Font size
Worksheetsлекция 14-12
Total questions: 103
Worksheet time: 52mins
1. What characterizes the developing flow region in a pipe?
A. The velocity profile is parabolic and constant in time.
B. The velocity profile starts flat and changes due to the growing boundary layer
C. The velocity profile remains flat and uniform throughout the pipe.
D. The velocity profile becomes flatter near the walls as Reynolds number increases.
2. In fully developed laminar flow, the velocity profile is:
A. Constant and parabolic.
B. Flattened at the center with steep gradients near the walls.
C. Random and three-dimensional.
D. Flattened at high Reynolds numbers.
3. What is a key feature of turbulent flow in pipes?
A. Uniform velocity profile and no energy transfer between layers.
B. Orderly motion of fluid layers with minimal mixing.
C. Random, rapid fluctuations (eddies) that enhance momentum and energy transfer.
D. A parabolic velocity profile independent of Reynolds number.
4. Which region in turbulent flow near the wall is dominated by viscous effects?
A. Outer turbulent layer.
B. Overlap layer.
C. Buffer layer.
D. Viscous sublayer.
5. What does the Moody chart represent?
A. The relationship between velocity and pipe diameter for laminar flow.
B. The Darcy friction factor as a function of Reynolds number and relative roughness.
C. The velocity profile for turbulent flow near a wall.
D. The parabolic profile for laminar flow in circular pipes.
6. What is the Colebrook equation used for?
A. Calculating the Reynolds number for non-circular ducts.
B. Determining pressure drops in laminar flow.
C. Evaluating the friction factor for turbulent flow in pipes.
D. Calculating the flow rate in rough pipes.
7. How do major and minor losses differ in pipe flow systems?
A. Major losses occur in fittings, while minor losses occur in straight pipes.
B. Major losses are due to viscous effects in straight pipes, while minor losses are due to components like valves and bends.
C. Minor losses dominate in systems with long pipes.
D. Both are caused by flow separation and mixing.
8. What happens to the velocity profile in a fully developed turbulent flow?
A. It remains parabolic and constant in time.
B. It becomes flatter at the center with large velocity gradients near the walls.
C. It is dominated by molecular diffusion throughout the pipe.
D. It is completely uniform along the pipe cross-section.
9. What are the two components of turbulent shear stress?
A. Axial stress and radial stress.
B. Viscous stress and eddy stress.
C. Laminar component and turbulent component.
D. Momentum stress and energy stress.
10. Which equation can be used as an approximation of the Colebrook equation for smooth pipes?
A. Haaland equation.
B. Blasius equation.
C. Reynolds correlation.
D. Swamee and Jain equation.
11. Which region in turbulent pipe flow is dominated by turbulent effects?
A. Viscous sublayer.
B. Buffer layer.
C. Outer turbulent layer.
D. Overlap layer.
12. What determines the thickness of the viscous sublayer?
A. Pipe roughness and Reynolds number.
B. Kinematic viscosity and flow velocity.
C. Diameter of the pipe and velocity gradient.
D. Fluid density and pipe length.
13. What is the main purpose of the Moody chart?
A. To estimate head loss in minor pipe fittings.
B. To calculate the hydraulic diameter of non-circular ducts.
C. To determine the friction factor for fully developed pipe flow.
D. To predict pressure drops in laminar flow.
14. In the context of turbulent flow, what is "eddy viscosity"?
A. The viscosity of the fluid near the wall.
B. A property that accounts for momentum transport by eddies.
C. The same as molecular viscosity but for turbulent flow.
D. The viscosity caused by random motion in laminar layers.
15. For rough pipes, what is typically needed to solve the Colebrook equation?
A. An explicit solution using Reynolds number.
B. An initial guess for the friction factor and iteration.
C. A direct calculation of relative roughness.
D. A Moody chart for smooth pipes.
16. What is a key feature of the buffer layer in turbulent pipe flow?
A. Laminar flow dominates completely.
B. Viscous and turbulent effects are both significant.
C. Turbulent effects dominate, with no viscous effects.
D. The velocity profile is linear and steady.
17. What increases the fullness of a turbulent velocity profile?
A. Decreasing flow velocity.
B. Increasing Reynolds number.
C. Reducing the pipe roughness.
D. Decreasing eddy viscosity.
18. What causes turbulent flow to enhance momentum and energy transfer?
A. Uniform velocity profiles.
B. Random motion of eddies and rapid fluctuations.
C. Laminar flow layers exchanging energy.
D. Reduced shear stress near the walls.
19. Which type of flow is characterized by a parabolic velocity profile?
A. Fully developed turbulent flow.
B. Developing turbulent flow.
C. Fully developed laminar flow.
D. Transitional flow.
20. What does the Reynolds number determine in pipe flow?
A. The pipe diameter required for a given flow rate.
B. Whether the flow is laminar, turbulent, or transitional.
C. The thickness of the pipe wall.
D. The velocity gradient near the pipe center.
21. Which region of turbulent flow is closest to the pipe wall?
A. Outer turbulent layer.
B. Overlap layer.
C. Viscous sublayer.
D. Buffer layer.
22. What does the Darcy friction factor depend on?
A. Pipe diameter and flow velocity.
B. Reynolds number and relative roughness.
C. Length of the pipe and fluid density.
D. Viscosity and pipe material.
23. Which layer in turbulent flow shows steep velocity gradients?
A. Buffer layer.
B. Outer turbulent layer.
C. Overlap layer.
D. Viscous sublayer.
24. What happens to the viscous sublayer as the Reynolds number increases?
A. It thickens and dominates the flow.
B. It becomes thinner and less significant.
C. It remains constant regardless of flow velocity.
D. It transitions into the buffer layer.
25. What is a primary characteristic of turbulent flow in a pipe?
A. Smooth, predictable motion of fluid layers.
B. Steady pressure and velocity profiles.
C. Random fluctuations and eddy motion.
D. A velocity profile that remains uniform across the pipe.
26. What is the significance of the overlap (transition) layer in turbulent flow?
A. It marks the transition between viscous and turbulent effects.
B. It is dominated by viscous forces only.
C. It has a fully developed velocity profile.
D. It shows no influence of eddy motion.
27. What is the general shape of a velocity profile for fully developed turbulent flow?
A. Parabolic, with maximum velocity at the center.
B. Flatter in the center with steep gradients near the walls.
C. Uniform across the pipe's cross-section.
D. Linear throughout the pipe's length.
28. What does the term "relative roughness" represent in pipe flow?
A. The ratio of flow velocity to pipe diameter.
B. The ratio of roughness height to pipe diameter.
C. The ratio of Reynolds number to flow rate.
D. The ratio of friction factor to flow velocity.
29. What happens to the friction factor as pipe roughness increases in turbulent flow?
A. It decreases.
B. It remains constant.
C. It increases.
D. It becomes independent of Reynolds number.
30. What is the purpose of turbulence models like Boussinesq’s model?
A. To describe laminar flow shear stress.
B. To predict momentum exchange due to turbulent eddies.
C. To calculate flow rates in straight pipes.
D. To estimate friction factor for non-circular pipes.
What characterizes internal flow?
A. Fluid flowing over an open surface.
B. Fluid flowing along a surface.
C. Fluid flowing inside a fully filled conduit driven by a pressure difference.
D. Fluid flowing due to gravity alone.
Why are circular pipes most commonly used?
A. They are cheaper to manufacture.
B. They are easier to install.
C. They can withstand large pressure differences.
D. They require less space.
What velocity profile is characteristic of laminar flow?
A. Completely uniform.
B. Flat in the center, with sharp changes near the walls.
C. Parabolic.
D. Random and fluctuating.
At what Reynolds number is the flow considered turbulent?
A. Re<2100
B. Re>4000
C. 2100<Re<4000
D. Re=2300
What is the main cause of pressure drop in pipes?
A. Changes in temperature.
B. Energy losses due to viscosity and friction.
C. Transition between flow regimes.
D. Valve resistance.
What characterizes fully developed flow?
A. Velocity profile remains constant along the pipe’s length.
B. Velocity profile changes continuously.
C. Boundary layer does not reach the pipe center.
D. Friction has no effect on the flow.
Which flow regime has smooth, well-defined streamlines?
A. Laminar flow.
B. Turbulent flow.
C. Transitional flow.
D. Developing flow.
8. What happens to fluid near the pipe walls due to the no-slip condition?
A. Fluid velocity becomes maximum.
B. Fluid velocity is zero.
C. Fluid velocity increases linearly.
D. Fluid velocity fluctuates randomly.
What is the primary factor distinguishing laminar and turbulent flows?
A. Flow velocity.
B. Fluid density.
C. Degree of order in motion.
D. Temperature of the fluid.
Why is average velocity (Vavg) used in pipe flow calculations?
A. Because it represents the highest velocity in the pipe.
B. Because the velocity at the wall is zero.
C. To account for temperature changes in the fluid.
D. To simplify calculations for incompressible flow.
What is the velocity profile for fully developed turbulent flow?
A. Parabolic, with a maximum at the center.
B. Flatter in the center with steep gradients near the walls
C. Completely uniform throughout the pipe.
D. Constant and independent of Reynolds number.
What is the role of the boundary layer in pipe flow?
A. It causes fluid to move faster near the walls
B. It separates the flow into viscous and core regions.
C. It determines the flow regime
D. It ensures uniform flow across the pipe.
What happens in the hydrodynamic entry region of a pipe?
A. Velocity profile becomes parabolic immediately.
B. The boundary layer grows until it fills the entire pipe.
C. Flow is fully turbulent from the start.
D. Pressure drop is negligible.
Which condition indicates fully developed flow?
A. The velocity profile changes along the pipe length.
B. The wall shear stress remains constant.
C. The boundary layer has not yet reached the pipe center.
D. Reynolds number exceeds 4000.
What determines the critical Reynolds number for flow transition?
A. Fluid viscosity and density
B. Surface roughness and pipe geometry.
C. Flow velocity and pressure.
D. All of the above.
Why are temperature changes due to friction often ignored in pipe flow calculations?
A. Frictional heating is negligible compared to pressure drop effects.
B. Temperature changes are already accounted for in velocity profiles.
C. Frictional effects only occur in turbulent flow.
D. Heat transfer is dominant in all flow conditions.
How is Reynolds number calculated for non-circular pipes?
A. Using the pipe's hydraulic diameter
B. Using the cross-sectional area only.
C. Using the pipe's perimeter only.
D. Assuming the pipe is circular.
Which of the following primarily causes a transition from laminar to turbulent flow?
A. Increased surface roughness and disturbances.
B. Increased fluid density.
C. Decreased pipe diameter.
D. Decreased viscosity.
What is the main consequence of friction in fluid flow?
A. Temperature rise.
B. Pressure drop.
C. Uniform velocity distribution.
D. Increased flow rate.
What does the principle of conservation of mass state?
A. The net mass transfer in or out of a control volume equals the change in total mass within the control volume over time.
B. Mass flow rate remains constant, regardless of the pipe cross-section.
C. Mass flow rate depends only on velocity, not on the pipe's area
D. Mass can be created or destroyed under specific conditions.
What is mechanical energy?
A. The energy that cannot be converted into work
B. The form of energy that can be fully converted into mechanical work.
C. Energy only associated with pressure forces.
D. The sum of thermal and potential energy in a system.
What does pump efficiency represent?
A. The degree of conversion of mechanical energy to thermal energy.
B. The degree of perfection in converting mechanical work into fluid energy.
C. The ratio of fluid velocity to pressure.
D. The ability of a pump to maintain constant flow.
What does the Bernoulli equation describe?
A. The balance of mechanical energy along a streamline for steady, incompressible flow.
B. The conservation of mass within a control volume.
C. The relationship between thermal and kinetic energy in turbulent flow.
D. The effect of surface roughness on flow velocity.
What is total pressure in fluid flow?
A. The sum of static and dynamic pressures.
B. The pressure at which fluid stops completely isentropically.
C. The sum of static, dynamic, and hydrostatic pressures.
D. The pressure caused by frictional losses in the flow.
What is the hydraulic grade line (HGL)?
A. The line representing the total head of the fluid.
B. The sum of static pressure and elevation head.
C. The pressure caused by flow velocity.
D. The visualization of dynamic pressure only.
What primarily drives internal flow in a conduit?
A. Gravity.
B. Surface tension.
C. Pressure difference.
D. Shear forces
What characterizes laminar flow?
A. Random and fluctuating velocity components.
B. Smooth, highly ordered motion
C. Large-scale mixing and eddies.
D. High Reynolds number values.
What is the role of the boundary layer in pipe flow?
A. It creates uniform velocity across the pipe
B. It separates regions of viscous effects from core flow
C. It reduces pressure losses due to friction.
D. It only affects turbulent flow.
When does flow become fully developed in a pipe?
A. When the velocity profile no longer changes along the pipe.
B. When the Reynolds number is less than 2300.
C. When the boundary layer is negligible.
D. When frictional losses stop affecting the flow.
What does the hydraulic diameter (Dh) represent?
A. The diameter of a circular pipe only.
B. The equivalent diameter for noncircular pipes.
C. The ratio of pipe length to cross-sectional area
D. The diameter that minimizes frictional losses.
What happens at the entrance region of a pipe?
A. The velocity profile is fully parabolic from the start.
B. The boundary layer begins to grow from the pipe walls.
C. Flow is uniform throughout the pipe length.
D. Turbulent effects dominate immediately.
What is the primary reason for a transition from laminar to turbulent flow?
A. Increased viscosity of the fluid.
B. Increased disturbances such as roughness or vibrations.
C. Decreased flow velocity.
D. Constant pressure difference in the pipe.
How does mechanical energy differ from thermal energy?
A. Mechanical energy can be fully converted into work, while thermal energy cannot.
B. Thermal energy depends on pressure, while mechanical energy does not.
C. Mechanical energy is only present in stationary fluids.
D. Thermal energy is independent of fluid velocity.
How are static pressure and dynamic pressure related in Bernoulli's principle?
A. They are independent of each other.
B. A decrease in static pressure corresponds to an increase in dynamic pressure.
C. They remain constant along a streamline.
D. They depend only on the fluid's viscosity.
What is the purpose of the energy grade line (EGL) in fluid flow analysis?
A. To represent static pressure only.
B. To show the total head of the fluid, including velocity and elevation effects.
C. To indicate the effects of friction on the flow.
D. To measure the hydrostatic pressure.
What does the term "stagnation pressure" refer to?
A. The pressure when a fluid particle is brought to a complete stop isentropically.
B. The sum of the static pressure and elevation head.
C. The difference between static and dynamic pressures.
D. The pressure caused by flow turbulence.
What happens to the boundary layer as flow develops in a pipe?
A. It becomes thinner near the walls.
B. It grows and eventually fills the entire pipe.
C. It disappears when the Reynolds number exceeds 2300.
D. It remains constant throughout the pipe
In laminar flow, what is the primary force acting within the fluid?
A. Inertial forces.
B. Viscous forces.
C. Turbulent forces.
D. Centrifugal forces.
Which assumption is NOT valid in Bernoulli's equation?
A. The flow is compressible.
B. The flow is steady.
C. There are no frictional effects
D. The fluid is inviscid
What is the focus of the Eulerian approach in fluid mechanics?
A. Tracking the trajectories of individual fluid particles.
B. Analyzing fluid properties at fixed points in space.
C. Following changes in velocity and position of individual particles.
D. Studying the motion of a group of particles over time.
What does the Lagrangian approach involve?
A. Analyzing the flow properties at specific locations over time
B. Following individual fluid particles and observing their properties as they move
C. Measuring pressure and temperature along a streamline.
D. Determining the overall flow behavior in a control volume
What is a streamline?
A. A line that represents the trajectory of a fluid particle
B. A line that is tangent to the velocity field at every point.
C. A line connecting all particles passing through a single point in the flow.
D. A line that represents areas of constant pressure in the flow.
How does the Reynolds Transport Theorem (RTT) relate control volumes and systems?
A. It calculates the velocity field for a given system.
B. It links changes in a property within a control volume to flows across its boundaries.
C. It measures the total energy of a system in a flow field.
D. It predicts the behavior of turbulent flow within a system
What is the purpose of the area vector in RTT?
A. To calculate the size of the control volume.
B. To determine the direction and magnitude of the flow across a surface.
C. To track the movement of individual fluid particles.
D. To measure the total flux of energy within the control volume.
What does the sign of the scalar (dot) product indicate in RTT?
A. The magnitude of the velocity in the control volume.
B. Whether the flow is entering or leaving the control volume.
C. The total energy of the fluid in the system.
D. The density of the fluid at the control surface.
What is the main advantage of the Eulerian approach in fluid mechanics?
A. It provides detailed trajectories of fluid particles.
B. It simplifies analysis by focusing on fixed points in space.
C. It allows for the calculation of intensive properties for individual particles.
D. It eliminates the need for boundary conditions in flow analysis.
Which of the following is a Lagrangian concept?
A. Streamline.
B. Streakline.
C. Pathline.
D. Control surface.
How does the RTT simplify fluid flow analysis?
A. By focusing only on compressible flows.
B. By converting system-based laws to control-volume-based equations.
C. By neglecting external forces acting on the control volume.
D. By eliminating the need for continuity equations.
What happens to the control surface in RTT when flow leaves the control volume?
A. The area vector becomes negative.
B. The velocity field is zero.
C. The flow is considered positive.
D. The flow rate decreases.
What is the primary difference between a system and a control volume in fluid mechanics?
A. A system has fixed boundaries, while a control volume allows mass to cross its boundaries.
B. A system focuses on steady flow, while a control volume only applies to unsteady flow.
C. A system requires no external forces, while a control volume does.
D. A system works for incompressible flows only, while a control volume works for compressible flows.
What does a streakline represent in fluid flow?
A. A line traced by a single particle as it moves through the flow field.
B. A line tangent to the velocity field at every point.
C. All particles that have passed through a common point in the flow.
D. A line of constant pressure in the flow field.
What happens to the velocity vector at a control surface if flow enters the control volume?
A. It is parallel to the control surface
B. It is perpendicular to the control surface and points inward.
C. It is perpendicular to the control surface and points outward
D. It becomes zero
In the Lagrangian approach, what is tracked over time?
A. Fluid properties at fixed points in space.
B. The trajectory, velocity, and acceleration of individual particles.
C. Pressure and temperature changes in a control volume.
D. Net flux across a control surface.
What does the Reynolds Transport Theorem primarily address?
A. The conservation of mass only in a closed system.
B. The relationship between system properties and control volume properties.
C. The computation of velocity fields in turbulent flow.
D. The calculation of boundary conditions for incompressible flows.
Why is the Eulerian approach preferred in practical fluid dynamics applications?
A. It eliminates the need for boundary conditions.
B. It simplifies analysis by focusing on flow properties at fixed locations.
C. It provides detailed trajectories of individual fluid particles.
D. It avoids the need for conservation laws.
What is the Bernoulli equation primarily concerned with?
A. Conservation of mass.
B. Conservation of kinetic, potential, and flow energy
C. Conservation of temperature.
D. Conservation of viscosity effects
Which of the following is a key assumption for the Bernoulli equation?
A. The fluid is compressible.
B. The flow is steady and inviscid.
C. The flow has significant frictional effects.
D. The velocity remains constant throughout the flow field.
What does the Mach number represent?
A. The ratio of fluid velocity to the speed of sound.
B. The ratio of kinetic energy to potential energy in the flow
C. The relationship between pressure and velocity in the flow
D. The ratio of density to temperature in compressible flow
What is a streamline?
A. The path traced by a single particle in the flow field.
B. A curve that is tangent to the local velocity vector at every point.
C. A line showing all particles that passed through a single point.
D. A curve representing regions of constant pressure
Which of the following best describes a streamtube?
A. The path followed by a group of fluid particles over time.
B. A bundle of streamlines through which fluid is confined.
C. A time-integrated snapshot of fluid motion.
D. A representation of compressible flow regions.
What is the main difference between pathlines and streaklines?
A. Pathlines represent instantaneous velocity, while streaklines show past trajectories.
B. Pathlines trace the trajectory of a single particle, while streaklines represent particles passing through a point.
C. Pathlines are used in compressible flow, while streaklines are used in incompressible flow.
D. Pathlines are steady, while streaklines are unsteady.
When are pathlines and streamlines identical?
A. When the flow is compressible.
B. When the flow is steady.
C. When the flow is turbulent.
D. When the flow is two-dimensional.
What is the primary purpose of flow visualization?
A. To calculate velocity vectors in turbulent flows.
B. To examine flow field features and patterns.
C. To determine the Mach number in compressible flows.
D. To predict pressure distribution in boundary layers.
Which of the following equations expresses the conservation of mass?
A. Bernoulli equation.
B. Continuity equation.
C. Energy equation.
D. Momentum equation.
What happens to fluid inside a streamtube?
A. It can freely cross the boundaries of the streamtube.
B. It remains confined within the streamtube.
C. Its pressure remains constant.
D. Its velocity remains constant.
Why is the Bernoulli equation limited in its application?
A. It only applies to turbulent flows.
B. It neglects viscous effects and assumes steady, inviscid flow.
C. It cannot be used for compressible flows.
D. It assumes constant density throughout the flow field.
What does the energy equation in fluid dynamics express?
A. The conservation of pressure.
B. The conservation of temperature.
C. The conservation of total energy, including kinetic, potential, and internal energy.
D. The relationship between mass and velocity.
What is the Mach number (Ma) in fluid dynamics?
A. A measure of fluid density.
B. The ratio of fluid velocity to the speed of sound in the medium.
C. The ratio of dynamic pressure to static pressure.
D. A measure of the compressibility of a fluid.
How are streamlines useful in fluid dynamics?
A. They represent regions of equal pressure.
B. They show the path traced by individual particles.
C. They provide an instantaneous direction of fluid motion throughout the flow field.
D. They are used to calculate the Reynolds number.
In the Lagrangian approach, what is tracked over time?
A. Fluid properties at fixed points in space.
B. The position, velocity, and acceleration of individual fluid particles.
C. The changes in pressure and temperature across the flow field.
D. The flow rate through control volumes.
What happens to the velocity vector at a control surface if flow enters the control volume?
A. The velocity vector points inward, indicating negative flux.
B. The velocity vector points outward, indicating positive flux.
C. The velocity vector becomes zero.
D. The velocity vector becomes perpendicular to the surface.
How does flow visualization help in fluid dynamics?
A. It helps measure the Reynolds number in compressible flow.
B. It assists in visualizing flow field features in both physical experiments and computational fluid dynamics (CFD).
C. It calculates pressure gradients in boundary layers.
D. It provides exact velocity profiles in turbulent flow.
What is a control volume in fluid mechanics?
A. A fixed region in space used to analyze changes in fluid properties.
B. A volume where the fluid is stationary and cannot change its properties.
C. A section of the flow field where only static properties are measured.
D. A system where mass cannot enter or exit.
