Fluids Final

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Homework 4

Continuity equations

A closed system is necessarily an isolated system

False

A closed system must be an isolated system

False

A control volume is fixed, identifiable quantity of mass that is isolated from its surroundings by boundaries

False

A fluid can be a liquid, but not a gas

False

A fluid is said to be static if there is no relative motion between adjacent particles

False

A frictionless flow is a viscous flow.

False

A fully-developed flow field in the x-direction means that the pressure is constant in the x-direction.

False

A large Reynolds number indicates that the flow is more likely to be laminar.

False

A magnetic force i an example of a surface force

False

A non-newtonian fluid has linear stress to strain relationship for a given applied shear stress

False

A streamline is a line joining all of the fluid particles that have passed through a fixed point in the flow field

False

A stress is a body force

False

A system cannot be both closed and isolated

False

A viscous fluid must flow very slowly when poured out of a can

False

All fluids are liquids

False

An incompressible fluid is expressed mathematically as rho = 0

False

An inviscid fluid is expressed mathematically as mu = 0 and rho = 0

False

An inviscid fluid is one where the viscosity is constant.

False

As you stir a pot of liquid mercury, you notice that it is hard to stir. This is, it resists your stirring action. This resistance comes entirely from the viscosity of the fluid

False

Density is an extensive property of a system since it is composed of mass and volume, which are both extensive properties

False

Ducts, nozzles, and diffusers are examples of external flows.

False

Enthalpy is an intensive property of a system

False

Flow through a duct system in a building is an example of a channel flow

False

For a steady flow situation, the timelines and streamlines are the same

False

For an unsteady flow situation, the curve representing the pathlines and streamlines are always the same, but the streamlines and streaklines are, in general, different

False

For an unsteady system, the volume flow rate in must equal the volume flow rate out of a control volume

False

For two-dimensional streamline coordinates, the positive n-direction points in a direction perpendicular to the flow direction and away from the convex side toward the concave side

False

For two-dimensional streamline coordinates, the positive n-direction points in a direction perpendicular to the flow direction and away from the convex side toward the concave side.

False

For two-dimensional streamline coordinates, the velocity component in the normal direction, Vn, is never zero (except at an inflection point in the curve)

False

Generally speaking, for an unsteady flow situation, only the pathlines and streaklines are the same

False

Geometric Similarity implies Kinematic Similarity.

False

Geometric similarity implies dynamic similarity.

False

Given an absolute pressure of 90 kPa and an atmospheric pressure of 100 kPa, the gage pressure is 10 kPa

False

Glycerin is an example of a non-newtonian fluid because its slow to pour out of a container

False

If a flow had friction, the total head (H) of the flow would increase.

False

If heat is added to a system and the temperature of a system increases, then the bulk kinetic energy of the system must always increase since the average speed of the molecules has increased

False

If the fluid is incompressible and the flow field is steady, then you can apply the steady Bernoulli equation between any two points on a streamline.

False

If we take the vorticity of the two-dimensional stream function, cz = vx - uy then it is always zero provided it is twice differentiable in x and y

False

Internal flows with viscosity generally have uniform velocity distributions.

False

Kinetic energy is an intensive property of a system

False

Liquid honey can be experimentally verified to be non-newtonian by showing that it pours more slowly than water out of a container

False

Mass is an intensive property of a system

False

Newton's second law of motion states that mass is conserved

False

Pipes with smaller diameters will have less head loss.

False

Stoke's Theorem states that the circulation around a closed contour is equal to the total viscosity within it.

False

Strictly speaking, a gas is not a continuum fluid because it is made up of discrete molecule with lots of space between them (the mean-free path); however, a liquid is a continuum because there is no space between the molecules in a liquid (they're touching)

False

The Hanquist number is a common dimensionless group, which is defined as the velocity of the flow divided by the speed of sound.

False

The Reynolds number is a ratio of pressure forces to viscous forces.

False

The concepts of closed and isolated in regards to a system are independent concepts

False

The continuity equation is derived from the conservation of momentum.

False

The continuity equation is the essential governing equation needed for studying head loss.

False

The continuity equation only applies to turbulent flows.

False

The continuity equation states that momentum is conserved

False

The drag coefficient has units of force.

False

The first law of thermodynamics states that the net force on an object is equal to the mass of the object multiplied by the acceleration of the object

False

The friction factor is only a function of the Reynold's number for turbulent flow.

False

The friction factor is only a function of the pipe roughness for a laminar flow.

False

The fundamental units for the British gravitational system are the slug, foot, and second

False

The fundamental units in the SI system corresponding to mass, length, and time are the gram, meter, and second

False

The hydrostatic equation would not be valid on the moon's surface where the acceleration due to gravity is less than that of earth's (assume the moon ha atmosphere)

False

The kinematic viscosity and dynamic viscosity must have the same dimensions since they both represent the stickiness of the fluid

False

The kinematic viscosity of a fluid is an extensive property of the fluid

False

The motion of a fluid particle can be decomposed into four basic components: kinetic energy, acceleration, momentum, and conservation of mass.

False

The static pressure is due to the bulk motion of the fluid.

False

The total head loss consists only of losses due to frictional effects in fully developed pipe flow.

False

The underlying principle that makes the hydrostatic equation valid is a balance between centripetal forces and gravity

False

Turbulent flow in a pipe is expected for Reynolds numbers less than 2300.

False

Velocity is an extensive property of a system

False

When you measure the air in your bike tire your tire gauge is measuring absolute pressure

False

Work is an extensive property of a system

False

Work is an intensive property of a system

False

You are stirring a pot of liquid mercury with a large paddle. You notice a strong resistance to the motion of the paddle from the liquid mercury. The resistance to the paddle's motion is solely due to the viscosity of the fluid

False

A benefit of differential analysis is that it can provide detailed information of the flow field (e.g. pressure and velocity distributions).

True

A closed system is also known as a control mass because no mass can escape the system

True

A control volume is a well-defined region in space that need not correspond to particular fluid particles

True

A dimension is a name given to any measurable quantity

True

A fluid in rigid-body rotation is experiencing shear forces, since the fluid particles are accelerating

True

A main difference between Euler's equations and Navier-Stokes equations is that Euler's equations are used for inviscid flows and Navier-Stokes are used for viscous flows.

True

A newtonian fluid is on the has a linear shear stress to shear strain-rate relationship

True

A normal stress on a static fluid's surface is also known as a pressure

True

A normal stress on a static fluid's surface is also known as pressure

True

A small Reynolds number indicates that the flow is more likely to be laminar.

True

A stress on a fluid particle's surface is defined as a force per unit surface area

True

A system is in steady state if its properties are independent of time

True

A system is said to be homogeneous if its properties are independent of space

True

A tangential stress on an object's surface is known as shear stress

True

A two-dimensional stream function is always constant along a streamline in steady flow.

True

A uniform flow field is independent of all space variables

True

All liquids are fluids

True

An example of fluid statics would be a thermometer

True

An irrotational flow has zero vorticity.

True

An isolated system is necessarily a closed system

True

An open system is a system where mass passes through the system

True

Any contact force that acts on an area of the surface of a fluid particle can be expressed as a stress

True

Archimedes's principle depends on the presence of a vertical pressure gradient

True

Archimedes's principle does not apply to "small" objects, such as the centimeter length scale of smaller. Assume the object is not so small that the continuum assumption fails to hold

True

Archimedes's principle states that a body immersed in a fluid is buoyed up with a force equal to the weight of the fluid displaced by the body

True

Consider a perfectly isolated piston-cylinder assembly that contains a gas. Take the gas to be our system. This system is an example of a closed isolated system

True

Crudely, a fluid is a substance that is easily deformable, and if poured into a container, it takes the shape of the container

True

Crudely, you can recognize a flowing liquid as laminar flow field if you inject a dye into the fluid and the flow looks very smooth and "glass-like"

True

Crudely, you can recognize when a fluid is turbulent if you inject a dye into the fluid and notice the flow field is very unsteady and "bubble" with lots of eddies swirling about, and the dye is quickly spread about and becomes unrecognizable in a short period of time

True

Dynamic similarity implies kinematic similarity.

True

Flow over a wing is an example of external flow

True

For a gas, the physical origins of the effect of viscosity on a small fluid particle of gas come from an exchange of momentum across the particle's boundary owing to random molecular motion plus a difference in bulk motion between the fluid particles and its environment

True

For a steady flow situation, the curve representing the pathlines, streamlines, and streaklines are all the same

True

For a steady system and incompressible flow, the volume flow rate in must equal the volume flow rate out of a control volume

True

For two-dimensional streamline coordinates, if the stream-lines are circular and the flow is steady, then the normal acceleration component, An, always points towards the concave side of the curve.

True

Gage pressure can be negative but absolute pressure can never be negative

True

Geometric similarity requires that the model and prototype be the same shape, and that all linear dimensions of the model be related to the corresponding dimensions of the prototype by a constant scale factor.

True

Head loss increases with flow rate

True

Head loss is typically due to friction.

True

If a fluid is assumed to be a continuum, the fluid's properties vary smoothly from point to point

True

If heat is added to a system and the temperature of a system increases, then the internal energy must always increase

True

If the fluid is incompressible and inviscid, and the flow field steady, then you can apply the steady Bernoulli equation between any two points on a streamline.

True

In a quasi-equilibrium process, the pressure in a system is approximately spatially uniform throughout the system at each moment in time

True

In a static fluid the only stresses present in the fluid are due to pressure

True

In order to properly define the temperature at a point in the flow field, we need the continuum assumption

True

In order to use the non-dimensionalization technique, you must know all of the governing equations and the boundary conditions for the system

True

In order to use the non-dimensionalization technique, you must know all of the governing equations and the boundary conditions for the system.

True

In the ideal gas model the internal energy, u, is a function of temperature alone

True

Inertial forces are fictitious forces that resists a change in velocity of an object.

True

Kinematic similarity implies geometric similarity.

True

Kinematic similarity is a necessary, but not sufficient, requirement for dynamic similarity.

True

Liquid honey and paint are examples of non-newtonian fluids

True

Loosely speaking, the viscosity of a fluid is the "stickiness" of the fluid

True

Mass is an extensive property of a system

True

Momentum is an extensive property of a system

True

Newton's second law of motion states that the net force on an object is equal to the mass of the object multiplied by the acceleration of the object

True

Paint is an example of a pseudoplastic in that it is a shear-thinning fluid

True

Particle linear deformation is related to volumetric strain

True

Particle rotation is related to angular velocity and vorticity

True

Pascal's law is one of the main underlying principles at work in hydraulic systems

True

Pascal's law states that if a gas is maintained at a constant temperature, then its volume will be inversely proportional to its pressure

True

Pascal's law states that pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and to the walls of the container

True

Pipe roughness, e, has units of length

True

Pressure is an intensive property of a system

True

Specific Volume is an intensive property of a system

True

Suppose the Buckingham Pi Theorem approach leads to one equation with one dependent non-dimensional parameter Π1, and two independent parameters, Π2 and Π3. Then, without knowing anything about the function itself, the resulting non-dimensional functional relationship is of the form: Π1=f(Π2,Π3).

True

Temperature is an intensive property of a system

True

The Buckingham Pi Theorem approach can be applied to situations where you don't know the explicit governing equations.

True

The Buckingham Pi Theorem approach requires experimental intervention to discover the functional relationship(s) between the parameters.

True

The Eulerian (or field) approach to describing fluid motion describes the flow field as a function of space and time

True

The Moody diagram relates pipe roughness, Reynold's number, and the friction factor.

True

The Reynolds number is a ratio of inertial forces to viscous forces.

True

The constant in the steady Bernoulli equation depends on the streamline that you're on (i.e., on the initial condition).

True

The continuum assumption for a fluid means that if the fluid was cut in half and in half again ad infinitum that the fluid's intensive properties, such as pressure and temperature, would be well defined in the limit at each point in space

True

The dynamic viscosity (mu) of a fluid has a fundamental SI units of kg/(m*s)

True

The equation F = 9.8m for the weight of an object is an example of a restrictive homogeneous equation

True

The equation W = int(P dV) is dimensionally consistent, where W = work, P = pressure, and V = volume

True

The equation v^2 = v0^2 + 2ax is dimensionally consistent

True

The equation x = t(v + 1/2at) is dimensionally consistent

True

The equation y = 4.9t^2 for a body falling from rest is an example of a restrictive homogeneous equation

True

The expansion of steam in a piston-cylinder is a situation well-suited for using a control volume analysis

True

The fundamental units in the SI system corresponding to mass, length, and time are the kilogram, meter, and second

True

The kinematic viscosity, when written in terms of the fundamental units, is independent of mass

True

The kinetic energy correction factor, α, is generally close to unity for turbulent flows.

True

The mathematical representation for an incompressible fluid is p (rho) is constant

True

The motion of a fluid particle can be decomposed into four basic components: translation, rotation, linear deformation, and angular deformation

True

The non-dimensionalization technique is most useful when you are able to identify characteristic properties of the flow field.

True

The parameters ρ, V, and L composing the inertia force term are idea candidates for repeated parameters since the inertia force shows up in so many non-dimensional parameters.

True

The shear-strain rate on an object is a measure of the object's rate of deformation to an applied shear force

True

The specific weight can be defined as g/v where g is gravity and v is the specific volume

True

The stagnation pressure (sometimes called total pressure) is essentially the sum of the static and dynamic pressures at a given location in the flow field.

True

The velocity field V = u(x,y)i + v(y)j is an example of planar flow

True

Turbulent flow is flow with fluctuating and disorderly motion.

True

Two flows are dynamically similar when the two flows have force distributions such that identical types of forces are parallel and are related in magnitude by a constant scale factor at all corresponding points.

True

Two flows are kinematically similar when the velocities at corresponding points are in the same direction and differ only by a constant scale factor.

True

Two-dimensional stream function is always constant along a streamline in steady flow

True

Volume is an extensive property of a system

True

Water flowing in a pipe is an example of an internal flow

True

Water flowing in a river is an example of a channel flow

True

When using the ideal gas law, you must use an absolute temperature scale

True

When you measure your body temperature in degrees Fahrenheit you are using a relative temperature scale

True


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