低速におけるカーボンナノチューブ感温塗料を用いた非定常流れ場計測

Tohoku University博士（工学）要約のみthesi

Data-Driven Optimal Sensor Placement for High-Dimensional System Using Annealing Machine

We propose a novel method for solving optimal sensor placement problem for high-dimensional system using an annealing machine. The sensor points are calculated as a maximum clique problem of the graph, the edge weight of which is determined by the proper orthogonal decomposition (POD) mode obtained from data based on the fact that a high-dimensional system usually has a low-dimensional representation. Since the maximum clique problem is equivalent to the independent set problem of the complement graph, the independent set problem is solved using Fujitsu Digital Annealer. As a demonstration of the proposed method, the pressure distribution induced by the K\'arm\'an vortex street behind a square cylinder is reconstructed based on the pressure data at the calculated sensor points. The pressure distribution is measured by pressure-sensitive paint (PSP) technique, which is an optical flow diagnose method. The root mean square errors (RMSEs) between the pressure measured by pressure transducer and the reconstructed pressures (calculated from the proposed method and an existing greedy method) at the same place are compared. As the result, the similar RMSE is achieved by the proposed method using approximately 1/5 number of sensor points obtained by the existing method. This method is of great importance as a novel approach for optimal sensor placement problem and a new engineering application of an annealing machine

Clustering Method for Time-Series Images Using Quantum-Inspired Computing Technology

Time-series clustering serves as a powerful data mining technique for time-series data in the absence of prior knowledge about clusters. A large amount of time-series data with large size has been acquired and used in various research fields. Hence, clustering method with low computational cost is required. Given that a quantum-inspired computing technology, such as a simulated annealing machine, surpasses conventional computers in terms of fast and accurately solving combinatorial optimization problems, it holds promise for accomplishing clustering tasks that are challenging to achieve using existing methods. This study proposes a novel time-series clustering method that leverages an annealing machine. The proposed method facilitates an even classification of time-series data into clusters close to each other while maintaining robustness against outliers. Moreover, its applicability extends to time-series images. We compared the proposed method with a standard existing method for clustering an online distributed dataset. In the existing method, the distances between each data are calculated based on the Euclidean distance metric, and the clustering is performed using the k-means++ method. We found that both methods yielded comparable results. Furthermore, the proposed method was applied to a flow measurement image dataset containing noticeable noise with a signal-to-noise ratio of approximately 1. Despite a small signal variation of approximately 2%, the proposed method effectively classified the data without any overlap among the clusters. In contrast, the clustering results by the standard existing method and the conditional image sampling (CIS) method, a specialized technique for flow measurement data, displayed overlapping clusters. Consequently, the proposed method provides better results than the other two methods, demonstrating its potential as a superior clustering method.Comment: 13 pages, 4 figure

A Computational Approach To Predict Warp Of Sawn Lumber Due To Residual Growth Stress In A Log

A tree generates a complicated stress distribution inside the stem during its formation, which is called 'residual growth stress (RGS)'. The RGS often induces warp in a sawn lumber such as bow, crook, and other deformation, which causes severe losses of materials and benefits in the sawmill industry. Generally, warp becomes more serious in the lumber 'without pith' than in the lumber 'with pith'. In Japan, 50% of conifer plantations are ready to produce large-diameter logs of which diameter is more than 30 cm. The use of those logs inevitably leads to the production of the lumber 'without the pith', so we are concerned about the problems due to lumber warp in future sawmill industry using largediameter logs. Based on those practical background, this study presents a computational procedure to predict warp of the squared lumber, such as a beam, a bearer, and so forth, when those lumbers are sawn from the log and/or the thick plank. Using the derived procedure, 2-D patterns of the RGSs in the sawn lumbers and their changes during sawing processes are simulated. Simulated results will be experimentally verified by measuring the warp of the sawn lumber, as well as by measuring the RGS distributions in a log

Influence of Formulations on Characteristics of Ruthenium-Based Temperature-Sensitive Paints

Temperature-sensitive paint (TSP) can optically measure a global temperature distribution using a thermal quenching of dye molecules. The TSP measurement is often used in wind tunnel tests to measure the temperature and flow fields in the aerodynamic field. The measurement accuracy is affected by the characteristics of TSP, such as temperature sensitivity, pressure dependency, luminescent intensity, photostability, and surface condition. The characteristics depend on the formulation of TSP. This study investigates the characteristics of the TSP using dichlorotris (1,10-phenanthroline) ruthenium(II) hydrate (Ru-phen). We compare the characteristics of TSPs using different polymers, solvents, and dye concentrations. The TSPs using polyacrylic acid as a polymer shows linear calibration curves, high luminescent intensity, high photostability, and smooth surface. On the other hand, the TSPs using polymethyl methacrylate have nonlinear calibration curves, low luminescent intensity, strong photodegradation, and a rough surface

Measurement of Boundary Layer Transition on Oscillating Airfoil using cntTSP in Low-Speed Wind Tunnel

cntTSP is a flow visualization technique combining temperature-sensitive paint (TSP) and carbon nanotube (CNT). TSP is a sprayable temperature sensor, and CNT is used as a thin inner electric heater for TSP. The cntTSP technique allows visualizing a dynamic boundary layer transition on a moving airfoil in the low-speed condition. In this study, cntTSP was used to visualize a movement of the dynamic boundary layer transition on a pitch-oscillating airfoil in the low-speed wind tunnel. The transition position was evaluated by using a heat transfer coefficient. At a high reduced frequency, the detected transition positions were different between pitching-up and pitching-down procedure, and hysteresis was observed. Moreover, we observed not only the unsteadiness of the aerodynamic phenomenon due to the pitch-oscillation but also the thermal delay due to the response time of the cntTSP

Investigation of Formulations on Pyrene-Based Anodized-Aluminum Pressure-Sensitive Paints for Supersonic Phenomena

Pressure-sensitive paint (PSP) is an optical sensor that can measure global pressure distribution by using the oxygen quenching of dye molecules. In particular, anodized aluminum pressure-sensitive paint (AA-PSP) exhibits a fast time response. AA-PSP has been used in unsteady measurements at supersonic and transonic speeds, such as on the surface of a transonic free-flying sphere or the wall of a shock tube when the shock wave passes. To capture such ultrafast phenomena, the frame rate of the camera must be sufficiently fast, and the exposure time must be sufficiently short. Therefore, it is desirable that the AA-PSP exhibits bright luminescence, high-pressure sensitivity, and fast response time. This study focused on pyrene-based AA-PSPs and investigated their characteristics, such as luminescence intensity and pressure sensitivity, at different anodization times, dipping solvents, and dipping concentrations. Furthermore, a time-response test using a shock tube was conducted on the brightest AA-PSP. Consequently, the time for a 90% rise in pressure was 2.2 μs

Evaluation of cntTSP for Boundary Layer Transition Detection in Low Speed Flow

Recently, low-Reynolds-number flight vehicles have attracted attention such as a micro air vehicle (MAV) and a Mars airplane. For the experiments conducted at lowReynolds-number conditions under the atmosphere, the flow of the wind tunnel must be low speed. It is difficult to measure the pressure field on the wing surface using pressuresensitive paint (PSP) under the low-speed conditions because the pressure fluctuation on the wing surface is very small. The TSP can be used for the boundary layer transition detection even in low-speed conditions. The visualization principle of the TSP measurement is based on the temperature fluctuation caused by the different heat transfer coefficient in the laminar and turbulent flows. When the model surface is heated, the heat transportation is facilitated and the temperature fluctuation on the model surface is increased. A cntTSP is an advanced TSP technique which uses carbon nanotubes (CNT) as a thin electric inner heater for the TSP. The CNT layer can continue to supply constant heat to the model surface even during the measurement. Therefore, the cntTSP allows the dynamic visualization on a moving airfoil, which requires a long-time measurement. In this study, the cntTSP was applied to an oscillating airfoil in order to visualize the dynamic boundary layer transition in the low-speed condition. We succeeded to detect the moving boundary layer transition positions on the oscillating airfoil in the wind tunnel test. A hysteresis of the boundary layer transition position was observed in pitching-up and pitching-down procedures. It was assumed that the hysteresis of the transition position was caused by the unsteadiness of the aerodynamic phenomenon. However, it was also indicated the hysteresis includes the delay of the time response of cntTSP at the same time. Thus, we conclude that the time response is a technical problem of cntTSP and the evaluation of the time response is required

Carbon Nanotube TSP technique in a pitch-sweep wind tunnel test

The visualization of the temperature distribution on a whole wind tunnel model is possible using Temperature Sensitive Paint (TSP). TSP measurement method is based on the dependence of the emission intensity or decay time of its luminescence on the temperature, caused by thermal quenching. One major area of interest for such technique is the examination of the laminar-to-turbulent boundary-layer transition behavior on wind tunnel models. However, the naturally established adiabatic wall temperature difference caused by the recovery process is typically too small to be detected with TSP, especially in low-speed tests. Therefore, the TSP technique requires an increase of the adiabatic wall temperature difference for transition detection measurements. The basic working principle of this approach is the imposition of a heat flux between the flow and the surface of the wind tunnel model. In the previous work carbon nanotubes (CNT) were presented as a source for electrical heating in order to generate temperature differences between laminar and turbulent boundary layers which are sufficient for the TSP technique. CNT has several desirable properties: for example a very high electric conductivity, and its ease of applicability as a coating with a thickness of few micrometers, which enables a successful combination with TSP for transition detection measurements in the wind tunnel environment (called cntTSP). One big advantage of cntTSP is that the boundary-layer transition can be detected without changing the flow parameters. In addition, based on its capability of constant model surface heating, the cntTSP has a potential to be used for the dynamic visualization of boundary-layer transition, leading to the application of cntTSP in continuous model angle-sweep tests. The use of cntTSP in the angle-sweep tests is strongly desirable by the industrial partners in order to improve the data productivity of wind tunnel tests. This work reports investigation of the transition detection methods in pitch-sweep wind tunnel tests for improving the reliability and the data productivity with various measurement and data reduction methods