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FlowState

The FlowState class is a frozen dataclass representing a complete compressible flow state.

Overview

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from flow_state import FlowState

FlowState objects are returned by all solver functions. They are immutable (frozen) to ensure consistency of the computed properties.

Class Definition

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class FlowState:
    """Frozen dataclass representing a complete flow state."""
    # static conditions
    pres: float           # Static pressure [Pa]
    temp: float           # Static temperature [K]
    dens: float           # Density [kg/m^3]
    a: float              # Speed of sound [m/s]

    # flow kinematics
    mach: float           # Mach number [-]
    uvel: float           # Velocity [m/s]

    # transport
    mu: float       # Dynamic viscosity [Pa-s]
    nu: float       # Kinematic viscosity [m^2/s]
    re1: float            # Unit Reynolds number [1/m]

    # gas properties
    gamma: float          # Ratio of specific heats [-]
    r_gas: float          # Specific gas constant [J/(kg-K)]

    # stagnation conditions
    pres_stag: float      # Stagnation pressure [Pa]
    temp_stag: float      # Stagnation temperature [K]
    dens_stag: float      # Stagnation density [kg/m^3]

    # metadata
    altitude: float | None = None
    atmosphere_model: str | None = None

Properties

Static Conditions

Property Type Description
pres float Static pressure [Pa]
temp float Static temperature [K]
dens float Density [kg/m^3]
a float Speed of sound [m/s]

Flow Kinematics

Property Type Description
mach float Mach number
uvel float Velocity [m/s]

Transport Properties

Property Type Description
mu float Dynamic viscosity [Pa-s]
nu float Kinematic viscosity [m^2/s]
re1 float Unit Reynolds number [1/m]

Stagnation Conditions

Property Type Description
pres_stag float Stagnation pressure [Pa]
temp_stag float Stagnation temperature [K]
dens_stag float Stagnation density [kg/m^3]

Gas Properties

Property Type Description
gamma float Ratio of specific heats
r_gas float Specific gas constant [J/(kg-K)]

Metadata

Property Type Description
altitude float \| None Altitude [m], if computed from atmosphere
atmosphere_model str \| None Name of atmosphere model used

Methods

__str__

Returns a formatted summary table of all flow properties.

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state = solve(mach=7.0, pres=1000.0, temp=200.0)
print(state)

__repr__

Returns a concise representation for debugging.

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state = solve(mach=7.0, pres=1000.0, temp=200.0)
repr(state)  # FlowState(M=7.00, p=1000.0 Pa, T=200.0 K)

Example

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from flow_state import solve

state = solve(mach=7.0, altitude=30_000, atm="ussa76")

# Access individual properties
print(f"Mach: {state.mach}")
print(f"Velocity: {state.uvel:.1f} m/s")
print(f"Unit Reynolds: {state.re1:.2e} /m")
print(f"Stagnation temperature: {state.temp_stag:.1f} K")