  We investigate streaming instability using two-fluid approximation (neutral
gas and dust) in a quasi-global, unstratified protoplanetary disc, with the
help of PIERNIK code. We compare amplification rate of the eigen-mode in
numerical simulations, with the corresponding growth resulting from the linear
stability analysis of full system of Euler's equation including aerodynamic
drag. Following Youdin & Goodman (2005) we show that (1) rapid dust clumping
occurs due to the difference in azimuthal velocities of gas and dust, coupled
by the drag force, (2) initial density perturbations are amplified by several
orders of magnitude. We demonstrate that the multi-fluid extension of the
simple and efficient Relaxing TVD scheme, implemented in PIERNIK, leads to
results, which are compatible with those obtained with other methods.
