English to Arabic Tech/Engineering Mechanics / Mech Engineering hydraulics

Control valves particularly susceptible to cavitation. Pressure may drop to critical values in the reduced cross section of the restriction due to increased flow velocity. Behind the constriction, pressure mounts again and the gas bubbles collapse. The surface of the pipe wall in this area may be damaged significantly by the impact of the striking jet of water and by the shock wave from the imploding bubbles.

I only need "reduced" in this particular context. It cannot be المقطع العرضي المخفض ?
Thanks a lot for any help in advance!