[Jsbsim-cvslogs] CVS: JSBSim/src/models/propulsion FGPropeller.cpp, 1.42, 1.43

[Ron J. <je...@us...>]

Update of /cvsroot/jsbsim/JSBSim/src/models/propulsion
In directory vz-cvs-3.sog:/tmp/cvs-serv23614/src/models/propulsion

Modified Files:
	FGPropeller.cpp 
Log Message:
Adjust VInduced formula to handle sign (direction) separately from magnitude.


Index: FGPropeller.cpp
===================================================================
RCS file: /cvsroot/jsbsim/JSBSim/src/models/propulsion/FGPropeller.cpp,v
retrieving revision 1.42
retrieving revision 1.43
diff -C2 -r1.42 -r1.43
*** FGPropeller.cpp	22 Dec 2011 22:13:59 -0000	1.42
--- FGPropeller.cpp	11 Feb 2012 15:14:27 -0000	1.43
***************
*** 229,234 ****
    // from momentum theory - see B. W. McCormick, "Aerodynamics, Aeronautics,
    // and Flight Mechanics" 1st edition, eqn. 6.15 (propeller analysis chapter).
!   Vinduced = 0.5 * (-Vel + sqrt(Vel*Vel + 2.0*Thrust/(rho*Area)));
! 
    // P-factor is simulated by a shift of the acting location of the thrust.
    // The shift is a multiple of the angle between the propeller shaft axis
--- 229,242 ----
    // from momentum theory - see B. W. McCormick, "Aerodynamics, Aeronautics,
    // and Flight Mechanics" 1st edition, eqn. 6.15 (propeller analysis chapter).
!   // Vinduced = 0.5 * (-Vel + sqrt(Vel*Vel + 2.0*Thrust/(rho*Area)))
!   // Since Thrust and Vel can both be negative we need to adjust this formula
!   // To handle sign (direction) separately from magnitude.
!   double Vel2sum = Vel*abs(Vel) + 2.0*Thrust/(rho*Area);
!   
!   if( Vel2sum > 0.0)
!     Vinduced = 0.5 * (-Vel + sqrt(Vel2sum));
!   else
!     Vinduced = 0.5 * (-Vel - sqrt(-Vel2sum));
!     
    // P-factor is simulated by a shift of the acting location of the thrust.
    // The shift is a multiple of the angle between the propeller shaft axis