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Physical experiments were conducted in an impounded channel to study the propagation of negative surges advancing in still water and evolution of undular surges against an instantaneously varied flow. The results demonstrated that the initial wave height of a negative surge could be accurately predicted using the simple wave solution of the Saint–Venant equations. Moreover, the wave height evolution during surge propagation could be satisfactorily described using the solution by Ippen and Kulin. The main characteristics of an undular surge were strongly correlated to the surge Froude number and turbulent boundary layer development at the toe of the surge. However, the occurrence of wave breaking at the first wave crest was independent of the inflow conditions and was close to the breaking criterion for solitary waves. Furthermore, the present results indicated the largest turbulent Reynolds stress components beneath the wave crests of an undular surge. [ABSTRACT FROM AUTHOR]

The study of the vibration phenomenon of pebbles under turbulence is still a gap despite recent technological advancements in measurement capabilities. In this study, the vibration process of a fully exposed, isolated smart pebble on a rough bed was measured using a miniature inertial accelerometer and combined with simultaneous local measurements of the near-bed velocities. The paper conducts a series of experimental studies with different flow conditions. The test data match well with the manually observed phenomena, indicating the authenticity of the sediment vibration data collected by the measurement system. The test results show that the pebble motion (before entrainment) subjected to turbulence is a nonlinear vibration process, and its vibration types include in-situ vibration and ex-situ strong vibration. The probability distribution for the amplitude of vibration acceleration is well parameterized by the normal distribution. The vibration intensity tends to increase before approaching the threshold, but it weakens when approaching the point. The sediment vibration frequency is within 20–25 Hz, similar to the flow pulsation frequency and belongs to low-frequency vibration. The data indicate that the near-bed flow velocity is most directly related to the particle vibration events. [ABSTRACT FROM AUTHOR]

Bank slopes are an important part of river ecosystems. In recent years, a series of ecological engineering projects with ecological functions have been implemented in the middle and lower reaches of the Yangtze River. In this study, we designed a new type of ecological slope-protection structure for rivers. Through physical model tests, the hydraulic characteristics of the structure, such as velocity, turbulence intensity, and Reynolds stress, at different test conditions were analyzed. These characteristics were then compared with those of an open channel with vegetation. The distributions of hydraulic properties determined in the open-channel tests involving the new structure were similar for different experimental conditions. Velocity and turbulence intensity are hyperbolic along the normal direction, whereas the Reynolds stress is close to zero. Several inflection points were observed in each distribution of hydraulic properties. The inflection point at the top is due to variations in the water flow conditions. On the outside, a second inflection point occurs because the water flow fluctuates violently near the new structure. The distribution of hydraulic properties in the far water layer is similar to that observed in a soft bed test. This study provides foundational knowledge for the future development of ecological slope-protection structures. A new ecological slope-protection structure is proposed. The distribution of hydraulic characteristics of an open channel with the new structure is analyzed. The zoning of shore slopes for the construction of the new structure is presented. The hydraulic characteristics of an open channel with the new structure and of an open channel with vegetation are compared. [ABSTRACT FROM AUTHOR]

Physical experiments were conducted in a long water wave tank over a wide range of still water depths to study the evolution and runup of nonbreaking undular surges generated by the release of a given volume of water. The results demonstrated that the wavefront of a nonbreaking undular surge closely matched that of the corresponding solitary wave of the same height. The wave celerity of the surge could be accurately predicted using the solitary wave theory. Two distinct wave stages existed in the evolution process of a nonbreaking undular surge based on the wave shape asymmetry. The wave stage transition could be approximated as a surge Froude number equal to 1.15. The wave amplitude and steepness of undular surges were in reasonable agreement with the linear wave theory for surge Froude numbers greater than 1.20. However, the wave length data presented a different pattern to that predicted by either the linear wave theory or the solution of the Boussinesq equation. Furthermore, the maximum surge runup on a vertical wall was in excellent agreement with the solitary wave theory. This study provided new insights into the quantitative behavior of nonbreaking undular surges. [ABSTRACT FROM AUTHOR]

Subaerial landslides sliding into shallow water are physically modeled in a three-dimensional wave basin. The generated impulse waves are highly nonlinear, and a large-scale splash zone is formed above the waves. Such impulse wave characteristics are different from those from landslides into deep water that are completely submerged after sliding. The recorded wave profiles included three wave types, namely nonlinear oscillatory wave, nonlinear transition wave and bore-like wave, mainly depending on the relative slide thickness and slide Froude number at impact. Bore-like waves were possible produced only by landslides into shallow water in three-dimensional experiments. The conversion rate of landslide kinetic energy at impact into the wave train energy is 1 to 18%. Energy conversion characteristics are compared with other two- and three-dimensional studies on landslide-generated waves and the results are discussed. [ABSTRACT FROM AUTHOR]

Impulse waves generated by landslides lead to serious secondary disasters. To investigate the effects of impulse waves on a bank slope, a three-dimensional physical model test was conducted considering multiple factors, such as the width, thickness, and volume of the landslide body, inclination angle of the landslide, and bank slope angle. The results show that the wave did not break upon the first crest. And the waves break and swirl locally when fallback water flowed into the trough. The pressure acting upon the bank slope included pulsating pressure and impact pressure, of which the latter was largely affected by repeated tests, measuring frequencies, and measurement point densities. The existing empirical formulas cannot accurately reflect the wave pressure on the bank slope under the action of landslide-generated impulse waves. The maximum pulsating pressure increased proportionally with width, thickness, volume and inclination angle of the landslide body. This study better restores the interaction process between landslide, impulse waves and bank slope in actual river channels, and provides relevant support for the formulation of water pressure prediction formulas. [ABSTRACT FROM AUTHOR]

Because of the complex geological conditions of the seabed, submarine pipelines buried beneath the ocean floor become suspended over the seabed under the long-term scour of waves eroding the surrounding sediment. Further, most oil fields were built in offshore areas while the country was developing. This gives the waves seen in shallow water obvious nonlinear features, and the abnormal characteristics of these waves must be considered when calculating their hydrodynamic forces. Particularly under such conditions, these suspended spans of submarine pipelines are prone to damage caused by the action of the external environment load. Such damages and eventual failures may result not only in great property losses but also pollution of the marine environment. The span length of these areas is a key predictive factor in pipeline damages. Therefore, determining the allowable span length for these submarine pipelines will allow future projects to avoid or prevent damage from excessive suspended span lengths. Expressions of the hydrodynamic loads placed on suspended spans of pipeline were developed in this work based on the first-order approximate cnoidal wave theory and Morison equation. The formula for the allowable free span length was derived for the common forms of free spanning submarine pipeline based on the point where maximum bending stresses remain less than the material’s allowable stress. Finally, the allowable free span length of real-world pipelines was calculated for a subsea pipeline project in Bohai Bay. This research shows that, with consideration for the complicated marine environment, existing suspended spans are within allowable length limitations. However, continuing to limit the length of these submarine pipeline spans in the Nanpu oil field will require ongoing attention. [ABSTRACT FROM AUTHOR]

Acute lung injury is a fatal condition characterized by excessive inflammation responses. Salidroside, the active constituent of Rhodiola rosea , possesses properties including anti-oxidation, anti-aging, anti-inflammatory, anti-hypoxia, and anti-cancer activities. In the present study, Salidroside attenuated acute lung injury via inhibition of inflammatory cytokine production. Rats pre-treated with Salidroside showed attenuated lipopolysaccharide (LPS)-induced pathological damage and suppressed tumor necrosis factor-alpha (TNFα) and interleukin 6 (IL-6) secretion in the lung. Furthermore, flow cytometry showed that Salidroside reduced the production of TNFα and IL-6 in NR8383 alveolar macrophages. These findings suggest that Salidroside may attenuate LPS-induced acute lung injury. • Sal attenuates LPS-induced pathological damage and decreases the W/D lung ratio. • Sal suppresses TNFα, IL-6, and GM-CSF secretion in the ALI model. • Sal inhibits TNFα, IL-6, and GM-CSF transcription in lung tissues in the ALI model. • Sal reduces TNFα and IL-6 production induced by LPS in NR8383 cells. [ABSTRACT FROM AUTHOR]