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
Manning's roughness coefficient (n) in open channel flow primarily accounts for:
Answer: Boundary resistance due to channel surface texture
Manning's n is an empirical coefficient that quantifies energy losses due to boundary friction from the channel's surface roughness (concrete, earth, rock, vegetation, etc.).
The hydraulic radius (R) used in Manning's equation is defined as:
Answer: The ratio of flow area to wetted perimeter
Hydraulic radius R = A/P, where A is the cross-sectional flow area and P is the wetted perimeter, representing the efficiency of the channel shape in conveying flow.
Water hammer in a pipeline is primarily caused by:
Answer: Rapid changes in flow velocity such as sudden valve closure
Water hammer occurs when flow velocity changes rapidly (e.g., sudden valve closure), converting kinetic energy into pressure surges that propagate as pressure waves through the pipe at acoustic velocity.
Which of the following best describes specific energy in open channel flow?
Answer: Energy per unit weight measured with respect to the channel bottom as datum
Specific energy (E = y + V²/2g) is the total energy per unit weight of fluid measured with respect to the channel bottom, combining depth (pressure term) and velocity head.
In a pipe network analysis using the Hardy Cross method, what condition must be satisfied at each junction node?
Answer: Continuity: the algebraic sum of flows at each node must equal zero
The Hardy Cross method iteratively satisfies both loop equations (sum of head losses = 0) and nodal continuity (sum of inflows = sum of outflows = 0) simultaneously to solve pipe networks.
A venture meter measures flow rate by detecting the pressure difference between:
Answer: The inlet section and the constricted throat section
A venturi meter uses the pressure drop between the full-diameter inlet and the narrowed throat, where by Bernoulli's principle the velocity increases and pressure decreases, allowing flow rate calculation.
Cavitation in hydraulic systems is most likely to occur when:
Answer: Local pressure drops below the vapor pressure of the liquid
Cavitation occurs when local static pressure falls below the fluid's vapor pressure, causing vapor bubbles to form; when these bubbles collapse in higher-pressure zones, they cause erosion, noise, and vibration.