Sorry for the late reply, so I went on to use species transport with hydrogen-air mix in order to patch 2 gases in different sections and i all worked fine like expected when i applied 10 bar to driver section and 1 bar to the driven section, also applying 1 value to hydrogen. Later when i increased the pressure and patched 20 bar instead of 10 bar, the results went bad and when i mean bad, when i ploted the static pressure, it when to zero instead of 20 bar in the driver section and also in the driven section and i dont know why does this happen