## 4 Conclusions  
The synergistic FIM and the energy conversion capacity of two T-section prisms in tandem were investigated experimentally for various values of the spacing ratio, damping ratios, and Reynolds numbers of 45,263 \(\leq Re\leq\) 116,842, which fall in the TrSL3 flow regime. The results, including oscillatory response, active power, and the efficiency of the two T-section prisms, were analyzed and presented. The effect of load resistances and spacing ratio on energy conversion were presented and discussed separately. The following conclusions can be drawn from the tests conducted. (1) For all the tested spacing ratios, the amplitude of UTP was generally lower than that of STP Except for \(R_{L}\) = 13 \(\Omega\) and 3 \(\leq L\)/\(D\)\(\leq\) 6, the UTP underwent SG instead of the VIV that occurred for STP because of the positive influence from DTP. The amplitude of DTP was also lower than that of STP in general. One particularly notable phenomenon was that the amplitude of DTP continuously increased as the velocity increased and was higher than that of STP for 8 \(\Omega\)\(\leq\)\(R_{L}\)\(\leq\) 13 \(\Omega\) and \(U_{r}\)\(\geq\) 8.5 due to the wake of UTP. (2) The WIM phenomenon was observed for DTP for 6 \(\leq L\)/\(D\)\(\leq\)15 and 8 \(\Omega\)\(\leq\)\(R_{L}\)\(\leq\) 41 \(\Omega\), accompanied by an evident upward trend in the amplitude of DTP with the increase of the flow velocity and a stronger WIM as the spacing ratio increased. (3) In the VIV lower branch, the hydrokinetic power harnessed by UTP + DTP (9.52 W, \(L\)/\(D\) = 15) was much higher than that of STP (0.32 W) at \(U_{r}\) = 12.25, mainly because the wake of UTP had a positive influence on the DTP, resulting in the growth of energy conversion. (4) For UTP and DTP, the active power curves that varied with load resistances crossed each other, and the rules were similar. As the load resistances decreased, the active power increased considerably for 11 \(\Omega\)\(\leq\)\(R_{L}\)\(\leq\) 41 \(\Omega\). (5) For different spacing ratios, both UTP and DTP were suppressed to different degrees due to the mutual interference. Except for \(R_{L}\) = 13 \(\Omega\) and 3 \(\leq\)\(L\)/\(D\)\(\leq\) 6, the UTP output power gradually increased as the velocity increased and underwent soft galloping because of the positive influence from DTP. For 8 \(\Omega\)\(\leq\)\(R_{L}\)\(\leq\) 13 \(\Omega\), the active power of DTP increased as \(U_{r}\)\(\geq\) 8.5. (6) In the tests, the highest active power occurred at \(U_{r}\) = 12.25 for \(L\)/\(D\) = 6, \(R_{L}\) = 11 \(\Omega\), and \(P_{harm}\) = 30.12 W, corresponding to \(\eta_{harm}\) = 9.08%. The highest efficiency reached in this set of tests was 10.04%. It occurred at \(U_{r}\) = 12.25 for \(L\)/\(D\) = 6 and \(R_{L}\) = 11 \(\Omega\), corresponding to \(P_{harm}\) = 21.02 W. The active power of UTP and DTP was lower than that of STP in general. It can be concluded that the active power of UTP + DTP was less than twice that the STP, and the optimal active power of two T-section prisms (30.12 W, \(L\)/\(D\) = 6) in the tests was that of single prism (20.12 W), i.e., 1.5 times for \(R_{L}\) = 11 \(\Omega\). [PERSON] provided methodology. [PERSON] designed the experiments; [PERSON], [PERSON], and [PERSON] performed the experiments; [PERSON] and [PERSON] analyzed the data; [PERSON] built and wrote the majority of the manuscript text; all authors reviewed the manuscript. [PERSON] and [PERSON] made contributions to the structure and language of the manuscript. All authors have read and agree to the published version of the manuscript. This research was funded by [General Program of National Natural Science Foundation of China] grant number [51779166] and [National Natural Science Foundation of China] grant number [No. 51909190]. **Acknowledgments:** This work is supported by the National Natural Science Foundation of China (No. 51909190). All workers from the State Key Laboratory of Hydraulic Engineering Simulation and Safety of Tianjin University are acknowledged.