112 lines
2.8 KiB
C++
112 lines
2.8 KiB
C++
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// SIS Twin Otter Iced aircraft Nonlinear model
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// Version 020409
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// read readme_020212.doc for information
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#include "uiuc_iced_nonlin.h"
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void Calc_Iced_Forces()
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{
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// alpha in deg
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double alpha;
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double de;
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double eta_ref_wing = 0.08; // eta of iced data used for curve fit
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double eta_ref_tail = 0.12;
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double eta_wing;
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//double delta_CL; // CL_clean - CL_iced;
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//double delta_CD; // CD_clean - CD_iced;
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//double delta_Cm; // CM_clean - CM_iced;
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double delta_Cm_a; // (Cm_clean - Cm_iced) as a function of AoA;
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double delta_Cm_de; // (Cm_clean - Cm_iced) as a function of de;
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double delta_Ch_a;
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double delta_Ch_e;
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double KCL;
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double KCD;
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double KCm_alpha;
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double KCm_de;
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double KCh;
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double CL_diff;
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alpha = Alpha*RAD_TO_DEG;
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de = elevator*RAD_TO_DEG;
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// lift fits
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if (alpha < 16)
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{
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delta_CL = (0.088449 + 0.004836*alpha - 0.0005459*alpha*alpha +
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4.0859e-5*pow(alpha,3));
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}
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else
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{
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delta_CL = (-11.838 + 1.6861*alpha - 0.076707*alpha*alpha +
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0.001142*pow(alpha,3));
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}
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KCL = -delta_CL/eta_ref_wing;
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eta_wing = 0.5*(eta_wing_left + eta_wing_right);
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delta_CL = eta_wing*KCL;
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// drag fit
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delta_CD = (-0.0089 + 0.001578*alpha - 0.00046253*pow(alpha,2) +
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-4.7511e-5*pow(alpha,3) + 2.3384e-6*pow(alpha,4));
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KCD = -delta_CD/eta_ref_wing;
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delta_CD = eta_wing*KCD;
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// pitching moment fit
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delta_Cm_a = (-0.01892 - 0.0056476*alpha + 1.0205e-5*pow(alpha,2)
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- 4.0692e-5*pow(alpha,3) + 1.7594e-6*pow(alpha,4));
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delta_Cm_de = (-0.014928 - 0.0037783*alpha + 0.00039086*pow(de,2)
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- 1.1304e-5*pow(de,3) - 1.8439e-6*pow(de,4));
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delta_Cm = delta_Cm_a + delta_Cm_de;
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KCm_alpha = delta_Cm_a/eta_ref_wing;
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KCm_de = delta_Cm_de/eta_ref_tail;
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delta_Cm = (0.75*eta_wing + 0.25*eta_tail)*KCm_alpha + (eta_tail)*KCm_de;
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// hinge moment
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if (alpha < 13)
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{
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delta_Ch_a = (-0.0012862 - 0.00022705*alpha + 1.5911e-5*pow(alpha,2)
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+ 5.4536e-7*pow(alpha,3));
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}
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else
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{
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delta_Ch_a = 0;
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}
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delta_Ch_e = -0.0011851 - 0.00049924*de;
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delta_Ch = -(delta_Ch_a + delta_Ch_e);
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KCh = -delta_Ch/eta_ref_tail;
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delta_Ch = eta_tail*KCh;
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// rolling moment
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CL_diff = (eta_wing_left - eta_wing_right)*KCL;
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delta_Cl = CL_diff/4;
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}
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void add_ice_effects()
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{
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CL_clean = -1*CZ*cos(Alpha) + CX*sin(Alpha); //Check later
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CD_clean = -1*CZ*sin(Alpha) - CX*cos(Alpha);
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Cm_clean = Cm;
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Cl_clean = Cl;
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Ch_clean = Ch;
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CL_iced = CL_clean + delta_CL;
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CD_iced = CD_clean + delta_CD;
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Cm_iced = Cm_clean + delta_Cm;
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Cl_iced = Cl_clean + delta_Cl;
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//Ch_iced = Ch_clean + delta_Ch;
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CL = CL_iced;
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CD = CD_iced;
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Cm = Cm_iced;
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Cl = Cl_iced;
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//Ch = Ch_iced;
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CZ = -1*CL*cos(Alpha) - CD*sin(Alpha);
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CX = CL*sin(Alpha) - CD*cos(Alpha);
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}
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