What type of flow is characterized by smooth, parallel layers of fluid?
A Viscous flow
B Turbulent flow
C Laminar flow
D Steady flow
Laminar flow occurs when the fluid moves smoothly in parallel layers with minimal mixing between layers. It is typical at low velocities and for fluids with higher viscosity, where the flow is orderly and predictable.
What does the term “viscosity” describe in a fluid?
A Internal resistance
B Pressure
C Density
D Flow rate
Viscosity is a measure of a fluid’s internal resistance to flow. It represents the friction between layers of fluid as they move past each other. Higher viscosity means more resistance to flow, such as with honey or syrup.
What happens to the pressure in a fluid as the velocity increases, according to Bernoulli’s principle?
A Changes unpredictably
B Decreases
C Stays constant
D Increases
Bernoulli’s principle states that for an incompressible fluid, an increase in velocity leads to a decrease in pressure. This occurs because the total mechanical energy (pressure, kinetic, and potential) remains constant along a streamline.
What does the Reynolds number predict in a fluid flow system?
A Fluid velocity
B Fluid viscosity
C Fluid density
D Type of flow
The Reynolds number is a dimensionless quantity that helps predict the flow type in a fluid system. It determines whether the flow will be laminar (smooth) or turbulent (chaotic). A high Reynolds number generally indicates turbulent flow.
What is the primary reason for buoyancy in a fluid?
A Pressure difference
B Temperature difference
C Density difference
D Viscosity
Buoyancy is the upward force exerted on an object submerged in a fluid, caused by the pressure difference between the top and bottom of the object. This pressure difference is a result of the weight of the fluid.
How does the velocity of a fluid change as it passes through a narrowing pipe?
A Increases
B Stays constant
C Decreases
D Depends on the fluid
According to the continuity equation, when the pipe diameter decreases, the velocity of the incompressible fluid increases to maintain a constant flow rate. This is because the flow rate (Q) must remain constant, so velocity increases as the cross-sectional area decreases.
What is the primary factor influencing drag force on an object moving through air?
A Temperature
B Shape
C Viscosity
D Pressure
The shape of an object moving through a fluid significantly affects drag force. Streamlined shapes experience less drag, while irregular or blunt shapes have higher drag due to increased turbulence and resistance.
In which type of fluid flow does the flow velocity vary across the flow section?
A Laminar flow
B Steady flow
C Unsteady flow
D Turbulent flow
In laminar flow, fluid moves in layers, and the velocity varies across the cross section. The velocity is highest at the center and decreases near the surface due to friction, forming a parabolic velocity profile.
How is the flow in a pipe affected by an increase in fluid viscosity?
A Increases pressure
B No effect
C Decreases speed
D Increases speed
An increase in viscosity makes the fluid thicker and more resistant to flow. As viscosity increases, the fluid’s ability to flow easily decreases, resulting in a slower velocity in the pipe.
What is the main cause of cavitation in hydraulic systems?
A High temperature
B High viscosity
C Low pressure
D High velocity
Cavitation occurs when local pressure in the fluid falls below the vapor pressure, causing the fluid to vaporize and form bubbles. These bubbles collapse violently, causing damage to hydraulic components like pumps and valves.
Which of the following is the result of a high Reynolds number?
A Steady-state conditions
B Turbulent flow
C Laminar flow
D Steady flow
A high Reynolds number indicates turbulent flow, which is chaotic and characterized by swirling eddies and irregular fluid movement. It occurs at high velocities or when the fluid has a low viscosity.
What type of fluid flow occurs when the velocity at each point in the fluid remains constant over time?
A Steady flow
B Unsteady flow
C Laminar flow
D Turbulent flow
Steady flow occurs when the velocity of the fluid at each point remains constant over time. The fluid particles follow the same path and have the same speed at any given point throughout the flow.
What does the drag coefficient depend on in fluid mechanics?
A Viscosity
B Fluid density
C Velocity
D Shape of object
The drag coefficient depends on the shape of the object moving through the fluid. Streamlined shapes have lower drag coefficients, while blunt or irregular shapes have higher coefficients due to increased turbulence and resistance.
What happens to the fluid pressure as it moves upward in a column of liquid?
A Fluctuates
B Stays constant
C Decreases
D Increases
Fluid pressure decreases as the fluid moves upward in a column due to the reduction in the weight of the fluid above. This pressure variation is described by the hydrostatic pressure equation.
What does the term “hydraulic diameter” refer to in pipe flow?
A Effective diameter in non-circular ducts
B Flow velocity
C Diameter of the pipe
D Radius of the pipe
The hydraulic diameter is used to calculate flow resistance in non-circular ducts. It is defined as four times the cross-sectional area divided by the wetted perimeter. It simplifies the analysis of flow in irregular ducts.