Experimental Thermal and Fluid Science最新文献

{"title":"Droplet breakup and evaporation in liquid-fueled detonations","authors":"","doi":"10.1016/j.expthermflusci.2024.111324","DOIUrl":"10.1016/j.expthermflusci.2024.111324","url":null,"abstract":"<div><div>In liquid-fueled detonations droplets are subjected to a myriad of complex codependent physical phenomena occurring on overlapping temporal and spatial scales, resulting in rapid vaporization. The rate at which droplets vaporize is enhanced by the concurrent hydrodynamic breakup processes. This article describes experiments where small (<span><math><mrow><mi>d</mi><mo>&lt;</mo><mn>125</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span>) droplet breakup at high Weber number <span><math><mrow><mi>O</mi><mrow><mo>(</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup><mtext>–</mtext><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span> is imaged in a self-sustained liquid-fueled detonation with laser optical Mie scattering imagery. Experimental initial conditions, including the droplet size and mass distribution, are characterized and reported. Child droplet clouds generated from droplet interactions with detonation waves are observed to persist for approximately 10 mm past the detonation front and grow to the order of millimeters in width. A velocity deficit of <span><math><mrow><mo>∼</mo><mn>10</mn><mtext>%</mtext></mrow></math></span> was observed for the multiphase detonations wave speed when compared to calculations for the equivalent gaseous detonations. The bulk droplet survival distances and breakup cloud morphology are compared to the predictions of relevant evaporation and breakup models. Calculations indicate that evaporation alone would result in droplet survival distances orders of magnitude longer than those observed. A droplet process whereby breakup occurs over an extended time, concurrent with evaporation, provides a phenomenological explanation. Empirical models constructed for shock-driven breakup predicted larger child droplet sizes than theoretical models based on linear stability theory, yielding survival distances and cloud shapes within the range of values seen in experiments. Droplets were however observed to persist longer than either model would predict. The discrepancy between calculations and experiment indicate that development of models tailored to droplets subject to variable acceleration are necessary to fully explain the multiphase detonation.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142357735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hypergolic fuel impacting a gelled oxidizer wall: Droplet dynamics, heat release, ignition, and flame analysis","authors":"","doi":"10.1016/j.expthermflusci.2024.111322","DOIUrl":"10.1016/j.expthermflusci.2024.111322","url":null,"abstract":"<div><div>The combination of high-concentration solutions of hydrogen peroxide, known as High Test Peroxide (HTP), with the green fuel composed of tetramethylethylenediamine, dimethylaminoethanol, and methanol (TMEDA/DMEA/MeOH, 1:1:1 vol%), catalyzed by 1 wt% of copper chloride dihydrate, has significant potential for space hypergolic propulsion applications in terms of performance and safe operation. Besides the well-known and mature propulsion systems adopting liquid and solid propellants, gel propellants also present interesting characteristics that can be better explored to enable the creation of alternative propulsive systems. The present work employed HTP at 98 wt% with 6 wt% of fumed silica as a gelling agent to create gelled HTP (GHTP). Droplets of the green fuel impinged on a layer of GHTP placed over a glass slide, acting as a solid oxidizer, mimicked an element of a new hybrid gel/liquid hypergolic propulsion system. Data from infrared and visible light cameras enabled a detailed analysis of the dynamics of a reactive droplet impinging on a gelled oxidizer wall, as well as the heat release, ignition, and flame spread of the hypergolic GHTP/green fuel pair under open-air conditions. The heat release was observed to be distributed across concentric annular areas for both the fuel surrogate and the fuel with catalyst, before and after ignition, demonstrating a strong correlation with non-reactive droplet fluid dynamics, which was corroborated by spread diameter analysis processed from visible image data. Vapor and Ignition Delay Times (VDT and IDT) were found to be as low as 4 and 17 ms, respectively, for the highest droplet impact velocity and catalyst concentration. The reaction rate in the gas phase, considering the flame spread area, showed a dependency of both impact velocity and catalyst concentration, with the latter exhibiting a more pronounced and clear effect. The surface temperature ranges where first vaporization and ignition occurred were 60 °C <span><math><mo>∼</mo></math></span> 70 °C and 120 <span><math><mo>∼</mo></math></span> 170 °C, respectively, which is close to the boiling point of methanol and the auto-ignition temperature of TMEDA. This finding, along with the chemical mechanisms in the gas phase related to the presence of a catalyst in the fuel, may be important for hypergolic ignition. The relatively low ignition temperatures and the short ignition times represent additional advantages of the present hypergolic combination for propulsion applications.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142319395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Visualization study on the dynamic behavior of shear thinning droplets impacting superhydrophobic spheres","authors":"","doi":"10.1016/j.expthermflusci.2024.111318","DOIUrl":"10.1016/j.expthermflusci.2024.111318","url":null,"abstract":"<div><div>The surface and droplet characteristics significantly affect the dynamic of droplet impact on solid surfaces. In present work, a platform is utilized to experimentally study the dynamic behavior of shear thinning fluid droplets impacting superhydrophobic spheres, where the effects of different concentrations, Weber numbers (<em>We</em>), particle size ratios on droplets impact are studied. The results showed that on the superhydrophobic sphere, as the shear thinning droplet concentration increases, the diffusion diameter increases, and the contact time decreases. For the same curvature, the contact time between the droplet and the sphere decreases with the increase of the <em>We</em>. When the <em>We</em> reaches 75 or above, the contact time remains constant with an increase in the <em>We</em>. For various curvature conditions, the contact time increases as the curvature increasing. When the diameter ratio of the sphere to the droplet is <span><math><mrow><msub><mi>D</mi><mrow><mo>∗</mo></mrow></msub><mo>≥</mo><mn>6</mn></mrow></math></span>, the maximum diffusion coefficient remains almost constant. However, when <span><math><mrow><msub><mi>D</mi><mrow><mo>∗</mo></mrow></msub><mo>&lt;</mo><mn>6</mn></mrow></math></span>, the maximum diffusion dimensionless diameter significantly increases as the particle size ratio decreases. More importantly, a theoretical model considering gravity effect is presented to predict the maximum dimensionless diameter of shear thinning droplets on superhydrophobic spheres according to energy conservation. The predicted results are rationally agreement with experiments with the deviation within ±10 %.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A study on the wake structure of an ascending submersible with silk flexible appendages using continuous wavelet transform and dynamic mode decomposition","authors":"","doi":"10.1016/j.expthermflusci.2024.111323","DOIUrl":"10.1016/j.expthermflusci.2024.111323","url":null,"abstract":"<div><div>This study proposed a new method for installing silk flexible appendages on the surface of the submersible to modify the wake structure of ascending submersibles, and explored a method of drag reduction of ascending submersible. A comparative analysis of the flow structure of submersibles with varying appendage lengths was conducted to understand the disturbance characteristics of the wake flow structure of submersible, and the high-speed particle image velocimetry (PIV) measurement experiment was conducted at a Reynolds number of 6456. Analysis of the time-averaged flow field showed that the flexible appendages could disrupt the two large-scale vortices in the wake of the submersibles during the sailing process, but this ability diminished with increasing appendage length. Furthermore, continuous wavelet transform (CWT) and dynamic mode decomposition (DMD) were used to analyze the mechanism behind this phenomenon. The analysis results showed that flexible appendages based on CWT had an inhibitory effect on large-scale flow, and this effect gradually decreased with increasing appendage length. The results indicate that the flexible appendages can disrupt the wake vortex structure, reduce vortex energy, and facilitate the transition from large-scale vortex to small-scale vortex. Additionally, excessive disturbance is generated in the wake region when the flexible appendage is too long, hindering the shedding of small-scale vortices and resulting in an increase.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142357783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contactless thermal diffusivity characterization of second order magnetocaloric materials under magnetic field using modulated photo-thermal radiometry method with very low power probe beam","authors":"","doi":"10.1016/j.expthermflusci.2024.111321","DOIUrl":"10.1016/j.expthermflusci.2024.111321","url":null,"abstract":"<div><p>The thermal diffusivity of magnetocaloric materials has a transition point at a given temperature that depends on the intensity of the applied magnetic field. Consequently, a fine temperature resolution on the material sample is needed to obtain an accurate determination of the thermal diffusivity variation with temperature. The coupling between the external and the internal fields has to be carefully mastered since the pertinent operating condition is fixed by the actual internal field which is not directly measurable and may be heavily affected by any element in contact with the sample. Therefore, contactless methods such as Photo-Thermal Radiometry (PTR) are privileged. The latter is based on a radiative excitation of the front face of a thin sample and the detection of the thermal effect on the opposite face. However, the powerful radiative source may significantly increase the sample temperature which is not suitable for caloric materials. In this work, a low power modulated PTR method is proposed to characterize second order magnetocaloric materials under magnetic field. It was compared to high energy thermo-flash PTR and validated on common materials such as steel and stainless steel, and then applied to gadolinium which is the reference magnetocaloric material for magnetic refrigeration and heat pumping study. The thermal diffusivity of gadolinium samples is measured in the 285.1 K to 305.1 <!--> <!-->K temperature range, including the magnetic transition temperature without and under an external magnetic flux density of 0.5 T in the 13 mm air gap of the permanent magnet magnetic circuit. The low power probe beam ensures a temperature stability with a negligible sample temperature fluctuation less than 0.05 K on the incident sample surface and less than 0.03 K on the measurement surface. The experimental results without magnetic field align with those using other methods including the magnetic transition temperatures determination. This low-power optical method proved its efficiency to characterize highly temperature dependent materials such as magnetocaloric materials sensitive to magnetic field. The data obtained partly fills the lack of information in the literature on excited gadolinium.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142274549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measurement of local Nusselt number and local recovery factor for impinging multiple compressible jets","authors":"","doi":"10.1016/j.expthermflusci.2024.111320","DOIUrl":"10.1016/j.expthermflusci.2024.111320","url":null,"abstract":"<div><div>In the present study the appropriate reference temperature is identified for the compressible impinging jet. Using the measured reference temperature, local recovery factor is calculated. The steady state thin metal foil technique is used for the measurement of target plate temperature. In this study, the effect of Mach number (<em>Ma</em>) at a constant Reynolds number (<em>Re</em>) and the combined effect of Mach number and Reynolds number on the heat transfer rate are investigated. For both the cases, jet-to-plate distance is varied from <em>z/d</em> = 5 to 12. For the first case (effect of Mach number at a constant <em>Re</em> = 20,000), <em>Ma</em> is varied from 0.15 to 0.85. In the second case (combined effect of Mach number and Reynolds number), <em>Ma</em> is varied from 0.2 to 0.78 and the corresponding <em>Re</em> variation is 7200 to 29,000. At a constant Reynolds number, the heat transfer coefficient increases with the increase in the Mach number. For a given Mach number and Reynolds number, the heat transfer rate decreases with the increase in the jet-to-plate distance. The recovery factor remains unaffected by the Mach number and jet-to-plate distance in the case of the concurrent variation of the Mach number and Reynolds number.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An experimental acoustofluidic system for analyzing boundary-driven acoustic streaming generated by flat and curved walls","authors":"","doi":"10.1016/j.expthermflusci.2024.111319","DOIUrl":"10.1016/j.expthermflusci.2024.111319","url":null,"abstract":"<div><p>While boundary-driven acoustic streaming in fluids surrounded by flat walls has been extensively studied in the literature, theoretical studies on boundary-driven acoustic streaming generated by curved walls have recently emerged. This paper aims to present a quantitative analysis of acoustic streaming fields driven by forces induced by both flat and curved walls. A semi-circular channel made of stainless steel was designed to serve as a model channel with both flat and curved boundaries. A multi-layered glass-steel-glass device, actuated by a piezoelectric transducer, was assembled for experimental characterization of boundary-driven acoustic streaming in such scenarios. First, the various standing acoustic modes in the semi-circular channel were measured through the acoustophoretic patterning of 20 µm polystyrene particles. Next, the acoustic radiation force fields and boundary-driven acoustic streaming patterns under various resonant acoustic modes were characterized through micro-particle-image-velocimetry measurements of the motion of 20 µm and 1 µm polystyrene particles, respectively. Finally, the experimental results were explained using efficient finite element simulations of acoustofluidics and acoustophoresis in a semi-circular reduced-fluid model, with a focus on analyzing the streaming velocities driven by the flat and curved walls. Both experimental and numerical results demonstrated that the ratio of streaming velocities induced by the flat wall and the curved wall in this semi-circular channel depends on the resonant acoustic modes. This research highlights the diverse boundary-driven acoustic streaming patterns that arise in irregular channels and provides a theoretical foundation for choosing strategies for shape optimization to suppress acoustic streaming in acoustofluidic devices.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142242042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Free surface vortex and associated air entrainment during liquid drainage using two outlets","authors":"","doi":"10.1016/j.expthermflusci.2024.111314","DOIUrl":"10.1016/j.expthermflusci.2024.111314","url":null,"abstract":"<div><p>Plughole vortex dynamics and the corresponding air entrainment is of paramount importance in various process industries. The present study experimentally investigates plughole vortex induced air entrainment during the drainage of water through two closely spaced outlets from a tank. The discharge from the two outlet tubes has been modulated and the different stages of air entrainment including formation of air lamella, periodic slug bubble pinch-off, and transition into the stable annular flow are observed. The transition between the slug bubble pinch-off and the stable annular flow has been modelled by balancing the local dynamic pressure of the fluid and the Laplacian pressure jump across the gas-liquid interface. The balance yields the ratio of critical height, <span><math><mrow><msub><mi>H</mi><mi>c</mi></msub></mrow></math></span> and radius of the stable air neck, <span><math><mrow><msub><mi>r</mi><mi>m</mi></msub></mrow></math></span> as <span><math><mrow><msub><mi>H</mi><mi>c</mi></msub><mo>/</mo><msub><mi>r</mi><mi>m</mi></msub><mo>≈</mo><mn>30.68</mn><msup><mrow><mi>Bo</mi></mrow><mrow><mo>-</mo><mn>0.904</mn></mrow></msup><msup><mrow><mfenced><mrow><mi>f</mi><mrow><mfenced><mrow><mi>D</mi><mo>,</mo><msub><mi>r</mi><mi>e</mi></msub></mrow></mfenced></mrow></mrow></mfenced></mrow><mrow><mo>-</mo><mn>0.210</mn></mrow></msup></mrow></math></span>, with the Bond number, <span><math><mrow><mi>Bo</mi><mo>=</mo><mi>Δ</mi><mi>ρ</mi><mi>g</mi><msup><mrow><mi>D</mi></mrow><mn>2</mn></msup><mo>/</mo><mi>σ</mi></mrow></math></span> and the geometric parameter, <span><math><mrow><mi>f</mi><mrow><mfenced><mrow><mi>D</mi><mo>,</mo><msub><mi>r</mi><mi>e</mi></msub></mrow></mfenced></mrow><mo>=</mo><msup><mrow><mfenced><mrow><mn>1</mn><mo>-</mo><mfrac><msub><mrow><mn>2</mn><mi>r</mi></mrow><mi>e</mi></msub><mi>D</mi></mfrac></mrow></mfenced></mrow><mn>2</mn></msup></mrow></math></span>.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142274548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SAMPO-P: A prototypical scale low-temperature experiment on two-layer melt pool heat transfer in LWR lower head","authors":"","doi":"10.1016/j.expthermflusci.2024.111303","DOIUrl":"10.1016/j.expthermflusci.2024.111303","url":null,"abstract":"<div><div>To better understand the thermal behavior of a two-layer melt pool with a high Rayleigh number—a pattern observed in the RASPLAV study, which indicates a significant risk to pressure vessel integrity and the success of in-vessel retention (IVR) strategies—this paper reports experimental findings from a 2D, full-scale (1:1 ratio) prototypical stratified melt pool (SAMPO-P). A series of experimental tests were carried out with varying heating powers and top layer heights, achieving a Rayleigh number of <span><math><mrow><mn>3.77</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mn>15</mn></msup></mrow></math></span>, comparable to that found in light water reactors (LWR). Water was used to simulate the bottom layer, while n-octanol represented the top layer. Internal decay heat was modeled in the bottom layer using electric heating rods. After analyzing the main heat transfer parameters from the experiment, this paper derived several useful heat transfer correlations. The normalized temperature and heat flux distributions remained consistent across different power levels, and the normalized heat flux in the bottom layer aligned well with existing experimental correlations. In the bottom layer, the downward heat transfer coefficient was lower compared to other single-layer correlations, likely due to increased upward heat transfer.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Twelfth Mediterranean Combustion Symposium","authors":"","doi":"10.1016/j.expthermflusci.2024.111317","DOIUrl":"10.1016/j.expthermflusci.2024.111317","url":null,"abstract":"","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}