CFD Thermodynamics flow in Angular momentum system

Click For Summary

Discussion Overview

The discussion revolves around the relationship between angular momentum conservation and thermal dynamics in a closed, rotating system, particularly focusing on the implications of thermal isolation and energy flow in such systems. The context includes concepts from thermodynamics and computational fluid dynamics (CFD), with an emphasis on high-speed rotation and turbulence effects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether thermal isolation is necessary for angular momentum conservation in a closed system, using a high-speed rotating cavity with high-pressure gas as an example.
  • Another participant seeks clarification on the term "angular momentum energy," suggesting it may refer to rotational energy.
  • A participant outlines two main energy flow paths: thermal energy transfer due to temperature differences and energy required to maintain the rotation rate of the container.
  • It is proposed that if angular momentum is conserved, the energy flow related to thermal dynamics should stabilize over time, assuming no mass exchange occurs.
  • Concerns are raised about the complexity introduced by rotational kinetic energy, where hot gas flows inward gaining rotational energy while cooler gas flows outward losing it, complicating the thermal dynamics.
  • Another participant critiques the clarity of the initial post, noting the mixing of terms and suggesting that energy in and out must balance in a steady state, especially in a rotating system.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of angular momentum and energy flow in the context of thermodynamics, indicating that the discussion remains unresolved with multiple competing interpretations.

Contextual Notes

There are limitations in the definitions used, particularly regarding the terms related to energy types and flow, as well as the assumptions about system behavior under varying conditions of rotation and thermal dynamics.

Leef
Messages
12
Reaction score
1
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?
 
Science news on Phys.org
Not sure what you mean by "angular momentum energy". Do you mean rotational energy?
 
Chandra Prayaga said:
Not sure what you mean by "angular momentum energy". Do you mean rotational energy?

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.
 
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.
 

Similar threads

  • · Replies 135 ·
5
Replies
135
Views
9K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 15 ·
Replies
15
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
17
Views
2K
Replies
7
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 5 ·
Replies
5
Views
4K