KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES OBSTACLE IN A STEADY, UNIFORM WIND (a) Flow round a section of a tall rectangular building in a steady, uniform wind. (b) Vortices on the roof of a rectangular building. a) b)

KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES

Region B’BCDD’- Separated flow forming the wake Inside the wake the wind flow is very turbulent (turbulence intensity up to 40%) BB’ and DD’- shear layers (the greatest level of fluctuating component) Corner vorticies on the roof are responsible for the high peak suction near the edges of buildings (important for ventilation system) OBSTACLE IN A STEADY, UNIFORM WIND Flow structure in the wake behind the plate

KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES OBSTACLE IN A STEADY, UNIFORM WIND Visualization of the flow behind the rectangular obstacle

KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES OBSTACLE IN A STEADY, UNIFORM WIND Drag coefficient for an obstacle of rectangular cross-section

KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES OBSTACLE IN A STEADY, UNIFORM WIND wind direction Sharp cornersRounded corners r/h= Drag coefficients for objects with sharp and rounded corners

KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES OBSTACLE IN A STEADY, UNIFORM WIND Influence of the rounded corners

OBJECT IN TURBULENT INCIDENT FLOW KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES Two main effects of the inlet turbulence: The separated flow can re-attach at D’. The second separation occurs at C, so the boundaries of the wake are B’BCC’ Shear layers BB’ and CC’ are thickened.

KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES OBJECT IN TURBULENT INCIDENT FLOW Influence of turbulence untensity on drag coefficient

EFFECT OF SHEAR IN INCIDENT WIND KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES The effects of shear in the inclined wind on the flow round a building. (a) Stream lines. (b) Vortex lines. Upstream of an obstacle in a shear flow on the ground (boundary layer) a vortex is found which creates a down-wash on the front face of the obstacle. Explanation: Vortex lines swept in by the inclined flow are “piled” up. Swirling flow exists downwind on either side of the building.

KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES EFFECT OF SHEAR IN INCIDENT WIND Turbulent boundary layer separation in front of a building. Plan view shows trajectories at ground level.

KINEMATICAL STUDY OF THE FLOW AROUND SURFACE-MOUNTED OBSTACLES EFFECT OF SHEAR IN INCIDENT WIND