Quiz Flashcards
The Conservation of mass (continuity) equation may be derived from the GENERAL TRANSPORT EQUATION by setting the transport variable, phi, and source term, S respectively
phi = 1
S= 0
In Fick’s law of diffusion the units of the diffusion coefficient are:
m^2/s
In an non-Newtonian fluid the shear stress is directly proportional to:
The Strain rate to the power of an exponent not equal to 1
In the Energy Equation the term responsible for viscous heating is often called:
The dissipation function
An example of a TRUE SOURCE TERM in the energy equation is:
Nuclear Fission
In the derivation of the Energy Equation the RATE OF WORK acting on the control volume surface may be express as the product of:
Force and Velocity
A model of the flow which considers a fluid element fixed in space
Eulerian
An example of a CONSTITUTIVE RELATIONSHIP is
Stokes hypothesis
The constant of proportionality in Fick’s law of Diffusion is
The mass diffusivity
The following term
duu/dx
can be used to describe
The convection of acceleration
A definition of fully developed, laminar pipe flow is as follows:
All axial gradients are zero except the pressure gradient
In the General Transport Equation the operator GRAD does the following
Converts a scalar to a vector
In the Navier-Stokes equation, a NORMAL STRESS term contains the following (where the symbols have their usual meaning)
du/dx
What does the following term represent?
mu/rho (d^2u/dx^2)
The diffusion of u in the x direction for constant viscosity
The Stokes’ relatioship for shear stress and strain-rate may be express as
txy = tyx = mu(du/dy+dv/dx)
The equality:
txy = tyx
Is true because of:
Conservation of angular momentum
Fourier’s law of conduction may be express as:
q = - kA(dT/dx)
Where the negative sign is necessary in order to
Ensure that the 2nd law of thermodynamics is upheld.
The GENERAL TRANSPORT EQUATION consists of the following terms:
Transient + Convection + Diffusion + Source
TRANny CONVicts DIe SOURly
An example of a non-Newtonian fluid is:
Blood
∇.u = 0
may be expanded into what form?
du/dx + dv/dy + dw/dz = 0
∇.u = 0
Describes what?
The steady state continuity equation for incompressible flow
An example of a Newtonian fluid is
Water, Air, Alcohol, Milk, Glycerol, Thin Motor Oil
Define Newtonian Fluid
A fluid that all viscous stresses arising in the flow are, at all points, linear to the local strain rate and rate of change of its deformation over time.
In the GENERAL TRANSPORT EQUATION what does phi mean?
Mass, Momentum, Energy, Species Concentration.
MASSive MOMENTs ENERGise SPECky Cunts
What does the transient terms in GTE mean?
Accumulation Rate of the variable, phi.
Can be expressed in terms of Convection, diffusion and source terms.
What does The Convection Terms in GTE depend on?
Convection Term only becomes important when the variables in partial derivatives vary in direction
Convection Terms as “equations” are:
d(rho*u^2)/dx
d(rhovu)/dy
d(rhoue)/dx
Diffusion process is characterised by a dependency on what?
a gradient of a particulat variable and occurs at a molecular level.
State Fourier’s Law of Heat Conduction.
q = -k (dT/dx)
What does phi represent in the energy equation?
Dissapation function
Why is the dissipation function important in compressible flows?
Contributes significant viscous heating of fluid
Where does viscous heating also occur?
Incompressible flows, lubrication of bearings and journals
What units does species, M have?
kg substance/ kg mixture
KgA/Kg(A+B
Is species concentration scalar or vector?
Scalar
what four terms make up the species concentration equation?
transient, convection, diffusion, source
TRANny CONVicts Die SOURly
What is an example of a constitutive or particular relationship?
Stoke’s hypothesis
What is Fick’s Law of diffusion?
Thermal energy diffusing from high concentration regions to low concentration regions.
What can a species be quantified in terms of?
Mass density and molar concentration.
What are the units for mass density and molar concentration?
kg/m^3 and Kmol/m^3
what is the relationship between mass density, molar concentration and molar mass?
phi i = Mi * ci
What are the units of the diffusion coefficient?
m^2/s
What are the units of volumetric source (na) of phi A
kg/s/m^3
What is heat transfer?
Heat transfer is thermal energy in transit- as a result of temperature differences
What is momentum transfer?
Acceleration or deceleration of fluid particles as a result of motive or retardive forces.
What is mass transfer?
Mass transfer is mass in transit as a result of concentration differences?
Phase change example?
Water evaporating: Energy is taken from the water droplet (cooling) allowing it to break liquid bond, this energy turns into laten heat as the liquid into a gas, this energy is released as the gas is condensed back into a liquid
Is the model Eularian or Lagrangian?
Eulerian: Fixed in space
Lagrangian: Moves in space
(abcdEFg…LMnop…)
delta phi = ?
Net convection + net diffusion + source/sink +effects on CV surface (shear/normal stresses)
What are the four physical fundamental principles?
Mass, Energy, Species Concentration, momentum
What forces act on the CV to allow us to apply momentum equation?
Body forces (gravitational, magnetic)
Surface Forces ( Shear and normal stresses pushing and tugging).
What type of diffusion occurs and what direction is it in when shear stress are present on 2d body?
Diffusion of momentum in the high to low shear direction (look for terms du/dy, dv/dx etc.)
What does the term
u*du/dx
represent?
Convection of u in x direction
What does the term
v*du/dy
represent?
Convection of u in the y direction
What does the term
u/p(d^2u/dx^2)
represent?
Diffusion of u in the x direction due to normal stresses for constant velocity
What does the term
u/p(d^2u/dy^2)
Diffusion of u in the y direction due to shear stresses for constant velocity.
