Computational model of airflows underneath a lift-up building

Cilj ovog diplomskog rada je određivanje utjecaja niza parametara na strujanje zraka oko zgrade s izdignutim stambenim dijelom. Rad se temelji na simulacijama provedenim u računalnoj mehanici fluida. Za izradu računalne mreže je korišten komercijalni programski paket CF MESH+®, a za proračune je korišten programski paket otvorenog koda OpenFOAM®. U radu je korišten model stacionarnog trodimenzijskog turbulentnog strujanja nestlačivog fluida opisan osrednjenim Navier Stokesovim jednadžbama i k - ε modelom turbulencije, dok je strujanje uz zid modelirano zidnim funkcijama. Strujanje vjetra je modelirano koristeći dva tipa homogenog atmosferskog graničnog sloja pogonjenog smičnim naprezanjem i gradijentom tlaka. U radu je ispitan utjecaj parametara dimenzija i oblika izdignute zgrade na brzinu strujanja vjetra i koeficijent ugode na visinama koje odgovaraju visini pješaka u okolini zgrade. Analizirano je ukupno trideset različitih konfiguracija izdignute zgrade gdje su se mijenjale dimenzije zgrade, oblik nosivog dijela zgrade, kutovi nastrujavanja vjetra na zgradu te modeli homogenog atmosferskog graničnog sloja koji nastrujava na zgradu. Dobiveni rezultati koeficijenta ugode u okolini zgrade uspoređeni su s rezultatima dostupnim u literaturi te je postignuta vrlo dobra podudarnost (relativno odstupanje manje od 6%). Rezultati analize ukazuju na činjenicu da visina zgrade te kut nastrujavanja imaju dominantan utjecaj na strujanje zraka u blizini zgrade u odnosu na vrstu homogenog atmosferskog graničnog sloja koji nastrujava na zgradu i oblik nosivog dijela zgrade.The scope of this work is to determine the parameters that influence the airflows around lift up buildings. The study is based on the Computational Fluid Mechanics (CFD) simulations. The CF MESH+® commercial software package was used to create the volume meshes and OpenFOAM® was used to perform the CFD calculations. The stationary 3D turbulent flow model of a non compressible fluid described by the averaged Navier Stokes equations and the k - ε turbulence model were used, whereas the flow near the wall was modeled by using the wall functions. The wind flow was modeled as the atmospheric boundary layer (ABL) for two types of boundary conditions. The effect of a number of parameters on wind characteristics at the pedestrian height of 2 m was analyzed. In particular, thirty simulations were performed to analyze the effects of the building dimensions and shape and the flow incidence angle for two sets of boundary conditions at the inlet of the computational domain. The results were compared with the results that are available in the literature and a very good match was obtained with the discrepancies less than 6%. It was observed that the building height and the flow incidence angle dominate the wind characteristics at 2 m height around the lift up building compared to the effects of the inlet boundary conditions and the shape of the lowest portion (core) of the building