@tomleslie last equations are not equations itself, they are rather restrictions, so i need velocity to be between 0 and 4. im not sure if there is a way to solve the problem with ecuations and inequalities on it, working with 4<= 4 Qi/pi Di^2 <=4. i uploaded a new file and wrote the inequalities or restrictions in the fsolve command, 10 equations and 10 inequalities... i also modified the Re numbers with an absolute value, although all solutions got before were positive, maybe there is a solution with a negative Q and maple cant find it because of the Re numbers being negative... thanks for your help aceitoso.mw

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