The variables in equation (8-1) may be separated and integrated to give
The constant of integration C1 may be evaluated by knowing a value of trx at some r. Such a
condition is known at the center of the conduit, r ¼ 0, where for any finite value of C1, the
shear stress, trx, will be infinite. As this is physically impossible, the only realistic value for
C1 is zero. Thus, the shear-stress distribution for the conditions and geometry specified is