What is Rayleigh line & fanno line?

Asked By: Alireza Uva | Last Updated: 24th January, 2020
Category: science physics
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Difference between Fanno Line Flows and Rayleigh Line Flows:- Fanno Line: The line representing the locus of points with the same mass velocity and stagnation enthalpy is called a Fanno line. It is a one-dimensional model for adiabatic flow in a constant area duct with friction.

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Considering this, what do you understand by choking in Rayleigh flow?

Rayleigh flow refers to frictionless, non-Adiabatic flow through a constant area duct where the effect of heat addition or rejection is considered. Heat addition will cause both supersonic and subsonic Mach numbers to approach Mach 1, resulting in choked flow.

Furthermore, what is meant by isentropic flow? In fluid dynamics, an isentropic flow is a fluid flow that is both adiabatic and reversible. That is, no heat is added to the flow, and no energy transformations occur due to friction or dissipative effects.

Just so, what is choking in Fanno flow?

Fanno flow is the adiabatic flow through a constant area duct where the effect of friction is considered. For a flow with an upstream Mach number greater than 1.0 in a sufficiently long enough duct, deceleration occurs and the flow can become choked.

What is sonic flow?

Answered Mar 17, 2018. Subsonic flow is a flow which has a velocity lower than the velocity of sound. In other words, the fluids which has a Mach number less than 1. Sonic flow is the flow which has the same velocity as the sound. In other words, the fluids which has a Mach number equal to 1.

34 Related Question Answers Found

What is Rayleigh line?

In thermodynamic coordinates, the Rayleigh flow process can be described by a curve known as Rayleigh line and is defined as the locus of quasi- static thermodynamic state points traced during the flow. The Rayleigh line satisfies the equation of state along with simple forms of continuity and momentum equation.

What is choking in nozzle?

Choked flow. Choked flow is a fluid dynamic condition associated with the venturi effect. When a flowing fluid at a given pressure and temperature passes through a constriction (such as the throat of a convergent-divergent nozzle or a valve in a pipe) into a lower pressure environment the fluid velocity increases.

How do you determine if a nozzle is choked?

If P06/Pc > P06/Pa, the nozzle is unchoked, whereas if P06/Pc < P06/Pa, the nozzle is choked. This can be simplified by saying if the critical pressure is greater than atmospheric pressure, the nozzle is choked.

What is critical flow rate?

In the context of biofilms, critical flow rate is the minimum flow rate that keeps biofilm deposits from forming on the surface of the pipe. In the context of corrosion or errosion, critical flow rate is the maximum flow rate that avoids damage to the pipe from corrosion or erosion.

What is sonic velocity?


Simply stated, sonic velocity is the velocity of sound in that fluid (a gas/vapor). It is a maximum that can be achieved by the fluid. As you know, flow is induced due to a pressure difference between the upstream condition and the downstream condition.

What is critical pressure drop?

The critical pressure drop is the point at which any further pressure drop will not result in an increase in steam velocity. The approximate value at which the critical velocity occurs is 45 percent of the absolute inlet pressure.

What is supersonic flow?

supersonic flow. [¦sü·p?r¦sän·ik ′flō] (fluid mechanics) Flow of a fluid over a body at speeds greater than the speed of sound in the fluid, and in which the shock waves start at the surface of the body. Also known as supercritical flow.

Is choked flow bad?

Choked flow is bad because you can't get any more flow by increasing the pressure drop… with a fixed orifice and constant inlet conditions. Remember, choked flow is based on no changes in inlet conditions or Cv, so if the Cv can change, then the issues with choked flow also change.

How is Mach calculated?

Calculating the Speed of Sound:
Once the speed of sound is known, the Mach number can be easily computed by dividing the airspeed of the vehicle by the speed of sound. Or conversely, the airspeed of the vehicle can be found by multiplying the speed of sound by the Mach number.

What is critical pressure ratio in nozzle?


The maximum gas flow through a nozzle is determined by critical pressure. critical pressure ratio is the pressure ratio where the flow is accelerated to a velocity equal to the local velocity of sound in the fluid.

What is back pressure in nozzle?

Back pressure is a single value of pressure typically represent that at the exit of a flow device in your case the duct. There are many ways to make the gas in the duct to flow, and one of them is to lower the pressure at the exit (back pressure) . The suction pressure at each nozzle is 1kPa.

What is critical flow condition?

critical flow Critical flow occurs when the flow velocity in a channel equals the wave velocity generated by a disturbance or obstruction. In this condition the Froude number (Fr) = 1.

How do you define enthalpy?

Enthalpy is a thermodynamic property of a system. It is the sum of the internal energy added to the product of the pressure and volume of the system. It reflects the capacity to do non-mechanical work and the capacity to release heat. Enthalpy is denoted as H; specific enthalpy denoted as h.

How do I calculate entropy?

Key Takeaways: Calculating Entropy
  1. Entropy is a measure of probability and the molecular disorder of a macroscopic system.
  2. If each configuration is equally probable, then the entropy is the natural logarithm of the number of configurations, multiplied by Boltzmann's constant: S = kB ln W.

What does Polytropic mean?


The term "polytropic" was originally coined to describe any reversible process on any open or closed system of gas or vapor which involves both heat and work transfer, such that a specified combination of properties were maintained constant throughout the process.

What is adiabatic flow?

Adiabatic conditions refer to conditions under which overall heat transfer across the boundary between the thermodynamic system and the surroundings is absent. The flow of a viscous liquid or gas through a heat-insulated channel is often referred to as adiabatic.

Are nozzles Isenthalpic?

When the change in flow variables is small and gradual, isentropic flows occur. The generation of sound waves is an isentropic process. A supersonic flow that is turned while there is an increase in flow area is also isentropic. Since there is an increase in area, therefore we call this an isentropic expansion.