Design of room air distribution systems
The next section describes the main parameters which should be considered when conducting a physical-model investigation or when interpreting the model data for full-scale design.
6.2.1 Parameters for model investigations
Before conducting an experimental investigation involving a physical model it is essential that the fundamental similarity laws relevant to the case under investigation be established and implemented during the experiments. Any deviation from the basic laws of similarity pertaining to the physics of the problem could diminish the signiﬁcance of the results obtained from the model tests. Szücs  deﬁnes the similarity in the behaviour of systems, i.e. similitude, as ‘two systems (phenomena) are similar if their corresponding characteristics (features, parameters) are connected by bi-unique (oneto-one) mappings (representations)’. This statement links any physical quantity in two systems by a transformation function which is unique to it and therefore a complete similitude may require a number of different transformation functions. For the study of non-isothermal turbulent diffusion of air jets in enclosures three
basic similarity criteria must be adhered to, namely geometric, kinematic and thermal similarities [1-4]. The signiﬁcance of each of these three criteria in modelling room air movement is discussed below.