Evaluation of the flow field imparted by a marine vehicle reveals the underlying efficiency and performance. However, the relationship between precise design features and their impact on the flow field is not well characterized. The goal of this work is first, to investigate the thermally-stratified near field of a self-propelled marine vehicle to identify the significance of propulsion and hull-form design decisions, and second, to develop a functional mapping between an arbitrary vehicle design and its associated flow field to accelerate the design analysis process. The unsteady Reynolds-Averaged Navier-Stokes equations are solved to compute near-field wake profiles, showing good agreement to experimental data and providing a balance between simulation fidelity and numerical cost, given the database of cases considered. Machine learning through convolutional networks is employed to discover the relationship between vehicle geometries and their associated flow fields with two distinct deep-learning networks. The first network directly maps explicitly-specified geometric design parameters to their corresponding flow fields. The second network considers the vehicle geometries themselves as tensors of geometric volume fractions to implicitly-learn the underlying parameter space. Once trained, both networks effectively generate realistic flow fields, accelerating the design analysis from a process that takes days to one that takes a fraction of a second. The implicit-parameter network successfully learns the underlying parameter space for geometries within the scope of the training data, showing comparable performance to the explicit-parameter network. With additions to the size and variability of the training database, this network has the potential to abstractly generalize the design space for arbitrary geometric inputs, even those beyond the scope of the training data. / Doctor of Philosophy / Evaluation of the flow field of a marine vehicle reveals the underlying performance, however, the exact relationship between design features and their impact on the flow field is not well established. The goal of this work is first, to investigate the flow surrounding a self–propelled marine vehicle to identify the significance of various design decisions, and second, to develop a functional relationship between an arbitrary vehicle design and its flow field, thereby accelerating the design analysis process. Near–field wake profiles are computed through simulation, showing good agreement to experimental data. Machine learning is employed to discover the relationship between vehicle geometries and their associated flow fields with two distinct approaches. The first approach directly maps explicitly–specified geometric design parameters to their corresponding flow fields. The second approach considers the vehicle geometries themselves to implicitly–learn the underlying relationships. Once trained, both approaches generate a realistic flow field corresponding to a user–provided vehicle geometry, accelerating the design analysis from a multi–day process to one that takes a fraction of a second. The implicit–parameter approach successfully learns from the underlying geometric features, showing comparable performance to the explicit–parameter approach. With a larger and more–diverse training database, this network has the potential to abstractly learn the design space relationships for arbitrary marine vehicle geometries, even those beyond the scope of the training database.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/89341 |
| Date | 02 May 2019 |
| Creators | Jones, Matthew Cecil |
| Contributors | Aerospace and Ocean Engineering, Paterson, Eric G., Devenport, William J., Pitt, Jonathan, Roy, Christopher J. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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