Drag Force

Drag Force Formula
$F_d \;=\; \dfrac{ \rho \cdot v^2 \cdot C_d \cdot A_c }{ 2 }$ (Drag Force) $\rho \;=\; \dfrac{ 2 \cdot d }{ v^2 \cdot C_d \cdot A_c }$ $v \;=\; \sqrt{ \dfrac{ 2 \cdot d }{ \rho \cdot C_d \cdot A_c } }$ $C_d \;=\; \dfrac{ 2 \cdot d }{ \rho \cdot v^2 \cdot A_c }$ $A_c \;=\; \dfrac{ 2 \cdot d }{ \rho \cdot v^2 \cdot C_d }$
Symbol	English	Metric
$F_d$ = Drag Force	$lbf$	$N$
$\rho$ (Greek symbol rho) = Fluid Density	$lbm \;/\; ft^3$	$kg \;/\; m^3$
$v$ = Fluid Velocity	$ft \;/\; sec$	$m \;/\; s$
$C_d$ = Drag Coefficient	$dimensionless$	$dimensionless$
$A_c$ = Area Cross-section Perpendicular to Flow	$ft^2$	$m^2$

Drag force, abbreviated as $F_d$ , is a resistive force that acts on an object moving through a fluid (gas or liquid). It is the force exerted perpendicular to the reference area and in opposition to the direction of travel. The reference area is the frontal area of the body that is perpendicular to the flow direction. Drag force opposes the motion of the object and is caused by the interaction between the object and the surrounding fluid. When an object moves through a fluid, it experiences drag due to two main factors: viscous drag and pressure drag. The total drag force experienced by an object is a combination of the viscous drag and pressure drag. It is typically modeled using equations like the drag equation, which relates the drag force to the fluid density, object's surface area, drag coefficient, and velocity of the object.

Understanding drag force is crucial in various applications, including aerodynamics, hydrodynamics, and vehicle design. Minimizing drag is often desired to reduce energy consumption, improve efficiency, and enhance performance in areas such as aerospace, automotive engineering, and sports. Methods for reducing drag include streamlining the object's shape, reducing surface roughness, employing aerodynamic or hydrodynamic design principles, and utilizing various techniques like boundary layer control or the addition of streamlined fairings.

Drag Force Types

Parasitic Drag - This type of drag does not contribute to lift (in the case of aircraft) and is generally undesirable.
- Form Drag (Pressure Drag) - Caused by the pressure differences created as the fluid flows around the object's shape. It's determined by the object's cross-sectional shape and area.
- Skin Friction Drag (Viscous Drag) - Caused by friction between the fluid and the surface of the object. This is influenced by surface roughness and the fluid's viscosity.
- Interference Drag - Occurs when different airflows over various parts of an object (wing and fuselage junction) interact and create additional drag.
Induced Drag (Lift-Induced Drag): - This type of drag is generated as a byproduct of producing lift (in aircraft wings). It's related to the vortices created at the wingtips due to pressure differences. Induced drag decreases as speed increases.
Wave Drag - Occurs at high speeds (transonic and supersonic) when shockwaves form around the object, leading to a sudden and significant increase in drag.

Drag Force

Drag Force Formula

Similar Articles

Latest Articles