T J, Gerasimov A V, Iacovides H. Progress in the Generalization of Wall-Function Treatments[J]. International Journal of Heat and Fluid Flow, 2002, 23: 148-160.
[54] Lienhart H, Becker S. Flow and Turbulence Structure in the Wake of a Simplified Car Model[C]. SAE Paper, 2003-01-0656, Warrendale, 2003.
[55] Gillieron P, Noger C. Contribution to the Analysis of Transient Aerodynamic Effects Acting on Vehicles[C]. SAE Paper, 2004-01-1311, Warrendale, 2004.
[2]傅力敏,贺宝琴,吴允柱等.汽车超车过程的空气动力特性研究[J].空气动力学学报, 2007, 25(3): 351-356.
[3]谷正气.汽车空气动力学[M].北京:人民交通出版社, 1999.
[4]陈振明.微型客车外流场数值模拟[D].重庆:重庆交通大学, 2008.
[5] White R G S. A Rating Method for Assessing Vehicle Aerodynamic Drag coefficients[J]. MIRA-Rep, 1967, (11): 12-15.
[6]赛伯里尔斯基著,杨尊正,邹仲贤译.汽车空气动力学[M].北京:人民交通出版社, 1984.
[7] Zabat M, Frascaroli S, Browand F. Drag Measurements on 2,3&4 Car Platoons[C]. SAE Paper, 1994-04-21, Detroit, 1994.
[8] Tsuei L, Savas O. A Wind Tunnel Investigation of the Transient Aerodynamic Effects on a Four-Car Platoon during Passing Maneuvers[C]. SAE Paper, 2001-01-0875, Detroit, 2001.
[9] Telionis D P, Fahrner C J, Jones G S. An experimental study of highway aerodynamic interference[J]. Journal of Wind Engineering and Industrial Aerodynamics, 1979, (5): 113-125.
[10] Azim A F, Gawad A F. A Flow Visualization Study of the Aerodynamic Interference Between Passenger Cars[C]. SAE Paper, 2001-01-0355, Detroit, 2001.
[11] Yamamoto S, Yanagimoto K, Fukuda H, et al. Aerodynamic influence of a passing vehicle on the stability of the other vehicles[C]. JSAE, 4-18-1-39, Tokyo, 1997.
[12] Gillieron P, Noger C. Contribution to the analysis of transient aerodynamic effects acting on vehicles[C]. SAE Paper, 2004-01-1311, Detroit, 2004.
[13] Corin R J, He L, Dominy R G. A CFD investigation into transient aerodynamic forces on overtaking road vehicle models[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2008, 96: 1390-1411.
[14]谷正气.大客车模型的气动特性研究[J].客车技术与研究, 1996, 18(2): 69-72.
[15]傅立敏,蔡国华.降低国产轿车阻力的风洞试验研究[J].空气动力学学报, 1998, 16(2): 147-153.
[16]欧阳鸿武,张志沛,高延令.轿车外流场的二维数值模拟[[J].汽车工程, 1997, 19(5): 302-306.
[17]梁德旺,秦毅.汽车气动力计算[J].南京航空航天大学学报, 1998, 30(2): 207~210.
[18]张奇.高速车辆车头改进的空气动力学特性研究[D].南京:南京航空航天大学, 2006.
[19]范土杰,王开春.国产新型轿车空气动力特性的三维仿真计算[J].汽车工程, 2000, 22(5): 293-295.
[20]邓亚东,江贤军.电动客车外形设计与外流场数值仿真[J].武汉理工大学学报, 2003, 25(1): 61-64.
[21]傅立敏,贺宝琴,吴允柱等.汽车超车过程的空气动力特性研究[J].空气动力学学报, 2007, 25(3): 351-356.
[22]吴允柱,贺宝琴,傅立敏.车速对超车车辆瞬态气动特性的影响[J].吉林大学学报, 2007, 37(5): 1009-1013.
[23]张世村.超车过程流场瞬态数值模拟分析[D].长春:吉林大学, 2006.
[24]张英朝,李杰,李玉虎等.轿车会车时气动特性的数值模拟[J].江苏大学学报, 2008, 29(2): 119-122.
[25]张建立,张国忠. CFD在汽车空气动力学中的应用[J].沈阳大学学报, 2006, 18(4): 15-18.
[26]许华舫.空气动力学基础[M].北京:北京航空学院出版社, 1987.
[27]倪冬香.乘员舱内流场数值模拟理论基础与方法[D].上海:上海交通大学, 2010.
[28]宋振寰,朱炳哲.计算流体力学在模拟汽车外流场研究方面的发展状况[J].汽车科技, 2002, (1): 5-7.
[29] Ogawa S, Kamioka T, Geroge A R. Review of Aerodynamic Noise Prediction Using CFD[C]. SAE Paper, 1999-01-1126, Warrendale, 1999.
[30] Uchida K, Okumura K. Aerodynamic Noise Simulation Based on Lattice Boltzmann Method[C]. SAE Paper, 1999-01-1127, Warrendale, 1999.
[31] Lee M, Lee J, Kim D. Reduction of Aeolian Noise from Roof Rack Crossbars Using Asymmetric Cross-Section Geometry[C]. SAE Paper, 2002-01-1275, Warrendale, 2002.
[32] Strachan R K, Knowles K, Lawson N J. A CFD and Experimental Study of an Ahmed Reference Model[C]. SAE Paper, 2004-01-0442, Warrendale, 2004.
[33]傅立敏,扶原放.轿车并列行驶湍流特性的数值模拟[J].吉林大学学报, 2005, 35(4): 358-362.
[34]阎超.计算流体力学方法及应用[M].北京:北京航空航天大学出版社, 2006.
[35]王福军.计算流体动力学分析[M].北京:清华大学出版社, 2004.
[36]吴德铭,郜冶.实用计算流体力学[M].哈尔滨:哈尔滨工程大学出版社, 2006.
[37]周正贵.计算流体力学基础理论与实际应用[M].南京:东南大学出版社, 2008.
[38]张国强,吴家鸣.流体力学[M].北京:机械工业出版社. 2006.
[39] Emmerich S J, McGrattan K B. Applications of a Large Eddy Simulation model to study room airflow[J]. ASHRAE Transaction, 1998, 104: 1128-1140.
[40] Launder B E, Spalding D B. The numerical computation of turbulent flow[J]. Computer Method in Applied Mechanics and Engineering, 1974, (3): 269-289.
[41] Victor Y, Orszag S A. Renormalization group analysis of turbulence, I basic theory[J]. J of Scientific Computing, 1986, (1): 1-51.
[42] Raedt H D, Michielsen K, Kole J S. Solving the Maxwell equations by the Chebyshev method: a one-step finite difference time domain algorithm[J] . IEEE transactions on antennas and propagation, 2003, 51(11): 3155- 3157.
[43]陈作斌.计算流体力学及应用[M].北京:国防工业出版社. 2003.
[44] Jameson A, Schmidt W, Turkel F. Numerical Solution of the Euler Equations by Finite Volume Methods Using Rung-Kutta Time - Stepping Schemes[C]. AIAA Paper, Palo Alto, 1981.
[45] Stein L R, Gentry R A, Hirt C W. Computational simulation of transient blast loading on three-dimensional structure[J]. Computer Methods in Applied Mechanics and Engineering, 1977, (11): 57-74.
[46] Cockburn B, Karniadakis G E, Shu C W. Discontinuous Galerkin Methods[J], Lecture Notes inComputational Science and Engineering, 2000, (11): 1-19.
[47] Koomullil R, Soni B, Singh R. A comprehensive generalized mesh system for CFD applications[J]. Mathe and Computers in Simulation, 2008, 78: 605-617.
[48] Fares E. Unsteady flow simulation of the Ahmed reference body using a lattic Boltzmann approach[J]. Computers & Fluids, 2006, 35: 940-950.
[49]张世村.超车过程流场瞬态数值模拟分析[D].长春:吉林大学, 2006.
[50] Sumitani K, Shinohara T. Research on Aerodynamic Noise around Automobiles[C]. JSAE, 948035, Tokyo, 1994.
[51]曾闽山,田冬玲,郭吉民.一种基于格网划分的高效Delaunay三角网格化算法[J].网络与通信, 2006, (3): 127-130.
[52]李春开,庞明勇.基于八叉树的四面体网格生成算法[J].微计算机信息, 2010, 26(3): 174-175.
[53] Craft T J, Gerasimov A V, Iacovides H. Progress in the Generalization of Wall-Function Treatments[J]. International Journal of Heat and Fluid Flow, 2002, 23: 148-160.
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