Fluid Mechanics Midterm 1 Review

The absolute pressure is measured relative to a datum, where the value of the absolute pressure is _____ bar

0

One stoke equals _____ m^2/s.

0.0001

Numerically, one poise equals _____

0.1 N⋅s/m^2

Rank the general procedural steps involved in the mathematical modeling of a physical problem or a phenomenon

1. Identify important variables that affect the problem. 2. Make reasonable assumptions and approximations. 3. Apply relevant physical laws and principles. 4. Formulate the problem mathematically. 5. Apply applicable solution techniques and boundary and initial conditions. 6. Interpret the results obtained.

Arrange the following such that the flow with the lowest Mach number is on the top row and the flow with the highest Mach number is on the bottom row

1. Subsonic 2. Sonic 3. Supersonic 4. Hypersonic

Over the free surface of a liquid exposed to the atmosphere, the pressure is approximately equal to _____

1.01 bar

Identify the equivalent value of one bar in terms of Pascal

10^5 Pa

Express 1 standard atm of pressure in English system units

14.696 psi

Standard atmospheric pressure is defined as the pressure produced by a column of mercury _____ under standard gravitational acceleration

76.0 cm in height at 0°C

The equivalent value of one atm in units of torr is _____ torr

760

Turbulent Flow

A highly disordered fluid motion that typically occurs at high velocity and is characterized by velocity fluctuations

Fluid (definition)

A substance in the liquid or gas phase that continually deforms under an applied shear stress is known as a fluid

Identify the applications in which fluid mechanics plays a major part

Aircraft, wind turbines, boats

Fluids that can resist a finite shear stress but deform continuously when the shear stress exceeds the yield stress are called _____ fluids

Bingham plastic fluids

Recognize the examples of non-Newtonian fluids

Blood Liquid plastic

Solid (deformation)

Can resist an applied shear stress by deforming

Fluid (deformation)

Deforms continuously under the influence of shear stress

Differential Equations

Differential equations provide precise mathematical operations by representing the rates of change as derivatives

Internal flow

Flow of a fluid that is bounded by solid surfaces

External flow

Flow of an unbounded fluid over a surface

What are Newtonian fluids?

Fluids whose shear stress is linearly proportional to the velocity gradient

Forms a Fluid can take

Gas, Liquid

Molecular Properties of Fluids

Gases cannot form free surfaces when kept in an open container (liquids can) Gases have a less cohesive force compared to liquids Liquids have a less cohesive force compared to solids

Recognize the Newtonian fluids

Gasoline Water

Fluids for which the rate of deformation is proportional to the shear stress are called _____

Newtonian fluids

The SI units of the coefficient of viscosity are _____

Newton⋅second/(meter)^2 kilogram/meter−second pascal⋅second

Identify the unit of dynamic viscosity that is used commonly in engineering

Poise

Consider a fluid flowing between two flat parallel plates. The lower plate is fixed and the upper plate is subjected to a force F. Under equilibrium conditions, the equal and opposite forces acting on the plate-fluid interface is proportional to which of the following terms? (Check all that apply.)

Shear stress Area of the plate Viscosity

_____ is defined as the ratio of the density of a substance to the density of some standard substance at a specified temperature.

Specific Gravity

The weight per unit volume of a substance is called the _____

Specific Weight

In the context of specific gravity, identify the true statements

Specific gravity is also known as relative density. Specific gravity is a dimensionless quantity.

Solid

Stress is proportional to strain

Fluid (stress)

Stress is proportional to strain rate

Identify the properties of fluids that relate the volume changes to the changes in pressure and temperature

The bulk modulus of elasticity (k) The coefficient of volume expansion (β)

Compressible Flow

The density of a flowing fluid changes significantly.

Incompressible Flow

The density of a flowing fluid remains nearly constant throughout.

Cohesive Force

The force existing between the molecules of a fluid that binds them together

As shown in the figure, τ represents shear stress and α represents shear strain. If the shear stress is proportional to shear strain, how is the friction force related to the shear strain?

The friction force is proportional to the shear strain

A Principle of Fluid Mechanics

The natural rise of ground water to the tops of trees

The force a flowing fluid exerts on a body in the flow direction is called the _____ force

drag

It is a common observation that a fluid contracts when more pressure is applied on it and expands when the pressure acting on it is reduced. That is, fluids act like a(n) _____ with respect to pressure

elastic solid

A fluid flow is said to be natural or forced, depending on _____

how the fluid motion is initiated

A flow is said to be one-, two-, or three-dimensional _____.

if the flow velocity varies in one, two, or three primary dimensions, respectively.

Fluid flow regions in which frictional effects are negligible are called _____ flows

inviscid

A large value of coefficient of compressibility (κ) of a fluid indicates that a _____ is needed to cause a small fractional change in volume

large change in pressure

The SI units of dynamic viscosity are _____

newton−second/(meter)2

A fluid in direct contact with a solid surface sticks to the surface and there is no slip. This is known as the _____condition

no-slip condition

The counterpart of pressure in solids is _____

normal stress

Fluids for which the apparent viscosity decreases with the rate of deformation are referred to as _____ fluids

pseudoplastic

The image shows the forces acting on a surface by a fluid flow. The stress created by the force Ft is the _____

shear stress

Density is defined as mass per unit volume. The reciprocal of density is called ____

specific volume

The density of a substance is most likely dependent on _____

temperature

The speed of sound in a specified ideal gas is a function of _____ alone

temperature

A flow is classified as being compressible or incompressible, depending on _____

the level of variation of density in the flow

Speed of sound is defined as _____

the speed at which an infinitesimally small pressure wave travels through a medium

A flow can be approximated as _____-dimensional when the aspect ratio is large and the flow does not change appreciably along the longer dimension

two

The term _____ implies no change with location over a specified region

uniform

The negative gage pressure is also called _____ pressure.

vacuum

The coefficient of volume expansion is the property of a fluid that represents the _____

variation of the density of a fluid with temperature at constant pressure

The no-slip condition is due to the _____ of the fluid

viscosity

In the formula γ=ρg where the symbols have standard notations, ___ is the specific weight.

γ

At what situation, the center of pressure coincides with the centroid of the plate?

The plate is immersed horizontally to the free surface.

What is Pascal's law?

The pressure applied in a closed fluid system is equally transmitted in all directions.

Experimental Modeling

The type of modeling technique that is expensive, time-consuming, and sometimes impractical

A fluid deforms continuously under the influence of shear stress, no matter how small.

True

For fluids at rest, the shear stress is zero, and the pressure experienced is due only to the normal stress.

True

The coefficient of compressibility of a fluid cannot be negative

True

The continuum idealization is valid as long as the size of the system is large relative to the space between the molecules

True

Identify the factors on which pressure in a fluid at rest depends

Vertical distance Density of the fluid

Laminar Flow

When the fluid motion is highly ordered and characterized by smooth layers of fluid

A large value of coefficient of volume expansion means _____

a large change in density with temperature

The actual pressure at a given location in a flow is called the _____ pressure

absolute

The amplitude of the ordinary sonic wave is very small and does not cause any appreciable change in the pressure and temperature of the fluid. Therefore, the propagation of a sonic wave is _____

adiabatic (heat doesn't enter or leave) and very nearly isentropic (equal entropy)

Atmospheric pressure is often referred to as _____ pressure

barometric

When a plane surface is immersed in a fluid, the total hydrostatic force is assumed to act on the _____

center of pressure

In the equation κ=−V(∂P∂V)T, κ represents the _____. ∂P is a small change in the pressure exerted on the fluid, V is the volume of the fluid, and ∂V is a small change in the volume of the fluid. The temperature of the system is held constant

coefficient of compressibility

The variation of the pressure of a fluid with density at constant temperature is known as the _____.

coefficient of compressibility

The fraction of volume change of a fluid that corresponds to a small temperature change of ΔT at a constant pressure is given by _____

coefficient of volume expansion (β) × ΔT

A water drop remains spherical during free fall but adopts a hemispherical shape when it is sitting on the ground. In the case of a mercury droplet, the shape remains spherical irrespective of whether it is in mid-air or on the ground. The molecular property that is responsible for both the above cases is _____.

cohesion

In fluid mechanics, the _____ allows us to treat properties as point functions and to assume that the properties vary continually in space with no jump discontinuities

continuum idealization

At high altitudes, a given volume of air will contain less oxygen. This is due to the decrease in the _____ of air

density

The pressure difference between any two points 1 and 2, dP/dz=−ρg can be determined by integration only when the variation of ______ with elevation is known in a fluid at rest

density

If a substance is assumed incompressible, the properties considered as constant is ___

density specific volume

Fluids for which the apparent viscosity increases with the rate of deformation are referred to as _____ fluids.

dilatant