1D interferometric Mie scattering for micronozzle exit flow velocity measurement

Abstract The non-invasive nature of optical diagnostic techniques is advantageous in studying micronozzles, as it safeguards the undisturbed nature of the highly sensitive micro-scale flow field. In this work, a laser-based interferometric Mie scattering system is developed using a virtually imaged phased array to quantitatively measure the one-dimensional velocity profile at the exit of micronozzles. A narrow-linewidth solid-state laser is used as the light source, acetone-seeded air flow is used as the gas, and velocity is estimated from the Doppler shift in light scattered from the flow exiting the micronozzle. The measurement system is demonstrated on a 2D micronozzle with a 500 mm throat width and a 1 mm exit width. These results are compared with measurements obtained using particle image velocimetry. Peak axial velocities ranging from 370 m s −1 to 450 m s −1 are measured with a precision of approximately 1% and an accuracy of 5%. This system is relatively inexpensive and is particularly suited to micronozzles where the probed region is small in size.