What does the continuity equation express in fluid flow?
A Velocity
B Pressure
C Energy conservation
D Mass conservation
The continuity equation is based on the principle of mass conservation. It states that for an incompressible fluid, the mass flow rate must remain constant along any streamline. This means that if the cross-sectional area changes, the velocity must adjust accordingly.
Which of these factors primarily determines whether a flow is laminar or turbulent?
A Reynolds number
B Pressure
C Temperature
D Density
The Reynolds number is a dimensionless quantity used to predict the flow regime. A low Reynolds number indicates laminar flow (smooth and steady), while a high Reynolds number leads to turbulent flow (chaotic and irregular).
How does temperature affect the viscosity of a fluid?
A Depends on fluid
B Decreases viscosity
C Increases viscosity
D No effect
For most fluids, increasing temperature decreases viscosity. As temperature rises, the fluid particles gain energy and move more freely, reducing the internal friction between them, which lowers viscosity.
What is the primary cause of pressure in a fluid at rest?
A Density
B Viscosity
C Fluid motion
D Gravity
In a fluid at rest, pressure is mainly caused by the weight of the fluid above a given point, which is a result of gravity acting on the fluid’s mass. This pressure increases with depth in the fluid.
What is the primary purpose of using a Venturi meter?
A Measure pressure
B Measure velocity
C Measure flow rate
D Measure temperature
A Venturi meter is used to measure the flow rate of a fluid in a pipe. It utilizes the principle of Bernoulli’s equation, where a constriction in the pipe causes a pressure drop, which is related to the flow rate.
What is the effect of increasing the diameter of a pipe on the flow of a fluid?
A Decreases velocity
B Increases pressure
C Increases velocity
D No effect
According to the continuity equation, when the diameter of a pipe increases, the fluid velocity decreases to maintain a constant flow rate, as the cross-sectional area and velocity are inversely related.
In a turbulent flow, what is the flow pattern like?
A Uniform across sections
B Chaotic and irregular
C Smooth and orderly
D Steady and non-rotational
Turbulent flow is characterized by chaotic and irregular fluid motion, with eddies, vortices, and fluctuations in velocity. It typically occurs at high velocities or with fluids having high Reynolds numbers.
What is the relationship between the drag force and the velocity of a fluid?
A Inversely proportional
B Exponentially related
C No relation
D Directly proportional
Drag force is directly proportional to the square of the velocity of the object moving through the fluid. As velocity increases, the drag force increases significantly due to higher resistance encountered by the object.
What is the primary factor in determining the lift force on an aircraft wing?
A Shape of the wing
B Air temperature
C Wing material
D Velocity
The lift force generated on an aircraft wing is primarily determined by the shape of the wing (airfoil). The curvature creates a difference in airspeed above and below the wing, generating upward lift.
What is the behavior of a fluid in a pipe if the flow is considered incompressible?
A Pressure varies only
B Temperature remains constant
C Density remains constant
D Density varies
Incompressible flow assumes that the fluid’s density does not change with pressure variations. This assumption simplifies many equations in fluid mechanics, particularly in pipe flow, where the density of water, for example, remains nearly constant.
What is the main principle behind the operation of a pump?
A Newton’s law of motion
B Bernoulli’s principle
C Energy conservation
D Conversion of work to fluid energy
A pump works by converting mechanical energy (work) into fluid energy. The mechanical energy added to the fluid increases its pressure and/or velocity, allowing the fluid to be transported or lifted in the system.
What is the boundary layer in fluid flow?
A Thin layer near the surface
B Streamline flow area
C Region of turbulence
D High pressure region
The boundary layer is a thin region of fluid flow near the surface of a solid object. In this layer, the fluid velocity changes from zero at the surface to the free-stream velocity, and it plays a key role in drag and friction.
What does a pressure drop in a pipe indicate?
A Increase in temperature
B Decrease in velocity
C Energy loss
D Increase in pressure
A pressure drop in a pipe typically indicates that energy is being lost due to friction and turbulence as the fluid moves through the pipe. This energy loss is converted into heat and can affect the flow efficiency.
Which fluid property is described by the ability of a fluid to resist flow?
A Viscosity
B Temperature
C Pressure
D Density
Viscosity is the property of a fluid that quantifies its internal resistance to flow. High viscosity fluids, like honey, resist flow more than low viscosity fluids, like water, making them “thicker” and slower moving.
What is the effect of compressibility on the behavior of gas flow?
A No effect
B Changes density
C Increases pressure
D Decreases velocity
In compressible flow, the density of the fluid (often gas) changes significantly as it moves, due to pressure and temperature variations. This is a key difference from incompressible flow, where density remains constant.