Skip navigation
Please use this identifier to cite or link to this item:
Title: Investigations of the Fundamentals of Passive Scalar Dynamics using Nano-sensing devices
Authors: Arwatz, Gilad
Advisors: Hultmark, Marcus N
Smits, Alexander J
Contributors: Mechanical and Aerospace Engineering Department
Keywords: Fluid modeling
Heat Transfer
Nano sensors
Subjects: Mechanical engineering
Aerospace engineering
Issue Date: 2015
Publisher: Princeton, NJ : Princeton University
Abstract: Turbulence has been the core of numerous investigations over several decades. Among the wide spectrum of turbulence aspects, we focus on temperature as passive scalar advected in a turbulent velocity field. In this study, fundamental flow quantities are revisited by investigating statistically homogeneous and isotropic turbulence, with an imposed mean cross-stream linear temperature gradient. This is made possible by developing a new fast response nano-sensor to minimize measurement errors inherent in conventional temperature probes (cold wires). It is observed that cold wire attenuation has widespread effects on most aspects of themeasurements, resulting in the variance and the scalar rate of dissipation being significantly underestimated. Newly acquired data allow for a theoretical study of the temperature spectra, the dissipation range, different scaling laws and intermittencies. By studying the evolution equations of the temperature spectra, conditions for self-preserving solutions are derived and experimentally validated. Self-similarity of the dissipation subrange is explored,which reveals that the temperature field can be independently resolvedwithout knowledge of the velocity field. The results raise interesting questions about the underlying behavior of the scalar field, namely local equilibrium versus non-equilibrium. Based on the proposed scaling and the significant departure of existing models from the expected power-law behavior in the inertial range, a model spectrum is developed based entirely on temperature-related variables, showing a convincing agreement with the experimental data in the dissipation range. The underlying cause of scalar intermittencies, a well-established phenomenon reflected in the exponential tails of the scalar PDF, is yet to be determined. The interplay between advection and diffusion is investigated through their timescales ratio, following the linear eddymodel of Kerstein. The analysis reveals a widening iii of the PDF as more of the low frequency content is excluded. The development of the new sensor, along with the fundamental study, inspires new ideas for measuring conductivity as a way to assess humidity in the atmospheric boundary layer or blood damage due to shear stresses. Overall, the study sheds light on the importance of accurate and optimized measurement techniques in the pursuit of understanding turbulence.
Alternate format: The Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the library's main catalog
Type of Material: Academic dissertations (Ph.D.)
Language: en
Appears in Collections:Mechanical and Aerospace Engineering

Files in This Item:
File Description SizeFormat 
Arwatz_princeton_0181D_11294.pdf12.8 MBAdobe PDFView/Download

Items in Dataspace are protected by copyright, with all rights reserved, unless otherwise indicated.