  We systematically investigate the pion transverse momentum spectrum, elliptic
flow, and Hanbury-Brown-Twiss (HBT) interferometry in the granular source model
of quark-gluon plasma droplets in ultra-relativistic heavy ion collisions. The
granular source model can well reproduce the experimental results of the Au-Au
collisions at $\sqrt{s_{NN}}=$ 200 GeV and the Pb-Pb collisions at
$\sqrt{s_{NN}} =$ 2.76 TeV with different centralities. We examine the
parameters of the granular source models with an uniform and Woods-Saxon
initial energy distributions in a droplet. The parameters exhibit certain
regularities for collision centrality and energy.
