The current research proposed the theoretical model for ship twin-propeller jet based on the axial momentum theory and Gaussian normal distribution. The twin-propeller jet model is compared to the more matured single propeller jet model with good agreement. Computational Fluid Dynamics (CFD) method is used to acquire the velocity distribution within the twin-propeller jet for understanding of flow characteristics and validation purposes. Efflux velocity is the maximum velocity within the entire jet with strong influences by the geometrical profiles of the blades. Twin-propeller jet model showed four-peaked profile at the initial plane downstream to the propeller compared to the two-peaked profile from a single-propeller. The four-peaked profile merges to be two-peaked velocity profile and then one-peaked profile due to the fluid mixing. Entrainment occurs between the ambient still water outside and the rotating flow within jet due to the high velocity gradient. The research proposes a twin-propeller jet theory with a serial of equations enabling the predictions of velocity magnitude within the jet.

The wake from a tidal current turbine has a significant impact on a tidal farm. A single turbine wake would affect the turbine located adjacent or downstream. Two equations are proposed to predict the mean velocity within the wake of a vertical-axis turbine. The first equation used to predict the efflux velocity is derived based on the axial momentum theory and dimensional analysis. Efflux velocity is the minimum velocity closest to the turbine downstream. The second equation used to predict the lateral velocity distribution is derived based on Gaussian probability distribution. The predictions are compared with the existing experimental and numerical results. Validation of the equations gives a variation in the range of 0-1.13% for the efflux velocity by comparing the proposed theoretical works and Dai and Lam's experimental measurements. These equations are the foundation of the analytical method for wake prediction of a vertical-axis turbine.

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We explored the effect of self-serving leadership on employees' helping behavior, focusing on the mediating role of moral disengagement and the moderating role of prosocial motivation. We recruited employees and direct supervisors of six companies in China, and analyzed data from 295 participants using structural equation modeling and hierarchical regression. Self-serving leadership had a significant negative impact on employees' helping behavior, and moral disengagement mediated the relationship between self-serving leadership and employees' helping behavior. Further, prosocial motivation moderated this relationship, that is, the stronger (vs. weaker) was the prosocial motivation of employees, the weaker (vs. stronger) was the effect of self-serving leadership on employees' helping behavior.

The efflux velocity is the basis for the prediction of turbine wake. A novel energy coefficient is defined to propose a new theoretical equation to predict the efflux velocity of tidal current turbine in this paper. Several CFD cases with different tip speed ratio and solidity is conducted using the DES-SA model. In order to overcome the limitations of the axial momentum theory, the effects of tip speed ratio and solidity on the efflux velocity are studied and the energy coefficients with different tip speed ratio and solidity are determined using the proposed equation based on the CFD results. Several semi-empirical efflux velocity equations are finally proposed by fitting the equation of the energy coefficient with tip speed ratio. The application of these equations in the prediction of wake flow and the power calculation of tidal turbine are also introduced in this paper.