Effect of Lobe Count and Lobe Length of Corrugated Lobed Nozzle on Subsonic Flow Characteristics

Abstract

The corrugated lobed nozzle is an emerging research topic in jet flow dynamics, and little investigation has been conducted on its effect on flow characteristics. Thus, in this study, the effects of lobe count and lobe length of corrugated lobed nozzles on subsonic jet characteristics were experimentally investigated by analyzing the velocity profiles of the jets emanating from the nozzles. The Pitot tube readings were obtained by varying the count (4 ≤ N ≤ 8) and length (10 mm ≤ L ≤ 20 mm) of corrugated lobes. These measurements were then compared with the experimental readings obtained for a baseline circular nozzle. The nozzle pressure ratio (NPR) and exit nozzle area were kept identical at 1.5 and 600 mm2, respectively, for all nozzle configurations. The most striking observation was the ‘W’-shaped radial velocity profile of the corrugated nozzle, which differed from the ‘Top hat’ profile of the baseline circular nozzle. Additionally, the length of the potential central region of the corrugated nozzle was always shorter than that of the baseline circular nozzle, indicating the early occurrence of turbulence in the former. It was found that the lobe length had a meagre effect on the velocity variation in the jet issuing from the corrugated nozzle, whereas the lobe count had a significant effect on the velocity profile. However, as the lobe count increased, the velocity profile of the corrugated nozzle gradually resembled that of the circular nozzle. The findings of this study would be beneficial for selecting a proper lobe count and lobe length while designing and implementing a corrugated lobed nozzle.

Keywords

• corrugation
• jet
• lobe
• pitot tube
• velocity profile