Tuesday, June 28, 2011
USAF DATCOM: Lesson #1 (3)
Datcom_1-3.
Right now we are ready to run our very first DATCOM analysis. Make sure your file look exactly like the following:
kode
Save the file as for005.dat, in the same folder with Datcom.exe. Close the file, then run the datcom.exe (by double clicking it). In the same folder, datcom will create three other file, which will be for013.dat, for014.dat, and datcom.out. Right now Im gonna explain just the latest. Datcom.out is where the entire datcom output placed. Open it using notepad. If there nothing wrong in for005 file you created, the datcom.out should look like the folowing:
datcom.out
Congratulations. You've done your very first datcom analysis. Lets now observe what the datcom.out contains.
The structure of datcom.out is usually as follows:
figure
It contains (1) Datcom blah-blah (2) What you inputted in for005 (3) What Datcom read from your input (4) lifting surfaces cross section analysis (5) Static Aerodynamic analysis on flight condition you want (usually, this part is what you really want from Datcom).
By reading the output, Im sure you can guest each of its meaning. For a complete datcom.out interpretation, click here.
Right now, lets close the datcom.out, and go back to our for005.dat. As you may notice in datcom.out. The analysis is just carried out for one angle of attack condition. In fact, datcom could accomodate up until 20 angle of attack condition in one run. The same also true for the speed and air density (or height).
Now, change NALPHA value to 20.0, and ALSCHD to a range of angle of attack from -18.0 to 20.0, in the FLTCON namelist group, as shown as follows:
kode
Notice we also change the altitude (NALT, ALT) and speed (NMACH, MACH) for three condition each. Save your file (remember, as for005.dat). Close it, and run DATCOM.exe again. Your analysis in Datcom.out file will look as follows:
kode
Observe the analysis result. The aerodynamic characteristics is calculated for all angle of attack we inputted. Scroll down, and you will see more result for each speed and altitude combination. The information of speed, altitude, and other references, are described in the beginning of each results, as follows:
result
Now im going to explain one more variable in this first course. The LOOP variable, used in the FLTCON namelist. As you already notice, the DATCOM calculation before were done for each combination of height and speed. What if we want our analysis being conducted for each speed in each altitude? For this purpose, we need the LOOP variable. Write the variable in the FLTCON namelist in our for005.dat file, as follows:
kode
Save it again, close it, then run DATCOM again. Open the result. Now you get 9 condition analysis instead of 6. Try to change the LOOP value to 3.0. See what hapen in the result. For a complete explanation about the LOOP variable, click here.
Thats all for this very first lesson. Thank you.
And youre comments are always welcome. Download Source.
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