The flow around a gyrocopter is shown here, calculated approximately two-dimensionally. The images were calculated with a
2D-Navier-Stokes-Solver: For turbulent flow according k,ε - turbulence model,
speed 120 km/h in air at 13 C and 1 bar, discretized in 898 × 241 points and with
the boundary conditions: inflow on the left, outflow on the right, slides on top and bottom.
The file Bildbereich.png was created with Gnuplot and shows the outline of the gyrocopter in the underlying x,y coordinate system. It covers 974 × 326 pixels, because the border areas are still present; the color depth is 24 bits.
The file Kontour-matrix.png was created with Irfanview and Gimp , i.e. the edges of Bildbereich.png were cut off, possible remains were covered white, the obstacle area filled black, the color depth reduced to 1 bit b/w. The image file includes 898 × 241 pixels. The image must now be mirrored vertically and saved under the same name.
The file Kontour-matrix.xpm is loaded into a large editor, e.g. Kate , and saved as Kontour-matrix.txt . All marks outside the matrix are deleted. There are now only the characters
for fluid and
for obstacle, a total of 241 rows and 898 columns.
With the editor Kate all characters
will be changed in
0 + blank
1 + blank
. Kontour-matrix01.txt has 241 rows and 1796 columns;
stands for fluid and
for obstacle, separated by one blank.
With the editor Kate all characters in Kontour-matrix01.txt
will be changed in
. The file is saved as tragschrauber.flag and is one input file for the further calculation.
The first calculations showed, that tragschrauber.flag contains here a total of seven unauthorized obstacle cells. That must be removed, either by deleting the cell or by expanding the obstacle. With Kate all
are changed, the unauthorized cell is corrected, then all
for the new flag file.
If you want to check the obstacle area of file tragschrauber.flag , it is recommended to change all
to blank and save the file as tragschrauber.flag1 . With the command
a2ps -l500 -o file.ps tragschrauber.flag1
file.ps is created , which can be imported with Gimp and 600 Pixel/in and saved as flagfile.png ; the obstacle cells are visible as
on white background.
The streamlines were calculated in time intervals of ΔT* = 0.5 , d.h. ΔT = ΔT* · L / c∞ = 0.126s and compiled as video.
The formation of the Kármán vortex street can be seen.