## 4 Conclusions  
In this paper, a wind tunnel test was conducted on smooth low-aspect-ratio cylinders with \(AR\) = 0.323 and 0.875, respectively. The influence of parameters, including wind fields, \(AR\), and \(Re\), was analyzed by comparing the coefficient of wind pressure, base pressure, local and base force, etc. for two cylinders. The main conclusions reached as a result of the findings are as follows:  
1. The cylinder with \(AR\) = 0.875 has a significant \(Re\) effect, and the distribution of the circular pressure coefficient at different \(Re\) shows the process from sub-criticality to super-criticality. However, due to the stronger free end effect, the \(Re\) effect for \(AR\) = 0.323 is not significant, and the value of the circular pressure coefficient in the negative pressure range is smaller than that of \(AR\) = 0.875. In addition, increasing the incoming turbulence causes the wind pressure distribution to be at a higher \(Re\) state, that is, the supercritical regime is reached at a smaller \(Re\).
2. Aspect ratio is the main factor affecting the value of the base pressure coefficient and positive pressure range. The base pressure coefficient increases with \(AR\), and has a \(Re\) effect for \(AR\) = 0.875. The positive pressure range decreases with \(AR\) and \(Re\), and has large values in the middle-upper part of cylinders. The variation of the base  
Figure 15: The variation of the base force coefficient of models with \(Re\) under different wind fields. (**a**) M1, the mean base force coefficient; (**b**) M1, the fluctuating base force coefficient; (**c**) M2, the mean base force coefficient; (**d**) M2, the fluctuating base force coefficient.  
pressure coefficient and positive pressure range also tends to be at a higher \(Re\) state as turbulence increases.
3. In the transition from sub-criticality to criticality, the local force coefficients for \(AR=0.875\) vary substantially. The mean value of the drag coefficient decreases in the transition, while the lift coefficient reaches its maximum at \(Re=2.6\times 10^{5}\), corresponding to the separation bubble appearing on one side of the cylinder. The fluctuating value of the drag and lift coefficient also reaches its maximum at \(Re=2.6\times 10^{5}\). However, for \(AR=0.323\), only the lift coefficient has a \(Re\) effect at \(Re\leq 2.7\times 10^{5}\). Due to the influence of the free end and turbulence, which may suppress vortex shedding, the power spectrum of the lift coefficient for two cylinders mainly shows broad spectral peaks with \(Re\) and turbulence. In addition, when turbulence is greater than 4.0%, turbulence and \(Re\) have little effect on the mean base force coefficient of low-aspect-ratio cylinders.  
Conceptualization, B.L. and Z.H.; methodology, B.L.; software, Y.T.; validation, B.L. and Z.H.; formal analysis, Z.H.; investigation, M.X.; resources, B.L.; data curation, Z.H.; writing--original draft preparation, Z.H.; writing--review and editing, Z.H.; visualization, S.S.; supervision, B.L.; project administration, B.L.; funding acquisition, B.L. All authors have read and agreed to the published version of the manuscript.  
This research is funded by the National Natural Science Foundation of China (51878041), and the 111 project of the Ministry of Education and the Bureau of Foreign Experts of China (B13002).  
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The authors declare no conflict of interest.