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Added a new turbulence type ttStandard, and made it the default.

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ttStandard is copied from ttBerndt, with the following modifications:

1. All turbulence is diminished within three wingspans of the ground.

2. The horizontal forces are used to calculate the moments, but then
   zeroed out so that only the vertical force is actually applied to
   the aircraft.

3. The yaw moment is not used.

In fact, the horizontal forces and the yaw moment should be allowed,
but they are extremely rare compared to the vertical force and the
pitch/roll moments.  For now, simply zeroing them gives the most
accurate feel.
This commit is contained in:
david 2003-03-16 21:14:45 +00:00
parent b9985548d4
commit b3930c9c60
2 changed files with 50 additions and 2 deletions
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50
src/FDM/JSBSim/FGAtmosphere.cpp
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@ -89,7 +89,8 @@ FGAtmosphere::FGAtmosphere(FGFDMExec* fdmex) : FGModel(fdmex)
MagnitudedAccelDt = MagnitudeAccel = Magnitude = 0.0;
// turbType = ttNone;
turbType = ttBerndt;
turbType = ttStandard;
// turbType = ttBerndt;
TurbGain = 0.0;
bind();
@ -261,6 +262,53 @@ void FGAtmosphere::Calculate(double altitude)
void FGAtmosphere::Turbulence(void)
{
switch (turbType) {
case ttStandard: {
vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));
vDirectiondAccelDt(eZ) = 1 - 2.0*(double(rand())/double(RAND_MAX));
MagnitudedAccelDt = 1 - 2.0*(double(rand())/double(RAND_MAX)) - Magnitude;
MagnitudeAccel += MagnitudedAccelDt*rate*State->Getdt();
Magnitude += MagnitudeAccel*rate*State->Getdt();
vDirectiondAccelDt.Normalize();
vDirectionAccel += vDirectiondAccelDt*rate*State->Getdt();
vDirectionAccel.Normalize();
vDirection += vDirectionAccel*rate*State->Getdt();
vDirection.Normalize();
// Diminish turbulence within three wingspans
// of the ground
vTurbulence = TurbGain*Magnitude * vDirection;
double HOverBMAC = Position->GetHOverBMAC();
if (HOverBMAC < 3.0)
vTurbulence *= (HOverBMAC / 3.0) * (HOverBMAC / 3.0);
vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
vBodyTurbGrad = State->GetTl2b()*vTurbulenceGrad;
vTurbPQR(eP) = vBodyTurbGrad(eY)/Aircraft->GetWingSpan();
// if (Aircraft->GetHTailArm() != 0.0)
// vTurbPQR(eQ) = vBodyTurbGrad(eZ)/Aircraft->GetHTailArm();
// else
// vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
if (Aircraft->GetVTailArm())
vTurbPQR(eR) = vBodyTurbGrad(eX)/Aircraft->GetVTailArm();
else
vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
// Clear the horizontal forces
// actually felt by the plane, now
// that we've used them to calculate
// moments.
vTurbulence(eX) = 0.0;
vTurbulence(eY) = 0.0;
break;
}
case ttBerndt: {
vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));

2
src/FDM/JSBSim/FGAtmosphere.h
View file

@ -161,7 +161,7 @@ public:
private:
double rho;
enum tType {ttBerndt, ttNone} turbType;
enum tType {ttStandard, ttBerndt, ttNone} turbType;
int lastIndex;
double h;