Universal distribution of centers and saddles in two-dimensional turbulence

An electromagnetically forced soap film was used to investigate statistical properties of universal distribution of centers and saddles in two-dimensional turbulance. Jacobian determinant consisting of local vorticity and local strain rate characterized local topology of incompressible two-dimensional flow. The proposed model tested the normalized correlation of shear strain rates in different directions from experimental flow fields. The analysis suggested that the probability distribution functions (PDF) decayed more slowly for positive Jacobian determinant than negative.