Energy Equation

Question 1

What is the accumulation rate of energy in the CV?

Answer 1

(Convection in - convection out) + (conduction in - conduction out) +( energy sources - rate of work done on CV by surface forces)

Question 2

What kind of energy is looked at in this equation?

Answer 2

Internal (e), kinetic (1/2(u^2 +v^2) and potential (gz)

Question 3

Model of flow is split into what two parts?

Answer 3

Transport terms and work terms

Question 4

What are transport terms?

Answer 4

Diffusion, convection and source

Question 5

What are work terms?

Answer 5

Shear, normal and pressure surface forces

Question 6

Express accumulation rate of energy as equation

Answer 6

d/dt(rho.dx.dy.E)=d/dt (rho(e+(u^2/2 +v^2/2) +gz))

Question 7

Individual accumulation rate term of E?

Answer 7

d/dt(rho.dx.dy.1.E)

Question 8

Individual convection term of E?

Answer 8

Due to fluid movement:

rho.u.E.dy.1

Question 9

Individual conduction term of E?

Answer 9

Due to diffusion across Cv boundaries:

qx.dy.1= -k.dT/dx.dy.1

Question 10

Individual source term of E?

Answer 10

Due to fission, combustion etc:

rho.d.dx.dy.1

Question 11

What is the dissipation function?

Answer 11

2.mu[(du/dx)^2+(dv/dy)^2 +1/2(du/dy +dv/dx)^2]

Question 12

What are assumptions of phi (dissipation function)?

Answer 12

Important in compressible flows, Ma>0.3. Contributes to viscous heating of fluid.

Question 13

Express the thermal energy source term

Answer 13

rho.S.dx.dy

Question 14

Define the thermal energy source term

Answer 14

Heat flux due to volumetric heating rate from endo/exo thermic reactions.