flightgear/src/FDM/JSBSim/FGAuxiliary.cpp

/*******************************************************************************

 Module:       FGAuxiliary.cpp
 Author:       Jon Berndt
 Date started: 01/26/99
 Purpose:      Calculates additional parameters needed by the visual system, etc.
 Called by:    FGSimExec

 ------------- Copyright (C) 1999  Jon S. Berndt (jsb@hal-pc.org) -------------

 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
 Foundation; either version 2 of the License, or (at your option) any later
 version.

 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 details.

 You should have received a copy of the GNU General Public License along with
 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 Place - Suite 330, Boston, MA  02111-1307, USA.

 Further information about the GNU General Public License can also be found on
 the world wide web at http://www.gnu.org.

FUNCTIONAL DESCRIPTION
--------------------------------------------------------------------------------
This class calculates various auxiliary parameters.

REFERENCES
  Anderson, John D. "Introduction to Flight", 3rd Edition, McGraw-Hill, 1989
                    pgs. 112-126
HISTORY
--------------------------------------------------------------------------------
01/26/99   JSB   Created

********************************************************************************
INCLUDES
*******************************************************************************/

#include "FGAuxiliary.h"
#include "FGTranslation.h"
#include "FGRotation.h"
#include "FGAtmosphere.h"
#include "FGState.h"
#include "FGFDMExec.h"
#include "FGFCS.h"
#include "FGAircraft.h"
#include "FGPosition.h"
#include "FGOutput.h"

/*******************************************************************************
************************************ CODE **************************************
*******************************************************************************/

FGAuxiliary::FGAuxiliary(FGFDMExec* fdmex) : FGModel(fdmex)
{
  Name = "FGAuxiliary";
  vcas = veas = mach = qbar = pt = 0;
  psl = rhosl = 1;
}


FGAuxiliary::~FGAuxiliary()
{
}


bool FGAuxiliary::Run()
{
  float A,B,D;

  if (!FGModel::Run()) {
    GetState();
    if(mach < 1)    //calculate total pressure assuming isentropic flow
      pt=p*pow((1 + 0.2*mach*mach),3.5);
  else
  {
    // shock in front of pitot tube, we'll assume its normal and use
    // the Rayleigh Pitot Tube Formula, i.e. the ratio of total
    // pressure behind the shock to the static pressure in front

    B = 5.76*mach*mach/(5.6*mach*mach - 0.8);

    // The denominator above is zero for Mach ~ 0.38, for which
    // we'll never be here, so we're safe

    D = (2.8*mach*mach-0.4)*0.4167;
    pt = p*pow(B,3.5)*D;
  }

  A = pow(((pt-p)/psl+1),0.28571);
  vcas = sqrt(7*psl/rhosl*(A-1));
  veas = sqrt(2*qbar/rhosl);

  } else {

  }

  return false;
}

void FGAuxiliary::GetState(void)
{
  qbar = Translation->Getqbar();
  mach = Translation->GetMach();
  p = Atmosphere->GetPressure();
  rhosl = Atmosphere->GetDensitySL();
  psl = Atmosphere->GetPressureSL();
}