# Wind Tunnel Test on Windblown Sand Two-Phase Flow Characteristics in Arid Desert Regions
## 4 Conclusions  
In this study, we attempt to absorb the theory from Aeolian Physics into the research of structural wind engineering to obtain the characteristics of windblown sand flow fields. The research results would provide the reference for the improvement of windblown sand test technologies and methods, and also provide the theoretical basis for wind erosion control, wear resistance, windblown sand mitigation, and windblown sand resistance design of infrastructures and civil structures in arid desert regions. Significant conclusions are summarized as follows:  
(1) Based on the measured wind characteristics in arid desert regions, windblown sand flow fields with three kinds of sand beds are simulated in the wind tunnel, respectively. The results indicate three kinds of sand particles in the flow field mainly move below 0.3 m. The characteristic saltation height of sand particles increases with increasing wind speed and particle size.  
(2) The sand concentration increases as the wind speed increases, and decreases exponentially as the height increases and the exponential function \(\rho_{s}=a\exp(-z/b)\) is applied. Coefficient \(1/b\) is the relative decay rate, which decreases with the increase in  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Particle Size** & **Wind Speed (m/s)** & \(\alpha\) & \(\beta\) & \(R^{2}\) \\ \hline \multirow{3}{*}{Coarse sand} & 14.74 & 0.44 & 11.39 & 0.94 \\  & 16.68 & 2.50 & 14.28 & 0.96 \\  & 18.61 & 4.39 & 10.94 & 0.99 \\ \hline \multirow{3}{*}{Fine sand} & 14.74 & 1.83 & 11.31 & 0.99 \\  & 16.68 & 3.90 & 9.30 & 0.99 \\  & 18.61 & 7.73 & 10.26 & 0.99 \\ \hline \multirow{3}{*}{Mixed sand} & 14.74 & 2.48 & 11.18 & 0.99 \\  & 16.68 & 5.02 & 9.09 & 0.99 \\ \cline{1-1}  & 18.61 & 9.43 & 8.78 & 0.99 \\ \hline \hline \end{tabular}  
Fitted function: \(P_{s}=\alpha\exp(-\beta z)\); \(R^{2}\) is the correlation coefficient at 0.05 significance level.  
\end{table}
Table 4: The correlation between the impact pressure of sand particles and height.  
Figure 15: The impact pressure: (**a**) At the indicated wind speed of 14.74 m/s; (**b**) At the indicated wind speed of 16.68 m/s; (**c**) At the indicated wind speed of 18.61 m/s.  
wind speed for all particle sizes. At the same wind speed, the concentration value is the largest for mixed sand, followed by fine sand, and the smallest for coarse sand.  
(3) Windblown sand flow field can be divided into the flow field inside and outside the sand particle saltation layer. Within the saltation layer, the particle movement significantly reduces wind speed and enhances turbulence intensity. The influence is directly related to the vertical distribution characteristics of sand concentration. Outside the saltation layer, the particle movement has little effect on wind profile and turbulence intensity.  
(4) The energy and impact pressure of particles increase with increasing wind speed, and decays with exponential function as the height increases. At the same wind speed, the energy and impact pressure in the mixed sand, fine sand, and coarse sand are successively reduced. The variation of kinetic energy with height is similar to that of total energy with height and the proportion of potential energy to total energy is quite small.  
Conceptualization, B.H. and Z.L.; methodology, B.H. and Z.L.; software, Z.Z. ([PERSON]); investigation, B.H., Z.L. and Z.Z. ([PERSON]); formal analysis, B.H. and B.G.; resources, B.G.; writing--original draft preparation, B.H.; writing--review and editing, B.H. and Z.Z. ([PERSON]); supervision, Z.L. and Z.Z. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
This research is supported by the Hainan Provincial Natural Science Foundation of China (No. 520 QN231), the National Natural Science Foundation of China (No. 52068019), the Hainan University Research Start-up Foundation (No. KYQD(ZR)20005) and the Hainan Major Science and Technology Project (No. ZDKJ201803), which are greatly acknowledged.  
Not applicable.  
The authors declare no conflict of interest.