In many cases it is useful to prescribe mass flow rate together with inlet velocity angles. Meridian angle and circular angle are prescribed. Their definitions can be found in figures () and (). p:

 boundaryField
 {
     ".*_inlet"
    {
     type            zeroGradient;
    }
 }

U:

 boundaryField
 {
    ".*_inlet"
    {
        type            turboMassFlowUniformDirectedInletVelocity;
        value           $internalField;
        axis            (0 0 1); // axis z-plus
        origin          (0 0 0);
        merAng          90; //         => from axis
        circAng         120.0; //      => from tangent
        flowRate        0.031923077; 
    }
  }