Analysis of Flow Through a Convergent Nozzle at Sonic Mach Number for Area Ratio 4

Ambareen Khan; Nurul Musfirah Mazlan; Mohd Azmi Ismail

Authors

Ambareen Khan School of Aerospace Engineering, Engineering Campus, Universiti SainsMalaysia, Nibong Tebal, Pulau Pinang, 14300, Malaysia
Nurul Musfirah Mazlan School of Aerospace Engineering, Engineering Campus, Universiti SainsMalaysia, Nibong Tebal, Pulau Pinang, 14300, Malaysia
Mohd Azmi Ismail School of Mechanical Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, Pulau Pinang, 14300, Malaysia

Keywords:

Nozzle pressure ratio, base pressure, sudden expansion, the flow field

Abstract

The presence of a blunt base can be found in automobile industries as well as in the aerospace industry. The blunt base caused the lower base pressure than ambient pressure and resulted in significant value of the base drag. The present study addresses the effect of the base drag if the rectangular rib is located to the suddenly enlarged duct in which the flow from the convergent nozzle suddenly expandsusing CFD. The nozzle is operated at sonic Mach number, and the enlarged duct has a diameter of 20 mm. The height of the rib is varied from 1 mm to 3 mm while the width of the rib is maintained at 3 mm throughout the study. The rib is located at 1D (D = 20 mm), 2D, 3D, and 4D, and the nozzle pressure ratio is increased from 1.5 to 5 in the step of 0.5. The computational model is validated with experimental work, and then the pressure variations are analyzed. It is observed that the location of the rib is a prime factor in regulating the base pressure. As the rib is located downstream of reattachment point, the base pressure obtained is always higher than in duct without rib irrespective of any height.