Three-dimensional reynolds number effects and wind load models for cylindrical storage tanks with low aspect ratios

Abstract

The wind loads of cylindrical storage tanks may be significantly affected by the Reynolds number (Re), while it is different from the infinite-length cylinder because the aspect ratios (H/D) of storage tanks are usually very low. The flow around tanks changes along the spanwise direction and presents a three-dimensional characteristic. In this study, the wind pressure on cylindrical storage tanks with 4 aspect ratios (H/D = 0.2–1.5) are measured by wind tunnel tests. Two kinds of flow field, uniform and atmospheric boundary layer (ABL) flow are set in the test with Re varying from 105 to 106. The drag and lift coefficients, wind pressure distributions and power spectra are analyzed to reveal the three-dimensional characteristics of the aerodynamic loads. Consequently, as the H/D of cylinder decreases, the Reynolds number effects are attenuated or even disappear gradually. The transition of separation occurs at Re in the range of 2.2 × 105–3.0 × 105 and 1.8 × 105–2.6 × 105 for tanks with H/D = 1.5 and 1.0 respectively, which is lower than that of two-dimensional cylinders. Moreover, the circumferential wind pressure distributions near the free end enter the critical Reynolds number region at lower Re than that at the middle sections. Parameters like the minimum pressure coefficient and separation angle are not exactly the same at different heights. Finally, a three-dimensional mean wind pressure distribution model of the storage tanks in the post-critical Re-independent region is proposed, the wind loads computed from which are accurate enough with only about 5% relative error to be used for design reference.