2. Similarity of thermoacoustic machines

The technique of similarity is often used in aeronautics, naval studies, turbine design, centrifugal or axial compressors and many other machines. It consists in deducing the geometry of a new machine, based on the knowledge of particular dimensionless groupings for the operation of a machine already developed and experimentally tested, and the application of similarity rules. The reference machine can be a scaled-down prototype, for example. Another advantage of similarity is the ability to represent the behavior of a system by means of a reduced number of dimensionless groups, thus limiting the number of variables required in an experimental study. However, the first step is to identify the list of essential variables on which the system's operation depends. For the study of thermoacoustic systems, variables can be classified into the following categories:

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