SUPERPOSITION METHOD OF DRAG ANALYSIS Drag due Trim drag. to lift Zero lift Skin wave friction drag Drag Near Field U U △C。 SKIN FRICTION DRAG DUE TO LIFT Far Field AND TRIM DRAG (WAVE VORTEX) ZERO LIFT WAVE DRAG FIGURE 3.0-2.-DRAG BUILDUP 7
SUPERPOSITION METHOD OF DRAG ANALYSIS Drag due ..;:!':'"' 6 .. " ...:..- -_lf_...... to lift ..::_!iiiii....,-"'"" Zero .::'.:iiiii_L::'"" ___ drag 'wif_tve _7 .:ff_iii:';!'"" Drag U dl_ _'/ Near Field Ul:; SKIN FRICTION / I puU U _2 _ield (WAVE & VORTEX ) ZERO LIFT WAVE DRAG FIGURE 3. 0-2.-DRAG BUILDUP
2)Program Sequencing Program execution is ordered by means of special identification cards,read in the executive,which initiate a specific operation; for instance: GEOM This card instructs the executive to have the geometry module read configuration geometry. PLOT This card orders a plot of the configuration to be drawn, according to size and view requirements which will be supplied. SKFR Compute skin friction for the configuration. Other similar cards control the other basic modules.The configuration that is to be plotted,or analyzed,need not be the complete configuration that has been input.Also,the geometry definition may be updated without complete replacement of the geometry input. A summary of the executive control cards is given in Section 4. For each basic program,there are some inputs that are not geometry (e.g.,Mach number,number of longitudinal cuts in analysis,etc.). These inputs are given immediately after the program calling card and are read in the proper interface routine in the geometry module. 3) Program Answers A limited amount of common storage between the different programs is used to preserve answers and transfer data between modules.The lift analysis module is the largest single program in the system. Therefore,some common blocks used in the lift analysis program are carried also in the executive level without increasing total system size.These data blocks include: Wing camber surface definition Wing thickness pressures ● Fuselage upwash buoyancy pressures Nacelle pressure field ● Asymmetric fuselage buoyancy field (non mid-wing configurations) Another data block transfers the optimized fuselage area dis- tribution,based on wave drag considerations,to the geometry module for updating. 8
2) 3) Program Sequencing Program execution is ordered by means of special identification cards, read in the executive, which initiate a specific operation; for instance: GEOM This card instructs the executive to have the geometry module read configuration geometry. PLOT This card orders a plot of the configuration to be drawn, according to size and view requirements which will be supplied. SKFR Compute skin friction for the configuration. Other similar cards control the other basic modules. The configuration that is to be plotted, or analyzed, need not be the complete configuration that has been input. Also, the geometry definition may be updated without complete replacement of the geometry input. A summary of the executive control cards is given in Section 4. For each basic program, there are some inputs that are not geometry (e.g., Mach number, number of longitudinal cuts in analysis, etc.). These inputs are given immediately after the program calling card and are read in the proper interface routine in the geometry module. Program Answers A limited amount of common storage between the different programs is used to preserve answers and transfer data between modules. The lift analysis module is the largest single program in the system. Therefore, some common blocks used in the lift analysis program are carried also in the executive level without increasing total system size. These data blocks include: • Wing camber surface definition • Wing thickness pressures • Fuselage upwash buoyancy pressures • Nacelle pressure field • Asymmetric fuselage buoyancy field (non mid-wing configurations) Another data block transfers the optimized fuselage area distribution, based on wave drag considerations, to the geometry module for updating
Wing pressure data for use in the pressure summary module (WPLT)utilize the above common blocks and two supplemental disk files for data storage. 3.2 Geometry Module The function of the geometry module is to read system geometry input,update it if required,and arrange it as needed for the individual programs of the system.A schematic of the geometry module is shown in figure 3.2-1. The geometry module is accessed by the executive control cards GEOM NEW (input new configuration)or GEOM (addition or replacement of components).The geometry module is also called to update the fuselage or wing camber surface def initions if the executive cards FSUP or WGUP are read. In addition,the geometry module is called by the executive as an intermediate step in the execution of any of the basic programs.This requires the proper interface routine to be entered,the system geometry to be put into the correct form for the program to be executed,and any special (non-geometric) data required to be read.This is all stacked in the proper order,whereupon the executive then calls the basic program. In order to minimize core storage requirements of the input data,both the basic system geometry and the transferred input (from the geometry module to another program)are stored on tape (or disk).The basic system geometry is preserved on a tape when the geometry module is not in core,and the input "stack"for a given program is written on a tape to be read by the programs when called by the executive.The input tape created by the geometry module thus merely replaces the usual input tape written from cards. The format of the system geometry input is the same as that of the NASA-LRC plot program (reference 2).There are some restrictions (relative to the reference 2 input)in the allowable number of input defining stations, however.The geometry format and limits are given in section 4.Some optional geometry has also been added.This includes provisions for fuselage perimeters to be input (if needed by the skin friction program),and pro- visions for wing camber surface input at planform spanwise stations other than those specified for the system geometry.This camber surface definition, called WZORD,is data in the form normally generated or used by the wing design and analysis programs.Also,nacelles may be located either in the Z coordinate system of the basic geometry or relative to the local wing surface,whichever is more convenient. 3.3 Plot The plot module generates the necessary instructions for drawings of the input configuration,either in hard-copy form (Cal Comp)or on the cathode ray tube.Various view options are available.The view option and drawing size are controlled by program inputs. 9
Wing pressure data for use in the pressure summary module (WPLT) utilize the above common blocks and two supplemental disk files for data storage. 3.2 Geometry Module The function of the geometry module is to read system geometry input, update it if required, and arrange it as needed for the individual programs of the system. A schematic of the geometry module is shown in figure 3.2-1. The geometry module is accessed by the executive control cards GEOM NEW (input new configuration) or GEOM (addition or replacement of components). The geometry module is also called to update the fuselage or wing camber surface definitions if the executive cards FSUP or WGUPare read. In addition, the geometry module is called by the executive as an intermediate step in the execution of any of the basic programs. This requires the proper interface routine to be entered, the system geometry to be put into the correct form for the program to be executed, and any special (non-geometric) data required to be read. This is all stacked in the proper order, whereupon the executive then calls the basic program. In order to minimize core storage requirements of the input data, both the basic system geometry and the transferred input (from the geometry module to another program) are stored on tape (or disk). The basic system geometry is preserved on a tape when the geometry module is not in core, and the input "stack" for a given program is written on a tape to be read by the programs when called by the executive. The input tape created by the geometry module thus merely replaces the usual input tape written from cards. The format of the system geometry input is the same as that of the NASA-LRC plot program (reference 2). There are some restrictions (relative to the reference 2 input) in the allowable number of input defining stations, however. The geometry format and limits are given in section 4. Some optional geometry has also been added. This includes provisions for fuselage perimeters to be input (if needed by the skin friction program), and provisions for wing camber surface input at planform spanwise stations other than those specified for the system geometry. This camber surface definition, called WZORD, is data in the form normally generated or used by the wing design and analysis programs. Also, nacelles may be located either in the Z coordinate system of the basic geometry or relative to the local wing surface, whichever is more convenient. 3.3 Plot The plot module generates the necessary instructions for drawings of the input configuration, either in hard-copy form (Cal Comp) or on the cathode ray tube. Various view options are available. The view option and drawing size are controlled by program inputs. 9
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The plot program was developed at NASA-LRC and has been incorporated into the system with minimum change.Documentation of the program is presented in reference 2. A typical configuration drawing generated by the plot program is shown in figure 3.3-1. 3.4 Skin Friction Skin friction drag for a configuration is computed by separating the airplane into its components,then calculating wetted area and the corresponding turbulent skin friction drag for each component.The wing,tail and/or canard (components which may have large variations in chord length)are strip-integrated to obtain an accurate average skin friction coefficient. Skin friction coefficients are computed from the method of reference 1. Flight conditions for skin friction calculations may be input either as Mach number/altitude,or Reynolds number per foot and total temperature.If the user wishes to input wetted areas for the different components,rather than have the program generate the wetted areas from the system geometry,several special input options are provided. A schematic of the skin friction program is shown in figure 3.4-1. 3.5 Far-Field Wave Drag Program This program computes the zero-lift wave drag of an arbitrary configuration by means of the supersonic area rule.The program was originally developed at the Boeing Company,and has been documented (reference 3)and updated by NASA-LRC.The version of the program used in the design and analysis system is that of LRC. The far-field wave drag program is extremely versatile,and includes a fuselage area optimization feature which is very useful.The fuselage op- timization is accomplished by requiring the program to optimize the overall area distribution of wing-nacelles-tail,etc.,subject to a few fuselage area control points or "restraints".The program then fills-in the non-restrained fuselage area distribution in an optimum fashion for minimum wave drag. In the design and analysis system,a fuselage area distribution may be optimized by initially defining it in the basic geometry,optimizing the definition in the far-field wave drag program,and then transferring the optimized definition to the geometry module for use in further design or analysis cycles.The actual transfer of the optimized fuselage geometry is performed by use of the executive card FSUP,as described in Section 4. 11
The plot program was developed at NASA-LRC and has been incorporated into the system with minimum change. Documentation of the program is presented in reference 2. A typical configuration drawing generated by the plot program is shown in figure 3.3-1. 3.4 Skin Friction Skin friction drag for a configuration is computed by separating the airplane into its components, then calculating wetted area and the corresponding turbulent skin friction drag for each component. The wing, tail and/or canard (components which may have large variations in chord length) are strip-integrated to obtain an accurate average skin friction coefficient. Skin friction coefficients are computed from the method of reference I. Flight conditions for skin friction calculations may be input either as Mach number/altitude, or Reynolds number per foot and total temperature. If the user wishes to input wetted areas for the different components, rather than have the program generate the wetted areas from the system geometry, several special input options are provided. A schematic of the skin friction program is shown in figure 3.4-1. 3.5 Far-Field Wave Drag Program This program computes the zero-lift wave drag of an arbitrary configuration by means of the supersonic area rule. The program was originally developed at the Boeing Company, and has been documented (reference 3) and updated by NASA-LRC. The version of the program used in the design and analysis system is that of LRC. The far-field wave drag program is extremely versatile, and includes a fuselage area optimization feature which is very useful. The fuselage optimization is accomplished by requiring the program to optimize the overall area distribution of wing-nacelles-tail, etc., subject to a few fuselage area control points or "restraints". The program then fills-in the non-restrained fuselage area distribution in an optimum fashion for minimum wave drag. In the design and analysis system, a fuselage area distribution may be optimized by initially defining it in the basic geometry, optimizing the definition in the far-field wave drag program, and then transferring the optimized definition to the geometry module for use in further design or analysis cycles. The actual transfer of the optimized fuselage geometry is performed by use of the executive card FSUP, as described in Section 4. l!