Partial validation of CFD blast simulation in a cityscape environment featuring structural failure

Abstract

We demonstrate the capabilities of computational fluid dynamics (CFD) and a pressure-impulse failure model to predict blast loading and structural damage in a geometrically complex cityscape. The simulated loading is compared against experimental results for 69 g PE4 in a 1/50th scale model with wood-framed and plywood-faced buildings; data were collected from 11 pressure gauges throughout. In the initial simulation, geometric features were modeled as perfectly rigid, whereas buildings in the experiment failed: the resulting differences between the model and experiment allowed us to evaluate CFD when failure occurs. Simulated peak pressures during the first positive phase were still within 20% of experiment at most pressure gauges. However, errors in first phase impulses were around 40%, suggesting that building-failure effects are greater toward the phase end. Then, to model building-failure effects, we attempted to fit pressure-impulse failure curves to the plywood-faces: this proved too simplistic to produce realistic blast wave behavior due to the various, complex failure modes. This work illustrates key limitations of available CFD software and the pressure-impulse failure model – both industry-standard tools to determine structural response to blast. We conclude that stronger coupling between blast loading and structural response is needed where significant failure occurs.