Manuel J. García

FIXED GRID FINITE ELEMENT ANALYSIS FOR 3D STRUCTURAL PROBLEMS

Fixed Grid (FG) methodology was first introduced by Garcia and Steven as an engine for numerical estimation of two-dimensional elasticity problems. The advantages of using FG are simplicity and speed at a permissible level of accuracy. Two-dimensional FG has been proved effective in approximating the strain and stress field with low requirements of time and computational resources. Moreover, FG has been used as the analytical kernel for different structural optimization methods as Evolutionary Structural Optimization, Genetic Algorithms (GA), and Evolutionary Strategies. FG consists of dividing the bounding box of the topology of an object into a set of equally sized cubic elements. Elements are assessed to be inside (I), outside (O) or neither inside nor outside (NIO) of the object. Different material properties assigned to the inside and outside medium transform the problem into a multi-material elasticity problem. As a result of the subdivision NIO elements have non-continuous properties. They can be approximated in different ways which range from simple setting of NIO elements as O to complex non-continuous domain integration. If homogeneously averaged material properties are used to approximate the NIO element, the element stiffness matrix can be computed as a factor of a standard stiffness matrix thus reducing the computational cost of creating the global stiffness matrix. An additional advantage of FG is found when accomplishing re-analysis, since there is no need to recompute the whole stiffness matrix when the geometry changes. This article presents CAD to FG conversion and the stiffness matrix computation based on non-continuous elements. In addition inclusion/exclusion of O elements in the global stiffness matrix is studied. Preliminary results shown that non-continuous NIO elements improve the accuracy of the results with considerable savings in time. Numerical examples are presented to illustrate the possibilities of the method.

Low Altitude Wind Simulation over Mount Saint Helens Using NASA SRTM Digital Terrain Model

On February 11, 2000, the Shuttle Radar Topography Mission (SRTM) was launched into space as part of one of the pay load of the Shuttle Endeavor. Using a new radar sweeping technique most of the Earths surfaces was digitized in 3D in approximately 10 days. SRTM acquired enough data during its mission to obtain a near-global high-resolution database of the Earths topography. This paper describe how this revolutionary data set can be used to simulate anywhere around the Earth low altitude wind conditions for various atmospheric conditions. More specifically, we will describe the various processing steps necessary to convert this high-resolution terrain model provided by the SRTM database into a Computational Fluid Dynamic (CFD) volumetric mesh that is compatible with an open source CFD solver called OpenFOAM running in parallel on large West- Grid supercomputers. This work is the result of a new virtual wind-tunnel under development at the University of Alberta. In the paper, we present wind flow over the Mount- Saint Helens in the United States for a simple wind flow boundary condition.

Local quaternion weighted difference functions for orientation calibration on electromagnetic trackers

The accuracy of the electromagnetic tracking systems has been always an important issue with application to motion and kinematic analysis. Applications in virtual reality and gesture recognition require not only of improved accuracy but also fast error compensation. Several analytic methods have been used in order to correct the position error and they are well known and fast: polynomial fitting, calibration tables, and more recent, neural networks. We are interested in the orientation calibration of working spaces with possible high distortion conditions. Such conditions are prevalent in virtual environment spaces such as the CAVE and it is not always possible to avoid metallic components in the surroundings. In this paper, we introduce a calibration method for a multiple-sensor electromagnetic tracking system in an environment with highly electromagnetic distortional conditions. The target system is a twelve-sensor Ultratrak Polhemus Inc.trade system. We compare two possible formulations: global parameter estimation and local parameter estimation for the corrective functions. It is assumed that the inverse quaternion error Q-1isin exists and it is a function of the three-dimensional location: Q-1 isin rarr f(x,y,z)

Augmentation of Visualisation Using Sonification: A Case Study in Computational Fluid Dynamics

Advances in computer processing power and networking over the past few years have brought significant changes to the modeling and simulation of complex phenomena. Problems that formerly could only be tackled in batch mode, with their results being visualized afterwards, can now be monitored using graphical means while in progress. In certain cases, it is even possible to alter parameters of the computation while it is running, depending on what the scientist perceives in the current visual output. This ability to monitor and change parameters of the computational process at any time and from anywhere is called computational steering. Combining this capability with advanced multi-modal tools to explore the data produced by these systems are key to our approach. We present an advanced multi-modal interface where sonification and 3D visualization are used in a computational steering environment specialized to solve real-time Computational Fluid Dynamics (CFD) problems. More specifically, this paper describes and experimentally proves how sonification of CFD data can be used to augment 3D

A Dynamic Regulation Market Mechanism for improved financial settlements in wholesale electricity markets

This paper proposes a Dynamic Regulation Market Mechanism (DRMM) that results in improved financial settlements for wholesale electricity markets. The DRMM dispatches control signals at the Tertiary Control (TC) level based on a co-optimization problem that jointly optimizes energy production and reserve capacity. At the Secondary Control (SC) level the DRMM dispatches control signals using an iterative algorithm that effectively eliminates steady state error in the system frequency. In addition to the overall DRMM remaining stable, the conditions under which it leads to improved financial settlements are described. Using a three area example, where each area corresponds to a modified IEEE-300 bus system, the control performance and the financial settlements are compared to standard SC. It is shown that the frequency response is nearly identical and that the make-whole payments, a performance metric associated with financial settlements, are smaller with the proposed DRMM.

Multi-modal Interface for Fluid Dynamics Simulations Using 3---D Localized Sound

Multi-modal capabilities can be added to a simulation system in order to enhance data comprehension. We describe a system for adding sonification capabilities to a real-time computational fluid dynamics (CFD) simulator. Our system uses Max/MSP modules to add sonic properties to CFD solutions. The enhancements described in this paper allow users to locate sound sources in a 3---D environment using stereo auditory cues to identify data features.

ParaVoxel: A Domain Decomposition Based Fixed Grid Preprocessor

In this paper, a parallel cartesian fixed grid mesh generator for structural and fluid dynamics problems is presented. The method uses the boundary representation of a body and produces a set of equal sized cells which are classified in three different types according to its location with respect to the body. Cells are inside, outside or intersecting the boundary of the body. This classification is made by knowing the number of nodes of a cell that are inside body. That process is accomplished very efficiently as the nodes can be classified in batch. Once boundary cells are identified, its geometry is approximated by the convex hull of the nodes inside the body and the intersection points of the boundary against the cell edges. This paper presents the basics of the Fixed Grid Meshing algorithm, followed by some domain decomposition modifications and the data structures required for its parallel implementation. A set of examples and a brief discussion on the possibility of applying this algorithm together with other approaches is presented.

Modeling and Simulation of an Underwater Remotely Operated Vehicle (ROV) for Surveillance and Inspection of Port Facilities Using CFD Tools

Universidad Pontificia BolivarianaDepartment of Mechanical EngineeringP.O. Box 56006Medell´in, Colombiatelephone: 574-415-9020fax: 574-411-8779raul.valencia@upb.edu.coJuan A. Ram´irezUniversidad Pontificia BolivarianaDepartment of Mechanical EngineeringP.O. Box 56006Medell´in, Colombiatelephone: 574-415-9020fax: 574-411-8779juan.ramirez@upb.edu.coLuis B. Gutierrez´Universidad Pontificia BolivarianaDepartment of Electrical and Electronics EngineeringP.O. Box 56006Medell´in, Colombiatelephone: 574-415-9020fax: 574-411-8779luis.gutierrez@upb.edu.coManuel J. Garc´iaUniversidad EAFITDepartment of Mechanical EngineeringP.O. Box 3300Medell´in, Colombiatelephone: 574-261-9500fax: 574-266-4284mgarcia@eafit.edu.coABSTRACTThis article presents theoretical and computational stud-ies with Computational Fluids Dynamics (CFD) tools of anUnderwater Remotely Operated Vehicle (ROV), requiredto obtain reliable visual information, used for surveillanceand maintenance of ship shells and underwater structures ofColombian port facilities. The thrust force is analyzed at the op-erational conditions by using CFD tools (FLUENT

A comparative computational study of blood flow pattern in exemplary textile vascular grafts

Abstract Textile vascular grafts are biomedical devices and play an important role serving as a solution for the partial replacement of damaged arterial vessels. It is believed that the success of a textile vascular graft, in the healing process after implantation, is due to the porous micro-structure of the wall. Although the transport of fluids through textiles is of great technical interest in biomedical applications, little is known about predicting the micro-flow pattern and cellular transport through the wall. The aim of this work is to investigate how the type of fabric, permeability and porosity affect both the local fluid dynamics at several scales and the fluid-particle interaction between platelets in textile grafts, related with the graft occlusion. This study involves both experimental and computational tests. Experimental tests are performed to characterize the permeability and porosity according to the ISO 7198 standard. The numerical process is based on a multi-scale approach where the fluid flow is solved with the Finite Element Method and the discrete particles are solved with the Molecular Dynamic Method. The results have shown that the type of fabric in textile vascular grafts and the degree of porosity and permeability affect both the local fluid dynamics and the level of penetration of platelets through the wall, thus indicating their importance as design parameters.

Design, construction and testing of a data transmission system for a mid-power rocket model

This paper presents the continuation of a previous work in the development of a communication module for a solid propellant mid-power rocket model named “Simple-1” mission. It considered the design, construction, and testing procedures related to the data transmission protocol and its data rate. The current phase considers the antennas optimization, launching, and data analysis on-flight. In the actual optimization step, the antenna components were modified to increase the gain. A rocket model Estes Ventris Series Pro II® was used to carry in the payload section a communication module with several sensors in a CanSat form factor. The collected data was processed using an Arduino Mini micro-controller and transmitted using a radio module (Radiometrix) to a software defined radio (SDR) HackRF-based platform on the ground station. The printed circuit boards (PCBs) were designed and manufactured from commercial off the shelf (COTS) and assembled in a cylindrical rack structure similar to this small format satellite concept. The Simple-1 was tested with the help of a wind tunnel to validate the behavior of the antennas subsystem and was proved in several launches using solid propellant motors reaching altitudes from 500–700 meters. Different experimental data such as altitude, position, atmospheric pressure, and vehicle temperature were successfully captured and analyzed. This demonstrates that it is possible to develop low cost near space activities, gradually installing capabilities in a teamwork. In this developing stage, the techniques to design and manufacture two layers PCB were appropriated by traditional circuit board etching methods. In addition, the SDR technology was studied and implemented for the telemetry architecture. The use of surface mounting devices (SMD) offers an alternative to reduce the volume of the module. In the future, it is expected to have more advances in the stability of the communication protocols, robust hardware manufacturing, and integration of electronic circuits in four-layer PCB, in order to contribute to the access to space in our region and local aerospace industry developments.