Kevin Erhart

An evolutionary‐based inverse approach for the identification of non‐linear heat generation rates in living tissues using a localized meshless method

Purpose – This paper aims to develop and describe an improved process for determining the rate of heat generation in living tissue.Design/methodology/approach – Previous work by the authors on solving the bioheat equation has been updated to include a new localized meshless method which will create a more robust and computationally efficient technique. Inclusion of this technique will allow for the solution of more complex and realistic geometries, which are typical of living tissue. Additionally, the unknown heat generation rates are found through genetic algorithm optimization.Findings – The localized technique showed superior accuracy and significant savings in memory and processor time. The computational efficiency of the newly proposed meshless solver allows the optimization process to be carried to a higher level, leading to more accurate solutions for the inverse technique. Several example cases are presented to demonstrate these conclusions.Research limitations/implications – This work includes on...

An RBF Interpolated Generalized Finite Difference Meshless Method for Compressible Turbulent Flows

Computational Fluid Dynamics (CFD) is a topic that has been researched heavily over the past 50 years, especially since the accessibility to sufficient computational resources has greatly increased. However, it is precisely this increase in technology that has led to a lack of efficiency in many CFD developments, especially when it comes to the process of grid generation. While many researchers are currently focused on solutions to the grid generation problems of traditional CFD techniques, the majority of these approaches still suffer serious numerical difficulties due to the underlying CFD solution algorithms that are used. Therefore, the focus of this work is to demonstrate a novel approach to true CFD automation which is based on traditional Cartesian grid generation coupled with a Meshless flow solution algorithm. As Meshless method solutions require only an underlying nodal distribution, this approach works well even for complex flow geometries. And with the addition of a so-called shadow layer of body-fitted nodes, the stair-casing issues of typical Cartesian solvers are eliminated. This paper will describe the approach taken to automatically generate the Meshless nodal distribution, along with the details of an automatic local refinement process. Also, as the primary interest of automated CFD is for aerospace applications, this work includes the development of standard two-equation turbulence models for use in this Meshless based solver. Finally, results will be shown for the application of high-speed, compressible turbulent flows.Copyright

A Parallel Domain Decomposition Boundary Element Method Technique for Large-Scale Transient Heat Conduction Problems

In this paper, we develop a parallel domain decomposition Laplace transform BEM algorithm for the solution of transient heat conduction problems. The original domain is decomposed into a number of sub-domains, a procedure is described to provide a good initial guess for the domain interface temperatures, and an iteration is carried out to satisfy continuity of temperature and heat flux at the domain interfaces. The decomposition procedure significantly reduces the size of any single problem to be tackled by the BEM, significantly reduces the overall storage and computational burden, and renders the application of the BEM to modeling large transient conduction problem feasible on modest computational platforms. The procedure is readily implemented in parallel and applicable to 3D problems. Moreover, as the approach described herein readily allows adaptation and integration of traditional BEM codes, it is expected that the domain decomposition approach coupled to parallel implementation should prove very competitive to alternatives proposed in the literature such as fast multipole acceleration methods that require a complete re-write of traditional BEM codes.Copyright

Direct Compensator Profile Optimization for Intensity Modulated Radiation Therapy Treatment Planning

Radiation therapy is a widely used and highly effective technique for the treatment of cancer, however the commissioning and delivery of a course of external beam radiation is a complex process with numerous challenges. This paper will present new developments that aim to improve both the planning and delivery of this important cancer treatment technique. Specifically, this work develops a new direct delivery parameter optimization approach for planning of solid compensator intensity modulated radiation therapy, coined Direct Compensator Profile Optimization (DCPO). In order to understand the benefits and implications of this new DCPO approach, a reasonable understanding of the field of radiation therapy is needed. Therefore, this document will include a brief discussion of the history and relevant background information in the area of radiation therapy. It is intended that this background information is detailed enough so that the remainder of this research can be followed by those without existing experience in the field of radiation treatment planning. The specific details of this new approach will be then be presented followed by a display of initial results to verify the performance.Copyright