Rotation Entropy-Based Vortex Identification

The information measure and detection for vortex in flow field is a challenging issue. This paper presents a new information measure for flow field called rotation entropy to highlight vortex regions in flow field. Rotation entropy is the statistical quantity of vectors in sample region around a point, and indicates the rotation information of the region. The properties of rotation entropy are discussed in this paper. Based on these properties, a vortex detection algorithm is proposed. In this algorithm, the linear fit of points in radial direction of the local maximum is applied to determine vortex. The experimental results show that rotation entropy highlights the rotation information of the field, and the algorithm proposed can exactly identify the vortex in flow field.