Need urgent help: Flow through a pipe hi guys. i have a long question. first read the attachment to understand part A. part A To simplify the flow, we need to use POLAR COORDINATES CYLINDRICAL navier stokes equation and continuity equation. the energy equation can be ignored. first we need to make some assumptions. and also explain why these assumptions were made. basically i can make as many assumptions as i want to i have to justify each assumptions. what i have said is that we can assume the flow to be 2D and not 3D. this cancels out the theta (radial) term in the continuity and navier stokes equations (i think). but i need to say why does this happen. i have also assumed that the flow is steady state, inviscid, isothermal at the inlet and outlet. fully developed at the outlet as well. but how can these assumptions hold? also, the flow starts 1D at the inlet and as i have assumed it becomes 2D during the pipe, i need to explain how does this happen. what about part B. what boundary conditions can i say. there are 3 vairables...density, velocity and pressure therefore 3 boundary conditions but haw can i explain these? also, what other assumptions can i say. IF YOU DONT UNDERSTAND WHAT I SAID, PLEASE TELL ME. THANKS PLEASE PLEASE PLEASE I NEED HELP WITH THIS A LOT.