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YASim: attempt to fix MAC calculation for multiple wing sections.

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This commit is contained in:
Henning Stahlke 2018-02-13 23:11:27 +01:00 • committed by Florent Rougon
parent 1727af3638
commit c2e7842110
4 changed files with 31 additions and 36 deletions
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2
src/FDM/YASim/Airplane.cpp
View file

@ -17,8 +17,6 @@
namespace yasim {
//default prop names
// gadgets
inline float abs(float f) { return f<0 ? -f : f; }

4
src/FDM/YASim/Math.hpp
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@ -14,7 +14,9 @@ public:
if(val > max) return max;
return val;
}
static float weightedMean(float x1, float w1, float x2, float w2) {
return (x1*w1 + x2*w2)/(w1+w2);
}
// Simple wrappers around library routines
static inline float abs(float f) { return (float)::fabs(f); }
static inline float sqrt(float f) { return (float)::sqrt(f); }

49
src/FDM/YASim/Wing.cpp
View file

@ -59,7 +59,7 @@ int Wing::addWingSection(float* base, float chord, float wingLength, float taper
}
// append section: Calculate wing MAC from MACs of section and prev wing
else {
_mac = Wing::calculateMAC(_mac, ws->getMAC());
_mac = _weightedMeanChord(_mac, _area, ws->getMAC(), ws->getArea());
_netSpan += ws->_sectionSpan;
_area += ws->getArea();
_meanChord = _meanChord * ws->_meanChord * 0.5f;
@ -90,6 +90,16 @@ void Wing::_chord2float(Chord c, float* pos)
pos[2] = c.z;
}
Chord Wing::_weightedMeanChord(Chord a, float wa, Chord b, float wb)
{
Chord c;
c.length = Math::weightedMean(a.length, wa, b.length, wb);
c.x = Math::weightedMean(a.x, wa, b.x, wb);
c.y = Math::weightedMean(a.y, wa, b.y, wb);
c.z = Math::weightedMean(a.z, wa, b.z, wb);
return c;
}
void Wing::WingSection::calculateGeometry()
{
_meanChord = _rootChord.length*(_taper+1)*0.5f;
@ -147,15 +157,15 @@ void Wing::WingSection::calculateSpan()
void Wing::WingSection::calculateMAC()
{
// http://www.nasascale.org/p2/wp-content/uploads/mac-calculator.htm
//const float commonFactor = _rootChord.length*(0.5+_taper)/(3*_rootChord.length*(1+_taper));
//const float commonFactor = _rootChord.length*0.5(1+2*_taper)/(3*_rootChord.length*(1+_taper));
const float commonFactor = (0.5+_taper)/(3*(1+_taper));
_mac.length = _rootChord.length-(2*_rootChord.length*(1-_taper)*commonFactor);
// y distance to root chord
_mac.y = Math::abs(2*(_tipChord.y-_rootChord.y))*commonFactor;
// MAC leading edge x = midpoint + half MAC length
_mac.x = _rootChord.x-Math::tan(_sweepAngleCenterLine)*_mac.y + _mac.length/2;
_mac.z = _rootChord.z+Math::tan(_dihedral)*_mac.y;
_mac.x = -Math::tan(_sweepAngleCenterLine)*_mac.y + _mac.length/2 + _rootChord.x;
_mac.z = Math::tan(_dihedral)*_mac.y + _rootChord.z;
//add root y to get aircraft coordinates
_mac.y += _rootChord.y;
}
@ -178,23 +188,6 @@ void Wing::WingSection::setIncidence(float incidence)
((SurfRec*)_surfs.get(i))->surface->setIncidence(incidence + _sectionIncidence);
}
/// root and tip (x,y) coordinates are on leading edge
Chord Wing::calculateMAC(const Chord root, const Chord tip)
{
assert(root.length > 0);
// http://www.nasascale.org/p2/wp-content/uploads/mac-calculator.htm
//taper = tip.length / root.length;
const float commonFactor = (root.length*0.5+tip.length)/(3*(root.length+tip.length));
Chord m;
m.length = root.length-(2*(root.length - tip.length)*commonFactor);
float dy = tip.y - root.y;
m.y = Math::abs(2*dy)*commonFactor;
m.z = root.z + m.y*(tip.z-root.z)/dy;
m.x = root.x - m.y*(root.x - tip.x)/dy;
m.y += root.y;
return m;
}
void Wing::setFlapParams(int section, WingFlaps type, FlapParams fp)
{
((WingSection*)_sections.get(section))->_flapParams[type] = fp;
@ -340,7 +333,7 @@ void Wing::compile()
for(int j=0; j<nSegs; j++) {
float frac = start + (j+0.5f) * (end-start)/nSegs;
float pos[3];
interp(base, tip, frac, pos);
_interp(base, tip, frac, pos);
float chord = ws->_rootChord.length * (1 - (1-ws->_taper)*frac);
float weight = chord * segWid;
@ -360,7 +353,7 @@ void Wing::compile()
// called before we were compiled.
setIncidence(_incidence);
}
writeInfoToProptree();
_writeInfoToProptree();
}
float Wing::getArea() const
@ -495,14 +488,14 @@ void Wing::WingSection::newSurface(Version* _version, float* pos, float* orient,
_surfs.add(sr);
}
void Wing::interp(const float* v1, const float* v2, const float frac, float* out)
void Wing::_interp(const float* v1, const float* v2, const float frac, float* out)
{
out[0] = v1[0] + frac*(v2[0]-v1[0]);
out[1] = v1[1] + frac*(v2[1]-v1[1]);
out[2] = v1[2] + frac*(v2[2]-v1[2]);
}
void Wing::writeInfoToProptree()
void Wing::_writeInfoToProptree()
{
if (_wingN == nullptr)
return;
@ -548,9 +541,9 @@ void Wing::writeInfoToProptree()
sectN->getNode("chord", true)->setFloatValue(ws->_rootChord.length);
sectN->getNode("incidence-deg", true)->setFloatValue(ws->_sectionIncidence * RAD2DEG);
sectN->getNode("mac", true)->setFloatValue(ws->_mac.length);
sectN->getNode("mac-x", true)->setFloatValue(ws->_mac.x);
sectN->getNode("mac-y", true)->setFloatValue(ws->_mac.y);
sectN->getNode("mac-z", true)->setFloatValue(ws->_mac.z);
sectN->getNode("mac-x", true)->setFloatValue(ws->getMACx());
sectN->getNode("mac-y", true)->setFloatValue(ws->getMACy());
sectN->getNode("mac-z", true)->setFloatValue(ws->getMACz());
}
_wingN->getNode("weight", true)->setFloatValue(wgt);

12
src/FDM/YASim/Wing.hpp
View file

@ -100,6 +100,9 @@ class Wing {
// valid only after Wing::compile() was called
Chord getMAC() const { return _mac; };
float getMACx() const { return _mac.x; };
float getMACy() const { return _mac.y; };
float getMACz() const { return _mac.z; };
float getArea() const { return _sectionSpan*_meanChord; };
void setDragCoefficient(float scale);
void multiplyDragCoefficient(float factor);
@ -143,8 +146,9 @@ class Wing {
static Chord _float2chord(float* pos, float lenght = 0);
//copy chord x,y,z to float[3]
static void _chord2float(Chord c, float* pos);
void interp(const float* v1, const float* v2, const float frac, float* out);
void writeInfoToProptree();
void _interp(const float* v1, const float* v2, const float frac, float* out);
void _writeInfoToProptree();
Chord _weightedMeanChord(Chord a, float wa, Chord b, float wb);
public:
Wing(Version* ver, bool mirror);
@ -153,8 +157,6 @@ public:
int addWingSection(float* base, float chord, float wingLength,
float taper = 1, float sweep = 0, float dihedral = 0, float twist = 0, float camber = 0, float idrag = 1, float incidence = 0);
static Chord calculateMAC(const Chord root, const Chord tip);
void setFlapParams(int section, WingFlaps type, FlapParams fp);
void setSectionDrag(int section, float pdrag);
void setSectionStallParams(int section, StallParams sp);
@ -184,7 +186,7 @@ public:
float getMACLength() const { return _mac.length; }; // get length of MAC
float getMACx() const { return _mac.x; }; // get x-coord of MAC leading edge
float getMACy() const { return _mac.y; }; // get y-coord of MAC leading edge
float getMACz() const { return _mac.z; }; // get y-coord of MAC leading edge
float getMACz() const { return _mac.z; }; // get z-coord of MAC leading edge
float getSweepLEMin() const { return _sweepLEMin; }; //min sweep angle of leading edge
float getSweepLEMax() const { return _sweepLEMax; }; //max sweep angle of leading edge