Numerical modeling validation for the microclimate thermal condition of semi-closed courtyard spaces between buildings

Abstract In this study, the microclimate model ENVI-met version 4 was evaluated with field data inside courtyard spaces. The measurements were planned in different climate conditions in summer and winter at different points inside the courtyard located in Hannover, Germany. Climate variables —including air temperature (Ta), relative humidity (RH), wind speed (WS) and mean radiant temperature (Tmrt) — were investigated. The comparison between observation and prediction was performed while considering the accuracy of the model with the different domain and cell sizes, the different lateral boundary conditions for turbulence (LBC for TKE) and the time step size for flow. Consequently, the 2 × 2 × 1 m3 cell-sized model with cyclic LBC for TKE and tflow = 0 s lead to quicker simulation and reliable results. This study provides further confidence that the ENVI-met model is capable of predicting the microclimate variables inside medium-narrow courtyards with an acceptable accuracy. The root mean square error (RMSE) value at the center of the shaded courtyard was calculated as approximately 0.73 °C for Ta, 3.34% for RH, 0.01 m/s for WS and 8.44 °C for Tmrt. However, due to the model resolution, inaccuracies in the values are displayed for Tmrt in the sun-exposed areas.

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