| Abstract: | Relative dispersion ratio(RDR) can be used to quantify the deviation behavior of a water parcel's trajectory caused by a disturbance in a hydrodynamic system. It can be calculated by using a standard method for determining relative dispersion(RD),which accounts for the growth of the deviation of a cluster of particles from a specific initial time. However, the standard method for computing RD is time consuming. It involves numerous computations on tracing many water parcels. In this study, a new method based on the adjoint method is proposed to acquire a series of RDR fields in one round of tracing. Through this method,the continuous variation in the RDR corresponding to a time series of the disturbance time t can be obtained. The consistency and efficiency of the new method are compared with those of the standard method by applying it to a double-gyre flow and an unsteady Arnold-Beltrami-Childress flow field. Results show that the two methods have good consistency in a finite time span. The new method has a notable speedup for evaluating the RDR at multiple t. |
