Recent advancements in material technology have led to the development of non-porous negative Poisson's ratio (NPR) materials (also called auxetic structures) by making spherical inline dimples on both sides of an elastic sheet. Manufacturing technologies such as 3-D printing and additive manufacturing paved the way to realize the complex shapes needed to achieve NPR behavior. These materials are desirable in many engineering applications, especially in the gas turbines hot-gas-path, due to their unique properties. In the current study, an effort is made to understand the flow physics and surface heat transfer mechanism for channel flow having one wall with spherical dimples and protrusions. An equivalent geometry, with dimples on both sides of the flat sheet with density beyond a certain threshold, would have NPR characteristics. Furthermore, dimples and protrusions are also studied in isolation to understand what key differences are brought by the combination of these two. Flow field measurements, in-and-around these features, are done using the stereoscopic PIV. The transient TLC method is used for local surface heat transfer measurement. Numerical simulations, steady RANS, URANS, and LES, are used in conjunction with experimental data to develop a detailed understanding of the flow field and surface heat transfer. A comparison of experimental measurements and numerical simulations identifies the areas for improvement in numerical modeling of the flow field and surface heat transfer in the presence of such geometries. The friction factor measurement along with heat transfer is used to characterize the thermal performance factor (TPF) of each geometry for a range of Reynolds number. The novelty of this work is the inline arrangement of features and first-of-its-kind PIV measurement for dimples-protrusions. The understanding developed from this work can easily be utilized for designing components involving NPR materials with dimples-protrusions.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Gupta, Gaurav, "Detailed Study of Flow and Surface Heat Transfer Enhancement Mechanism in the Presence of Dimples and/or Protrusions" (2020). Electronic Theses and Dissertations, 2020-. 224.