Is there any explaination to the patterns of the harmonics? I`ll use Bb to explain my point. The first mode of Bb1 is Bb2, an octave. The second mode is F2, which is a fifth about Bb2. Then, the interval increases to a 4th when the third mode is Bb3. what I`m asking is why do the intervals of overtones decrease? Is there any explaination as the why the harmonics follow the pattern that they do?

yes there is