The numerical simulation of plate-type windborne debris flight

Kakimpa, Bruce (2012) The numerical simulation of plate-type windborne debris flight. PhD thesis, University of Nottingham.

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Abstract

Wind borne debris is one of the principal causes of building envelope failure during severe storms. It is often of interest in windstorm risk modelling to estimate the potential flight trajectories and impact energy of a piece of debris. This thesis presents research work aimed at the development and validation of a numerical model for the simulation of plate-type windborne debris. While a number of quasi-steady analytical models are available at present, these models are unable to account for the fluid-plate interaction in highly unstable flows. The analytical models are also limited to simple launch flow conditions and require extensive a-priori knowledge of the debris aerodynamic characteristics. In addition, the use of Euler angle parametrisations of orientation in the analytical models results in mathematical singularities when considering 3D six degree-of-freedom motion.

To address these limitations, a 3D Computational Fluid Dynamics (CFD) model is sequentially coupled with a quaternion based singularity-free six degree of freedom Rigid Body Dynamics (RBD) model in order to successfully simulate the flight of plate-type windborne debris. The CFD-RBD model is applied to the numerical investigation of the flow around static, forced rotating, autorotating and free-flying plates as well as the treatment of complex launch conditions.

Key insights into the phenomena of plate autorotation are highlighted including the genesis of the aerodynamic damping and acceleration torques that make autorotation possible. The CFD-RBD model is then validated against measurements of rotational speed and surface pressure obtained from recent autorotation experiments. Subsequently a general 3D spinning mode of autorotation is demonstrated and the CFD-RBD model is extended to include plate translation in order to simulate windborne debris flight.

Using the CFD-RBD flight model, a parametric study of windborne debris flight is carried out and four distinct flight modes have been identified and are discussed. The flight results are contrasted against available free-flight experiments as well as predictions from existing quasi-steady analytical models and an improved quasi-steady force model based on forced rotation results is proposed.

The resulting CFD-RBD model presents the most complete numerical approach to the simulation of plate-type windborne debris, directly simulating debris aerodynamics, and incorporates complex launch flow fields in the initial conditions.

Item Type:Thesis (PhD)
Supervisors:Hargreaves, D.
Owen, J.S.
Uncontrolled Keywords:CFD, Rigid Body Dynamics, CFD-RBD, Windborne Debris, Autorotation, Fluid-Rigid Body Interaction, free-flying plates
Faculties/Schools:UK Campuses > Faculty of Engineering > Department of Civil Engineering
ID Code:2376
Deposited By:Mr Bruce Kakimpa
Deposited On:27 Nov 2012 13:54
Last Modified:27 Nov 2012 13:54

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