Study on similarity grade of immovable riverbed hydraulic model

The concept of similarity grade is proposed to quantitatively assess the similitude of hydraulic models.Similitude relationship between model and prototype is based on a series of similarity elements,which is equal to the product of characteristic ratio and corresponding characteristic weight.The sum of all similarity elements is the similarity grade representing the degree of similitude.The similarity between prototype and immovable hydraulic model consists of 10 elements.According to this principle,the effect of geometric distortion on velocity and pressure in distorted model are analyzed.Calculation examples are given.It is concluded that the quantitative evaluation of similarity grade results in enhancing simitilude, and models with larger scale should be advocated.