The Laboratory Test Of Wind Speed Scale In Gravity Similarity System

The correspondence between model wind speed and model pressure distribution was explained based on wind tunnel model test. The correspondence between prototype wind speed and prototype pressure distribution was calculated based on the theory ("Code for Loads of Port Engineering" and "Rules for the classification and construction of offshore fixed platform" are the same. The accurate wind speed scale was obtained based on the basic principles of similitude theory consequently. This method can be applied to circumstances of arbitrary cylinder objects.A series of experiments with cylinders and square cylinders at different wind speed was done by the method above. The test gives the correction coefficient of cylinders and square cylinders' wind speed scale. Then the influences of the geometric scale, turbulence intensity, model dimension, the incidence angle of wind, the three-dimension character were discussed. Results are as follows.Considering the wind effect under the gravity similarity system, the wind speed scale should be corrected. The coupling effects of structure shape, turbulence intensity, geometric scale are especially discussed.The physical model test of cylinder and square cylinder can be taken without correction under the conditions that geometric scale is less than 30 and prototype wind speed is higher than 50m/s (cylinder) or higher than 40m/s(square cylinder). This article provides the experimental datas of correction coefficient for reference with different structure shape, turbulence intensity and geometric scale.The influence of three-dimensional effect on cylinder's correction coefficient is 10-15% in test zone. On the other side, the influence on square cylinder is less than 4%. The influence of incidence angle of wind on square cylinder's correction coefficient is concerned with wind speed when prototype wind speed is less than 30m/s. Correction coefficient is found to have maximum value when the incidence angle of wind at 10°, and orrection coefficient is found to have minimum value when the incidence angle of wind at 45° (the incidence angle of wind changes between 0°?45°).The test result shows that the influence of turbulent intensity on correction coefficient presented a fluctuation change when the turbulent intensity is between 7%?26%. The correction coefficient within a turbulent intensity of 13%?26% is more stable than that within a turbulent intensity of 7%?13%. We suggest to control the turbulent intensity in wind field larger than 13%.