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ABSTRACT
Heating is the main biological effect of the electromagnetic (EM) fields to human eye. This study intends to focus attention on the differences in the heat transfer characteristics of the human eye induced by EM fields in different body positions. The effect of three different body positions – sitting, supine, and prone – on natural convection of aqueous humor (AH) in the anterior chamber of the eye is systematically investigated. The specific absorption rate (SAR) value, fluid flow, and the temperature distribution in the eye during exposure to EM fields are obtained by numerical simulation of EM wave propagation. In this study, the frequencies of 900 and 1,800 MHz are chosen for the investigations. The heat transfer model used in this study is developed based on natural convection and porous media theories. The results show that the AH temperature inside the anterior chamber is the highest in the supine position at both frequencies. It is found that during exposure to EM fields, body position plays an important role on AH natural convection and the heat transfer process within the anterior chamber and its periphery in the front part of the eye. However, the body position has no significant effect on temperature distribution for the middle part of the eye. The obtained results provide information on the body position and thermal effects from EM fields exposure.
Nomenclature
| C | = | specific heat capacity (J/(kg K)) |
| E | = | electric field intensity (V/m) |
| e | = | tear evaporation heat loss (W/m2) |
| f | = | frequency of incident wave (Hz) |
| H | = | magnetic field (A/m) |
| h | = | convection coefficient (W/m2 · K) |
| j | = | current density (A/m2) |
| k | = | thermal conductivity (W/(m K)) |
| n | = | normal vector |
| p | = | pressure (N/m2) |
| Q | = | heat source (W/m3) |
| T | = | temperature (K) |
| u | = | velocity (m/s) |
| t | = | time |
| B | = | volume expansion coefficient (1/K) |
| μ | = | magnetic permeability (H/m) |
| ϵ | = | permittivity (F/m) |
| σ | = | electric conductivity (S/m) |
| ω | = | angular frequency (rad/s) |
| ρ | = | density (kg/m3) |
| ωb | = | blood perfusion rate (1/s) |
| Γ | = | external surface area |
| Subscripts | = | |
| am | = | ambient |
| b | = | blood |
| ext | = | external |
| i | = | subdomain |
| met | = | metabolic |
| r | = | relative |
| ref | = | reference |
| 0 | = | free space, initial condition |
Nomenclature
| C | = | specific heat capacity (J/(kg K)) |
| E | = | electric field intensity (V/m) |
| e | = | tear evaporation heat loss (W/m2) |
| f | = | frequency of incident wave (Hz) |
| H | = | magnetic field (A/m) |
| h | = | convection coefficient (W/m2 · K) |
| j | = | current density (A/m2) |
| k | = | thermal conductivity (W/(m K)) |
| n | = | normal vector |
| p | = | pressure (N/m2) |
| Q | = | heat source (W/m3) |
| T | = | temperature (K) |
| u | = | velocity (m/s) |
| t | = | time |
| B | = | volume expansion coefficient (1/K) |
| μ | = | magnetic permeability (H/m) |
| ϵ | = | permittivity (F/m) |
| σ | = | electric conductivity (S/m) |
| ω | = | angular frequency (rad/s) |
| ρ | = | density (kg/m3) |
| ωb | = | blood perfusion rate (1/s) |
| Γ | = | external surface area |
| Subscripts | = | |
| am | = | ambient |
| b | = | blood |
| ext | = | external |
| i | = | subdomain |
| met | = | metabolic |
| r | = | relative |
| ref | = | reference |
| 0 | = | free space, initial condition |