src/FDM/UIUCModel/uiuc_iced_nonlin.cpp

   1 //     SIS Twin Otter Iced aircraft Nonlinear model\r
   2 //     Version 020409\r
   3 //     read readme_020212.doc for information\r
   4 \r
   5 #include "uiuc_iced_nonlin.h"\r
   6 \r
   7 void Calc_Iced_Forces()\r
   8         {\r
   9         // alpha in deg\r
  10           double alpha;\r
  11           double de;\r
  12         double eta_ref_wing = 0.08;                      // eta of iced data used for curve fit\r
  13         double eta_ref_tail = 0.12;\r
  14         double eta_wing;\r
  15         //double delta_CL;                              // CL_clean - CL_iced;\r
  16         //double delta_CD;                              // CD_clean - CD_iced;\r
  17         //double delta_Cm;                              // CM_clean - CM_iced;\r
  18         double delta_Cm_a;                              // (Cm_clean - Cm_iced) as a function of AoA;\r
  19         double delta_Cm_de;                             // (Cm_clean - Cm_iced) as a function of de;\r
  20         double delta_Ch_a;\r
  21         double delta_Ch_e;\r
  22         double KCL;\r
  23         double KCD;\r
  24         double KCm_alpha;\r
  25         double KCm_de;\r
  26         double KCh;\r
  27         double CL_diff;\r
  28         \r
  29         \r
  30         \r
  31         alpha = Alpha*RAD_TO_DEG;\r
  32         de = elevator*RAD_TO_DEG;\r
  33         // lift fits\r
  34         if (alpha < 16)\r
  35                 {\r
  36                 delta_CL = (0.088449 + 0.004836*alpha - 0.0005459*alpha*alpha +\r
  37                                         4.0859e-5*pow(alpha,3));\r
  38                 }\r
  39         else\r
  40                 {\r
  41                 delta_CL = (-11.838 + 1.6861*alpha - 0.076707*alpha*alpha +\r
  42                                         0.001142*pow(alpha,3));\r
  43                 }\r
  44         KCL = -delta_CL/eta_ref_wing;\r
  45         eta_wing = 0.5*(eta_wing_left + eta_wing_right);\r
  46         delta_CL = eta_wing*KCL;\r
  47         \r
  48                 \r
  49         // drag fit\r
  50         delta_CD = (-0.0089 + 0.001578*alpha - 0.00046253*pow(alpha,2) +\r
  51                                         -4.7511e-5*pow(alpha,3) + 2.3384e-6*pow(alpha,4));\r
  52         KCD = -delta_CD/eta_ref_wing;\r
  53         delta_CD = eta_wing*KCD;\r
  54         \r
  55         // pitching moment fit\r
  56         delta_Cm_a = (-0.01892 - 0.0056476*alpha + 1.0205e-5*pow(alpha,2)\r
  57                       - 4.0692e-5*pow(alpha,3) + 1.7594e-6*pow(alpha,4));\r
  58                                         \r
  59         delta_Cm_de = (-0.014928 - 0.0037783*alpha + 0.00039086*pow(de,2)\r
  60                                         - 1.1304e-5*pow(de,3) - 1.8439e-6*pow(de,4));\r
  61                                         \r
  62         delta_Cm = delta_Cm_a + delta_Cm_de;\r
  63         KCm_alpha = delta_Cm_a/eta_ref_wing;\r
  64         KCm_de = delta_Cm_de/eta_ref_tail;\r
  65         delta_Cm = (0.75*eta_wing + 0.25*eta_tail)*KCm_alpha + (eta_tail)*KCm_de;\r
  66         \r
  67         // hinge moment\r
  68         if (alpha < 13)\r
  69                 {\r
  70                 delta_Ch_a = (-0.0012862 - 0.00022705*alpha + 1.5911e-5*pow(alpha,2)\r
  71                                                 + 5.4536e-7*pow(alpha,3));\r
  72                 }\r
  73         else\r
  74                 {\r
  75                 delta_Ch_a = 0;\r
  76                 }\r
  77         delta_Ch_e = -0.0011851 - 0.00049924*de;\r
  78         delta_Ch = -(delta_Ch_a + delta_Ch_e);\r
  79         KCh = -delta_Ch/eta_ref_tail;\r
  80         delta_Ch = eta_tail*KCh;\r
  81         \r
  82         // rolling moment\r
  83         CL_diff = (eta_wing_left - eta_wing_right)*KCL;\r
  84         delta_Cl = CL_diff/4;\r
  85         \r
  86         }\r
  87 \r
  88 void add_ice_effects()\r
  89 {\r
  90   CL_clean = -1*CZ*cos(Alpha) + CX*sin(Alpha);  //Check later\r
  91   CD_clean = -1*CZ*sin(Alpha) - CX*cos(Alpha);\r
  92   Cm_clean = Cm;\r
  93   Cl_clean = Cl;\r
  94   Ch_clean = Ch;\r
  95 \r
  96   CL_iced = CL_clean + delta_CL;\r
  97   CD_iced = CD_clean + delta_CD;\r
  98   Cm_iced = Cm_clean + delta_Cm;\r
  99   Cl_iced = Cl_clean + delta_Cl;\r
 100   //Ch_iced = Ch_clean + delta_Ch;\r
 101 \r
 102   CL = CL_iced;\r
 103   CD = CD_iced;\r
 104   Cm = Cm_iced;\r
 105   Cl = Cl_iced;\r
 106   //Ch = Ch_iced;\r
 107 \r
 108   CZ = -1*CL*cos(Alpha) - CD*sin(Alpha);\r
 109   CX = CL*sin(Alpha) - CD*cos(Alpha);\r
 110 \r
 111 }\r