A Numerical Study on the Pressure Variation in a Sudden Expansion and a Sudden Expansion with Central Restriction

In this paper, a numerical study on the performance of sudden expansion with central restriction, viewed as a diffuser, has been carried out. The two dimensional steady differential equations for conservation of mass and momentum are solved for Reynolds number(Re) from 10 to 100 and CR from 0% to 30% for an aspect ratio (AR) of 2 and fully developed velocity profile at inlet. From the study, it is revealed that for sudden expansion, maximum wall pressure decreases with the increase in Re. Sudden expansion with central restriction also behaves in same way. Location of the maximum wall pressure increases with increase in Re for both sudden expansion and sudden expansion with central restriction. The value of maximum average static pressure increases with increase in Re for both sudden expansion and sudden expansion with central restriction. Location of the maximum average static pressure from the throat, which may be considered as the effective length of the diffuser, increases with Re for both the cases. In case of sudden expansion with central restriction, maximum average static pressure increases with the increase in CR but its location from throat remains more or less same, at a particular value of Re. In comparison to a simple sudden expansion, the magnitude of maximum average static pressure is more and the location of maximum average static pressure from the throat is less for sudden expansion with central restriction.

Therefore, choice of the configuration of sudden expansion with central restriction, as a diffuser, is more attractive in comparison to the configuration of a simple sudden expansion.