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Questions tagged [compressible-flow]

35 questions
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What makes something like water so hard to change its density?

So I'm taking a compressible flow class soon, and I've been thinking beforehand about the topic. A substance like water can easily be pressurized, but its density doesn't change easily, meaning there has to be some microscopic force between…
Jesse Batson
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How do gas flow regulators avoid choking?

According to compressible flow theory, a downstream pressure of 0.528 times upstream pressure is sufficient to choke a flow device. So, how do industrial grade pressure regulators throttle a wide range of pressures (say 150 bar to 20 bar)?
DBTKNL
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Determining mass flow rate and exit velocity of compressible flow

This one's a bit of a doozy, so please feel free to comment on any one single part or parts to this problem. The setup is simple--I have a container (an empty bottle) which I fill with a certain pressure of compressed air through a car tire valve…
Avant Guard
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Methane Gas Density in Adiabatic Compressible Flow

Hi.. The question above is one of the tutorial question from fluid mechanics textbook. In the textbook solution for this question, the density of the methane gas stream at downstream was computed with the ideal gas law equation. What I don't…
Daozui
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Why don't all gas pipe flows end up at sonic speed?

According to the 1D models of compressible fluid flow, the effects of pipe wall friction and the effects of heat addition from the environment both drive a flow toward Mach 1 (i.e. the speed of sound). Whether the flow starts off supersonic (M > 1)…
Sean49
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Shouldn't enthalpies be equal in isentropic process?

I have some questions about the enthalpies between two points during an isentropic process in a nozzle. By doing the energy balance between the two points, one gets: $h_1 + \frac{v_1^2}{2}+gz_1=h_2+\frac{v_2^2}{2}+gz_2$ If one neglects the potential…
Physther
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How do stators in axial compressors work?

How do the stators in axial compressors convert kinetic energy to pressure? Is this equivalent to a water hammer?
Francis L.
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Determining required pressure drop for choked flow conditions to be met

I have pipework system with an inlet pressure, $P_0$, which passes from a pipeline of fixed diameter, $D_0$, through a tee with reducer to a smaller diameter pipe, $D_1$, before returning to another pipeline (same diameter, $D_0$) of lower but…
Avocado
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How to balance flow and pressure in nitrogen purged chambers?

I have an instrument that is technically a humidity controlled chamber. It measures how much moisture is picked up by the sample through a microbalance(Zone 1). Nitrogen gas flows from zone 3 and split into 2 chambers (by a union Tee ) in Zone 2.…
Zaid assaf
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If a fluid is incompressible,is it correct to say that the flow may or may not be incompressible?

From my understanding,when there is no change in volume due to pressure applied on a fluid,the fluid can be called as incompressible.As there can be still be change in volume due to other properties,can I say that flow may be compressible?
Shwetha
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Determination of blower mass flow from limited information

For a variable speed centrifugal blower, can a rough measure of mass flow be obtained from only motor speed and power when the outlet restriction is variable?
DGM
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Why does exit pressure match back pressure in Converging Diverging Nozzles?

I am trying to understand why normal shocks are caused in Converging Diverging Nozzles. My textbook explains that since the exit pressure must match the back pressure, the normal shock is the only mechanism that can make this happen, which I…
john melon
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Using pressure drop to correlate mass flow

I am looking for a way to double check readings I am getting through a mass flow meter that appear to be reading lower than expected. Once flow starts in the system, the pressure regulator at the supply tank drops in pressure readout. This drop…
Justin B.
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Combustion Chamber Back Pressure due to gas injection

I am trying to calculate prior to testing the expected back pressure resulting from injecting gaseous oxygen through an injector orifice (choked) into a rocket combustion chamber before ignition. I have tried using the Borda-Carnot equation with the…
Justin B.
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Isentropic flow equation derivation

I am trying to derive the isentropic flow equations for a compressible gas by myself and at the end, I have different formulation than the one in the literature. Can you please tell me what am I doing wrong? So we have a nozzle: If we do an energy…
Physther
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