View source for Meco Simulation Model and Component Graph

The Meco Rocket Simulator represents complex rocket engine systems through an interconnected component graph that models both liquid propellant flows and gas dynamics. This document explains how the simulation model works and how the component graph captures the physical relationships between different parts of the rocket engine system.

For a detailed overview of all available components, see the '''[[Meco Rocket Simulator Components|Component Overview]]''' page.

== Model Architecture Overview ==

The simulation model is built around a **directed graph topology** where:
* '''[[Meco Nodes|Nodes]]''' represent physical junction points and boundary conditions in the system
* '''[[Meco Branches|Branches]]''' represent flow paths connecting nodes (pipes, ducts, valves)
* '''[[Meco Machinery|Components]]''' represent active elements that add or extract energy (pumps, turbines)
* '''[[Meco Control Parameters|Control Parameters]]''' provide dynamic system control and time-varying inputs

This graph-based approach allows the simulator to model complex flow networks with multiple interconnected paths, branching flows, and coupled subsystems.

== Dual Flow Network Architecture ==

The simulation model handles two distinct but interconnected flow networks:

=== Liquid Flow Networks ===

The liquid flow network models incompressible fluid flow through the propellant feed system:

'''Network Topology:'''
* Liquid nodes serve as connection points and boundary conditions
* Branches model pipes, cooling channels, and valves with viscous flow effects
* Flow is governed by mass conservation and momentum equations
* Pressure-driven flow with friction and fitting losses

'''Physical Modeling:'''
* Turbulent and laminar flow regimes based on Reynolds numbers
* Complex duct geometries (circular, rectangular, annular)
* Multiple parallel cooling channels with volume factors
* Pump work addition through machinery components

'''Key Components:'''
* '''[[Meco Nodes|NodeInlet/NodeOutlet]]''': Boundary conditions with controlled pressures
* '''[[Meco Nodes|NodeInternal]]''': Internal junction points with pressure dynamics
* '''[[Meco Branches|Branch]]''': Flow connections with friction models and fitting losses
* '''[[Meco Machinery|MachineryPump]]''': Centrifugal pumps adding energy to liquid flow

=== Gas Flow Networks ===

The gas flow network models compressible flow through the combustion and exhaust systems:

'''Network Topology:'''
* Gas nodes handle internal junctions and boundary conditions
* Gas branches model high-speed compressible flow with choking effects
* Flow governed by conservation of mass, momentum, and energy
* Isentropic flow relations with friction and heat transfer

'''Physical Modeling:'''
* Subsonic and supersonic flow regimes with Mach number tracking
* Critical flow conditions and sonic choking at throats
* Fanno flow with friction effects in ducts
* Temperature and pressure ratio calculations

'''Key Components:'''
* '''[[Meco Nodes|NodeGasInternal]]''': Internal gas junctions with pressure dynamics
* '''[[Meco Nodes|NodeGasGenerator]]''': Combustion chambers mixing oxidizer and fuel
* '''[[Meco Branches|BranchGas]]''': Compressible flow connections with Mach number evolution
* '''[[Meco Machinery|MachineryTurbine]]''': Gas turbines extracting energy from hot gas flow

== Network Interaction and Coupling ==

The liquid and gas networks interact through several critical coupling mechanisms:

=== Combustion Coupling ===

The '''[[Meco Nodes|NodeGasGenerator]]''' serves as the primary coupling point between liquid and gas networks:

* '''Liquid Inputs''': Separate oxidizer and fuel liquid streams enter the gas generator
* '''Mixing and Combustion''': Liquid propellants mix and combust according to equilibrium chemistry
* '''Gas Output''': High-temperature, high-pressure combustion products exit as gas flow
* '''Property Calculation''': Gas properties (temperature, density, specific heat ratio) computed from oxidizer-fuel ratio and pressure

=== Heat Transfer Coupling ===

'''[[Meco Solids|Solid]]''' components provide thermal coupling between gas and liquid networks:

* '''Gas-Side Heat Transfer''': Hot combustion gases transfer heat to chamber walls
* '''Liquid-Side Cooling''': Cold liquid propellant flows through cooling channels
* '''Thermal Conduction''': Heat conducts through solid material between gas and liquid sides
* '''Regenerative Cooling''': Liquid propellant preheated before injection, improving performance

=== Control System Coupling ===

Dynamic control parameters coordinate between networks:

* '''Valve Control''': Coordinated liquid and gas valve positions
* '''Pressure Control''': Boundary pressure control affecting both networks
* '''Turbopump Coupling''': Gas turbine drives liquid pumps through shaft connections

== Fluid Property Propagation ==

The simulation uses a sophisticated fluid inheritance system to maintain consistent properties throughout each network:

=== Liquid Property Inheritance ===

* '''Boundary Definition''': Liquid properties defined at inlet boundary nodes
* '''Forward Propagation''': Properties inherited downstream through branches and nodes
* '''Molecular Identity''': Each liquid stream maintains its molecular identity (O2, H2, etc.)
* '''Temperature Evolution''': Liquid temperature changes due to pumping and heat transfer

=== Gas Property Evolution ===

* '''Combustion Products''': Gas properties calculated from chemical equilibrium
* '''Dynamic Properties''': Temperature, pressure, and composition evolve through network
* '''Isentropic Relations''': Property changes follow thermodynamic relations
* '''Flow-Dependent Properties''': Mach number and flow regime affect local properties

== Network Solving Strategy ==

The simulation employs different numerical strategies for each network type:

=== Liquid Network Solution ===

* '''Differential Equations''': Mass conservation and momentum balance equations
* '''Pressure Dynamics''': Node pressures evolve based on mass flow imbalances
* '''Friction Modeling''': Darcy-Weisbach friction with automatic Reynolds number calculation
* '''Pump Modeling''': Performance curves relating head rise to flow rate

=== Gas Network Solution ===

* '''Iterative Solution''': Mass flow and pressure distribution solved iteratively
* '''Finite Difference''': Jacobian matrix computed using finite differences
* '''Mach Number Tracking''': Flow regime detection and sonic choking handling
* '''Energy Balance''': Temperature mixing at junction points

== Component Graph Benefits ==

The component graph representation provides several key advantages:

=== Modularity ===
* Components can be easily added, removed, or modified
* Complex systems built from simple, well-understood elements
* Reusable component library for different engine configurations

=== Physical Intuition ===
* Graph structure mirrors actual physical connections
* Engineers can visualize and understand system topology
* Debugging and validation easier with clear component relationships

=== Scalability ===
* Networks can range from simple test cases to full engine systems
* Multiple engines or stages can be represented in single model
* Component count limited only by computational resources

=== Flexibility ===
* Different component types can be connected as needed
* Control systems easily integrated throughout the model
* New component types can be added without changing core infrastructure

== Advanced Network Features ==

=== [[Meco Solids|Multiple Cooling Circuits]] ===
* Parallel cooling channels with different flow rates
* Series-parallel combinations for complex heat exchangers
* Volume factors to account for channel count and geometry

=== [[Meco Transmission|Transmission Systems]] ===
* Shaft connections between turbines and pumps
* Gear ratios and rotational dynamics
* Power transmission through multiple stages

=== [[Meco Branches|Valve Control]] ===
* Time-varying valve positions with smooth transitions
* Coordinated valve sequences for engine startup and shutdown
* Pressure relief and safety valve modeling

=== Boundary Condition Flexibility ===
* Time-varying pressure and temperature boundary conditions
* Mass flow rate specifications for complex operational profiles
* Ambient condition variations for altitude simulations

== Model Validation and Verification ==

The component graph approach enables comprehensive model validation:

=== Component-Level Testing ===
* Individual components validated against analytical solutions
* Benchmark cases for each component type
* Parametric studies to verify physical behavior

=== Network-Level Validation ===
* Simple network configurations compared to analytical solutions
* Progressive complexity building from validated simple cases
* Mass and energy conservation checks throughout solution process

=== System-Level Verification ===
* Full engine models compared to test data
* Transient behavior validation during startup and shutdown
* Performance parameter correlation with experimental measurements

== See Also ==

* '''Component Documentation:'''
** [[Meco Nodes|Node Components]] - Junction points and boundary conditions
** [[Meco Branches|Branch Components]] - Flow connections and piping
** [[Meco Machinery|Machinery Components]] - Pumps and turbines
** [[Meco Transmission|Transmission Components]] - Power transfer elements
** [[Meco Solids|Solid Components]] - Heat transfer modeling
** [[Meco Control Parameters|Control Parameters]] - Dynamic system control

* '''Technical References:'''
** Gas Network Theory and Fanno Flow Implementation
** Liquid Network Friction and Pump Modeling
** Chemical Equilibrium and Combustion Modeling
** Heat Transfer and Thermal Analysis

[[Category:Meco Simulation]]
[[Category:Rocket Engine Modeling]]
[[Category:Computational Fluid Dynamics]]
[[Category:Network Analysis]]
[[Category:Component Graphs]]