VLM 4.997 Manual - the AOE home page
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1. 180 less than 180 but not equal to 0 Cols 21 30 NUMAA Number of angles of attack This value must be at least 1 but no more than 26 In addition the resulting ending in angle of attack ENDAA BEGAA NUMAA 1 STEPAA must be greater than 90 but less than 90 Wednesday November 20 1996 4 3 4 Section four data is required when SCW 0 see section 4 3 1 This section determines the number of span stations for each planform and the number of chordwise control points along each span station Multiple card sets per planform Format F5 1 n 16F5 1 Card 1 Cols 1 5 STA Number of spanwise stations of horseshoe vortices on the left half of the planform This variable sets the number of TBLSCW values read in for that planform Cards 2 n Cols 1 5 6 10 etc TBLSCW I Number of horseshoe vortices at each spanwise station beginning at the station nearest the tip of the planform and proceeding toward the station nearest the root These sets of STA and TBLSCW I cards are repeated for each planform The sum of all the STA values cannot exceed 100 4 3 5 4 3 6 Section five data is required for any planform having a nonzero value for TWIST D see section 4 3 1 This section determines the mean camber line slopes or angles of attack across the planform Multiple cards per planform Format 8F10 6 n 8F10 6 Cols 1 10 11 20 etc ALP Local streamwise angles of attack eg camber flap def2. CL TWIST ALPHA and Y CP are also printed for each plan form For each spanwise station the following data are presented from the left tip towards the root 1 2Y B Location of midpoint of each spanwise station in fraction of wing semispan The next two columns of data describe the additional or angle of attack wing loading at a lift coefficient of 1 based on the total lift achieved and the true configuration area The third column is the chord ratio result and the other columns detail specific kinds of span loadings and local centers of pressure for the configuration The preceeding is done on a planform basis 1 2 3 4 SL COEF span load coefficient clc CLcav CL RATIO Ratio of local lift to total lift cl CL C RATIO Ratio of local chord to averge chord c cav LOAD DUE TO TWIST Distribution of Span load coefficient due to twist and camber at 0 degrees angle of attack for the configuration ADD LOAD AT CL Distribution of additional span load coefficient at CL te BASIC LOAD AT CL 0 Basic span load coefficient distribution at zero lift coefficient These data are the difference of the previous two columns of data SPAN LOAD AT DESIRED CL Distribution of the combination of the basic span load and additional span load coefficients at the desired CL 13 Wednesday November 20 1996 8 AT CL DES X LOCATION OF LOCAL CENT PR The X location of the local center of pressure for the resulti
3. STLOIND Streamwise load indicator Set this value to 0 if the loading along the entire outer streamwise edge or at the outermost breakpoint of this planform is to be 0 0 If the loading is to be non zero along the entire edge or at the outermost breakpoint set this indicator to 1 0 The rest of this set of data describes the breakpoints used to define the AAN line segments on this planform There are AAN 1 breakpoints and all data subsequently described are required on all except the last card of this set the last card uses only the first two variables in the following list 1 Cols 1 10 XREG D X location of the ith breakpoint The first breakpoint is located at the most inboard location of the leading edge for the left hand side of this planform The other breakpoints are numbered around the planform perimeter in increasing order for each intersection of lines in a counterclockwise direction 2 Cols 11 20 YREG D Y location of the ith breakpoint Once the absolute value of Y starts to decrease it cannot be increased 3 Cols 21 30 DIH D Dihedral angle degrees in the Y Z plane of the line from breakpoint of i to i 1 positive upward Note that along a streamwise line the dihedral angle is not defined so use 0 0 for these lines Note the sign of the dihedral angle is the same along the leading and trailing edges 4 Cols 31 40 AMCD The move code this number indicates whether the line s is on the movable panel of a v
4. chordwise horseshoe vortices from the tip to root and is called TBLSCW I This SCW 0 option can only be used for planforms without dihedral and for coplanar configurations SCW must be greater than or equal to 2 for cambered wing vortex flow aerodynamic and KV se solutions 3 Cols 26 30 VIC The nominal number of spanwise stations at which chordwise horseshoe vortices will be located This variable must not cause more than 100 spanwise stations to be used by the program in describing the left half of the configuration In addition the product of the stations spanwise and SCW cannot exceed 400 If SCW is 0 then the sum of the value sin TBLSCW I cannot exceed 400 The use of variable VIC is discussed in references 1 and 2 VIC should always be greater than or equal to 10 so that the near field drag or vortex flow forces on cambered configurations can be properly computed 4 Cols 31 35 MACH Mach number use a value other than 0 0 only if the Prandtl Glauert compressibility correction factor is to be applied The value used should be less than that of the critical Mach number 5 Cols 36 40 CLDES Desired lift coefficient CL d The number specified here is used to obtain the span load distribution at a particular lift coefficient If the drag polar is required over a CL range from 0 1 to 1 0 use CLDES 11 if the vortex flow aerodynamic characteristics are required on a cambered and or twisted configuration use CLDES 10
5. directions for these are downward for 2 U out the right wing for v U and forward for u U These are followed by the induced downwash angles DWNWH arctan w U in degrees Epsilon d Epsilon d Alpha the ratio of local dynamic pressure to free stream dynamic pressure Q LOCAL Q INF and the sidewash angle SIGMA arctan v U in degrees Epsilon is a particular kind of downwash angle given in degrees and defined by Epsilon Alpha arctan sin Alpha w U cos Alpha u U d Epsilon d Alpha is just the differential of the above equation with respect to Alpha and may be useful in certain wing tail body problems SAMPLE INPUT the B 2 as shown in Air International ANALYSIS OF THE B 2 AIR INTERNATIONAL GEOMETRY fhe ci 1 0000 5040 1 Qs 6 0 0 0 0 0 0 0 1 0 59 47 86 0 67 9 72 74 48 26 43 90 63 24 22 50 56 82 12 66 65 46 0 0 BASIC LINEAR AERO 10 18 0 20 0 4 SAMPLE OUTPUT The output is lengthy and requires 133 columns Run the sample case and printout the output to obtain an output to study 17 Wednesday November 20 1996
6. 0 see page 21 If the vortex flow characteristics are required for a specific set of angles of attack use 101 6 Cols 41 45 SA 1 Variable sweep angle for the first planform Specify the leading edge sweep angle in degrees for the first movable line adjacent to the fixed portion of the planform For a fixed planform this quantity may be omitted 7 Cols 46 40 SA 2 same for the second planform Wednesday November 20 1996 10 11 12 13 14 15 16 17 18 19 20 21 Cols 51 55 SA 3 same for the third planform Cols 56 60 SA 4 same for the fourth planform Cols 61 62 TWIST 1 Twist code for the first planform If this planform has no twist and or camber use a value of 0 otherwise specify a value of 1 or 2 Use 1 if the data in section five is in radians use a 2 if the data is in degrees Cols 63 64 TWIST 2 same for the second planform Cols 65 66 TWIST 3 same for the third planform Cols 67 68 TWIST 4 same for the fourth planform Cols 69 70 PTEST Clp indicator if the damping in roll parameter is desired use 1 0 for this quantity Except for the Delta Cp and Clp all other aerodynamic data will be omitted Use a 0 if Clp is not required Cols 71 72 QTEST CLq and Cmq indicator if these stability derivatives are desired use a 1 0 for this quantity Except for Delta Cp Clq and Cmq all other aerodynamic data will be omitted It sho
7. E The corresponding leading edge radius values in the same dimensional units as previously used 4 3 7 Section seven data is required when ATPCOD 2 see section 4 3 1 and CLDES is not equal to 11 100 or 101 see section 4 3 1 This section sets up the field lines used in the flow field analysis TOTFL 1 Cards Format 2F10 6 n 8F10 6 Card 1 Cards 2 n l Cols 1 10 TOTFL Total number of field lines This also controls the read of the field line data cards maximum of 60 Cols 11 20 TOTFP Total number of points along each field line If omitted a value of 75 is assumed Cols 1 10 XDOWN X location where the field line intersects the plane of symmetry positive forward Cols 1 1 20 SWEP Sweep angle of field line in X Y plane in degrees sweepback is positive nd 90 deg lt SWEP lt 90 deg Cols 21 30 ZREF Z height of the field line at the plane of symmetry posi tive down Cols 31 40 DIHED Dihedral angle of the field line in the Y Z plane in de grees Standard convention is employed to determine positive values 90 deg lt DIHED lt 90 deg 4 3 8 Section eight data is always required VLM is able to create three SIF files called SIF1 SIF2 and SIF3 These files contain the significant information from three main sections of output vortex flow aerodynamic results linear aerodynamic results and a description of the horseshoe vortices respectively 1 Card Fo
8. PCOD 1 see section 4 3 1 This section sets up Card 1 4 3 3 the limits of integration used in the computations of the wing leading edge and side edge suction values If the configuration does not have side edges use zeroes for the values of XL and XT I on the second card 2 Cards Format 8F10 6 8F10 6 Cols 1 10 YINNER 1 Represents the Y inner for the first planform Cols 11 20 YOUTER 1 Represents the Y outer for the first planform Cols 21 30 31 40 YINNER 2 YOUTER 2 same for the second planform Cols 41 50 51 60 YINNER 3 YOUTER 3 same for the third planform Cols 61 70 71 80 YINNER 4 YOUTER 4 same for the fourth planform Cols 1 10 XL 1 The leading edge tip X coordinate for the first planform Cols 11 20 XT 1 The trailing edge tip X coordinate for the first planform Cols 21 30 31 40 XL 2 XT 2 same for the second planform Cols 41 50 51 60 XL 3 XT 3 same for the third planform Cols 61 70 71 80 XL 4 XT 4 same for the fourth planform Section three data is required when CLDES 101 see section 4 3 1 This section allows theuser to choose the particular angles of attack to be used in the vortex flow analysis computations 1 card Format 3F10 6 Cols 1 10 BEGAA Beginning angle of attack in degrees This value must be greater than 90 but less than 90 Cols 11 20 STEPAA Step angle of attack in degrees This value must be greater than
9. VLM4997 User s Manual This manual describes the input for John Lamar s vortex lattice program The program resides on trident aoe vt edu In order to run the code the user must have an account on trident This can be obtained from the Design Lab Administrator The user should then check to make sure that usr local bin is in the default path This can be checked by typing printenv PATH If this direc tory is not in the default path it can be added by editing the login file in the user s home directory Before running the code the user should create a working directory within his home directory for the data files After changing into this new directory the user should copy the default input file This is done by typing cp aero v1m4997 VLM DAT Note that the command ends with a space and then a period This tells cp to place a copy of the file in the current directory with the same name Now the user can run the code by simply typing vlm The code will automatically use the data file called VLM DAT in the current directory Therefore to run a different case the user must either modify this input file or copy another input file to the name VLM DAT The output goes to file named PRN The theory is described in the following references and the user s manual provided here is basi cally the instructions from reference 4 with minor corrections and clarifications References 1 Margason R J and Lamar J E Vortex La
10. ariable sweep wing Use 1 0 for a fixed line defaults to 1 0 if not set or 2 0 for a movable line Good results require that a few common rules of thumb be used in selecting the planform break points The number of line segments should be minimized Breakpoints should line up streamwise on front and rear portions of each planform and should line up between plan forms Streamwise tips should be used and small spanwise distances should be avoided by making edges streamwise if they are actually very highly swept Wednesday November 20 1996 4 3 GROUP 2 DATA There are eight sections of group 2 data Each section may be required or optional depending on the previous input and each may have one or more input cards lines of input Each section is described individually 4 3 1 Section one data is always required 1 Card Format A20 8F5 2 8F2 0 411 1 Cols 1 20 CONFIG An arbitrary configuration designation of up to 20 alphanumeric characters 2 Cols 21 25 SCW The number of chordwise horseshoe vortices to be used at a spanwise station for each planform The maximum value for this variable is 20 If varying values of chordwise horseshoe vorticies are desired due to either multiple planforms or large discontinuities in chord across the span the user can input a value of O that will cause the program to expect user supplied data at this point in the input stream The data are in the form of a table that contains the number of
11. ction coefficient term 5 CDIIV CL 2 Total drag coefficient over CL d 2 6 CT Total leading edge thrust coefficient 7 CS Total leading edge suction coefficient This completes the printout for combination i however for combination iv additional printout is produced In particular Kp and Kv values and respective centroids in both chordwise and spanwise directions and the associated limits of integration for the leading edge and side edge values of Kv The item entitled Sum of the positive side edge contributions which appears 14 Wednesday November 20 1996 here on the printout is indicative of the contribution to the side edge forces for that particular planform which were oppositely signed to those that contributed in a manner to increase Kv se The value of Kv se does contain these positive contributions provided the sweep angle is positive They should not be and therefore are not added in for the planform with a swept forward leading edge Furthermore aerodynamic performance values for each planform and for the entire configuration will be listed over an angle of attack range by the use of the Polhamus Suction Analogy The headings are expalined below KP Kp KVLE Kv le KV SE Kv se ALPHA a CN CN tot CLP CL p CLVLE CL vle CLVSE Kv se lsing Isina cos a CMP pitching moment coefficient due to CL p CMVLE pitching moment coefficient due to CL vle CMVSE pitching moment coefficient due to CL vse CM to
12. erence chord of the configuration This chord is used only to nondimensionalize the pitching moment terms and must be greater than zero Cols 31 40 SREF Reference area this is used only to nondimensionalize the comput ed output data such as lift and pitching moment and must always be greater than zero Cols 41 50 XLOCTN Pitching moment reference point location relative to coordinate origin along the X axis Cols 51 60 CTILDA Characteristic chord in the augmented vortex lift computations see reference 3 Cols 61 70 XTILDA X location of the centroid of augmented vortex lift Cols 71 80 DISTALE Distance along the leading edge where the vortex flow is developed that leads to the augmented vortex lift 3 Wednesday November 20 1996 The data required to define the planform s is provided in the next set of group 1 cards as follows 1 Cols 1 10 AAN Number of line segments used to define the left half of the planform does not include the innermost streamwise A maximum of 24 line segments may be used per planform and each planform must extend to the plane of symmetry 2 Cols 11 20 XS X location of the pivot use 0 0 for a fixed planform 3 Cols 21 30 YS Y location of the pivot use 0 0 for a fixed planform 4 Cols 31 40 RTCDHT Vertical distance of the particular planform being read in with respect to the reference planform root chord height use 0 for the reference planform 5 Cols 41 50
13. erodynamic characteristics of up to four complex planforms The concepts embodied in this program are mostly detailed in references and 2 this document is intended to serve as an update to these references and include the additional concept of reference 3 for users of this program 3 MODELING THE CONFIGURATION The configuration can be modeled with up to four planforms all of which must extend to the plane of symmetry Y 0 0 The fuselage is represented by its planar projection experience to date indicates that this produces acceptable global forces and moments for most wing body tail configurations Winglets can be modeled but the dihedral angle must be less than 90 0 degrees and greater than 90 0 degrees Both upper positive dihedral and lower negative dihedral winglets can be accounted for in this code The program uses as its solution surface the chord plane which may be inclined due to dihedral Moreover the only out of X Y plane displacement specifically allowed for is dihedral Local camber and twist is assumed to be small and can be represented by its slope projection to the local solution surface The wind and body axes are assumed to be coincidental in the code 4 RUNNING THE PROGRAM 4 1 INPUT DATA SETUP The very first card of input is the Title card and the user can have up to 80 characters of free field information on it about the data being run This is only used by the program as a header for output Note that the
14. hed flow heading are the lift drag and pitching moment CL CD CM coefficients for both zero leading edge suction and full leading edge suction over the angle of attack range These items include all the appropriate trigonometric terms Regarding the vortex induced separated flow terms some headings include the potential flow terms and some do not Those which include the potential flow terms lead to total results whereas those which are isolated such as side edge or augmented vortex lift terms do not lead to total values The augmented vortex lift is described in Reference 3 Combination vii determines the flow field around the configuration in the attached flow First the elemental panel circulation values Gamma U associated with the basic load and the additional load at CL 1 0 are listed followed by those associated with the total load and the additional load at the desired CL This is followed by a heading which lists out the geometric data for the prescribed field line along with the 16 Wednesday November 20 1996 desired CL and the required configuration angle of attack from linear attached flow aerodynamics Then from near the plane of symmetry to approximately three times the configuration semispan the flow field properties are determined along that line The X Y and Z coordinates of each field point and the associated normalized downwash w U sidewash v U and backwash u U values are then listed Note that the positive
15. l when the total lift is CL d 11 Wednesday November 20 1996 5 1 4 The fourth group of data presents the following geometric results 1 2 T7 8 REF CHORD Reference chord of the configuration C AVERAGE Average chord cav true configuration area divided by true span TRUE AREA True area computed from the configuration listed in second group of geometry data REFERENCE AREA Reference area B 2 Maximum semispan of all planforms listed in second group of geometry data REF AR Reference aspect ratio computed from the reference planform area and true span TRUE AR True aspect ratio computed from the true planform area and true span MACH NUMBER Mach number 5 2 AERODYNAMIC DATA If PTEST 1 or QTEST 1 on the configuration card then either Clp or CLq and Cmq are computed and printed followed by program termination Otherwise the aerodynamic data are described by at least two groups of results The first is always present but the second depends on what is requested on the configuration card The following items of the first group of data are given in the order that they are found on the printout Note that CL ALPHA CL TWIST CM CL CMO CDI CL 2 are based on the specified reference dimensions Many of the items that follow are for the complete configuration 5 2 1 1 DESIRED CL Desired lift coefficient CL d specified in Input Data for complete configuration 2 COMPUTED ALPHA Ang
16. le of attack at which the desired lift is developed CL d CL ALPHA ALPHA at CL O 3 CL WB That portion of desired lift coefficient developed by the planform with the maximum span when multiple planforms are specified When one planform is specified this is the desired lift coefficient If two or more planforms have the same span and this value is equal to the maximum the planform used here is the latter one read in 4 CDI AT CL WB Induced drag coefficient for lift coefficient in the previous item When two or more planforms are specified this is the induced drag coefficient of only the planform with the maximum span This result is based on the far field solution 12 Wednesday November 20 1996 10 11 12 13 CDI CL WB 2 Induced drag parameter computed from the two previous items 1 PI AR REF Induced drag parameter for an elliptic load distribution based on reference aspect ratio CL ALPHA Lift curve slope per radian and per degree CL TWIST Lift coefficient due to twist and or camber at zero angle of attack CL tc ALPHA AT CL O Angle of attack at zero lift in degrees nonzero only when twist and or camber is specified Y CP Spanwise distance in fraction of semispan from root chord to center of pressure on the left wing panel CM CL Longitudinal stability parameter based on a moment center about the reference point CMO Pitching moment coefficient at CL O CL ALPHA
17. lection in radians if TWIST 1 or in degrees if TWIST 2 These are the values at the control point for each horseshoe vortex on the planform when the innermost streamwise edge of the reference planform has an angle of attack of 0 degrees The volume of this data will usually require several input cards For the first value on the first card use the local angle of attack for the horseshoe vortex nearest the first planform leading edge at the tip for the second value use the angle of attack for the horseshoe vortex immediately behind in the chordwise direction Continue in the same manner for the rest of the horseshoe vortices at the tip Begin a new card for the next inboard station and input the data in the same chordwise manner Repeat for all successive inboard spanwise stations on that planform For each planform with twist camber start the data on a new card and specify the data from the tip and proceed chordwise and then inboard as detailed above Section six data is required for any planform having a nonzero value for LERAD I see section 4 3 1 This section determines the distribution of leading edge radius across the planform The parameter LERAD also specifies how many Y location LE radius pairs are specified in this section 2 Cards Format 8F10 6 8F 10 6 Wednesday November 20 1996 Card 1 Cols 1 10 11 20 etc YLE Y span locations of the leading edge radius values Card 2 Cols 1 10 11 20 etc RADL
18. ng span load at CL d as a function of 2Y b 5 22 The other options available as group two aerodynamic data are accessed based on the values of CLDES and ATPCOD For instance with CLDES 11 and ATPCOD 0 0 the program will produce a drag polar CDI at CL WB versus CL WB based on the linear aerodynamics in the middle of the first part of group one aerodynamic data This and other combinations are given in the table below along with their purposes COMBINATION CLDES ATPCOD PURPOSE i 101 100 gt CL d gt 0 0 Determine linear aerodynamics ii 11 0 Linear aerodynamic drag iii 101 100 0 polar not valid iv 101 100 gt CL d gt 0 1 Planar wing vortex flow aerodynamics v 11 1 not valid vi 101 100 1 Cambered wing vortex flow aerodynamics vii 101 100 gt CL d gt 0 2 Determine flow field off wing Vili 11 2 not valid ix 101 100 2 not valid x 101 100 gt CL d gt 0 3 Determine longitudinal load distribution xi 11 3 not valid xii 101 100 3 not valid For combinations i iv and x the induced drag leading edge thrust and suction coefficient characteristics at each spanwise station are computed from a near field solution for the total loading at CL d and presented 1 L E SWEEP ANGLE Leading edge sweep angle in degrees 2 CDI C 2B Nondimensional section induced drag coefficient term 3 CT C 2B Nondimensional section leading edge thrust coefficient term 4 CS C 2B Nondimensional section leading edge su
19. ngles and the move codes The data are listed primarily for variable sweep wings to provide a definition of the planform where the outer panel sweep is different from that of the reference planform This is followed by a printer plot of the approximate configuration 5 1 3 The third group of data presents a detailed description of the horseshoe vortices used to represent the configuration These data are listed in nine columns with each line describing one elemental panel of the configuration see Figure 2 in the same order that the twist and or camber angles of attack are to be provided 10 Wednesday November 20 1996 Figure 2 Nomenclature used to describe the geometry of an elemntal panel The following items of data are presented for each elemental panel 1 2 X C 4 X location of quarter chord at the horseshoe vortex midspan X 3C 4 X location of three quarter chord at the horseshoe vortex midspan This is the X location of the control point Y Y location of the horseshoe vortex midspan Z Z location of the horseshoe vortex midspan S Semiwidth of horseshoe vortex C 4 SWEEP ANGLE Sweep angle of the quarter chord of the elemental panel and horseshoe vortex DIHEDRAL ANGLE Dihedral angle of elemental panel LOCAL ALPHA IN RADIANS Local angle of attack in radians at control point X 3C 4 Y Z DELTA CP AT DESIRED CL Delta Cp or Net Cp normal to the surface at dihedral for each elemental pane
20. re is only one title card per input deck The actual input data to VLM is organized into two distinct groups group defines the reference planform s and group 2 defines the details for the particular solution An example input follows the description of the input and output The individual details of the items in the deck layout are given in the following sections 4 2 GROUP 1 DATA This group of data defines the planform s projected into the X Y plane with all the coordinates being given for the left half of the configuration negative y values The axis system is shown in Figure 1 The Y 0 intercept coincides with the plane of symmetry and is positive to the right of this plane The X 0 intercept may be taken to occur anywhere along the symmetry plane of the configuration X is positive pointing into the wind Wednesday November 20 1996 Note X opposite standard aerodynamic convention Y Planform 1 l6 1 bi S Planform 2 7 Figure 1 Definition of axis system for VLM4997 All cards use the 8F10 6 format for the group 1 data The fields in this group are as follows 1 Cols 1 10 PLAN Number of planforms for this configuration PLAN can assume values of 1 0 2 0 3 0 or 4 0 Cols 11 20 TOTAL Number of sets of group 2 data specified for this configuration The maximum number of data sets is limited by the computation time specified by the user and the print limit 50000 lines Cols 21 30 CREF Ref
21. rmat 3F10 6 1 Cols 1 10 SIF1 First SIF file creation indictor To create the SIF file con taining the vortex flow aerodynamic results use a 1 Otherwise use a 0 default Wednesday November 20 1996 2 Cols 11 20 SIF2 Second SIF file creation indicator To create the SIF file containing the linear aerodynamic results use a 1 Otherwise use a 0 default 3 Cols 21 30 SIF3 Third SIF file creation indicator To create the SIF file con taining a description of the horseshoe vortices use a 1 Otherwise use a 0 de fault 5 OUTPUT DATA The printed results of this computer program appear in two parts geometry data and aerodynamic data 5 1 GEOMETRY DATA The geometry data are described in the order that they are found on the printout 5 1 1 The first group of the data describes the basic configuration it states the numbers of lines used to describe each planform the root chord height pivot position and then lists the breakpoints sweep and dihedral angles and move codes These data are basically a listing of input data except that the X coordinates are adjusted to the reference point location and the sweep angle is computed from the input 5 12 The second group of data describes the particular configuration for which the aerodynamic data are being computed Included are the configuration designation sweep position a listing of the breakpoints of the planform X Y and Z the sweep and dihedral a
22. tal pitching moment CD CL tot x tana CL 2 PI AR CL tot Pi Aspect Ratio The additional printout associated with combination x which determines the longitudinal load distribution is as follows see figure 4 for definition of the nomenclature 1 X The X location at which the spanwise integration of Delta Cp or Net Cp is to occur 2 Y The Y value at which Delta Cp or Net Cp is interpolated 3 INTERPOLATED DELTA CP The values of Delta Cp interpolated from the chordwise arrangement to that of a spanwise one 4 BL X Local span b x 5 CNL 2 Yin by x 2 2 expe faga b B x 2 te Aix 6 CN FOR PLANFORM I Lib 2 q CN I CNL d x L Sref 15 Wednesday November 20 1996 7 TOTAL CN Total value of CN for the configuration where PLAN CN tot CND I 1 Figure 4 Nomenclature for longitudinal load distribution analysis The vortex flow aerodynamics for cambered wings are determined when combination vi is specified and is done from a solution in the body axis system of the leading edge suction force acting on a deflected surface over a range of angles of attack Kv le is not solved for in this solution but its effect is calculated at each internally prescribed body axis angle of attack Kv se is solved for in the manner described in reference 2 and is tabulated The headings on the printout are divided into attached flow and separated flow regions Under the attac
23. ttice FORTRAN Program for Estimating Sub sonic Aerodynamic Characteristics of Complex PLanforms NASA TN D 6142 Feb 1971 2 Lamar J E and Gloss B B Subsonic Aerodynamic Characteristics of Interacting Lifting Surfaces with Separated Flow around Sharp Edges Predicted by a Vortex Lattice Method NASA TN D 7921 Sept 1975 3 Lamar J E and Frink N T Experimental and Analytic Study of the Longitudinal Aerody namic Characteristics of Analytically and Empirically Designed Strake Wing Configurations at Subcritical Speeds NASA TP 1803 June 1981 4 Lamar J E and Herbert H E Production Version of the Extended NASA Langley Vortex Lattice FORTRAN Computer Code Volume I User s Guide NASA TM 83303 April 1982 VLM 4997 User s Guide from reference 4 1 ABSTRACT SUMMARY This document summarizes the latest production version Mark 4 997 of the NASA Lan gley Vortex Lattice Computer Program All viable subcritical aerodynamic features of previous versions have been retained This version extends the previously documented program capabilities to four planforms 400 panels and enables the user to obtain vortex flow aerodynamics on cambered planforms flow field properties off the configuration in attached flow and planform longitudinal load distributions Wednesday November 20 1996 2 INTRODUCTION The NASA Langley Vortex Lattice FORTRAN Program VLM is designed to estimate the subsonic a
24. uld be noted that both PTEST and QTEST cannot be set equal to 1 simultaneously for a particular configuration Use 0 if Clq and Cmq are not required Cols 73 74 ATPCOD Set to 0 it will cause only linear aerodynamic results to be printed out Set to 1 this will cause the program to print out the contributions to the lift drag and moment from the separated flow around the leading side edges Set to 2 it will provide the local flow field velocities away from the configuration and set to 3 it will provide the attached flow longitudinal load distribution see page 19 Cols 75 76 REPORT Vortex flow report option For sectional planform and overall characteristics use a 0 For planform and overall characteristics use a 1 For overall characteristics only use a 2 The value used here will not affect the information written to the SIF file SIF1 Col 77 LERAD 1 Leading edge radius indicator for the first planform If this planform has no leading edge radius use a 0 Otherwise specify the number of Y location LE radius pairs available for interpolation across this planform see section 4 3 6 At least 2 but no more than 8 pairs may be specified These pairs need not be in any particular order Col 78 LERAD 2 same for the second planform Col 79 LERAD 3 same for the third planform Col 80 LERAD 4 same for the fourth planform Wednesday November 20 1996 4 3 2 Section two data is required when AT
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