Comparing 2D and 3D Solar Radiation Modeling in Urban Areas

The use of solar radiation in the urban environment is becoming increasingly important for the sustainable development of cities and human societies. Several factors influence the distribution of solar radiation in urban areas, including urban morphology and the physical properties of urban materials. Most of these factors can be modeled with a relatively high accuracy using 2D and 3D solar radiation models. In this paper, the r.sun and v.sun solar radiation models are used to calculate solar radiation for the city of Košice in Eastern Slovakia to assess the accuracy of both approaches for vertical surfaces frequently found in urban areas. The results were validated by pyranometer measurements. The results showed relatively good estimates by the 3D v.sun model and poor estimates by the 2D r.sun model. This can be attributed to an improper representation of vertical surfaces by a digital surface model, which has a strong impact on solar resource assessments. We found that 3D city models prepared in level of detail 2 (LoD2) are not always adequate in case of complex buildings with morphological structures, such as terraces. These cast shadows on facades especially when solar altitude is high and, thus, assessments, even by a 3D model, are inaccurate.

Investigation on the Impact of Angle Dependency and Polarization on Radiation Heat Transfer

In the semiconductor industry there is an increasing demand for thermal stability to optimize the performance of lithography machines. This results in a need for computational tools that are able to accurately model radiation heat transfer, with the ability to include specular and angle dependent reflection and take the influence of the polarization into account. An analytical approximation model of a square passage is formulated, that includes angle dependent reflecting surfaces and the influence of polarization. These problems can be used as benchmarks to verify radiation modeling tools, e.g. COMSOL. The tool is validated by modeling an experiment and comparing the numerical results with the experimental data. The impact of angle dependency and polarization on the heat flux through passages is discussed.

Solar Extreme and Far Ultraviolet Radiation Modeling for Aeronomic Calculations

Modeling the upper atmosphere and ionospheres on the basis of a mathematical description of physical processes requires knowledge of ultraviolet radiation fluxes from the Sun as an integral part of the model. Aeronomic models of variations in the radiation flux in the region of extreme (EUV) and far (FUV) radiation, based mainly on the data of the last TIMED mission measurements of the solar spectrum, are proposed. The EUVT model describes variations in the 5–105 nm spectral region, which are responsible for the ionization of the main components of the earth’s atmosphere. The FUVT model describes the flux changes in the 115–242 nm region, which determines heating of the upper atmosphere and the dissociation of molecular oxygen. Both models use the intensity of the hydrogen Lyman-alpha line as an input parameter, which can currently be considered as one of the main indices of solar activity and can be measured with relatively simpler photometers. A comparison of the results of model calculations with observations shows that the model error does not exceed 1–2% for the FUVT model, and 5.5% for EUVT, which is sufficient for calculating the parameters of the ionosphere and thermosphere.

Application of the Multi-Spectral Correlated-k Distribution Model to Multi-Dimensional Rectangular Enclosure Gas Radiation Calculations

The Multi-Spectral Correlated-k distribution model (MSCk) is an amelioration of the widely used Ck model. In the MSCk model, the breakdown of correlation assumption used in the original Ck model for non-uniform media is overcome by introducing the clustering of scaling functions. The principle of MSCk model is to group together wavenumbers with respect to the spectral scaling functions—defined as the ratio between spectral absorption coefficients in distinct states—so that the correlation assumption can be considered as exact over the corresponding intervals of wavenumbers. Until now, validations of the MSCk model in 0D and 1D test cases have already been performed in the previous work (Andre, F., Hou, L., Roger, M. and Vaillon, R., 2014. The multispectral gas radiation modeling: A new theoretical framework based on a multidimensional approach to k-distribution methods. Journal of Quantitative Spectroscopy and Radiative Transfer, 147, pp.178–195; Andre, F., Hou, L. and Solovjov, V.P., 2016. An Exact Formulation of k-Distribution Methods in Non-Uniform Gaseous Media and its Approximate Treatment Within the Multi-Spectral Framework. Journal of Physics: Conference Series, 676(1)). However, its application to multi-dimensional configurations (much closer to industrial applications) has not been conducted. Accordingly, in the present paper, we focus our attention on the application of the MSCk model to Multi-dimensional calculations.