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flightgear/src/FDM/LaRCsim/basic_aero.c

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/***************************************************************************
TITLE: basic_aero
----------------------------------------------------------------------------
FUNCTION: aerodynamics model based on stability derivatives
+ tweaks for nonlinear aero
----------------------------------------------------------------------------
MODULE STATUS: developmental
----------------------------------------------------------------------------
GENEALOGY: based on aero model from crrcsim code (Drela's aero model)
----------------------------------------------------------------------------
DESIGNED BY:
CODED BY: Michael Selig
MAINTAINED BY: Michael Selig
----------------------------------------------------------------------------
MODIFICATION HISTORY:
DATE PURPOSE BY
7/25/03 LaRCsim debugging purposes
----------------------------------------------------------------------------
REFERENCES:
----------------------------------------------------------------------------
CALLED BY:
----------------------------------------------------------------------------
CALLS TO:
----------------------------------------------------------------------------
INPUTS:
----------------------------------------------------------------------------
OUTPUTS:
--------------------------------------------------------------------------*/
#include "ls_generic.h"
#include "ls_cockpit.h"
#include "ls_constants.h"
#include "ls_types.h"
#include "basic_aero.h"
#include <math.h>
#include <stdio.h>
#ifdef USENZ
#define NZ generic_.n_cg_body_v[2]
#else
#define NZ 1
#endif
extern COCKPIT cockpit_;
void basic_aero(SCALAR dt, int Initialize)
// Calculate forces and moments for the current time step. If Initialize is
// zero, then re-initialize coefficients by reading in the coefficient file.
{
static int init = 0;
static SCALAR elevator_drela, aileron_drela, rudder_drela;
SCALAR C_ref;
SCALAR B_ref;
SCALAR S_ref;
SCALAR U_ref;
/* SCALAR Mass; */
/* SCALAR I_xx; */
/* SCALAR I_yy; */
/* SCALAR I_zz; */
/* SCALAR I_xz; */
SCALAR Alpha_0;
SCALAR Cm_0;
SCALAR CL_0;
SCALAR CL_max;
SCALAR CL_min;
SCALAR CD_prof;
SCALAR Uexp_CD;
SCALAR CL_a;
SCALAR Cm_a;
SCALAR CY_b;
SCALAR Cl_b;
SCALAR Cn_b;
SCALAR CL_q;
SCALAR Cm_q;
SCALAR CY_p;
SCALAR Cl_p;
SCALAR Cn_p;
SCALAR CY_r;
SCALAR Cl_r;
SCALAR Cn_r;
SCALAR CL_de;
SCALAR Cm_de;
SCALAR CY_dr;
SCALAR Cl_dr;
SCALAR Cn_dr;
SCALAR CY_da;
SCALAR Cl_da;
SCALAR Cn_da;
SCALAR eta_loc;
SCALAR CG_arm;
SCALAR CL_drop;
SCALAR CD_stall = 0.05;
int stalling;
SCALAR span_eff;
SCALAR CL_CD0;
SCALAR CD_CLsq;
SCALAR CD_AIsq;
SCALAR CD_ELsq;
SCALAR Phat, Qhat, Rhat; // dimensionless rotation rates
SCALAR CL_left, CL_cent, CL_right; // CL values across the span
SCALAR dCL_left,dCL_cent,dCL_right; // stall-induced CL changes
SCALAR dCD_left,dCD_cent,dCD_right; // stall-induced CD changes
SCALAR dCl,dCn,dCl_stall,dCn_stall; // stall-induced roll,yaw moments
SCALAR dCm_stall; // Stall induced pitching moment.
SCALAR CL_wing, CD_all, CD_scaled, Cl_w;
SCALAR Cl_r_mod,Cn_p_mod;
SCALAR CL_drela,CD_drela,Cx_drela,Cy_drela,Cz_drela,Cl_drela,Cm_drela,Cn_drela;
SCALAR QS;
SCALAR G_11,G_12,G_13;
SCALAR G_21,G_22,G_23;
SCALAR G_31,G_32,G_33;
SCALAR U_body_X,U_body_Y,U_body_Z;
SCALAR V_body_X,V_body_Y,V_body_Z;
SCALAR W_body_X,W_body_Y,W_body_Z;
SCALAR P_atmo,Q_atmo,R_atmo;
// set the parameters
C_ref = 0.551667;
B_ref = 6.55000;
S_ref = 3.61111;
U_ref = 19.6850;
Alpha_0 = 0.349066E-01;
Cm_0 = -0.112663E-01;
CL_0 = 0.563172;
CL_max = 1.10000;
CL_min = -0.600000;
CD_prof = 0.200000E-01;
Uexp_CD = -0.500000;
CL_a = 5.50360;
Cm_a = -0.575335;
CY_b = -0.415610;
Cl_b = -0.250926;
Cn_b = 0.567069E-01;
CL_q = 7.50999;
Cm_q = -11.4975;
CY_p = -0.423820;
Cl_p = -0.611798;
Cn_p = -0.740898E-01;
CY_r = 0.297540;
Cl_r = 0.139581;
Cn_r = -0.687755E-01;
CL_de = 0.162000;
Cm_de = -0.597537;
CY_dr = 0.000000E+00;
Cl_dr = 0.000000E+00;
Cn_dr = 0.000000E+00;
CY_da = -0.135890;
Cl_da = -0.307921E-02;
Cn_da = 0.527143E-01;
span_eff = 0.95;
CL_CD0 = 0.0;
CD_CLsq = 0.01;
CD_AIsq = 0.0;
CD_ELsq = 0.0;
eta_loc = 0.3;
CG_arm = 0.25;
CL_drop = 0.5;
if (!init)
{
init = -1;
}
// jan's data goes -.5 to .5 while
// fgfs data goes +- 1.
// so I need to divide by 2 below.
elevator = Long_control + Long_trim;
aileron = Lat_control;
rudder = Rudder_pedal;
elevator = elevator * 0.5;
aileron = aileron * 0.5;
rudder = rudder * 0.5;
// printf("%f\n",V_rel_wind);
/* compute gradients of Local velocities w.r.t. Body coordinates
G_11 = dU_local/dx_body
G_12 = dU_local/dy_body etc. */
/*
G_11 = U_atmo_X*T_local_to_body_11
+ U_atmo_Y*T_local_to_body_12
+ U_atmo_Z*T_local_to_body_13;
G_12 = U_atmo_X*T_local_to_body_21
+ U_atmo_Y*T_local_to_body_22
+ U_atmo_Z*T_local_to_body_23;
G_13 = U_atmo_X*T_local_to_body_31
+ U_atmo_Y*T_local_to_body_32
+ U_atmo_Z*T_local_to_body_33;
G_21 = V_atmo_X*T_local_to_body_11
+ V_atmo_Y*T_local_to_body_12
+ V_atmo_Z*T_local_to_body_13;
G_22 = V_atmo_X*T_local_to_body_21
+ V_atmo_Y*T_local_to_body_22
+ V_atmo_Z*T_local_to_body_23;
G_23 = V_atmo_X*T_local_to_body_31
+ V_atmo_Y*T_local_to_body_32
+ V_atmo_Z*T_local_to_body_33;
G_31 = W_atmo_X*T_local_to_body_11
+ W_atmo_Y*T_local_to_body_12
+ W_atmo_Z*T_local_to_body_13;
G_32 = W_atmo_X*T_local_to_body_21
+ W_atmo_Y*T_local_to_body_22
+ W_atmo_Z*T_local_to_body_23;
G_33 = W_atmo_X*T_local_to_body_31
+ W_atmo_Y*T_local_to_body_32
+ W_atmo_Z*T_local_to_body_33;
*/
//printf("%f %f %f %f\n",W_atmo_X,W_atmo_Y,G_31,G_32);
/* now compute gradients of Body velocities w.r.t. Body coordinates */
/* U_body_x = dU_body/dx_body etc. */
/*
U_body_X = T_local_to_body_11*G_11
+ T_local_to_body_12*G_21
+ T_local_to_body_13*G_31;
U_body_Y = T_local_to_body_11*G_12
+ T_local_to_body_12*G_22
+ T_local_to_body_13*G_32;
U_body_Z = T_local_to_body_11*G_13
+ T_local_to_body_12*G_23
+ T_local_to_body_13*G_33;
V_body_X = T_local_to_body_21*G_11
+ T_local_to_body_22*G_21
+ T_local_to_body_23*G_31;
V_body_Y = T_local_to_body_21*G_12
+ T_local_to_body_22*G_22
+ T_local_to_body_23*G_32;
V_body_Z = T_local_to_body_21*G_13
+ T_local_to_body_22*G_23
+ T_local_to_body_23*G_33;
W_body_X = T_local_to_body_31*G_11
+ T_local_to_body_32*G_21
+ T_local_to_body_33*G_31;
W_body_Y = T_local_to_body_31*G_12
+ T_local_to_body_32*G_22
+ T_local_to_body_33*G_32;
W_body_Z = T_local_to_body_31*G_13
+ T_local_to_body_32*G_23
+ T_local_to_body_33*G_33;
*/
/* set rotation rates of airmass motion */
/* BUG
P_atmo = W_body_X;
Q_atmo = -W_body_Y;
R_atmo = V_body_Z;
*/
/*
P_atmo = W_body_Y;
Q_atmo = -W_body_X;
R_atmo = V_body_X;
*/
P_atmo = 0;
Q_atmo = 0;
R_atmo = 0;
// printf("%f %f %f\n",P_atmo,Q_atmo,R_atmo);
if (V_rel_wind != 0)
{
/* set net effective dimensionless rotation rates */
Phat = (P_body - P_atmo) * B_ref / (2.0*V_rel_wind);
Qhat = (Q_body - Q_atmo) * C_ref / (2.0*V_rel_wind);
Rhat = (R_body - R_atmo) * B_ref / (2.0*V_rel_wind);
}
else
{
Phat=0;
Qhat=0;
Rhat=0;
}
// printf("Phat: %f Qhat: %f Rhat: %f\n",Phat,Qhat,Rhat);
/* compute local CL at three spanwise locations */
CL_left = CL_0 + CL_a*(Std_Alpha - Alpha_0 - Phat*eta_loc);
CL_cent = CL_0 + CL_a*(Std_Alpha - Alpha_0 );
CL_right = CL_0 + CL_a*(Std_Alpha - Alpha_0 + Phat*eta_loc);
// printf("CL_left: %f CL_cent: %f CL_right: %f\n",CL_left,CL_cent,CL_right);
/* set CL-limit changes */
dCL_left = 0.;
dCL_cent = 0.;
dCL_right = 0.;
stalling=0;
if (CL_left > CL_max)
{
dCL_left = CL_max-CL_left -CL_drop;
stalling=1;
}
if (CL_cent > CL_max)
{
dCL_cent = CL_max-CL_cent -CL_drop;
stalling=1;
}
if (CL_right > CL_max)
{
dCL_right = CL_max-CL_right -CL_drop;
stalling=1;
}
if (CL_left < CL_min)
{
dCL_left = CL_min-CL_left -CL_drop;
stalling=1;
}
if (CL_cent < CL_min)
{
dCL_cent = CL_min-CL_cent -CL_drop;
stalling=1;
}
if (CL_right < CL_min)
{
dCL_right = CL_min-CL_right -CL_drop;
stalling=1;
}
/* set average wing CL */
CL_wing = CL_0 + CL_a*(Std_Alpha-Alpha_0)
+ 0.25*dCL_left + 0.5*dCL_cent + 0.25*dCL_right;
// printf("CL_wing: %f\n",CL_wing);
/* correct profile CD for CL dependence and aileron dependence */
CD_all = CD_prof
+ CD_CLsq*(CL_wing-CL_CD0)*(CL_wing-CL_CD0)
+ CD_AIsq*aileron*aileron
+ CD_ELsq*elevator*elevator;
// printf("CD_all:%lf\n",CD_all);
/* scale profile CD with Reynolds number via simple power law */
if (V_rel_wind > 0.1)
{
CD_scaled = CD_all*pow(((double)V_rel_wind/(double)U_ref),Uexp_CD);
}
else
{
CD_scaled=CD_all;
}
// printf("CD_scaled:%lf\n",CD_scaled);
/* Scale lateral cross-coupling derivatives with wing CL */
Cl_r_mod = Cl_r*CL_wing/CL_0;
Cn_p_mod = Cn_p*CL_wing/CL_0;
// printf("Cl_r_mod: %f Cn_p_mod: %f\n",Cl_r_mod,Cn_p_mod);
/* total average CD with induced and stall contributions */
dCD_left = CD_stall*dCL_left *dCL_left ;
dCD_cent = CD_stall*dCL_cent *dCL_cent ;
dCD_right = CD_stall*dCL_right*dCL_right;
/* total CL, with pitch rate and elevator contributions */
CL_drela = (CL_wing + CL_q*Qhat + CL_de*elevator)*Cos_alpha;
// printf("CL:%f\n",CL);
/* assymetric stall will cause roll and yaw moments */
dCl = 0.45*-1*(dCL_right-dCL_left)*0.5*eta_loc;
dCn = 0.45*(dCD_right-dCD_left)*0.5*eta_loc;
dCm_stall = (0.25*dCL_left + 0.5*dCL_cent + 0.25*dCL_right)*CG_arm;
// printf("dCl: %f dCn:%f\n",dCl,dCn);
/* stall-caused moments in body axes */
dCl_stall = dCl*Cos_alpha - dCn*Sin_alpha;
dCn_stall = dCl*Sin_alpha + dCn*Cos_alpha;
/* total CD, with induced and stall contributions */
Cl_w = Cl_b*Std_Beta + Cl_p*Phat + Cl_r_mod*Rhat
+ dCl_stall + Cl_da*aileron;
CD_drela = CD_scaled
+ (CL*CL + 32.0*Cl_w*Cl_w)*S_ref/(B_ref*B_ref*3.14159*span_eff)
+ 0.25*dCD_left + 0.5*dCD_cent + 0.25*dCD_right;
//printf("CL: %f CD:%f L/D:%f\n",CL,CD,CL/CD);
/* total forces in body axes */
Cx_drela = -CD_drela*Cos_alpha + CL_drela*Sin_alpha*Cos_beta*Cos_beta;
Cz_drela = -CD_drela*Sin_alpha - CL_drela*Cos_alpha*Cos_beta*Cos_beta;
Cy_drela = CY_b*Std_Beta + CY_p*Phat + CY_r*Rhat + CY_dr*rudder;
/* total moments in body axes */
Cl_drela = Cl_b*Std_Beta + Cl_p*Phat + Cl_r_mod*Rhat + Cl_dr*rudder
+ dCl_stall + Cl_da*aileron;
Cn_drela = Cn_b*Std_Beta + Cn_p_mod*Phat + Cn_r*Rhat + Cn_dr*rudder
+ dCn_stall + Cn_da*aileron;
Cm_drela = Cm_0 + Cm_a*(Std_Alpha-Alpha_0) +dCm_stall
+ Cm_q*Qhat + Cm_de*elevator;
/* set dimensional forces and moments */
QS = 0.5*Density*V_rel_wind*V_rel_wind * S_ref;
F_X_aero = Cx_drela * QS;
F_Y_aero = Cy_drela * QS;
F_Z_aero = Cz_drela * QS;
M_l_aero = Cl_drela * QS * B_ref;
M_m_aero = Cm_drela * QS * C_ref;
M_n_aero = Cn_drela * QS * B_ref;
// printf("%f %f %f %f %f %f\n",F_X_aero,F_Y_aero,F_Z_aero,M_l_aero,M_m_aero,M_n_aero);
}
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