2. 黑龙江科技大学 机械工程学院, 黑龙江 哈尔滨 150022
2. College of Mechanical Engineering, Heilongjiang University of Science and Technology, Harbin 150022, China
从18世纪开始,在力学发展史上出现了与牛顿的矢量力学并驾齐驱的另一力学体系,即Lagrange于1755年写出了不朽名著《Mécanique Analytique》(分析力学),但这部专著在巴黎正式出版则迟至1788年[1]。这个体系的特点是对能量与功的分析代替对力与力矩的分析。W.R. Hamilton建立了Hamilton原理和正则方程,把分析力学推进一步[2]。从而在分析动力学中形成了Lagrange体系和Hamilton体系。
如何将经典分析动力学应用于连续介质力学的问题,一直是各国学者关注的研究课题。
我国出版的分析力学专著[3],将分析力学从质点刚体力学扩展到连续介质力学、从离散系统扩展到连续系统的问题。Goldstein H的名著(第三版)《Classical Mechanics》仍然作为一个专题研究连续体分析动力学[4]。我国学者将Lagrange方程应用于机构动力学分析[5-8],应用于振动系统[9]、防护工程[10]、电器系统和机电系统[11]等。研究了如何将Lagrange方程应用于非惯性系统[12-14],研究了弹性力学的Lagrange形式、弹性介质的Lagrange动力学和精确Cosserat弹性杆动力学的分析力学方法[15-17]。研究了完整系统三阶Lagrange方程、状态空间Lagrange函数和运动方程[18-19]。研究了关于Birkhoff方程和Lagrange方程分析力学问题[20]。
通过多年的研究,积累了不少成功的和失败的经验,在一定的意义上说,Lagrange方程和Hamilton原理都涉及变分学,Lagrange本人又是变分学的奠基人之一,从变分学的基本理论研究做起,或许是一条可行的途径。本文作者提出变分的逆运算变积概念,建立了变积方法,得到钱伟长的亲自推荐[21]。应用变积方法,与胡海昌一起建立了一般力学三类变量的广义变分原理[22]。刘高联[23]肯定了变积方法的首创性。这些研究使得微积分学中的积分、微分和导数在变分学中都有了对应的概念—变积、变分和变导,从而初步地将变分学扩充为变积分学。文献[24-25]的关于分析力学完整的叙述,成为本文研究的重要基础。
人们在研究如何将Lagrange方程应用于连续介质力学的问题时,几乎都是以弹性动力学为例展开的,尚未见哪位学者以流体力学为例展开研究。Lagrange在其不朽名著《Mécanique analytique》中用了较大篇幅研究流体力学,可惜的是,由于当时自然科学发展程度的限制,这位分析力学大师未能给出适用于流体力学的Lagrange方程,以至于使得各国学者继续研究了几百年,力图解决这个理论难题。本文应用变导的概念和运算法则,通过研究Lagrange方程中的求导的性质和Lagrange-Hamilton体系,逐步将Lagrange方程应用于理想流体动力学和不可压缩黏性流体动力学中,并探讨了如何将Lagrange方程应用于可压缩黏性流体动力学的问题。
1 Lagrange方程中的求导的性质为了说明这个问题,首先明确变导的概念。
设有定积分形式的泛函:
$ V = \int_a^b {F\left( {x,y,y'} \right){\rm{d}}x} $ | (1) |
其边界条件为
$ {y_{x = a}} = \alpha ,{y_{x = b}} = \beta $ | (2) |
对式(1)进行变分运算可得
$ \delta V = \int_a^b {\left( {\frac{{\partial F}}{{\partial y}}\delta y + \frac{{\partial F}}{{\partial y'}}\delta y'} \right){\rm{d}}x} $ | (3) |
应用分部积分
$ \int_a^b {\frac{{\partial F}}{{\partial y'}}\delta y'{\rm{d}}x} = \frac{{\partial F}}{{\partial y'}}\delta y\left| {_a^b} \right. - \int_a^b {\frac{{\rm{d}}}{{{\rm{d}}x}}\frac{{\partial F}}{{\partial y'}}\delta y{\rm{d}}x} $ | (4) |
将式(4)代入式(3),考虑到边界条件(2),整理可得
$ \delta V = \int_a^b {\left( {\frac{{\partial F}}{{\partial y}} - \frac{{\rm{d}}}{{{\rm{d}}x}}\frac{{\partial F}}{{\partial y'}}} \right)\delta y{\rm{d}}x} $ | (5) |
由于δy任意性,式(5)可以变换为
$ \frac{{\delta V}}{{\delta y}} = \int_a^b {\left( {\frac{{\partial F}}{{\partial y}} - \frac{{\rm{d}}}{{{\rm{d}}x}}\frac{{\partial F}}{{\partial y'}}} \right){\rm{d}}x} $ | (6) |
在微分学中,函数的微分表示为dy,自变量的微分表示为dx,微商表示为
接下来,分析Lagrange方程中的求导的性质。经典分析动力学中的Lagrange方程表示为
$ \frac{{\rm{d}}}{{{\rm{d}}z}}\frac{{\partial T}}{{\partial \mathit{\boldsymbol{\dot q}}}} - \frac{{\partial T}}{{\partial \mathit{\boldsymbol{q}}}} + \frac{{\partial U}}{{\partial \mathit{\boldsymbol{q}}}} = 0 $ | (7) |
其中,q=q(t)为广义坐标,一般分析动力学中均把其处理为广义坐标列阵
$ {\left[ {{q_1}\left( t \right),{q_2}\left( t \right), \cdots ,{q_{n - 1}}\left( t \right),{q_n}\left( t \right)} \right]^{\rm{T}}}\;\;\;i = 1,2, \cdots ,n $ | (8) |
在变分学中,基本上存在三级变量—自变量、可变函数和泛函。简单函数和泛函的区别在于:简单函数是自变量的函数,而泛函是可变函数的函数,独立自主地变化的可变函数称为自变函数。从不独立的可变函数也是自变函数的函数的角度看问题,不独立的可变函数也是泛函,可称其为子泛函。明确了变分学中的三级变量,对区分微积分中的导数和变积分学中的变导很有帮助。对自变量求导为微积分中的导数,而对可变函数的求导则为变积分中的变导。
在Lagrange方程中,有四个求导运算
严格说来,变导
这里指出,Lagrange本人已经注意到微分符号用“d”而变分符号用“δ”,而且应用了符号“
$ {\rm{d}}\frac{{\delta T}}{{\delta \dot \xi }} - \frac{{\delta T}}{{\delta \xi }} + \frac{{\delta U}}{{\delta \xi }} = 0 $ | (9) |
需要说明的是:当时Lagrange将
如果将ξ表示为q,将d表示为
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\delta T}}{{\delta \mathit{\boldsymbol{\dot q}}}} - \frac{{\delta T}}{{\delta \mathit{\boldsymbol{q}}}} + \frac{{\delta U}}{{\delta \mathit{\boldsymbol{q}}}} = 0 $ | (10) |
如果按照现在的习惯,将变导
变积分学中的变导和微积分学中的导数的运算法则,有时相同、有时不同,这类问题,在后面研究具体问题时可以明显的表现出来。
2 Lagrange方程应用于理想流体动力学 2.1 一类变量Lagrange方程应用于理想流体动力学在理想流体动力学中,取流体的位移uq为广义坐标,则一类变量Lagrange方程表示为
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {{\mathit{\boldsymbol{\dot u}}}^q}}} - \frac{{\partial T}}{{\partial {\mathit{\boldsymbol{u}}^q}}} + \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = 0 $ | (11) |
理想流体动力学的动能可以表示为
$ T = \iiint\limits_V {\frac{1}{2}\rho {{\mathit{\boldsymbol{\dot u}}}^q} \cdot {{\mathit{\boldsymbol{\dot u}}}^q}{\rm{d}}V} $ | (12) |
理想流体动力学的势能可以表示为
$ \begin{array}{*{20}{c}} {U = \iiint\limits_V {\left[ {\left( { - p\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - {f^q} \cdot {\mathit{\boldsymbol{u}}^q}} \right){\rm{d}}V - } \right.}} \\ {\left. {\iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q} \cdot {\mathit{\boldsymbol{u}}^q}{\rm{d}}S}} \right]{\rm{d}}t} \end{array} $ | (13) |
其先决条件
$ {\mathit{\boldsymbol{u}}^q} - \mathit{\boldsymbol{\bar u}} = 0 $ | (14) |
推导计算Lagrange方程中的各项
$ \frac{{\partial T}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = 0 $ | (15) |
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {{\mathit{\boldsymbol{\dot u}}}^q}}} = \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{\partial }{{\partial {{\mathit{\boldsymbol{\dot u}}}^q}}}\iiint\limits_V {\frac{1}{2}\rho {{\mathit{\boldsymbol{\dot u}}}^q} \cdot {{\mathit{\boldsymbol{\dot u}}}^q}{\rm{d}}V} = \iiint\limits_V {\rho {{\mathit{\boldsymbol{\dot u}}}^q}{\rm{d}}V} $ | (16) |
势能的变导项推导较为复杂
$ \begin{array}{*{20}{c}} {\frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = \frac{\partial }{{\partial {u^q}}}\left[ {\iiint\limits_V {\left( { - p\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - {f^q} \cdot {\mathit{\boldsymbol{u}}^q}} \right){\rm{d}}V - }} \right.} \\ {\left. {\iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q} \cdot {\mathit{\boldsymbol{u}}^q}{\rm{d}}S}} \right]{\rm{d}}t} \end{array} $ | (17) |
$ \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = \iiint\limits_V {\left( { - \frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}p\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - {f^q}} \right){\rm{d}}V} - \iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q}{\rm{d}}S} $ | (18) |
应用Green定理,并考虑到先决条件(14),可得
$ \begin{array}{*{20}{c}} {\iiint\limits_V { - \frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}p\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V} = \iiint\limits_V { - p\mathit{\boldsymbol{I}}:\frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}\nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V} = } \\ { - \iint\limits_{{S_w} + {S_f}} {p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S} + \iiint\limits_V {\nabla \cdot p\mathit{\boldsymbol{I}}\frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}{\mathit{\boldsymbol{u}}^q}{\rm{d}}V} = } \\ { - \iint\limits_{{S_f}} {p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S} + \iiint\limits_V {\nabla \cdot p\mathit{\boldsymbol{I}}{\rm{d}}V}} \end{array} $ | (19) |
将式(19)代入式(18),则得
$ \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = \iiint\limits_V {\left( {\nabla \cdot p\mathit{\boldsymbol{I}} - {f^q}} \right){\rm{d}}V} + \iint\limits_{{S_f}} {\left[ { - p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q}} \right]{\rm{d}}S} $ | (20) |
将相关各项代入Lagrange方程, 可得
$ \begin{array}{*{20}{c}} {\frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {{\mathit{\boldsymbol{\dot u}}}^q}}} - \frac{{\partial T}}{{\partial {\mathit{\boldsymbol{u}}^q}}} + \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = } \\ {\iiint\limits_V {\left( {\rho {{\mathit{\boldsymbol{\ddot u}}}^q} + \nabla \cdot p\mathit{\boldsymbol{I}} - {f^q}} \right){\rm{d}}V} + } \\ {\iint\limits_{{S_f}} {\left( { - p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q}} \right){\rm{d}}S} = 0} \end{array} $ | (21) |
脱去积分号,可得理想流体动力学方程
$ \rho {{\mathit{\boldsymbol{\ddot u}}}^q} + \nabla \cdot p\mathit{\boldsymbol{I}} - {\mathit{\boldsymbol{f}}^q} = 0 $ | (22) |
$ p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} + {\mathit{\boldsymbol{T}}^q} = 0 $ | (23) |
可见,理想流体动力学方程(22)和(23)与其先决条件(14)一起,构成封闭的微分方程组。
2.2 两类变量Lagrange方程应用于理想流体动力学在理想流体动力学中,取流体的速度
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} - \frac{{\partial T}}{{\partial {\mathit{\boldsymbol{u}}^q}}} + \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = 0 $ | (24) |
理想流体动力学的动能可以表示为
$ T = \iiint\limits_V {\frac{1}{2}\rho {\mathit{\boldsymbol{v}}^q} \cdot {\mathit{\boldsymbol{v}}^q}{\rm{d}}V} $ | (25) |
理想流体动力学的势能可以表示为
$ U = \iiint\limits_V {\left[ {\left( { - p\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - {\mathit{\boldsymbol{f}}^q} \cdot {\mathit{\boldsymbol{u}}^q}} \right){\rm{d}}V - \iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q} \cdot {\mathit{\boldsymbol{u}}^q}{\rm{d}}S}} \right]{\rm{d}}t} $ | (26) |
其先决条件
$ {\mathit{\boldsymbol{v}}^q} - \frac{{{\rm{d}}{\mathit{\boldsymbol{u}}^q}}}{{{\rm{d}}t}} = 0 $ | (27) |
$ {\mathit{\boldsymbol{u}}^q} - \mathit{\boldsymbol{\bar u}} = 0 $ | (28) |
推导计算Lagrange方程中的各项
$ \frac{{\partial T}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = 0 $ | (29) |
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {v^q}}} = \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{\partial }{{\partial {\mathit{\boldsymbol{v}}^q}}}\iiint\limits_V {\frac{1}{2}\rho {\mathit{\boldsymbol{v}}^q} \cdot {\mathit{\boldsymbol{v}}^q}{\rm{d}}V} = \iiint\limits_V {\rho {{\mathit{\boldsymbol{\dot v}}}^q}{\rm{d}}V} $ | (30) |
势能的变导项的推导较为复杂,引用2.1节的结果
$ \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = \left[ {\iiint\limits_V {\left( {\nabla \cdot p\mathit{\boldsymbol{I}} - {\mathit{\boldsymbol{f}}^q}} \right){\rm{d}}V} + \iint\limits_{{S_f}} {\left[ { - p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q}} \right]}} \right.{\rm{d}}S $ | (31) |
将相关各式代入Lagrange方程, 并考虑到先决条件(28),可得
$ \begin{array}{*{20}{c}} {\frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} - \frac{{\partial T}}{{\partial {\mathit{\boldsymbol{u}}^q}}} + \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = } \\ {\iiint\limits_V {\left( {\rho {{\mathit{\boldsymbol{\dot v}}}^q} + \nabla \cdot p\mathit{\boldsymbol{I}} - {\mathit{\boldsymbol{f}}^q}} \right){\rm{d}}V} - \iint\limits_{{S_f}} {\left[ {p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} + {\mathit{\boldsymbol{T}}^q}} \right]{\rm{d}}S} = 0} \end{array} $ | (32) |
脱去积分号,可得理想流体动力学方程
$ \rho {{\mathit{\boldsymbol{\dot v}}}^q} + \nabla \cdot p\mathit{\boldsymbol{I}} - {\mathit{\boldsymbol{f}}^q} = 0 $ | (33) |
$ p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} + {\mathit{\boldsymbol{T}}^q} = 0 $ | (34) |
可见,理想流体动力学方程(33)和(34)与其先决条件(28)一起构成封闭的微分方程组。
考虑到一类变量的Lagrange方程在流体动力学中应用较少,在以下各节中,不再专门讨论这类问题。
3 Lagrange方程应用于不可压缩黏性流体动力学由于黏性的存在,使得不可压缩黏性流体动力学成为非保守系统的力学问题。鉴于不可压缩黏性流体动力学的Lagrange方程是不可压缩黏性流体动力学的Hamilton型拟变分原理的拟驻值条件,本节是由不可压缩黏性流体动力学的Hamilton型拟变分原理推导出不可压缩黏性流体动力学的Lagrange方程,然后,再由不可压缩黏性流体动力学的Lagrange方程推导出不可压缩黏性流体动力学的控制方程。
不可压缩黏性流体动力学的Hamilton型拟变分原理可以表示为
$ \delta {\mathit{\Pi }_1} + \delta Q = 0 $ | (35) |
其中
$ \begin{array}{*{20}{c}} {{\mathit{\Pi }_1} = \int_{{t_0}}^{{t_1}} {\left\{ {\iiint\limits_V {\left[ {\frac{1}{2}\rho {\mathit{\boldsymbol{v}}^q} \cdot {\mathit{\boldsymbol{v}}^q} + p\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right):} \right.}} \right.} } \\ {\left. {\left. {\nabla {\mathit{\boldsymbol{u}}^q} + {\mathit{\boldsymbol{f}}^q} \cdot {\mathit{\boldsymbol{u}}^q}} \right]{\rm{d}}V + \iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q} \cdot {\mathit{\boldsymbol{u}}^q}{\rm{d}}S}} \right\}{\rm{d}}t} \end{array} $ | (36) |
$ \delta Q = \int_{{t_0}}^{{t_1}} {\left[ {\iiint\limits_V {\nabla {\mathit{\boldsymbol{u}}^q}:\delta \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right){\rm{d}}V}} \right]{\rm{d}}t} $ | (37) |
其先决条件
$ {\mathit{\boldsymbol{v}}^q} - \frac{{{\rm{d}}{\mathit{\boldsymbol{u}}^q}}}{{{\rm{d}}t}} = 0 $ | (38) |
$ {\mathit{\boldsymbol{u}}^q} - \mathit{\boldsymbol{\bar u}} = 0 $ | (39) |
式中:ρ是密度,为零阶张量(标量);vq为流体速度矢量(一阶张量);fq为单位体积流体所受的体积力矢量;μ为黏性系数标量;I为二阶单位张量;p为流体压强,为零阶张量(标量);nq为流体边界面单位外法向矢量;Tq为流体所受的面积力矢量;uq为流体位移;▽为梯度算子(又称Hamilton算子);V为体积;Sw为固壁边界面;Sf为自由表面。
系统的动能为
$ T = \iiint\limits_V {\frac{1}{2}\rho {\mathit{\boldsymbol{v}}^q} \cdot {\mathit{\boldsymbol{v}}^q}{\rm{d}}V} $ | (40) |
系统的势能为
$ U = \iiint\limits_V {\left( { - p\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - {\mathit{\boldsymbol{f}}^q} \cdot {\mathit{\boldsymbol{u}}^q}} \right){\rm{d}}V} - \iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q} \cdot {\mathit{\boldsymbol{u}}^q}{\rm{d}}S} $ | (41) |
将黏性阻力引起的流体剪切应力视为非保守力,表示为τNq=μ(▽vq+vq▽),则系统的拟势能为
$ {U_N} = \iiint\limits_V {\mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right):\nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V} = \iiint\limits_V {{\mathit{\boldsymbol{\tau }}_N}:\nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V} $ | (42) |
非保守系统的余虚功为
$ \begin{array}{*{20}{c}} {\delta Q = \int_{{t_0}}^{{t_1}} {\left[ {\iiint\limits_V {\nabla {\mathit{\boldsymbol{u}}^q}:\delta \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right){\rm{d}}V}} \right]{\rm{d}}t} = } \\ {\int_{{t_0}}^{{t_1}} {\left[ {\iiint\limits_V {\nabla {\mathit{\boldsymbol{u}}^q}:\delta {\mathit{\boldsymbol{\tau }}_N}{\rm{d}}V}} \right]{\rm{d}}t} } \end{array} $ | (43) |
经过如上的准备,可以将式(35)变换为
$ \begin{array}{*{20}{c}} {\delta {\mathit{\Pi }_1} + \delta Q = }\\ {\delta \int_{{t_0}}^{{t_1}} {\left( {T - U - {U_N}} \right){\rm{d}}t} + \delta Q = }\\ {\int_{{t_0}}^{{t_1}} {\left( {\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} \cdot \delta {\mathit{\boldsymbol{v}}^q} - \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q} - \frac{{\partial {U_N}}}{{\partial {\mathit{\boldsymbol{u}}^q}}} \cdot \delta {u^q}} \right){\rm{d}}t + \delta Q = 0} } \end{array} $ | (44) |
进行分部积分,考虑到运动学关系,
$ \int_{{t_0}}^{{t_1}} {\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} \cdot \delta {{\mathit{\boldsymbol{\dot u}}}^q}{\rm{d}}t} = \frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q}\left| {_{{t_0}}^{{t_1}}} \right. - \int_{{t_0}}^{{t_1}} {\frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q}{\rm{d}}t} $ | (45) |
将式(45)代入式(44),按惯例在时域边界t=t0和t=t1处取δu=0,可得
$ \begin{array}{*{20}{c}} {\int_{{t_0}}^{{t_1}} {\left( { - \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q} - \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q} - \frac{{\partial {U_N}}}{{\partial {\mathit{\boldsymbol{u}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q}} \right){\rm{d}}t} + }\\ {\delta Q = 0} \end{array} $ | (46) |
与τN有关的两项为
$ \begin{array}{*{20}{c}} {\int_{{t_0}}^{{t_1}} {\left( { - \frac{{\partial {U_N}}}{{\partial {\mathit{\boldsymbol{u}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q}} \right){\rm{d}}t} + \delta Q = } \\ {\int_{{t_0}}^{{t_1}} { - \delta {U_N}{\rm{d}}t} + \delta Q = } \\ {\int_{{t_0}}^{{t_1}} {\iiint\limits_V { - {\mathit{\boldsymbol{\tau }}_N}:\delta \nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V{\rm{d}}t}} + \int_{{t_0}}^{{t_1}} {\iiint\limits_V { - \delta {\mathit{\boldsymbol{\tau }}_N}:\nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V{\rm{d}}t}} + } \\ {\int_{{t_0}}^{{t_1}} {\iiint\limits_V {\nabla {\mathit{\boldsymbol{u}}^q}:\delta {\tau _N}{\rm{d}}V{\rm{d}}t}} + \int_{{t_0}}^{{t_1}} {\iiint\limits_V { - {\mathit{\boldsymbol{\tau }}_N}:\delta \nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V{\rm{d}}t}} } \end{array} $ | (47) |
应用Green定理,并考虑到先决条件(39),可得
$ \begin{array}{*{20}{c}} {\iiint\limits_V { - {\mathit{\boldsymbol{\tau }}_N}:\delta \nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V} = \iint\limits_{{S_f}} { - {\mathit{\boldsymbol{\tau }}_N} \cdot {\mathit{\boldsymbol{n}}^q} \cdot \delta {\mathit{\boldsymbol{u}}^q}{\rm{d}}S} + } \\ {\iiint\limits_V {\nabla \cdot {\tau _N} \cdot \delta {\mathit{\boldsymbol{u}}^q}{\rm{d}}V}} \end{array} $ | (48) |
将式(48)代入式(47),然后代入式(46),可得
$ \begin{array}{*{20}{c}} {\int_{{t_0}}^{{t_1}} {\left[ { - \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q} - \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} \cdot \delta {\mathit{\boldsymbol{u}}^q} + \iiint\limits_V {\nabla \cdot {\mathit{\boldsymbol{\tau }}_N} \cdot \delta {\mathit{\boldsymbol{u}}^q}dV} - } \right.} } \\ {\left. {\left. {\iint\limits_{{S_f}} {{\mathit{\boldsymbol{\tau }}_N} \cdot {\mathit{\boldsymbol{n}}^q} \cdot \delta {\mathit{\boldsymbol{u}}^q}{\rm{d}}S}} \right)} \right]{\rm{d}}t = } \\ {\int_{{t_0}}^{{t_1}} {\left[ { - \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} - \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} + \iiint\limits_V {\nabla \cdot {\mathit{\boldsymbol{\tau }}_N}dV} - } \right.} } \\ {\left. {\iint\limits_{{S_f}} {{\mathit{\boldsymbol{\tau }}_N} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S}} \right] \cdot \delta {u^q}{\rm{d}}t = 0} \end{array} $ | (49) |
由于δuq的任意性,故由上式可得不可压缩黏性流体动力学的两类变量的Lagrange方程
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} + \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} - \iiint\limits_V {\nabla \cdot {\mathit{\boldsymbol{\tau }}_N}{\rm{d}}V} + \iint\limits_{{S_f}} {{\mathit{\boldsymbol{\tau }}_N} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S} = 0 $ | (50) |
以下,应用不可压缩黏性流体动力学的两类变量的Lagrange方程来推导不可压缩黏性流体动力学的控制方程。
推导计算Lagrange方程中的各项,如前所述,有关动能的项为
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} = \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}}\iiint\limits_V {\frac{1}{2}\rho {\mathit{\boldsymbol{v}}^q} \cdot {\mathit{\boldsymbol{v}}^q}{\rm{d}}V} = \iiint\limits_V {\rho {{\mathit{\boldsymbol{\dot v}}}^q}{\rm{d}}V} $ | (51) |
有关势能的变导的项为
$ \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = \iiint\limits_V {\left( {\nabla \cdot p\mathit{\boldsymbol{I}} - {\mathit{\boldsymbol{f}}^q}} \right){\rm{d}}V} + \iint\limits_{{S_f}} {\left[ { - p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q}} \right]{\rm{d}}S} $ | (52) |
与τN有关的两项为
$ \begin{array}{*{20}{c}} { - \iiint\limits_V {\nabla \cdot {\mathit{\boldsymbol{\tau }}_N}dV} + \iint\limits_{{S_f}} {{\mathit{\boldsymbol{\tau }}_N} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S} = } \\ { - \iiint\limits_V {\nabla \cdot \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right){\rm{d}}V} + } \\ {\iint\limits_{{S_f}} {\mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right) \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S}} \end{array} $ | (53) |
将相关各式代入Lagrange方程, 可得
$ \begin{array}{*{20}{c}} {\iiint\limits_{{V^q}} {\left\{ {\rho {{\mathit{\boldsymbol{\dot v}}}^q} + \nabla \cdot \left[ {p\mathit{\boldsymbol{I}} - \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right)} \right] - {f^q}} \right\}{\rm{d}}V} + } \\ {\iint\limits_{{S_f}} {\left[ { - p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} + \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right) \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q}} \right]{\rm{d}}S} = 0} \end{array} $ | (54) |
进一步处理为
$ \rho {{\mathit{\boldsymbol{\dot v}}}^q} + \nabla \cdot \left[ {p\mathit{\boldsymbol{I}} - \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right)} \right] - {\mathit{\boldsymbol{f}}^q} = 0 $ | (55) |
$ - p\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} + \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right) \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q} = 0 $ | (56) |
可见,不可压缩黏性流体动力学方程(55)、(59)和其先决条件(38)、(39)一起构成封闭的微分方程组。
4 关于Lagrange方程应用于可压缩黏性流体动力学的探讨本节探讨将Lagrange方程应用于可压缩黏性流体动力学的问题。这是研究将Lagrange方程应用于流体动力学的最一般的研究课题,因为物理方面和数学方面的复杂性,本文未能给出全面的、深入的研究,以下给出的仅仅是一个初步的探讨。
两类变量Lagrange方程表示为
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} + \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} - \iiint\limits_V {\nabla \cdot {\mathit{\boldsymbol{\tau }}_N}{\rm{d}}V} + \iint\limits_{{S_f}} {{\mathit{\boldsymbol{\tau }}_N} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S} $ | (57) |
可压缩黏性流体动力学的动能可以表示为
$ T = \iiint\limits_V {\frac{1}{2}\rho {\mathit{\boldsymbol{v}}^q} \cdot {\mathit{\boldsymbol{v}}^q}{\rm{d}}V} $ | (58) |
可压缩黏性流体动力学的势能可以表示为
$ \begin{array}{*{20}{c}} {U = \iiint\limits_V {\left[ { - \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{d\rho }}{{dt}}} \right)\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - {\mathit{\boldsymbol{f}}^q} \cdot {\mathit{\boldsymbol{u}}^q}} \right]{\rm{d}}V} - } \\ {\iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q} \cdot {\mathit{\boldsymbol{u}}^q}{\rm{d}}S}} \end{array} $ | (59) |
可压缩黏性流体动力学的非保守应力为
$ \mathit{\boldsymbol{\tau }}_N^q = \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right) $ | (60) |
其先决条件
$ {\mathit{\boldsymbol{v}}^q} - \frac{{{\rm{d}}{\mathit{\boldsymbol{u}}^q}}}{{{\rm{d}}t}} = 0 $ | (61) |
$ {\mathit{\boldsymbol{u}}^q} - \mathit{\boldsymbol{\bar u}} = 0 $ | (62) |
推导计算Lagrange方程中的各项
$ \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} = \frac{{\rm{d}}}{{{\rm{d}}t}}\frac{\partial }{{\partial {\mathit{\boldsymbol{v}}^q}}}\iiint\limits_V {\frac{1}{2}\rho {\mathit{\boldsymbol{v}}^q} \cdot {\mathit{\boldsymbol{v}}^q}{\rm{d}}V} = \iiint\limits_V {\rho {{\mathit{\boldsymbol{\dot v}}}^q}{\rm{d}}V} $ | (63) |
势能的变导项的推导较为复杂
$ \begin{array}{*{20}{c}} {\frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = \frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}\left\{ {\iiint\limits_V {\left[ { - \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - } \right.}} \right.} \\ {\left. {\left. {{\mathit{\boldsymbol{f}}^q} \cdot {\mathit{\boldsymbol{u}}^q}} \right]{\rm{d}}V - \iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q} \cdot {\mathit{\boldsymbol{u}}^q}{\rm{d}}S}} \right\}{\rm{d}}t} \\ {\frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = \iiint\limits_V {\left[ { - \frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}\left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q} - {\mathit{\boldsymbol{f}}^q}} \right]{\rm{d}}V} - } \\ {\iint\limits_{{S_f}} {{\mathit{\boldsymbol{T}}^q}{\rm{d}}S}} \end{array} $ | (65) |
应用Green定理,并考虑到先决条件(62),可得
$ \begin{array}{*{20}{c}} {\iiint\limits_V { - \frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}\left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}}:\nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V} = } \\ {\iiint\limits_V { - \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}}:\frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}\nabla {\mathit{\boldsymbol{u}}^q}{\rm{d}}V} = } \\ { - \iint\limits_{{S_w} + {S_f}} {\left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q}\frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}{\mathit{\boldsymbol{u}}^q}{\rm{d}}S} + } \\ {\iiint\limits_V {\nabla \cdot \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}}\frac{\partial }{{\partial {\mathit{\boldsymbol{u}}^q}}}{\mathit{\boldsymbol{u}}^q}{\rm{d}}V} = } \\ { - \iint\limits_{{S_f}} {\left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S} + } \\ {\iiint\limits_V {\nabla \cdot \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}}{\rm{d}}V}} \end{array} $ | (66) |
将式(66)代入式(65),则得
$ \begin{array}{*{20}{c}} {\frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} = \iiint\limits_V {\left( {\nabla \cdot \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}} - {\mathit{\boldsymbol{f}}^q}} \right){\rm{d}}V} + } \\ {\iint\limits_{{S_f}} {\left( { - \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q}} \right){\rm{d}}S}} \end{array} $ | (67) |
与τN有关的两项为
$ \begin{array}{*{20}{c}} { - \iiint\limits_V {\nabla \cdot {\mathit{\boldsymbol{\tau }}_N}{\rm{d}}V} + \iint\limits_{{S_f}} {{\mathit{\boldsymbol{\tau }}_N} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S} = } \\ { - \iiint\limits_V {\nabla \cdot \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right){\rm{d}}V} + \iint\limits_{{S_f}} {\mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right) \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S}} \end{array} $ | (68) |
将相关各式代入Lagrange方程, 可得
$ \begin{array}{*{20}{c}} {\frac{{\rm{d}}}{{{\rm{d}}t}}\frac{{\partial T}}{{\partial {\mathit{\boldsymbol{v}}^q}}} + \frac{{\partial U}}{{\partial {\mathit{\boldsymbol{u}}^q}}} - \iiint\limits_V {\nabla \cdot {\mathit{\boldsymbol{\tau }}_N}{\rm{d}}V} + \iint\limits_{{S_f}} {{\mathit{\boldsymbol{\tau }}_N} \cdot {\mathit{\boldsymbol{n}}^q}{\rm{d}}S} = } \\ {\iiint\limits_V {\left\{ {\rho {{\mathit{\boldsymbol{\dot v}}}^q} + \nabla \cdot \left[ {\left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}}} \right.} \right.}} \\ {\left. {\left. {\mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right)} \right] - {\mathit{\boldsymbol{f}}^q}} \right\}{\rm{d}}V + } \\ {\iint\limits_{{S_f}} {\left[ { - \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)I \cdot {n^q} + } \right.}} \\ {\left. {\mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right) \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q}} \right]{\rm{d}}S = 0} \end{array} $ | (69) |
进一步处理为
$ \begin{array}{*{20}{c}} {\rho {{\mathit{\boldsymbol{\dot v}}}^q} + \nabla \cdot \left[ {\left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}} - \mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right)} \right] - } \\ {{\mathit{\boldsymbol{f}}^q} = 0} \\ { - \left( {p + \frac{2}{3}\mu \frac{1}{\rho }\frac{{{\rm{d}}\rho }}{{{\rm{d}}t}}} \right)\mathit{\boldsymbol{I}} \cdot {\mathit{\boldsymbol{n}}^q} + } \\ {\mu \left( {\nabla {\mathit{\boldsymbol{v}}^q} + {\mathit{\boldsymbol{v}}^q}\nabla } \right) \cdot {\mathit{\boldsymbol{n}}^q} - {\mathit{\boldsymbol{T}}^q} = 0} \end{array} $ | (71) |
可见,可压缩黏性流体动力学方程(70)、(71)和其先决条件(61)、(62)一起,构成封闭的微分方程组。
5 结论1) 应用变导运算法则,将Lagrange方程应用于理想流体动力学,得到理想流体动力学控制方程。
2) 应用Lagrange-Hamilton体系,对于非保守系统,Lagrange方程是Hamilton型拟变分原理的拟驻值条件。基于这一理论,借助于不可压缩黏性流体动力学Hamilton型拟变分原理,应用变分方法推导其Lagrange方程,进而应用Lagrange方程推导不可压缩黏性流体动力学的控制方程。
3) 探讨了将Lagrange方程应用于可压缩黏性流体动力学,得到可压缩黏性流体动力学的控制方程。
论文较全面地解决了将Lagrange方程应用于流体动力学的问题。
[1] |
LAGRANGE J L. Mécanique analytique[M]. Paris:Ve Courcier, 1811(Originally published in l788).
(0)
|
[2] |
HAMILTON W R. On a general method in dynamics[M].[S.l.]:Philosophical Transaction of the Royal Society, Part Ⅰ, 1834:247-308.
(0)
|
[3] |
汪家訸. 分析动力学[M]. 北京: 高等教育出版社, 1958.
(0)
|
[4] |
GOLDSTEIN H. Classical Mechanics[M]. 2nd ed.[S.l.]:Addison-Wesley Publishing Co., 1980.
(0)
|
[5] |
赵俊伟, 李雪锋, 陈国强. 基于Lagrange方法的3-PRS并联机构动力学分析[J]. 机械设计与研究, 2015, 31(2): 1-5. ZHAO Junwei, LI Xuefeng, CHEN Guoqiang. The dynamics equation of A 3-PRS parallel manipulator based on lagrange method[J]. Machine design & research, 2015, 31(2): 1-5. (0) |
[6] |
林良明, 吴俊. 用Lagrange方程描述假手机构动力学的研究[J]. 中国生物医学工程学报, 1989, 8(1): 1-8. LIN Liangming, WU Jun. Description of mechanism dynamics of prosthetichand using lagrangian equation[J]. Chinese journal of biomedical engineering, 1989, 8(1): 1-8. (0) |
[7] |
王启明, 汪劲松, 刘辛军, 等. 二移动自由度并联操作臂的动力学建模[J]. 清华大学学报(自然科学版), 2002, 42(11): 1469-1472. WANG Qiming, WANG Jinsong, LIU Xinjun, et al. Dynamic modeling of a parallel manipulator with two translational degrees of freedom[J]. Journal of Tsinghua University (science and technology), 2002, 42(11): 1469-1472. DOI:10.3321/j.issn:1000-0054.2002.11.015 (0) |
[8] |
孙伟, 汪博, 鲁明, 等. 基于拉格朗日方程的直线滚动导轨系统解析建模[J]. 计算机集成制造系统, 2012, 18(4): 781-786. SUN Wei, WANG Bo, LU Ming, et al. Analytical modeling of linear rolling guide system based on lagrange equation[J]. Computer integrated manufacturing systems, 2012, 18(4): 781-786. (0) |
[9] |
卢长福, 傅鹏, 黄诚, 等. Lagrange方程在振动系统中的应用[J]. 江西科学, 2013, 3(2): 148-150. LU Changfu, FU Peng, HUANG Cheng, et al. The application of lagrange equation in vibration systen[J]. Jiangxi science, 2013, 3(2): 148-150. (0) |
[10] |
赵晓兵, 方秦. Lagrange方程在防护工程中的应用及其相关的力学问题[J]. 防护工程, 2000(2): 28-32. ZHAO Xiaobing, FANG Qin. Application of Lagrange equation in protection engineering and its related mechanical problems[J]. Protection engineering, 2000(2): 28-32. (0) |
[11] |
靳希, 鲁炜. Lagrange方程应用于电系统和机电系统运动分析[J]. 上海电力学院学报, 2003, 19(4): 1-4. JIN Xi, LU Wei. The application of lagrange equation in the analysis of electric and electromechanical system[J]. Journal of Shanghai University of Electric Power, 2003, 19(4): 1-4. (0) |
[12] |
颜振珏. 非惯性参照系中的Lagrange方程[J]. 黔南民族师范学院学报, 2004, 24(6): 8-11. YAN Zhenyu. Lagrange equation in uninertia system[J]. Journal of Qiannan Normal University for Nationalities, 2004, 24(6): 8-11. (0) |
[13] |
廖旭. 非惯性系中的Lagrange方程及其应用[J]. 云南大学学报(自然科学版), 2004, 26(B07): 122-124. LIAO Xu. Lagrange equation in noninertial frame and application[J]. Journal of Yunnan University(natural sciences edition), 2004, 26(B07): 122-124. (0) |
[14] |
和兴锁, 宋明, 邓峰岩. 非惯性系下考虑剪切变形的柔性梁的动力学建模[J]. 物理学报, 2011, 60(4): 323-328. HE Xingsuo, SONG Ming, DENG Fengyan. Dynamic modeling of flexible beam with considering shear deformation in non-inertial reference frame[J]. Acta physica sinica, 2011, 60(4): 323-328. (0) |
[15] |
沈惠川. 弹性力学的Lagrange形式:用Routh方法建立弹性有限变形问题的基本方程[J]. 数学物理学报, 1998, 18(1): 78-88. SHEN Huichuan. Lagrange formalism of elasticity:building the basic equations on finite-deformation problems by routh's method[J]. Acta mathematica scientia, 1998, 18(1): 78-88. (0) |
[16] |
方刚, 张斌. 弹性介质的Lagrange动力学与地震波方程[J]. 物理学报, 2013(15): 248-253. FANG Gang, ZHANG Bin. Lagrangian dynamics and seismic wave align of elastic medium[J]. Acta physica sinica, 2013(15): 248-253. (0) |
[17] |
薛纭, 翁德玮, 陈立群. 精确Cosserat弹性杆动力学的分析力学方法[J]. 物理学报, 2013(4): 312-318. XUE Yun, WENG Dewei, CHEN Liqun. Methods of analytical mechanics for exact Cosserat elastic rod dynamics[J]. Acta physica sinica, 2013(4): 312-318. (0) |
[18] |
马善钧, 徐学翔, 黄沛天, 等. 完整系统三阶Lagrange方程的一种推导与讨论[J]. 物理学报, 2004, 53(11): 3648-3651. MA Shanjun, XU Xuexiang, HUANG Peitian, et al. The discussion on Lagrange equation containing third order derivatives[J]. Acta physica sinica, 2004, 53(11): 3648-3651. (0) |
[19] |
丁光涛. 状态空间Lagrange函数和运动方程[J]. 中国科学(G辑), 2009(6): 813-820. DING Guangtao. The state space Lagrange function and the corresponding equation of motion[J]. Science in China (series G), 2009(6): 813-820. (0) |
[20] |
梅凤翔. 广义Birkhoff系统动力学[M]. 北京: 北京理工大学出版社, 1996. MEI Fengxiang. Generalized Birkhoff system dynamics[M]. Beijing: Beijing Institute of Technology Press, 1996. (0) |
[21] |
LIANG Lifu, SHI Zhifei. On the inverse problem in calculus of variations[J]. Applied mathematics and mechanics, 1994, 15(9): 815-830. DOI:10.1007/BF02451631 (0)
|
[22] |
LIANG Lifu, HU Haichang. Generalized variational principle of three kinds of variables in general mechanics[J]. Science in China(A), 2001, 44(6): 770-776. (0)
|
[23] |
梁立孚. 变分原理及其应用[M]. 哈尔滨: 哈尔滨工程大学出版社, 2005. LIANG Lifu. Variational principles and their applications[M]. Harbin: Harbin Engineering University Press, 2005. (0) |
[24] |
陈滨. 分析动力学[M]. 2版. 北京: 北京大学出版社, 2010. CHEN Bin. Analytical mechanics[M]. 2 ed. Beijing: Peking University Press, 2010. (0) |
[25] |
梅凤翔. 分析力学[M]. 北京: 北京理工大学出版社, 2013. MEI Fengxiang. Analytical mechanics[M]. Beijing: Beijing Institute of Technology Press, 2013. (0) |