Compressible Fluid Dynamics Flashcards
What is a high velocity gas?
A gas moving with a velocity in excess of approximately 100 meters per seconds.
What is the ideal gas law?
It is the equation of state fro ideal gases.
What is an equation of state?
A relationship that predicts the state from a set of two other independent properties.
What is the specific gas constant?
Its the ratio of the universal gas constant to the molecular weight of the gas.
What is the universal gas constant?
A constant that can be used for any gas.
What is an adiabatic process?
A process where there is no heat loss.
What is the ratio of specific heats?
is the ratio of specific heat at constant pressure to the specific heat at constant volume.
What is the speed of sound?
In a fluid the speed of sound is a function of its bulk modulus, or equivalently, of its compressibility.
What is the Mach number?
Its the ratio of the objects speed to the speed of sound in the medium through which the object is traveling.
What does sub sonic travel imply?
A Mach number less than one.
What does super sonic travel imply?
A Mach number greater than one.
What does hyper sonic travel imply?
A Mach number greater than five.
What does transonic travel imply?
Travel in the transition region between subsonic and supersonic. A Mach number between .8 and 1.2.
When does a sonic boom occur?
When an object travels at super sonic speed.
What is reversible flow?
If the gas flow is adiabatic and frictionless.
What is isentropic flow?
Flow with no entropy change.
What are static properties?
Static properties are properties at an instantaneous moment.
What are stagnation properties?
Stagnation properties are the total properties.
What static properties are related in isentropic flow for any two points?
Pressure, temperature, and density.
What variable is used to relate the static properties in isentropic flow for any two points?
The ratio of specific heats.
What stagnation and static properties are related in isentropic flow?
Temperature, density, and pressure.
Do stagnation properties change along the flow path in isentropic flow?
No
Do static properties change along the flow path in isentropic flow?
Yes
What variables are used to relate the static and stagnation properties for isentropic flow?
The Mach number, and ratio of specific heats.
What is critical area?
The area at which the gas velocity is sonic.
What is the flow area?
It is the ratio of the static to critical area.
What is the relationship between the flow area and the Mach number?
When the Mach number is less than one, the flow area must decrease in order for the velocity to increase. However, if the Mach number is greater than one, the flow area must increase in order for the velocity to increase.
What is a shock wave?
When the velocity drops from supersonic to subsonic
What direction does a shock wave form?
It forms normal to the flow direction.
How is the strength of a shockwave measured?
The strength of a shockwave is measured by the change in Mach number across it.
What properties stay constant across a normal shock wave?
Total temperature, enthalpy and momentum
What properties decrease across a normal shock wave?
Total pressure, total density, velocity, and Mach number.
What properties increase across a normal shock wave?
Pressure, density, temperature, entropy, and internal energy.
