**2. Finite Element Analysis of Diaphragm Deformation**

The flow path surface structure of weir type diaphragm valve is determined not only by the shape of the bottom ridge and the tube wall itself, but also by the deformation of the diaphragm bottom surface and the angle of the installation joint at different openings. A number of shape elements determine the upper and lower wall boundary of the two-dimensional flow field of weir type diaphragm valve.

However, the rubber diaphragm is hyper elastic and irregular in shape. It is difficult to calculate the deformation by theoretical calculation [31,32]. At present, there are few experimental or simulation results for the diaphragm deformation when the diaphragm valve works. Therefore, in order to obtain the inner surface shape of the diaphragm at different openings and determine the changing two-dimensional flow field boundary, firstly, finite element method analysis on the diaphragm of diaphragm valve is carried out.
