OpenModelica中ClosedVolume与SweptVolume仿真报错及质量设置求助

我正在学习OpenModelica软件，尝试搭建一个由ClosedVolume、StaticPipe、SweptVolume及平动质量组件组成的简单模型，但运行仿真时出现错误，进程崩溃。错误信息显示：solveOneNonlinearEquation函数调用中u_min和u_max未包围非线性方程的根，fa与fb符号未相反。同时希望了解如何为ClosedVolume设置指定质量，特附上模型代码及错误信息如下：

模型代码 #

Modelica.Fluid.Machines.SweptVolume sweptVolume(redeclare package Medium = Modelica.Media.Air.SimpleAir, clearance = 0.0001, nPorts = 1, pistonCrossArea = 0.001) annotation(
    Placement(visible = true, transformation(origin = {18, 0}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
  Modelica.Fluid.Vessels.ClosedVolume volume(redeclare package Medium = Modelica.Media.Air.SimpleAir, V = 6e-4, nPorts = 1, use_portsData = false) annotation(
    Placement(visible = true, transformation(origin = {-66, 20}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  inner Modelica.Fluid.System system annotation(
    Placement(visible = true, transformation(origin = {-82, 80}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Fluid.Pipes.StaticPipe pipe(redeclare package Medium = Modelica.Media.Air.SimpleAir, diameter = 0.8, length = 1, nParallel = 1) annotation(
    Placement(visible = true, transformation(origin = {-28, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Mechanics.Translational.Components.Mass mass(m = 0.1) annotation(
    Placement(visible = true, transformation(origin = {54, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
equation
  connect(volume.ports[1], pipe.port_a) annotation(
    Line(points = {{-66, 10}, {-66, 0}, {-38, 0}}, color = {0, 127, 255}));
  connect(pipe.port_b, sweptVolume.ports[1]) annotation(
    Line(points = {{-18, 0}, {8, 0}}, color = {0, 127, 255}));
  connect(sweptVolume.flange, mass.flange_a) annotation(
    Line(points = {{28, 0}, {44, 0}}, color = {0, 127, 0}));
  annotation(
end ClosedSwept; 

错误信息 #

The arguments u_min and u_max provided in the function call     solveOneNonlinearEquation(f,u_min,u_max) do not bracket the root of the single non-linear equation 0=f(u):   u_min  = 200   u_max  = 6000   fa = f(u_min) = 212529   fb = f(u_max) = 7.66508e+06 fa and fb must have opposite sign which is not the case
Process crashed Simulation process failed. Exited with code 0xffffffffc0000005.

这个错误源于求解器无法找到非线性方程的根，核心原因是模型初始条件或参数设置不合理，可按以下步骤调整：

• 修正组件初始条件
  • 给ClosedVolume手动设置合理的初始压力和温度，比如标准大气压和室温：

    Modelica.Fluid.Vessels.ClosedVolume volume(
      redeclare package Medium = Modelica.Media.Air.SimpleAir,
      V = 6e-4,
      nPorts = 1,
      use_portsData = false,
      p_start=101325,
      T_start=293.15
    );
    

  • 给SweptVolume设置合理的初始活塞位置，避免初始体积与clearance冲突：

    Modelica.Fluid.Machines.SweptVolume sweptVolume(
      redeclare package Medium = Modelica.Media.Air.SimpleAir,
      clearance = 0.0001,
      nPorts = 1,
      pistonCrossArea = 0.001,
      x_start=0.1
    );
    

• 调整管道参数
  当前StaticPipe直径0.8米，和其他组件（ClosedVolume体积6e-4 m³、活塞面积0.001 m²）尺寸差距过大，会导致流体状态异常。建议缩小管道直径，比如改成0.01米：

  Modelica.Fluid.Pipes.StaticPipe pipe(
    redeclare package Medium = Modelica.Media.Air.SimpleAir,
    diameter = 0.01,
    length = 1,
    nParallel = 1
  );
  

• 可选：调整求解器设置
  如果上述调整后仍有问题，可在仿真设置中切换非线性求解器（比如从默认的Newton法改为Broyden法），或增大迭代次数，但优先调整模型参数和初始条件。

ClosedVolume默认通过体积、初始压力/温度间接确定质量，要直接指定质量，有两种可行方式：

方式1：利用portsData初始化 #

设置use_portsData=true，结合理想气体状态方程反推初始压力/温度，来得到目标质量。示例：
假设目标质量为0.0007kg（标准状态下6e-4 m³空气的质量），修改ClosedVolume参数：

Modelica.Fluid.Vessels.ClosedVolume volume(
  redeclare package Medium = Modelica.Media.Air.SimpleAir,
  V = 6e-4,
  nPorts = 1,
  use_portsData = true,
  portsData = {Modelica.Fluid.Types.PortData(m_flow_start=0, p_start=101325, T_start=293.15)}
);

如果需要其他目标质量，可通过公式m = (p*V)/(R*T)（R为空气气体常数，取287 J/(kg·K)）反推对应的p或T值。

方式2：添加初始方程约束 #

在模型的initial equation部分直接指定ClosedVolume的介质质量，需确保参数兼容：

initial equation
  volume.medium.m = 0.0007; // 替换为你的目标质量值

注意：这种方式可能需要同时约束压力或温度，避免状态变量冲突，比如同时添加volume.medium.p = 101325;。

内容的提问来源于stack exchange，提问作者Emma