Characterization and Simulation of a Bush Plane Tire

This paper deals with a Bush plane tire rolling in critical and extreme conditions as shocks and rebounds. The approach adopted is based on previous works on the modelling of Jumbo-Jet tires. A numerical finite element model is used in the simulation of the tire. Firstly, an experimental part is dedicated to study the inner features of the tire. The tire geometry and the materials within it are described. Secondly, a 2D embedded mesh model is developed based on the tire cross-section. Then a 3D model is generated and a runway with rocks and ramps is modelled. The tire behavior while rolling over obstacles is investigated. The simulation results, such as tire deformation, are analyzed. The results show significant deformation of the tire while rolling over ramps and a low lateral stiffness, giving it a significant capacity to absorb shocks. The numerical simulation was developed in order to predict the tire behavior during landing, especially in critical and extreme conditions. Cornering simulations were realized to evaluate the self-aligning moment. The numerical simulation is an efficient tool to estimate the forces transferred to the rim axis in critical and extreme conditions.

Control-Oriented Modeling of the Dynamics of Stirling Engine Regenerators

We develop a first-principles model of the regenerator component of a generic Stirling engine. The model is based on the Euler equations of one-dimensional gas dynamics coupled with its convective/conductive heat transfer with the embedded mesh material. We investigate various methods for deriving simpler and low-order control-oriented models from this first principles model, the basic criterion being high fidelity representation of the dynamics of the regenerator when coupled to other dynamic components of the engine. We identify several nondimensional parameters that potentially categorize different modes of operation, and investigate the corresponding time-scale separation. A hierarchy of singularly perturbed models is derived in which acoustic dynamics are eliminated, periodic mesh dynamics are averaged, and the shape of the distributed regenerator gas state is approximated. In addition, since the reduced model is to be operated cyclically when connected to other parts of the engine, we develop such a feedback-aware model reduction algorithm based on a proper orthogonal decomposition (POD) with a chirped signal input (chirp-POD). This algorithm yields reduced models that are accurate over a range of engine operating frequencies.

Computational Performance of an Embedded Reinforcement Mesh Generation Method for Large-Scale RC Simulations

In this paper, a numerical investigation on the limits of an automatic procedure for the generation of embedded steel reinforcement inside hexahedral finite elements (FEs) is presented. In 3D detailed reinforced concrete simulations, mapping the reinforcement grid inside the concrete hexahedral FEs is performed using the end-point coordinates of the rebar reinforcement macro-elements. This procedure is computationally demanding while in cases of large-scale models, the required computational time for the reinforcement mesh generation is excessive. This research work scopes to study and present the limitations of the embedded mesh generation method that was proposed by Markou and Papadrakakis, through the use of a 64-bit operating system. The embedded mesh generation method is integrated with a filtering algorithm in order to allocate and discard relatively short embedded rebar elements that result from the arbitrary positioning of the embedded rebar macro-elements and the nonprismatic geometry of the hexahedral mesh. The computational robustness and efficiency of the integrated embedded mesh generation method are demonstrated through the analysis of three numerical models. The first two numerical models are a full-scale 2-story and a 7-story RC structures while the third model deals with a full-scale RC bridge with a trapezoidal section and a total span of 100 m. Through the third numerical implementation, the computational capacity of the integrated embedded rebar mesh generation method is investigated.