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The landing of a seaplane on the wave is a crucial issue with practical engineering applications in the fields of aeronautical and ocean engineering. The safe landing of seaplanes on wave surfaces prompts an urgent investigation on further understanding the mechanism by which the wings affect loads. This study examines the slamming force characteristics, pressure distributions, and free surface profiles of a two-dimensional seaplane section with varied heel angles into waves, considering different entry velocities, entry locations, and wave steepnesses. The overset mesh technique has been integrated into the waves2Foam toolbox to achieve a numerical wave tank based on the overset mesh. Numerical results for the vertical slamming force, slamming pressure coefficient distribution, and free surface profile were validated against published semi-analytical solutions and laboratory tests. The slamming force during the water entry of the seaplane section under the wave effect shows similar but more complex characteristics than those of the wedge section, manifesting as a phenomenon of multiple peaks. In addition to the bottom slamming of the airframe, localized high-pressure regions appear beneath the wing due to the combined squeezing effect on the air layer by the wing and water particle, which is similar to the wing-in-ground (WIG) effect. Slight sawtooth fluctuations of the wavefront were observed as a consequence of the disturbance of the air layer by the wings. [ABSTRACT FROM AUTHOR]

Objects entering water is a complex multiphase flow event that exhibits nonlinear and transient characteristics. This study examines the impact cavities, multiphase flow characteristics, and motion behaviors of a cylinder during vertical water entry, considering different flow and entry velocities. A three-dimensional model was carried out using OpenFOAM® framework, taking into account the effects of wind and linearly sheared flow through newly customized initial and boundary conditions. The overset mesh technique was applied to capture the water entry trajectories of the moving cylinder. Numerical results for the cavity evolution and cylinder motion behaviors were validated against published laboratory tests. The cavity closure patterns were classified into four categories based on the evolution characteristics, which were found to be more complex than those observed under calm water and uniform current conditions. Furthermore, the rapid closure of the splash dome results in a unique cavity flow phenomenon, which creates a suction air channel. The velocities of the flow and water entry have a noticeable impact on the closure modes and time of the cavity. This, accordingly, affects the motion characteristics of the cylinder, as well as the evolution of the velocity field, pressure field, and vortex structures. [ABSTRACT FROM AUTHOR]

The process of a damaged ship flooding is a complicated free surface flow problem. There is a complex coupling effect between the ship cabin and the flow inside and outside of the cabin. In this paper, a GPU (graphic processing unit)- δ + -SPH (smoothed particle hydrodynamics) numerical model for the cabin flooding in deep-water environments is developed based on GPU parallel acceleration technology and Nvidia's CUDA (compute unified device architecture). First, the computational accuracy and efficiency of this numerical model are verified by experiments results on the water flooding of a simple damaged cabin model. Furthermore, the flooding characteristics of a submarine cabin are analyzed, considering different numbers of damaged cabins, depths, and opening positions. Finally, the progressive flooding and the dynamic response characteristics of a full-scale submarine model are investigated. The results show that the process of progressive flooding in a submarine cabin is characterized by its rapidity and intensity. Different factors, for example, damaged cabin numbers, cabin depths, and opening positions, have great influences on the process of flooding and the motion of the submarine cabin. This study can offer valuable technical assistance in the post-damage remediation process. [ABSTRACT FROM AUTHOR]

For the special ship like catamaran, which has a unique structure with gap resonance, the traditional potential method tends to over-predict the motion at the resonance frequency due to the negligence of fluid viscosity. In this paper, a new method considering damping is put forward to inhibit over-predicted heave and pitch response. Viscous damping is introduced into free surface boundary conditions. Critical damping is added in the motion equations. Numerical simulations of a HEU catamaran and a DUT catamaran are performed. It is found both viscous damping and critical damping can weaken the over-predicted resonant responses. However, the method of adding critical damping is much more efficient at high speeds and the results conform better to the experimental results. [ABSTRACT FROM AUTHOR]

The paper presents an experimental investigation on the nonlinear bending moments of an ultra large container ship over 300 m long in rough waves. The design and calibration procedure of the scaled segmented ship model with variable cross-section backbone beam is introduced. Transfer functions of vertical bending moments at different Froude numbers, wave headings and wave heights are analyzed. Ship responses in harsh waves are analyzed and the largest wave height to wavelength ratio exceeds 1/10. It is interesting and significant to analyze the strongly nonlinear behaviors of the ship in such high waves. The resonance frequencies, proportion of high-order harmonic components, asymmetry of hogging and sagging moments as well as the phase differences between wave-frequency and high-order harmonics in extreme waves are investigated systematically. • Springing in oblique waves is observed and analyzed when wave periods are close to natural period of roll. • Strongly nonlinear phenomena like slamming, green water, water entry and exit are observed from image records. • Up to 11th-order harmonic bending moments are presented in the amplitude spectrum. • Asymmetry of hogging and sagging moments and its causes are investigated. • The proportion and phase differences of wave-frequency and high-order components in extreme waves are discussed. [ABSTRACT FROM AUTHOR]

The hydrodynamic problem of a three dimensional cone entering water in three degrees of freedom is analysed based on the incompressible velocity potential theory. The effect of horizontal motion and rotational motion on the entry process is investigated. The problem is solved through the boundary element method in the time domain. Two physical coordinate systems are constructed. One is the body-fixed system for the solution of fluid velocities and free surface tracking, and the other is the space-fixed system for equations of motion. To match the extremely small wetted surface at the initial stage, the former frame is stretched based on the ratio of physical coordinates and vertical travelled distance. The auxiliary function method is used to decouple the nonlinear mutual dependence between fluid loads and the body motion. Detailed results for cone motion, impact pressure and free surface are provided, and in-depth discussion on the effect of the horizontal motion and rotational motion is given. [ABSTRACT FROM AUTHOR]

Slamming is common when a trimaran sails in rough seas. Owing to the semiclosed structural shape of a trimaran, an air cushion can easily form, reducing the slamming pressure. Therefore, the air-cushion effect during water entry of a trimaran section is investigated in this work. To study the air-cushion effect quantitively, an experimental procedure together with a novel model design is presented. Partly opened acrylic plates are pasted to a trimaran section model and the opening size is changed to control the efficiency of air escape from the front and rear of the model. The formation of the air cushion and the transformation of the water surface are captured by a high-speed camera. The influences of the opening size and the initial release height of the model on the slamming pressure are analyzed to investigate the air-cushion effect. The most novel idea of the present paper is the design of the asymmetrical openings on the front and rear acrylic plates pasted to the symmetrical model. Through this design, the significant difference produced by the air-cushion effect can be clearly distinguished by comparing the left and right halves of the model. Results show that the air cushion can postpone the emergence time of the pressure peak, decrease the magnitude of the pressure peak, and magnify the pressure fluctuation phenomenon. • Water entry of a trimaran section is studied to analyze the air cushion effect on the slamming. • An experimental method to analyze the air cushion by controlling the size of opening is proposed. • The air cushion effect can decrease the peak value of slamming and delay the time. • A strong air cushion effect will greatly reduce the bang peak and cause signal fluctuations. [ABSTRACT FROM AUTHOR]

l -theanine, the most abundant free amino acid in tea, has been documented to possess many different bioactive properties through oral or intragastrical delivery. However, little is known about the effect of topical delivery of l -theanine on acute inflammation. In the present study, by using 12-O-tetradecanoylphorbol-13-acetate (TPA, 2.5 μg/ear)-induced ear edema model in mice, we first found that single-dose local pretreatment of l -theanine 30 min before TPA time- and dose-dependently suppressed the increases in both skin thickness and weight. Subsequently l -theanine ameliorated TPA-induced erythema, vascular permeability increase, epidermal and dermal hyperplasia, neutrophil infiltration and activation via downregulating the expression of PECAM-1 (a platelet endothelial adhesion molecule-1) in blood vessels and the production of pro-inflammatory cytokines IL-1β, TNF-α, and mediator cyclooxygenase-2 (COX-2), which is mainly expressed in neutrophils. It highlighted the potential of l -theanine as a locally administrable therapeutic agent for acute cutaneous inflammation. [ABSTRACT FROM AUTHOR]

Background: Nonalcoholic fatty liver disease (NAFLD) is a chronic metabolic disease that easily induces hepatitis, cirrhosis, and even liver cancer. The long-term use of NAFLD therapeutic drugs produces toxicity and drug resistance. Therefore, it is necessary to develop high efficiency and low-toxicity active ingredients to alleviate NAFLD., Objective: This study aimed to reveal the role and mechanism of a new functional food CMT in alleviating NAFLD., Results: In the ob/ob fatty liver mice models, the CMT extracts significantly inhibited the weight gain of the mice and reduced the accumulation of white fat. The anatomical and pathological results showed that CMT relieved fatty liver in mice and reduced excessive lipid deposition and inflammatory infiltration. Serological and liver biochemical indicators suggest that CMT reduced dyslipidemia and liver damage caused by fatty liver. CMT obviously activated the adenosine 5'-monophosphate-activated protein kinase (AMPK)/acetyl-coA carboxylase (ACC) and AMPK/fatty acid synthase (FAS) signaling pathways, promoted fat oxidation, and inhibited synthesis. Moreover, CMT regulated the expression of inflammatory factors to relieve hepatitis caused by NAFLD., Conclusion: The study explained the role and mechanism of CMT in alleviating NAFLD and suggested that the active ingredients of CMT might be beneficial in NAFLD therapy., Competing Interests: All authors declare no conflict of interest. This study was funded by the National Natural Science Foundation of China (81803236, 31800295, and 81903319). Guangdong Basic and Applied Basic Research Foundation (2020A1515011266), Guangzhou Science and Technology program (202002030202), Guangdong Science and Technology program (2017A070702004, 2016B090918118, and 2018KJYZ002), QingYuan Science and Technology Program (DZXQY021 and DZXQY016), ShaoGuan Science and Technology Program (2018CS11902), YingDe Science and Technology Board (JHXM2018029), Special fund for scientific innovation strategy-construction of high level Academy of Agriculture Science (R2019PY-JX004, R2018YJ-YB3002, R2016YJYB3003, R2018PY-QF005, and R2018QD-101), Department of Science and Technology of Jiangmen (NO. 2016350100170008351 and 2018110100330005446), and Department of Education of Guangdong Province (No. 2016KCXTD005 and 2017KSYS010)., (© 2022 Shuai Wen et al.)