Meco Branches

Branches connect nodes and represent flow paths through the rocket engine system. They model pipes, ducts, valves, and other flow connections with detailed fluid dynamics.

Overview

The Meco Rocket Simulator supports 4 different branch types:

Branch Type	System	Controllable	Geometries	Fittings Support
Branch	Liquid	No	Circle, Rect, Annulus	Yes
BranchGas	Gas	No	Circle, Rect	No
BranchValve	Liquid	Yes	Circle only	Yes
BranchGasValve	Gas	Yes	Circle only	No

Common Parameters

All branches share these core parameters:

• name - Component name (string)
• node_i - Inlet node name (string)
• node_j - Outlet node name (string)
• length - Branch length in meters (double)
• roughness - Wall roughness in meters (double)
• n - Number of parallel branches (integer)

Geometry Types

Circle

• dimType: "Circle"
• Parameters:
  • dimA - Diameter in meters (double)

Rectangle

• dimType: "Rect"
• Parameters:
  • dimA - Width in meters (double)
  • dimB - Height in meters (double)

Annulus

• dimType: "Annulus"
• Parameters:
  • dimA - Outer diameter in meters (double)
  • dimB - Inner diameter in meters (double)

Branch Types

Branch (Liquid)

• Type: Branch
• Purpose: Standard liquid flow branch with optional fittings
• Supported Geometries: Circle, Rect, Annulus
• Additional Parameters:
  • fittings - Array of fitting types (optional)

Example JSON:

{
  "name": "LH HP Line",
  "category": 2,
  "type": "Branch",
  "dimType": "Circle",
  "dimA": 0.055,
  "length": 1.5,
  "node_i": "LH HP Joint",
  "node_j": "LH HP Junction",
  "roughness": 0.00003,
  "fittings": ["Elbow45", "Elbow90"],
  "n": 1
}

BranchGas

• Type: BranchGas
• Purpose: Gas flow branch (no fittings support)
• Supported Geometries: Circle, Rect (Annulus not supported)
• Limitations: No fittings support

Example JSON:

{
  "name": "TC Throat",
  "category": 2,
  "type": "BranchGas",
  "dimType": "Circle",
  "dimA": 0.127,
  "length": 0.038558466155904414,
  "node_i": "TC Throat Joint",
  "node_j": "TC Nozzle Joint",
  "roughness": 0.00003,
  "n": 1
}

BranchValve

• Type: BranchValve
• Purpose: Controllable valve for liquid systems
• Supported Geometries: Circle only
• Features: Supports fittings, controllable via control parameters

Example JSON:

{
  "name": "Main Valve",
  "category": 2,
  "type": "BranchValve",
  "dimType": "Circle",
  "dimA": 0.08,
  "length": 0.2,
  "node_i": "Manifold",
  "node_j": "Engine Inlet",
  "roughness": 0.00003,
  "fittings": ["ValveBall"],
  "n": 1
}

BranchGasValve

• Type: BranchGasValve
• Purpose: Controllable valve for gas systems
• Supported Geometries: Circle only
• Features: Controllable via control parameters, no fittings support

Example JSON:

{
  "name": "Gas Control Valve",
  "category": 2,
  "type": "BranchGasValve",
  "dimType": "Circle",
  "dimA": 0.05,
  "length": 0.1,
  "node_i": "Gas Manifold",
  "node_j": "Nozzle Inlet",
  "roughness": 0.00003,
  "n": 1
}

Supported Fittings

Available for Branch and BranchValve types:

Flow Obstructions

• TankBaffles - Tank internal baffles
• ValveBall - Ball valve
• ValveButterfly - Butterfly valve
• ValveCheckSwing - Swing check valve

Directional Changes

• Elbow90 - 90-degree elbow
• Elbow45 - 45-degree elbow
• Elbow180 - 180-degree return bend

Junctions

• TeeElbow - Tee with flow turning
• TeeFlowThrough - Straight-through tee

Fitting Usage Example:

"fittings": [
  "Elbow45",
  "Elbow90",
  "ValveBall",
  "TeeFlowThrough"
]

Design Guidelines

Flow Sizing

1. Size pipes for reasonable velocities (2-10 m/s for liquids, 50-200 m/s for gases)
2. Consider pressure drop through fittings and length
3. Use parallel branches (n > 1) for high flow rates

Geometry Selection

1. Circle: Most common, best for pressure applications
2. Rectangle: For compact installations, non-pressure applications
3. Annulus: For cooling channels, coaxial configurations

Roughness Values

1. Smooth pipes: 0.000015 m (15 microns)
2. Commercial steel: 0.000045 m (45 microns)
3. Cast iron: 0.00026 m (260 microns)
4. Concrete: 0.0015 m (1.5 mm)

Valve Control

1. Use BranchValve/BranchGasValve for controllable flow restrictions
2. Connect to Control Parameters for dynamic operation
3. Consider valve authority and rangeability in sizing

Common Applications

• Feed Lines: Connect tank outlets to pump inlets
• High Pressure Lines: Connect pump outlets to injectors
• Gas Lines: Connect gas generators to turbine inlets
• Cooling Channels: Use annular geometry for regenerative cooling
• Control Valves: Use valve types for throttling and shutoff
• Nozzles: Use gas branches for converging-diverging nozzle sections

Performance Considerations

• Fittings add significant pressure drop - use sparingly
• Multiple parallel branches (n > 1) reduce pressure drop
• Gas branches handle compressible flow with choking
• Valve branches enable dynamic flow control during simulation

See Also

• Main Components Overview
• Node Components
• Control Parameters
• Machinery Components
• Fluid Dynamics Reference
• Pipe Sizing Guidelines