Three-dimensional Numerical Simulation of the Protective Effect of Tall Building on Short Building

Abstract

Tall buildings distort the electric field of the surrounding environment, resulting in a relatively strong electric field at top corners, which affects the lightning strike process, and the protection effect that short buildings receive from tall buildings varies with the distance between them. A three-dimensional fine-resolution lightning attachment model with multiple upward leaders (LAMM) is used to simulate protection effect of a tall building and a short building with different height and distance, with an isolated building set as a control group. Experimental results show that when there is a tall building with a short building in the space and two buildings are close to each other, the distortion range of the tall building almost completely contains the distortion range of the short building, the development of downward leader is completely affected by the tall building, and the shielding effect of the tall building on the short building is significant. With the increase of the building distance, the shielding effect of the tall building on the short building decreases exponentially. When tall building is 250 m high and the short building is 150 m high, probabilities of lightning strikes on short building with distance from 50 m to 600 m with interval of 50 m are 8.3%, 15.0%, 26.5%, 36.7%, 39.5%, 47.5%, 58.9%, 57.0%, 56.0%, 57.2%, 61.0%, and 62.5%. When there is a cut-off point where the increasing trend of the probability of lightning strikes on short buildings appears to slow down significantly, the probability of lightning strikes on short building differs from its probability of lightning strikes in isolation by only 3.6%. Comparing the lightning strike results for different building distance and isolated building, the difference in lightning strike results caused by the presence of tall building decreases from 44.5% to 22.7% when the horizontal distance between tall and short buildings is increased from 400 m to 600 m. Given the height of tall building, the probability of lightning strikes on short building with different heights follows a similar trend from a large increase to a flat increase with an inflection point. Corresponding to short building height from 50 m to 200 m, the horizontal distances reaching cut-off point are 300, 450, 550 m and 600 m, respectively. When two buildings are far separated, the effect of tall building on the probability of lightning strikes on short building is weaker, and it can be assumed that there is a state when tall building have no effect on the lightning attachment process.

Keywords

• spatial morphology
• electric field distortion
• protective effect
• numerical simulation
• multiple upward leaders