CV_CHAR_EQ_PERC

Computes the normalized equal-percentage valve characteristic as a function of fractional opening.

Equal-percentage valves provide a near-constant percentage change in flow coefficient for equal increments in stem travel, producing a highly nonlinear characteristic.

The returned value is a dimensionless normalized coefficient fraction between approximately 0 and 1 over the practical opening range.

Excel Usage

=CV_CHAR_EQ_PERC(opening)

• opening (float, required): Fractional opening of the valve [0-1].

Returns (float): Flow coefficient characteristic fraction [0-1].

Example 1: Zero opening

Inputs:

opening
0

Excel formula:

=CV_CHAR_EQ_PERC(0)

Expected output:

1.35226e-19

Example 2: Full opening

Inputs:

opening
1

Excel formula:

=CV_CHAR_EQ_PERC(1)

Expected output:

1

Example 3: Half opening

Inputs:

opening
0.5

Excel formula:

=CV_CHAR_EQ_PERC(0.5)

Expected output:

0.163588

Example 4: Large opening (0.9)

Inputs:

opening
0.9

Excel formula:

=CV_CHAR_EQ_PERC(0.9)

Expected output:

0.859939

Python Code

Show Code

from fluids.control_valve import Cv_char_equal_percentage

def cv_char_eq_perc(opening):
    """
    Calculates the flow coefficient characteristic for an equal percentage control valve.

    See: https://fluids.readthedocs.io/fluids.control_valve.html#fluids.control_valve.Cv_char_equal_percentage

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

    Args:
        opening (float): Fractional opening of the valve [0-1].

    Returns:
        float: Flow coefficient characteristic fraction [0-1].
    """
    try:
      val = float(opening)
      if val < 0 or val > 1:
        return "Error: opening must be between 0 and 1"
      return float(Cv_char_equal_percentage(val))
    except Exception as e:
      return f"Error: {str(e)}"

Online Calculator

opening *

Fractional opening of the valve [0-1].