  Discontinuous shear thickening (DST) observed in many dense athermal
suspensions has proven difficult to understand and to reproduce by numerical
simulation. By introducing a numerical scheme including both relevant
hydrodynamic interactions and granularlike contacts, we show that contact
friction is essential for having DST. Above a critical volume fraction, we
observe the existence of two states: a low viscosity, contactless (hence,
frictionless) state, and a high viscosity frictional shear jammed state. These
two states are separated by a critical shear stress, associated with a critical
shear rate where DST occurs. The shear jammed state is reminiscent of the
jamming phase of granular matter. Continuous shear thickening is seen as a
lower volume fraction vestige of the jamming transition.
