Michael R. Myers

Heat Flux Determination From Ultrasonic Pulse Measurements

Ultrasonic time of flight measurements have been used to estimate the interior temperature of propulsion systems remotely. All that is needed is acoustic access to the boundary in question and a suitable model for the heat transfer along the path of the pulse train. The interior temperature is then deduced from a change in the time of flight and the temperature dependent velocity factor, which is obtained for various materials as a calibration step. Because the acoustic pulse samples the entire temperature distribution, inverse data reduction routines have been shown to provide stable and accurate estimates of the unknown temperature boundary. However, this technique is even more interesting when applied to unknown heat flux boundaries. Normally, the estimation of heat fluxes is even more susceptible to uncertainty in the measurement compared to temperature estimates. However, ultrasonic sensors can be treated as extremely high-speed calorimeters where the heat flux is directly proportional to the measured signal. Through some simple one-dimensional analyses, this work will show that heat flux is a more natural and stable quantity to estimate from ultrasonic time of flight. We have also introduced an approach for data reduction that makes use of a composite velocity factor, which is easier to measure.Copyright

A comparison of extended Kalman filter, ultrasound time-of-flight measurement models for heating source localization

Comparisons of six heating source localisation measurement models are conducted where temperature or ultrasonic time of flight readings provide the measurement update to the extended Kalman filter for estimating the location of a high heat flux spot source on a flat plate. For a particular measurement model, one of two processes are used: (1) directly using the measurements as the measurement vector in the extended Kalman filter or (2) indirectly obtaining the distance from the sensor to the heating source based on the measurement and then using the obtained distance as the measurement vector in the extended Kalman filter. For the direct models, the Jacobian required by the extended Kalman filter is obtained numerically using finite differences from the finite element forward conduction solution. For the indirect models, the derivatives of the distances with respect to the state variables are obtained in closed form. Heating source localisation results and convergence behaviour are compared for the six measurement models investigated. The ellipse from ultrasonic pulse one-way time of flight measurement model produces the best results when considering accuracy of converged solution, ability to converge to the correct solution given different initial guesses, and smoothness of convergence behaviour. Additionally, extended Kalman filter, extended information filter, and least squares inverse methods are compared for a parameter identification to quantify the heat flux and convection coefficient on the plate. All three inversion methods produce similar results which is significant as future work will consider only the extended Kalman filter.

Cyber-Physical Vehicle Modeling, Design, and Development

Vanderbilt University introduced a new course in the 2012 Fall Semester: Cyber-physical vehicle modeling, design and development. This course focused on the design, development, fabrication, verification, and validation of a scale vehicle in the virtual and the physical domains to meet a set of realistic and challenging design requirements for the Defense Advanced Research Projects Agency’s Model-Based Amphibious Racing Challenge. The students built a series of models in software and hardware to guide the design choices for the 1/5th scale amphibious vehicle. The culmination of this course was a competition against teams from other universities in January 2013 that compared the vehicle’s actual performance with student-created simulation models. This was an elective course outside the traditional capstone design curriculum and consisted of a team of juniors and seniors across the disciplines of mechanical engineering, electrical engineering, computer engineering, computer science, and physics. The students received robust training “to be an engineer” with many activities that can’t be included in a typical classroom environment: hands-on experience designing, modeling, and building a complete vehicle; simultaneously solving several open ended, rigid deadline challenges; and navigating complex team dynamics in a full end-to-end project. Additionally, the students gained experience using modern engineering modeling tools from the Defense Advanced Research Projects Agency’s META tool suite under development for the Fast, Adaptable, Next-Generation Ground Vehicle program. The META tool suite is a set of free, open source tools for compositional design synthesis at multiple levels of abstraction, design trade space exploration, metrics assessment, and probabilistic verification of system correctness. This work details the course activities and summarizes the lessons learned from a pedagogy perspective.Copyright

Using Ultrasound and the Extended Kalman Filter for Characterizing Aerothermodynamic Environments

Characterizing aerothermodynamic environments represents a significant challenge to aircraft operations. Hypersonic boundary-layer structure including transitions from laminar flow to turbulent flow is important to air vehicle design, thermal protection system design, and air vehicle in-flight control. Because the transition region cannot be observed directly, an inverse procedure must be formulated that relates transition region characteristics with parameters that can be measured. We propose a novel measurement system that leverages the hypersonic body-surface heating profile to locate the boundary-layer transition region. In this work, we focus on ultrasonic sensing as the measurement strategy, a three-dimensional conduction solution, and the extended Kalman filter for the inverse procedure. Development of the proposed measurement method is accomplished using simple, controlled experiments involving a high-heat flux step source on a large flat metal plate. Although the heating profile of the step sourc...

Heat Source Localization Sensitivity Analyses for an Ultrasonic Sensor Array

State estimation procedures using the extended Kalman filter are investigated for a transient heat transfer problem in which a heat source is applied on one side of a thin plate and ultrasonic pulse time of flight is measured between spatially separated transducers on the other side of the plate. This work is an integral part of an effort to develop a system capable of locating the boundary layer transition region on a hypersonic vehicle aeroshell. Results from thermal conduction experiments involving one-way ultrasonic pulse time of flight measurements are presented. Uncertainties in the experiments and sensitivity to heating source location are discussed. Comparisons of heating source localization measurement models are conducted where ultrasonic pulse time of flight readings provide the measurement update to the extended Kalman filter. Two different measurement models are compared: 1) directly using the one-way ultrasonic pulse time of flight as the measurement vector and 2) indirectly obtaining distance from the one-way ultrasonic pulse time of flight and then using these obtained distances as the measurement vector in the extended Kalman filter. For the direct model, the Jacobian required by the extended Kalman filter is obtained numerically using finite differences from the finite element forward conduction solution. For the indirect model, the derivatives of the distances with respect to the state variables are obtained in closed form. Heating source localization results and convergence behavior are compared for the two measurement models. Two areas of sensitivity analyses are presented: 1) heat source location relative to sensor array position, and 2) sensor noise. The direct measurement model produced the best results when considering accuracy of converged solution, ability to converge to the correct solution given different initial guesses, and smoothness of convergence behavior.Copyright

Collaborative Design in DARPA’s FANG I Challenge

The Defense Advanced Research Projects Agency (DARPA) created the Fast, Adaptable, Next-Generation Ground Vehicle (FANG) program to design and develop a new heavy, amphibious infantry fighting vehicle (IFV). DARPA, through the FANG program, is undertaking a radically novel approach to the design and manufacture of complex defense systems, and is hosting a series of prize-based design competitions. These are called the FANG Challenges, and their products will be progressively more complex vehicle subsystems, culminating in the design of a full IFV. They leverage the META design tools and the VehicleFORGE collaboration environment to significantly change the design experience and widen the aperture for design innovation. The META tool suite is a set of free, open source tools for compositional design synthesis at multiple levels of abstraction, design trade space exploration, metrics assessment, and probabilistic verification of system correctness. VehicleFORGE is an open source development collaboration environment for the creation of large, complex systems by numerous unaffiliated designers with the goal of democratizing the design innovation process by engaging several orders of magnitude more talent than the current industry model. This work summarizes the results from the first FANG challenge through analysis of participants, team structures, and the designs created.Copyright

A Novel Ultrasonic Method for Locating the Boundary Layer Transition Region on a Hypersonic Vehicle

Knowledge of where air owing across a body transitions from laminar ow to turbulent ow can provide numerous bene ts to air vehicle design, thermal protection system design, and air vehicle inight control. We propose a novel measurement system that leverages the hypersonic body-surface heating pro le to locate the boundary layer transition region. Ultrasonic sensing as the measurement strategy to detect localized changes in aeroshell temperature is suggested. For a localization system using ultrasonic transducers, the sensors would be located on the inside surface of the aeroshell away from the harsh external conditions. Consequently, the phenomenon that is being measured is not disturbed and the sensor is not exposed to deleterious environments. We hypothesize that incorporating state estimation to locate the transition region will require fewer sensors than otherwise possible. The proposed method involves a forward conduction solution and an inverse procedure based on the extended Kalman lter. Development of the proposed measurement method based on ultrasound and the extended Kalman lter is accomplished using simple, controlled experiments involving concentrated high heat ux sources on a large at metal plate. In this work, the proposed heating source localization method is detailed, results are presented from forward conduction solution development and at plate experimentation with a high heat ux point source, and extended Kalman lter convergence behavior is compared for heating source locations inside and outside a four-element ultrasonic transducer sensor array. The inverse procedure is able to converge to the correct heating source location if the heating source is located inside the sensor array but is unable to converge to the correct location if the heating source is located outside of the array. A key nding is the need to design a sensor array with numerous propagation paths and with paths near the heating source location.

Shrinkwrap geometry defeaturing for finite element analysis for a wheel and hub model

ABSTRACTThis manuscript presents an automated approach to accurately estimate structural performance for component assemblies using a shrinkwrap geometry defeaturing process for a wheel and hub model. Defeaturing is a popular geometry simplification technique that suppresses features within the geometry to decrease computational resources and time. Shrinkwrap defeaturing is an automated modeling technique that represents the exterior shape of the original full-featured geometry with a collection of surfaces for an abstract representation. The shrinkwrap defeaturing can be used on full-featured computer aided design components that are parts of an assembly but are not undergoing structural analysis and are included to transmit loads within the assembly. Of interest is the automated finite element structural analysis of the assembly. The proposed shrinkwrap approach is reviewed and assessed with a full-featured geometry model as well as other geometry defeaturing methods. A numerical example of a wheel and ...

A Challenge-based Unit with a Hands-on Demonstration for Teaching Momentum in Undergraduate Fluid Mechanics

Fluid momentum has proven to be one of the toughest concepts to grasp in fluid mechanics at Vanderbilt University and other institutions. Understanding the concept of fluid momentum is crucial to understanding and solving many real-world engineering problems. We developed, presented, and evaluated a fluid momentum unit in the Vanderbilt University undergraduate fluid mechanics course during the Fall 2011 semester. This particular course does not have a lab component, however we believe students can benefit from experiments and demonstrations in the classroom. Therefore, we included a hands-on demonstration component. We designed the fluid momentum unit using the Legacy Cycle developed by the Vanderbilt-Northwestern-Harvard/MIT Engineering Research Center (VaNTH ERC). The fluid momentum unit presented in this work achieved some success in helping students understand the concept of fluid momentum and the forces fluids exert on their surroundings. From a quantitative perspective, a statistical significance was not found when comparing the results from the students that received the subject fluid momentum unit and a control group of students that received a traditional lecture-formatted unit. Qualitatively, the subject group applied the conservation of momentum principle effectively in project and exam assessments. Additionally, the subject group student surveys indicated most of the students felt the fluid momentum unit presented in this work helped them learn better compared to traditional lecture units.