Engr Help

Terms for Different Forms of The Bernoulli Equation

In a Nutshell: The Bernoulli equation provides a convenient way to relate changes of pressure,

fluid speed, and gravitational attraction for fluid acceleration in a flow field. It applies to

different forms of fluid motion. The following table contains the definition of terms.

Term Meaning

Inviscid

All fluids support a shear stress to some extent. However, one model is to

assume that the shear stress in the fluid is negligible. In this case the

viscous effects are presumed negligible. i.e. the viscosity is zero

Steady or

Steady Flow

If the flow is steady, the flow is established and no fluid characteristics

change with time.

i.e. the pressure, fluid velocity, flow rate, etc do not change with

time at any given location.

Irrotational or

Irrotational Flow

The field of flow is said to be irrotational if the fluid particles

do not "spin" as they move. i.e. The rotational characteristic.

is termed, vorticity, and is zero for irrotational flow.

Vorticity relates to fluid particle rotation.

From a theoretical point of view, for a two-dimensional field

field of flow, the curl of the velocity vector equals the vorticity

and must be zero in irrotational flow.