Application of an Immersed Boundary Method to generate boundary layer turbulence and unsteady wind fields

Large-eddy simulations of wind engineering problems frequently rely on a combination of artificial turbulence generation and a rough wall function on the ground surface to generate a neutral surface layer flow. This approach may fall short when the aim is to capture non-standard wind conditions. Examples range from modeling the roughness sublayer for simulations of low-rise buildings to modeling profiles that deviate from the typical log-law shape or modeling unsteady events such as tornados. To address these challenges, this study explores the use of an Immersed Boundary Method (IBM) to simulate the interaction between the wind flow and a combination of roughness elements, spires, or louvers positioned in the flow development section of the computational domain. The implementation is tested on two set-ups: one with roughness elements that will generate a roughness sublayer for low rise building applications, and one with louvres that generate an unsteady velocity profile. In the first case, we quantitatively established the relationship between the velocity profile of the complete ABL inner layer and the distribution characteristics of roughness elements. At the same time, we achieved the simplification of the set-up of numerical analysis of a wide range of wind engineering flows without compromising on computational efficiency. In the second case, we compared with the results of wind tunnel experiments, demonstrating the feasibility and convenience of applying IBM in non-steady flow simulations.