The bleed models simulate a bleed boundary without the need to grid and simulate the bleed plenum on the other side. In the main passage, the properties at the edge of the local boundary layer are given by the Mach number (Mδ), total pressure (ptδ), and total temperature (Ttδ). The surface through which the bleed passes has a total surface area of Aregion and porosity (φ). The actual area of the bleed holes is denoted as Ableed and the mass flow rate though the holes is denoted by mbleed or mholes .
The bleed plenum total pressure and total temperature are denoted as pt plenum and Tt plenum. Since the plenum is at a near-stagnation condition, with a Mach number (M) approximately zero, the plenum static pressure (pplenum) is nearly the same as the plenum total pressure. The plenum chamber has an exit passage of area Aexit and discharge coefficient CD. The mass flow through the exit is mexit and the static pressure at the end of the passage is pexit.
During steady operation, the bleed mass flow rate (mbleed) must be the same as the mass flow rate through the bleed holes (mholes) and also the mass flow rate through the plenum exit (mexit).
Last updated 31 Oct 2011