IS_CHOKED_FLOW

Overview

Determine if a flow is choked (critical) based on pressure ratio.

Excel Usage

=IS_CHOKED_FLOW(p_upstream, p_downstream, k_isentropic)

• p_upstream (float, required): Higher, source pressure [Pa]
• p_downstream (float, required): Lower, downstream pressure [Pa]
• k_isentropic (float, required): Isentropic exponent [-]

Returns (bool): True if flow is choked (critical), False otherwise

Examples

Example 1: API 520 Example 1 - not choked

Inputs:

p_upstream	p_downstream	k_isentropic
670000	532000	1.11

Excel formula:

=IS_CHOKED_FLOW(670000, 532000, 1.11)

Expected output:

false

Example 2: API 520 Example 2 - choked flow

Inputs:

p_upstream	p_downstream	k_isentropic
670000	101000	1.11

Excel formula:

=IS_CHOKED_FLOW(670000, 101000, 1.11)

Expected output:

true

Example 3: Near critical pressure ratio

Inputs:

p_upstream	p_downstream	k_isentropic
1000000	500000	1.4

Excel formula:

=IS_CHOKED_FLOW(1000000, 500000, 1.4)

Expected output:

true

Example 4: High pressure ratio - definitely choked

Inputs:

p_upstream	p_downstream	k_isentropic
5000000	100000	1.4

Excel formula:

=IS_CHOKED_FLOW(5000000, 100000, 1.4)

Expected output:

true

Python Code

import micropip
await micropip.install(["fluids"])
from fluids.compressible import is_critical_flow as fluids_is_crit

def is_choked_flow(p_upstream, p_downstream, k_isentropic):
    """
    Determine if a flow is choked (critical) based on pressure ratio.

    See: https://fluids.readthedocs.io/fluids.compressible.html#fluids.compressible.is_critical_flow

    This example function is provided as-is without any representation of accuracy.

    Args:
        p_upstream (float): Higher, source pressure [Pa]
        p_downstream (float): Lower, downstream pressure [Pa]
        k_isentropic (float): Isentropic exponent [-]

    Returns:
        bool: True if flow is choked (critical), False otherwise
    """
    # Validate and convert inputs
    try:
        p_upstream = float(p_upstream)
    except (ValueError, TypeError):
        return "Invalid input: p_upstream must be a number."

    try:
        p_downstream = float(p_downstream)
    except (ValueError, TypeError):
        return "Invalid input: p_downstream must be a number."

    try:
        k_isentropic = float(k_isentropic)
    except (ValueError, TypeError):
        return "Invalid input: k_isentropic must be a number."

    # Validation
    if p_upstream <= 0:
        return "Invalid input: p_upstream must be positive."
    if p_downstream < 0:
        return "Invalid input: p_downstream must be non-negative."
    if k_isentropic <= 1:
        return "Invalid input: k_isentropic must be greater than 1."
    if p_downstream >= p_upstream:
        return "Invalid input: p_downstream must be less than p_upstream."

    try:
        result = fluids_is_crit(P1=p_upstream, P2=p_downstream, k=k_isentropic)
        return bool(result)
    except Exception as e:
        return f"Error: Failed to compute critical flow check: {str(e)}"

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