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 "cells": [
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Wing–Fuselage Configuration with OpenVSP\n",
    "## Level: Intermediate\n",
    "\n",
    "This notebook demonstrates how to build a wing–fuselage aircraft configuration\n",
    "using the OpenVSP Python API and perform a panel aerodynamic analysis with VSPAero.\n",
    "\n",
    "### Topics covered\n",
    "- OpenVSP geometry creation via Python API\n",
    "- Wing and fuselage parametric modeling\n",
    "- VSPAero VLM (Vortex Lattice Method) analysis setup\n",
    "- Aerodynamic coefficient extraction: CL, CDi, Cm\n",
    "- Effect of fuselage on wing aerodynamics\n",
    "\n",
    "### Requirements\n",
    "- `openvsp` package installed (see https://openvsp.org)\n",
    "- If OpenVSP is not installed, this notebook will use a mock/fallback mode\n",
    "\n",
    "### References\n",
    "- OpenVSP Python API docs: https://openvsp.org/pyapi_docs/latest/\n",
    "- Raymer, D.P., *Aircraft Design: A Conceptual Approach*, AIAA, 2018"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import numpy as np\n",
    "import matplotlib.pyplot as plt\n",
    "import sys, os\n",
    "sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath('.')), 'src'))\n",
    "\n",
    "from aerodemo.openvsp_utils import (\n",
    "    check_openvsp, init_vsp, add_wing, add_fuselage, run_vspaero\n",
    ")\n",
    "from aerodemo.vlm import WingGeometry, VortexLatticeMethod\n",
    "\n",
    "HAS_VSP = check_openvsp()\n",
    "print(f\"OpenVSP available: {HAS_VSP}\")\n",
    "if not HAS_VSP:\n",
    "    print(\"NOTE: OpenVSP not found. Using VLM fallback for aerodynamic analysis.\")\n",
    "    print(\"Install OpenVSP with: pip install openvsp\")\n",
    "\n",
    "plt.rcParams.update({'figure.dpi': 100, 'axes.grid': True, 'grid.alpha': 0.3, 'font.size': 11})"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 1. Aircraft Configuration Parameters\n",
    "\n",
    "We design a simple low-wing transport aircraft:\n",
    "\n",
    "| Component | Parameter | Value |\n",
    "|-----------|-----------|-------|\n",
    "| Wing | Span | 28 m |\n",
    "| Wing | Root chord | 4.5 m |\n",
    "| Wing | Tip chord | 1.8 m |\n",
    "| Wing | Sweep (c/4) | 20° |\n",
    "| Wing | Dihedral | 5° |\n",
    "| Fuselage | Length | 30 m |\n",
    "| Fuselage | Max diameter | 3.2 m |"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Aircraft configuration parameters\n",
    "config = {\n",
    "    # Wing\n",
    "    'wing_span': 28.0,\n",
    "    'wing_root_chord': 4.5,\n",
    "    'wing_tip_chord': 1.8,\n",
    "    'wing_sweep': 20.0,\n",
    "    'wing_dihedral': 5.0,\n",
    "    'wing_x_offset': 10.0,\n",
    "    'wing_z_offset': -1.2,\n",
    "    # Fuselage\n",
    "    'fuse_length': 30.0,\n",
    "    'fuse_diameter': 3.2,\n",
    "}\n",
    "\n",
    "# Derived parameters\n",
    "S_ref = config['wing_span'] * (config['wing_root_chord'] + config['wing_tip_chord']) / 2\n",
    "AR = config['wing_span']**2 / S_ref\n",
    "lam = config['wing_tip_chord'] / config['wing_root_chord']\n",
    "MAC = (2/3) * config['wing_root_chord'] * (1 + lam + lam**2) / (1 + lam)\n",
    "\n",
    "print(\"Wing-Fuselage Configuration:\")\n",
    "print(f\"  Wing span:            b = {config['wing_span']:.1f} m\")\n",
    "print(f\"  Reference area:       S = {S_ref:.2f} m²\")\n",
    "print(f\"  Aspect ratio:        AR = {AR:.2f}\")\n",
    "print(f\"  Taper ratio:          λ = {lam:.3f}\")\n",
    "print(f\"  MAC:                  c̄ = {MAC:.3f} m\")\n",
    "print(f\"  Fuselage length:      L = {config['fuse_length']:.1f} m\")\n",
    "print(f\"  Fuselage diameter:    D = {config['fuse_diameter']:.1f} m\")\n",
    "print(f\"  Fineness ratio:     L/D = {config['fuse_length']/config['fuse_diameter']:.2f}\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 2. OpenVSP Model Creation\n",
    "\n",
    "We create the wing and fuselage geometry in OpenVSP.\n",
    "If OpenVSP is installed, the geometry is built programmatically.\n",
    "Otherwise, we proceed with the VLM analysis."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "if HAS_VSP:\n",
    "    # Initialize fresh model\n",
    "    init_vsp(\"WingFuselage\")\n",
    "\n",
    "    # Add fuselage\n",
    "    fuse_id = add_fuselage(\n",
    "        length=config['fuse_length'],\n",
    "        max_diameter=config['fuse_diameter'],\n",
    "        name=\"Fuselage\"\n",
    "    )\n",
    "    print(f\"Fuselage geometry ID: {fuse_id}\")\n",
    "\n",
    "    # Add wing\n",
    "    wing_id = add_wing(\n",
    "        span=config['wing_span'],\n",
    "        root_chord=config['wing_root_chord'],\n",
    "        tip_chord=config['wing_tip_chord'],\n",
    "        sweep_deg=config['wing_sweep'],\n",
    "        dihedral_deg=config['wing_dihedral'],\n",
    "        x_offset=config['wing_x_offset'],\n",
    "        z_offset=config['wing_z_offset'],\n",
    "        name=\"Wing\"\n",
    "    )\n",
    "    print(f\"Wing geometry ID: {wing_id}\")\n",
    "    print(\"VSP model created successfully.\")\n",
    "else:\n",
    "    print(\"Skipping VSP model creation (OpenVSP not available).\")\n",
    "    print(\"Using VLM analysis as fallback.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 3. Aerodynamic Analysis\n",
    "\n",
    "### VSPAero (if OpenVSP available)\n",
    "VSPAero performs a Vortex Lattice analysis on the full 3D geometry.\n",
    "\n",
    "### VLM fallback\n",
    "Our custom VLM solver provides equivalent results for isolated wing analysis."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "alpha_range = np.linspace(-4, 14, 10)\n",
    "\n",
    "if HAS_VSP:\n",
    "    print(\"Running VSPAero VLM sweep...\")\n",
    "    vsp_results = run_vspaero(\n",
    "        alpha_start=-4.0,\n",
    "        alpha_end=14.0,\n",
    "        alpha_npts=10,\n",
    "        mach=0.2,\n",
    "        ref_area=S_ref,\n",
    "        ref_span=config['wing_span'],\n",
    "        ref_chord=MAC,\n",
    "    )\n",
    "    if vsp_results:\n",
    "        alpha_data = np.array(vsp_results['Alpha'])\n",
    "        CL_data = np.array(vsp_results['CL'])\n",
    "        CDi_data = np.array(vsp_results['CDi'])\n",
    "        Cm_data = np.array(vsp_results.get('Cm', [0]*len(alpha_data)))\n",
    "        analysis_label = 'VSPAero VLM'\n",
    "    else:\n",
    "        vsp_results = None\n",
    "        print(\"VSPAero returned no results. Falling back to VLM.\")\n",
    "        HAS_VSP = False\n",
    "\n",
    "if not HAS_VSP or vsp_results is None:\n",
    "    # VLM fallback\n",
    "    wing_geom = WingGeometry(\n",
    "        span=config['wing_span'],\n",
    "        root_chord=config['wing_root_chord'],\n",
    "        tip_chord=config['wing_tip_chord'],\n",
    "        sweep_angle=config['wing_sweep'],\n",
    "        dihedral=config['wing_dihedral'],\n",
    "        n_spanwise=14,\n",
    "        n_chordwise=5,\n",
    "    )\n",
    "    vlm_solver = VortexLatticeMethod(wing_geom)\n",
    "    sweep = vlm_solver.sweep_alpha(alpha_range)\n",
    "    alpha_data = sweep['alpha']\n",
    "    CL_data = sweep['CL']\n",
    "    CDi_data = sweep['CDi']\n",
    "    Cm_data = np.zeros_like(CL_data)\n",
    "    analysis_label = 'VLM (fallback)'\n",
    "\n",
    "print(f\"Analysis complete using: {analysis_label}\")\n",
    "print(f\"\\nResults at α=4°:\")\n",
    "idx = np.argmin(np.abs(alpha_data - 4.0))\n",
    "print(f\"  CL  = {CL_data[idx]:.4f}\")\n",
    "print(f\"  CDi = {CDi_data[idx]:.4f}\")\n",
    "print(f\"  L/D = {CL_data[idx]/max(CDi_data[idx], 1e-6):.1f}\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "fig, axes = plt.subplots(1, 3, figsize=(15, 5))\n",
    "\n",
    "ax = axes[0]\n",
    "ax.plot(alpha_data, CL_data, 'bo-', linewidth=2, markersize=7, label=analysis_label)\n",
    "ax.axhline(0, color='k', linewidth=0.5)\n",
    "ax.axvline(0, color='k', linewidth=0.5)\n",
    "ax.set_xlabel('α [deg]')\n",
    "ax.set_ylabel('$C_L$')\n",
    "ax.set_title('Lift Curve', fontweight='bold')\n",
    "ax.legend()\n",
    "\n",
    "ax = axes[1]\n",
    "ax.plot(CDi_data, CL_data, 'rs-', linewidth=2, markersize=7, label=analysis_label)\n",
    "ax.set_xlabel('$C_{Di}$')\n",
    "ax.set_ylabel('$C_L$')\n",
    "ax.set_title('Drag Polar', fontweight='bold')\n",
    "ax.legend()\n",
    "\n",
    "ax = axes[2]\n",
    "LD = CL_data / np.maximum(CDi_data, 1e-8)\n",
    "ax.plot(alpha_data, LD, 'gD-', linewidth=2, markersize=7)\n",
    "ax.set_xlabel('α [deg]')\n",
    "ax.set_ylabel('$C_L / C_{Di}$')\n",
    "ax.set_title('Aerodynamic Efficiency', fontweight='bold')\n",
    "\n",
    "plt.suptitle(f'Wing–Fuselage Configuration — {analysis_label}', fontsize=13, fontweight='bold')\n",
    "plt.tight_layout()\n",
    "plt.savefig('wing_fuselage_aero.png', bbox_inches='tight', dpi=100)\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 4. Summary\n",
    "\n",
    "In this notebook we have:\n",
    "1. Defined a wing–fuselage configuration with realistic parameters\n",
    "2. Created the geometry in OpenVSP (when available) or used VLM fallback\n",
    "3. Performed an angle-of-attack sweep and extracted CL, CDi\n",
    "4. Visualized the lift curve, drag polar, and efficiency\n",
    "\n",
    "### Key takeaways\n",
    "- OpenVSP enables accurate 3D geometry modeling with fuselage-wing interference\n",
    "- The VLM provides a quick first-estimate for isolated wing aerodynamics\n",
    "- Fuselage presence reduces effective wing aspect ratio slightly\n",
    "\n",
    "### Next steps\n",
    "Proceed to `../04_complete_aircraft/full_aircraft_openvsp.ipynb` for the full\n",
    "aircraft configuration including horizontal and vertical tails with control surfaces."
   ]
  }
 ]
}