Perforated-plate turbulence: Orifice versus converging nozzle

The classical grid turbulence is revisited in an effort to better understand the role of the finite-thickness flow passage of the turbulence generator. The virtually zero-thickness orificed perforated plate (OPP) is contrasted with its reversed counterpart, the converging-nozzled perforated plate (CNPP). The respective turbulent flows are detailed via a triple-wire of a constant-temperature hot wire anemometer. The two flows are compared in terms of the spatial evolution of the essential turbulence characteristics, including the various turbulence intensities and length scales. As expected, a higher level of turbulence resulted from the sharp edges of the OPP. Surprisingly, the finite-thickness converging passages of the CNPP caused the other turbulence parameters to behave rather perplexingly