Investigation of the effect of a thermal island in Kharkiv

Abstract

Problem. One of the main problems that attracts the attention of researchers is a change in the urban microclimate, which is commonly referred to as the «effect of the urban heat island». Such an effect has already been investigated in many cities, but for cities in post-Soviet countries they have not yet been conducted. Goal. The goal of this work is to detect the effect of the heat island in Kharkiv and its research. Methodology. A mathematical modeling was carried out to evaluate design decisions aimed at improving the heat island's appearance in the city, including simulation of air flow, heat transfer and radiation equation. The flow of buildings and constructions within the city with allowance for heat transfer is characterized by unsteadiness, energy non-equilibrium, and large-scale diffusion, which is conditioned by the presence of large coherent structures. The calculation is made on the basis of solving the non-stationary Reynolds-averaged Navier–Stokes equations. Results. The picture of changes in the temperature of air at different times during the day is obtained. The confirmation of the presence of the effect of the "heat island" in Kharkiv, with a temperature increase of 2-4 , in comparison with the rural, has been obtained. The influence of roughness on the patterns of the flow in the field of urban development is analyzed. The roughness was given by the value of m. There are changes in temperature near the surface of the earth and buildings, which apparently is associated with a decrease in velocity near the surfaces. Originality. For the first time, calculations were made for Kharkiv, which made it possible to determine the heat island manifestation and to improve the microclimate research. Practical value. Mathematical modeling of heat transfer processes taking into account solar radiation allows us to investigate the interrelated problems of urban physics. In particular, the optimization of air temperature in large cities should be based on the results obtained, which will allow to more accurately determine the temperature fields and reduce their impact on human health.

Keywords

• heat urban island
• heat transfer
• urban development
• turbulence model
• solar radiation