Why pressure at the cylinder input is higher than the pressu

Why pressure at the cylinder input is higher than the pressure at the pump output in the original figure? Does it make sense? Please explain. In the original figure, fitting is located exactly at the same distance from pump and cylinder. How does changing the location of the fitting affect the result? Why at end of the simulation, we see a pressure jump (see second figure)? How do you think we can fix this issue not to damage the equipment? Original figure!

Solution

I am assuming this is an IC engine and the working fluid is gaseous,

so it is a compressible flow system, in a transient (time varient) compressible system, pressure distributin is not uniform necessarily.

in the picture, it seems like the piston is at the bottom dead centre, or approaching BDC ( in the given picture the cylinder is upside down, so in this case the piston is at the top most point, do not confuse with the terms). At this position, the piston is retarding, so there will be ramming effect ( like when a door is closed suddenly while people are passing) so there will be a pile up of molecules near the piston topland, hence higher density and pressure than the average. It is a usual thing in an IC engine, increase in pressure at BDC during suction stroke and decreased pressure at TDC during exhaust stroke