渡邉 智昭 (Tomoaki Watanabe)

K. Inokuma, T. Watanabe, K. Nagata, Y. Sakai Statistical properties of spherical shock waves propagating through grid turbulence, turbulent cylinder wake, and laminar flow Physica Scripta 94(4) 044004 2019 This article may be found at  https://doi.org/10.1088/1402-4896/aafde2 . Abstract Wind tunnel experiments are reported for a spherical shock wave propagating through turbulent wakes of a single cylinder, double cylinders, grid-turbulence, and a laminar flow, whose influences on the shock wave are compared. Overpressure behind the shock wave is measured on a plate while streamwise velocity is measured at the flow point between the measurement plate and the location of the shock wave ejection. Average of peak-overpressure observed upon arrival of the shock wave is decreased by the mean velocity defect of the cylinder wake. Root mean squared (rms) peak-overpressure fluctuation divided by the averaged peak-overpressure is increased by turbulence, and it becomes larger with the rms ve...

X. Zhang, T. Watanabe, K. Nagata Passive scalar mixing near turbulent/non-turbulent interface in compressible turbulent boundary layers Physica Scripta 94(4) 044002 2019 Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  This article may be found at  https://doi.org/10.1088/1402-4896/aafbdf . Abstract Direct numerical simulations for compressible temporally evolving turbulent boundary layers (TBLs) at Mach numbers of M = 0.8 and 1.6 are preformed up to the Reynolds number based on the momentum thickness Reθ ≈ 2200 to investigate a passive scalar field near the turbulent/non-turbulent interface (TNTI) layer that is formed at the edge of the TBLs. The passive scalar is diffused from the wall in the TBLs developing on the moving wall at constant speed. The outer edge of the TNTI layer detected by an isosurface of vorticity magnitude and passive scalar are compared by visualization, and it is shown th...

T. Watanabe, Y. Sakai, K. Nagata, Y. Ito, T. Hayase Implicit large eddy simulation of a scalar mixing layer in fractal grid turbulence Physica Scripta 91(7) 74007 2016 Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  This article may be found at  https://doi.org/10.1088/0031-8949/91/7/074007 . Abstract A scalar mixing layer in fractal grid turbulence is simulated by the implicit large eddy simulation (ILES) using low-pass filtering as an implicit subgrid-scale model. The square-type fractal grid with three fractal iterations is used for generating turbulence. The streamwise evolutions of the streamwise velocity statistics obtained in the ILES are in good agreement with the experimental results. The ILES results are used for investigating the development of the scalar mixing layer behind the fractal grid. The results show that the vertical development of the scalar mixing lay...

T. Watanabe, Y. Sakai, K. Nagata, O. Terashima Joint statistics between velocity and reactive scalar in a turbulent liquid jet with a chemical reaction Physica Scripta T155 014039 2013 Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  This article may be found at  https://doi.org/10.1088/0031-8949/2013/T155/014039 . Abstract Joint statistics between the velocity and the concentration of reactive species are experimentally investigated in a planar liquid jet with a second-order chemical reaction A +  B → R. Reactant species A and B are premixed in a jet flow and a main flow, respectively. An optical fibre probe based on light absorption spectrometry is used to measure the instantaneous concentrations of reactive species. The stream-wise velocity and the concentrations of reactive species are simultaneously measured by combining the optical fibre probe with I-type hot-film anemometry, and we i...