Make a copy of the flute passage you want to sound overblown, and paste it into an empty track in a MIDI sequencer -- the software that allows you to edit MIDI songs with multiple tracks.
Transpose the copy of this flute passage one octave lower. Your sequencer has a MIDI transposition function that transposes all designated notes at once. See the user guide for details if you are not familiar with this function.
Decrease only the durations of the transposed notes by about 75 percent. Most sequencers allow this using the "length of MIDI" function.
Return to the original flute passage and slide the notes 10 to 12 ticks forward using your sequencer's "slide MIDI music" function. This creates a slight delay between the lower and higher notes once the transposed lower-octave notes are merged with the original passage.
Copy and paste the transposed and altered passage into the same track and measure as the original passage, making sure you merge rather than overwrite the MIDI data.
Set all note velocities between 50 and 60 on a scale of 0 to 127. Note velocity determines how much punch a note has when sounded. Too little makes the sound mushy; too much results in harshness.
Experiment with velocity until the articulation is as you want. The result sounds like an overblown flute playing the second harmonic and has a somewhat breathy sound.