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Wind Tunnel Model Tests of Large Billboards

Two series of wind tunnel tests on 1: 200 scale models of large billboard structures were carried out in turbulent boundary layer flow. The tested configurations in the first series are single-panel rectangular billboards with width to depth ratio varying from 1 to 3 and depth to height ratio varying from ⅓ to ⅔, and in second series are two-panel billboards with the angle between two panels (ϕ) varying from 0° to 30°. The high-frequency force balance technique was employed. The test results show that the mean drag force coefficient CD of single-panel billboards attains its maximum value of about 1.3 to 1.5 when the wind attack angle θ lies between −45° and +45°. The maximum value of mean forces on two-panel billboards is slightly higher than that of the corresponding single-panel billboard. Wind-induced torsion about the vertical axis of single-panel billboards increases as θ increases, and attains its maximum value at θ of about ±45°. The maximum torsion can be estimated by multiplying the maximum drag force with the peak horizontal eccentricity of about 15% of the billboard width. For two-panel billboards, the eccentricity increases as ϕ increases, and reaches 24% at ϕ = 30°. The aerodynamic admittance function for all billboard configurations agrees reasonably well with the well-known Vickery's admittance formula.