Hydraulics RATs

The Reynolds number (Re = ρV l/μ) might be used to analyze problems when which of the following forces are dominant? A. Inertia force B. Viscous force C. Pressure force D. Surface tension force

AB

For laminar pipe flow, which of the following would increase the flow rate? A. Change to a pipe with a large diameter B. Increase the pressure at the start of the pipe C. Raise the end of the pipe D. Change to a fluid with a higher viscosity

AB

Dimensional analysis can have which of the following benefits? A. Reduce the number of variables in an experiment. B. Make it easier to interpret the results of an experiment. C. Make it cheaper to conduct an experiment. D. Eliminate the need to conduct an experiment.

ABC

The material derivative can be used to describe which of the following? A. The acceleration field. B. Change in temperature of a particle moving through a temperature field. C. Change in snowfall rate seen from a car driving through a snow storm. D. Fluid velocity profile across a pipe cross-section.

ABC

When the Bernoulli equation is written in terms of heights called heads, which of the following terms are included? A. The elevation head, z. B. The pressure head, p/γ. C. The velocity head, V^2/2g. D. The kinematic viscous head, ν/V .

ABC

Work transfer across a control surface can be achieved through which of the following? A. Rotating shafts, e.g., turbines and pumps. B. Normal stresses, e.g., pressure of fluid entering a control volume. C. Tangential stresses, e.g., shear stresses of fluid exiting a control volume. D. Convection, e.g., heat transfer due to a temperature difference.

ABC

When pressure is expressed as a head, such as the height of a column of mercury, it can have which of the following units? A. Inches, in. B. Pounds per square inch, psi. C. Meters, m. D. Newtons per square meter, N/m2. E. Pascals, Pa.

AC

All fluids (liquids and gases) obey a no-slip condition, meaning: A. The fluid "sticks" to any solid boundaries. B. The fluid doesn't "stick" to any solid boundaries. C. The fluid velocity is zero at stationary solid boundaries. D. The fluid velocity is the same as the velocity at moving solid boundaries.

ACD

Which of the following are examples of control volumes? A. The outflow pipe from a wastewater treatment plant. B. Treated wastewater discharged into a river. C. A pulse of water flowing downriver from a recent rain event. D. The dammed reservoir into which the river flows.

AD

The buoyant force: A. Is the resultant fluid force acting on a submerged or floating body. B. Has a magnitude equal to the weight of the body. C. Has a direction dependent on the shape of the body. D. Acts through the center of buoyancy. E. Acts through the center of mass of the displaced volume.

ADE

The method of inspection is less structured than the method of repeating variables, but it can be used to determine the same pi terms for a given physical relationship.

True

The method of repeating variables provides a simple, systematic technique for determining the pi terms for a given problem.

True

The pressure at a point in a fluid at rest is independent of direction.

True

The specific volume ν and specific weight γ have units, but the specific gravity SG is unitless.

True

Viscosity is a measure of the ease of motion within a fluid; the higher the fluid's viscosity, the more resistant it is to motion.

True

The Bernoulli equation can be written so each term has units of energy per unit mass, so its terms can be related to types of energy for the fluid particle.

False, change units of energy to units of force, unit mass to unit area, types of energy to types of pressure

The external forces in the linear momentum equation have signs that follow the convention: A. The sign is positive if the force acts in the positive coordinate direction. B. The sign is positive if the force acts upward. C. The sign is positive if the force acts out of the control volume. D. The sign is positive if the force acts into the control volume.

A

The buoyant force has a magnitude equal to the weight of the submerged or floating body.

False - change submerged or floating body to displaced fluid.

A system is a volume in space through which a fluid may flow.

False - change system to control volume

The center of pressure for a submerged plane surface acts through the center of volume of the pressure prism.

True

The dimensionless entrance length depends on the Reynolds number for both laminar and turbulent flow.

True

The height of capillary rise is a function of the surface tension σ and specific weight γ of the fluid.

True

The material derivative is a way to describe the changes experienced by a Lagrangian particle as it moves through an Eulerian flow field.

True

The mechanical energy equation is an extended form of the Bernoulli equation to include the shaft work and losses.

True

The net mass flow into or out of a control volume must be zero.

False - must be matched by net accumulation or depletion.

Which of the following are units? A. Length B. Hour C. Kilogram D. Force E. Newton

BCE

The study of fluid kinematics deals with the fluid flow properties and the forces causing the flow.

False - remove "and the forces causing the flow", or change kinematics to dynamics

For laminar flows, the velocity profile is parabolic with maximum velocity at the pipe wall and minimum velocity at the pipe centerline.

False - switch wall and centerline OR switch minimum and maximum

The Bernoulli Equation is based on the assumptions that the flow is steady, compressible, and viscous.

False, change compressible to incompressible and viscous to inviscid.

When viscous effects are ignored, which of the following may vary along a fluid streamline? A. Energy line. B. Hydraulic grade line. C. Elevation head. D. Velocity head. E. Pressure head. F. Friction head.

BCDE

Which of the following is an example of minor head loss hL,minor: A. Viscous effects in a straight pipe B. Flow through a valve C. Flow through a pipe bend D. Flow entering (or exiting) a pipe from (or to) a tank E. Flow through a sudden contraction or expansion

BCDE

For the external forces in the linear momentum equation (such as the forces due to pressure, weight, or reactions), their sign is positive if the force acts out of the control volume.

False - change to 'force acts in the direction of the positive coordinate direction'

The continuity equation can be used to equate velocities at two points in a confined flow.

False - change velocities to flowrates

Free jets are open to the atmosphere, so we can assume their fluid velocity is zero.

False - change velocity to pressure

Flow is impossible in the direction parallel to a streamline.

False - change parallel to perpendicular

The dot product V.n is a way to find the velocity component that is parallel to the control surface.

False - change parallel to perpendicular

When a solid is acted on by any shearing stress, it will deform continuously.

False - change solid to fluid

The pressure in a fluid is independent of direction, even when shearing stresses are present.

False - add 'not' in 'are present'

The major head loss hL, major is always larger than the minor head loss hL, minor.

False - can be larger

A U-tube manometer can be used to measure the difference in fluid densities between two containers in a given system.

False - change densities to pressures

If we use experimental data to determine the specific relationship between dimensional variables, then we can re-use that relationship for flows with other fluids, geometries, etc.

False - change dimensional to dimensionless, change other to similar

Linear momentum is independent of direction; we can write only one equation for conservation of linear momentum for any system and control volume.

False - change independent to dependent, change 'one equation' to 'up to three equations'

If an unknown fluid has a lower viscosity than water, then it will be less likely to deform or "flow."

False - change lower to higher OR less to more

The physical system for which the predictions are to be made is called the model.

False - change model to prototype

The lines that are normal to the velocity vectors throughout the flow field are called streamlines.

False - change normal to tangent or parallel

A control volume should be selected so its surfaces align with locations where we either know or want to know information about the flow.

True

If the pressure is greater than atmospheric pressure, then the pressure force on a control surface is directed into the control volume, regardless of the direction of the flow.

True

In most pipe flow problems, it is best to start with the extended Bernoulli equation, and then account for all of the head losses due to the pipe system components.

True

Many of the conservation equations can be derived from the Reynolds transport theorem, which relates systems concepts to control volume concepts.

True

Most liquids can be considered as incompressible because their densities vary only slightly, even over large vertical distances.

True

The Bernoulli equation can be derived from Newton's second law, so its terms can be related to forces and accelerations for the fluid particle.

True

The Reynolds transport theorem allows us to shift between systems and control volume approaches.

True