Shigeo Kimura

Time-Resolved Temperature Distribution of Icing Process of Supercooled Water in Microscopic Scale

The icing process of supercooled water is investigated in a microscope to provide further 8 understandings in an icing process in a micro scale. One question of using dual-luminescent 9 imaging method is that the luminescent probes may aggregate in the icing process, which 10 causes the signal attenuation. We monitored the luminescent outputs during the icing 11 process in a microscopic scale. It was found that the luminescent signal did not show an 12 increase during the icing process; it was actually decreased. By the ratio of the luminescent 13 output, we can obtain the temperature information from the dual-luminescent imaging. 14 Even though the signal attenuation was seen, the ratio value showed constant, which 15 supports that the temperature after the release of supercooled condition was constant. These 16 findings tell us that the luminophore aggregation may not occur during the icing process. 17

Aerodynamic characteristics of an iced cup-shaped body

The negative effects of ice accretion on wind speed measurements by a cup anemometer have been indicated by analyses of field test results and already been studied numerically and experimentally by the authors of this paper. Implementation of calculations of the dynamic behavior of a cup anemometer with or without ice was carried out employing the fictitiously altered aerodynamic characteristics of an iced or clean cup based on NACA test results for a conical cup because no information covering the aerodynamic characteristics of an iced cup had been provided up to that point. In light of the absence of solid data, wind tunnel tests of the aerodynamic characteristics of iced cup-shaped bodies were performed. Imitated ice models were built and used for the test based on test results from an icing wind tunnel test conducted separately. We found that, depending on its amount, ice accretion in dry-growth conditions results in big penalties to the aerodynamics of cup-shaped bodies, while ice deposits of wet growth cause little effect, regardless of the thickness of ice.

Hydrophobic Coating Study for Anti-icing Aircraft

Submitted for the DFD10 Meeting of The American Physical Society Hydrophobic coating study for anti-icing aircraft KATSUAKI MORITA, University of Tokyo, AKIHITO AOKI, AKIHISA KONNO, Kogakuin University, HIROTAKA SAKAUE, JAXA — Anti-icing or deicing of an aircraft is necessary for a safe flight operation. Mechanical processes, such as heating and deicer boot, are widely used. Deicing fluids, such as ethylene glycol type, are used to coat the aircraft. However, these should be coated every time before the take-off, since the fluids come off from the aircraft while cruising. We study a hydrophobic coating as a anti-icing for an aircraft. It is designed to coat the aircraft without removal. Since a hydrophobic coating prevents water by reducing the surface energy, it would be another way to prevent ice on the aircraft. We provide a temperaturecontrolled room, which can control its temperature at an icing condition (-10 to 0 degrees C). The contact angle is tested for various hydrophobic coatings. A water jet impingement on a hydrophobic-coated plate is included. The jet freezes under the icing condition. Qualitative comparison among various hydrophobic coatings as anti-icing is discussed. Katsuaki Morita University of Tokyo Date submitted: 09 Aug 2010 Electronic form version 1.4

Flow characteristics around a square cylinder with changing chamfer dimensions

It is known that for a square cylinder subjected to uniform flow, the drag force changes with the angle of attack. To clarify the flow characteristics around a square cylinder with corner cutoffs, we measured the drag coefficient and the Strouhal number for changing chamfer dimensions. We analyzed the flow around a square cylinder with corner cutoffs by applying the RNG k–ε turbulent model, and investigated the surface flow pattern using visualization by means of the oil film and mist flow method. From these results, we obtained the surface flow patterns by the oil film method and numerical analysis. The numerical results agreed well with the experimental values. The drag coefficient of the square cylinder with corner cutoffs decreased suddenly at an angle of attack of about αxa0=xa00°–xa010° when compared with the drag coefficient for a square cylinder. The minimum value of the drag coefficient for the square cylinder with corner cutoffs decreased by about 30% compared with that for the square cylinder. The drag coefficient of the square cylinder with 10% corner cutoffs was found to be smallest, since the wake area of this square cylinder was smaller compared with that of the other square cylinder.Graphical Abstract

Mid-infrared sensing waveguides embedded in silica glass: Detection of water phase and ice microstructure in harsh-environments

The development of mid-infrared (λ∼3–20 μm) integrated optical sensors has accelerated within the last years. The main driving interest is the potential of using photonic integrated elements capable of direct interaction with biomolecules and chemicals through their ground molecular vibrational modes, so that resonance fingerprints are exploited for novel sensor industrial applications. State-of-the-art ultrahigh-sensitivity photonic sensing schemes rely on exposing the evanescent field of tightly confined light to the environment. Yet these devices are extremely fragile, and any surface modification or damage entails irreversible sensor malfunction. Since adding a protective layer disables these sensors, there exists a technology gap for highly-sensitive harsh-environment resistant surface photonic sensors. Here we propose the use of mid-infrared waveguide sensors which exploit vibrational resonance-driven directional coupling effects besides absorption, so that waveguide sensing elements can be buried (∼1–10 μm) and resist systematic exposure to industrial environments without failure.

Experimental Investigation of a Single Droplet on a Superhydrophobic Coating in Icing Wind Tunnel for the Development of Ice-Protection System

Advanced deand anti-icing method using a combination of heating and superhydrophobic coating has been proposed as an approach to the demand for saving energy consumption on wing ice-protection system. To understand the relationship between shedding droplet and airflow speed as one of the removal process of water sticking on the superhydrophobic coating surface, we measured shedding droplet size on a flat plate sprayed with a superhydrophobic coating exposed to the airflow up to 60 m/s. Our proposed model describing the shedding droplet also estimated the droplet size in airflow of over 60 m/s. It was found that a shedding droplet diameter decreased as the airflow speed increased. It tells us that a small droplet remaining on surface needs a higher speed to remove. For an efficient ice prevention, we suggest that it would be better to have a droplet growth providing enough droplet size to be removed from the surface.

Behavior of a Small Water Droplet on Superhydrophobic Coating and Heating Surface in Cold Environment

A new ice protection method has been paid attention that uses a combination of electrothermal heater and superhydrophobic coating. In this method, a heater supports to remove a supercooled water droplet from a superhydrophobic coating that prevents from icing. However, an efficient temperatures of the heater nor the droplet are unknown. In this paper, we varied the heating temperature of the superhydrophobic coating as well as the droplet temperature to understand the behavior of the droplet on the coating. A sliding angle was measured in an icing environment. This experimental investigation will give us further understandings to create an efficient operation of the ice-ptotection method. It was found that the temerature difference instead of the absolute temperatures of the coating and droplet is important to remove a droplet from the coating.

Study of Icing Process using Dual-Luminescence Imaging for Aircraft-Icing Prevention

A hydrophobic coating has been paid attention as an ice-prevention coating on an aircraft surface. The icing process of a supercooled water droplet on the coating surface will give great insights into the further development of the ice-prevention coating. To understand the icing process, the time-resolved temperature distributions of the droplet will be a key factor. A dual-luminescent imaging is introduced and applied to capture the temperature distributions of the droplet on a hydrophobic surface. This paper describes the temperaturecapturing method of the dual-luminescence imaging, the characterizations of the imaging system, and the temperature measurements. The temperature measurements include the time-resolved temperature distributions of the droplet under static and dynamic conditions.

Development and Application of Dual-Luminescence Imaging for Capturing Supercooled-Water Droplet under Icing Conditions

We introduce a dual-luminescent imaging to capture the temperature distribution of 9 supercooled-water droplets for understanding the icing process. Two luminescent probes of 10 coumarin and rhodamine derivatives are used to obtain the temperature-independent and 11 temperature-dependent images. Both images are simultaneously acquired by a high-speed 12 color camera. The temperature calibration of the developed system shows the temperature 13 sensitivity of -5.4 %/°C. This system captures the time-resolved staticand dynamic-icing 14 processes of a supercooled-water droplet under the icing conditions. 15

Visualization of snowdrift around buildings of an Antarctic base through numerical simulation

The removal of snowdrifts resulting from snowstorms is often a physically intensive work in Antarctica. Therefore, it is important to consider snowdrift around buildings in construction planning. In this study, we predicted snowdrift using a small experimental facility and existing numerical-analysis software that can be easily implemented. First, the snow cover around a cube model resulting from a snowstorm was calculated through numerical analysis. And the validity of numerical analysis was examined. To consider the effect of the form of a proposed Antarctic building on snowdrift, the snowdrift around buildings of an Antarctic base was then predicted by numerical analysis. As a result, it is thus expected that work involved in removing snowdrifts can be reduced through the appropriate design of curved-roof Antarctic buildings employing numerical analysis.Graphical Abstract