Neutrally Buoyant Particle Migration in Poiseuille Flow Driven by Pulsatile Velocity

A neutrally buoyant circular particle migration in two-dimensional (2D) Poiseuille channel flow driven by pulsatile velocity is numerical studied by using immersed boundary-lattice Boltzmann method (IB-LBM). The effects of Reynolds number (25≤Re≤200) and blockage ratio (0.15≤k≤0.40) on particle migration driven by pulsatile and non-pulsatile velocity are all numerically investigated for comparison. The results show that, different from non-pulsatile cases, the particle will migrate back to channel centerline with underdamped oscillation during the time period with zero-velocity in pulsatile cases. The maximum lateral travel distance of the particle in one cycle of periodic motion will increase with increasing Re, while k has little impact. The quasi frequency of such oscillation has almost no business with Re and k. Moreover, Re plays an essential role in the damping ratio. Pulsatile flow field is ubiquitous in aorta and other arteries. This article is conducive to understanding nanoparticle migration in those arteries.

Comparative Test Analysis for Determining Dynamic Deflection by Using GNSS/RTK, Trigonometric Leveling and Elevation of Sight

Respectively applied Trimble R8 GNSS/RTK, Leica TCA2003 3D coordinates measurement and SPRINTER 200M elevation of sight to synchronously monitor the deflection displacement of an underdamped oscillation, it has a 0.5 Hz design frequency and mm level amplitude in this test. Based on the FFT algorithm, spectral information was independently calculated out from these observed data of deflection displacement. Combined the spectrogram with the deflection displacement of R8, TCA2003 and SPRINTER 200M monitoring points, this paper makes a comparative analysis. The results show that the TCA2003 automatic tracking measurement can not only accurately measure the dynamic changes in the process of the damped oscillation dynamic deflection but truly reflect the structure of the dynamic deformation characteristics; the SPRINTER 200M digital leveling can monitor the overall trend of dynamic deflection, but get a harmonic frequency; and GNSS/RTK only acquires a harmonic.

Impedance Characteristics of Pulsed Atmospheric Electrical Discharge in Spherical Plasma Switch

A number of pulsed experiments have been carried out using a high-voltage circuit containing R,L, and C in certain arrangements. A spherical spark gap of steel electrodes was used as a high-current switch operated by a voltage of up to 8kV and triggered in both self-triggering and third-electrode triggering modes. Current measurements were carried out by using both current-viewing resistor and Rogowski coils designed for this purpose. Typical current waveforms have shown obvious dominating inductance effect of the circuit components in an underdamped oscillation. The behavior of the circuit impedance was studied by recording both pulsed current peaks and the charging voltages when currents of up to 2.5kA were recorded. The duration of these current pulses were found to extend between 0.1?s and 0.3?s depending on the values of the circuit components as well as the spacing of the spark gap electrodes along which the plasma propagates at atmospheric pressure. Over the whole range of experimental conditions, the average nominal impedance values were ranged between (2-10)? depending on the gap and circuit parameters. Typical damage patterns were observed with average diameters of up to 8.3 mm on the high voltage electrode and 10.5 mm on the grounded sphere resulting from accumulative discharges and power dissipation within the gap.