Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 25 for “"Low-order models"”.
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Low order models for hybrid gas bearings
A low order model was created to analyze a small scale gas bearing designed for the MIT microfabricated gas turbine engine. The journal has a diameter of 4.1 mm and is designed to spin at 2 million rpm. Due to microfabrication constraints, the bearing will have a very low length to diameter ratio …
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Experimental Study of Low-Order Models of Highly-Irregular Roughness and Their Impact on Turbulent Boundary Layers
… of the roughness to promote 'channeling' of the flow in the form of low- and high-momentum pathways as noted in contour maps of the mean velocity defect. Similarly, enhanced turbulent and vortical activity is observed both between and along the spanwise boundaries of these streamwise-elongated …
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Experimental study of low-order models of highly-irregular roughness and their impact on turbulent boundary layers
… layer under both developing- and developed-flow conditions. Low-order representations of highly irregular surface roughness replicated from a turbine-blade damaged by deposition of foreign materials were generated using singular value decomposition to decompose the complex topography into a …
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Analysis and reduction of a modeled bursting neuron
… of bursting in the model consisted of two slow variables traversing the state-space across a saddle-node bifurcation that defined an interface between quiescence and periodic spiking of the subsystem of fast variables. The parabolic nature of the burst was due to the homoclinicity of the …
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Real-time data assimilation in nonlinear dynamical systems
… Central to digital twins are physics-based low-order models and experimental data. On the one hand, low-order models are computationally cheap, but they may be quantitatively inaccurate and contain model errors. On the other hand, experimental data can be quantitatively accurate, but they …
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Impact of Total Temperature Probe of Geometry on Sensor Flow and Heat Transfer
… This work has led to the development of low-order models which can be used to calculate the performance of a total temperature probe as a first-order estimate. These low-order models require knowledge of the heat transfer to the total temperature sensor in order to calculate the probe …
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Physical domain model reduction for design and control of engineering systems
There is an increasing need for obtaining low order approximations of high order models of physical systems. Low order models result in several advantages including the reduction of computational complexity and improved understanding of the original system structure. Although different methods have …
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Use of Response Surface Metamodels in Damage Identification of Dynamic Structures
The need for low order models capable of performing damage identification has become apparent in many structural dynamics applications where structural health monitoring and damage prognosis programs are implemented. These programs require that damage identification routines have low computational …
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Closed-Loop Control of HCCI Engine Dynamics
… a potential to combine high efficiency with very low emissions. In order to fulfill the potential benefits, closed-loop control is needed. The thesis discusses sensors, feedback signals and actuators for closed-loop control of the HCCI combustion. Closed-loop control of the HCCI combustion using …
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Multi-channel blind system identification using the Laguerre expansion for characterization of circulatory hemodynamics
… new signal-processing algorithm generates two low order models that represent the distinct branch dynamic behavior associated with the measured circulatory signals. The framework for this methodology is based on a multi-channel blind system identification technique that has been reformulated to …
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Reduced-order, trajectory piecewise-linear models for nonlinear computational fluid dynamics
… the fluid dynamics community and yields accurate models for problems of interest. However, due to its high computational cost, CFD is limited for some applications. Therefore, model reduction has been used to derive low-order models that replicate CFD behavior over a restricted range of inputs, …
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An Experimental Conduction Error Calibration Procedure for Cooled Total Temperature Probes
… calibration procedure. The review of historical low-order models, as well as results from a developed thermal resistance model, indicates that conduction error is driven by dimensionless parameters, including the Biot, Nusselt, and Reynolds Numbers, as well as a non-dimensional temperature …
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Dynamics of swirling jets and flames
Even the simplest swirling jet flows possess an astonishing degree of complexity. This complexity is a two-edged sword, presenting both a unique opportunity to advance the science of fluid mechanics as well as a major barrier for a variety of engineering applications. In particular, swirling jet …
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Modelling and predictive control techniques for building heating systems
… of the system is often prohibitive. Models are required which can capture the thermodynamic properties of the building with sufficient accuracy for meaningful predictions to be made. Furthermore, a large number of tuning weights may need to be determined to achieve a desired …
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Theoretical and practical aspects of linear and nonlinear model order reduction techniques
Model order reduction methods have proved to be an important technique for accelerating time-domain simulation in a variety of computer-aided design tools. In this study we present several new techniques for model reduction of the large-scale linear and nonlinear systems. First, we present a method …
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Toward Efficient Bio-Inspired Propulsion: The Effect of Propulsor Shape and Kinematics on System Performance and Efficiency during Bio-inspired Locomotion
… difference from aspect ratio and area effects. Low order models were primarily used to conduct the bird flight study, though experimental methods were investigated as well. The thunniform swimming study was conducted through experimentation on a biomimetic system. The flight study found that, …
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Determination of Flame Dynamics for Unsteady Combustion Systems using Tunable Diode Laser Absorption Spectroscopy
… simulations of full-scale, turbulent, reacting flows remain unrealizable. The work in this paper is part of a study that focuses on developing compact models of TA instabilities, i.e. acoustics and flame dynamics. Flame dynamics are defined as the response in heat release to acoustic …
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Evaluation of uncertainty in dynamic, reduced-order power system models
… they remain time-consuming. Additionally, the models and parameters used in simulations are uncertain, due to measurement uncertainty, the need to approximate complex behavior with low-order models and the inherent changing nature of the power system. This thesis explores the use of model …
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Modelling and analysis of nonlinear thermoacoustic systems using frequency and time domain methods
In this thesis, low-order nonlinear models for the prediction of the nonlinear behaviour of thermoacoustic systems are developed. These models are based on thermoacoustic networks, in which linear acoustics is combined with a nonlinear heat release model. The acoustic networks considered in this …
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