What does the Reynolds number indicate about fluid flow?
A Flow type
B Viscosity
C Pressure
D Velocity
The Reynolds number helps determine whether the flow will be laminar or turbulent. A low Reynolds number (<2000) indicates laminar flow, while a high number (>4000) suggests turbulent flow, with the transitional flow occurring in between.
How does the pressure vary in a fluid moving through a pipe when the velocity increases?
A Fluctuates
B Decreases
C Increases
D Stays constant
According to Bernoulli’s principle, in a steady flow of an incompressible fluid, when the velocity of the fluid increases, its pressure decreases, and vice versa, maintaining a balance of energy along the streamline.
What is the primary cause of drag force on an object moving through a fluid?
A Fluid temperature
B Object velocity
C Fluid pressure
D Object shape
The drag force is primarily affected by the shape of the object. Streamlined shapes experience less drag because they allow the fluid to flow smoothly around them, whereas blunt or irregular shapes create more resistance.
What is the purpose of a Venturi meter in fluid dynamics?
A Measure flow rate
B Measure temperature
C Measure pressure
D Measure velocity
A Venturi meter is used to measure the flow rate of a fluid by creating a constriction in the pipe. The pressure drop across the constriction is related to the flow rate, based on Bernoulli’s principle.
Which factor affects the laminar flow characteristics?
A Pipe diameter
B Pressure
C Fluid viscosity
D Temperature
Laminar flow is characterized by smooth, orderly motion of the fluid. High-viscosity fluids tend to flow more laminar because their internal resistance to movement minimizes turbulence, keeping the flow organized.
What happens to the pressure in a fluid when it moves upward in a column of liquid?
A Stays constant
B Increases
C Decreases
D Fluctuates
As the fluid moves upward in a column, the pressure decreases because the weight of the fluid above decreases with height. This is described by the hydrostatic pressure equation.
In which type of flow is the velocity constant at every point along a streamline?
A Laminar flow
B Uniform flow
C Turbulent flow
D Steady flow
In laminar flow, the velocity of the fluid at each point along a streamline remains constant. The flow is smooth, and there is no mixing between adjacent layers of the fluid.
What happens to the viscosity of a fluid as its temperature increases?
A Stays constant
B Decreases
C Fluctuates
D Increases
With an increase in temperature, the viscosity of most fluids decreases. The higher kinetic energy of the molecules allows them to slide past each other more easily, reducing internal resistance to flow.
What is the significance of the boundary layer in fluid mechanics?
A It defines velocity
B It increases turbulence
C It creates pressure
D It affects drag
The boundary layer is the thin region of fluid near a solid surface where the fluid velocity transitions from zero (at the surface) to the free-stream velocity. This layer plays a key role in drag force and frictional resistance.
What does Bernoulli’s equation assume about the flow of a fluid?
A Temperature variation
B Viscous flow
C Steady and incompressible flow
D Variable density
Bernoulli’s equation assumes the flow is steady (constant over time), incompressible (density remains constant), and there is no viscosity. It expresses the conservation of mechanical energy along a streamline.
What happens when the flow in a pipe transitions from laminar to turbulent?
A Decreases pressure
B Increases turbulence
C Increases pressure
D Decreases velocity
When the Reynolds number exceeds a certain threshold (approximately 2000), laminar flow transitions into turbulent flow, which is characterized by chaotic fluid motion, eddies, and increased turbulence. This transition increases energy losses and friction.
How does the velocity of a fluid change as it moves through a constricted section of a pipe?
A Increases
B Depends on pressure
C Stays constant
D Decreases
According to the continuity equation, if the cross-sectional area of a pipe decreases, the velocity of an incompressible fluid must increase to maintain the same flow rate. This is a key principle in fluid dynamics.
What does the term “hydraulic diameter” refer to in non-circular ducts?
A Flow velocity
B Pipe diameter
C Fluid density
D Effective diameter
The hydraulic diameter is used for non-circular ducts, calculated as four times the cross-sectional area divided by the wetted perimeter. It is used to calculate flow resistance in irregular ducts.
What is the primary cause of cavitation in pumps?
A High temperature
B High velocity
C Low pressure
D High viscosity
Cavitation occurs when the local pressure in a fluid falls below the vapor pressure, causing the fluid to vaporize and form bubbles. These bubbles collapse violently when moving to higher-pressure regions, causing damage to the pump.
What is the term for the resistance to fluid flow due to the roughness of a pipe’s interior surface?
A Frictional resistance
B Drag force
C Boundary layer
D Viscosity
Frictional resistance refers to the resistance encountered by the fluid as it moves along a pipe’s surface. It is influenced by the roughness of the pipe and the fluid’s viscosity, which increases energy losses in the system.
