Fluid Mechanics Flashcards

The Moody diagram relates the Darcy friction factor to:

Answer: Reynolds number and relative pipe roughness

The Moody diagram provides friction factor f as a function of Reynolds number Re and relative roughness ε/D.

For an ideal (inviscid, incompressible) fluid, Bernoulli's equation assumes which condition along a streamline?

Answer: Steady, incompressible, inviscid flow with no shaft work

Bernoulli's equation applies along a streamline for steady, incompressible, inviscid flow with no external work done.

Which non-dimensional parameter characterizes the ratio of buoyancy forces to viscous forces in natural convection flows?

Answer: Grashof number

The Grashof number (Gr = gβΔTL³/ν²) represents buoyancy to viscous force ratio in natural convection.

A hydraulic jump occurs in open channel flow when the flow transitions from:

Answer: Supercritical to subcritical

A hydraulic jump is an abrupt transition from supercritical (Fr > 1) to subcritical (Fr < 1) flow with significant energy loss.

The stream function ψ is defined such that lines of constant ψ represent:

Answer: Streamlines of the flow

The stream function ψ is defined so that ∂ψ/∂y = u and ∂ψ/∂x = −v, making iso-ψ lines identical to streamlines.

Minor losses in pipe systems (bends, fittings, valves) are commonly expressed as:

Answer: h_m = K(V²/2g) where K is a loss coefficient

Minor losses are expressed as h_m = K·V²/(2g), where K is the dimensionless loss coefficient specific to each fitting.

In a centrifugal pump, the specific speed Ns is used to:

Answer: Classify pump geometry and select the optimal impeller type

Specific speed classifies pump geometry: low Ns favors radial-flow (centrifugal) designs, high Ns favors axial-flow designs.