Academic literature on the topic 'Shock-Spray interaction'
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Journal articles on the topic "Shock-Spray interaction"
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Gärtner, Jan Wilhelm, Ye Feng, Andreas Kronenburg, and Oliver T. Stein. "Numerical Investigation of Spray Collapse in GDI with OpenFOAM." Fluids 6, no. 3 (March 4, 2021): 104. http://dx.doi.org/10.3390/fluids6030104.
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During certain operating conditions in spark-ignited direct injection engines (GDI), the injected fuel will be superheated and begin to rapidly vaporize. Fast vaporization can be beneficial for fuel–oxidizer mixing and subsequent combustion, but it poses the risk of spray collapse. In this work, spray collapse is numerically investigated for a single hole and the spray G eight-hole injector of an engine combustion network (ECN). Results from a new OpenFOAM solver are first compared against results of the commercial CONVERGE software for single-hole injectors and validated. The results corroborate the perception that the superheat ratio Rp, which is typically used for the classification of flashing regimes, cannot describe spray collapse behavior. Three cases using the eight-hole spray G injector geometry are compared with experimental data. The first case is the standard G2 test case, with iso-octane as an injected fluid, which is only slightly superheated, whereas the two other cases use propane and show spray collapse behavior in the experiment. The numerical results support the assumption that the interaction of shocks due to the underexpanded vapor jet causes spray collapse. Further, the spray structures match well with experimental data, and shock interactions that provide an explanation for the observed phenomenon are discussed.
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Wu, Wangxia, Bing Wang, and Gaoming Xiang. "Impingement of high-speed cylindrical droplets embedded with an air/vapour cavity on a rigid wall: numerical analysis." Journal of Fluid Mechanics 864 (February 15, 2019): 1058–87. http://dx.doi.org/10.1017/jfm.2019.55.
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The high-speed impingement of hollow droplets embedded with a cavity has fundamental applications in various scenarios, such as in spray coating and biomedical engineering. The impingement dynamics is modulated by the wrapping medium, different from that of denser solid droplets. With air and vapour cavities, the impingement of two kinds of hollow cylindrical droplets is simulated in the present study to investigate the morphology and physical mechanisms regarding droplet and cavity dynamics. The compressible two-phase Eulerian model is used to couple with the phase transition procedure. The results detail the evolution of droplets and collapsing dynamics of the two kinds of cavities. Processes are captured in which the impinging water-hammer shock wave interacts with the cavity, and vertical liquid jets are induced to impact the embedded cavity. For the case of the air cavity, a transmitted shock wave is formed and propagates inside the cavity. The air cavities are compressively deformed and broken into a series of small cavities. Subsequently, a range of intermittent collapsing compression wavelets are generated due to the interface collapse driven by local jets. As for the vapour cavity in the saturated state, initially, once it is impacted by the impinging shock wave, it gradually shrinks accompanied by local condensation but without generation of transmitted waves. Following the first interaction between the lower and upper surfaces of the cavity, the vapour cavity undergoes continuous condensation and collapse with repeated interface fusion. The vapour cavity finally turns into liquid water blended into the surroundings, and the strong collapsing shock waves are expanded inside the droplet. The radius ratios and initial impinging speeds are chosen to analyse the variation of the collapsing time, maximum collapsing pressure and mean pressure on the rigid wall. The pressure withstood by the wall due to the collapsing cavity increases with the initial size of the cavity and initial impinging speed. The maximum local pressures in the entire fluids and the mean pressure on the wall during the collapsing of the vapour cavities are higher than those for the air cavities.
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Mardoukhi, Ahmad, Mikko Hokka, and Veli-Tapani Kuokkala. "Experimental study of the dynamic indentation damage in thermally shocked granite." Rakenteiden Mekaniikka 51, no. 1 (August 16, 2018): 10–26. http://dx.doi.org/10.23998/rm.69036.
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This paper presents an experimental procedure to study the effects of pre-existing cracks and damage on the rock behavior under dynamic indentation. To gain better understanding on the mechanism involved in percussive-rotary drilling procedure, a modified Split Hopkinson Pressure Bar device was used to carry out dynamic indentation tests, where rock drill buttons were impacted on rock samples with dimensions of 30 cm × 30 cm × 30 cm. Before the mechanical testing, the samples were thermally shocked using a plasma spray gun for periods of 3, 4, and 6 seconds. The plasma gun produces a powerful heat shocks on the rock sample, and even short exposures can change the surface structure of the samples and provide samples with different crack patterns and surface roughness for experimental testing. The effects of the heat shock damage on the dynamic indentation behavior of the rock were characterized with single- and triple-button indentation tests. The specific destruction work was used to characterize the effects of heat shocks on the material removal during dynamic indentation. The results show that the force-displacement response of the rock does not change much even if the rock surface is severely damaged by the heat shock, however, the destruction work decreases significantly. This means that the same loading removes more volume if the material surface is pre-damaged, and that the efficiency of the indentation process cannot be evaluated from the bit-rock interaction forces alone. The presented experimental framework can be a useful tool for the verification of numerical models where the rock microstructure and especially the microcracks are essential.
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Zhang, Jingyu, Yanfei Li, Hongming Xu, Xiao Ma, and Shijin Shuai. "Investigation into shock-to-shock interactions induced by flash boiling and the impact on spray behaviors." Fuel 337 (April 2023): 127120. http://dx.doi.org/10.1016/j.fuel.2022.127120.
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Quan, Jin, Xinyuan Li, Zewei Li, Meifang Wu, Biao Zhu, Seung-Beom Hong, Jiang Shi, Zhujun Zhu, Liai Xu, and Yunxiang Zang. "Transcriptomic Analysis of Heat Stress Response in Brassica rapa L. ssp. pekinensis with Improved Thermotolerance through Exogenous Glycine Betaine." International Journal of Molecular Sciences 24, no. 7 (March 29, 2023): 6429. http://dx.doi.org/10.3390/ijms24076429.
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Chinese cabbage (Brassica rapa L. ssp. pekinensis) is sensitive to high temperature, which will cause the B. rapa to remain in a semi-dormancy state. Foliar spray of GB prior to heat stress was proven to enhance B. rapa thermotolerance. In order to understand the molecular mechanisms of GB-primed resistance or adaptation towards heat stress, we investigated the transcriptomes of GB-primed and non-primed heat-sensitive B. rapa ‘Beijing No. 3’ variety by RNA-Seq analysis. A total of 582 differentially expressed genes (DEGs) were identified from GB-primed plants exposed to heat stress relative to non-primed plants under heat stress and were assigned to 350 gene ontology (GO) pathways and 69 KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways. The analysis of the KEGG enrichment pathways revealed that the most abundantly up-regulated pathways were protein processing in endoplasmic reticulum (14 genes), followed by plant hormone signal transduction (12 genes), ribosome (8 genes), MAPK signaling pathway (8 genes), homologous recombination (7 genes), nucleotide excision repair metabolism (5 genes), glutathione metabolism (4 genes), and ascorbate and aldarate metabolism (4 genes). The most abundantly down-regulated pathways were plant-pathogen interaction (14 genes), followed by phenylpropanoid biosynthesis (7 genes); arginine and proline metabolism (6 genes); cutin, suberine, and wax biosynthesis (4 genes); and tryptophan metabolism (4 genes). Several calcium sensing/transducing proteins, as well as transcription factors associated with abscisic acid (ABA), salicylic acid (SA), auxin, and cytokinin hormones were either up- or down-regulated in GB-primed B. rapa plants under heat stress. In particular, expression of the genes for antioxidant defense, heat shock response, and DNA damage repair systems were highly increased by GB priming. On the other hand, many of the genes involved in the calcium sensors and cell surface receptors involved in plant innate immunity and the biosynthesis of secondary metabolites were down-regulated in the absence of pathogen elicitors in GB-primed B. rapa seedlings. Overall GB priming activated ABA and SA signaling pathways but deactivated auxin and cytokinin signaling pathways while suppressing the innate immunity in B. rapa seedlings exposed to heat stress. The present study provides a preliminary understanding of the thermotolerance mechanisms in GB-primed plants and is of great importance in developing thermotolerant B. rapa cultivars by using the identified DEGs through genetic modification.
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Barradas, S., V. Guipont, R. Molins, M. Jeandin, M. Arrigoni, M. Boustie, C. Bolis, L. Berthe, and M. Ducos. "Laser Shock Flier Impact Simulation of Particle-Substrate Interactions in Cold Spray." Journal of Thermal Spray Technology 16, no. 4 (September 26, 2007): 548–56. http://dx.doi.org/10.1007/s11666-007-9069-9.
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Zhang, Jingyu, Yanfei Li, Hongming Xu, Yang Liu, Xiao Ma, and Shijin Shuai. "General understanding on spray collapse process of an asymmetrical multi-hole direct injection gasoline injector under wide flash-boiling conditions." International Journal of Engine Research, December 14, 2023. http://dx.doi.org/10.1177/14680874221149244.
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How the under-expansion impacts the flash-boiling spray collapse process over wide superheat levels ( Rp, defined as the ratio of saturation pressure to ambient pressure) is not well understood. In the present study, n-hexane flash-boiling sprays issued from a five-hole asymmetrical injector were experimentally and numerically studied to obtain a more general understanding of the spray collapse with wide Rp variation. The experimental results proved that the collapse in the transitional region occurs in the far field, unlike the fully collapse that occurred in the near-nozzle region. The numerical results demonstrated the complexity of individual jet evolutions and their interactions over wide Rp. For individual flash-boiling jets, there were different behaviors in the near-nozzle region. In the case with Rp slightly larger than 1, no shock waves can be observed, but a set of compression-expansion chains. The further increase in Rp caused the generation of shock waves, and resultantly the primary cells were established. For the multi-jet sprays, the further increase in Rp enlarged the primary cells, leading to their interactions and the generation of secondary cells. When Rp was sufficiently higher, the further interactions among primary and secondary cells could cause the generation of tertiary cell. Orderly interactions of shock cells were observed with increasing Rp, that is, the interactions initially occur between the adjacent jets with smaller distances, and then other jets were involved. Based on the results: It was found that the compression-expansion chains caused the low- Rp flash-boiling spray collapse in the far field; With the increase in Rp, the shock waves and shock-to-shock interaction become the main contributor to spray collapse, leading collapse appearing in the near-nozzle region.
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Takana, Hidemasa, Kazuhiro Ogawa, Tetsuo Shoji, and Hideya Nishiyama. "Computational Simulation on Performance Enhancement of Cold Gas Dynamic Spray Processes With Electrostatic Assist." Journal of Fluids Engineering 130, no. 8 (July 30, 2008). http://dx.doi.org/10.1115/1.2907417.
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A real-time computational simulation on the entire cold spray process is carried out by the integrated model of compressible flow field, splat formation model, and coating formation model, in order to provide the fundamental data for the advanced high performance cold gas dynamic spray process with electrostatic acceleration. In this computation, viscous drag force, flow acceleration added mass, gravity, Basset history force, Saffman lift force, Brownian motion, thermophoresis, and electrostatic force are all considered in the particle equation of motion for the more realistic prediction of in-flight nano∕microparticle characteristics with electrostatic force and also for the detailed analysis of particle-shock-wave-substrate interaction. Computational results show that electrostatic acceleration can broaden the smallest size of applicable particle diameter for successful adhesion; as a result, wider coating can be realized. The utilization of electrostatic acceleration enhances the performance of cold dynamic spray process even under the presence of unavoidable shock wave.
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Siddappa, C., O. Thomine, M. S. Shadloo, G. Gai, and A. Hadjadj. "Interactions of shock waves with polydisperse particle clouds: Effects on mitigation and topological heterogeneity." Physics of Fluids 36, no. 5 (May 1, 2024). http://dx.doi.org/10.1063/5.0205854.
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This study explores the efficiency of employing a particle-spray cloud to mitigate shock wave propagation, which is essential in various industrial applications, especially in preventing potential hydrogen explosions within nuclear reactor containment buildings. Numerical simulations, primarily in one- and two-dimensional configurations, are utilized to examine the interaction between shock waves and a cloud of polydisperse particles, considering both air and hydrogen–air mixtures as carrier gases. A novel reduced-order theoretical model is developed to analyze the dispersion pattern of polydisperse particles, with validation conducted through direct numerical simulations. Results demonstrate that the polydispersion of cloud particles significantly reduces shock wave propagation compared to monodisperse particles. Notably, particles with smaller diameters and higher standard deviations (σ) show increased attenuation effects. Additionally, scenarios with higher particle volume fractions (τv,0) contribute to enhanced shock wave attenuation. A critical incident Mach number is identified, indicating a significant change in shock wave transmission from supersonic to subsonic when Ms<2.8.
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Ahamed, Sheikh, and Song-Charng Kong. "Analysis of Thermomechanical Stress of High-Temperature Ignition Surface Caused by Drop-Wall Interaction at Engine Conditions." Journal of Thermal Science and Engineering Applications, February 20, 2024, 1–28. http://dx.doi.org/10.1115/1.4064820.
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Abstract Drop-wall interaction is an important phenomenon in various industrial applications. The liquid droplets can impinge on the high-temperature wall, causing thermal shock because of a sudden temperature change. The change in temperature in the solid wall can induce thermal stress. When the thermal stress exceeds the strength of the material in that stress mode, failure can occur. Hence, it is essential to investigate the temperature evolution on the high-temperature surface to optimize the durability of the material. In this paper, drop-wall interactions in the engine environment are studied. The Smoothed Particle Hydrodynamics (SPH) method is used to simulate the impingement of fuel droplets on an ignition plug with different materials to characterize the heat transfer, thermal penetration, and temperature distributions in the heated wall. This paper also investigates the behavior of ceramic material (i.e., silicon nitride) for thermomechanical stress and its durability based on the stress-number of cycles (S-N) curve. Thermal stress is calculated based on the temperature gradient and material properties, while mechanical stress is evaluated based on the bending momentum and momentum flux induced by the spray. A parametric study was conducted for various materials, including wolfram carbide, iron, stainless steel, carbon steel, and aluminum. Results show that ceramic materials have the lowest thermal stress distribution and best durability.
Dissertations / Theses on the topic "Shock-Spray interaction"
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Siddappa, Chethan. "Numerical simulation of the attenuation of hydrogen explosion by spraying water." Electronic Thesis or Diss., Normandie, 2025. http://www.theses.fr/2025NORMIR03.
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Les ondes de choc à haute pression sont cruciales dans de nombreux processus industriels et environnementaux impliquant l'énergie hydrogène. Les explosions d'hydrogène posent des risques importants pour les structures et la sécurité humaine, faisant des systèmes de pulvérisation d'eau une solution essentielle, notamment pour le confinement des réacteurs nucléaires. Ce manuscrit étudie les interactions entre les ondes de choc et les sprays d'eau pour atténuer les explosions d'hydrogène à l'aide de modélisations multiphasiques avancées. Les premières simulations numériques dans des configurations unidimensionnelles et bidimensionnelles se concentrent sur le transfert de quantité de mouvement, en analysant les forces de traînée exercées sur des particules polydispersées dans des mélanges d'air et d'air-hydrogène. Un modèle théorique d'ordre réduit a été développé pour étudier la topologie de dispersion, validé par des simulations numériques directes. Les résultats montrent que les nuages de particules polydispersées améliorent significativement l'atténuation des ondes de choc par rapport aux configurations monodispersées, avec des diamètres plus petits et une plus grande déviation standard σ produisant des effets plus marqués. Des fractions volumiques de particules plus élevées Ƭv,₀ amplifient davantage l'atténuation. Un nombre de Mach incident critique (Mₛ < 2,8) a été identifié, où l'onde de choc transmise passe de l'état supersonique à subsonique. En développant l'investigation initiale du transfert de quantité de mouvement lors des interactions entre les ondes de choc et les gouttelettes, la phase suivante de l'étude introduit des mécanismes de transfert de chaleur et d'évaporation pour analyser de manière exhaustive l'atténuation des ondes de choc multiphasiques. Les résultats révèlent que l'intégration du transfert de chaleur et de l'évaporation améliore considérablement l'atténuation des ondes de choc, avec des petites gouttelettes dans des configurations hautement polydispersées et denses favorisant une évaporation plus rapide grâce à leur surface cumulative plus grande, conduisant à une dissipation efficace de l'énergie et à une atténuation améliorée. L'analyse montre une relation linéaire entre le nombre de Mach de choc transmis à saturation (Mₛₜ)ₛₐₜ et le nombre de Mach incident Mₛ. Une corrélation empirique a été développée pour prédire (Mₛₜ)ₛₐₜ en fonction du nombre de Mach incident Ms et du diamètre des gouttelettes. Ce travail offre une analyse approfondie des interactions multiphasiques dans les environnements chargés de gouttelettes et souligne l'efficacité des sprays d'eau comme stratégie pour réduire les risques d'explosion d'hydrogène dans les contextes industriels et nucléairesHigh-pressure blast waves are critical in many industrial and environmental processes involving hydrogen energy. Accidental shock waves from hydrogen explosions pose significant risks to structural integrity and human safety, making water spray systems a vital strategy for mitigating such hazards, particularly in nuclear reactor containment scenarios. This manuscript investigates shock-spray interactions to mitigate hydrogen explosions through advanced multiphase modeling. The study examines the coupled effects of momentum, heat, and mass transfer during shock-wave interactions with water sprays, a proven strategy for explosion attenuation. Initial numerical simulations in one- and two - dimensional configurations focus on momentum transfer, analyzing drag forces on polydisperse particles in air and hydrogen-air mixtures. A reduced-order theoretical model is developed to study dispersion topology, validated against direct numerical simulations. Results show that polydisperse particle clouds significantly enhance shock attenuation compared to monodisperse ones, with smaller diameters and higher standard deviation σ exhibiting stronger effects. Greater particle volume fractions Ƭv,₀ further amplify attenuation. A critical incident Mach number (Mₛ< 2.8) is identified, where the transmitted shock transitions from supersonic to subsonic states. Expanding upon the initial investigation of momentum transfer during shock-droplet interactions, the subsequent phase of the study introduces heat transfer and evaporation mechanisms to comprehensively analyze multiphase shock wave attenuation. The results reveal that incorporating heat transfer and evaporation significantly enhances shock attenuation, with smaller droplets in highly polydisperse and dense configurations promoting faster evaporation due to their larger cumulative surface area, leading to efficient energy dissipation and improved mitigation. The analysis reveals a linear relationship between the saturated transmitted shock Mach number, (Mₛₜ)ₛₐₜ, and the incident Mach number, (Mₛ). An empirical correlation was developed to predict (Mₛₜ)ₛₐₜ as a function of incident Mach number (Mₛ) and droplet diameter. This work provides a detailed understanding of multiphase interactions in droplet-laden environments and highlights the potential of water sprays as a robust mitigation strategy for hydrogen explosion risks in industrial and nuclear safety contexts
Book chapters on the topic "Shock-Spray interaction"
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Gärtner, Jan Wilhelm, Daniel D. Loureiro, and Andreas Kronenburg. "Modelling and Simulation of Flash Evaporation of Cryogenic Liquids." In Fluid Mechanics and Its Applications, 233–50. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09008-0_12.
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AbstractRocket engine manufacturers attempt to replace toxic, hypergolic fuels by less toxic substances such as cryogenic hydrogen and oxygen. Such components will be superheated when injected into the combustion chamber prior to ignition. The liquids will flash evaporate and subsequent mixing will be crucial for a successful ignition of the engine. We now conduct a series of DNS and RANS-type simulations to better understand this mixing process including microscopic processes such as bubble growth, bubble-bubble interactions, spray breakup dynamics and the resulting droplet size distribution. Full scale RANS simulations provide further insight into effects associated with flow dynamic such as shock formation behind the injector outlet. Capturing these gas dynamic effects is important, as they affect the spray morphology and droplet movements.
Conference papers on the topic "Shock-Spray interaction"
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Barradas, S., R. Molins, M. Jeandin, M. Arrigoni, M. Boustie, C. Bolis, L. Berthe, and M. Ducos. "Laser Shock Flier Impact Simulation of Particle-Substrate Interactions in Cold Spray." In ITSC2005, edited by E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p0343.
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Abstract Coating-substrate adhesion in cold spray is a paramount property, the mechanisms of which are not yet well elucidated. These mechanisms are governed by metallurgical and morphological phenomena occuring when cold-sprayed particles impinge on the substrate. To go into these mechanisms, due to the intrinsic characteristics of the cold spray process, i.e. the low-temperature and high velocity of the particles, direct observation and control of inflight particles and related phenomena (especially when impinging) cannot be done easily. For this reason, an experimental simulation of the particle-substrate reactions at the particle impingement was developed. This simulation is based on original filter impact experiments from laser shock acceleration of plates/foils (fliers). These were applied to the Cu-Al metallurgically-reactive system to simulate Cu cold-sprayed onto Al. The velocity of the plate was selected in the range of actual cold spray velocities. Relevant Cu-Al interaction phenomena were featured and studied as a function of filter impact conditions, i.e., primarily, shearing, plastic deformation, phase transformation (including rapid melting/solidification and formation of intermetallics). These phenomena were shown to be similar to those involved in cold spray. This was ascertained by a parallel study of cold-sprayed Cu coating of Al using SEM, TEM, EPMA, and an energy balance and diffusion calculations. In addition, this simulation can be used to feed FE modeling of cold spray particle impingement on the substrate. Preliminary results are discussed from modeling using the “RADIOSS®” code. More generally, laser shock flier impact experiments were demonstrated to result in a powerful tool capable of simulating cold spray coating-substrate interface mechanisms. Major assets rest on their high significance, reproducibility, flexibility and potential for substituting for direct laborious cold spray optimization testing.
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Dammati, Sai Sandeep, Alexei Poludnenko, Nikolaos Kateris, Wendi Dong, Hai Wang, and Tianfeng Lu. "Numerical Simulations of Non-Ideal Spray Detonations in Jet Fuels With a Shock-Droplet Interaction Model." In AIAA SCITECH 2025 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2025. https://doi.org/10.2514/6.2025-0388.
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Takana, Hidemasa, Kazuhiro Ogawa, Tetsuo Shoji, and Hideya Nishiyama. "Optimization of Cold Gas Dynamic Spray Processes by Computational Simulation." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37081.
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An integrated model of compressible thermofluid, splat formation and coating formation for a cold dynamic spray process has been established. In-flight behavior of nano-micro particles and the interaction between the shock wave and the particles in a supersonic jet flow impinging onto the substrate and further particle acceleration with electrostatic force are clarified in detail by considering viscous drag force, flow acceleration, added mass, gravity, Basset history force, Saffman lift force, Brownian motion, thermophoresis and electrostatic force. The effect of electrostatic acceleration becomes more significant with the decrease in particle diameter even in the presence of unavoidable shock wave. As a result, electrostatic acceleration can broaden the application range of operating particle diameter in a cold gas dynamic spray process to form a robust and activated coating. Finally, based on the integrated model, the coating thickness characteristics in an electrostatic assisted cold dynamic spray process are evaluated.
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Refke, A., G. Barbezat, J. L. Dorier, M. Gindrat, and Ch Hollenstein. "Characterization of LPPS Processes Under Various Spray Conditions for Potential Applications." In ITSC2003, edited by Basil R. Marple and Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p0581.
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Abstract Low Pressure Plasma Spraying (LPPS) is nowadays a well-established thermal spray process with a broad variety of important applications for functional surface coatings. The operating pressure for LPPS processes can vary in a wide range from typically 200 mbar down to only a few mbar. This leads to unconventional properties of the plasma jet, in terms of supersonic flow with strong shock structure at moderate pressure, towards rarefaction and frozen flow at very low pressure. In order to optimize and control the spray processes for specific applications, it is necessary to understand the underlying physical mechanisms. However, so far only limited knowledge has been established on the plasma jet properties and its interaction with the spray particles in LPPS conditions. We present several experimental investigations to characterize plasma spray processes under various pressure conditions. Measured plasma jet properties using a dedicated enthalpy probe system and imaging are combined with IR-pyrometry and velocimetry on the particles (DPV2000) to further improve the understanding of the plasma particle interactions. These results, along with spray deposit characterization, can be used to optimize the coating properties and explore further potential applications.
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Takana, H., K. Ogawa, T. Shoji, and H. Nishiyama. "Electrostatic Assist on a Cold Spray Process by Computational Simulation." In ITSC2007, edited by B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima, and G. Montavon. ASM International, 2007. http://dx.doi.org/10.31399/asm.cp.itsc2007p0090.
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Abstract The integrated model of thermofluid, splat formation and coating formation for a cold spray process has been established. The in-flight behavior of micro and submicron particles, the interaction between shock wave and particles in a supersonic jet impinging onto the substrate are clarified by this integrated model in detail. Then, the effect of electrostatic force on the particle acceleration is discussed in detail by carrying out a real-time computational simulation. It is shown that coating can be formed with the assist of electrostatic acceleration even though there is a lack of particle acceleration over critical velocity only through momentum transfer from airflow. Thus, the utilization of electrostatic acceleration enhances the performance of cold spray coating and contributes the extension of application range of a cold spray process.
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Papyrin, A. N., A. P. Alkhimov, V. F. Kosarev, and S. V. Klinkov. "Experimental Study of Interaction of Supersonic Gas Jet With a Substrate Under Cold Spray Process." In ITSC2001, edited by Christopher C. Berndt, Khiam A. Khor, and Erich F. Lugscheider. ASM International, 2001. http://dx.doi.org/10.31399/asm.cp.itsc2001p0423.
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Abstract The interaction of the supersonic gas jets of rectangular section with a flat obstacle under conditions of the Cold Spray process was studied. Pressure distribution on the obstacle surface at various jet regimes is measured. Instability of the jet as well as compressed layer structure is observed with the aid of laser Schlieren visualization. Depending on jet pressure ratio, distance between nozzle exit and the obstacle various modes of the jet are registered including classical mode, the mode with peripheral maximum and circulate bands, the mode with oscillations of bow shock, and the mode with jet oscillations. It is shown that the distribution of pressure along the smaller size of the nozzle is self-similar in the classic regime of the impingement and does not depend on the angle of encounting at φ= 50 - 90°. The critical parameters of the gas, when it accelerates along the surface, are reached near the boundary of the falling jet. The distributions of the stagnation temperature and heat transfer coefficient in the near-wall jet at various stand-off distances are experimentally obtained. It is shown that the experimental data on the heat transfer coefficient are higher than the calculated ones, and this difference can be explained by velocity fluctuations in the vicinity of the stagnation point and in the near wall jet.
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Tropea, Cam, and Ilia V. Roisman. "Spray Impact Onto a Rigid Wall: Modelling Strategy." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31392.
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The common approach to the modelling of spray impact is to treat the phenomenon as a simple superposition of single drop impact events [1]. The main input for such model formulation is obtained either from experimental [2,3] or theoretical [4,5,6] studies of the impact of a single drop onto a dry wall, onto a uniform, undisturbed liquid film or into a deep pool [7]. However, in [8] it was shown that this conventional approach is not universal in the description of the spray impact and that in the case of relatively dense sprays, the interaction of crowns (Fig. 1) and the oscillations of the liquid-wall film must be taken into account. For example, these interactions result in the emerging of uprising jets during spray impingement of the diesel spray (see Fig. 2). In the study of spray impact we have chosen the following strategy of the modelling: 1. Description (experimental and theoretical) of single dropimpact. Determining of the parameters influencing the splash. 2. Description of the interaction of two drops on the wall surface. 3. Determining of the parameters of the single drop impacts influencing the dynamics of the film formed on the wall. Characterization of the film: the time averaged thickness, the time averaged velocity and its fluctuations. 4. Description of the influence of the oscillating motion of the film on the outcome from a single drop impact. Single drop impact onto a wetted wall—The motion of a kinematic discontinuity in the liquid film on the wall due to the drop impact, the formation of the uprising jet at this kinematic discontinuity and its elevation are analyzed. The theory [4] for the propagation of the kinematic discontinuity is generalized for the case of arbitrary velocity vectors in the inner and outer liquid films on the wall. Next, the mass, momentum balance and Bernoulli equations at the base of the crown are considered to obtain the velocity and the thickness of the jet on the wall. An analytical solution for the crown shape is obtained in the asymptotic case of such high impact velocities that the surface tension and the viscosity effects can be neglected in comparison to inertial effects. The edge of the crown is described by the motion of a rim, formed due to the surface tension. The theoretical predictions of the height of the crown are compared with experiments. The agreement is rather good in spite of the fact that no adjustable parameters are used (see Fig. 3). Three different cases are considered: normal axisymmetric impact of a single drop, oblique impact of a single drop, and impact and interaction of two drops. Next, two new parameters of single drop impact influencing the dynamics of the film formed due to the polydisperse spray impact are identified. The first one is associated with the relative presence of the crown on the film surface and allowing one to estimate the probability of crown interactions. The second parameter is associated with the axial momentum in the plane of the wall. Time-averaged film motion—The theory of the creation of the film by spray can be subdivided into three main parts: 1. The characterization of the spray, particularly definition of the flux vectors of scalar properties (number flux vector, volume flux vector, etc.) and the momentum flux tensor. 2. Boundary conditions at the time-averaged spray/film boundary. 3. Dynamics of the film motion on the wall. The mass and momentum equations of the film are formulated accounting for the volume flux of the spray, the dynamic pressure, and the time-averaged stress vector at the film “free” surface caused by the inertia of the spray. The inertial terms of the liquid in the film contains of the inertia of the time-averaged motion and the inertia of film oscillations. These oscillations are modelled as an ensemble of the radial flows in the film associated with the single drop impacts. The probability of the crown interactions is also taken into account. Jetting at the film surface due to impingement of a dense spray—Here we consider impact of such dense sprays that the probability of single crown to propagate without interaction with another crown is very small. The non-uniformities in the dynamic pressure in such sprays yields the significant fluctuations in the film velocity leading to the shocks and jetting (as in the case of the diesel spray impact shown in Fig. 2). We describe the statistically averaged distribution of drop impacts around a given drop assuming that all the impacting drops are distributed randomly in space and in time. The statistically averaged dynamic pressure around given drop is not uniform either in the time or in the radial direction. The self-similar solution for the statistically averaged radial velocity in the film and its thickness (Fig. 4) is obtained. The characteristic time of the instant of shock is estimated. The theoretical predictions of the jets diameter agree with the experimental data in the order of the magnitude.
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Christoulis, D. K., S. Guetta, V. Guipont, M. H. Berger, M. Jeandin, M. Boustie, S. Costil, et al. "Cold Spraying Combined with Laser Surface Pre-Treatment Using Protal." In ITSC2009, edited by B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima, and G. Montavon. ASM International, 2009. http://dx.doi.org/10.31399/asm.cp.itsc2009p1151.
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Abstract In this study, fine aluminum powder was cold sprayed onto aluminum substrates, some of which were polished, some grit blasted, and some pretreated using a nano-pulsed Nd:YAG laser. In the latter case, the laser is coupled with the cold spray gun and the irradiation treatment occurs just prior to deposition. To better understand the interaction mechanisms involved with laser pretreating, coating-substrate interfaces were examined on thin-foil specimens and adhesion strength was determined by laser shock testing. The results show that substrate pretreatment with a nano-pulsed laser significantly improves the coating-substrate interface as well as coating adhesion.
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Reuter, Christopher B., and Douglas A. Schwer. "Spray-Shock Interactions Downstream of a Converging-Diverging Nozzle." In AIAA SCITECH 2025 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2025. https://doi.org/10.2514/6.2025-1773.
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Conahan, Joseph M., Ozan C. Ozdemir, Mohammad E. Taslim, and Sinan Muftu. "A Comparison Between Numerical and Experimental High Reynolds Number Supersonic Jets Generated by Millimeter Scale Converging-Diverging Nozzles." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-24170.
Full textAbstract:
Abstract In thermal spray applications, such as cold spray, an inert gas jet (typically helium or nitrogen) is used to accelerate micron scale particles to supersonic velocities. The complex gas dynamics of these supersonic jets are critical to understand via computational methods for the control of the spray. This work compares supersonic jet waveforms visualized by schlieren imaging with those predicted by computational fluid dynamics (CFD) simulations. A supersonic nitrogen jet is produced by a millimeter scale converging-diverging nozzle with inlet pressures as high as 50 bars. The jet Reynolds numbers based on the nozzle exit diameter and stagnation gas properties range between 60,000 to 325,000. A schlieren visualization setup has been built which shows the first spatial derivative of densities within the flow field. The strong density gradients across the oblique shock waves in the jets allow for clear photographs of the flow pattern of the jets using this schlieren visualization setup. Comparisons between the experiments and the CFD results act as a validation technique for the accuracy of the simulations in terms of the positions and orientations of the oblique shock waves. Through this study, the nozzle internal surface roughness is determined to be a critical parameter in millimeter scale nozzles for the development of the boundary layer. The CFD surface roughness parameters inside the nozzle are incremented until the geometry of the oblique shock waves matches the schlieren images. This work validates the simulation techniques which will be used for future jet simulations, in which shock wave locations and orientations are important, such as jet impingement on a flat plate and particle-shock interactions.