Anisotropic radiation source models for computational thermal manikin simulations based on common radiation field measurements

The balanced design of extreme heat adaptation strategies that engineer the radiative properties of infrastructure or human clothing requires realistic methods of spectrally and spatially resolving irradiation from a complex built environment on the human body. Current irradiation measurement methods oversimplify the human body as points, spheres, or cylinders. In contrast, computational thermal manikins often used in convective simulations resolve the 3D body shape but have predominantly been used to model radiation exchange only with a large isothermal surrounding. To bridge this gap, we formulated six anisotropic radiation source models for thermal manikin simulations based on net-radiometer 6-directional, acrylic globe, and cylindrical radiation thermometer measurements. In some cases, we augmented the models with solar zenith angle and theoretical global solar irradiation. The models predict similar diffuse longwave (LW) as well as direct and diffuse shortwave (SW) radiation for measurements taken during a representative hot, sunny day with an unobstructed sky view. For three times of the day, we simulated irradiation distributions on an average male thermal manikin. Comparing the resulting irradiation maps showed that the direct SW component should be based on solar direction instead of the 6-directional "box" approach. Results also highlight the importance of the diffuse irradiation implementation method. However, experimental benchmarking (e.g., using physical thermal manikins in real-world settings) is required to determine whether the volumetric, box, or spherical diffuse source specification is the most realistic approach. The introduced techniques can be applied to realistically simulate irradiation from real-world built environments on a wide range of individuals.