Takayuki Nagata

Ensemble-Averaged Adjoint Sensitivity Analysis for Weather Modification: Dataset and Code for the July 2018 Western Japan Heavy Rainfall WRF simulation

Shan Jiang, Takayuki Nagata, Masahito Watanabe, Junshi Ito et autres

This repository includes a modified WRF source code and scripts for case preparation and post-processing for the ensemble-averaged adjoint sensitivity analysis applied to numerical simulation of precipitation control. Version 0.2.0 comprises the original dataset archive and a supplementary archive containing the additional …

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Development of dynamic calibration system for high-frequency response evaluation of fast pressure-sensitive paint using cavity-induced flapping jet

Di Kong, Takayuki Nagata, Taku Nonomura

A high-frequency dynamic calibration system for pressure-sensitive paint (PSP) was developed using cavity-induced jets. The dominant frequency for dynamic calibration was adjusted to the range of 9–16 kHz by scaling the cavity. The dominant flapping frequencies corresponding to different cavity lengths were …

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Wall-Resolved LES Evaluation of Mach Number and Angle of Attack Effects on the Flow Field around NACA Airfoils at Low Reynolds Numbers under Compressible Conditions

T. Uchida, Takayuki Nagata, Taku Nonomura

We performed wall-resolved large-eddy simulations (LES) to investigate the effects of Mach number, angle of attack, and airfoil thickness on the flow field and aerodynamic characteristics of NACA 4-digit airfoils. The Reynolds number was set to 2.3 × 10^4, and the angle …

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Experimental analysis of three-dimensional coherent structures associated with the screech-resonance mechanism in underexpanded jets: Spatiotemporal super-resolution and dynamic-mode-decomposition analyses of density fields

Chungil Lee, Yuta Ozawa, Takayuki Nagata, Taku Nonomura

Three-dimensional (3D) coherent structures associated with screech tones, along with their correlations and resonance mechanisms, were investigated in underexpanded jets at a nozzle pressure ratio of 2.52 using the 3D spatiotemporal super-resolution reconstruction (3DSSR) method and dynamic mode decomposition analysis. Both approaches …

Anomaly Detection Using Data-Driven Sparse Sensors: Combination of Modal Representation and Sensor Optimization for Sensing of Targeted Variable

Yuji Saito, Ryoma Inoba, Yasuo Sasaki, Takayuki Nagata et autres

We propose an anomaly detection method based on modal representation and a noise-robust sparse sensor position optimization method. We focus on the detection of anomalies in global sea surface temperature field observations indicative of El Niño and La Niña phenomena. For evaluation, …

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Schlieren visualization and drag measurement on compressible flow over a circular cylinder at Reynolds number of $$\mathcal {O}(10^2)$$

Takayuki Nagata, Tsuyoshi Shigeta, M. Kasai, Taku Nonomura

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Fast Data-Driven Greedy Sensor Selection for Ridge Regression

Yasuo Sasaki, Keigo Yamada, Takayuki Nagata, Yuji Saito et autres

We propose a data-driven sensor-selection algorithm for accurate estimation of the target variables from the selected measurements. The target variables are assumed to be estimated by a ridge-regression estimator, which is trained based on the data. The proposed algorithm greedily selects sensors …

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Unsteady flow field behind levitated short-finite circular cylinder with angle of attack

Sho Yokota, Takayuki Nagata, Taku Nonomura

Flow field in the near wake of a short-finite circular cylinder at $L/D=1.0$ with an angle of attack between 0 $^\circ$ –15 $^\circ$ , where the transition from the non-reattaching flow to the reattaching flow appears, is investigated in wind tunnel tests …

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Analysis of Waves Associated With Screech Resonance Mechanism Using Double-Pulsed 3D-BOS Measurement

Chungil Lee, Yuta Ozawa, Takayuki Nagata, Taku Nonomura

Waves associated with screech resonance mechanism of underexpanded jets are investigated using the double-pulsed three-dimensional background-oriented schlieren (3D-BOS) measurement. The nozzle pressure ratio of 2.52 is employed. The microphone measurement is also performed, and two peaks corresponding to screech frequencies of the …

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Switch of the Azimuthal Structure of an Underexpanded Jet in the Screech B Mode

Christopher H. T. Lee, Yuta Ozawa, Takayuki Nagata, Taku Nonomura

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Actuator Placement Optimization in a Linear Impulsive Control System by Determinant-Based Greedy Algorithm

Masahito Watanabe, Yasuo Sasaki, Takayuki Nagata, Keigo Yamada et autres

In this paper a numerical algorithm to optimize actuator locations in a linear impulsive control system is developed so that the terminal output could be varied efficiently under various initial conditions. The core innovation of our method is that the sensitivity of …

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Discrete element method-based simulation system for predicting natural stone evacuation pathways in patients with urolithiasis

Naoaki OKABAYASHI, Katsuki HIRAI, Takayuki Nagata, Kazuhide Makiyama et autres

Urolithiasis is a globally prevalent disease with high incidence and recurrence rates and is often accompanied by severe pain. Its ideal treatment is spontaneous stone passage, avoiding the invasiveness associated with surgery. However, the mechanisms underlying spontaneous stone passage remain unclear. Therefore, …

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