ALBERT

Description: GEMPAK was developed to aid designers in the generation of detailed configuration geometry. This program was written to allow the user as much flexibility as possible in his choice of configurations and detail of description desired while at the same time, keeping input requirements, program turnaround time, and cost to a minimum. The program consists of routines that generate fuselage and planar surface (wing-like) geometry and a routine that determines the true intersection of all components with the fuselage. GEMPAK consists of three major parts: the fuselage generator, the generator for planar surfaces, and the module for integrating the configuration components with the fuselage. Each component is input and generated independently. The program then scales the resulting individual geometries for compatibility and merges the components into an integrated configuration. This technique permits the user to easily make isolated changes to the configuration. There are three modes of modeling the fuselage. The first is complete lofting where the fuselage is defined analytically by three to eleven lofting curves that may be continuous or discontinuous. The user needs to input only the minimum number of points that can be fitted with conic sections for a good reproduction of his configuration. The second mode of fuselage modeling is cross-section lofting. This mode is structured around lofting data input for discrete prescribed cross-section locations. The model is not analytic in the longitudinal direction in mode two. The third mode is a point by point mode and requires that all surface points be input at discrete longitudinal locations. The model resulting from this mode is completely nonanalytic. No interpolation routines are provided in either longitudinal or cross-sectional directions. The amount of required input is least for mode one and greatest for mode three. The wing, canard, horizontal tail, fin, and elevon are all generated with a single type of calculation. There are two basic options for input to this part of the airfoil section. The first is to generate a one- or two-panel surface with basic input parameters such as aspect ratio, taper ratio, and sweep angle. A slabsided airfoil or a circular arc airfoil can be input with a minimum of input. The second is to input a point by point description of the airfoil. Once the airfoil description has been entered by either method then there are program options to change dihedral, twist, coordinate translation, angle of attack, and roll angle of the previously defined airfoil. After all of the geometry for the separate parts has been generated, then control passes to the merge section of the program. Merge calculates the intersection of all the planar surfaces with the fuselage. Input consists of program option flags and data to define the geometry of the fuselage and the wing-like portions of the aircraft. This program has been implemented in FORTRAN IV on a CDC 6000 series machine with a central memory requirement of approximately 55K (octal) of 60 bit words.

Description: Results are presented from two separate tests on the same blended wing-body hydrogen fueled transport model at a Mach number of about 8 and a range of Reynolds numbers (based on theoretical body length) of 0.597 x 10 to the 6th power to about 156.22 x 10 to the 6th power. Tests were made in conventional hypersonic blowdown tunnel and a hypersonic shock tunnel at angles of attack of -2 deg to about 8 deg, with an extensive study made at a constant angle of attack of 3 deg. The model boundary-layer flow varied from laminar at the lower Reynolds numbers to predominantly turbulent at the higher Reynolds numbers. Model wall temperatures and stream static temperatures varied widely between the two tests, particularly at the lower Reynolds numbers. These temperature differences resulted in marked variations of the axial-force coefficients between the two tests, due in part to the effects of induced pressure and viscous interaction variations. The normal-force coefficient was essentially independent of Reynolds number. Analysis of results utilized current theoretical computer programs and basic boundary-layer theory.

Description: A computer program, GEMPAK, has been developed to aid in the generation of detailed configuration geometry. The program was written to allow the user as much flexibility as possible in his choices of configurations and the detail of description desired and at the same time keep input requirements and program turnaround and cost to a minimum. The program consists of routines that generate fuselage and planar-surface (winglike) geometry and a routine that will determine the true intersection of all components with the fuselage. This paper describes the methods by which the various geometries are generated and provides input description with sample input and output. Also included are descriptions of the primary program variables and functions performed by the various routines. The FORTRAN program GEMPAK has been used extensively in conjunction with interfaces to several aerodynamic and plotting computer programs and has proven to be an effective aid in the preliminary design phase of aircraft configurations.

Description: Computer program helps designers to generate detailed configuration geometry with much flexibility in choices of configurations and details of description. Input requirements, program turnaround time, and costs are kept low. It consists of routines that generate fuselage and planar-surface (winglike) geometries and routine that determines true intersection of all components with fuselage.

Description: A computer-aided design system has recently been developed specifically for the small research group environment. The system is implemented on a Prime 400 minicomputer linked with a CDC 6600 computer. The goal was to assign the minicomputer specific tasks, such as data input and graphics, thereby reserving the large mainframe computer for time-consuming analysis codes. The basic structure of the design system consists of GEMPAK, a computer code that generates detailed configuration geometry from a minimum of input; interface programs that reformat GEMPAK geometry for input to the analysis codes; and utility programs that simplify computer access and data interpretation. The working system has had a large positive impact on the quantity and quality of research performed by the originating group. This paper describes the system, the major factors that contributed to its particular form, and presents examples of its application.