What is the primary characteristic of turbulent flow?
A Steady velocity
B Parallel layers
C Smooth layers
D Chaotic motion
Turbulent flow is characterized by irregular and chaotic fluid motion, with fluctuating velocity and the formation of eddies and vortices. This type of flow occurs at high Reynolds numbers and typically results in higher energy losses.
What does the Reynolds number indicate in fluid flow?
A Flow regime
B Viscosity
C Fluid density
D Pressure distribution
The Reynolds number is a dimensionless quantity that helps predict the flow type. A low Reynolds number (below 2000) suggests laminar flow, while a high Reynolds number (above 4000) indicates turbulent flow.
What happens to the velocity profile of a fluid in a pipe as it transitions from laminar to turbulent flow?
A Becomes parabolic
B Becomes irregular
C Stays constant
D Becomes smooth
In laminar flow, the velocity profile is parabolic, with the highest velocity at the center. As the flow transitions to turbulent, the profile becomes irregular with fluctuating velocities across the pipe’s cross‐section.
What is the main purpose of the continuity equation in fluid mechanics?
A Pressure measurement
B Energy conservation
C Mass conservation
D Velocity calculation
The continuity equation expresses the conservation of mass in a fluid system. It states that the mass flow rate remains constant in an incompressible fluid, ensuring that velocity and pipe cross‐sectional area are inversely related.
How does fluid viscosity affect drag force on an object moving through it?
A Increases drag force
B Decreases drag force
C No effect
D Varies with velocity
Higher viscosity increases the resistance to flow around an object, which results in a higher drag force. Viscous fluids, like honey or oil, create more resistance than less viscous fluids, like water or air.
What is the role of boundary layers in fluid flow?
A Increase turbulence
B Decrease velocity
C Increase pressure
D Reduce drag
The boundary layer is a thin region of fluid near a surface where the fluid velocity transitions from zero at the surface to free‐stream velocity. It helps reduce frictional resistance between the surface and the fluid, lowering drag.
What does Bernoulli’s equation assume about the flow of a fluid?
A Viscous flow
B Incompressible flow
C Compressible flow
D Unsteady flow
Bernoulli’s equation assumes the fluid is incompressible, meaning its density does not change with pressure or velocity changes. The equation represents the conservation of mechanical energy along a streamline for steady, incompressible flow.
What is the purpose of a Venturi meter in fluid flow measurement?
A Measure pressure
B Measure temperature
C Measure flow rate
D Measure velocity
A Venturi meter is a device used to measure the flow rate of a fluid by exploiting the pressure difference between a constricted and non‐constricted section of a pipe. It uses Bernoulli’s principle for flow rate calculations.
What happens when the velocity of a fluid increases in a pipe with a constant cross‐sectional area?
A Increases viscosity
B Stays constant
C Increases pressure
D Decreases pressure
According to Bernoulli’s principle, when the velocity of a fluid increases, its pressure decreases. This inverse relationship ensures the total mechanical energy in the fluid is conserved, with kinetic energy increasing as pressure decreases.
What does the term “drag coefficient” measure?
A Fluid pressure
B Flow velocity
C Resistance to flow
D Fluid density
The drag coefficient quantifies the resistance of an object moving through a fluid. It depends on factors such as the shape of the object, flow conditions, and the fluid’s properties, and is used to calculate drag force.
How does the pressure drop in a pipe relate to fluid velocity?
A Directly proportional
B Inversely proportional
C Exponentially related
D No relationship
According to the Darcy-Weisbach equation, the pressure drop in a pipe is related to the fluid velocity and pipe resistance. As velocity increases, the pressure drop increases, and vice versa, for a given pipe length and roughness.
What does the Navier-Stokes equation describe?
A Pressure distribution
B Velocity profiles
C Fluid motion
D Energy conservation
The Navier-Stokes equations describe the motion of viscous fluid substances. They provide a mathematical framework for understanding how fluids move under various conditions, accounting for factors like viscosity, pressure, velocity, and external forces.
What is the effect of fluid compressibility on flow analysis?
A No effect
B Decreases velocity
C Changes density
D Increases pressure
In compressible flow, particularly with gases, the density of the fluid changes significantly with variations in pressure or temperature. This must be accounted for in flow analysis, unlike incompressible flow, where density is assumed constant.
What is the purpose of using dimensional analysis in fluid mechanics?
A Simplify complex equations
B Predict fluid pressure
C Measure fluid density
D Measure flow velocity
Dimensional analysis helps simplify fluid mechanics equations by eliminating units and reducing variables, making it easier to compare different flow scenarios and derive non-dimensional numbers like Reynolds number for flow predictions.
What causes cavitation in a pump?
A Low pressure
B High velocity
C Low viscosity
D High temperature
Cavitation occurs when the local pressure drops below the fluid’s vapor pressure, causing the fluid to vaporize and form bubbles. These bubbles collapse violently when moving to higher-pressure areas, damaging pump components.