The hydrodynamics of bubble columns operated at pressures up to 7.0 MPa are investigated using a laser Doppler velocimetry system. Laser Doppler velocimetry is a noninvasive optical technique, which is used to conduct in situ measurements of velocity, with high spatial resolution, fast dynamic response, and the ability to detect flow. The axial and tangential velocities and the Reynolds shear and normal stresses are analyzed and discussed in relation to large-scale structures present in the flow. This study demonstrates the significance of the pressure effect on the flow field in bubble-column systems.

Abstract-In the field of radar target detection, vortex electromagnetic (EM) wave carrying orbital angular momentum (OAM) has drawn great attention in recent years because of its prospect to improve the capacity of information acquisition. As a typical vortex EM wave, the high-order Bessel vortex beam (HOBVB) has the properties of non-diffraction propagation, small central spot diameter, good direction, and long propagation distance. This study investigates the scattering of non-diffracting HOBVB by radar targets. The mathematical description of the electromagnetic field components of the arbitrarily incident HOBVB are given. The surface integral equations for solving the scattering problems involving typical radar targets are established. The effects by OAM intrinsic mode characteristics on the radar scattering cross section are simulated. This investigation is expected to provide useful guidance for revealing EM scattering mechanism in the OAM domain.

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