Research

Jump to: Review

13 pages, 2535 KiB

Open AccessArticle

On Transformation Form-Invariance in Thermal Convection

by Gaole Dai and Jun Wang

Materials 2023, 16(1), 376; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16010376 - 30 Dec 2022

Cited by 1 | Viewed by 912

Over the past two decades, effective control of physical fields, such as light fields or acoustics fields, has greatly benefited from transforming media. One of these rapidly growing research areas is transformation thermotics, especially embodied in the thermal conductive and radiative modes. On [...] Read more.

Over the past two decades, effective control of physical fields, such as light fields or acoustics fields, has greatly benefited from transforming media. One of these rapidly growing research areas is transformation thermotics, especially embodied in the thermal conductive and radiative modes. On the other hand, transformation media in thermal convection has seldom been studied due to the complicated governing equations involving both fluid motion and heat transfer terms. The difficulty lies in the robustness of form invariance in the Navier–Stokes equations or their simplified forms under coordinate transformations, which determines whether the transformation operations can be executed on thermal convection to simultaneously regulate the flow and thermal fields. In this work, we show that thermal convection in two-dimensional Hele–Shaw cells keeps form-invariance, while its counterpart in general creeping flows or general laminar flows does not. This conclusion is numerically verified by checking the performances of invisible devices made of transformation media in convective environments. We further exploit multilayered structures constituted of isotropic homogeneous natural materials to realize the anisotropic inhomogeneous properties required for transformation media. Our results clarify the long-term confusion about the validation of the transformation method in thermal convection and provide a rigorous foundation and classical paradigm on inspiring various fascinating metadevices in both thermal and flow fields. Full article

(This article belongs to the Special Issue Thermal Metamaterials and Thermal Functional Devices)

► Show Figures

Figure 1

11 pages, 3781 KiB

Open AccessArticle

Nanoscale Thermal Cloaking in Silicon Film: A Molecular Dynamic Study

by Jian Zhang, Haochun Zhang, Wenbo Sun, Qi Wang and Dong Zhang

Materials 2022, 15(3), 935; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15030935 - 26 Jan 2022

Cited by 2 | Viewed by 1271

Abstract

Nanoscale thermal shielding is becoming increasingly important with the miniaturization of microelectronic devices. They have important uses in the field of thermal design to isolate electronic components. Several nanoscale thermal cloaks based on graphene and crystalline silicon films have been designed and experimentally [...] Read more.

Nanoscale thermal shielding is becoming increasingly important with the miniaturization of microelectronic devices. They have important uses in the field of thermal design to isolate electronic components. Several nanoscale thermal cloaks based on graphene and crystalline silicon films have been designed and experimentally verified. No study has been found that simultaneously treats the functional region of thermal cloak by amorphization and perforation methods. Therefore, in this paper, we construct a thermal cloak by the above methods, and the ratio of thermal cloaking and response temperature is used to explore its cloaking performance under constant and dynamic temperature boundary. We find that compared with the dynamic boundary, the cloaking effect produced under the constant boundary is more obvious. Under two temperature boundaries, the thermal cloak composed of amorphous and perforated has a better performance and has the least disturbance to the background temperature field. The phonon localization effect produced by the amorphous structure is more obvious than that of the perforated structure. The phonon localization of the functional region is the main reason for the cloaking phenomenon, and the stronger the phonon localization, the lower the thermal conductivity and the more obvious the cloaking effect. Our study extends the nanoscale thermal cloak construction method and facilitates the development of other nanoscale thermal functional devices. Full article

(This article belongs to the Special Issue Thermal Metamaterials and Thermal Functional Devices)

► Show Figures

Figure 1

Review

Jump to: Research

17 pages, 5915 KiB

Open AccessReview

Thermal Cloak: Theory, Experiment and Application

by Xiuli Yue, Junyi Nangong, Peiyan Chen and Tiancheng Han

Materials 2021, 14(24), 7835; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14247835 - 17 Dec 2021

Cited by 5 | Viewed by 2658

Abstract

In the past two decades, owing to the development of metamaterials and the theoretical tools of transformation optics and the scattering cancellation method, a plethora of unprecedented functional devices, especially invisibility cloaks, have been experimentally demonstrated in various fields, e.g., electromagnetics, acoustics, and [...] Read more.

In the past two decades, owing to the development of metamaterials and the theoretical tools of transformation optics and the scattering cancellation method, a plethora of unprecedented functional devices, especially invisibility cloaks, have been experimentally demonstrated in various fields, e.g., electromagnetics, acoustics, and thermodynamics. Since the first thermal cloak was theoretically reported in 2008 and experimentally demonstrated in 2012, great progress has been made in both theory and experiment. In this review, we report the recent advances in thermal cloaks, including the theoretical designs, experimental realizations, and potential applications. The three areas are classified according to the different mechanisms of heat transfer, namely, thermal conduction, thermal convection, and thermal radiation. We also provide an outlook toward the challenges and future directions in this fascinating area. Full article

(This article belongs to the Special Issue Thermal Metamaterials and Thermal Functional Devices)

► Show Figures