  In this paper we introduce (I,J) similar method for incompressible two and
three dimensional Euler equations and Navier-Stokes equations, obtain a series
of explicit (I,J) similar solutions to the incompressible two dimensional Euler
equations, they include all of twin wave solutions, some new singularity
solutions, and some global smooth solutions with finite energy. We also
discover that twin wave solution and affine solution to two dimensional
incompressible Euler equations are respectively plane wave and constant vector.
Finally, we supply some explicit piecewise smooth solutions to incompressible
three dimensional Euler and an example to incompressible three dimensional
Navier-Stokes equations which indicates that viscosity limit of a solution to
Navier-Stokes equations does not need to be a solution to Euler equations.
