# CFD Thermodynamics flow in Angular momentum system

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1. Nov 10, 2015

### Leef

Angular momentum is conserved in a closed system. Is thermal isolation required too?

An example special case in mind is a closed cavity high speed rotation.

It contains high pressure gas and the thermal flow is driving convection currents creating turbulence and or a heat pumping loop. Energy in must = Energy out so even in extreme cases with high thermal flows does Angular momentum Energy become a factor?

2. Nov 10, 2015

### Chandra Prayaga

Not sure what you mean by "angular momentum energy". Do you mean rotational energy?

3. Nov 10, 2015

### Leef

I have 2 main energy flow paths.
A. Strictly a thermal temperature differences to and from container.
B. Energy to maintain a rotation rate of container.

If Angular momentum is conserved in a closed system / the closed container B will always over time settle out and remain 0.

From that then A should settle out to a fixed energy flow rate.

Well I am almost a closed system on the rotation part other than pure Thermal Energy

I think I am ok long as there is no mass exchange in or out of the container Angular momentum will be conserved. So I am looking for a more complete definition or explanation from the thermodynamics and CFD side.

If you start looking at the rotational kintic energy (RKE) it gets complicated fast. Hot gas far out from center in the container will flow inward thus gain RKE, cool gas will flow from center out losing RKE. Then add in the ideal gas pressure / tempura changes it gets very thermodynamics involved. Also there will be turbulence / wall drag on inside wall of container.

It should act like a heat pump and energy is not free so there should be rotational energy input or total thermal flow should be more in than out to support the internal turbulence flow.

4. Nov 10, 2015

### Staff: Mentor

I don't mean to sound rude here, but you've mixed together about a dozen different terms, and only about half appear meaningful in the context you used them (for example, CFD in the title). That's making it hard to understand what you are asking. However:

We can say that in a closed container, energy in and energy out (mechanical or thermal) must be equal when the system is in a steady state (not changing). If there is something rotating inside and the energy flow rates are constant, that means it must rotate at a constant rate.