Wind Proofing LIGO*

To reduce problematic wind that contributes to ground tilt, LIGO has proposed building a 50% porous fence around End Station X. We employed experimental and computational methods to evaluate the proposed fence. First, we tested different fence materials with a fan and a wind tunnel. Both materials reduced wind speed by about 50%, so the main differences will arise from cost and material strength. Next, we employed Computational Fluid Dynamics (CFD) modeling to evaluate the wind load on End Station X with and without a porous fence. We found that the fence is quite effective in reducing the load on the building. Models show that with a fence, problematic wind speeds could be above 20 m/s, which only occur 1.54% of the time. We then gathered data from the test fence at LIGO Hanford and compared it to steady-state and transient CFD models. We found that the steady state models are in good agreement with the measurements. However, the transient model shows variability than the real data, suggesting that the fence may smooth wind flow. A 50% porous fence is a well motivated wind proofing measure for End Station X, yet more robust model verification should be completed.