📂Fluid Mechanics

Fluid Velocity and Steady Flow

Definition ^{1 2}

In fluid mechanics, a fluid has no definite shape and its detailed state of motion is difficult to determine, so one posits entities such as a fluid particle.

1. The motion of a fluid is called flow.
2. The distance a fluid particle travels per unit time is called the flow velocity.
3. If all fluid particles passing through a point have the same flow velocity, that flow is called steady flow.
4. The path of a fluid particle in a steady flow is called a streamline.

Explanation

In fluid mechanics one typically treats, in theory, an infinite number of particles, and which particular fluid particle occupies a given position is not of primary importance. Instead, interest focuses on the state of motion of the fluid passing through a specific location; naturally, the object of analysis in fluid mechanics begins with the flow velocity rather than the position.

A fluid system’s steady state usually means a state in which every point has converged to steady flow, and it can be regarded as analogous to a fixed point of a dynamical system. In particular, studies of heat or mass transfer by fluids predominantly analyze the system in the steady state.