## 5 Conclusions  
In this study, based on an optimized geometric model of a spiral-cyclone separator, the spiral-cyclone separator prototype for the experiments was designed, and the machining and assembly of the experimental prototype were carried out to build an indoor experimental system for spiral-cyclone in situ separation, and the spiral-cyclone separator performance validation study carried out under ambient conditions as follows:  
(1) According to the actual size of the spiral-cyclone separator for natural gas hydrate, an experimental prototype of a spiral-cyclone separator suitable for indoor experiments was machined and the experimental prototype was assembled to build an indoor experimental system for the in situ separation of silt and sand from the spiral-cyclone separator.  
(2) The comparison between the numerical simulation results and the indoor experimental data demonstrates that, despite minor differences in certain phenomena, the overall trends observed in both are consistent, validating the accuracy of the numerical simulation model. As the inlet pressure and flow rate increase, the pressure drop across the spiral-cyclone separator rises, ranging from 0.032 MPa at 11.4 m\({}^{3}\)/h to 0.13 MPa at 24.3 m\({}^{3}\)/h. Furthermore, higher inlet flow rates lead to increased turbulence intensity in the separator's spiral channel, as evidenced by the calculated inlet velocities.  
(3) The influence of the inlet flow rate of the separator on the separation effect was investigated, and it was found that with an increase in the flow rate, the sediment separation area began to move upward, and the sediment settling area at the bottom showed different degrees of sediment accumulation. When the flowrate is in the range of 5 to 25 m\({}^{3}\)/h, a higher pressure drop correlates with a higher flow velocity. Both the experimental results and numerical simulation results indicate that the separation efficiency increases as the flowrate increases. In the operation experiments with the separator parallel to the ground, with a particle size of 1 mm, the unilateral accumulation will be due to the influence of gravity, but this phenomenon occurs when the silt sand has been separated from the multi-phase mixed slurry.  
Figure 13: Comparison of experimental and simulated phenomena for different action attitudes of the separator.  
**Author Contributions**: Y.H.: writing--original draft, formal analysis, and conceptualization. Y.T.: visualization, validation, data curation, writing--review and editing. Y.Z.: methodology, funding acquisition, writing--review and editing. N.X.: project administration, validation. G.W.: project administration, resources, supervision. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was funded by the State Key Laboratory of Natural Gas Hydrate Open Fund Project [2022-KF]-SHW], China.  
**Institutional Review Board Statement**: Not applicable.  
**Informed Consent Statement**: Not applicable.  
**Data Availability Statement**: Data are contained within the article.  
**Conflicts of Interest**: Author [PERSON] and author [PERSON] were employed by the CNOOC Research Institute Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.