Use tiedPropertyLists instead of manually matched tie/untie calls.

[flightgear.git] / src / FDM / JSBSim / FGJSBBase.cpp

diff --git a/src/FDM/JSBSim/FGJSBBase.cpp b/src/FDM/JSBSim/FGJSBBase.cpp
index ccf098b598e0bf3e506fcf0a94da5e22af178e29..f0bc3ed48e097c1cad333fecc73c921bd2befd2a 100644 (file)
--- a/src/FDM/JSBSim/FGJSBBase.cpp
+++ b/src/FDM/JSBSim/FGJSBBase.cpp
@@ -44,7 +44,7 @@ INCLUDES
 
 namespace JSBSim {
 
-static const char *IdSrc = "$Id: FGJSBBase.cpp,v 1.31 2011/07/27 03:55:48 jberndt Exp $";
+static const char *IdSrc = "$Id: FGJSBBase.cpp,v 1.32 2011/10/22 14:38:30 bcoconni Exp $";
 static const char *IdHdr = ID_JSBBASE;
 
 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -283,5 +283,67 @@ double FGJSBBase::GaussianRandomNumber(void)
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+double FGJSBBase::VcalibratedFromMach(double mach, double p, double psl, double rhosl)
+{
+  double pt,A;
+
+  if (mach < 0) mach=0;
+  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 of
+    // the normal shock assumption should not be a bad one -- most supersonic
+    // aircraft place the pitot probe out front so that it is the forward
+    // most point on the aircraft.  The real shock would, of course, take
+    // on something like the shape of a rounded-off cone but, here again,
+    // the assumption should be good since the opening of the pitot probe
+    // is very small and, therefore, the effects of the shock curvature
+    // should be small as well. AFAIK, this approach is fairly well accepted
+    // within the aerospace community
+
+    // The denominator below is zero for Mach ~ 0.38, for which
+    // we'll never be here, so we're safe
+
+    pt = p*166.92158*pow(mach,7.0)/pow(7*mach*mach-1,2.5);
+  }
+
+  A = pow(((pt-p)/psl+1),0.28571);
+  return sqrt(7*psl/rhosl*(A-1));
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+double FGJSBBase::MachFromVcalibrated(double vcas, double p, double psl, double rhosl)
+{
+  double pt = p + psl*(pow(1+vcas*vcas*rhosl/(7.0*psl),3.5)-1);
+
+  if (pt/p < 1.89293)
+    return sqrt(5.0*(pow(pt/p, 0.2857143) -1)); // Mach < 1
+  else {
+    // Mach >= 1
+    double mach = sqrt(0.77666*pt/p); // Initial guess is based on a quadratic approximation of the Rayleigh formula
+    double delta = 1.;
+    double target = pt/(166.92158*p);
+    int iter = 0;
+
+    // Find the root with Newton-Raphson. Since the differential is never zero,
+    // the function is monotonic and has only one root with a multiplicity of one.
+    // Convergence is certain.
+    while (delta > 1E-5 && iter < 10) {
+      double m2 = mach*mach; // Mach^2
+      double m6 = m2*m2*m2;  // Mach^6
+      delta = mach*m6/pow(7.0*m2-1.0,2.5) - target;
+      double diff = 7.0*m6*(2.0*m2-1)/pow(7.0*m2-1.0,3.5); // Never zero when Mach >= 1
+      mach -= delta/diff;
+      iter++;
+    }
+
+    return mach;
+  }
+}
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
 } // namespace JSBSim