Axisymmetric geometries(combustor) in Gambit

pankaj shukla

Dear friends, I am sending a problem of mine to you in which i have made an axisymmetric geometry of a combustor chamber with dome shaped head(annular).The flow coming from a diffuser is split into two annuli due to the dome shaped head or flame tube.The flow splits into the ratio as

mass in outer annulus /mass in inner annulus=1.3. My first problem pertains to geometry in gambit.The problem is that the axis passing through the centre of the flame tube and diffuser is not axis of syymetry but is situated at a distance of 130.2 mm from lower annulus.Have i to connect this geometry to the centreline ( at 130.2 mm)so that one face more connected to the main geometry is made.what boundary conditions will I have to put in this face(Where no analysis is to be done). I have given boundary conditions of velocity inlet at diffuser and outflow at two annuli.Accordingly I have given mass rate weightings as .5653 and .4347.Is it correct.

Another thing i want to know is that If the length of the annuli ( the Distance measured from extit of two annuli to end point of hemisperical flame tube )is six times the diameter of the annulus,is there any restriction Regarding the use of outflow condition in such cases.what will be the appropriate boundary condtion then.

please tell me anything else concerned to this problem so i can solve it .Hoping for your frindly advice.

pankaj