What does the Reynolds number help predict in fluid flow?
A Flow type
B Flow rate
C Pressure drop
D Fluid density
The Reynolds number is a dimensionless number used to predict the flow type in a fluid. It helps determine whether the flow is laminar (smooth) or turbulent (chaotic). A low Reynolds number indicates laminar flow, while a high Reynolds number suggests turbulent flow.
What is the main feature of laminar flow?
A High turbulence
B Chaotic movement
C High velocity
D Parallel layers
Laminar flow is characterized by fluid moving in smooth, parallel layers with minimal mixing. It occurs at low velocities and for high-viscosity fluids, where each layer moves smoothly over the next.
What does the Navier-Stokes equation describe in fluid mechanics?
A Temperature changes
B Fluid motion
C Flow rate
D Pressure distribution
The Navier-Stokes equations describe the motion of viscous fluids. They are a set of nonlinear partial differential equations that account for the fluid’s velocity, pressure, density, and viscosity, governing the behavior of fluid flow.
In which type of flow do fluid particles follow a straight path without mixing?
A Steady flow
B Turbulent flow
C Laminar flow
D Compressible flow
In laminar flow, the fluid particles follow a straight path without mixing. The flow is orderly and occurs at low velocities, typically when the Reynolds number is low.
Which fluid property quantifies the resistance to shear forces within a fluid?
A Viscosity
B Temperature
C Density
D Pressure
Viscosity is the measure of a fluid’s resistance to flow or shear. It describes the internal friction between fluid layers. Fluids with high viscosity, like honey, resist flow more than those with low viscosity, like water.
What happens to the velocity of a fluid as it passes through a narrowing pipe, assuming constant flow rate?
A Increases
B Decreases
C Stays constant
D Fluctuates
According to the continuity equation, when the diameter of the pipe decreases, the fluid’s velocity must increase to maintain the same flow rate. This is because the flow rate (Q) is constant for incompressible fluids.
What does Bernoulli’s equation describe in fluid dynamics?
A Energy conservation
B Flow velocity
C Pressure difference
D Flow rate
Bernoulli’s equation is based on the conservation of energy principle. It relates pressure, velocity, and elevation in an incompressible, steady fluid flow, stating that the total mechanical energy remains constant along a streamline.
What effect does increasing the fluid’s temperature typically have on its viscosity?
A No effect
B Decreases viscosity
C Increases viscosity
D Fluctuates
As temperature increases, the viscosity of most fluids decreases. The fluid particles gain more kinetic energy, allowing them to move past each other more easily, reducing internal friction and making the fluid flow more easily.
Which type of flow is characterized by irregular, chaotic motion and eddies?
A Uniform flow
B Laminar flow
C Turbulent flow
D Steady flow
Turbulent flow occurs at high velocities or with low-viscosity fluids. It is marked by chaotic and irregular motion, with eddies, vortices, and fluctuating velocity profiles that make the flow unpredictable.
What is the primary cause of pressure in a fluid at rest?
A Temperature
B Viscosity
C Gravity
D Density
In a fluid at rest, pressure is primarily caused by the weight of the fluid. Gravity pulls the fluid downward, and pressure increases with depth due to the increasing weight of the fluid above the point of measurement.
What factor does NOT affect the drag force on an object moving through a fluid?
A Fluid temperature
B Fluid density
C Object shape
D Fluid velocity
Drag force is influenced by the velocity of the fluid, the shape of the object, and the fluid density. However, fluid temperature does not directly affect the drag force unless it changes the fluid’s density or viscosity significantly.
What is the effect of increasing the velocity of fluid flow in terms of pressure, according to Bernoulli’s principle?
A Fluctuates
B Decreases pressure
C Increases pressure
D No effect
According to Bernoulli’s principle, as the velocity of an incompressible fluid increases, its pressure decreases. This is due to the conversion of pressure energy into kinetic energy, keeping the total energy constant along a streamline.
What is the main factor that causes cavitation in pumps?
A High velocity
B Low pressure
C High viscosity
D Low temperature
Cavitation occurs when the local pressure in the fluid drops below the vapor pressure, causing the fluid to vaporize and form bubbles. These bubbles collapse when moving to higher-pressure areas, causing damage to pump surfaces.
Which equation is used to describe the conservation of mass in a fluid flow?
A Euler’s equation
B Bernoulli’s equation
C Continuity equation
D Navier-Stokes equation
The continuity equation describes the conservation of mass in fluid dynamics. It states that the mass flow rate is constant along a streamline for an incompressible fluid. If the cross-sectional area changes, the fluid velocity adjusts accordingly.
What does the boundary layer represent in fluid flow?
A Velocity variation
B Viscosity gradient
C Fluid density
D Pressure zone
The boundary layer in fluid flow refers to the thin layer of fluid close to a solid surface, where the velocity changes from zero at the surface to the free-stream velocity. This layer is important for drag and friction calculations.