Viscosity is a measure of a fluid’s resistance to flow. The SI unit of dynamic viscosity is Pascal second (Pa•s). Poise is a unit of viscosity in the CGS system, but Pascal second is the standard SI unit. Newton and Joule are units of force and energy, respectively, and are not related to viscosity.
Which of the following is a property of an ideal fluid?
A Viscosity
B Zero viscosity
C Compressibility
D Surface tension
An ideal fluid is a theoretical concept where the fluid is assumed to have no viscosity (frictionless) and is incompressible. Real fluids have viscosity, but ideal fluids are used in simplified models to analyze fluid behavior without considering viscous effects.
What does Bernoulli’s equation primarily describe?
A Conservation of energy
B Conservation of mass
C Conservation of momentum
D Conservation of pressure
Bernoulli’s equation states that the total mechanical energy (sum of pressure energy, kinetic energy, and potential energy) of an ideal, incompressible fluid remains constant along a streamline. It is derived from the principle of conservation of energy.
What is the continuity equation based on?
A Conservation of energy
B Conservation of momentum
C Conservation of mass
D Conservation of pressure
The continuity equation states that the mass flow rate of a fluid remains constant in a closed system. It is derived from the principle of conservation of mass and is expressed as A₁V₁ = A₂V₂, where A is the cross-sectional area and V is the velocity.
What is the Reynolds number used to determine?
A Pressure in a fluid
B Type of flow (laminar or turbulent)
C Viscosity of a fluid
D Density of a fluid
The Reynolds number is a dimensionless quantity used to predict the flow regime in a fluid. If Re < 2000, the flow is laminar; if Re > 4000, it is turbulent. It depends on velocity, characteristic length, viscosity, and density.
Which device is used to measure fluid velocity in a pipe?
A Manometer
B Barometer
C Venturimeter
D Hydrometer
A Venturimeter is a flow measurement device that uses Bernoulli’s principle to calculate the velocity of a fluid in a pipe by measuring the pressure difference between two sections of different cross-sectional areas.
What is the primary cause of cavitation in fluids?
A Low pressure
B High pressure
C High temperature
D Low viscosity
Cavitation occurs when the local pressure in a fluid drops below its vapor pressure, causing the formation of vapor bubbles. These bubbles collapse violently when they move to higher pressure regions, causing damage to surfaces.
What is the formula for the hydraulic gradient in open channel flow?
A ΔP / L
B Δh / L
C ΔV / L
D ΔT / L
The hydraulic gradient is the change in hydraulic head (Δh) per unit length (L) along the flow direction. It represents the slope of the energy grade line in open channel flow.
Which of the following is an example of laminar flow?
A Waterfall
B River flow
C Ocean waves
D Smoke rising from a candle
Laminar flow is characterized by smooth, orderly movement of fluid particles in parallel layers. Smoke rising from a candle initially exhibits laminar flow before transitioning to turbulent flow as it rises.
What is the primary force acting on a fluid in fluid statics?
A Gravitational force
B Inertial force
C Viscous force
D Surface tension
In fluid statics, the primary force acting on a fluid is gravity, which causes pressure variations with depth. This is described by the hydrostatic equation P = ρgh, where P is pressure, ρ is density, g is gravity, and h is depth.
What is the purpose of a weir in fluid mechanics?
A Increase pressure
B Reduce velocity
C Store fluid
D Measure flow rate
A weir is a barrier installed in an open channel to measure the flow rate of water. The height of the water flowing over the weir is used to calculate the discharge.
What is the effect of increasing viscosity on fluid flow?
A Decreases flow rate
B Increases flow rate
C No effect on flow rate
D Increases turbulence
Viscosity is a measure of a fluid’s resistance to flow. Higher viscosity means greater resistance, which reduces the flow rate of the fluid under the same pressure gradient.
What is the primary application of dimensional analysis in fluid mechanics?
A Measuring fluid density
B Calculating fluid pressure
C Predicting fluid behavior
D Determining fluid temperature
Dimensional analysis is used to predict the behavior of fluids by identifying dimensionless groups (e.g., Reynolds number). It simplifies complex problems by reducing the number of variables.
What is the primary cause of water hammer in pipelines?
A Increase in fluid density
B Sudden valve closure
C Decrease in fluid velocity
D Increase in fluid temperature
Water hammer is a pressure surge caused by the sudden stoppage or change in direction of fluid flow, such as when a valve is closed abruptly. This creates a shock wave that can damage pipelines.
What is the primary function of a pump in fluid systems?
A Increase fluid pressure
B Decrease fluid velocity
C Measure fluid flow
D Store fluid
A pump is a mechanical device that transfers mechanical energy to the fluid, increasing its pressure and enabling it to flow through pipes or channels against resistance.