Research on hydrodynamic characteristics of cylinder planing

This paper selects SST k-w turbulence model and VOF wave to construct a numerical calculation model of moving body planning on a flat free surface based on STAR-CCM+ numerical simulation software. The construction model is checked through foreign classic literature, and the numerical simulation results are in good agreement with the experimental results. The hydrodynamic numerical errors are less than 5%, which is within the engineering error range. The model can be used for the numerical simulation of the planning cylinder. In this paper, it is used to simulate the planing process of cylinder with different speeds and different submerged depths, and the flow field characteristics and hydrodynamic characteristics in the planing process are obtained. The results show that waves appear at the tail and the tail liquid splashes to form a water splash during the planing process of the cylinder on a flat surface. The higher the speed of the planning cylinder is, and the deeper the submersion depth, the more pronounced waves at the tail. When the cylinder has a Fr number Cv≥8, the hydrodynamic force of the cylinder is almost unchanged, and it is not affected by the speed. But when Cv=3, the hydrodynamic characteristic coefficient is higher. The drag coefficient is 20% higher than that in the high-speed (Cv≥8) planing process. The lift coefficient is 3 times of high-speed planing lift coefficient. It is related to the surface pressure and frictional force distribution of cylinder during the low-speed planing. There is a linear relationship between the drag coefficient and the submerged depth during the cylinder planing at different submerged depths.

Construction and performance analysis of data warehouse based on ship propulsion system

A large number of operation data will be generated in the process of ship propulsion system operation. Aiming at the processing, analysis and application of these operation data, a data warehouse for propulsion system is constructed based on the operation data of a ship, and the multidimensional analysis and result display of data are realized by combining OLAP technology with visual analysis software tableau. On the basis of the data warehouse, the soft sensing of parameters is applied to the data warehouse. Based on the soft sensing data, the hydrodynamic characteristics of the propeller are studied, and the hydrodynamic characteristic curves of the propeller are obtained. The research of ship propulsion system based on data warehouse provides support for the comprehensive information of propulsion system data.

RESEARCH OF HYDRAULIC RESISTANCE OF VORTEX RECTIFICATION STAGES

The article deals with the issue of studying the hydraulic resistance of vortex contact stages for rectification equipment used for separation of alcohol-containing solutions obtained on the basis of hydrolysate of vegetable raw materials. Based on the conducted research, the dependences for determining the hydraulic resistance coefficient for axial and tangential swirlers are obtained. It is shown how the design parameters affect the change in the coefficient of hydraulic resistance. Hydraulic resistance is an important hydrodynamic characteristic of contact stages, which characterizes the energy consumption of the gas flow for the mass transfer process and determines the scope of its application in practice. Knowledge of the amount of hydraulic losses in the device is also necessary when calculating the schemes of technological strapping of the device. Currently, there are numerous data on the study of regularities in the domestic and foreign literature.

Numerical Modelization of the Oil Film Pressure for a Hydrodynamic Tilting-Pad Thrust Bearing

This study analyses the hydrodynamic characteristic of the tilting pad thrust bearing. Research content is simultaneously solving the Reynolds equation, force equilibrium equation, and momentum equilibrium equations. Reynolds equation is solved by utilizing the finite element method with Galerkin weighted residual, thereby determines the pressure at each discrete node of the film. Force and momentums are integrated from pressure nodes by Gaussian integral. Finally, force and momentum equilibrium equations are solved using Newton-Raphson iterative to achieve film thickness and inclination angles of the pad at the equilibrium position. The results yielded the film thickness, the pressure distribution on the whole pad and different sections of the bearing respected to the radial direction. The high-pressure zone is located at the low film thickness zone and near the pivot location.

Hydraulic Modeling and Evaluation Equations for the Incipient Motion of Sandbags for Levee Breach Closure Operations

Open channel levees are used extensively in hydraulic and environmental engineering applications to protect the surrounding area from inundation. However, levees may fail to produce an unsteady flow that is inherently three dimensional. Such a failure may lead to a destructive change in morphology of the river channel and valley. To avoid such a situation arising, hydraulic laboratory modeling was performed on an open channel levee breach model capturing velocity, in x, y and z plans, at selected locations in the breach. Sandbags of various shapes and sizes are tested for incipient motion by the breach flow. We found that a prism sandbag has a better hydrodynamic characteristic and more stability than spherical bags with the same weight. Experimental results are then used to evaluate existing empirical equations and to develop more accurate equations for predicting critical flow velocity at the initial stage of sandbag motion. Results showed the superior predictions a few of the equations could be considered with an uncertainty range of ±10%. These equations explained the initial failed attempts of the United States Army Corps of Engineers (USACE) for breach closure of the case study, and confirmed the experimental results are simulating the case study of breach closure.