Parametric geometry model for a blended wing body

A method for defining lofting parameters for a lofting module in a computer system for a blended wing body air vehicle comprising the steps of:

• providing as an input the required payload volume of an air vehicle;
• analyzing the payload volume to determine coordinates for a plurality of corner points of the payload volume;
• passing the coordinates of the plurality of points to a loft module as keep-out points;
• establishing a body portion of the blended wing body using a faceted minimum volume which encloses all of the provided keep-out points;
• creating a trapezoidal wing shape and size to accommodate aerodynamic performance requirements;
• trimming a leading edge of the body portion and trapezoidal wing leading edge;
• blending a trailing edge of the body portion and trapezoidal wing trailing edge;
• establishing a leading edge elevation;
• with leading edge radius as an input, defining all other point coordinates and all tangents and remaining curvatures to smoothly enclose the payload volume in a first plurality of aerodynamic sections;
• defining aerodynamic requirements of the trapezoidal wing including wing thickness, camber, twist and shear for a second set of aerodynamic sections;
• defining sections in a transition region between the body portion and the trapezoidal wing;
• and,
• providing the first plurality of sections, second plurality of sections and transition sections as outputs to a lofting module.

A method for determining a blended wing body air vehicle shape using modules in a computer system comprising the steps of:

• providing as an input the required payload volume of an air vehicle;
• analyzing the payload volume to determine a list of corner points of the payload volume;
• passing the list of points to a Loft Module as keep-out points;
• establishing a body portion of the blended wing body using a faceted minimum volume which encloses all of the provided keep-out points and
• creating a leading edge planform associated with the body portion by establishing a local payload maximum height, Hmax, in the chordwise direction on the faceted volume, determining a leading edge offset curve applying a predefined input parameter, L_over_Hmax, to the local payload height and determining a first segment line and second segment line for a leading edge based on input parameters defined by a leading edge first segment angle, leading edge second segment angle, and a leading edge break ratio for first and second segment, and shifting the created leading edge to contact the leading edge offset curve;
• and,
• creating a trailing edge planform associated with the body portion by determining a trailing edge constraint from an approximate airfoil closure angle and upper and lower payload trailing edge curves from the faceted minimum volume to define a midpoint equidistant from each which is then offset to achieve the desired closure angle forming a trailing edge constraint curve, constructing a trailing edge curve using input parameters of a trailing edge second segment, a trailing edge first segment angle and a trailing edge first and second segment break ratio;
• and shifting the trailing edge curve to contact the trailing edge constraint curve;
• creating a trapezoidal wing shape and size to accommodate aerodynamic performance requirements by
• determining an outboard wing side of body cord as a percentage of side of body chord established as the distance between the leading edge and trailing edge curves at a lateral extent of the faceted payload volume, determining an outboard wing root location as a percentage of remaining chord from the leading edge of the side of body cord, establishing an outboard wing span, establishing an outboard wing leading edge sweep by defining a Maximum Sweep as the sweep resulting from intersection of the outboard wing leading edge with the leading edge second segment at the defined outboard wing span and, if maximum sweep is negative, then the maximum negative number is used, and defining an outboard wing taper ratio;
• trimming a leading edge of the body portion and trapezoidal wing leading edge;
• blending a trailing edge of the body portion and trapezoidal wing trailing edge;
• establishing a leading edge elevation;
• with leading edge radius as an input defining all other point coordinates and all tangents and remaining curvatures to smoothly enclose the payload volume in a first plurality of aerodynamic sections;
• defining aerodynamic requirements of the trapezoidal wing including Wing Thickness, Camber, Twist and Shear for a second set of aerodynamic sections;
• defining sections in a transition region between the body portion and the trapezoidal wing;
• and,
• lofting the blended wing body based on the first plurality of sections, second plurality of sections and transition sections.