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To enhance energy separation in a counter-current Ranque-Hilsch vortex tube, a newly designed hollow helical fin was inserted into the hot tube of the vortex tube. In this study, the effect of the fin on the energy separation was investigated using three types of the vortex tube, and then computational fluid dynamics (CFD) simulation has been conducted to understand the experimental results and discuss the flow structure in the vortex tube with the hollow helical fin. As a result, it was found from the experimental data that the fin effectively enhanced energy separation, and that the tube length could be shorten. When the inlet air pressure was 0.5 MPa, the maximum temperature difference from the inlet to the cold exit was 62.2$^{\circ}$C. The CFD code employing the Reynolds Stress Model (RSM) turbulence model was used to analyze the fluid dynamics in the vortex tube. As a result, it was confirmed that the temperature, velocity, and pressure distributions changed significantly at the stagnation point, and that the distributions in the tube with the fin were completely different from those without the fin. It was thought that a strong reversing helical vortex flow with small recirculating vortex structure formed between the fin end and the stagnation point on the cold exit side would enhance energy separation in the vortex tube with the hollow helical fin., ボルテックスチューブにおけるエネルギー分離を促進するために、新たに設計した中空螺旋状フィンを管内に挿入した。本報では、3種類の管を用いて、フィンがエネルギー分離に及ぼす影響を実験的に調べ、次に、数値流体力学(CFD)シミュレーションを行い、実験結果と中空螺旋状フィン付き管内の流動構造との関係を研究した。実験データから、フィンがエネルギー分離を促進し、管長を短くできることがわかった。入口空気圧が0.5MPaのとき、入口から出口までの最大温度差は62.2$^{\circ}$Cであった。レイノルズ応力モデル(RSM)乱流モデルを組み込んだCFDコードを用いて流体解析をした結果、フィン無とフィン有の場合とで淀み点の位置が大きく変わり、流動構造が全く異なることを確認した。中空螺旋状フィンによって、低温側フィン端と淀み点との間に小さな循環渦構造を持つ強い反転渦流が形成され、乱流運動エネルギーが大きな領域が生成されることによってエネルギー分離が促進されたと考えられる。

Additional file 1: Table S1. Search ranges of parameters in the GA search for each observation site. Fig. S1. Array configurations at HAK site in Hakodate city. Red, green, and blue symbols and lines correspond to L array, S array, and N array, respectively. The circles indicate the locations of sensors. The black inverted triangle represents K-NET HKD160 strong motion station. Fig. S2. Array configurations at MHR site in Mihara, Hakodate city. Red, green, and blue symbols and lines correspond to L array, S array, and N array, respectively. The circles indicate the locations of sensors. The black inverted triangle represents JMA D66 strong motion station. Fig. S3. Array configurations at KMI site in Kamiiso, Hokuto city. Red, green, and blue symbols and lines correspond to L array, S array, and N array, respectively. The circles indicate the locations of sensors. The black inverted triangle represents HKDP08 strong motion station. Fig. S4. Array configurations at OON site in Ono, Hokuto city. Red, green, and blue symbols and lines correspond to L array, S array, and N array, respectively. The circles indicate the locations of sensors. The black inverted triangle represents HKDP09 strong motion station. Fig. S5. Array configurations at NNE site in Nanae town. Red, green, and blue symbols and lines correspond to L array, S array, and N array, respectively. The circles indicate the locations of sensors. The black square represents the location of the hot-spring well (H480-017). Fig. S6. Photo of the huddle test on September 25, 2017, at Omori Park in Hakodate city. Eight blue cylindrical-shaped sensors are LE-3D/5s manufactured by Lennartz-Electronic (one was for spare, which was not used in this field work). Data loggers DATAMARK LS-8800 connected to LE-3D/5s are stored in orange boxes. Four duralumin boxes are portable all-in-one accelerographs SMAR-6A3P (three accelerometers and data logger LS-8800). Fig. S7. Results of the huddle test for LE-3D/5s sensors. (Top) Velocity waveforms of the vertical component observed by seven LE-3D/5s sensors (0.1–10 Hz). The origin time of the time axis is at 10:08:18.72 on September 25, 2017 (JST). (Bottom Left) Ensemble average of the power spectral densities of five selected time-windows of the vertical component for all seven sensors. (Bottom Right) Ensemble average of the coherences and phase differences of the vertical components for all possible combinations of the seven sensors. Fig. S8. Results of the huddle test for SMAR-6A3P seismographs. (Top) Acceleration waveforms of the vertical component observed by four SMAR-6A3P seismographs (0.1–10 Hz). The origin time of the time axis is at 10:04:56.16 on September 25, 2017 (JST). (Bottom Left) Ensemble average of the power spectral densities of five selected time-windows of the vertical component for all four sensors. (Bottom Right) Ensemble average of the coherences and phase differences of the vertical components for all possible combinations of the four sensors. Fig. S9. Comparison of the S-wave velocity model estimated by the microtremor array observation with the geological profile of nearby hot spring well (Geological Survey of Hokkaido 1995, 2004). The locations of the hot spring wells were shown in Fig. 1(a). H: Holocene, Fm: Fumizuki Formation, Tm: Tomikawa Formation, Tv: Togeshita pyroclastic rocks, Mh: Mohejigawa Formation, Td: Todagawa Formation, Hk: Hekirijigawa Formation, K: Kamiiso Group. Fig. S10. Goodness-of-Fit (GOF) scores evaluated for five frequency bands (0.05–0.1 Hz, 0.1–0.2 Hz, 0.2–0.5 Hz, 0.5–1 Hz, and 1–2 Hz) based on the GOF criterion proposed by Anderson (2004). The square, circle, and triangle correspond to NS, EW, and UD component, respectively. The number above each panel is the average of the GOF scores of all frequency bands and components. Red: This study, purple: J-SHIS V2 model.

Additional file 1: Table S1. Focal Mechanism of Two Moderate-Sized Aftershocks. Table S2. Physical Parameters in the 1D Velocity Structure Models Used for the Waveform Inversions. Figure S1. Spatiotemporal distribution of the relocated aftershocks within the three days following the Anchorage mainshock (plotted points). The large star marks the epicenter of the mainshock. Figure S2. Relocated aftershocks within the three days following the Anchorage mainshock (plotted points). a Map view. The large star marks the epicenter of the mainshock. The dashed and dotted ellipses denote the southern and northern aftershock clusters, respectively. b Cross-sectional view of the aftershocks along the linear profile C–D. The bold line indicates the slab surface. Figure S3. Weight of the smoothing constraint and rupture velocity selected by the inversion (case B). a ABIC versus the weight of smoothing constraint. b Variance reduction versus the rupture velocity. The circles denote the values selected by the inversion. Figure S4. Velocity waveforms (0.1–0.4 Hz) during two moderate-sized aftershocks. The number to the right of each waveform denotes the peak amplitude in cm/s. Figure S5. Preliminary inversion trials for different fault widths of segment S1. a Map views of the final slips. The large yellow star denotes the epicenter. b Comparison between the observed and synthetic velocity waveforms (0.05–0.4 Hz). The number to the right of each waveform denotes the peak amplitude in cm/s. The map view shows the epicenter (star) and stations (triangles). The gray dashed lines show the waveform differences. Figure S6. Slip model of the Inskin earthquake (USGS 2018). The star denotes the rupture initiation point. The inside of the black rectangle denotes the rupture area. The two purple rectangles indicate the large slip areas. The rupture area and the large slip areas were determined using the criteria of Somerville et al. (1999).

強震動予測に必要となる堆積平野の地下構造モデルの改良、高度化に資するため、石川県加賀平野南部および邑知潟平野において、微動アレイ観測および単点微動観測を実施した。得られた位相速度分散曲線およびH/Vスペクトル卓越周期の空間分布をもとに、平野内の堆積層構造の空間変化について議論するとともに、既存の地下構造モデルとの比較を行った。加賀平野において、小松周辺では手取川扇状地以北に比べて堆積層が急激に薄くなっていることが明らかとなった。邑知潟平野においては、七尾から羽咋に向かって、徐々に卓越周期が長周期化しており、堆積層厚が厚くなっていることが示唆される。Microtremor array observations and single-station microtremor observations are conducted in the Kaga plain and the Ochigata plain, Ishikawa prefecture, Japan, to improve the three-dimensional velocity structure model for strong motion prediction in this area. The lateral variation of the peak periods estimated from the H/V spectra and phase velocity estimated from the array observation are discussed in terms of three-dimensional structure of subsurface sediment layers and bedrock depth. The peak period is relatively short around Komatsu city in the southern part of the Kaga plain compared to the northern and central part of the Kaga plain, indicating the change in the bedrock depth or thickness of sediment layers, which is not well considered in the present velocity structure models. In the Ochigata plain, our observations indicate the need for improving the present model to explain that the thickness of sediment layers gradually increases along the observation line from northeast to southwest.

Microtremor H/V spectral ratio is analyzed to obtain the observational information for performance-checking and improving the three-dimensional velocity structure model of the Osaka sedimentary basin. Microtremor was observed at 100 strong motion stations in and around the Osaka basin. The observed peak period of H/V spectral ratio reflects the bedrock depth beneath the observed site. We identified areas where we need revise the model by comparing the observed H/V spectral ratios with the theoretical Rayleigh-wave R/V ratios from the present three-dimensional velocity structure models.

We estimated the predominant period of surface waves from the dispersion curves of the Love and the Rayleigh fundamental mode, calculated from 1-D verlocity structure models extracted from the Osaka basin model.The estimated predominant period is from 1 to 10 s for the Love waves and 1 to 6 s for the Rayleigh waves in the Osaka plain. The linear relationships between the predominant period of surface waves and the bedrock depth are confirmed. Predominant period is proportionality to the bedrock depth. Coefficient proportionality approximately equals 5 s/Km for Love waves and 2 s/Km for Rayleigh waves. We compared the estimated predominant periods with the observed ones at strong ground motion observation stations maintained by CEORKA (Committee of Earthquake Observation and Research in the Kansai Area)for the main shock(M_J7.4)and aftershock(M_J6.5) of the 2004 off the Kii peninsula earthquake. Except for some CEORKA sites, where the depth of the bedrock is deeper than 1.5 Km, the estimated predominant period of surface waves is consistent with the observed one. This result is the first approximation,effective for the predominant period of surface waves in the Osaka plain. However,there is a possibility of a variation of the predominant period for the surface waves coming from a different direction.