## 1 Introduction  
New alternative energy natural gas hydrate has received extensive attention due to its huge development potential [1, 2]. Previous studies have shown that there is a large number of natural gas hydrates in the northern part of the South China Sea, and trial production was completed in May 2017 [3, 4, 5]. However, there are serious sand production problems in the process of exploitation, which will lead to the low efficiency of pipeline transportation, poor continuous production capacity, the collapse of goal reservoirs, the blockage and wear of equipment, engineering geological risk, and equipment failure [6, 7]. These problems have seriously hindered the development of key technologies and equipment for natural gas hydrate exploitation.  
To solve the above problems, considering that separators are widely used in the petroleum, chemical, and other industries because of their high impurity removal efficiency, large processing capacity, simple operation and structure, and low cost [8, 9, 10]. Subsequently, some scholars have researched the application of separators in the field of sand removal in the process of natural gas hydrate exploitation. [PERSON] [11] validated hydrocyclone performance through CFD and experiments, focusing on geometric parameters and their effects on separation efficiency. [PERSON] [12] emphasized the separation of NGH fragments from sands, achieving a high recovery efficiency of 99.8% through experimental validation. [PERSON] [13] investigated the impact of inlet structure on hydrocyclone performance using numerical simulations and experimental data, optimizing a design for NGH separation. However, these studies primarily focus on specific scenarios such as solid-fluid separation or NGH-sand consolidation, leaving the unique challenges of mud/sand separation in NGH exploitation underexplored. [PERSON] [14] proposed a sand removal scheme combining a water mixing viscosity reduction and hydrocyclone separation. A computational fluid dynamics numerical simulation method was used to study the sand removal characteristics of a water-bearing heavy oil hydrocyclone. [PERSON] [15] designed a downhole spiral gas-liquid separator and carried out numerical simulation analysis on the separator. [PERSON] [16] conducted a numerical study on a tangential inlet cyclone separator with spiral guide vanes.  
In summary, few researchers have verified the results of numerical simulation analysis. The aim here is to qualitatively understand the performance of the separator in separating mud and sand from a natural gas hydrate slurry, based on the relevant numerical study of the spiral-swirl coupling separator conducted by our team and some typical results of the spiral-swirl separator. Therefore, the numerical simulation results of the spiral-swirl separator are experimentally verified in this study. In order to simulate the actual production conditions of natural gas hydrate spiral-swirling flow separation as far as possible, the natural gas hydrate spiral-swirling flow separation device used in the experiment was processed, and an indoor experimental system was built. The pressure loss experiment for the hydrate separation device was carried out to verify the accuracy of the designed spiral-swirl separator's numerical simulation model and the calculation results' accuracy. The influence of the inlet flow rate and the working attitude on separation efficiency were tested to study the influence of different working conditions on the separator's performance. The results of this study can provide a feasible reference for numerical simulation analysis and verification of downhole separators.