Performance evaluation of fringe thinning algorithms for interferometric tomography

A deep learning method based on partition modeling for reconstructing temperature field

The present work analyzed the flow and heat transfer of the nanoliquid film flow over a moving inclined substrate. The motion of nanoparticles is induced by the action of both the gravitational force as well as the substrate movement. The hydrodynamic and thermal layers developing along the channel with a constant film thickness are resolved analytically. The corresponding pressure distribution, velocity field, temperature field and the physical quantities of wall shear stress as well as wall heat transfer rate are formulated in closed-form expressions. Seven different types of nanofluids are accounted for. Thermophysical properties of these particles enable us to visualize the flow and thermal development of the nanoliquid films in terms of the clean base fluid by the help of the defined shape factors. The considered mathematical model is validated against the available data in cases of special flow configurations. The carbon nanotubes are shown to have the highest heat transfer rates as compared to the other nanoparticles. On the other hand, the film thickness is much reduced and the wall shear is much amplified in the presence of silver nanoparticles.

A study is made of buoyant convection in a rectangular enclosure, with protruding heaters attached on one vertical wall. The total amount of heat generated in the entire heaters is fixed. Numerical solutions to the Navier-Stokes equations are secured for the Rayleigh number ranging 104–108. In order to deal with more practical situations, a fluid of temperature-dependent viscosity is considered. Detailed descriptions are presented for the flow and temperature fields. Physical interpretations are provided for the heat transfer mechanism. At low Rayleigh number, heat transfer across the enclosure is invigorated as the number of heaters increases. At high Rayleigh number, there exist an optimum number of heaters that yields maximal system-wide heat removal in the enclosure.

The authors present a new algorithm for analyzing ray deflection within spherical refractive index fields. The algorithm emanates from the well-known deconvolution algorithm for axisymmetric refractive index fields using the inverse Abel transformation and can be used for experimental Rainbow Schlieren Deflectometry (RSD) data. It was numerically validated by Computational Fluid Dynamics (CFD) calculations of free convection around an isothermal sphere and successive ray tracing through the determined temperature field. The algorithm determined radial temperature profiles and local Nusselt numbers from resulting deflection angles of the ray tracing simulations. An excellent agreement between original and reconstructed temperature field within the limits of assumptions was reached. This proves the usability of the algorithm for the experimental determination of spherical refractive index fields from future heat or mass transfer experiments.

In this paper, we present a method of quantitatively measuring in real-time the dynamic temperature field change and visualization of volumetric temperature fields generated by a 2D axial-symmetric heated fluid from a pulsatile jet in a water tank through off-axis digital holographic interferometry. A Mach-Zehnder interferometer on portable platform was built for the experimental investigation. The pulsatile jet was submerged in a water tank and fed with water with higher temperature. Tomographic approach was used to reconstruct the temperature fields through the Abel Transform and the filtered back-projection. Averaged results, tomographic view, standard deviation and errors are presented. The presented results reveal digital holographic interferometry as a powerful technique to visualize temperature fields in flowing liquids and gases.

This investigation deals with the combined effects of Navier slip, suction/injection, convective cooling and temperature dependent viscosity on an unsteady third grade fluid flow in a porous channel filled with saturated porous medium. The heat exchange with the ambient at the channel surfaces is assumed to obey Newton’s law of cooling. The model equations governing the flow system are solved using a semi-implicit finite difference scheme. The effects of the thermophysical parameters on the temperature and velocity fields, the skin friction and the wall heat transfer rate are simulated and discussed in detail.

Instantaneous phase-stepping interferometry based on a pixelated micro-polarizer array

Introduction. The efficiency of the metalworking processes highly depends on the performance of the implemented cutting tools that can be increased by studying its stress-strain state and temperature fields. Existing stress analysis methods either have a low accuracy or are inapplicable for research during the operation of the tools made of materials with high mechanical properties. In addition, the study of temperature fields using known methods is difficult due to the small size of the cutting zone, high temperatures, and a heavy temperature gradient appearing during metal cutting. The purpose of this study is to develop new experimental methods for measuring the stress-strain and temperature fields in the cutting tool during its operation using laser interferometry. The methods include: obtaining interference fringe patterns using an interferometer with the original design, obtaining the tool deformation field during the cutting process by recording the changes in interference fringe patterns using a high-speed camera, processing fringe patterns with the separation of deformations caused by heating and cutting forces, and calculating temperature fields and stress distributions using mechanical properties and the coefficient of thermal expansion of the tool material. The advantages of the developed methods include: applicability under real operating conditions of the cutting tool, ability to study the non-stationary stress-strain state and temperatures during an operation, and achievement of a high spatial resolution and a small field of view for the investigated surface. Results and Discussion. The experimental study confirmed the efficiency of the methods. The results of the study included the fields of stresses and temperatures obtained during the orthogonal cutting of heat-resistant steel with a tool made of cemented tungsten carbide WC-8Co. The developed methods can be used to study the cutting tool efficiency at close to real conditions and in obtaining boundary conditions for the study stress-strain state of a workpiece material near the cutting zone.

Lattice BGK simulations of double diffusive natural convection in a rectangular enclosure in the presences of magnetic field and heat source

There are many deficiencies in contact temperature measurement, which can not provide a good guarantee for economy, efficiency and safety. Ultrasonic sensor temperature measurement technology has a good effect on the real-time monitoring of complex temperature field. This study takes the boiler furnace as the research object and the reconstruction of the temperature field in the furnace as the research purpose. Based on the finite element method, a single peak symmetrical temperature field model of the furnace is established on COMSOL platform to simulate the propagation of sound waves in the furnace, calculate the flight time according to the cross-correlation algorithm, and restore the temperature field of the furnace temperature field model by using the least square method and interpolation algorithm. The results show that the maximum relative error of flight time and theoretical flight time obtained by cross-correlation algorithm is 0.85%, and the average absolute error of reconstructed temperature field and single peak symmetric temperature field is 31K, which has a good reconstruction effect.

In this work, a measurement technique based on a single-beam coherent gradient sensing (CGS) interferometer is used to obtain line-of-sight projections of a 3-D temperature field in a convective fluid medium. Due to its inherent insensitivity to vibrations, simple and cost effective optical layout, and, most importantly, the absence of a separate reference beam, CGS is an attractive choice for measurements in convective fluids. In the present study, line-of-sight interferometric projections of a differentially heated water medium in a cylindrical cavity are presented for a cavity aspect ratio (diameter/height) of 3.9. The 3-D temperature field is then obtained using the line-of-sight interferometric projections with a 3-D tomographic reconstruction algorithm. The temperature field obtained shows the absence of a radial-symmetric pattern at a Rayleigh number of 1.6×105, which is in agreement with observations from the literature.

Buoyancy-driven convection in a differentially heated rectangular cavity containing layers of air—water, air—silicone oil, and silicone oil—water has been experimentally studied using laser-interferometry. The cavity has dimensions 32 × 32 mm2 in the vertical plane and length 447 mm. The layer thicknesses were taken to be equal. Experiments are conducted with three cavity temperature differences of 10, 15, and 18 K. The flow field is mapped in the direction parallel to the cavity length using a Mach-Zehnder interferometer. The flow regimes (such as steady two-dimensional, time-dependent, etc.) established in the individual fluid layers were compared with the published regime diagrams of single fluid layer at different Rayleigh numbers. Quantities such as the interface temperature, average Nusselt number, and the temperature profiles were determined from the interferograms. The interface shapes are recorded in the form of shadowgraphs. These results were also looked upon in terms of the coupling mechanism established at the interface. The major conclusions arrived in this study are as follows. In the experiments involving air, the layers were found to be thermally coupled. The unsteadiness in water could however be transmitted to air in the mechanical coupling mode. The presence of silicone oil over water led to mechanical coupling in the sense that the convective field in water was visibly retarded. The interface temperature determined from the experiments matched those from correlations for a single fluid whenever the coupling was thermal in origin. The differences were higher during mechanical coupling. The interface deformation correlated well with the roll movement visible in the fringes.

An experimental investigation of natural convection wakes above a line heat source

In This section we study of Mixed convective heat transfer of non-Newtonian fluids through porous medium with magnetic field on a flat plate has been investigated using a modified power - law viscosity model. This model does not contain physically unrealistic limits of zero or infinite viscosity as are encountered in the boundary - layer formulation with traditional models of viscosity for power - law fluids through porous medium with magnetic field. These unrealistic limits can introduce an irremovable singularity at the leading edge; the present modified model matches well with the measurement of viscosity, and does not introduce irremovable singularities. Therefore, the boundary layer equations can be solved by marching from the leading edge downstream as for Newtonian fluids. The numerical results are presented for a shear-thinning fluid in terms of the velocity and temperature distribution, and for important physical properties, namely the wall shear stress and heat transfer rates. valid at the leading edge of the boundary-layer. This similarity solution is the required upstream condition at the leading edge of the flat plate to integrate boundary-layer equations along the stream wise direction. Traditional power-law correlation, that in the limit of large or small shear rates, Traditional power-law correlations introduce non-removable singularities into boundary-layer formulations for infinite or zero viscosity. Without recognizing the cause of such unrealistic conditions, complex multi-layer structures have been introduced by many authors.

This paper proposes an analytical model for natural convection in a closed rectangular enclosure filled by a fluid, with imposed heat fluxes at the vertical walls and adiabatic horizontal walls. The analytical model offers a simplified, but easy to handle, description of the temperature and velocity fields. The predicted temperature, velocity, and pressure fields are shown to be in agreement with those obtained from a reliable numerical model. The Nusselt numbers for both the analytical and numerical solutions are then calculated and compared, varying both the aspect ratio of the enclosure and the Rayleigh number. Based on the comparisons, it is possible to assess the dependence of the reliability of the analytical model on the aspect ratio of the enclosure, showing that the prediction error rapidly decreases with the increase of the enclosure slenderness.