Dual-luminophore pressure-sensitive paint measurement using three-gate lifetime method with photodegradation correction.

In this paper, we propose a photodegradation correction method for the dual-luminophore pressure-sensitive paint (PSP) measurement using lifetime-based imaging, which was proposed for correction of the temperature-induced error but has suffered from photodegradation in the previous studies. We introduced a parameter that characterizes the photodegradation of a dual-luminophore PSP as the intensity ratio between the two luminophores. The changes in the calibration coefficients for the pressure and the temperature due to photodegradation were corrected based on this parameter.

Efficient Sensor Node Selection for Observability Gramian Optimization.

Optimization approaches that determine sensitive sensor nodes in a large-scale, linear time-invariant, and discrete-time dynamical system are examined under the assumption of independent and identically distributed measurement noise. This study offers two novel selection algorithms, namely an approximate convex relaxation method with the Newton method and a gradient greedy method, and confirms the performance of the selection methods, including a convex relaxation method with semidefinite programming (SDP) and a pure greedy optimization method proposed in the previous studies. The matrix determinant of the observability Gramian was employed for the evaluations of the sensor subsets, while its gradient and Hessian were derived for the proposed methods.

First lift-off and flight performance of a tailless flapping-wing aerial robot in high-altitude environments.

Flapping flight of animals has captured the interest of researchers due to their impressive flight capabilities across diverse environments including mountains, oceans, forests, and urban areas. Despite the significant progress made in understanding flapping flight, high-altitude flight as showcased by many migrating animals remains underexplored. At high-altitudes, air density is low, and it is challenging to produce lift.

Model position sensing method for low fineness ratio models in a magnetic suspension and balance system.

A new model-position-sensing method for the levitation of models with a low fineness ratio (ratio of the longitudinal length to the diameter) in a magnetic suspension and balance system (MSBS) is proposed. MSBS is an ideal model-support device for wind-tunnel testing, which enables the study of flow fields around blunt bodies without flow disturbances introduced by mechanical support devices, with the aerodynamic forces determined from the magnetic forces using a pre-calibrated relationship. The new method allows wind tunnel experiments without mechanical supports with a low fineness ratio model.

Photostability Enhancement of Dual-Luminophore Pressure-Sensitive Paint by Adding Antioxidants.

Antioxidants were applied to a dual-luminophore pressure-sensitive paint (PSP), and the effects on photodegradation caused by exposure to excitation light were studied. Three types of antioxidants that are commonly used for the photostability enhancement of polymers were added to a dual-luminophore PSP, and degradation rates and pressure/temperature sensitivities were investigated by coupon-based tests. One-hour-long aging tests were performed in a pressure chamber with a continuous excitation light source under dry air and argon atmospheres at 100 kPa and 20 °C.

Practical Fast-Response Anodized-Aluminum Pressure-Sensitive Paint Using Chemical Adsorption Luminophore as Optical Unsteady Pressure Sensor.

We developed and evaluated an anodized-aluminum pressure-sensitive paint (AA-PSP) with new formulations of free-base porphyrin, H2TCPP, as an optical unsteady pressure sensor. The luminophore H2TCPP has quite a short fluorescent lifetime (2.4 ns on the condition of the AA-PSP).

Markerless Image Alignment Method for Pressure-Sensitive Paint Image.

We propose a markerless image alignment method for pressure-sensitive paint measurement data replacing the time-consuming conventional alignment method in which the black markers are placed on the model and are detected manually. In the proposed method, feature points are detected by a boundary detection method, in which the PSP boundary is detected using the Moore-Neighbor tracing algorithm. The performance of the proposed method is compared with the conventional method based on black markers, the difference of Gaussian (DoG) detector, and the Hessian corner detector.

Computational study on aeroacoustic fields of a transitional supersonic jet.

Aeroacoustic fields of a supersonic free jet at the Mach and Reynolds numbers of 2.1 and 70 000, respectively, of the transitional conditions are computationally investigated by large-eddy simulations. The supersonic transitional jets of different shear layer thicknesses without disturbances and those of the fixed shear layer thickness with disturbances are computationally investigated, and the effects of the shear layer thickness and the disturbance are discussed.

Frequency Response of Pressure-Sensitive Paints under Low-Pressure Conditions.

The characteristics of fast-response pressure-sensitive paints (PSPs) in low-pressure conditions were evaluated. Three representative porous binders were investigated: polymer-ceramic PSP (PC-PSP), anodized-aluminum PSP (AA-PSP), and thin-layer chromatography PSP (TLC-PSP). For each PSP, two types of luminophores, Pt(II) meso-tetra (pentafluorophenyl) porphine (PtTFPP) and tris(bathophenanthroline) ruthenium dichloride (Ru(dpp)3), were used as sensor molecules.

Effect of Oxygen Mole Fraction on Static Properties of Pressure-Sensitive Paint.

The effects of the oxygen mole fraction on the static properties of pressure-sensitive paint (PSP) were investigated. Sample coupon tests using a calibration chamber were conducted for poly(hexafluoroisopropyl methacrylate)-based PSP (PHFIPM-PSP), polymer/ceramic PSP (PC-PSP), and anodized aluminum PSP (AA-PSP). The oxygen mole fraction was set to 0.

Characteristic Evaluation of Chameleon Luminophore Dispersed in Polymer.

A temperature-sensitive paint (TSP) using a chameleon luminophore [ Tb 0 . 99 Eu 0 . 01 ( hfa ) 3 ( dpbp ) ] n is proposed.

Extended-Kalman-filter-based dynamic mode decomposition for simultaneous system identification and denoising.

A new dynamic mode decomposition (DMD) method is introduced for simultaneous system identification and denoising in conjunction with the adoption of an extended Kalman filter algorithm. The present paper explains the extended-Kalman-filter-based DMD (EKFDMD) algorithm which is an online algorithm for dataset for a small number of degree of freedom (DoF). It also illustrates that EKFDMD requires significant numerical resources for many-degree-of-freedom (many-DoF) problems and that the combination with truncated proper orthogonal decomposition (trPOD) helps us to apply the EKFDMD algorithm to many-DoF problems, though it prevents the algorithm from being fully online.

Evaluation of the Characteristics and Coating Film Structure of Polymer/Ceramic Pressure-Sensitive Paint.

Polymer/ceramic pressure-sensitive paint (PC-PSP), which incorporates a high percentage of particles in the binder layer, is proposed in order to improve the characteristics of PSP. The procedure for embedding particles into the binder layer was modified. In the conventional procedure, dye is adsorbed onto a polymer/ceramic coating film (denoted herein as a dye-adsorbed (D-adsorbed) PSP).

Linear least-squares method for global luminescent oil film skin friction field analysis.

A data analysis method based on the linear least-squares (LLS) method was developed for the extraction of high-resolution skin friction fields from global luminescent oil film (GLOF) visualization images of a surface in an aerodynamic flow. In this method, the oil film thickness distribution and its spatiotemporal development are measured by detecting the luminescence intensity of the thin oil film. From the resulting set of GLOF images, the thin oil film equation is solved to obtain an ensemble-averaged (steady) skin friction field as an inverse problem.