E. Koroteeva

Simulating particle inertia for velocimetry measurements of a flow behind an expanding shock wave

When particle-based velocimetry techniques are applied to complex high-speed flows, the non-ideal tracing capability of seeding particles becomes most prominent. Here, we present a numerical particle tracking methodology to predict the bias errors associated with particle image velocimetry (PIV) of flows with moving shocks. The methodology involves performing computational fluid dynamics simulations that yield time-varying flow fields, which are then used to compute the actual paths and velocities of the seeding particles. We test this approach on PIV measurements of the velocity field behind an expanding semi-cylindrical shock wave, generated by a pulsed sliding discharge. Although in transient high-speed compressible flows the PIV imaging accuracy is still hindered by the finite particle response, the proposed methodology allows for both a successful quantification of PIV errors as well as a direct comparison between particle-based velocimetry and numerical simulations.

Experimental and numerical investigation of a flow induced by a pulsed plasma column

The paper studies, both experimentally and numerically, a high-speed transient flow induced by a pulsed volume discharge in still air at low pressure. It is shown that, in the constricted mode, the discharge is capable of producing uniform deposition of the electrical energy into a long (24 mm in length), thin (less than 2 mm in radius) plasma column. Flow visualization experiments using particle image velocimetry (PIV) and high-speed shadow imaging indicate that this pulsed localized energy deposition generates a highly symmetrical cylindrical shock wave expanding at an average speed of 550 m/s within the first 40 μs after the discharge. Three-dimensional computational fluid dynamics (CFD) simulations successfully reproduce the experimentally observed flow structures and provide better insight into the complex discharge-induced flow. Modeling the trajectories of “virtual” particles within the CFD-predicted flow yields excellent agreement between numerical and PIV flow velocity profiles, and this comparison is used to quantify the rates of “rapid” energy thermalization in the pulsed discharge.The paper studies, both experimentally and numerically, a high-speed transient flow induced by a pulsed volume discharge in still air at low pressure. It is shown that, in the constricted mode, the discharge is capable of producing uniform deposition of the electrical energy into a long (24 mm in length), thin (less than 2 mm in radius) plasma column. Flow visualization experiments using particle image velocimetry (PIV) and high-speed shadow imaging indicate that this pulsed localized energy deposition generates a highly symmetrical cylindrical shock wave expanding at an average speed of 550 m/s within the first 40 μs after the discharge. Three-dimensional computational fluid dynamics (CFD) simulations successfully reproduce the experimentally observed flow structures and provide better insight into the complex discharge-induced flow. Modeling the trajectories of “virtual” particles within the CFD-predicted flow yields excellent agreement between numerical and PIV flow velocity profiles, and this comparis...

High speed imaging of a supersonic waterjet flow

Abstract This work studies a jet formation process and a flow developing from a waterjet cutting head. In experiments, the high speed imaging of a supersonic jet (a Photron FASTCAM SA5 camera with a frame rate of 100 kHz) is complemented with the thermographic measurements conducted using an infrared camera FLIR Systems SC7700 with a frame rate of up to 415 Hz. This study aims to provide new knowledge about two-phase flows under extreme conditions, and is of particular importance for waterjet design optimisation.