A new transient CFD method for determining the dynamic coefficients of liquid annular seals
Currently, the dynamic characteristics of annular seals are numerically investigated mainly by solving the bulk flow equations using perturbation method, or by simulating the perturbed flow field of annular seal using CFD method. The adopted disturbance way is generally the circular whirling motion of rotor around seal centre with constant speed. Relative to the transient CFD simulation, the quasisteady CFD simulation introducing Moving reference frame (MRF) has been widely used by researchers. Both the dynamic mesh problem and the time consuming problem suppress the use of transient CFD simulation in annular seal research. In the paper, a new transient CFD method based on rotor's variable speed whirl is presented to improve the time consuming problem and all the (total 20) dynamic coefficients of concentric liquid seal can be obtained by only two transient CFD simulations, one for the variable speed cylindrical whirl and the other for the variable speed conical whirl. The results are compared with those from the experiment, the quasi steady CFD method and the traditional transient CFD method based on constant speed whirl. The comparisons show that the new transient method can keep the good accuracy of traditional transient method and meantime largely save the computational time.