DMSModel:

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   Double Multiple Streamtube Model.
   Predict upwind and downwind interference parameters.
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   Form:
   [u, upm] = DMSModel(af,bld,rot,wnd,DynStlModel,ControlAlgo,
                       nItLim,nAngStps)
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   ------
   Inputs
   ------
    af             (1,1)      Airfoil data structure
                              .reCL    (1,:) Reynolds number
                              .alphaCL (1,:) Angle of attack (deg)
                              .cL      (:,:) Lift coefficient
                              .reCD    (1,:) Drag Reynolds number
                              .alphaCD (1,:) Angle of attack (deg)
                              .cD      (:,:) Drag coefficient
                              .reCM    (1,:) Reynolds number
                              .alphaCM (1,:) Angle of attack (deg)
                              .cM      (:,:) Moment coefficient
                              .alpha0  (1,1) Angle of atack for zero lift
   bld              (1,1)     Blade data structure
                              .c       (1,1) Chord (m)
                              .H       (1,1) Blade half length (m)
                              .thknss  (1,1) Blade thickness (m)
   rot              (1,1)     Rotor data structure
                              .R       (1,1) Rotor radius (m)
                              .N       (1,1) Number of blades
                              .omega   (1,1) Rotor speed (rad/s)
                              .zR      (1,1) Ground clearance (m)
   wnd              (1,1)     Wind data structure
                              .Vinf    (1,1) Free stream wind speed (m/s)
                              .alphaw  (1,1) Wind shear component
                              .rho     (1,1) Air density (kg/m^3)
                              .nu      (1,1) Kinematic viscosity (m^2/2)
   DynStlMdl        (1,1)     String specifying Dynamic Stall Model 
   ControlAlgo      (1,1)     String specifying Control Algorithm

   -------
   Outputs
   -------
   u               (1,1)     Upwind interference parameter
   upm             (1,1)     Downwind interference parameter

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   References

   [1] I. Paraschivoiu, "Double-Multiple Streamtube Model for Studying 
   Vertical Axis Wind Turbines", Journal of Propulsion, Vol. 4, No. 4, 
   pp 370-377

   [2] Y. Staelens, F. Saeed, and I. Paraschivoiu, "A straight-bladed
   variable-pitch VAWT concept for improved power generation", Proc. 41st
   Aerospace Sciences Meeting and Exhibit, 2003, Reno, NV; AIAA-2003-0524

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   Copyright (c) 2009, 2010 Princeton Satellite Systems, Inc.
   All rights reserved.
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