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This paper aims to study the transient flow characteristics in a mixed-flow pump during the start-up period.

In this study, numerical calculation of the internal flow field in a mixed-flow pump using the sliding mesh method was carried out. The regulation of the pressure, streamline and the relative speed during the start-up period was analyzed.

The trend of the simulated head is consistent with the experimental results, and the calculated head is around 0.3 m higher than the experimental head when the rotation speed reached the stable stage, indicating that the numerical method for the start-up process simulation of the mixed-flow pump has a high accuracy. At the beginning, the velocity inside the impeller changes little along the radius direction and the flow rate increases slowly during the start-up process. As the rotation speed reached the stable stage, the flow inside the impeller became steady, the vortex reduced and transient effects disappeared gradually.

The study results have significant value for revealing the internal unsteady flow characteristics of the mixed-flow pump and providing the reference for the design optimization of the mixed-flow pump.

The purpose of this paper is to experimentally and numerically study the transient hydraulic impact and overall performance during startup accelerating process of mixed-flow pump.

In this study, the impeller rotor vibration characteristics during the starting period under the action of fluid–structure interaction was investigated, which is based on the bidirectional synchronization cooperative solving method for the flow field and impeller structural response of the mixed-flow pump. Experimental transient external characteristic and the transient dimensionless head results were compared with the numerical calculation results, to validate the accuracy of numerical calculation method. Besides, the deformation and dynamic stress distribution of the blade under the stable rotating speed and accelerating condition were studied based on the bidirectional fluid–structure interaction.

The results show that the combined action of complex hydrodynamic environment and impeller centrifugal force in the startup accelerating process makes the deformation and dynamic stress of blade have the rising trend of reciprocating oscillation. At the end of acceleration, the stress and strain appear as transient peak values and the transient effect is nonignorable. The starting acceleration has a great impact on the deformation and dynamic stress of blade, and the maximum deformation near the rim of impeller outlet edge increases 5 per cent above the stable condition. The maximum stress value increases by about 68.7 per cent more than the steady-state condition at the impeller outlet edge near the hub. The quick change of rotating speed makes the vibration problem around the blade tip area more serious, and then it takes the excessive stress concentration and destruction at the blade root.

This study provides basis and reference for the safety operation of pumps during starting period

The purpose of this study is to validate the different turbulence models using in the numerical simulation of centrifugal pump diffuser. Computational fluid dynamics (CFD) has become the main method to study the pump inner flow patterns. It is important to understand the differences and features of the different turbulence models used in turbomachinery.

The velocity flow fields in a compact return diffuser under different flow conditions are studied and compared between CFD and particle image velocimetry (PIV) measurements. Three turbulence models are used to solve the steady flow field using high-quality fine structured grids, including shear stress transport (SST) k-w model, detached-eddy simulation (DES) model and SST k-w model with low-Re corrections.

SST k-w model with low-Re correction gives better results compared to DES and SST k-w model, and gives a good predication about the vortex core position under strong part-loading conditions.

A special test rig is designed to carry out the 2D PIV measurements under high rotating speed of 2850 r/min, and the PIV results are used to validate the CFD results.

The purpose of this paper is to predict the unstable cavitation shedding flow around a 2D Clark-y hydrofoil.

The paper studies Partially Averaged Navier-Stokes (PANS) model which was employed in the two-phase flow with a homogeneous cavitation model.

Maximum density ratio affects the mass transfer rate between the liquid and the vapor significantly. The cavitating flow predicted by PANS model can resolve more turbulent scales by decreasing the parameter fk.

The accuracy of numerical prediction is improved by increasing the maximum density ratio and decreasing fk.

Unlike previous research that primarily utilized structural equation modelling (SEM) to evaluate safety hazards in subway projects, this research aims to utilize a hybrid approach to investigate and scrutinize the key indicators of safety hazards leading to accidents, thereby hindering the progress of subway projects in China, taking into cognizance the multiple stakeholder’s perspective.

By administering a survey questionnaire to 373 highly involved stakeholders in subway projects spanning Changsha, Beijing and Qingdao, China, our approach incorporated a four-staged composite amalgamation of exploratory factor analysis (EFA), confirmatory factor analysis (CFA), covariance-based structural equation modelling (CB-SEM) and artificial neural network (ANN) to develop an optimized model that determines the causal relationships and interactions among safety hazards in subway construction projects.

The optimized model delineated the influence of individual safety hazards on subway projects. The feasibility and applicability of the model developed was demonstrated on an actual subway project under construction in Changsha city. The outcomes revealed that the progress of subway projects is significantly influenced by risks associated with project management, environmental factors, subterranean conditions and technical hazards. In contrast, risks related to construction and human factors did not exhibit a significant impact on subway construction progress.

While our study provides valuable insights, it is important to acknowledge the limitation of relying on theoretical approaches without empirical validation from experiments or the field. In future research, we plan to address this limitation by assessing the SEM using empirical data. This will involve a comprehensive comparison of outcomes derived from CB-SEM with those obtained through SEM-ANN methods. Such an empirical validation process is crucial for enhancing the overall efficiency and robustness of the proposed methodologies.

The established hybrid model revealed complex non-linear connections among indicators in the intricate project, enabling the recognition of primary hazards and offering direction to improve management of safety in the construction of subways.

Knowledge sharing is an important way to improve the knowledge system of industrial construction, and the supervision mechanism is an important way to improve the efficiency of knowledge sharing. However, some research works and practices indicate that the effects of applying the supervision mechanism are not obvious. Therefore, the purpose of this paper is to propose an incentive method of knowledge sharing based on the supervision mechanism for promoting knowledge sharing among member enterprises in the industrial construction supply chain.

A basic incentive model and an optimization model of knowledge sharing in the industrial construction supply chain based on the supervision mechanism were developed via the principal–agent theory. Weighted coefficients of explicit and implicit knowledge sharing were introduced into the basic model, while the supervision reward was added into the basic model of the optimization model. The effect of these two models was compared and analyzed via numerical simulation.

The optimal incentive coefficient and effort level of knowledge sharing can be obtained by solving the two aforementioned models. The results of the comparison between the two models indicate that the introduction of a supervisory reward improved the effort level and expected earnings produced by knowledge sharing, but reduced the confirmed equal earnings of member enterprises in the industrial construction supply chain.

Mutual transformation between tacit and explicit knowledge was not considered, and supervisory costs were also not considered, in the estimation of the output of knowledge sharing.

The new models proposed by this study provide theoretical guidance for the design of knowledge sharing incentive measures in the industrial construction supply chain based on the supervision mechanism. The findings suggest that member enterprises should pay attention to the costs of knowledge sharing, in order to obtain more benefits.

This study introduced the weight coefficients of explicit and implicit knowledge sharing into a previous incentive model, proposed an incentive optimization model of knowledge sharing in the industrial construction supply chain based on a supervisory mechanism, and revealed the change rules of related variables that affect the model with the change in weight coefficients. The findings verify the effectiveness of introducing supervisory reward measures and extend the range of theoretical application.

Suggests that misunderstandings frequently occur when trying to understand Chinese language and culture, and so gives the implied meaning of various Chinese expressions and sayings such as greetings, thanks, respect, age, congratulations and taboo subjects.

To solve the obstacle detection problem in robot autonomous obstacle negotiation, this paper aims to propose an obstacle detection system based on elevation maps for three types of obstacles: positive obstacles, negative obstacles and trench obstacles.

The system framework includes mapping, ground segmentation, obstacle clustering and obstacle recognition. The positive obstacle detection is realized by calculating its minimum rectangle bounding boxes, which includes convex hull calculation, minimum area rectangle calculation and bounding box generation. The detection of negative obstacles and trench obstacles is implemented on the basis of information absence in the map, including obstacles discovery method and type confirmation method.

The obstacle detection system has been thoroughly tested in various environments. In the outdoor experiment, with an average speed of 22.2 ms, the system successfully detected obstacles with a 95% success rate, indicating the effectiveness of the detection algorithm. Moreover, the system’s error range for obstacle detection falls between 4% and 6.6%, meeting the necessary requirements for obstacle negotiation in the next stage.

This paper studies how to solve the obstacle detection problem when the robot obstacle negotiation.