An Efficient Preprocessing and Composition Based Finite-Time Lyapunov Exponent Visualization Algorithm for Unsteady Flow Field

Based on piecewise linear hypothesis that both the velocity and flow map gradient are constant in grid cell and adjacent time intervals, we design a time-slicing flow map preprocessing and composition based Finite-Time Lyapunov Exponent (FTLE) visualization algorithm for unsteady flow field. This algorithm is capable of reducing the computation overhead from duplicated flow map calculation and multiple spatiotemporal variable interpolation. The FTLE computation error and speedup ratios with different field size are obtained from the experiments performed on 2- and 3-dimensional unsteady flow fields. The results show that this algorithm could dramatically improve visualization efficiency and reduce execution time compared with FTLE visualization by 4th-order Runge-Kutta (RK4) based flow map and other related algorithms.