Emre Cenker

Question 1

What is specific volume?

Answer 1

Inverse of density

Question 2

What is compressibility of a fluid?

Answer 2

a measure of the relative volume change of a fluid or solid as a response to a pressure (or mean stress) change. Units of m²/N

v is volume

p is pressure

This is isothermal compressibility as it happens at constant temperture.

Question 3

What is the mach number when flow is incompressiable

Answer 3

m<0.1

Question 4

What is the ideal gas equation?

Answer 4

pv=Rt

R is the gas constant specific to that gas.

Question 5

How do you find the specific gas constant of a gas?

Answer 5

8314 J/kmol.K ÷ molecular weight (kg/kmol)

Question 6

How do you relate C_p and C_v?

Answer 6

C_p=C_v+R

C_p/C_v=υ

Question 7

What is the ratio of specific heats?

Answer 7

υ=C_p/C_v

Question 8

What is the speed of sound in a gas?

Answer 8

c=(υRT)^0.5

Question 9

What is the critcal velocity?

Answer 9

local speed of sound

Question 10

What is hs?

Answer 10

Stagnation enthalpy. Sum of local enthalpy and local kinematic energy in flow.

At stagation points.

Question 11

When do critical conditions occour?

Answer 11

When the local mach number M_i is 1

Question 12

What is the critical temperture ratio?

Answer 12

T_local is the general temperture

T_s is the stagnation temperture (velcity = 0)

Question 13

What is the critical pressure ratio?

Answer 13

Question 14

What is the critical density ratio?

Answer 14

Question 15

Mass flow rate for a chocked nozzle?

Answer 15

Mass low rate for a choked nozzle does not depend on pressure downstream once it falls below the critical pressure. This flow rate can be increased only by increasing the stagnation pressure ps upstream

Question 16

If gas is escaping from a nozzle, how can you find the result force on the tank it is leaving from?

Answer 16

There are 2 contrbutions to the force. The pressure difference and the change in momentum

CiM= mass flow rate * velocity

Pressure difference. A*(P_e-P_atm)

A is the cross sectional area of the nozzle. P_atm is the pressure of the atmosphere and P_e is the pressure at the nozzle which may be different to that of the stagnation pressure. Use critical pressure ratio to find.

Question 17

What happens to the stagnation temperture across a shock wave?

Answer 17

Remains constant

Question 18

What happens to temperture across a shock wave?

Answer 18

It increases

Question 19

What happens to density across a shock wave?

Answer 19

It increases

Question 20

What happens to pressure across a shock wave?

Answer 20

It increases

Question 21

What happens to stagnation pressure across a shock wave?

Answer 21

It decreases

Question 22

What happens to velocity and mach number across a shock wave?

Answer 22

They decrease.

Question 23

How can compressability be expressed in terms of density?

Answer 23

Question 24

What is the difference between a thermally and a calorfically perfect gas?

Answer 24

For a calorically perfect gas Cv , Cp, and γ are constants

For a thermally perfect gas Cv , Cp, and γ will depend on temperature

Question 25

What is the isentropic pressure temperature equation?

Answer 25

Question 26

What is the stagnation enthalpy equation?

Answer 26

Question 27

What is the isentropic density temperature ratio?

Answer 27

Question 28

What is the equation for the maximum chocked mass flow rate?

Answer 28

Question 29

What is the equation for the flow rate from a large area to a small one?

Answer 29

Question 30

What is the equation that gives the effect of a change in area on velocity?

Answer 30

Question 31

Are shock waves adiabatic?

Answer 31

Yes, though they aren’t reversiable so they aren’t isentropic

Question 32

What is the pressure ratio for shockwaves?

Answer 32

Question 33

With Rayleigh flow, what is the effect of heating on temperature?

Answer 33

The energy from heating goes into increasing the kinetic energy.