咨询Modelica标准Fluid库是否支持壅塞流模拟（旋转爆震发动机场景）

Hey Thomas, great question—simulating choked flow in Rotating Detonation Engine (RDE) feed systems is no small feat, especially when dealing with non-design choke points like rough long pipes or converging nozzle throats. Let’s break down your options step by step:

First, let’s clarify what the standard Modelica.Fluid library can do:

• Core Compressible Flow Support: The library does include components for compressible flow (like Modelica.Fluid.Pipes.DynamicPipe or Modelica.Fluid.Nozzles.ConvergingNozzle) built on full compressible flow equations. However, this support isn’t always enabled by default—you’ll need to use a compressible medium model from Modelica.Media (e.g., real gas or high-pressure ideal gas models) and configure components to use flow models that account for Mach number limits.
• Non-Design Choke Points:
  • For converging nozzles, the ConvergingNozzle component does natively handle choked flow: it calculates Mach number at the throat, and switches to choked flow logic when the exit Mach number hits 1. This works well for intentional throat points.
  • For rough long pipes (choked due to friction), the standard library’s base pipe models are more limited. Most default pipe implementations use simplified friction models that assume subsonic flow. That said, some advanced pipe configurations (e.g., enabling friction-based compressible flow equations) can be tweaked to detect and handle friction-induced choking, though this requires diving into the component’s parameter settings and ensuring the medium model supports high-pressure, high-flow conditions.
• Key Limitation: The standard library treats compressible flow as a precision enhancement rather than a first-class feature for choking. You’ll likely need to manually verify that components are configured to trigger choke logic, and it may not handle edge cases (like mid-pipe choking from friction) out of the box.

If the standard library falls short, there are specialized libraries built explicitly for high-pressure, compressible, choked flow scenarios:

• ThermoPower: This library is tailored for thermal power systems and includes robust components for compressible flow, including pipes with friction-induced choking, nozzles, and valves. It natively handles choke logic for both design and non-design points, and it’s fully compatible with OpenModelica.
• NASA Glenn Modelica Library: Developed for aerospace applications, this library has components optimized for rocket propulsion systems. Its pipe and flow models explicitly account for high-speed, choked flow, making it a great fit for RDE feed systems.
• Custom Component Development: You mentioned you’re open to building new libraries—and this is totally feasible. The standard Modelica.Fluid framework provides a solid foundation for compressible flow equations. You can extend existing components (like DynamicPipe) by adding choke detection logic (e.g., monitoring local Mach number, switching to Fanno flow equations when Mach 1 is reached for friction-induced choking) or custom flow models for non-design points.

Short answer: Probably not, unless you need full 3D flow detail.

• Modelica’s strength lies in system-level modeling—perfect for your tank-to-engine pipeline system. Tools like ANSYS Fluent or OpenFOAM can handle 3D choked flow simulations, but they’re overkill for system-level analysis and require far more computational resources and setup time.
• If you do need to couple system-level modeling with 3D CFD for specific choke points, Modelica supports co-simulation via FMU (Functional Mock-up Unit) interfaces. This lets you use Modelica for the overall pipeline and a CFD tool for critical 3D regions.

1. Start with the standard Modelica.Fluid library: Configure compressible media, enable advanced flow models for pipes/nozzles, and test choke scenarios (especially for nozzles first).
2. If standard components don’t handle non-design chokes, import ThermoPower or NASA Glenn libraries—they have pre-built, validated components for your use case.
3. For fully custom needs, extend the standard library’s compressible flow components with choke logic. The base equations are already there; you just need to add the choke detection and state-switching logic.
4. Stick with Modelica unless you require high-fidelity 3D flow data—system-level modeling is exactly what you need for your RDE feed system.

内容的提问来源于stack exchange，提问作者Thomas