Simulation and analysis of dynamic heating in the ultrafast aircraft thermometer measurements (original) (raw)
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A New Ultrafast Thermometer for Airborne Measurements in Clouds
Journal of Atmospheric and Oceanic Technology, 1997
A new aircraft device for measuring temperature in clouds is described. Its sensor is a resistance thermometer made of platinum-coated tungsten wire 5 mm long and 2.5 m in diameter. The sensor is located on a rotatable vane behind a thin rod aimed at protecting it against the impact of cloud droplets, which according to limited experience gathered until now seems to be sufficiently effective as an antiwetting protection for the speeds of motorgliders. Contrary to the massive housings usually adopted in other constructions, the rod creates only negligible disturbances in the thermodynamic properties of the ambient air. The time constant of the sensor is of the order 10 Ϫ4 s, which permits measurements of temperature in clouds with a resolution of a few centimeters, depending on aircraft velocity. The thermometer was tested in a wind tunnel, and on an Ogar motorglider and a Do-228 aircraft. Its present version performs fairly well at low airspeeds of up to about 40 m s Ϫ1 . For faster aircraft further improvements seem necessary. The paper presents a detailed description of the instrument, discussion of test results, and examples of centimeter-scale features of temperature fields in clouds measured with the thermometer.
Measurement of Air Temperature Fluctuations with Thermocouples
Equations for determining the radiant heating and time constant of small thermocouples used for air temperature measurement are presented. Calculated and measured values are compared for 0.0025, 0.0127, and 0.0508 cm diameter copper-constantan thermocouples exposed to direct sunlight. The largest thermocouple gives measured temperatures that are approximately 1.3C higher than air temperature, and the smallest thermocouple reads about 0.3C above air temperature when they are exposed to direct solar radiation. In direct sunlight and for a range of wind speed of 100 to 500 cm sec-1 the temperature is reduced by 0.8 and O.1C for the largest and smallest thermocouples, respectively. The effects of two types of aspirated thermoshields on temperature fluctuations measured inside the shield with the 0.0025 cm thermocouples were determined. Thermoshield design was shown to be critical in temperature fluctuation measurement.
Temperature measurements in clouds on a centimetre scale Preliminary results
1996
Preliminary results of the temperature measurements in Cumulus mediocris clouds with a new ultra-fast airborne thermometer installed on a motor-glider are presented. The time constant of the thermometer is about 2 × 10 _4 s but due to limitations of the recorder the data were conditioned with the use of a 300 Hz low-pass filter and sampled with 999 Hz rate, giving spatial resolution of 3 cm at 30 m/s cruising speed. Records taken whilst penetrating various parts of Cumulus clouds on 23 and 25 August 1994 in the vicinity of Warsaw show a number of unexpected features such as single and multiple sharp jumps of temperature over layers only a few centimetres thick. Measurements of this kind are throwing a new light on the process of mixing in convective clouds.
Journal of Atmospheric and Oceanic Technology, 2005
We modeled damaged-irradiated carbon plasma facing component PFCs by graphite surfaces with vacancies. We combined theoretical and experimental investigations with a view to building tools to make a better assignment of the observed defects from the scanning tunneling microscope (STM) images. The theoretical part of this work is based on periodic density functional theory calculations. The electronic structure is calculated and the density of state along with the electronic density near the Fermi level are plotted. STM images are further simulated and their features are interpreted. On the experimental side, we performed scanning tunneling microscopy (STM) imaging at low bias voltage in order to probe the electronic modifications of the graphite surface induced either by H + (or D + ) ion bombardment and/or atomic H (respectively D) adsorption. A connection between STM images and the reactivity of defective graphite surfaces towards H is also proposed.
Atmospheric Measurement Techniques, 2013
A modified UFT-M version of the ultrafast airborne thermometer UFT, aimed at in-cloud temperature measurements, was designed for the Physics of Stratocumulus Top (POST) field campaign. Improvements in its construction resulted in the sensor's increased reliability, which provided valuable measurements in 15 of the 17 flights. Oversampling the data allowed for the effective correction of the artefacts resulting from the interference with electromagnetic transmissions from on-board avionic systems and the thermal noise resulting from the sensor construction. The UFT-M records, when averaged to the 1.4 and 55 m resolutions, compared to the similar records of a thermometer in a Rosemount housing, indicate that the housing distorts even lowresolution airborne temperature measurements. Data collected with the UFT-M during the course of POST characterise the thermal structure of stratocumulus and capping inversion with the maximum resolution of ∼ 1 cm. In this paper, examples of UFT-M records are presented and discussed.
2015 Academic High Altitude Conference, 2015
In this paper we present additional results from our ongoing research effort to characterize the thermal wake that trails below ascending latex weather balloons on flights into the stratosphere; a wake which interferes with the ability of temperature sensors in payload boxes hanging from the balloon (and hence enveloped by the wake) to correctly measure the ambient temperature of the atmosphere through which the balloon is ascending. A "wake boom" is used to measure temperature variations up to 1.5m horizontally from varying distance directly below the neck of the balloon. Results to date agree with the literature that especially above the tropopause the thermal wake is warmer than the ambient air during daytime ascents, due to solar radiation warming the balloon skin, but colder than ambient air during nighttime ascents, due to adiabatic cooling of the gas inside the balloon (which also occurs in the daytime, but is smaller than the daytime warming effect). In particular, we report on thermal wake characterization using (Neulog) thermocouple sensors, as compared to (HOBO) thermistors and (Arduino-logged) DS18B20 digital temperature sensors. We also present additional results from X-shaped 2-dimensional wake booms or "X-Booms" which allow us to compare wake temperatures on the sun side versus the shade side of the balloon, looking for asymmetries in the horizontal temperature profile.
Thermal analysis of anti-icing systems in aeronautical velocity sensors and structures
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2016
This work reviews theoretical-experimental studies undertaken at COPPE/UFRJ on conjugated heat transfer problems associated with the transient thermal behavior of heated aeronautical Pitot tubes and wing sections with anti-icing systems. One of the main objectives is to demonstrate the importance of accounting for the conduction-convection conjugation in more complex models that attempt to predict the thermal behavior of the anti-icing system under adverse atmospheric conditions. The experimental analysis includes flight tests validation of a Pitot tube thermal behavior with the military aircraft A4 Skyhawk (Brazilian Navy) and wind tunnel runs (INMETRO and NIDF/COPPE/UFRJ, both in Brazil), including the measurement of spatial and temporal variations of surface temperatures along the probe through infrared thermography. The theoretical analysis first involves the proposition of an improved lumped-differential model for heat This work is dedicated to the 228 victims of the AF447 flight and their families. This hard lesson will hopefully affect somehow technology development protocols, in a progressively more competitive world, reminding us all that there is no acceptable, sustainable, and safe technological development without a supporting extensive scientific analysis.
International Journal of Heat and Fluid Flow, 2000
Simultaneous measurements of two velocity components and temperature are performed combining Laser Doppler Anemometry (LDA) and cold wire thermometry. LDA is a common technique suitable for velocity measurements in turbulent jets where strong turbulence intensities and reverse¯ows may exist, but temperature measurements in association with LDA are dicult because the ®ne wire response is altered by the seeding deposit, so that the wire must be regularly cleaned. Results reported herein concern velocity±temperature correlations, as well as velocity and temperature marginal probability density functions and temperature (or velocity) probability density functions conditioned by the sign of the velocity (or temperature)¯uctuation. The evolution of these various quantities is analysed in order to better understand the mixing properties in the near-®eld of a turbulent jet where the initial conditions still have a strong in¯uence. It is shown that, while the velocity ®eld tends to relax rather quickly (within a few nozzle diameters from the exit) to almost gaussian statistics, the temperature properties are still signi®cantly skewed towards the hot jet exit temperature until xaD j about 7±8. On the contrary, the signature of the cold ambient temperature vanishes rather quickly. Ó 2000 Elsevier Science Inc. All rights reserved.
Aero-thermal analysis of shielded fine wire thermocouple probes
International Journal of Thermal Sciences, 2013
Thermocouple probes for high accuracy gas temperature measurements require specific designs optimized for the application of interest and precise characterization of the uncertainty. In the present investigation a numerical procedure is proposed that outperforms previous experimental approaches to analyze the thermocouple response and the different sources of temperature error. The results presented from conjugate heat transfer simulations on different shielded thermocouples, provide information of the influence of the design parameters on the different error sources. These outcomes should help experimentalists to better design future instrumentation.