DRAG

Overview

The DRAG function calculates the drag coefficient ($C_D$) for an object moving through a fluid. The drag coefficient is a dimensionless number that quantifies the drag or resistance of an object in a fluid environment, such as air or water. It is essential in fluid dynamics, aerodynamics, and engineering applications to estimate the force required to move an object through a fluid. The drag coefficient is calculated using the following equation:

where:

• $F$ is the drag force (N)
• $A$ is the projected area (m²)
• $\rho$ is the fluid density (kg/m³)
• $V$ is the velocity (m/s)

For more information, see the fluids GitHub repository  and the official documentation .

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

Usage

To use the function in Excel:

=DRAG(F, A, V, rho)

• F (float, required): Drag force in Newtons (N).
• A (float, required): Projected area in square meters (m²).
• V (float, required): Velocity in meters per second (m/s).
• rho (float, required): Fluid density in kilograms per cubic meter (kg/m³).

The function returns a single value (float): the drag coefficient (dimensionless), or an error message (string) if the input is invalid or out-of-range.

Examples

Example 1: Calculate Drag Coefficient for a Small Object

In Excel:

=DRAG(1000, 0.0001, 5, 2000)

Expected output:

Example 2: Calculate Drag Coefficient for a Large Object

In Excel:

=DRAG(500, 0.05, 10, 1000)

Expected output:

Example 3: Calculate Drag Coefficient for a Medium Object

In Excel:

=DRAG(250, 0.02, 8, 900)

Expected output:

Example 4: Calculate Drag Coefficient for a Low-Density Fluid

In Excel:

=DRAG(120, 0.01, 15, 1.2)

Expected output:

Python Code

import micropip
await micropip.install('fluids')
from fluids.core import Drag as fluids_drag
 
def drag(F, A, V, rho):
    """
    Calculate the drag coefficient (dimensionless) for an object in a fluid.
 
    Args:
        F: Drag force in Newtons (N).
        A: Projected area in square meters (m²).
        V: Velocity in meters per second (m/s).
        rho: Fluid density in kilograms per cubic meter (kg/m³).
 
    Returns:
        The drag coefficient (float), or an error message (str) if the input is invalid or out-of-range.
 
    This example function is provided as-is without any representation of accuracy.
    """
    try:
        F_val = float(F)
        A_val = float(A)
        V_val = float(V)
        rho_val = float(rho)
    except Exception:
        return "Invalid input: could not convert arguments to float."
    if A_val <= 0 or V_val <= 0 or rho_val <= 0:
        return "Invalid input: area, velocity, and density must be positive."
    try:
        result = fluids_drag(F_val, A_val, V_val, rho_val)
    except Exception as e:
        return f"Error: {str(e)}"
    return round(result, 3)

Live Notebook

Edit this function in a live notebook .

Live Demo