Dense packings of spheres in cylinders I. Simulations
  We study the optimal packing of hard spheres in an infinitely long cylinder, using simulated annealing, and compare our results with the analogous problem of packing disks on the unrolled surface of a cylinder. The densest structures are described and tabulated in detail up to D/d=2.873 (ratio of cylinder and sphere diameters). This extends previous computations into the range of structures which include internal spheres that are not in contact with the cylinder. 
A. Mughal, H. K. Chan, D. Weaire, S. Hutzler
cond-mat.soft