What does the continuity equation express in a pipe flow system?
A Pressure difference
B Energy conservation
C Mass conservation
D Velocity increase
The continuity equation represents the conservation of mass in an incompressible fluid flow. It states that the mass flow rate must remain constant along the pipe, which means the product of velocity and cross‐sectional area is constant.
Which of these factors determines the magnitude of drag force on an object in a fluid?
A Object’s shape
B Fluid density
C Pipe diameter
D Fluid temperature
The drag force depends primarily on the shape of the object moving through the fluid. Streamlined objects experience less drag as they allow the fluid to flow smoothly around them, while blunt shapes create more drag due to turbulence.
What is the effect of increasing the flow velocity on the pressure in a flowing fluid, according to Bernoulli’s principle?
A Increases pressure
B Fluctuates
C No effect
D Decreases pressure
Bernoulli’s principle states that in a steady, incompressible flow, an increase in fluid velocity results in a decrease in pressure. This is a result of the conservation of energy in the system, where increased kinetic energy lowers pressure.
How does viscosity affect the fluid flow in pipes?
A Decreases flow rate
B Depends on pressure
C Increases flow rate
D No effect
Viscosity is the internal resistance to flow. Higher viscosity fluids, like oil, resist flow more than lower viscosity fluids, such as water, causing a reduction in flow rate and an increase in pressure loss in the pipe.
What type of flow occurs when the fluid velocity is not constant at every point?
A Steady flow
B Unsteady flow
C Laminar flow
D Turbulent flow
Unsteady flow occurs when the fluid velocity changes with time at any given point. In contrast, steady flow maintains a constant velocity at each point in the fluid at all times.
In dimensional analysis, what is the purpose of using a non-dimensional number like Reynolds number?
A Simplify calculations
B Measure fluid density
C Determine fluid velocity
D Predict flow type
Reynolds number is a non-dimensional number used in dimensional analysis to predict whether the flow will be laminar or turbulent. It compares inertial forces to viscous forces and helps in understanding flow behavior under various conditions.
What does the term “drag coefficient” describe in fluid mechanics?
A Fluid velocity
B Pressure drop
C Resistance due to shape
D Fluid density
The drag coefficient is a dimensionless number that quantifies the drag force experienced by an object moving through a fluid. It is highly influenced by the object’s shape, surface roughness, and flow conditions.
What happens to the velocity profile of a fluid as it flows through a pipe with a rough interior?
A It remains constant
B The flow becomes laminar
C It becomes more turbulent
D It becomes more uniform
A rough pipe surface increases the fluid’s turbulence, which disrupts smooth flow and promotes mixing. The velocity profile becomes irregular, and the flow can transition from laminar to turbulent at lower flow rates.
What is the primary characteristic of a compressible flow?
A Constant density
B Density changes with pressure
C Flow remains steady
D Viscosity varies
In compressible flow, the density of the fluid changes significantly with variations in pressure or temperature, which typically occurs in gases. This is in contrast to incompressible flow, where density remains constant.
What is the function of the boundary layer in fluid flow over a surface?
A Increase velocity
B Decrease turbulence
C Increase pressure
D Reduce drag
The boundary layer is a thin region of fluid near a solid surface where the velocity changes from zero at the surface to free‐stream velocity. This layer plays a crucial role in reducing friction and drag, which can be beneficial in reducing energy losses.
In fluid mechanics, what does the term “streamline” refer to?
A Path of a particle
B Fluid density
C Pressure distribution
D Flow rate
A streamline represents the path that a fluid particle follows in steady flow. At any given time, the velocity of the fluid at each point is tangent to the streamline, helping visualize the flow direction.
What does the dimensional analysis of fluid flow help in determining?
A Flow rate
B Pressure variation
C Non-dimensional numbers
D Energy loss
Dimensional analysis is used to derive non-dimensional numbers like Reynolds number, which help predict flow behavior (laminar or turbulent) and provide insights into scaling relationships, helping in the design of experiments and models.
What is the main factor influencing the lift force on an aircraft wing?
A Air density
B Temperature
C Wing shape
D Velocity
The lift force on an aircraft wing is primarily generated by the difference in pressure between the upper and lower surfaces, which is influenced by the wing’s shape. The curved upper surface leads to higher speed and lower pressure above the wing.
In a fluid flow system, what happens to the total mechanical energy when a fluid moves through a narrowing pipe?
A Energy is converted to heat
B Energy remains constant
C Energy decreases
D Energy increases
According to the principle of energy conservation, the total mechanical energy (sum of pressure energy, kinetic energy, and potential energy) remains constant along a streamline in a steady flow. As velocity increases in a constriction, pressure decreases, maintaining constant energy.
What is the main reason for the formation of vortices in fluid flow?
A Sudden changes in direction
B Fluid acceleration
C High pressure
D Low velocity
Vortices are formed when a fluid experiences sudden changes in direction or velocity. These changes create rotating regions of fluid, or eddies, which are responsible for the chaotic movement and swirling patterns often seen in turbulent flow.