# Wind Tunnel Test on Windblown Sand Two-Phase Flow Characteristics in Arid Desert Regions
## 3 Experimental Results and Discussion  
### Wind Tunnel Simulation of the Measured Impurity-Free Wind Flow Field  
The sand transport characteristics and interaction mechanism between wind and sand particles are significantly affected by turbulence characteristics of incoming flow under the actual terrain conditions. Therefore, it is necessary to simulate the impurity-free wind field under the actual terrain conditions before the windblown sand test in the wind tunnel. Unfortunately, in previous studies on Aeolian Physics, the influence of turbulence characteristics on the movement of windblown sand under actual terrain conditions had been neglected [34; 35; 39; 40], resulting in a deviation between the simulation results and the actual results.  
To further improve the reliability of windblown sand tests, we carefully consider the influence of turbulence characteristics of incoming flow on the sand transport in this study. The measured wind data are divided into sub-samples at a 10-min interval following Load Code for the Design of Building Structures (GB50009-2012) [47]. Thus, the measured impurity-free wind profile and turbulence intensity profile in desert regions are obtained, as shown in Figure 5.  
Figure 4: The observation site and the measuring system.  
Based on the measured results of sand collection in most previous studies [3; 30; 31] and the actual height of the existing infrastructures and civil structures in desert regions, the wind tunnel tests are designed to replicate the first 10 m of the surface layer. By comparing the measured height in desert regions with the size of the wind tunnel test section, the geometric scale ratio is chosen to be 1:10. It is difficult to consider the geometric scaling of sand particles because the particle size is less than 1 mm. Therefore, according to the existing windblown sand tests [33; 35; 40; 44; 45], we ignored the influence of the geometric scaling of sand particles on the results. The impurity-free wind flow field in the wind tunnel test is shown in Fig. 5.  
Figure 5: Wind tunnel simulation: (**a**) Wind profiles; (**b**) Turbulence intensities.  
desert regions is simulated by using artificial roughness with baffles, roughness elements and spires in the wind tunnel (Figure 1). For comparison, the wind profiles and longitudinal turbulence intensity profiles with the 10-min interval are also presented in Figure 5, and, respectively, specified by the Chinese, Japanese and European wind codes and standards in the terrain types of Class A, Class I and Class I [47; 48; 49]. The roughness lengths obtained by field measurement and wind tunnel test are 0.0095 m and 0.0086 m, and the shear velocities are 0.378 m/s and 0.373 m/s, respectively. As can be seen from Figure 5, the impurity-free wind profile and the longitudinal turbulence intensities simulated in the wind tunnel are consistent with field measurement results obtained by [PERSON] et al. [33]. There is a significant difference between the measured wind profile and the exponential law wind profiles adopted by Chinese and Japanese wind codes and standards. The log-law wind profile defined by European wind code is in good agreement with the measured wind profile in desert regions. The measured turbulence intensities are greater than the turbulence intensities of a similar field specified by the Chinese, Japanese and European wind codes and standards.