  In a prototypical mode of single-cell migration, retrograde cytoskeletal flow
is mechanically coupled to the environment, propels the cell, and is sustained
by an anterograde cytosolic flow of disassembled cytoskeletal components.
Supracellular collectives also develop fountain-flows to migrate, but the
opposing cellular streams interact with the environment producing conflicting
forces. To understand the biophysical constraints of fountain-flow
supracellular migration, we develop an active gel model of a cell cluster
driven by a polarized peripheral contractile cable. While the model develops
fountain-flows and directed migration, efficiency and cluster velocity are
extremely small compared to observations. We find that patterned friction or
cluster-polarized single-cell directed migration, both suggested by contact
inhibition of locomotion, rescue robust and efficient supracellular migration.
