  We consider active particles swimming in a convergent fluid flow in a
trapezoid nozzle with no-slip walls. We use mathematical modeling to analyze
trajectories of these particles inside the nozzle. By extensive Monte Carlo
simulations, we show that trajectories are strongly affected by the background
fluid flow and geometry of the nozzle leading to wall accumulation and upstream
motion (rheotaxis). In particular, we describe the non-trivial focusing of
active rods depending on physical and geometrical parameters. It is also
established that the convergent component of the background flow leads to
stability of both downstream and upstream swimming at the centerline. The
stability of downstream swimming enhances focusing, and the stability of
upstream swimming enables rheotaxis in the bulk.
