Author(s): Paran Pourteimouri; Geert Campmans; Kathelijne Wijnberg; Suzanne Hulscher

Linked Author(s): Paran Pourteimouri

Keywords: Irflow around buildings; Aeolian sediment transport; Erosion and deposition patterns; Spacing between buildings at the beach; Computational fluid dynamics (CFD)

Abstract: Sandy beaches are very attractive to people worldwide. The attractiveness of sandy beaches increases the demands for the construction of buildings such as holiday cottages, restaurants, sailing clubs, recreational facilities and pavilions at the beach. These buildings alter the local airflow patterns in the surrounding area due to their dimension, geometry, elevation on pilings and positioning at the beach. This induces changes in the aeolian sediment transport, therefore erosion and deposition patterns around buildings at the beach. On a longer time-scale, these eroding and depositing areas influence the functioning of buildings at the beach, and might need additional measures in case this threatens the flood defense function of the dunes behind the beach. In the present study, the impact of spacing between adjacent buildings in a row on the erosion and deposition patterns in the surrounding area and downstream is studied as they are the supply towards the dunes. For this purpose, a computational fluid dynamics model using OpenFOAM is developed to simulate the airflow patterns around a row of ten full-scale buildings at the beach. The spacing between buildings is systematically changed between 0.5w to 4w, where w is the buildings’ width. The incident wind is perpendicular to the upwind faces of buildings in all simulations. The detailed simulated 2D field of near-bed shear stresses are then coupled to a process-based sediment transport model, AeoLiS, to calculate the aeolian sediment transport and morphologic changes around buildings. Numerical results are compared with field measurements around scaled buildings at De Zandmotor beach, the Netherlands. Results show that the flow barely intrudes into the gaps between buildings when the spacing between two adjacent buildings is 0.5w. Formation of two large counter-rotating vortices just behind the row of buildings, instead of two small vortices behind each building, indicate that a row of buildings close together act as one very wide building. This induces continuous sediment deposition upwind of the buildings, which is wrapped around the buildings and extends as two external deposition tails downwind the first and last buildings in the row. The length of the inner tails that form just downstream of the gaps between buildings increases when the spacing between two neighboring buildings reaches from 0.5w to w. The upwind depositions create a lunar shape and their peaks gradually become separate with increasing the spacing between buildings. Furthermore, the eroding regions occur very close to the upwind faces of buildings and the lateral sides in all simulations. The erosion and deposition patterns around buildings are fully independent and buildings act as isolated buildings when the spacing between two adjacent buildings increases to 4w.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022709

Year: 2022