Abstract
A numerical study of hydrodynamic focusing in microchannels is presented and compared with experimental results. The emphasis is on the characterization of the focused sheet in terms of its shape and position. The sheet defines the measurement plane when using selective seeding, a novel seeding method for micro-PIV. It is found that the sheet is considerably deformed at high flow velocities and large side stream ratios, making the technique applicable to micro-PIV in the velocity ranges below ~10mm/s. Using lower angles of the side stream inlet channels, the sheet deformation is substantially reduced, extending the velocity range in which selectively seeded micro-PIV is feasible.