Natural Frequency – Whole is not equal to its Parts

The concept that a system behaves differently than its parts is a concept which many often find it difficult to understand. By our education and training we are naturally prone to look at parts rather than the system . The idea is that the property of a system is distinctly different to the individual properties of its parts.

Let us illustrate this concept that a system would always behave differently than its parts through a simple example. We would take a physical parameter and then see how this physical parameter, which is a distinct property of a part, would change as soon as two parts are made to work together. For our purpose we would take ‘natural frequency’ as a physical parameter and see how it changes. And we would take the turbine-generator combination — a prime example  to illustrate this phenomenon of system behaviour.

The first natural frequency of the turbine, which is a property of the turbine, when taken alone is 2433 cycles per minute (cpm). Similarly the first natural frequency of the generator, when taken alone is 2124 cycles per minute (cpm).

What happens when we connect the turbine and the generator together through a coupling and make them work together? The natural frequencies of both the turbine and that of the generator would change altogether! Remember that natural frequency is a distinct property of a part.

The combined natural frequency changes in the following manner:

The first natural frequency of the turbine becomes 2028 cpm (drops by 17%) while that of the generator becomes 1806 cpm (drops by 15%). So the first natural frequency of the parts have changed as soon as the parts were put together.

Hence, it is always true that the WHOLE is never equal to its PARTS. Therefore, while designing, maintaining or operating or examining a problem, fault or a failure we would always gain a better understanding by observing a system as a whole and not its parts.

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3 thoughts on “Natural Frequency – Whole is not equal to its Parts

  1. It is true, even if in some disciplines this concept is not considered. In medicine the part is ever at the center of everything. So if you can understand symptoms leading to a part you are able to do something, otherwise you have to guess …

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  2. Another example might be a supercell thunderstorm, which is a moist push of air rising and rotating through cold air, resulting in the release of energy which accelerates the process, finally resulting in a downdraft and other features like microbursts, hail and tornadoes. The components are simply hot, humid air under colder air along with some vorticity in the atmosphere along with shearing winds.

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