Building Blocks for Fluid Systems
Chambers
 Chambers connect elements.
 Each element has an upstream and downstream chamber.
 Hold Pressure, Temperature, Velocity
 Boundary Chambers have known P, T, V
 NonBoundary (Internal) have solved P, T, V
 Solver convergence based on mass flow continuity at the internal chambers.
 Chamber Types : Plenum, Momentum, Inertial, Vortex, Elevation, Wind Bc
Frame 
Swirl Values (VEL_Air / VEL_metal) 
Comments  
Plenum 
Relative  0 or 1, (stationary or “onboard” rotating part) 

Momentum  Relative  0 or 1, (stationary or “onboard” rotating part) 

Elevation  Absolute  0 (always use on stationary) 

Inertial  Absolute  Any 

Vortex  Absolute  Any 

Plenum Chamber
 Variables: Static Pressure, Total Temperature (Absolute or Relative), Fluid Type
 Uses:
 Where velocity = 0 such as a large tank or cavity.
 Usually stationary parts
Momentum Chamber
 Variables: Static Pressure and Total Pressure (Absolute or Relative), or Mach Number, Total Temperature (Absolute or Relative), Fluid Type
 Can enter 2 out of these 3 items: Static Pressure, Total Pressure, Mach number. 3rd item is calculated
 Uses:
 Where velocity (fluid momentum) is passed from upstream to downstream elements
 Usually stationary or inside of rotating parts
Angles:
 Element orientation is critical to correct modeling when using momentum and inertial chambers.
 The relative angle difference between elements determines how much dynamic head is passed through the chamber to the downstream element.
Affects the source pressure that forces air through the downstream element. If elements are aligned the source pressure = total pressure. If elements are not aligned the source pressure < total pressure. If elements are 90 deg. different angles source pressure = static pressure.
 Input found under Advanced Options in most element panels.
Elevation Chamber
 Variables: Height, Static and Total Pressure or Mach Number, Total Temperature, Fluid Type
 Uses:
 Where there are significant changes in elevation that affect the pressure
 Stationary Parts
 Usually Incompressible Liquid
Inertial Chamber
 Variables: Static and Total Pressure or Mach Number, Total Temperature, Swirl, Fluid Type
 Can enter 2 out of these 3 items: Static Pressure, Total Pressure, Mach number. 3rd item is calculated
 Uses:
 Usually cavities in rotating models.
Vortex Chamber
 Variables: Static and Total Pressure or Mach Number, Total Temperature, Swirl, Fluid Type
 Can enter 2 out of these 3 items: Static Pressure, Total Pressure, Mach number. 3rd item is calculated
 Only chamber that is not attached to the end of elements.
 Cannot be a boundary
 Uses:
 Vortex elements and cavities in rotating models.
Elements & Components Overview
 Represents a flow path between one chamber and another
 Many different element types and subtypes are used to represent a flow circuit using the correct flow characteristics for a given feature – ranging from simple restrictions like tubes and orifices, to complex restrictions such as valves and seals.
 Grouped into both compressible (gas) elements and incompressible (liquid) elements.
 Flow rates and derivatives are calculated iteratively by passing through each element typespecific subroutine until mass continuity is achieved across all internal chambers.
 Most elements are restrictions. Flow rate is calculated based on the pressure drop from the upstream chamber to the downstream chamber.
 Some elements are pressure rise elements such as pumps and fans.
Restriction Elements
Orifices and generic losses
 Variables: CrossSectional Geometry and Losses
 Losses: Cd, Kloss. Constant or variable.
 Should be used for restrictions that do not have large L/D
 Uses:
 Generaluse element type
The CDCOMP subtype will calculate the loss but the other types require the user to enter a Cd or K.
Orifice Plates
 Variables: Orifice CrossSectional Geometry, Pipe Diameter
 Uses:
 Calculating loss for an orifice plate in a pipe/tube.
 Loss correlations based on circular holes in a circular pipe.
Tubes / pipes
 Variables: Diameter, Length, Number of Stations, Surface Roughness
 Include laminar and turbulent friction , rotation, and heat transfer effects
 Uses:
 Restrictions with large L/D where frictional effects would play a large role
 The tube elements solve the following equation at each segment of the tube.
 Subsonic Compressible
 Incompressible
 The tube element converges each outer iteration when the velocity (mass flow) used in the equations above allow the pressures at the first and last tube station to match the pressures in the upstream and downstream chambers.
Bends
 Variables: Bend Angle, Bend Radius, CrossSectional Geometry, Roughness
 Can model a variety of different bend geometries (see subtypes)
 Uses:
 Connect 2 tubes/pipes
 A more robust modeling of bends, including more loss data available that those included with the tube element type.
Junctions
 Variables: Arm Angle, Principle Diameter, Minor Diameter
 T Junction has straight through pipe with a side branch
 YJunction has a principle pipe with two minor branches
 Uses:
 Connect 3 tubes/pipes
 Models flow splits or unions, specifically to include a loss model
Expansions / Contractions
 Variables: Inlet / Exit CrossSectional Geometry
 Can use a variety of different expansion or contraction models
 Uses:
 Models either gradual (conical) or stepped (abrupt) changes in crosssectional geometry
Flow Elements
 Variables: Flowrate, Reference Flow, Reference Pressure Parameter
 Uses:
 Specify predefined flowrate either outright, or based on pressure parameter, or reference flows (combo flow)
Valves
 Variables: Momentum Loss Curve, CrossSectional Geometry, Valve Position
 Utilizes built in empirical loss data or user supplied loss data.
 Uses:
 Either for control or check valves

Seals
 Compressible Flow
 Uses:
 Calculates loss from a range of different types of seal configurations common in gas turbines.
Bearings
 Variables: Rotation Speed, Normal Force, Bearing Diameter & Width, Relative Clearance
 Can choose whether to include heating from friction
 Uses:
 To simulate steadily loaded journal bearing, determining flow rate (and optionally, heating)
Heat exchanger
 Uses a lumped eNTU method to calculate heat transfer between to fluid streams.
 Behaves like a chamber with 4 element attachment points.
NACA Scoop
 Variables: Geometry
 Bring external airflow of high velocity into a cavity with minimal pressure loss.
 Uses: Nacelles
Pressure Rise Elements
Centrifugal Pump
 Incompressible liquids only
 Requires a Pump Characteristic curve.
 The point where the derived pressure loss flow rate curve intersects the pump curve defines the operating point of the system.
Positive displacement Pump
 Incompressible liquids only.
 Positive displacement pump behaves like a Fixed Flow element where the flow gets calculated from volumetric displacement provided by manufacturer for the specific pump
Fans and Compressors
 Compressible gas only.
 The user needs to provide performance data for a machine that is dimensionally
similar to the one they wish to simulate, but which may differ in:
 Operating conditions (Temperature & Pressure)
 Gas Properties (i.e. Inlet Density)
 Rotational Speed
 Impeller Diameter
Transient Flow Analysis Items
Accumulators & Tanks
 Variables: Volume, Inlet/Outlet Geometry, Inlet/Outlet Loss, Fluid Type
 Actually a ‘Component’, behaves like chamber in terms of connectivity (used up or downstream of an element)
 Uses:
 Control volumes (such as tanks) that are either filling / emptying (or both)
Cylinders
 Variables: Diameter, Max Rod Displacement, Piston and Rod Mass, Initial Position and Velocity
 Can optionally include friction and damping effects
 Uses:
 Modeling of either a onesided or twosided piston in cylinder
Rotating Model Building blocks
Vortex elements
 Used to model rotating flow fields that do not have a significant flow restriction.
 Calculates pressure and temperature changes due to rotating flow.
 Uses:
 Rotating machinery such as gas turbines
Cavities
 Not an element or chamber
 Used to model rotating flow fields
 Uses angular momentum balance to calculate fluid swirl.
 Fluid swirl is used in vortex elements.
 Uses:
 Rotating machinery such as gas turbines
Combustion modelling
 Heat increase due to combustion using NASA CEA
 Fuel (reactants) and Air (oxidizer) tracked through network
 Fuel Source adds fuel to the network
 CEA Combustion Element
 Uses CEA to increase gas T
 Decrease Pressure due to heat addition
 Use series of elements for incomplete (rich) combustion upstream
Controllers
 Controllers are used to change chamber and element inputs while the solver is
running.
 Example: Change a valve position based on chamber pressure
 Controllers use “Gauge” variables to “Manipulate” the chamber or element
inputs.
 Example: Gauge variable = chamber pressure and Manipulate variable = valve position
 3 types of controllers
 PID Controller: Use PID logic to determine element variable value based on solution from another entity
 Mission BC Controller: Defines timedependent variations of a variable
 Feed Forward Controller: Change element variable based on solution from another entity
Thermal Network Items
Thermal network entities are typically used to model;
 heat flow through solids, liquids or gases,
 heat flow from a surface to another surface via electromagnetic waves
 heat flow applied directly at a point
Flow Simulator enables to integrate thermal resistances of conduction, convection and radiation, and direct heat application either as a standalone network or as a thermal network coupled with flow network to generate combined results. Moreover, SteadyState and Transient analyses are available for both options.