Theoretical phenomenon is a theory that explains the similarity principle of similar phenomena in nature and engineering. It is a theory that studies the relationship between individuality and * * *, or between particularity and generality, and between internal contradictions and external conditions in natural phenomena. In the structural model test research, only when the model and the prototype remain similar can the corresponding results of the prototype structure be deduced from the model test results.

Features:

Similarity theory is mainly used to guide model experiments and determine the similarity degree and grade between "model" and "prototype". With the continuous progress of computer technology, similarity theory not only continues to exist as the theory of physical model test, but also further expands its application scope and field, becoming one of the guiding theories in computer simulation and other fields. With the expansion of the concept of "similarity", the similarity theory has a tendency to expand from the field of natural science to include the fields of economy, social science, thinking science and cognitive philosophy.

Based on the internal regularity (mathematical equations) and external conditions (definite solution conditions) of the occurrence and development of phenomena, similarity theory takes the inherent homogeneity of these mathematical equations in dimensions and the correctness of these mathematical equations as the premise that they are not affected by the choice of measurement unit system, and obtains its own conclusions through mathematical deduction means such as linear transformation. Similarity theory is characterized by the combination of high abstraction and wide application, and the content of similarity theory is not much, and it is not even regarded as a separate discipline. Similarity theory is the theory of experiment, which is used to guide the fundamental layout of the experiment. It provides guidance for the simulation experiment, such as the reduction or enlargement of scale, the increase or decrease of parameters, the change of medium properties, etc., with the aim of finding out the internal regularity of the studied model at the lowest cost and in the shortest operation period. The most important value of similarity theory in modern science and technology is that it guides model experiments. Although the similarity theory itself is a relatively strict mathematical logic system, once it enters the practical application topic, it can't be very accurate in many cases. Because the problems dealt with by similarity theory are usually extremely complicated.