Since the first impoundment of Three Gorges Dam in 2003, algal blooms occur frequently in the near-dam tributaries. It is widely recognized that the impoundment-induced change in hydrodynamic condition with the lower current velocity will make the eutrophication problem even more severe when an excessive amount of nutrients is already loaded into a reservoir and/or its tributaries. Operation tests carried out by Three Gorges Corporation in 2010 point to some feasible reservoir operation schemes that may have positive impacts on reducing the algal bloom level. In our study, an attempt is made to obtain, through a numerical hydrodynamic and water quality modeling and analysis, the reservoir operation rules that would reduce the level of algal blooms in the Xiangxi River (XXR), a near-dam tributary. Water movements and algal blooms in XXR are simulated and analyzed under different scenarios of one-day water discharge fluctuation or two-week water level variation. The model results demonstrate that the reservoir operations can further increase the water exchange between the mainstream of the Three Gorges Reservoir (TGR) and the XXR tributary and thus move a larger amount of algae into the deep water where it will die. Analysis of the model results indicate that the water discharge fluctuation constituted of a lower valley-load flow and a larger flow difference for the short-term operation (within a day), the rise in water level for the medium-term operation (e.g., over weeks), and the combination of the above two for the long-term operation (e.g., over months) can be the feasible reservoir operation rules in the non-flood season for TGR.

The flow induced vibration and energy extraction of an equilateral triangle prism elastically mounted in a water channel are investigated experimentally at different system damping ratios ζ_total with the constant oscillating mass M_osc and system stiffness K. A power take-off system with a variable damping function is developed. The translation-rotation equation of the vibration system deduced in the study indicates that the total oscillating mass includes the material mass, and the equivalent mass due to the rotation of the gears and rotor. Besides, increasing load resistance can result in a decrease in ζ_total when K and M_osc remain unchanged. The prism experiences, in turn, soft galloping, hard galloping 1 and hard galloping 2 with increasing ζ_total. As ζ_total increases up to 0.335, only the vortex-induced vibration is observed because the extremely high ζ_total prevents the prism from galloping. The response amplitude decreases with the increasing ζ_total. In addition, higher ζ_total promotes the galloping to start at a higher reduced velocity. The galloping characteristics of the prism, including large amplitude responses in an extremely large range of flow velocities, excellent vibration stationarity, and steady vibration frequencies, are beneficial for improving energy conversion. The prism can extract hydraulic energy for the flow velocity U > 0.610 m/s. The harnessed power P_out and the energy conversion efficiency η_out increase with increasing ζ_total in the galloping zone. The maximum P_out and η_out reach 53.56 W and 40.44%, respectively. The optimal system damping ratio for extracting energy is the maximum system damping ratio that the prism can overcome to experience stable galloping.

Artificial air entrainment has been widely used to avoid cavitation damage in spillways where high-velocity flow occurs, and its performance is very important for spillway safety. In order to evaluate the performance of the aeration system in the spillway tunnel of the Jinping-I Dam, which is the highest arched dam in the world to date, systematic prototype observation was conducted. Ventilation characteristics of the air supply system and aeration-related characteristics of the aeration devices were examined at the prototype scale. The results showed that air flows smoothly in the air intake well and the real effect of air entrainment of the aeration device was desirable. In contrast with results from laboratory tests with a physical model at a scale of 1/30 following the gravity similarity, it was found that air demand in the prototype is much greater, clearly indicating the scale effect. By summing up and analyzing the air demand ratio of the prototype to the model in some projects, the scale effect was found to be ignorable when the model scale was greater than 1/10. In addition, based on a series of prototype data on air demand, a brief evaluation of present calculation methods for air demand was conducted and a new form of calculation method for air demand related to unit width flow rate was established. The present prototype results can be used as a reference for similar engineering design, and to validate and verify numerical simulations as well as model tests.

Flow-induced motion (FIM) performs well in energy conversion but has been barely investigated, particularly for prisms with sharp sections. Previous studies have proven that T-section prisms that undergo galloping branches with high amplitude are beneficial to energy conversions. The FIM experimental setup designed by Tianjin University (TJU) was improved to conduct a series of FIM responses and energy conversion tests on a T-section prism. Experimental results are presented and discussed, to reveal the complete FIM responses and power generation characteristics of the T-section prism under different load resistances and section aspect ratios. The main findings are summarized as follows. (1) Hard galloping (HG), soft galloping (SG), and critical galloping (CG) can be observed by varying load resistances. When the load resistances are low, HG occurs; otherwise, SG occurs. (2) In the galloping branch, the highest amplitude and the most stable oscillation cause high-quality electrical energy production by the generator. Therefore, the galloping branch is the best branch for harvesting energy. (3) In the galloping branch, as the load resistances decrease, the active power continually increases until the prism is suppressed from galloping to a vortex-induced vibration (VIV) lower branch with a maximum active power P_harn of 21.23 W and a maximum η_out of 20.2%. (4) Different section aspect ratios (α) can significantly influence the FIM responses and energy conversions of the T-section prism. For small aspect ratios, galloping is hardly observed in the complete responses, but the power generation efficiency (η_out,0.8 = 27.44%) becomes larger in the galloping branch.

Better understanding of the complex mechanical properties of ice is the foundation to predict the ice fail process and avoid potential ice threats. In the present study, uniaxial compressive strength and fracture mode of natural lake ice are investigated over moderate strain-rate range of 0.4–10 s⁻¹ at −5 °C and −10 °C. The digital speckle correlation method (DSCM) is used for deformation measurement through constructing artificial speckle on ice sample surface in advance, and two dynamic load cells are employed to measure the dynamic load for monitoring the equilibrium of two ends’ forces under high-speed loading. The relationships between uniaxial compressive strength and strain-rate, temperature, loading direction, and air porosity are investigated, and the fracture mode of ice at moderate rates is also discussed. The experimental results show that there exists a significant difference between true strain-rate and nominal strain-rate derived from actuator displacement under dynamic loading conditions. Over the employed strain-rate range, the dynamic uniaxial compressive strength of lake ice shows positive strain-rate sensitivity and decreases with increasing temperature. Ice obtains greater strength values when it is with lower air porosity and loaded vertically. The fracture mode of ice seems to be a combination of splitting failure and crushing failure.