In this work, the unsteady Reynolds-averaged Navier–Stokes (URANS) and three hybrid Reynolds-averaged Navier–Stokes-large eddy simulation (RANS-LES) models are employed to resolve the vortical flows in a typical single-stage side channel pump, to evaluate the suitability of these advanced turbulence models in predicting the pump hydraulic performance and unstable swirling flows. By the comparison of the overall performance, it can be observed that the results obtained by scale-adapted simulation (SAS) are closer to test data than shear stress transport (SST), detached eddy simulation (DES) and filter-based model (FBM). Simultaneously, the distribution of axial velocity on the plane near the interface is used to describe the position and intensity of internal fluid exchange between impeller and side channel. It is obvious that the intensity of mass flow exchange is strong near the inner and outer edges. Then, the vortex core region illustrates that the vortex is easily produced near the interface due to internal fluid exchange. Finally, the evolutions of circumferential in-plane vortical structures are presented to further account for the process of fluid exchange and the main vortex flows. It reveals that the recirculation flow presents a strong instability during 6–7 blade pitches as the fluid enters into the impeller and the flow is stable in downstream 7–8 blade pitches. Besides, the flow turns to be unsteady near outlet affected by the sudden change of fluid direction. This work could provide some suggestions for the choice of appropriate turbulence model in simulating strong swirling flows.

Objective The purpose of this study was to verify the age-, gender-and Arbeitsgemeinschaft für Osteosynthesefragen (AO) typespecific clinical characters of adult tibial plateau fractures in 83 hospitals in China and to investigate whether altitude has potential relationships with adult tibial plateau fractures. Methods A retrospective investigation was performed on consecutive patients with tibial plateau fractures treated in 83 hospitals in China between January 2010 and December 2011, data including age, gender and imaging were collected retrospectively through the PACS system and case reports checking system, imaging were classified into six types under fully qualified estimation based on AO classification. To further investigate imparities among different altitudes in China, all data were classified into four groups according to the centre altitudes of each city, G1 = plains group (<500 m), G2 = hills group (500-1000 m), G3 = mountain areas group (1000-2000 m), and G4 = plateau group (>2000 m). Comparison of gender distribution, age distribution and AO type were done. Results A total of 6,227 adult tibial plateau fractures were included. Men in the age range of 40-44 years were the most affected patients, and the overall high-risk injury type was 44-B. In four groups, the same peak age showed, namely, 40-44 years in males and 55-59 years in females. Age distribution showed no statistically significant difference in four groups (P > 0.05), while sex distribution and AO type indicated statistically significant differences (P < 0.05). Note an inversion of sex ratio among people over 60 years. Conclusion Our study showed that men in the 40-44 year age range are the most affected patients, and different sex distribution as well as injury type of adult tibial plateau fractures differed with various altitudes in China.

Abstract:Wind forecasting is critical in the wind power industry, yet forecasting errors often exist. In order to effectively correct the forecasting error, this study develops a weather adapted bias correction scheme on the basis of an average bias-correction method, which considers the deviation of estimated biases associated with the difference in weather type within each unit of the statistical sample. This method is tested by an ensemble forecasting system based on the Weather Research and Forecasting (WRF) model. This system provides high resolution wind speed deterministic forecasts using 40 members generated by initial perturbations and multi-physical schemes. The forecasting system outputs 28-52 h predictions with a temporal resolution of 15 min, and is evaluated against collocated anemometer towers observations at six wind fields located on the east coast of China. Results show that the information contained in weather types produces an improvement in the forecast bias correction.

Large eddy simulation is used in this work to simulate the three-dimensional turbulent flow in an open cavity, with special attention paid to the parametrical effect and turbulence analysis. The effect of mesh resolution, the sub-grid model and the advection scheme on the resolved flow structure is discussed in detail. Then, the mechanism of flow-induced pressure fluctuation associated with the primary and secondary vortex in the shear layer is clarified quantitatively and qualitatively. Finally, the turbulent kinetic energy and turbulence production rate, the contribution of three components to total turbulence production rate and the main single contributor are analyzed systematically. The present simulations are performed for two Reynolds numbers and the results show that the flow is more turbulent with the increase in Reynolds number, but the general flow morphology is almost the same. It is expected that the basic founding is useful for understanding such similar flows and will provide some guidelines for controlling the vortex-induced flow instability in engineering applications.