Phoenics

Phoenics [151] is a FVM-based, general-purpose CFD platform, which, at least for airflows within the urban canopy, provides similar modelling features and capabilities as CFX and Fluent. As the other CFD programs, Phoenics can solve for the most important conservation equations of mass, momentum, heat, chemical species, and turbulent parameters, towards the provision of results of microclimate parameters such as relative humidity, wind speed, turbulence intensity, and temperature. Similarly to the other CFD platforms, it provides access to the user to incorporate special physical models, such as evapotranspiration from vegetation. A substantial advantage of Phoenics over the other CFD tools is that it provides access to the source Fortran-based code rather than only offering the opportunity to incorporate user-defined models. Like previous tools, it possesses a wide variety of models to simulate turbulence, heat, and radiation transfer and, due to its wide validation, it can be confidently used to study microclimates in urban areas. Since it is not just a microclimate-oriented tool, expertise above average on computing and transport phenomena is required in order to develop a reliable microclimate model. The major difference is that it does not implement tetrahedral grids, and either a Body-Fitted or a hexahedral-unstructured grid option is available for complex geometries. The software includes a plant canopy module called FOLIAGE, which accounts for vegetation evaporation phenomena.

Fintikakis et al. [152] used Phoenics to study the urban microclimatic conditions in the historic centre of Tirana. They developed a microclimate model and incorporated it into the CFD platform towards the estimation of pedestrian thermal comfort in order to decide the best retrofitting measures (e.g., trees' kind and orientation, high albedo ground materials, earth-to-air heat exchangers) that ensure the best comfort conditions in strategic locations of the urban domain. Although a simple model was developed (evapotranspiration and radiation were neglected in the mathematical model and they were imposed as temperature boundary conditions taken from field measurements, instead), it provided adequate results at least for practical design purposes. Maragkogiannis et al. [153] combined Terrestrial Laser Scanners (TLS) and aerial ortho-photography with computational fluid dynamics (CFD) to study the thermal conditions of a public square in Chania, Greece. Yang et al. [154] reported that the software presented good structure for developing modular applications but required powerful computer or cloud computing to speed up simulations.

#### **3. Discussion**
