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