Emre Cenker Flashcards
What is specific volume?
Inverse of density
What is compressibility of a fluid?
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.
What is the mach number when flow is incompressiable
m<0.1
What is the ideal gas equation?
pv=Rt
R is the gas constant specific to that gas.
How do you find the specific gas constant of a gas?
8314 J/kmol.K ÷ molecular weight (kg/kmol)
How do you relate Cp and Cv?
Cp=Cv+R
Cp/Cv=υ
What is the ratio of specific heats?
υ=Cp/Cv
What is the speed of sound in a gas?
c=(υRT)0.5
What is the critcal velocity?
local speed of sound
What is hs?
Stagnation enthalpy. Sum of local enthalpy and local kinematic energy in flow.
At stagation points.
When do critical conditions occour?
When the local mach number Mi is 1
What is the critical temperture ratio?
Tlocal is the general temperture
Ts is the stagnation temperture (velcity = 0)
What is the critical pressure ratio?
What is the critical density ratio?
Mass flow rate for a chocked nozzle?
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
If gas is escaping from a nozzle, how can you find the result force on the tank it is leaving from?
There are 2 contrbutions to the force. The pressure difference and the change in momentum
CiM= mass flow rate * velocity
Pressure difference. A*(Pe-Patm)
A is the cross sectional area of the nozzle. Patm is the pressure of the atmosphere and Pe is the pressure at the nozzle which may be different to that of the stagnation pressure. Use critical pressure ratio to find.
What happens to the stagnation temperture across a shock wave?
Remains constant
What happens to temperture across a shock wave?
It increases
What happens to density across a shock wave?
It increases
What happens to pressure across a shock wave?
It increases
What happens to stagnation pressure across a shock wave?
It decreases
What happens to velocity and mach number across a shock wave?
They decrease.
How can compressability be expressed in terms of density?
What is the difference between a thermally and a calorfically perfect gas?
For a calorically perfect gas Cv , Cp, and γ are constants
For a thermally perfect gas Cv , Cp, and γ will depend on temperature
What is the isentropic pressure temperature equation?
What is the stagnation enthalpy equation?
What is the isentropic density temperature ratio?
What is the equation for the maximum chocked mass flow rate?
What is the equation for the flow rate from a large area to a small one?
What is the equation that gives the effect of a change in area on velocity?
Are shock waves adiabatic?
Yes, though they aren’t reversiable so they aren’t isentropic
What is the pressure ratio for shockwaves?
With Rayleigh flow, what is the effect of heating on temperature?
The energy from heating goes into increasing the kinetic energy.
