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.

This paper comprehensively summarizes and discusses the latest research progress in the underwater concrete structure damage repair technology of infrastructures. The prompt application of underwater concrete structure repair technology can effectively deal with the damaged parts of underwater concrete structures, and it can ensure the safe and stable operation of infrastructure and extend its service life. Firstly, this study uses bibliometric methods to analyze the characteristics of the literature on research into underwater concrete repair in the past 30 years (1993–2023), and expounds the research status and hotspots of this field. Then, we conduct a comprehensive classification and discussion of the underwater concrete structure damage repair technologies at the current stage. This technology can be divided into two major types: direct underwater type and dry environment type. Further, the development history of these technologies is systematically sorted out and, combined with practical engineering application cases, the operation processes, applicability, limitations, and economy of these technologies are analyzed. Finally, the challenges and future development trends of the current underwater concrete structure damage repair technology are pointed out, which provides a direction for future research on the intelligent maintenance of underwater concrete structures.

The impoundment and power generation of dams cause the temperature of released water much lower than the original rivers in the thermal stratified reservoirs. In addition, the released low-temperature water would damage the downstream habitats of fish and other biological groups seriously. Available facilities, such as stop log gate intakes and multi-level intakes, are built to alleviate the problem. For overcoming the limitations of traditional facilities on construction conditions and the improved effect of water temperature, a new facility of the temperature control curtain (TCC), with the advantages of convenient regulation and no hydropower loss, has been proposed recently. However, to the author’s knowledge, the theory of TCC is not abundant, with incomplete experimental tests and few numerical simulations. In this paper, a rectangular tank is designed specifically to conduct experimental tests to verify the effects of TCC and explore its potential impacts on released water temperature (RWT) under four major influencing factors. The study results show that TCC has significant effects on improving RWT, with a maximum increase of 8.3 °C. In addition, a three-dimensional hydrodynamic model with the same size of experimental model is established for further research. The results show that RWT is mainly related to the temperature distribution of a reservoir and the water-retaining proportion of the curtain. Finally, a basic principle for TCC construction is proposed and all these laid an important theory foundation for its application in engineering practice.

A series of experimental tests on flow-induced motion (FIM) and energy conversion of two rigidly coupled triangular prisms (TRCTP) in tandem arrangement were conducted in a recirculating water channel with the constant oscillation mass m_osc. The incoming flow velocity covered the range of 0.395 m/s ≤ U ≤ 1.438 m/s, corresponding to the Reynolds number range of 3.45 × 10⁴ ≤ Re ≤ 1.25 × 10⁵. The upstream and downstream triangular prisms with a width of 0.1 m and length of 0.9 m were connected by two rectangular endplates. Seven stiffness (1000 N/m ≤ K ≤ 2400 N/m), five load resistances (8 Ω ≤ R_L ≤ 23 Ω), and five gap ratios (1 ≤ L/D ≤ 4) were selected as the parameters, and the FIM responses and energy conversion of TRCTP in tandem were analyzed and discussed to illustrate the effects. The experimental results indicate that the “sharp jump” phenomenon may appear at L/D = 2 and L/D = 3 significantly, with substantially increasing amplitude and decreasing oscillation frequency. The maximum amplitude ratio in the experiments is A*_Max = 2.24, which appears after the “sharp jump” phenomenon at L/D = 3. In the present tests, the optimal active power P_harn = 21.04 W appears at L/D = 4 (U_r = 12.25, K = 2000 N/m, R_L = 8 Ω), corresponding to the energy conversion efficiency η_harn = 4.67%.

The flow-induced rotational motion of tandem double cylinders has rarely been studied in existing papers. In order to further study the flow-induced rotation (FIR) of two mechanically tandem-coupled cylinders, an FIR device was designed in this paper, and the theoretical basis of this system was established. On this basis, a series of variable spacing ratio (L/D) tests were carried out in a recirculating water tunnel. The range of L/D was 4.0 ≤ L/D ≤ 9.0. The main experimental conclusions can be summarized as follows: (1) When L/D = 4.0 and 4.5, the rotational response was similar to vortex-induced vibration (VIV), which is different from typical VIV, in that the rotational oscillation would appear to be a re-growth region when velocitycontinued to increase after the oscillation entered the lower branch of VIV. Additionally, the oscillation was at a low level and the maximum arc length ratio (A*) was less than 0.55 in these two cases; (2) For L/D = 5.0, 5.5 and 6.0, the rotational responses all showed typical VIV. When the oscillation reached a high level, the maximum A* was more than 0.85 for each case; (3) When L/D = 7.0, 8.0 and 9.0, the rotational responses still presented typical VIV. The oscillation was at a medium level, and the maximum A* was between 0.53 and 0.72, but these three cases had a wider synchronization interval than the other cases, and the range showed an increasing trend with the growth of L/D.

The advantageous performance in terms of energy conversion for the flow-induced motion (FIM) of T-section prisms has been experimentally reported recently. In order to further understand the oscillation and energy conversion of multiple T-section prisms, a series of tests of two T-section prisms arranged in tandem with five different spacing ratios (3 ≤ L/D ≤ 15) and seven load resistances (8 Ω ≤ R_L ≤ 41 Ω) were conducted. The effects of the spacing ratio and load resistances on energy conversion were discussed. The main conclusions can be summarized as follows. For most tests, the amplitudes of the upstream T-section prism (UTP) and downstream T-section prism (DTP) were both lower than the amplitude of the single T-section prism (STP) due to the mutual interference of the two prisms. Because of the mutual interference, the active powers of UTP and DTP were both less than that of STP, but at some special spacing ratios or load resistances, the mutual interference benefited the energy converted by the two prisms. In the presented tests, the total optimal active power of the upstream T-section prism and downstream T-section prism (UTP + DTP) was 30.12 W, which was 1.5 times that of STP (20.12 W).