Segment V5.3: Smokestack Plume Momentum

(Related to Textbook Section 5.2.2 - Application of the Linear Momentum Equation)

A change in the momentum of a fluid (such as a change in speed or direction of flow) requires a non-zero resultant force.

The exhaust gas flowing within a smokestack has vertical momentum only. As the fluid leaves the stack it interacts with the horizontal wind. This interaction produces a non-zero force on the exhaust gas and causes it to develop a horizontal motion. In addition, the vertical momentum is lost to the surrounding air and the exhaust gas eventually flows along with the wind.