First take a look at this (anyway theres 3 drag areas top, front and side areas of a jet)
but lets talk about only two top view area and frontal area.
how should i calculate drag force since: drag = sin(angleofattack)*drag_force_of_firstarea + cos(angleofattack)*drag_force_of_secondarea doesn't seem to work as it should.
What angle are you using for "angleofattack?"
How are you calculating "drag_force_offirstarea?"
Please don't PM me with questions. Post them in the forums for everyone's benefit, and I can embarrass myself publicly.
You don't forget how to play when you grow old; you grow old when you forget how to play.
This is a fairly crude approach to drag force. A simpler, but equally crude, approach would be to use the area of the aircraft projected onto a plane perpendicular to the direction of motion.
How are you expecting drag to work?
I would be inclined to treat the wing and tail as two lifting surfaces and then apply some NACA Lift & Drag curves.
You could do a similar thing for the fusalage (treat it as a long-chord wing section).
I calculate drag by: drag_coefficient* ( (denisty * vecolity squared) / 2.0f) * drag_area
angleof attack is angle between model pitch and moving direction
brucedjones
Posted Yesterday, 02:51 PM
This is a fairly crude approach to drag force. A simpler, but equally crude, approach would be to use the area of the aircraft projected onto a plane perpendicular to the direction of motion.
How are you expecting drag to work?
wtf?
CombatWombat ill take a look at it.
doesn't seem to work as it should.
As a simple approach to drag, your equations appear adequate. If that doesn't "seem to work," what are you expecting (as asked above) that you're not getting?
Please don't PM me with questions. Post them in the forums for everyone's benefit, and I can embarrass myself publicly.
You don't forget how to play when you grow old; you grow old when you forget how to play.
whenever i raise my nose (even to 0.5 degree) i get massive drag that prevents me from reaching 302 knots
float AngleOfAttack = AngleBetweenVectors(vel,ThrustForce_vec);
float tmpangle = RadToDeg(AngleOfAttack);
LiftCoeff = sin(AngleOfAttack) / 2.0f;//+0.050;
DragForce_vec = reverse_point(vel); DragForce_vec = Normalize( DragForce_vec ); i_drag_force = DragForce_vec;
DragForce_vec = vector_multiple(DragForce_vec,0.080f * ((dens * squareSpeed)/2.0f) * cos(tmpangle*imopi)*3.6f); //the thrust drag force
i_drag_force = vector_multiple(i_drag_force,1.280f*((dens * squareSpeed)/2.0f)* sin(tmpangle*imopi)*38.0f);
DragForce_vec = DragForce_vec + i_drag_force;
float LiftForce = 0.50f * LiftCoeff * dens * squareSpeed * 38.0f;// <--- LIFT AREA
LiftForce_vec.x = YPRangle.AIR_MATRIX[4]; /up
LiftForce_vec.y = YPRangle.AIR_MATRIX[5];
LiftForce_vec.z = YPRangle.AIR_MATRIX[6];
LiftForce_vec = vector_multiple(LiftForce_vec, LiftForce);
result_force = GForce_vec + ThrustForce_vec + DragForce_vec + LiftForce_vec;
Assuming that you've stepped through your code, checking values at each line: in which line do you get unexpected values?
((dens * squareSpeed)/2.0f) * cos(tmpangle*imopi)*3.6f)I'm not sure what all you're variables and factors represent. However, a simple drag force would be proportional to 1/2*density*v2*area. If I understand your diagram and angles correctly, the area should be proportional to the sin(angle), not cos.
Please don't PM me with questions. Post them in the forums for everyone's benefit, and I can embarrass myself publicly.
You don't forget how to play when you grow old; you grow old when you forget how to play.
not exactly cos of 0 is 1 and second area produces then drag with full force, anyway we can close this topic for now
