Flow through a laid cilinder (tank truck) connected to a 10m horizontal Dn3 pipe

Hi everybody !

I need to know how to compute the total time to completely empty a truck tank (by gravity flow). This tank is a cilindrical one and has in its bottom a nozzle of 3 inches, connected to a 3" diameter pipe with total lentgh of 10 meters (it's in horizontal). The pipe discharges to atmosphere and the tank is also open to atmosphere. The tank is in laid position (horizontal) and has a length of 13m and a diameter of 2m. It contains initially 35m3 of a liquid that must be drained. I'd like to have an expression of Flow as a function of time ( F=F(t)).

Any idea? please help me!

Thanks a lot