Reconstructed Temperature Field Research Articles

A statistical\u2013dynamical downscaling methodology for the urban heat island applied to the EURO-CORDEX ensemble

Regional Climate Models (RCMs) are the primary climate information available to public stakeholders and city-planners to support local adaptation policies. However, with resolution in the order of ten kilometres, RCMs do not explicitly represent cities and their influence on local climate (e.g. Urban Heat Island; UHI). Downscaling methods are required to bridge the gap between RCMs and city scale. A statistical–dynamical downscaling methodology is developed to quantify the UHI of the city of Paris (France), based on a Local Weather Types (LWTs) classification combined with short-term high-resolution (1-km) urban climate simulations. The daily near-surface temperature amplitude, specific humidity, precipitation, wind speed and direction simulated by the RCMs are used for the LWTs attribution. The LWTs time series is associated to randomly selected days simulated with the mesoscale atmospheric model Meso-NH coupled to the urban canopy model Town Energy Balance to calculate the UHI corresponding to the successive LWTs. The downscaling methodology is applied to the EURO-CORDEX ensemble driven by the ERA-Interim reanalysis, and evaluated for the 2000–2008 period against station observations and a 2.5-km reanalysis. The short-term dynamical simulations slightly underestimate and overestimate near-surface minimum and maximum air temperature respectively, but capture the UHI intensity with biases in the order of a tenth of a degree. RCMs show significant differences in the variables used for the LWTs attribution, but the seasonal LWT frequencies are captured. Consequently, the reconstructed temperature fields maintain the small biases of the Meso-NH simulations and the statistical–dynamical downscaling greatly improves the UHI compared to the raw data of RCMs.

Projecting Three‐Dimensional Ocean Thermohaline Structure in the North Indian Ocean From the Satellite Sea Surface Data Based on a Variational Method

AbstractThis study uses a variational method combined with satellite observations to reconstruct three‐dimensional temperature and salinity profiles for the Northern Indian Ocean. Sensitivity experiments show that sea surface temperature dominantly improve the temperature reconstruction of upper 100 m; sea surface salinity determines salinity estimation in the upper 100 m; sea surface height anomaly dominates the reconstruction of thermocline. The reconstructed temperature fields can be greatly improved in the thermocline by removing barotropic signal from the altimeter sea surface height data through a linear regression method. Ocean reanalysis and in situ temperature and salinity data are used to evaluate the results of reconstruction. Comparing with Simple Ocean Data Assimilation (SODA) in 2016, the spectral correlation between the reconstruction and the SODA density anomalies show that the reconstruction fields can retrieve mesoscale and large‐scale signals better. Moreover, the reconstruction salinity is much more accurate than SODA salinity in the upper ocean over the Bay of Bengal (BoB). Compared with CTD section observations, the reconstruction fields can capture the mesoscale eddy structure in the Arabian Sea and BoB well, respectively. The long time series of reconstruction along Argo trajectory shows that the reconstruction fields can better reproduce the observed intraseasonal oscillations of thermocline/halocline in the BoB. Compared with the World Ocean Atlas 2013 climatology, the reconstruction fields can better characterize upper ocean water mass variability.

Estimation of moving heat source for an instantaneous three-dimensional heat transfer system based on step-renewed Kalman filter

Inverse estimation of moving heat source is a common issue in many fields. A real-time method based on Kalman filter is proposed and further developed to identify the moving heat source in a three-dimensional heat transfer system. Firstly, a step-renewed state space model considering the source position is established according to principle of source contribution. Using this model, a technique coupling fuzzy adaptive Kalman filter with weight recursive least squares algorithm is implemented to realize the simultaneous estimation of moving heat source and temperature field. Different spatiotemporal changes of heat source and measurement noises are assumed to validate the feasibility and test its performances of this technique. Results illustrates that this method can be used to inversely estimate moving heat source with different changes rates and directions. When the moving velocity varies as 0.25, 0.50, 1.00 mm/s and the time period is employed as 100, 200, 400, 800 s, the estimated heat source can accurately agree with exact one while the reconstructed temperature field is of low deviation. The mean relative errors of estimated heat source are no more than 3.25% and mean relative errors of temperature are smaller than 1.37% while standard deviation of measurement noises increases from 0.01 to 5.00, which demonstrates that this method is of high robustness and can be used under a deteriorated condition.

Application of ultrasound thermometry technique in case of local HIFU heating of test-object

The present work is aimed at development of a method for estimation of the accuracy of ultrasound thermometry (UST) when applying during local HIFU heating of a tissue-mimicking material (TMM). The method is based on comparison of the ultrasound measurement results with a temperature field reconstructed inside the TMM using data of the infrared (IR) camera surface measurements. In the case presented, the HIFU transducer heated up the TMM by 30 °C for 10 s in the focus area. Ultrasound signals were processed using an in-house UST application software. A 3D temperature field inside the TMM was reconstructed using a method based on the neural network approach. As a result, it has been achieved a good agreement between the UST measurement data and the reconstructed temperature field, especially for the points along the HIFU transducer axis.

3D Temperature Distribution Reconstruction in Furnace Based on Acoustic Tomography

3D temperature distribution measurement in a furnace based on acoustic tomography (AT) calculates temperature field through multipath acoustic time-of-flight (TOF) data. In this paper, a new 3D temperature field reconstruction model based on radial basis function approximation with polynomial reproduction (RBF-PR) is proposed for solving the AT inverse problem. In addition, the modified reconstruction method that integrates the advantages of the TSVD and Tikhonov regularization methods is presented to reduce the sensitivity of noise on perturbations with the ill-posed problems and improve the reconstruction quality (RQ). Numerical simulations are implemented to evaluate the effectiveness of the proposed reconstruction method using different 3D temperature distribution models, which include the one-peak symmetry distribution, one-peak asymmetry distribution, and two-peak symmetry distribution. To study the antinoise ability of our method, noises are added to the value of TOF. 3D display of reconstructed temperature fields and reconstruction errors is given. The results indicate that our model can reconstruct the temperature distribution with higher accuracy and better antinoise ability compared with the truncated generalized singular value decomposition (TGSVD). Besides that, the proposed method can determine the hot spot position with higher precision, and the temperature error of the hot spot is lower than the other compared methods.

Inverse estimation of variable thermal parameters in a functionally graded annular fin using dragon fly optimization

ABSTRACTThis paper presents an inverse study of heat transfer of a conductive, convective and radiative annular fin made of a functionally graded material. Three major parameters such as conductive–convective parameter, conductive–radiative parameter and the parameter describing the variation of thermal conductivity are inversely estimated from a specified temperature field. The forward solution of temperature field is obtained from the closed form solution of nonlinear heat transfer equation using Homotopy perturbation method (HPM). A dragonfly algorithm that simulates the swarming behaviour of dragonflies, as analogous, is employed in finding out the inverse parameters. The temperature values of the forward solution are used as input data for the inverse analysis. The inverse parameters are then estimated iteratively by minimizing the objective function until the guessed temperature field approximately satisfies the preassigned temperature field of the forward solution. The inverse simulation following HPM-based forward solution converges faster than ordinary differential equation-based forward solution. The reconstructed temperature fields obtained from the various combination of inverse parameters give good agreement (∼1% error) with the desired temperature field. Thus, the presented inverse model provides an opportunity to the fin designer for selecting the several feasible combinations of thermal parameters suggesting the material design that result in a prescribed temperature field.

Experimental investigation on gas-phase temperature of axisymmetric ethylene flames by large lateral shearing interferometry

The gas temperature fields of axisymmetric co-annular laminar diffusion ethylene flame jets in air and oxygen-enriched atmospheres were measured and visualized using large lateral shearing interferometry technique. Seven cases of reconstructed temperature fields were investigated using various compositions of fuel/oxidant with an average correction factor. The phase difference field were obtained using a fringe trace algorithm. A discrete Abel inversion process was adopted to resolve the refractive index distribution from the line-of-sight integrated data. The peak temperatures of the flame varied between 1980 K and 2050 K using air as the oxidant and increased to more than 2150 K when oxygen was added. Two separate high temperature zones, one located at the side edge of the flame, the other in the upper part of the flame around the centerline of the burner were observed in four of the seven instances of high mixture stoichiometry. The proposed methodology was verified to be suitable for the reconstruction of temperature distributions from the experimental measurement results.

Analysis of the sensor placement for optimal temperature distribution reconstruction

The temperature distribution as a function of time and space is reconstructed over a non-homogeneous media having an arbitrary three-dimensional geometry. This is done by applying an inverse problem to the collected data from optimally placed sensors on the boundary surface of the object under study. Sensor positioning and the choice of the number of sensors are optimized in terms of the resolution of the reconstructed temperature field and the error propagation of the method in case of uncertain measurements. The method can be performed in real time since the major computation burden is performed off-line.

Two-Dimension Temperature Field Reconstruction in Furnace by Acoustic Method

Acoustic temperature measurement technology is a new temperature measuring technology which is rising in recent years. This paper discusses a kind of reconstruction method of temperature field based on acoustic pyrometer. First , acoustic sensors has been used to obtain measurement data, and the technique of wavelet has been used to denoise in order to improve the accuracy of measurement , secondly, the least-squares algorithm has been used to reconstruct temperature field. Finally, we work out our own acoustic temperature measurement system and has got the satisfying result using our own acoustic pyrometer to detect two-dimension temperature field in the laboratory.

Temperature Field Reconstruction System Based on Ultrasonic Time-of-Flight Technique

A temperature field related with ultrasonic propagation in the air according to the different velocity in different temperature can be reconstructed with the TOF (time of flight) measurement at different temperatures. One method of two-dimensional temperature field reconstruction has been proposed in this paper based on ultrasonic time-of-flight technique. The temperature of the total temperature field has been calculated with the method of 2-dimensional interpolation according to the temperature values measured with 8 ultrasonic sensors which has the functions of signal sending and receiving distributed around the measured field with given position. 4 thermocouples have been used to check the result of reconstruct temperature field in the experiment. The disturbance of temperature sensors distribution with the traditional ways has been avoided with little influence between the each sub-field divided by 8 temperature sensors with the given reconstruction in this paper.

An Optimization Model for the Identification of Temperature in Intelligent Building

Methods for the reconstruction of temperature fields in an intelligent building with temperature data of discrete observation positions is a current topic of research. To reconstruct temperature field with observation data, it is necessary to model the identification of temperature in each observation position. In this paper, models for temperature identification in an intelligent building are formalized as optimization problems based on observation temperature data sequence. To solve the optimization problem, a feed forward neural network is used to formalize the identification structure, and connection matrixes of the neural network are the identification parameters. With the object function for the given optimization problem as the fitness function, the training of the feed forward neural network is driven by a genetic algorithm. The experiment for the precision and stability of the proposed method is designed with real temperature data from an intelligent building.

A 150-year reconstructed summer Asian–Pacific Oscillation index and its association with precipitation over eastern China

Reconstructing the long-term series of the East Asian summer monsoon (EASM) indices may help understand long-term variability of EASM and its associations with precipitation. In this study, the summer middle–upper tropospheric temperature over the Asian–North Pacific sector is reconstructed from sea level pressure during the past 150 years, and then an atmospheric thermal contrast between Asia and the North Pacific, called the Asian–Pacific Oscillation (APO) index, is calculated from the reconstructed temperature. The results show that the APO phenomenon may occur in the reconstructed temperature fields, and its index has a significant positive/negative correlation with SST over the extratropical North Pacific/the tropical central–eastern Pacific in the past 150 years. The reconstructed summer APO index shows inter-decadal variability, with a positive phase in the 1870–1890s, the 1920s, and the 1940–1970s, indicating a stronger thermal contrast between Asia and the North Pacific, and with a negative phase in the 1860s, the 1900–1910s, and the 1980–1990s, indicating a weaker thermal contrast. Corresponding to a higher APO index in earlier decades of the twentieth century, there are more rainfall to the south of the Yangtze River and over North China and less rainfall over the Huaihe River valley. In the recent decades, however, more- and less-rain belts shifted southwards when the APO index is higher. During 1850–1900, the reconstructed APO index also showed a significant positive correlation with precipitation in some regions of North China.

Experimental study of Rayleigh–Benard convection at intermediate Rayleigh numbers using interferometric tomography

An experimental study of Rayleigh–Benard convection in an intermediate aspect ratio box that is square in plan is reported. An intermediate range of Rayleigh numbers has been considered in the study. The fluid employed is air. A Mach–Zehnder interferometer is used to collect the line-of-sight projections of the temperature field in the form of interferometric fringes. Images have been recorded after a sufficient time has elapsed for the initial transients to have been eliminated. Interferograms have been collected from four to six view angles. These are used to obtain the three dimensional temperature field inside the cavity by using tomography. An algebraic reconstruction technique has been used for the inversion of the projection data. The convergence of the iterative inversion procedure was unambiguous and asymptotic. The reconstructed temperature field with a subset of the total data was found to be consistent with the remaining unused projections. Results for two Rayleigh numbers, namely 13 900 and 40 200 have been reported. These were found to correspond to two distinct flow regimes. At these Rayleigh numbers, a well-defined steady state was not observed. At the lower Rayleigh number, the fringes away from the wall showed mild unsteadiness. At the higher Rayleigh number, the fringes were found to switch between two patterns. Results for the dominant mode alone have been presented for this problem. At a Rayleigh number of 13 900, three dimensional flow structures, whose influence is equivalent to longitudinal rolls have been observed. At a Rayleigh number of 40 200, cubic cells have been noted in the cavity. The associated flow pattern is inferred to be a plume rising from the heated plate. The local Nusselt number variation is seen to be consistent with the observed flow patterns.

INTERFEROMETRIC STUDY OF RAYLEIGH-BENARD CONVECTION USING TOMOGRAPHY WITH LIMITED PROJECTION DATA

Reconstruction of a three-dimensional temperature field using interferometry is presented. The reconstruction procedure involves projection data that are recorded in the form of interferograms. The physical problem addressed is Rayleigh-Benard convection in a horizontal layer of air at a Rayleigh number of 3.48 104. Experimental results of the reconstructed temperature field in the range of Rayleigh numbers 104-105 are not available in the literature. Interferometric projections of the temperature field in the fluid layer are recorded using a Mach-Zehnder interferometer. Four different view angles are considered. The three-dimensional temperature field is reconstructed from two orthogonal projections and three different reconstruction algorithms. The correctness of the reconstructed temperature field is tested by a cross-check against the projections from the remaining two view angles. Results show the formation of a three-dimensional cubic roll pattern for the thermal field in the fluid layer. This has been interpreted as flow associated with a buoyant plume rising from the hot surface. The fluid is seen to be cooled at the top boundary and descends all around the central plume.

Real three-dimensional reconstruction of temperature field based on wavefront retrieval

The visualization of a quasi-stable flow field with full 3-D meaning must be provided with 2-D projections. In flow field interferometric tomography, the conventional method of fringe tracking, by which a few solitary 1-D projections are obtained, can evaluate only the 2-D distribution of the field on a limited number of cross sections. A new method that combines Fourier analysis and modified multigrid iteration is proposed to extract 2-D projections from interferograms of the measured field in various directions. On the basis of 2-D projections, the real 3-D field reconstruction can be realized. An experiment with an asymmetric temperature field measurement using a rotary Fabry-Pe´ rot (F-P) interferometer is reported and some cross sections of the reconstructed temperature field are given to prove that the methods of sampling, processing and reconstruction of the algorithm illustrated are effective.

Performance evaluation of fringe thinning algorithms for interferometric tomography

The present study is concerned with the sensitivity of reconstruction algorithms to fringe thinning operations, in the context of interferometric tomography. Interferograms obtained from a Mach–Zehnder interferometer are considered as the fringe system. The physical problem considered is fluid convection in a rectangular enclosure that is square in plan, heated from below and cooled from the top. The fringes are line-of-sight integrals of the refractive index and hence the temperature field. The fringe patterns are digitized and stored as strings of numbers using a CCD camera along with an image processing system. Three methods of fringe thinning algorithms are considered. The first algorithm is programmable and is based on the search of minimum intensity within the dark bands of the fringe system. The other two algorithms are, respectively, semi-automatic and manual search procedures for location of the midpoints of the dark bands. The thinned fringes contain information about the projection of the temperature field in the direction of the light beam. These data have been used to reconstruct the three-dimensional temperature field in the fluid layer using principles of tomography. The fringe thinning algorithms have been evaluated in terms of effort required, and differences in the reconstructed temperature field as well as the wall heat transfer rate. The automatic search procedure developed in the present work is found to be best suited in terms of these criteria.