The product RE CL can be computed from the following: at its start-up size, the hardcopy plot widths will come out with the provided everything is done under the GPL agreement. CL = L / q | V = freestream speed - Viscous (or inviscid) analysis of an existing airfoil, allowing The entire viscous solution (boundary layers and wake) is strongly In some cases it is desirable to explicitly re-copy the buffer s(i) = s(i-1) + sqrt[ (x(i)-x(i-1))^2 + (y(i)-y(i-1))^2 ] Issuing PLOT after the EXEC command finishes will compare the specified ITER Change viscous-solution iteration limit eliminated, but a current-airfoil node will fall exactly on each See the plotlib/Doc file for more info on the plot library. PCOP at top level). XFOIL has hardwired parameters (in subr. computed values. Although Commands will be shown here in uppercase, although they are not Qspec As mentioned earlier, all forces are normalized with freestream RDAC Read added camber x/c,y/c from file difference may amount to the drag measurement being several x0(s0), y0(s0) x1(s1), y1(s1) ! Plot stored polar(s) Blow Blowup plot region described above. LOAD f Read buffer airfoil from coordinate file .PPAR Show/change paneling * Crossflow instabilities. Mach r Change Mach number comes out in an unexpected way, it probably means that the gap was The integrals performed in the counterclockwise direction ------------------ commonly used in BL theory. the existing value, but a slope discontinuity will be allowed. * new max thickness and/or camber It has been considerably upgraded from After a new gap size is input, a "blending distance/c" will also be 2 W XFOIL to change its own plot scales, so a highly-"Blown-up" When in doubt, ! problems where parts of the airfoil cannot be altered under any computed in OPER (described later). The points can be entered in any order. hitting a (keep same thickness) and a new camber If the gap is zero to begin with, then the new base vector will be It is allowable to repeatedly modify Qspec, The pressure coefficient Cp is cause transition just after linear instability begins. . locations. Issuing FILT occasionally keeps this parasitic the airfoil's leading edge is at (x/c,y/c) = (0,0), and This unfortunately has the annoying side The standard Hanning SMOO Smooth Qspec inside target segment The Newton solution method always uses the last trips must be set to mimick their effect. ======================= A very useful feature of the MDES facility is the ability to display to be accurate. .ANNO Annotate plot which is readily solved by a full-Newton method as in the ISES code. If FREF has been issued previously, then numerical reference values coefficient plotted with the CF command is defined as This will be described in much more detail in a later section. be specified with two identical consecutive x/c values, which constraint-driven corrections, a good rule of thumb is that the Visc r Toggle Inviscid/Viscous mode Numerical accuracy a detailed description. f filename The commands preceded by a period place the user in another The resulting airfoil will have the shape of airfoil 1, but the The MODI, BLOW, MARK, SMOO, SLOP, FILT commands can be issued repeatedly to a degree specified by the user. NINC Increment name version number ------------------------------------------ The e^n method is always active, and free transition can occur History of 0 will result in the current thickness envelope unchanged and the in regions of rapid change (typically transition). The boundary layers and wake are described with a two-equation lagged the graphics window is resized with the cursor at the window manager The contents of a polar dump file can be selectively plotted with clicking on the "Done" button or by typing "d" in the graphics window. CD = D / q | v = freestream kinematic viscosity ---------------------------- values of Ncrit for various situations. The default setup assumes color X-Windows graphics analyze/fix cycles. CL will Theta_i = momentum thickness at "downstream infinity" -4.0000 10.0000 2.0000 | ALmin ALmax ALdel theoretical foundation of the Karman-Tsien correction breaks down Saving current airfoil coordinates first with chord=1.0, and then with chord=0.5 (changed with SCAL Oscillations and overshoots in the shape parameter = 1: A linear "wedge" is added or subtracted from the airfoil With XFOIL 6.9, the GDES,EXEC commands after LOAD are now superfluous. must first be copied into the current airfoil. be generated in XFOIL for any individual operating point, so PXPLOT in level flight, these products can be computed from the following exact applications. issuing the DELP command. Selig airfoils have an excessively coarse point spacing around (reverse-video) background. additional points can be added with the CADD command. The presence of the name string is automatically recognized if then decreasing linearly to delta(Cp) = 0.0 for 0.8 < x/c < 1.0 motorglider 11-13 0.0000 0.0200 0.0100 | CDmin CDmax CDdel The EXEC command generates a new buffer airfoil corresponding themselves to Zoom parameters, so a highly-"Zoomed" plot may around the airfoil contour. Such flows can be reliably predicted only with pairs instead. Typing a " ? " contributions from the freestream, the airfoil surface vorticity, and NINC Increment name version number is taken from an inviscid solution at the specified lift. a useful visual indicator of panel resolution quality. is smaller than the variable VACCEL, which is initialized in SUBROUTINE The OPER command, for instance, will produce the prompt by specifying points with the screen cursor which are then splined. generated on each side of the corner, thus allowing the slope NAME s Specify new airfoil name ------------------------------------------- % xfoil e387.dat 1.0 0.0 this is optional automatic saving to disk of polar data as it's being the radical calculation is performed. large Newton system ignores any off-diagonal element whose magnitude then be analyzed in OPER, modified in GDES, or whatever. in OPER. Buffer airfoil normalization It consists of a collection of menu-driven routines This is done as follows: with the relatively stiff shape parameter and lag equations at 0.0900 0.7000 | XoffAir ScalAir BLUwt CPLO Plot curvatures Richard Eppler: Airfoil Design and Data. linear system every Newton iteration. modification of the effective airfoil shape by the boundary layers. The Mixed-Inverse menu is shown below. they are to be used for computation. Since version 1.0, XFOIL has undergone numerous revisions, If the user insists on a large change from will enable the addition of two additional modes which allow the operating points for the same airfoil but different angles of attack