Airflow patterns around obstacles with arched and pitched roofs: Wind tunnel measurements and direct simulation

• Turbulent airflow around arched and pitched roof obstacles is simulated by 2D DNS.
• Navier–Stokes and continuity equations are solved with the Finite element method.
• Wind tunnel experiments are performed to validate the numerical predictions.
• Instantaneous and averaged velocities are predicted and measured.
• Different obstacle roof effects on airflow patterns and TKE are studied.

Achieving accurate numerical predictions of airflow around buildings is challenging due to the dynamic characteristics of wind. Buildings are usually considered as obstacles to the wind. A time-dependent simulation model has been applied for the prediction of the turbulent airflow around obstacles with arched and pitched roof geometry, under wind tunnel conditions. The numerical model is based on the direct solution of transient Navier–Stokes and continuity equations using the Galerkin finite element method. To verify the reliability of the model an experiment was conducted inside a wind tunnel and the air velocity and turbulent kinetic energy profiles were measured around two small-scale obstacles with an arched-type and a pitched-type roof, respectively. The velocity components and the turbulent kinetic energy values were used to demonstrate a dynamic and statistical analysis of this complex flow. The wind tunnel tests presented good agreement with the numerical simulations with respect to airflow patterns. The different roof geometry of obstacles affected the instantaneous and time-mean averaged parameters of the flow. According to the instantaneous results of the numerical solution, airflow patterns presented fluctuating characteristics mainly downstream of the obstacles. Intense variations were shown in streamlines and velocity components, both at the arched-type and the pitched-type obstacle, starting from the upstream corner of the roof and the top of the roof respectively. The time-dependent simulation of the flow parameters can provide important information on instantaneous fluctuations of the complex flow phenomena around arched-type and pitched-type roof obstacles which cannot be obtained by the time-mean averaged approach.