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ABSTRACT
This paper studies the heat-shielding performance of a beetle forewing to explore how it has excellent thermal protective properties. With an experimental setup of a self-developed heating environment, the heat transfer characteristics of the beetle forewing were tested at 50°C under steady state conditions. Two types of the forewings are considered: cut wing and live wing. The heat transfer results show that the live forewing provides a good heat-shielding performance with the heat-shielding index stabilizing at around 22.1%, which is 60% higher than that of the cut wing. Based on scanning electron microscope images of the microstructure of the cross section of the beetle forewing, a simplified finite element analysis is performed to numerically calculate the heat transfer properties of the forewing. The numerical simulations reveal that the proposed structure of the forewing is good for the design of an effective thermal protection system. In addition, the uncertainty analysis is performed to evaluate the quality of experimental data. These results provide a foundational understanding of the heat transfer characteristics of beetle forewing, which will inspire a promising candidate for an actively cooled thermal protection systems.
Nomenclature
| a | = | thermal diffusion, m2.s−1 |
| cp | = | specific heat capacity, J.kg−1.K−1 |
| d | = | characteristic length, m |
| D | = | vertical length of flat plate, m |
| FE-SEM | = | field emission scanning electron microscopy |
| g | = | gravity constant, m.s−2 |
| hc | = | natural convective heat transfer coefficient, W.m−2.K−1 |
| h | = | forced convective heat transfer coefficient, W.m−2.K−1 |
| k | = | thermal conductivity, W.m−1.K−1 |
| L | = | vertical length of specimen, m |
| lu | = | upper lamination thick, µm |
| lv | = | trabecula height, µm |
| ld | = | lower lamination thick, µm |
| Nu | = | Nusselt number |
| Pr | = | Prandtl number |
| Q | = | measured quantity |
| q | = | heat flux, W.m−2 |
| r | = | radius of thermocouple wire, mm |
| Ra | = | Rayleigh number |
| Re | = | Reynolds number |
| T | = | temperature, °C |
| t | = | thickness of forewing, µm |
| ΔT | = | temperature difference, °C |
| TGA | = | thermogravimetric analysis |
| TPS | = | thermal protection system |
| V | = | flow velocity of fluid, m.s−1 |
| w | = | measured parameter |
| x | = | Cartesian coordinate |
| y | = | thermocouple position, mm |
| y0 | = | measured position of thermocouple, mm |
| z | = | measured parameter |
Greek symbols
| β | = | volumetric expansion coefficient, 1/K |
| δ | = | uncertainty |
| µ | = | dynamic viscosity, n.s.m−2 |
| ν | = | kinematic viscosity, m2.s−1 |
| ρ | = | density, kg.m−3 |
| τ | = | time, second |
| Ψ | = | heat–shielding index, % |
Subscripts
| b | = | back side |
| c | = | convection |
| d | = | characteristic length, m |
| D | = | vertical length of flat plate, m |
| e | = | ambient environment |
| f | = | front side |
| L | = | vertical length of specimen, m |
| s | = | back surface |
Additional information
Funding
Notes on contributors
Vinh Tung Le
Vinh Tung Le is a Ph.D. student at Konkuk University, Seoul, Korea. He received his B.S. in Aeronautics from Department of Aerospace Engineering of Ho Chi Minh City University of Technology, Vietnam in 2013, and M.S. in the Department of Advanced Technology Fusion, Konkuk University, South Korea in 2015. His research interests are thermal protection systems and high temperature structures.
Ngoc San Ha
Ngoc San Ha graduated from department of Aeronautical Engineering of Ho Chi Minh City University of Technology, Vietnam in 2008, and received his Ph.D. degree from the Department of Advanced Technology Fusion, Konkuk University, Korea in 2014. Currently, he is a postdoctoral research fellow at the Faculty of Science, Engineering and Technology, Swinburne University of Technology, Australia. His topics of interest primarily focus on bio-inspired structures, structural dynamics, impact mechanics, and digital image correlation application.
Nam Seo Goo
Nam Seo Goo is a Professor in the Department of Advanced Technology Fusion at Konkuk University, Seoul, Korea. He graduated from the Department of Aeronautics Engineering of Seoul National University with honors in 1990, and earned M.S. and Ph.D. degrees in Aerospace Engineering at the same university in 1992 and 1996, respectively. His Ph.D. was on the structural dynamics of aerospace systems. His current research interests are structural dynamics of small systems, smart structures and materials, high temperature structures and materials, and opto-mechanics.