The flow to the test cell goes through three parts, namely the settling chamber, a honeycomb section
and a contraction cone. Fine screens are mounted in the settling chamber for reducing the turbulence}.
level of flow entering the test section. The contraction ratio of the contraction cone in area units is 10:1.
The contraction cone reduces the spatial irregularities in the velocity distribution and helps in the decay of turbulence intensity by proper stretching of the vortices. The function of the honeycomb is to straighten the flow by damping the transverse components of velocity, and to reduce the turbulence level by suppressing the turbulence scales that are larger than the size of a honeycomb cell. The screens are used to suppress the small disturbances generated at the outlet tips of the honey comb. Proper mesh size gradation has been utilized by examining the diameter of the elements of the honeycomb, and hence the length scale of the vortices generated. Specially, two screens, one with a coarse grid (10 per cm²) and the other with a fine grid (100 per cm²) have been used in the test cell.

Fig 3.11: Imaging system for PIV