  The effect of various velocity boundary condition is studied in
two-dimensional Rayleigh-B\'enard convection. Combinations of no-slip,
stress-free and periodic boundary conditions are used on both the sidewalls and
the horizontal plates. For the studied Rayleigh numbers Ra between $10^8$ and
$10^{11}$ the heat transport is lower for $\Gamma = 0.33$ than for $\Gamma = 1$
in case of no-slip sidewalls. This is surprisingly opposite for stress-free
sidewalls, where the heat transport increases for lower aspect-ratio. In wider
cells the aspect-ratio dependence is observed to disappear for $\text{Ra} \ge
10^{10}$. Two distinct flow types with very different dynamics can be seen,
mostly dependent on the plate velocity boundary condition, namely roll-like
flow and horizontal zonal flow, which have a substantial effect on the dynamics
and heat transport in the system. The predominantly horizontal zonal flow
suppresses heat flux and is observed for stress-free and asymmetric plates. Low
aspect-ratio periodic sidewall simulations with a no-slip boundary condition on
the plates also exhibit zonal flow. In all the other cases, the flow is
roll-like. In two-dimensional Rayleigh-B\'enard convection, the velocity
boundary conditions thus have large implications on both roll-like and zonal
flow that have to be taken into consideration before the boundary conditions
are imposed.
