Thompson, "On the excitation of Gortler vortices by distributed roughness elements
," Theoretical and Computational Fluid Dynamics, vol.
The increased amount of roughness elements
, which are mainly composed of buildings and road networks in urban areas, dramatically alters the surface roughness and urban boundary layer dynamics , which in turn results in more frequent air pollution and extreme weather.
In another experiment conducted by Verma and Prasad , roughness elements
in the form of circular wires of different diameters were provided on the absorber plate at varying pitches.
Theoretically, [z.sub.0] has been found to be closely correlated with the geometry of surface elements including mean height, frontal area index (frontal area of roughness elements
per unit ground area), plan area index (fraction of unit ground area covered by roughness elements
), and the arrangement of roughness elements
and is much heightened over urban surfaces because of the drag exerted by buildings and other infrastructures [18-22].
(1-3) have demonstrated experimentally that significant cycle time reductions can be achieved by adding pins (28% reduction) or roughness elements
(18% reduction) to the exterior of a mold surface.
m = empirical factor accounting for the increased difference between maximum and mean shear stress on the erodible surface resulting from the flow around roughness elements
Additionally, ribs serve as artificial roughness elements
in a fluid flowing channel to improve the convective heat transfer by creating turbulence in the flow.
* The use of some regular (normally rectangle) roughness elements
 or irregular and randomly distributed roughness elements
 in the computation domain.
A caliper rod (Figure 1) was used to read the linear distance, L2, resulting from roughness elements
The performance of artificially roughened solar air heater has been tested experimentally over years for different shapes, sizes, and orientations of roughness elements
to enhance the heat transfer coefficient with minimum pumping power.