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ETC Hydraulics & Fluid Mechanics Flashcards

7 cards from real ETC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Manning's equation (V = (1/n) × R^(2/3) × S^(1/2)) is used primarily to calculate:

    Answer: Flow velocity in open channels and culverts

    Manning's equation calculates mean flow velocity in open channels using Manning's roughness coefficient n, hydraulic radius R, and channel slope S.

  2. The hydraulic radius (R) of an open channel cross-section is defined as:

    Answer: The ratio of flow area to wetted perimeter (A/P)

    Hydraulic radius R = A/P, where A is the cross-sectional area of flow and P is the wetted perimeter; it quantifies flow efficiency relative to boundary friction.

  3. A centrifugal pump transfers energy to a fluid primarily through:

    Answer: A rotating impeller that imparts kinetic energy converted to pressure

    A centrifugal pump's rotating impeller accelerates fluid radially outward, converting mechanical (shaft) energy to kinetic energy, which the volute casing then converts to pressure.

  4. The pump performance (head-capacity) curve shows the relationship between:

    Answer: Total dynamic head (TDH) and volumetric flow rate (Q)

    The head-capacity curve plots TDH vs. Q, showing that as flow rate increases, the head a centrifugal pump can deliver typically decreases.

  5. The Froude number in open channel flow is used to classify flow as:

    Answer: Subcritical or supercritical

    The Froude number Fr = V/√(gD); Fr 1 is supercritical (rapid) flow.

  6. Net Positive Suction Head Available (NPSHa) must always be:

    Answer: Greater than the pump's required NPSH (NPSHr) to prevent cavitation

    NPSHa must exceed NPSHr (typically by a safety margin of 1–2 m or per manufacturer guidance) to ensure local pressure stays above vapor pressure and prevent cavitation.

  7. The Hazen-Williams formula is most commonly used in water distribution design to estimate:

    Answer: Friction head loss in pressurized water pipes

    The Hazen-Williams formula calculates friction head loss in water supply pipes using an empirical roughness coefficient C, which ranges from ~80 (corroded old pipe) to 150 (smooth plastic).