Hydraulics and Fluid Mechanics Flashcards
7 cards from real ASCE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hydraulics and Fluid Mechanics flashcards as text
The specific weight of water (γ) at standard conditions (68°F/20°C) is approximately:
Answer: 62.4 lb/ft³ (9.81 kN/m³)
Water at standard conditions has a specific weight of approximately 62.4 lb/ft³ (9,810 N/m³ or 9.81 kN/m³), which is used extensively in hydrostatic pressure and buoyancy calculations.
The force exerted by a static fluid on a submerged flat surface acts at the:
Answer: Center of pressure, which is always at or below the centroid
The resultant hydrostatic force acts at the center of pressure, which is located at or below the centroid because pressure increases with depth, weighting the force distribution toward the lower portion of the surface.
The Moody diagram is used to determine which parameter in the Darcy-Weisbach equation?
Answer: The Darcy-Weisbach friction factor (f)
The Moody diagram relates the Darcy-Weisbach friction factor (f) to the Reynolds number and relative roughness (ε/D), enabling engineers to determine f for both laminar and turbulent pipe flow conditions.
In the design of a spillway, the discharge coefficient (Cd) is used to account for:
Answer: Hydraulic losses and velocity of approach effects on actual flow
The discharge coefficient Cd accounts for real-fluid effects including friction losses, velocity of approach, and crest geometry, correcting the theoretical weir formula Q = CLH^(3/2) to match actual measured discharge.
Which type of flow profile in open channels is classified as M1 (Mild slope, profile 1)?
Answer: Flow depth greater than normal depth on a mild slope
An M1 profile occurs on a mild slope (normal depth > critical depth) when the actual flow depth exceeds normal depth, causing the water surface to back up as in a backwater curve behind a dam or obstruction.
The net positive suction head available (NPSHA) for a pump must be:
Answer: Greater than the net positive suction head required (NPSHR)
To prevent cavitation, NPSHA (determined by system geometry and conditions) must exceed NPSHR (specified by the pump manufacturer), with a safety margin typically recommended by ASCE and pump standards.
The orifice equation Q = Cd·A·√(2gh) relates flow through an orifice to:
Answer: The discharge coefficient, orifice area, and head above the orifice centerline
The orifice equation computes volumetric flow rate from the discharge coefficient (Cd, typically 0.6–0.65 for sharp-edged orifices), the orifice cross-sectional area (A), and the driving head (h) above the orifice centerline.