step/stepcore

coulombforce.cc

00001 /* This file is part of StepCore library.
00002    Copyright (C) 2007 Vladimir Kuznetsov <ks.vladimir@gmail.com>
00003 
00004    StepCore library is free software; you can redistribute it and/or modify
00005    it under the terms of the GNU General Public License as published by
00006    the Free Software Foundation; either version 2 of the License, or
00007    (at your option) any later version.
00008 
00009    StepCore library is distributed in the hope that it will be useful,
00010    but WITHOUT ANY WARRANTY; without even the implied warranty of
00011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00012    GNU General Public License for more details.
00013 
00014    You should have received a copy of the GNU General Public License
00015    along with StepCore; if not, write to the Free Software
00016    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
00017 */
00018 
00019 #include "coulombforce.h"
00020 #include "particle.h"
00021 
00022 #include <cmath>
00023 
00024 namespace StepCore {
00025 
00026 STEPCORE_META_OBJECT(CoulombForce, "Coulomb force", 0,
00027     STEPCORE_SUPER_CLASS(Item) STEPCORE_SUPER_CLASS(Force),
00028     STEPCORE_PROPERTY_RW(double, coulombConst, STEPCORE_FROM_UTF8("N m²/C²"),
00029                 "Coulomb constant", coulombConst, setCoulombConst))
00030 
00031 STEPCORE_META_OBJECT(CoulombForceErrors, "Errors class for CoulombForce", 0,
00032     STEPCORE_SUPER_CLASS(ObjectErrors),
00033     STEPCORE_PROPERTY_RW(double, coulombConstVariance, STEPCORE_FROM_UTF8("N m²/C²"),
00034                 "Coulomb constant variance", coulombConstVariance, setCoulombConstVariance))
00035 
00036 CoulombForce* CoulombForceErrors::coulombForce() const
00037 {
00038     return static_cast<CoulombForce*>(owner());
00039 }
00040 
00041 CoulombForce::CoulombForce(double coulombConst)
00042     : _coulombConst(coulombConst)
00043 {
00044     coulombForceErrors()->setCoulombConstVariance(
00045         square(Constants::CoulombError));
00046 }
00047 
00048 void CoulombForce::calcForce(bool calcVariances)
00049 {
00050     const BodyList::const_iterator end = world()->bodies().end(); 
00051     for(BodyList::const_iterator b1 = world()->bodies().begin(); b1 != end; ++b1) {
00052         if(!(*b1)->metaObject()->inherits<ChargedParticle>()) continue;
00053         for(BodyList::const_iterator b2 = b1+1; b2 != end; ++b2) {
00054             if(!(*b2)->metaObject()->inherits<ChargedParticle>()) continue;
00055             ChargedParticle* p1 = static_cast<ChargedParticle*>(*b1);
00056             ChargedParticle* p2 = static_cast<ChargedParticle*>(*b2);
00057 
00058             Vector2d r = p2->position() - p1->position();
00059             double rnorm2 = r.norm2();
00060             Vector2d force = _coulombConst* p1->charge() * p2->charge() * r / (rnorm2*sqrt(rnorm2));
00061             p2->applyForce(force);
00062             force.invert();
00063             p1->applyForce(force);
00064 
00065             if(calcVariances) {
00066                 // XXX: CHECKME
00067                 ChargedParticleErrors* pe1 = p1->chargedParticleErrors();
00068                 ChargedParticleErrors* pe2 = p2->chargedParticleErrors();
00069                 Vector2d rV = pe2->positionVariance() + pe1->positionVariance();
00070                 Vector2d forceV = force.cSquare().cMultiply(
00071                         Vector2d(coulombForceErrors()->_coulombConstVariance / square(_coulombConst) +
00072                                  pe1->chargeVariance() / square(p1->charge()) +
00073                                  pe2->chargeVariance() / square(p2->charge())) +
00074                         Vector2d(rV[0] * square(1/r[0] - 3*r[0]/rnorm2) + rV[1] * square(3*r[1]/rnorm2),
00075                                  rV[1] * square(1/r[1] - 3*r[1]/rnorm2) + rV[0] * square(3*r[0]/rnorm2)));
00076                 pe1->applyForceVariance(forceV);
00077                 pe2->applyForceVariance(forceV);
00078             }
00079         }
00080     }
00081 }
00082 
00083 } // namespace StepCore
00084
step/stepcore

coulombforce.cc

step/stepcore

kdeedu
