To design more effective heat exchange ducts for thermoelectric conversion systems on aircraft, the heat transfer process of a working fluid in a nonuniformly heated square duct was simulated in this study and the influence of the heated wall position was further investigated. Due to the effects of the two main vortex structures in the duct, the highest wall temperature was found in the upper-wall heating case. With increasing working pressure, the influence of the heated wall position on the heat transfer process also increased. When the working pressure was 30 MPa, the wall temperature trend exhibited significant differences in cases with different heated walls, and the maximum wall temperature difference along the duct could be up to 110 K. With an increasing inlet temperature, the influence of the heated wall position on the heat transfer process decreased. Meanwhile, for cases under different pressures (specifically from 8 to 30 MPa), if the inlet temperature was higher than the value at which [Formula: see text] was [Formula: see text], the influence of the heated wall position on the yield strength of the duct also decreased with an increasing inlet temperature.
{"title":"Study on Heat Transfer of Carbon Dioxide in Airborne Thermoelectric Conversion System","authors":"Xuan-En Yang, Zhongwei Wang, Yao-bin Niu, Heyang Miao","doi":"10.2514/1.t6778","DOIUrl":"https://doi.org/10.2514/1.t6778","url":null,"abstract":"To design more effective heat exchange ducts for thermoelectric conversion systems on aircraft, the heat transfer process of a working fluid in a nonuniformly heated square duct was simulated in this study and the influence of the heated wall position was further investigated. Due to the effects of the two main vortex structures in the duct, the highest wall temperature was found in the upper-wall heating case. With increasing working pressure, the influence of the heated wall position on the heat transfer process also increased. When the working pressure was 30 MPa, the wall temperature trend exhibited significant differences in cases with different heated walls, and the maximum wall temperature difference along the duct could be up to 110 K. With an increasing inlet temperature, the influence of the heated wall position on the heat transfer process decreased. Meanwhile, for cases under different pressures (specifically from 8 to 30 MPa), if the inlet temperature was higher than the value at which [Formula: see text] was [Formula: see text], the influence of the heated wall position on the yield strength of the duct also decreased with an increasing inlet temperature.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48291678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. McGuire, C. Jacobs, Pierre B Mariotto, C. Grimaldi, A. Tibère-Inglesse, C. Laux
Measurements of high-temperature air emission spectra between 150 and 250 nm (VUV/UV) are presented. These measurements are calibrated in absolute intensity. The high-temperature air was produced using an atmospheric pressure plasma torch facility. The centerline temperature of the plasma jet is approximately 6700 K. A VUV emission spectroscopy system was adapted to the plasma torch facility to acquire spectra from 150 to 250 nm. Absolute intensity spectra were obtained in this wavelength range. They were compared with numerical predictions of the line-by-line spectroscopy code SPECAIR. The overall agreement between the SPECAIR predictions and measurements is good, particularly above 180 nm. Several modifications to the SPECAIR radiation code were carried out in order to improve agreement with experiments. These modifications significantly improved agreement though, at lower wavelengths, the data indicate that a source of emission remains unaccounted for by SPECAIR. Several possibilities for this missing source of emission are discussed, including photodissociation of the nitric oxide molecule.
{"title":"Measurements and Modeling of Air Plasma Radiation in the VUV","authors":"S. McGuire, C. Jacobs, Pierre B Mariotto, C. Grimaldi, A. Tibère-Inglesse, C. Laux","doi":"10.2514/1.t6768","DOIUrl":"https://doi.org/10.2514/1.t6768","url":null,"abstract":"Measurements of high-temperature air emission spectra between 150 and 250 nm (VUV/UV) are presented. These measurements are calibrated in absolute intensity. The high-temperature air was produced using an atmospheric pressure plasma torch facility. The centerline temperature of the plasma jet is approximately 6700 K. A VUV emission spectroscopy system was adapted to the plasma torch facility to acquire spectra from 150 to 250 nm. Absolute intensity spectra were obtained in this wavelength range. They were compared with numerical predictions of the line-by-line spectroscopy code SPECAIR. The overall agreement between the SPECAIR predictions and measurements is good, particularly above 180 nm. Several modifications to the SPECAIR radiation code were carried out in order to improve agreement with experiments. These modifications significantly improved agreement though, at lower wavelengths, the data indicate that a source of emission remains unaccounted for by SPECAIR. Several possibilities for this missing source of emission are discussed, including photodissociation of the nitric oxide molecule.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46786739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two-temperature models for coupled vibrational relaxation and dissociation in shock-heated oxygen are assessed using low-uncertainty measured data from reflected shock tube experiments. A computationally efficient multistep technique is developed to model the unsteady dynamics of shock reflection in a relaxing and dissociating gas. The developed technique is then benchmarked through comparison with unsteady computational fluid dynamic simulations. Results from the benchmarking effort demonstrate that the adopted multistep modeling procedure accurately captures the dominant gas dynamic effects influencing the state of the test gas at the measurement location. A parametric study is then performed to assess several combinations of possible two-temperature modeling approaches for nonequilibrium oxygen dissociation. The current assessment demonstrates that the widely adopted Park model is inconsistent with the measured data, while the recently developed modified Marrone and Treanor (MMT) model demonstrates promising agreement with the data. The results of the present study clearly indicate that the MMT model is more appropriate for two-temperature modeling of nonequilibrium oxygen dissociation than the legacy Park model. Patterns in the parametric comparison also suggest that the approximate treatment of non-Boltzmann vibrational state distributions within the MMT model may require improvement.
{"title":"Two-Temperature Modeling of Nonequilibrium Relaxation and Dissociation in Shock-Heated Oxygen","authors":"Timothy T. Aiken, I. Boyd","doi":"10.2514/1.t6753","DOIUrl":"https://doi.org/10.2514/1.t6753","url":null,"abstract":"Two-temperature models for coupled vibrational relaxation and dissociation in shock-heated oxygen are assessed using low-uncertainty measured data from reflected shock tube experiments. A computationally efficient multistep technique is developed to model the unsteady dynamics of shock reflection in a relaxing and dissociating gas. The developed technique is then benchmarked through comparison with unsteady computational fluid dynamic simulations. Results from the benchmarking effort demonstrate that the adopted multistep modeling procedure accurately captures the dominant gas dynamic effects influencing the state of the test gas at the measurement location. A parametric study is then performed to assess several combinations of possible two-temperature modeling approaches for nonequilibrium oxygen dissociation. The current assessment demonstrates that the widely adopted Park model is inconsistent with the measured data, while the recently developed modified Marrone and Treanor (MMT) model demonstrates promising agreement with the data. The results of the present study clearly indicate that the MMT model is more appropriate for two-temperature modeling of nonequilibrium oxygen dissociation than the legacy Park model. Patterns in the parametric comparison also suggest that the approximate treatment of non-Boltzmann vibrational state distributions within the MMT model may require improvement.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44890287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The arrangement of electrodes in an electrohydrodynamic (EHD) gas pump inside a square channel is experimentally examined for its effective use in thermal management. Particularly, the study looks into modifying the characteristics of flow produced by an EHD gas pump through the arrangement of its electrodes. The aim is to produce swirl flow, which can effectively increase the flow mixing inside the channel and leads to the desired outcome. To this end, a two-stage gas pump powered by direct-current voltages ranging from 24 to 26 kV with electrodes flush mounted on two neighboring walls is devised. In addition to the volume flow rate produced, the performance of the pump is evaluated using an energy efficiency factor, which is defined as the volume flow rate delivered by a unit power input. It is found that the EHD gas pump with offset electrodes can not only produce more volume flow rate but also has a larger value for energy efficiency, which may be more favorable for the application in thermal management. The present results reveal that the EHD gas pump has great potential for applications in thermal management and can be more energy efficient when operated with uneven applied voltages.
{"title":"Electrohydrodynamic Swirl-Flow Generators for Application in Thermal Management","authors":"S. C. Lin, Bert Huang, S. Liou, F. Lai","doi":"10.2514/1.t6741","DOIUrl":"https://doi.org/10.2514/1.t6741","url":null,"abstract":"The arrangement of electrodes in an electrohydrodynamic (EHD) gas pump inside a square channel is experimentally examined for its effective use in thermal management. Particularly, the study looks into modifying the characteristics of flow produced by an EHD gas pump through the arrangement of its electrodes. The aim is to produce swirl flow, which can effectively increase the flow mixing inside the channel and leads to the desired outcome. To this end, a two-stage gas pump powered by direct-current voltages ranging from 24 to 26 kV with electrodes flush mounted on two neighboring walls is devised. In addition to the volume flow rate produced, the performance of the pump is evaluated using an energy efficiency factor, which is defined as the volume flow rate delivered by a unit power input. It is found that the EHD gas pump with offset electrodes can not only produce more volume flow rate but also has a larger value for energy efficiency, which may be more favorable for the application in thermal management. The present results reveal that the EHD gas pump has great potential for applications in thermal management and can be more energy efficient when operated with uneven applied voltages.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46266952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aerothermal analysis of spacecraft planetary entry is heavily dependent on heritage engineering models. The film coefficient heat transfer model examined in this paper estimates the convective heating to the vehicle for a laminar, dissociated, chemically reacting boundary layer for an Earth atmosphere. This model requires information about the vehicle and flowfield for a given trajectory point and estimates a proportional relationship between enthalpy potential and convective heat flux. In practice it is the aerothermal engineer who must decide which assumptions are appropriate for his/her application. This work looks at numerous CFD simulations for an arbitrary, axisymmetric flight vehicle to analyze the relative importance of both the mass and energy constraints imposed at the wall boundary, as well as the effect of various diffusion models. Within the subset of tested energy boundary conditions, it is found that the most desirable energy boundary condition is the radiative equilibrium boundary condition, which permits conservative estimates of convective heat flux, but also generates flowfield-dependent spatial thermal distributions along the surface. Other key findings are presented in an effort to make the film coefficient engineering model readily available to design engineers across industry.
{"title":"Numerical Investigation of Film Coefficient Approximation for Chemically Reacting Boundary-Layer Flows","authors":"J. Cooper, Giovanni Salazar, Alexandre Martin","doi":"10.2514/1.t6707","DOIUrl":"https://doi.org/10.2514/1.t6707","url":null,"abstract":"Aerothermal analysis of spacecraft planetary entry is heavily dependent on heritage engineering models. The film coefficient heat transfer model examined in this paper estimates the convective heating to the vehicle for a laminar, dissociated, chemically reacting boundary layer for an Earth atmosphere. This model requires information about the vehicle and flowfield for a given trajectory point and estimates a proportional relationship between enthalpy potential and convective heat flux. In practice it is the aerothermal engineer who must decide which assumptions are appropriate for his/her application. This work looks at numerous CFD simulations for an arbitrary, axisymmetric flight vehicle to analyze the relative importance of both the mass and energy constraints imposed at the wall boundary, as well as the effect of various diffusion models. Within the subset of tested energy boundary conditions, it is found that the most desirable energy boundary condition is the radiative equilibrium boundary condition, which permits conservative estimates of convective heat flux, but also generates flowfield-dependent spatial thermal distributions along the surface. Other key findings are presented in an effort to make the film coefficient engineering model readily available to design engineers across industry.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43766276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Numerical simulations have been performed to examine the flows inside a square channel produced by a two-stage electrohydrodynamic (EHD) gas pump with two electrode arrangements. The EHD pump has a pair of seven emitting electrodes flush mounted on two parallel walls at each stage. The flush-mounted electrodes produce corona wind similar to a wall jet that is mainly responsible for flow delivery. The pump is operated by a combination of three different voltages (24, 26, and 28 kV) for performance improvement. Because flow visualization is very challenging to implement in experimental study of EHD flows, very few results are available in the literature. As such, this study is specifically aimed at providing additional insight to the flowfield inside the channel through visualization of the numerical results obtained. Also, the overall effectiveness of the EHD gas pump is evaluated by the volume flow rate delivered as well as its power efficiency. It has been found that the power efficiency for the EHD pumps considered is higher than the conventional fans/pumps. Thus, they have a great potential for applications in thermal management. Particularly, they can be more energy efficient when they are operated by uneven applied voltages.
{"title":"Flows Generated by Electrohydrodynamic Gas Pumps with Different Electrode Orientations","authors":"A. Mazumder, F. Lai","doi":"10.2514/1.t6711","DOIUrl":"https://doi.org/10.2514/1.t6711","url":null,"abstract":"Numerical simulations have been performed to examine the flows inside a square channel produced by a two-stage electrohydrodynamic (EHD) gas pump with two electrode arrangements. The EHD pump has a pair of seven emitting electrodes flush mounted on two parallel walls at each stage. The flush-mounted electrodes produce corona wind similar to a wall jet that is mainly responsible for flow delivery. The pump is operated by a combination of three different voltages (24, 26, and 28 kV) for performance improvement. Because flow visualization is very challenging to implement in experimental study of EHD flows, very few results are available in the literature. As such, this study is specifically aimed at providing additional insight to the flowfield inside the channel through visualization of the numerical results obtained. Also, the overall effectiveness of the EHD gas pump is evaluated by the volume flow rate delivered as well as its power efficiency. It has been found that the power efficiency for the EHD pumps considered is higher than the conventional fans/pumps. Thus, they have a great potential for applications in thermal management. Particularly, they can be more energy efficient when they are operated by uneven applied voltages.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47740299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hydrogen is the most promising fuel for reducing carbon emissions, but hydrogen combustion produces higher temperature compared to hydrocarbon fuel. In this paper, a three-dimensional compressible combustion–flow–heat transfer model of combustor was established, and a dry-low-emission combustor was examined by using the realizable [Formula: see text] model, transported probability density function, and discrete ordinates model combining weighted sum of gray gas model, analyzing the effects of hydrogen/methane blended fuel and thermal boundaries on the combustor thermal environment. The results show that when the fuel hydrogen volume percentage increases from 0 to 75%, the maximum gas temperature and [Formula: see text] concentration on the central axis of the combustor increase by about 160.8 and 662.9%, respectively; the maximum incident radiant heat flux of the combustor wall increases by about 150%; and the local maximum ratio of the radiant heat transfer to the total heat transfer through the wall increases from about 34 to about 49%. The effect of the boundary conditions varies depending on the hydrogen percentage. At the hydrogen percentage of 75%, the maximum wall-incident radiant heat flux under the adiabatic condition is nearly 180.3 and 77.4% higher than the values at 1370 and 1920 K isothermal boundaries, respectively.
{"title":"Effects of Hydrogen/Methane on the Thermal Environment of Heavy-Duty Gas Turbine Combustor","authors":"Xiao-Xian Zhang, Qing Ai, Wenzhuo Wang","doi":"10.2514/1.t6798","DOIUrl":"https://doi.org/10.2514/1.t6798","url":null,"abstract":"Hydrogen is the most promising fuel for reducing carbon emissions, but hydrogen combustion produces higher temperature compared to hydrocarbon fuel. In this paper, a three-dimensional compressible combustion–flow–heat transfer model of combustor was established, and a dry-low-emission combustor was examined by using the realizable [Formula: see text] model, transported probability density function, and discrete ordinates model combining weighted sum of gray gas model, analyzing the effects of hydrogen/methane blended fuel and thermal boundaries on the combustor thermal environment. The results show that when the fuel hydrogen volume percentage increases from 0 to 75%, the maximum gas temperature and [Formula: see text] concentration on the central axis of the combustor increase by about 160.8 and 662.9%, respectively; the maximum incident radiant heat flux of the combustor wall increases by about 150%; and the local maximum ratio of the radiant heat transfer to the total heat transfer through the wall increases from about 34 to about 49%. The effect of the boundary conditions varies depending on the hydrogen percentage. At the hydrogen percentage of 75%, the maximum wall-incident radiant heat flux under the adiabatic condition is nearly 180.3 and 77.4% higher than the values at 1370 and 1920 K isothermal boundaries, respectively.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45501704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Peisheng Li, Guozi Zhu, Y. Zhang, Yan Gao, Jian Hong, Zhaoqing Ke
In this paper, we propose a new microchannel heat sink with ribs and jets, which can not only increase the heat transfer performance but also improve the fluid flow in the microchannel. The effects of different shapes of ribs and inlet aspect ratios on the performance evaluation criteria at various Reynolds numbers are discussed. At an inlet Reynolds number of 3000, the maximum temperature of the modified microchannel heat sink is 8.78% lower than that of the smooth microchannel, and the performance evaluation criteria is increased by 0.94. Under the same conditions, the bottom plate temperature difference of the hydrofoil rib microchannel jets is 3.4% lower than that of the cylindrical rib microchannel jets; and the triangular-shaped ribs increase the heat transfer and cause greater pressure loss penalty due to the formation of a larger swirl zone in the back area. The jet inlet parameters can effectively improve the heat transfer coefficient of the microchannel. In terms of the heat transfer capability and the uniformity of the bottom plate temperature, the hydrofoil rib microchannel with jets has the best heat dissipation effect when the jet inlet parameter is [Formula: see text].
{"title":"Heat Transfer Enhancement of Microchannel with Jets and Ribs","authors":"Peisheng Li, Guozi Zhu, Y. Zhang, Yan Gao, Jian Hong, Zhaoqing Ke","doi":"10.2514/1.t6788","DOIUrl":"https://doi.org/10.2514/1.t6788","url":null,"abstract":"In this paper, we propose a new microchannel heat sink with ribs and jets, which can not only increase the heat transfer performance but also improve the fluid flow in the microchannel. The effects of different shapes of ribs and inlet aspect ratios on the performance evaluation criteria at various Reynolds numbers are discussed. At an inlet Reynolds number of 3000, the maximum temperature of the modified microchannel heat sink is 8.78% lower than that of the smooth microchannel, and the performance evaluation criteria is increased by 0.94. Under the same conditions, the bottom plate temperature difference of the hydrofoil rib microchannel jets is 3.4% lower than that of the cylindrical rib microchannel jets; and the triangular-shaped ribs increase the heat transfer and cause greater pressure loss penalty due to the formation of a larger swirl zone in the back area. The jet inlet parameters can effectively improve the heat transfer coefficient of the microchannel. In terms of the heat transfer capability and the uniformity of the bottom plate temperature, the hydrofoil rib microchannel with jets has the best heat dissipation effect when the jet inlet parameter is [Formula: see text].","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49055592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Haoxi Xiong, Xiwang Xu, S. Yi, Liangtao Nie, Yu Li
The flowfield structure, heat flux distribution, and pressure fluctuations of the wall-mounted cylinder-induced hypersonic boundary-layer transition are investigated at a 10 deg angle of attack. Experiments are conducted in a Mach 6 low-noise wind tunnel using the nanotracer-based planar laser scattering (NPLS) technique, temperature-sensitive paints (TSP), and high-frequency pressure sensors. First, the streamwise and spanwise NPLS images, TSP results, and power spectral density results of isolated cylinders at different heights show that with the increase of the cylinder height [Formula: see text], the size of the separated region and the spanwise width of the horseshoe vortex increase, and the transition moves forward. Second, the flowfield structure and wall heat flux distribution around the streamwise cylinder arrays are investigated. The results demonstrate that the downstream cylinder will destroy the development of the hairpin vortex in the upstream cylinder wake but will expand the horseshoe vortex to both sides, increasing the influence area of the cylinder.
{"title":"Experimental Investigation of the Hypersonic Boundary-Layer Transition Induced by the Wall-Mounted Cylinder","authors":"Haoxi Xiong, Xiwang Xu, S. Yi, Liangtao Nie, Yu Li","doi":"10.2514/1.t6682","DOIUrl":"https://doi.org/10.2514/1.t6682","url":null,"abstract":"The flowfield structure, heat flux distribution, and pressure fluctuations of the wall-mounted cylinder-induced hypersonic boundary-layer transition are investigated at a 10 deg angle of attack. Experiments are conducted in a Mach 6 low-noise wind tunnel using the nanotracer-based planar laser scattering (NPLS) technique, temperature-sensitive paints (TSP), and high-frequency pressure sensors. First, the streamwise and spanwise NPLS images, TSP results, and power spectral density results of isolated cylinders at different heights show that with the increase of the cylinder height [Formula: see text], the size of the separated region and the spanwise width of the horseshoe vortex increase, and the transition moves forward. Second, the flowfield structure and wall heat flux distribution around the streamwise cylinder arrays are investigated. The results demonstrate that the downstream cylinder will destroy the development of the hairpin vortex in the upstream cylinder wake but will expand the horseshoe vortex to both sides, increasing the influence area of the cylinder.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49174811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The transient temperature response of a bimaterial with a circular insulated interface region is studied under sudden heating or cooling. The time-fractional dual-phase-lag heat conduction model is adopted to simulate the non-Fourier effect. The problem is reduced to an initial-boundary value problem. The Laplace transform is applied to convert the problem to a mixed boundary value problem, and then the Hankel transform reduces it to a Fredholm integral equation. Special situations for asymptotic thermal behavior near the insulated circular edge and for the steady-state cases are discussed, respectively. The dynamic intensity factors of heat flux and temperature gradient near the insulated circular edge are computed numerically through Stehfest’s Laplace inversion transform technique. The influences of fractional order and relaxation times on the instantaneous temperature change are analyzed. The exact solution of temperature fields for the steady-state case is derived and displayed graphically. The wave-like diffusion behavior of the fractional dual-phase-lag model is interpreted.
{"title":"Fractional Dual-Phase-Lag Non-Fourier Heat Transfer in a Bimaterial with a Circular Interface Insulator","authors":"Xue-yang Zhang, Yingsi Hu, Xian‐Fang Li","doi":"10.2514/1.t6772","DOIUrl":"https://doi.org/10.2514/1.t6772","url":null,"abstract":"The transient temperature response of a bimaterial with a circular insulated interface region is studied under sudden heating or cooling. The time-fractional dual-phase-lag heat conduction model is adopted to simulate the non-Fourier effect. The problem is reduced to an initial-boundary value problem. The Laplace transform is applied to convert the problem to a mixed boundary value problem, and then the Hankel transform reduces it to a Fredholm integral equation. Special situations for asymptotic thermal behavior near the insulated circular edge and for the steady-state cases are discussed, respectively. The dynamic intensity factors of heat flux and temperature gradient near the insulated circular edge are computed numerically through Stehfest’s Laplace inversion transform technique. The influences of fractional order and relaxation times on the instantaneous temperature change are analyzed. The exact solution of temperature fields for the steady-state case is derived and displayed graphically. The wave-like diffusion behavior of the fractional dual-phase-lag model is interpreted.","PeriodicalId":17482,"journal":{"name":"Journal of Thermophysics and Heat Transfer","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43815356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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