This article proposes a rotordynamic identification method using the accelerating sweep frequency excitation method. The computational fluid dynamics transient solution combined with the moving grid method is utilized to obtain the transient flow field of the seal excited by the whirling rotor with an accelerating frequency. Rotordynamic coefficients at swept frequencies are obtained by analyzing the transient response force acting on the rotor. Rotordynamic coefficients of three published experimental seals including a labyrinth seal, a fully partitioned pocket damper seal and a honeycomb seal are identified to validate the proposed method. The results show that the predicted rotordynamic coefficients are all well agreement with the trend of experimental data. Compared with the existing numerical models based on transient solutions, the central processing unit consumption of the proposed method is substantially reduced by 98% when achieving the same frequency resolution. In addition, the impact of the exciting acceleration on the identification accuracy is also illustrated.

Nonuniform mesh is beneficial to reduce computational cost and improve the resolution of the interest area. In the paper, a cell-based adaptive mesh refinement (AMR) method was developed for bearing cavitation simulation. The bearing mesh can be optimized by local refinement and coarsening, allowing for a reasonable solution with special purpose. The AMR algorithm was constructed based on a quadtree data structure with a Z-order filling curve managing cells. The hybrids of interpolation schemes on hanging nodes were applied. A cell matching method was used to handle periodic boundary conditions. The difference schemes at the nonuniform mesh for the universal Reynolds equation were derived. Ausas’ cavitation algorithm was integrated into the AMR algorithm. The Richardson extrapolation method was employed as an a posteriori error estimation to guide the areas where they need to be refined. The cases of a journal bearing and a thrust bearing were studied. The results showed that the AMR method provided nearly the same accuracy results compared with the uniform mesh, while the number of mesh was reduced to 50–60% of the number of the uniform mesh. The computational efficiency was effectively improved. The AMR method is suggested to be a potential tool for bearing cavitation simulation.

The cavitation has a potential effect on the performance of surface-textured bearings. The traditional mass-conserving cavitation algorithms based on the Gauss-Seidel iteration method become slow as the grid increases. The computation time is unacceptable once the grid consists of a large array of textures. This study developed an explicit cavitation multigrid algorithm to accelerate the simulation of surface-textured bearings. The algorithm was based on the Ausas cavitation algorithm with the advantage of a matrix-free implementation. Novel numerical technologies were developed to overcome the difficulty of the floating free boundaries caused by the cavitation characteristics. An example of surface-dimpled thrust bearings was studied to analyze the algorithm efficiency. The algorithm is shown to be approximate optimal under reasonable solution parameters. It is an alternative to other cavitation algorithms.

In a turbomachine, the seal is a key flow control device. The highly complex flow behavior in the seal is featured by strong circumferential flow, and such flow causes the uneven circumferential pressure distribution, inducing the destabilizing tangential force that makes the rotor unstable. This raises safety concerns for various turbomachines. Regarding this issue, the fresh collection chamber-connecting pipe design is proposed to restructure the circumferential flow pattern and circumferential pressure distribution. Starting from the labyrinth seal, one collection chamber is designed above each seal cavity. The collection chamber and seal cavity are connected with several connecting pipes. The computational fluid dynamics method is utilized to simulate the new flow phenomenon brought about by the new design and analyze its working mechanisms. Results show that the new design autonomously generates the fluid barrier to weaken the circumferential flow. The pressure transmissions through connecting pipes reduce the unevenness of circumferential pressure distribution. The restructured flow fields have a significant positive effect in reducing the destabilizing tangential force. In comparison with the shallow collection chamber, the deep collection chamber yields the lower tangential force because of the more even circumferential pressure distribution.