AAE 333 EXAM 1
Match the flow regimes to the type of flow they represent.
- a. b. c. d. M < 0.3 - a. b. c. d. M < 1 - a. b. c. d. M = 1 - a. b. c. d. M > 1 a. Sonic flow b. Incompressible flow c. Supersonic flow d. Subsonic flow BDAC!!!!!!!!!!!!!!
Consider the vector field . The curl of is given by
1 i + j + k - ( i + j + k ) ??????????????
According to the Buckingham Pi Theorem, the number of fundamental dimensions required to describe the physical variables in a process is 4. The number of physical variables in the relation is 7. What is the number of dimensionless products (Π products) needed to re-express the physical relation?
3
Assume the number of variables required to describe a particular physical process is 7, and that the number of fundamental dimensions needed to describe those variables is 4. From the Buckingham Pi Theorem, what is the number of dimensionless products (Π products) needed to re-express the physical relation?
3
how are the reference areas and lengths are defined for a streamlined body? bluff body
3D: s= bxc 2D: s=c Bluff bodies 3D s=D*L projected frontal area 2D s=D (length)
Consider the momentum conservation equation given by What does the term represent?
Body forces
The thin viscous region adjacent to a body in a flow field where dissipative effects are included is called _____.
Boundary layer
The transfer of heat from a hotter region to a colder region by random molecular motion is called thermal ______ .
Conduction
If the mean free path, λ is orders of magnitude smaller than the scale of the body measured by d, then the flow is called ____.
Continuum flow
Pressure coefficient is defined as
Cp = (p-p_infinity)/(q_infinity)
The time rate of change of the volume of a moving fluid element, per unit volume represents the _____ of the velocity field.
Divergence
The momentum equations or inviscid flows are called the _____ equations.
Euler
Reynolds number is defined as
FALSE!!!
True of false: for a blunt body, drag is mostly due to friction? Explain why.
FALSE: Bluff bodies have large curvatures (dy/dx), so most of the drag is pressure drag
True or false: The vector field V=(x2,y2,-(x+y)z2) is divergenceless.
FALSE: DIV(DOT)V-> = 2X+2Y-2XY-2YZ =/= 0
A control volume has to be fixed in space with the fluid moving through it and it may not move with the fluid such that the same fluid particles are always inside it.
False
A body immersed in a fluid will experience a force only if there is a relative motion between the body and the fluid.
False???????????
what is continuum hypothesis? how is it used
Fluid is a continuous medium described by properties such as density pressure. which are continuous functions of space
Give the definition of Reynolds number and explain its physical meaning
It is the ratio of inertial to viscous forces.
Hydrodynamics refers to the flow of ____.
Liquids
A flow can be treated as an incompressible flow when ________________
M < 0.3
How flows are classified by the value of freestream Mach number?
M < 0.3 -> Incompressible flow, M < 0.8 -> Subsonic flow, 0.8 < M < 1.2 -> Transonic flow, M > 1.2 -> Supersonic flow, M > 5 -> Hypersonic flow
Which of these options has all correct combinations?
Mass conservation - Scalar equation, Momentum conservation - Vector equation, Energy conservation - Scalar equation?????????
what are the three physical principles behind the conservation laws?
Mass is neither created nor destroyed, force is change in momentum over time, mass is conserved.
What are the SI units of shear stress?
N/m^2
THAT OF VISCOUS FLOWS ARE CALLED THE______________EQUATIONS
Navier-Stokes
Consider the energy equation given by The term represents
Net rate of flow of total energy across the control surface S.??????
Consider the energy equation given by The term represents
Rate of work done on the fluid inside v due to body forces.?????????
When a force is applied tangential to the surface of a ____, it will experience a finite deformation and the shear stress will usually be proportional to the amount of the deformation.
Solid
If an airfoil is inclined at a high incidence angle to the flow, then the boundary layer will tend to separate from the top surface and a large wake is formed downstream. Such a separated flow is a characteristic of a flow-field over a ____ airfoil.
Stalled
How is curl used in 333
Stokes Theorem
Consider the energy equation given by The term represents
THIS IS WRONG :) Rate of work done by the fluid inside the control volume v due to the pressure force on S.
Consider the momentum conservation equation given by What does the term represent?
The time rate of change of momentum contained inside the control volume.
The equation is called the Hydrodynamic equation.
True???????????
A control volume is _____ region of the flow.
a finite
define fluid
a fluid is a substance that deforms continuously when a shear force is applied
What is a fluid?
a substance that deforms continuously when a shear force is applied
Which of these is not one of the consequences of flow similarity?
a. The streamline patterns are geometrically similar for the two flows. b. The non-dimensional pressure and temperature distributions are the same for both flows. c. The lift coefficients obtained are the same. d. None of these.??????????????
The heat transferred to or from the fluid can be visualized as volumetric heating of the fluid inside the control volume and this could be due to ________.
a. absorption of radiation originating outside the system b. local emission of radiation by the fluid itself c. chemical combustion processes taking place inside the control volume d. thermal conduction across the control surface e. mass diffusion across the control surface. ALL OF THE ABOVE
how do you calculate speed of sound
a= (gamma*R*T)^.5 Gamma- specific heat ratio R- specific heat constant 287 T- Temperature kelvin
To minimize aerodynamic heating we need a _____ body.
blunt
The weight of fluid displaced by an object that is immersed in the fluid is equal to the force of___.
buoyancy
The weight of fluid displaced by an object that is immersed in the fluid is called the force of___.
buoyancy?????????
Consider the scalar . The gradient of T is given by
c. (2ax + by) i + bx j + c k???????????????
If a gas is ________, then the internal energy satisfied the relation , where cv is the specific heat at constant volume and T is the temperature.
calorically perfect
Functional relationship for drag coefficient
cd= (D)/ .5*q*A for an infinite wing, A = C*1
The transfer of heat from a hotter region to a colder region by random molecular motion is called thermal ______ .
conduction
For incompressible flow, the _________ are sufficient tools to solve for the primary flow-field variables.
continuity and momentum equations
The time rate of change of the volume of a moving fluid element, per unit volume represents the _____ of the velocity field.
divergence
A body immersed in a fluid will experience a force only if there is a relative motion between the body and the fluid. (t or f)
false
A control volume has to be fixed in space with the fluid moving through it and it may not move with the fluid such that the same fluid particles are always inside it. (t or f)
false
t/f for a bluff body drag is mostly due to friction
false. bluff bodies ahve large curvatures so most of teh drag is pressure drag
What is the continuum hypothesis in fluid mechanics and how it is used?
fluid is a continuous medium described by properties such as density, pressure, etc. which are continuous functions of space.
The time rate of change of momentum is called ____.
force
how is gradient used in 333
gradient theorem directional derivative
What balances the pressure gradient in the hydrostatic equation
gravity balances the pressure gradient
For what flow is the temperature in the shock layer high enough for chemical reactions to occur in the air?
hypersonic flow
For which of these flows is the temperature in the shock layer high enough for chemical reactions to occur in the air?
hypersonic flow
A flow that is assumed to involve no friction, thermal conductivity or diffusion is called ____ flow.
inviscid
The SI units of mass flux are ____.
kg / (m2 s)
The SI units of mass flux are ____.
kg / (m^2 s)
What are the SI units for the absolute viscosity coefficient (μ)?
kg / m s
What are the SI units for the absolute viscosity coefficient (μ)?
kg/ m s
How does a liquid and gas differ? How are they the same
liquids-close molecules, constant volume gas-far molecules, takes shape of container
How is divergence used in 333
mass conservation divergence theorem
The phenomenon where friction causes the infinitesimally thin layer of air molecules immediately adjacent to the body surface stick to the surface is called the _____ condition.
no slip
The phenomenon where friction causes the infinitesimally thin layer of air molecules immediately adjacent to the body surface to stick to the surface is called the _____ condition.
no slip
what are the two basic aerodynamic forces
pressure and shear stress
For a blunt body, most of the drag is due to _____.
pressure drag
For a blunt body, most of the drag is due to _____.
pressure drag?????????????
Reynolds Number
ratio of inertial forces to viscous forces (inertial forces)/ (viscous forces)
Physical meaning of reynolds number
represents the ratio of intertial to viscous forces
For the perfect gas equation of state expressed as , R represents
specific gas constant????????
If Mach number is defined as , refers to
speed of sound
If Mach number is defined as M=v/a, a refers to
speed of sound
If an airfoil is inclined at a high incidence angle to the flow, then the boundary layer will tend to separate from the top surface and a large wake is formed downstream. Such a separated flow is a characteristic of a flow-field over a ____ airfoil.
stalled
One way of expressing the continuity equation is: This form is valid for _____ flows.
steady, unsteady, viscous, inviscid, compressible and incompressible
Consider a vehicle flying through the atmosphere. If the flow over the vehicle is characterized by the presence of shock waves at the nose of the vehicle, across which the flow properties change discontinuously, as what type of flow would the freestream be classified?
supersonic flow
What kind of flow is characterized by the presence of shock waves across which the flow properties and streamlines change discontinuously?
supersonic flow
Two flows will be dynamically similar if _____.
the bodies and any other solid boundaries are geometrically similar and the similarity parameters are the same
Give definition of mach number and explain its physical meaning
the number is the ratio of the speed of the object to the speed of sound . Mach number represents the type of flow and compressibility effects. m</3 incompressible. M<subsonic M>1 supersonic, m>6 hypersonic
Flows at high Reynolds numbers are often studied by dividing the flow into two regions, where the influence of friction, thermal conduction and diffusion is limited to a very thin region adjacent to the surface and the remainder of the flow is treated as an inviscid flow. (t or f)
true
T/f: for a streamlined body, drag is mostly due to shear stress
true. the expression has the term dy/dx multiplied by pressure this term is very small for a streamlined body due to which teh pressure term is almost negligble and drag is mostly due to shear stress
A flow where the flow-field variables at any given point are changing with time is called _____.
unsteady flow
We need to measure the ______ using a Pitot rake in order to calculate the drag of a two dimensional body in a wind tunnel.
velocity distribution?????????
Give the definition of the center of pressure
x(cp)' = M(LE)' / N'
Consider the vector field . The divergence of is given by
y + z + x i + j + k 0?????????
