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 Lam February 24, 2005 10:30

Concept Behind Moving Reference Frame

I would like to understand the concept behind the moving reference frame especially from the methematical view. Do anyone know where can I get any journal papers, books or any else resources?

Thanks in advances. Lam

 Bak_Flow February 27, 2005 13:31

Re: Concept Behind Moving Reference Frame

Hello Lam,

the concept is that our choice of coordinates from which to analyze a problem is in fact that "our choice". We can formulate the equations of motion in any frame that we wish.

Of course, most cases and courses teach the formulation of the equations of motion and boundary conditions, etc in an Eulerian frame fixed in space. There are 2 categories of moving frames of reference:

1. Inertial frames whereby the problem is solved in a moving but not accelerating frame.

2. Non-Inertial frames whereby the problem is solved in an accelerating frame. In this frame we must add "pseudo forces" to the equations of motion.

An aricraft flying at altidude and not accelerating is an example of a problem that can be solved (in a frame moving with the aircraft) by 1.

A rotor which rotates at a constant speed is and example of a problem that can be solved (in a frame attached to the rotor) by 2.

Why do we do it.....by solving in the "most appropriate frame" it greatly simplifies the problem. In both cases above the problem changes from being a fully unsteady problem in the fixed frame to steady in the moving reference frame.

As for references well many fluids and continuum mechanics texts cover some of this in more or less detail.

I have noted, although not gone through all the details, that

Fluid Dynamics: Theoretical and Computational Approaches Z. U. A. Warsi

has quite an extensive coverage on coordinate frames.

There also are lots of papers on specific frames for example for rotation problems look for papers in the 1980's by Bill Dawes.

Best of luck,

Bak_Flow

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