[hyebo1]

Hello im new in this and im developing a code in matlab to modelling a 1D flow compressible through a manifold. I have got excellents results of accuracy when i simulate shock tubes tests ( Riemman, sod shock tube....) but when i try to model "DeHaller" test which its basically a cylinder of high pressure which discharge flow through a pipe i got wrong results. The fact its that here i have to apply two boundary conditions, one for the in flow into the pipe from the cylinder and the second one is at the open end of the pipe which discharge the flow into the atmosphere. Im struggled in the boundary conditions which define the properties of the fluid at the beginning of the pipe when the flow go out of the cylinder and get into the pipe because according to the equations it says that the Pressure in the boundary (beginning of the manifold in which the flow get inside) is equal to the pressure in "p", being "p" the first point of the manifold. And i dont know how to resolve that because to calculate the pressure in "p" with euler equations i need to know the pressure in the step before or point before which is the boundary.

Im new and im pretty sure that has an easy solution so i would apreciate any help.