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In this study, the three-dimensional incompressible flow in a large-scale vaned-voluted centrifugal pump was numerically studied based on the Reynolds-averaged Navier–Stokes (RANS) method. As the flow rate increases, the vortices suddenly appear and disappear. These alternating vortices cause the instability region on the Q-H curve. Therefore, the local entropy production rate (LEPR) is analyzed for a better understanding. The LEPR method will provide a visualization of the energy change in unit and make it easier to understand the reasons of head-hump. Large-scale vaned-voluted centrifugal pumps are often used in large-scale water diversion projects. Long-time operation and frequent changes of conditions require the stability of pump performance, and the head-hump is an important factor that affects the stability of centrifugal pumps. The hump characteristics must be studied and the hump region should be avoided. Under small flow rate condition, six typical high LEPR situations in stay vanes are summarized. It is found that the vortex itself will not produce a large energy loss, the vortex causing high LEPR interacts with surrounding flow or wall. The flow interaction dominates LEPR in impeller and stay vanes. Zonal proportion of LEPR in impeller accounts for a higher proportion than stay vane. This study provides an effective way in understanding the mechanism of flow energy loss in the large-scale vaned-voluted centrifugal pump and can be referred to other similar turbomachinery cases.

Centrifugal impeller is usually designed for water pumping. Fluid get energy from impeller but also lose energy when passing through it. To improve the efficiency and have a better operation stability, it is necessary to understand the flow energy dissipation in centrifugal impeller in pump mode. In this case, a thermodynamic analysis is conducted on a model centrifugal pump unit based on computational fluid dynamics (CFD) simulation. Typical performance curve is found with a positive-slope efficiency curve and a negative-slope head curve. With the decreasing of flow rate, both the impeller head and the flow energy dissipation (FED) will rise up. The FED is found related to the flow regime. The complex undesirable flow pattern induces high FED under off-design conditions especially at very small partial-load. Based on the visualization, FED is found with two main sources including the wall friction and the flow interaction. At over-load and design-load, the wall friction induced FED is dominant. With the decreasing of flow rate, flow interaction induced FED becomes dominant. The typical strong FED sites are found related to the striking, separation, merging and interaction of both smooth flow and vortical flow. The FED analysis will correlate the pump performance estimation and guide the design.

Mesoscale convective systems (MCSs) play an important role in modulating the global water cycle and energy balance and frequently generate high-impact weather events. The majority of existing literature studying MCS activity over East Asia is based on specific case studies and more climatological investigations revealing the precipitation characteristics of MCSs over eastern China are keenly needed. In this study, we use an iterative rain cell tracking method to identify and track MCS precipitation during 2008–16 to investigate regional differences and seasonal variations of MCS precipitation characteristics. Our results show that the middle-to-lower reaches of the Yangtze River basin (YRB-ML) receive the largest amount and exhibit the most pronounced seasonal cycle of MCS precipitation in eastern China. MCS precipitation over YRB-ML can exceed 2.6 mm day−1 in June, contributing over 30.0% of April–July total rainfall. Particularly long-lived MCSs occur over the eastern periphery of the Tibetan Plateau (ETP), with 25% of MCSs over the ETP persisting for more than 18 h in spring. In addition, spring MCSs feature larger rainfall areas, longer durations, and faster propagation speeds. Summer MCSs have a higher precipitation intensity and a more pronounced diurnal cycle except for southeastern China, where MCSs have similar precipitation intensity in spring and summer. There is less MCS precipitation in autumn, but an MCS precipitation center over the ETP still persists. MCSs reach peak hourly rainfall intensities during the time of maximum growth (a few hours after genesis), reach their maximum size around 5 h after genesis, and start decaying thereafter.

The Tibetan Plateau (TP) is known as Asian Water Tower and its atmospheric water cycle has been a lasting challenge to climate modeling community. Here, we compare two sets of the Met Office Unified Model simulations—one is a convection-parameterized version (large-scale model; LSM) and the other is a convection-permitting model (CPM) simulation. The added value of the CPM in terms of atmospheric water cycle process is analyzed, including external moisture transport, fraction of atmospheric water vapor converting to precipitation and the precipitation recycle ratio. Results show that the simulated TP precipitation and evaporation for the summer of 2009 is significantly improved in the CPM. First, the overestimation of atmospheric water cycle by LSM is improved in CPM due to a reasonable representation of the fraction of atmospheric water vapor converting to precipitation. The overestimation of precipitation recycle ratio also indicates the LSM generates excessive convection compared to the CPM and therefore has a larger wet bias over the TP. Second, a better simulation of local precipitation has feedback on the circulation. Compared with the LSM, the less moisture convergence in the CPM is dominated by the stronger outflow through the eastern edge of the TP rather than the weaker inflow, implying the upscale effects of the resolved moist convection on the moisture transport over the TP. Our results imply that the CPM is a useful tool in the reproduction of moisture transport and atmospheric water cycle process over the Asian Water Tower and other regions of the world with complex topography.

Observations are required to understand monsoon changes over time. Reanalyses are useful supplements to observations; however, their ability to reveal long-term monsoon changes remains unknown. Here, we evaluate against observations the performance of two reanalysis datasets covering the whole twentieth century, the ECMWF reanalysis of the twentieth century (ERA20C) and the Twentieth Century Reanalysis Project (20CR), in terms of reproducing the climatological averages, the centennial co-variation, and long-term trends of Northern Hemisphere land monsoon rainfall (NHLMR). Their performance is compared with three other widely used reanalyses, the NCEP–NCAR reanalysis (NCEP1), the ECMWF 40-year reanalysis (ERA40), and the Japanese 55-year Reanalysis Project (JRA55), for the period after 1955. Results show that the five reanalysis datasets reasonably reproduce the climatological NHLMR and NHLM domains. The leading co-variation mode of NHLMR, with an overall increasing tendency before 1955 and a decreasing tendency afterwards, is captured by the corresponding principal components of the two long-term datasets, with some spatial biases. For the long-term precipitation trends, both the ERA20C and 20CR reproduce the increasing trend during 1901–1955, except for parts of the North African (NAF) monsoon region. However, neither dataset captures the decreasing trend of NHLMR after 1955 because of limitations in the NAF and North American (NAM) monsoon region. The NCEP1, ERA40, and JRA55 datasets also have shortcomings in the NAM region. An overall decreasing NHLMR is only shown in the NCEP1 dataset. A moisture budget analysis reveals that the long-term trends of NHLMR are dominated by the dynamic component of moisture convergence, suggesting a prominent role for atmospheric circulation changes. The influence of residual terms related to observations assimilated in the reanalyses is also discussed.

During the period from June 30th to July 6th, 2016, a heavy rainfall event affected the middle and lower reaches of the Yangtze River valley in eastern China. The event was characterized by high‐intensity, long‐duration (lasted more than 6 days) precipitation and huge amounts (over 600.0 mm) of rainfall. The rainfall moved eastward from the Sichuan basin to the middle Yangtze River valley during the first 2 days, then Mei‐yu front formed and circulations became more “quasi‐stationary”. During the second‐phase, successive heavy rainfall systems occurred repeatedly over the same areas along the front, leading to widespread and catastrophic flooding. In this study, limited‐area convection‐permitting models (CPMs) covering all of eastern China, and global‐model simulations from the Met Office Unified Model are compared to investigate the added values of CPMs on the veracity of short‐range predictions of the heavy rainfall event. The results show that all the models can successfully simulate the accumulated amount and the evolution of this heavy rainfall event. However, the global model produces too much light rainfall (10.0 mm/day), fails to simulate the small‐scale features of both atmospheric circulations and precipitation, and tends to generate steady heavy rainfall over mountainous region. Afternoon precipitation is also excessively suppressed in global model. By comparison, the CPMs add some value in reproducing the spatial distribution of precipitation, the smaller‐scale disturbances within the rain‐bands, the diurnal cycle of precipitation and also reduce the spurious topographical rainfall, although there is a tendency for heavy rainfall to be too intense in CPMs.

Vortex rope is a common phenomenon in the draft tube of hydraulic turbines. It may cause strong pressure pulsation, noise, and strong vibration of the unit especially when it is helical. Therefore, the study of vortex rope is of great significance. In order to study the helical vortex rope, the embedded large eddy simulation (ELES) method in the hybrid methods is used based on the vortex rope generator case. The Liutex method can show the three-dimensional shape of the vortex rope well. In order to quantitatively describe the helical vortex rope, the three-dimensional structure is divided into multiple two-dimensional sections, and then the shape of vortex rope on each section is processed to extract the perimeter and area of the vortex. Combined with the change trend of vortex number and section area, the helical vortex rope is divided into four zones. Then, the fractal dimension on each zone and section can be obtained, and it can be used to quantitatively analyze the change trend of the vortex rope in time and space. The fractal analysis method can be applied to the analysis of the vortex rope in the draft tube to help judge the flow pattern shape and the stability of the unit operating conditions.

Blade leading-edge pressure drop is an important parameter that strongly influences the safe and stable operation of centrifugal pump. It is sensitive to blade leading-edge geometry. To understand the inlet flow state of centrifugal pump, it is necessary to evaluate the location and the minimum value of blade leading-edge pressure drop. However, the operation condition is complex. A large amount of experiments and numerical simulations should be conducted for a fully understanding of the local pressure field. With the development of artificial intelligence, machine learning can be used for accelerating the evaluations with potential laws of fluid mechanism. Therefore, neural network is used in this case to fit the solution space of condition, leading-edge geometry and local pressure drop. The influence of different factors can be well analyzed. The conditions which is not directly tested will be predicted by well-trained neural network. With the increasing of the leading-edge elliptic ratio of the blade inlet, the minimum pressure position of the blade moves from the impeller hub to the impeller shroud. This study provides a preliminary study and a good reference of the evaluation of blade inlet leading edge flow state in the future researches.

A limited area convection permitting model (CPM) based on the Met Office Unified Model, with a 0.04° (4.4 km) horizontal grid spacing, is used to simulate an entire warm-season of the East Asian monsoon (from April to September 2009). The simulations are compared to rain gauge observations, reanalysis and to a lower resolution regional model with a 0.12° (13.2 km) grid spacing that has a parametrization of subgrid-scale convective clouds and precipitation. The 13.2 km simulation underestimates precipitation intensity, produces rainfall too frequently, and shows evident biases in reproducing the diurnal cycle of precipitation and low-level wind fields. In comparison, the CPM shows significant improvements in the spatial distribution of precipitation intensity, although it overestimates the intensity magnitude and has a wet bias over central eastern China. The diurnal cycle of precipitation over Mei-yu region, southern China and the eastern periphery of the Tibetan Plateau, as well as the diurnal cycle of low-level winds over both the Mei-yu region and southern China are better simulated by the CPM. Over the Mei-yu region, in both simulations and observations, the local atmospheric instability in the afternoon is favorable for upward motion and rainfall. The CPM receives more sensible heat flux from the surface, has a stronger upward motion, and overestimates water vapor convergence based on moisture budget diagnosis. All these processes help explain the excessive late afternoon rainfall over the Mei-yu region in the CPM simulation.

In this study, atmospheric water vapor transport was analyzed to study the changes in spring persistent rainfall (SPR) over southeastern China from 1980 to 2012. The performances of five sets of reanalysis data in reproducing the climatology, the long-term trend and interannual variability of the SPR were synthetically evaluated. To understand the mechanisms dominating SPR variation, the major components of moisture budget, including vertical moisture advection, horizontal moisture advection and evaporation, were examined based on the five reanalysis datasets. The results show that all five reanalysis datasets reproduce the climatology of the SPR reasonably well. Strong westerly wind flow over the southern Tibetan Plateau and southwest wind flow over the western North Pacific are the two main channels remotely supplying water vapor for the SPR. Locally, moisture budget diagnosis shows that the SPR is primarily contributed by the evaporation and vertical moisture advection terms. The SPR shows a decreasing tendency [−0.38 mm day−1 (10 year)−1] during 1980–2012 along with strong interannual variation, which is reasonably captured by all five reanalysis datasets. Vertical moisture advection dominates the SPR variation, and the decreasing trend of the SPR is mainly due to the weakening of ascending motion during this period. In an El Nino decaying spring, the anomalous lower-tropospheric anticyclone over the western North Pacific intensifies vertical upward motion and leads to more precipitation. Both the Japanese 55-year reanalysis (JRA55) and the European Centre for Medium-Range Weather Forecast interim reanalysis (ERAIM) show higher skill in reproducing the climatology and changes of the SPR.

Understanding the energy development ideas of the Yellow River Basin has a very important impact on the high-quality development of the Yellow River Basin. Aiming at the restriction and promotion of energy consumption in the Yellow River Basin to its high-quality development, this article takes the nine provinces of the Yellow River as the research object, builds an evaluation model based on the data of the river basin from 2004 to 2017, and uses the entropy method and elastic coefficient method to study the coupling characteristics of watershed energy consumption for its high-quality development in time and space. The results show that the high-quality development level of the river basin is generally increasing, the consumption level is generally decreasing, and the coupling of energy consumption and high-quality development is optimized year by year. Finally, according to the coupling of energy consumption level and high-quality development level, a development strategy suitable for improvement is proposed.

The expression of Aurora B in normal endometria and endometrial carcinomas and its relation with clinicopathologic parameters of endometrial carcinomas were investigated. Streptavidin-biotin peroxidase (SP) immunohistochemical technique was used to detect the expression of Aurora B in 10 cases of normal proliferative phase endometria, 10 cases of normal secretory phase endometria and 72 cases of endometrial carcinomas respectively. According to the 1988 International Federation of Gynecology and Obstetrics (FIGO) grade, there were 37 patients in grade 1, 23 in grade 2 and 12 in grade 3 respectively. According to the FIGO stage, there were 59 patients in stage I-II and 13 patients in stage III-IV. Aurora B was expressed in both normal proliferative phase endometria, secretory phase endometria and endometrial carcinomas, but its positive labeling index (PLI) in proliferative phase endometria was significantly higher than that in secretory phase endometria (P0.01) and endometrial carcinomas (P0.01). The PLI of Aurora B was lower in tumors with well differentiation (G(1)), low surgical staging (I-II), andor=1/2 myometrial invasion than that in tumors with moderate and low differentiation (G(2)-G(3)), higher surgical staging (III-IV), and1/2 myometrial invasion (all P0.01). Aurora B exerts its functions in the replication of normal endometrial glandular cells; Expression of Aurora B is significantly correlated with biologic behavior of endometrial carcinoma, indicating that Aurora B may be a promising prognostic factor in endometrial carcinoma.