Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

[Phys-l] Adding a dissipation term.



After the recent comments on the difficulty of adding dissipation in the L. formulation**, I hesitantly added ViscousDampingCoefficient* (V1) to



X1 (double dot) = F(X1, V1, K, X2, V2, L, m1, m2 ) where X1 is the position of the mass (m1) of the spring oscillator, V1 it's speed, and X2 is the angle of the coupled pendulum, its bob mass (m2) and V2 its angular speed. the m1 is the support for the suspension (a rotary motion detector) of the pendulum. K is the spring constant and L the rod length. There is a corresponding X2 (double dot), but I ignore its dissipation, because the pendulum's Q is > 1k. The Q of the spring oscillator is very low. (~ <100).

The two X's (double dotted) were found by plugging and chugging into the formula the L=T-U. Separating the accelerations was VERY time consuming! I checked the result by linearizing the sines and cosines and comparing to AP French's small angle derivation***. Also comparing the exptl. curves (data) to that predicted by my analytical result is "reasonable" To begin w/, I'm using the linear dissipation, but the exptl. trials show the dissipation is mainly Coulomb. If what I've done (added the VDC*v1) is valid, I'll try the Coulomb (signum[V1]*Cdc)?.

comments please.

** Is this only in the before plugging and chugging?
*** Initial trial angles ~ > one radian.

bc over his head in theory.

p.s. this work is of horological interest, as a principle problem with very high Q pendulum clocks is support movement; both due to very heavy bobs and microseisms.