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The orifice plate has the advantages of convenient construction, high energy dissipation efficiency, and economy, and is widely used in hydropower engineering and discharge engineering. The recovery length of the flow pressure behind the orifice plate is related to the distance arrangement between orifice plates in multi-stage orifice plate design. However, little research has been conducted on the pressure recovery length behind the orifice plate. The numerical simulation method is used to quantitatively study the influencing factors of the pressure recovery length behind the orifice plate, and the results show that the recovery length of the flow pressure behind the orifice plate is mainly dominated by the aperture ratio of orifice plate, the relative thickness of the orifice plate, and the Reynolds number of fluids flowing through orifice plate. As the Reynolds number increases to a fixed value, the pressure recovery length behind the orifice plate does not change. When the relative thickness of the aperture ratio of the orifice plate are within a certain range, the relative thickness of the orifice plate will not change, the aperture ratio of the orifice plate decreases, and the pressure recovery length behind the orifice plate increases. As the diameter ratio of orifice plate remains unchanged, the relative thickness of the orifice plate increases, and the pressure recovery length behind the orifice plate decreases. The empirical formula for the pressure recovery length behind the orifice plate is obtained by multivariate regression analysis and curve fitting, and the indoor test verification is adopted, which provide theoretical basis for distance arrangement between orifice plates in multi-stage orifice plate design.

The prediction of vessel trajectories plays a crucial role in ensuring maritime safety and reducing maritime accidents. Substantial progress has been made in trajectory prediction tasks by adopting sequence modeling methods, containing recurrent neural networks (RNNs) and sequence-to-sequence networks (Seq2Seq). However, (1) most of these studies focus on the application of trajectory information, such as the longitude, latitude, course, and speed, while neglecting the impact of differing vessel features and behavioral preferences on the trajectories. (2) Challenges remain in acquiring these features and preferences, as well as enabling the model to sensibly integrate and efficiently express them. To address the issue, we introduce a novel deep framework VEPO-S2S, consisting of a Multi-level Vessel Trajectory Representation Module (Multi-Rep) and a Feature Fusion and Decoding Module (FFDM). Apart from the trajectory information, we first defined the Multi-level Vessel Characteristics in Multi-Rep, encompassing Shallow-level Attributes (vessel length, width, draft, etc.) and Deep-level Features (Sailing Location Preference, Voyage Time Preference, etc.). Subsequently, Multi-Rep was designed to obtain trajectory information and Multi-level Vessel Characteristics, applying distinct encoders for encoding. Next, the FFDM selected and integrated the above features from Multi-Rep for prediction by employing both a priori and a posteriori mechanisms, a Feature Fusion Component, and an enhanced decoder. This allows the model to efficiently leverage them and enhance overall performance. Finally, we conducted comparative experiments with several baseline models. The experimental results demonstrate that VEPO-S2S is both quantitatively and qualitatively superior to the models. [ABSTRACT FROM AUTHOR]

The energy loss coefficient, relating directly to the energy dissipation ratio, is an important index of this energy dissipater. In this article, this coefficient and its affecting parameters were analyzed by theoretical considerations, and their relationships were obtained by numerical simulations. It could be concluded that the energy loss coefficient of sharp-edged orifice plate and its backflow region length were mainly dominated by the contraction ratio of the orifice plate. Sharp-edged orifice plate’s energy loss coefficient and its backflow region length all increase slightly with the increase in its thickness. When Reynolds number is in the range of 9.00×10 4 –10.3×10 6 , Reynolds number has little impacts on energy loss coefficient and backflow region length. Two empirical expressions, relating to backflow region length and energy loss coefficient, respectively, were presented.

Plug energy dissipater, as a kind of effective energy dissipater with economic characteristics, has become very popular. The energy loss coefficient and the minimum wall pressure coefficient of the plug are two important factors in the plug energy dissipater design. In this paper, the two coefficients and relative parameters, such as the contraction ratio of the plug diameter to the flood discharge tunnel diameter, the ratio of the plug thickness to the tunnel diameter, and the Reynolds number of the flow through the plug, were analysed by theoretical considerations, and their relationship expressions were obtained by numerical simulations and were verified by experimental data. It could be concluded that the two coefficients were mainly dominated by the contraction ratio of the plug. The lower contraction ratio of the plug is, the larger are the two coefficients. The research results demonstrate that effects of the Reynolds number on the two coefficients can be neglected when this number is greater than 105; the relative thickness of the plug has little impact on them and can be neglected. [ABSTRACT FROM AUTHOR]