Two hills flow differently than one
Two hills flow differently than one lead image
The effect of different terrains on atmospheric flow is relevant to wind energy utilization, pollutant transportation, wildfire spread, and other applications. Although many works have explored turbulent flow over one hill, researchers do not yet understand flow over more complex terrain.
Through large eddy simulation, Sun and Zheng investigated flow dynamics and turbulent fluctuations of atmospheric boundary flow over two hills. They compared the pressure velocity, vortices, and turbulent kinetic energy of the flow over one hill versus the flow over two hills.
In the presence of the second hill, the pressure and velocity near the first hill are almost the same as when there is only one hill. However, the second hill does affect various characteristics of the flow. It leads to a larger low-pressure region over both hills and enhances the recirculated flow in the valley between them. The second hill decreases the streamwise velocity before it. After the second hill, recirculation weakens, the reattachment point of the flow moves closer to the foot of the hill, turbulent kinetic energy decreases, and turbulent fluctuation near the surface increases.
“This work is relevant to various atmospheric flow applications and can provide information for wind energy utilization, such as when a wind turbine is installed in the mountains,” said author Yujia Sun. “The findings of this work may also serve as a basis for understanding interactions between wind, fire, and mountains.”
This work is a step toward the authors’ ultimate goal of studying how wildfire spreads across two hills. Next, they will incorporate chemical reaction and fuel consumption information in their assessment of the flow.
Source: “Large eddy simulation of atmospheric boundary flow over two two-dimensional hills,” by Yujia Sun and Shu Zheng, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0154416 .
