Journal of Applied Fluid Mechanics最新文献

{"title":"Active Air Injection Control to Enhance Performance of Hollow-bladed Axial Fan: A Numerical Study","authors":"A. Bouanik, T. Azzam, N. Abbasnezhad, A. Larabi, M. Mekadem, F. Bakir","doi":"10.47176/jafm.17.3.2201","DOIUrl":"https://doi.org/10.47176/jafm.17.3.2201","url":null,"abstract":"Nowadays, axial fans participate in the most important areas of industry and research, including aviation, navy, wind tunnels, cooling towers, and even automobiles. Thus, more emphasis has been placed on improving their aerodynamic performances. It is important to notice that the parameters involved in designing a fan are mainly concerned with aeraulic power, torque and efficiency. This study investigates the utilization of flow control techniques to improve performances of an axial fan equipped with hollow blades, shroud, and hub. These features grant the fan crucial characteristics, namely, its lightweight and facilitate the blowing action by taking advantage on its hollow parts. The fan's performance is evaluated using a steady RANS numerical model with a k-ω SST turbulence closure, which was validated with experimental data. An active control air blowing through a slot was introduced with various positions and dimensions. The results demonstrate a significant improvement in the fan's performance, with an up to 56% increase in aeraulic power gain, accompanied by changes in the overall flow topology, noticed by closely analyzing the flow structure near the tip clearance.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" 39","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139393494","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}

{"title":"Evaluation of Various Flow Control Methods in Reducing Drag and Aerodynamic Heating on the Nose of Hypersonic Flying Objects","authors":"†. S.Abbasi, S. E. Vali","doi":"10.47176/jafm.17.3.2150","DOIUrl":"https://doi.org/10.47176/jafm.17.3.2150","url":null,"abstract":"Effective deduction of air heating load and drag is a critical issue in hypersonic vehicle engineering applications. In this research, seven various geometrical models have been proposed to study and compare the effect of each configuration on the flow field, drag, and aerodynamic heating deduction under the same flow conditions. The presented configurations in this study: (a) blunt-body geometry as a reference of comparison, (b) blunt-body geometry with a spike, (c) blunt-body geometry with an counter flow jet, (d) blunt-body geometry with a spike and counter flow jet, (e) blunt-body geometry with a spike and aerodisk, (f) blunt-body geometry with a spike, aerodisk, and root counter flow jet, (g) blunt-body geometry with a spike, four aerodisks and root counter flow jet. The Reynolds-Averaged equations have been solved using the Finite Volume Method (FVM) along with the shear stress turbulence model (k-ω SST). The flow is assumed compressible, steady-state, and axisymmetric with a free stream Mach number of 6. According to the study of each configuration’s performance related to the parameters of drag, maximum pressure, and maximum heat flux factors on the blunt-body walls, (g) configuration with a drag factor of 0.2699, maximum pressure factor of 209.8, and maximum heat flux factor of 25.1, has the most deduction on the blunt-body walls among the seven configurations. The deduction percentage of drag, maximum pressure, and maximum heat flux factors of (g) configuration to (a) configuration are %72.1, %94.5, and %79.9, respectively, which significantly diminished drag and heat flux. Also, the best configuration scenarios for drag and aerodynamic heating deduction are geometrical models of g, f, d, e, c, b, and a, respectively.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"6 3","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139395727","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}

{"title":"Numerical Simulation of Crude Oil Leakage from Damaged Submarine-Buried Pipeline","authors":"H. J. Zhao, D. Zhang, †. X.F.Lv, L. L. Song, J. W. Li, F. Chen, X. Q. Xie","doi":"10.47176/jafm.17.1.2061","DOIUrl":"https://doi.org/10.47176/jafm.17.1.2061","url":null,"abstract":"Oil spill accidents in damaged submarine-buried pipelines cause tremendous economic losses and serious environmental pollution. The accurate prediction of oil spills from subsea pipelines is important for emergency response. In this study, the volume-of-fluid model, realizable k–ε turbulence model, and porous-medium model were employed to describe the process of an oil spill from a submarine pipeline to the sea surface. The effects of seawater density, seawater velocity, and pipeline buried depth on the transverse diffusion distance of crude oil and the time at which crude oil reaches the sea surface were obtained through numerical calculations. The calculation results show that, with a decrease in seawater density and an increase in seawater velocity and pipeline depth, the diffusion rate of crude oil decreases significantly, the maximum transverse diffusion distance increases and crude oil takes a long time to reach the sea surface. In particular, compared with a sea density of 1045 kg/m3, the transverse distance of a sea density of 1025 kg/m3 is increased by 0.091 m. When the seawater velocity is greater than 1.5 m/s, the diffusion of crude oil in seawater is significantly affected, the seawater velocity increases to 0.35 m/s, and the transverse diffusion distance of oil to the sea surface increases to 12.693 m. When the buried depth of the pipeline reaches 0.7 and 1.3 m compared to 0.1 m, the diffusion widths of crude oil in sea mud rise by 20% and 32.5%, respectively. The time required for crude oil to reach the sea surface and the transverse diffusion distance of crude oil migrating to the sea surface were analyzed using multiple regression, and the fitting formulas were obtained. The results provide theoretical support for accurately predicting the leakage range of submarine-buried pipelines and provide valuable guidance for submarine-buried pipeline leakage accident treatment schemes.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"135 43","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139128327","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}

{"title":"Hydrodynamic Performance of Cycloidal Propellers with Four-Bar and Mixed Four-bar/Five-bar Mechanisms: A Numerical Study","authors":"H. Yan, Z. Zhou, M. Lei, Z. Li, †. D.Xia","doi":"10.47176/jafm.17.3.2114","DOIUrl":"https://doi.org/10.47176/jafm.17.3.2114","url":null,"abstract":"Cycloidal propellers constitute a specialized category of underwater propulsion devices, widely employed in vehicles requiring exceptional maneuverability. The parameters of the blade-driving mechanism directly impact the propeller performance. Hence, the effect of variations in the geometric parameters of the blade-driving mechanism on the hydrodynamic performance of cycloidal propellers must be investigated. In this study, a specific set of four-bar and mixed four-bar/five-bar mechanisms are taken as examples, and the effect of linkage-length variations on the hydrodynamic performance of cycloidal propellers was analyzed using numerical simulation methods. First, we established a physical model of the cycloidal propeller, and then derived the relationship between blade-rotation and revolution angles. Subsequently, by solving the Navier–Stokes equations and employing computational fluid dynamics simulations based on viscosity, an analysis is conducted to reveal the trends in the impact of different linkage-length combinations on the hydrodynamic performance of the cycloidal propeller. Finally, the outcomes of the numerical simulations are interpreted using the wing element theory. In similar blade-driving mechanisms, the effects of varying linkage lengths on propeller hydrodynamic performance are determined through alterations in the blade rotation angle range and equilibrium position. An increase in the range of the blade-rotation angle significantly enhances the hydrodynamic performance of the cycloidal propeller. This research employs a more realistic auto-propulsion mode for numerical simulations, establishing a mapping relationship between the blade-driving mechanism and hydrodynamic performance of the cycloidal propeller, while analyzing the underlying influencing mechanisms. Furthermore, crucial numerical simulations and theoretical foundations are employed for designing the four-bar and mixed four-bar/five-bar mechanism cycloidal propellers. The findings of this study could also be used in similar cycloidal propellers with multilinkage mechanism.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"52 5","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139454779","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}

{"title":"Impact of Magnetic Fields and Fins on Entropy Generation, Thermal, and Hydrodynamic Performance in the Ferrofluids Flow within a Mini Channel","authors":"L. Boutas, M. Marzougui, J. Zinoubi, S. Gannouni","doi":"10.47176/jafm.17.3.2134","DOIUrl":"https://doi.org/10.47176/jafm.17.3.2134","url":null,"abstract":"The present work reports a CFD study of the magneto-convection of a ferrofluid (Fe3O4/water) circulating in a mini-channel under the influence of different vortex generators (fins and permanent magnets). The lower surface of the mini-channel is maintained at a constant temperature, while the upper surface is thermally insulated. The influence of fins, magnetic field intensity, and Reynolds number on the thermal and dynamic characteristics of the flow was numerically investigated using the finite volume method. The obtained results show that the coexistence of these two types of vortex generators considerably affects the flow structure; Entropy generation and heat transfer rate. Finally, the analysis of the different results shows that the concurrent presence of both the magnetic field and the fins results in a notably more efficient system. Using magnetic sources and fins simultaneously in a system with an intense magnetic field and a low Reynolds number can lead to a large gain in heat transfer.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"38 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139457827","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}

{"title":"Numerical Investigation of Oil–Air Flow Inside Tapered Roller Bearings with Oil Bath Lubrication","authors":"Z. Wang, F. Wang, H. Duan, W. Wang, R. Guo, Q. Yu","doi":"10.47176/jafm.17.1.1944","DOIUrl":"https://doi.org/10.47176/jafm.17.1.1944","url":null,"abstract":"Oil–air flow within an oil bath lubrication tapered roller bearing is essential for the lubrication and cooling of the bearing. In this paper, we develop a simulation model to investigate the flow field of tapered roller bearings with oil bath lubrication. The multiple reference frame (MRF) approach is used to describe the physical motion of the bearing, and the volume of fluid (VOF) two–phase flow model is used to track the oil–air interface in the flow field. The effects of mesh scale, geometric gap, and oil reservoir size on calculation time and convergence accuracy are examined in detail, and the effects of inner ring rotational speed and lubricant viscosity on frictional torque are systematically studied. The results of the numerical simulation indicate that as the gap distance between the raceway and the rolling elements decreases, the frictional torque is mainly generated by churning losses at the inner raceway and the rolling elements. The frictional torque increases with increasing inner ring speed and lubricating oil viscosity, with the rolling element contributing the largest portion at approximately 50% of the total. We demonstrate the effectiveness of a method to reduce frictional torque by optimizing the internal structure of the bearing to control oil flow. By optimizing the cage structure and reducing the roller half-cone angle, frictional torque can be reduced by 29.1% and 26.2%, respectively.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"20 10","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139126305","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}

{"title":"Suppressing the Vortex Rope Oscillation and Pressure Fluctuations by the Air Admission in Propeller Hydro-Turbine Draft Tube","authors":"H. Wu, F. Jin, Y. Luo, Y. Ge, Q. Wei, C. Zeng, X. Liu, W. Zhang, D. Miao, H. Bai","doi":"10.47176/jafm.17.1.1994","DOIUrl":"https://doi.org/10.47176/jafm.17.1.1994","url":null,"abstract":"For the purpose of automatic generation control (AGC), a portion of the propeller hydro-turbine units in China is adjusted to operate within a restricted range of 75%-85% load using computer-controlled AGC strategies. In engineering applications, it has been observed that when a propeller hydro-turbine unit operates under off-design conditions, a large-scale vortex rope would occur in the draft tube, leading to significant pressure fluctuations. Injecting air into the draft tube to reduce the amplitude of pressure fluctuations is a common practice, but its effectiveness has not been proven on propeller hydro-turbine units. In this study, a CFD model of a propeller hydro-turbine was established, and 15 cases with different guide vane openings (GVO, between 31° and 45°) under unsteady conditions were calculated and studied. Two air admission measures were introduced to suppress the vortex rope oscillation in the draft tube and to mitigate pressure fluctuations. The reason for the additional energy loss due to air admission was then explained by the entropy production theory, and its value was quantified. This study points out that when injecting air, it is necessary to first consider whether the air will obstruct the flow in the draft tube. Finally, based on simulation and experimental data under various load conditions, pressure fluctuation analysis (based on fast Fourier transform, FFT) was conducted to assess the effectiveness of air admission measures. This study can provide an additional option for balancing unit efficiency and stability when scheduling units using an AGC strategy.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"14 6","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139126338","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}

{"title":"Study of the Impact of LPG Composition on the Blowoff and Flashback Limits of a Premixed Flame in a Swirl Burner","authors":"A. S. Mahmood, F. A. Saleh","doi":"10.47176/jafm.17.3.2175","DOIUrl":"https://doi.org/10.47176/jafm.17.3.2175","url":null,"abstract":"Liquefied petroleum gas (LPG) is considered one of the gases widely used in many industrial and residential sectors. Still, due to its different compositions, mainly propane (C3H8) and butane (C4H10), it can have other combustion characteristics. This paper aims to conduct an experimental analysis to study the impact of LPG composition on the stability map (limits of blowoff and flashback) of the premixed flame in a tangential swirl burner. Four LPG mixtures were used with different proportions of ethane (C2H6), propane (C3H8), butane (C4H10), and pentane (C5H12). Three burner nozzles at diameters of 20, 25, and 30 mm have been used, which gave three swirl numbers of 0.918, 1.148, and 1.377, respectively. The results indicate that increasing the swirl number (S) from 0.918 to 1.377 for all LPG mixtures accelerated the flashback propensity (getting worse) while the blowoff resistance improved; thus, a rising S gave a better stability map. As for the effect of the LPG composition, it was found that the maximum flame temperature was for the LPG mixture containing high percentages of butane (C4H10), while the lowest was for the mixture containing fewer percentages of butane. Changing the LPG composition had an apparent effect on the flashback limits and a slight effect on the blowoff limits; it was found that mixtures containing high percentages of butane increased flame speeds and increased the flashback propensity. Compared to LPG mixtures, the flame stability map was widest for LPG mixtures containing lower percentages of butane. Therefore, LPG with propane (C3H8) proportions higher than butane (C4H10) reduces flame temperature, flame speeds, and flashback propensity, thus improving the stability map.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"19 23","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139457296","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}

{"title":"Analysis of Near-wall Coherent Structure of Spiral Flow in Circular Pipe Based on Large Eddy Simulation","authors":"Z. Wang, Y. Yin, S. Li, Y. Xu, L. Li, G. Li","doi":"10.47176/jafm.17.1.2038","DOIUrl":"https://doi.org/10.47176/jafm.17.1.2038","url":null,"abstract":"Based on the large eddy simulation method, this study performed the three-dimensional transient numerical analysis of the near-wall flow field of the spiral flow in a circular pipe and applied the sub-grid model of the kinetic energy transport. The low-speed bands, streamwise vortices and hairpin vortices of the spiral flow in the near-wall region of the circular pipe are determined using the Q criterion. The ejection and sweeping of coherent structures are identified using the velocity vector of the near-wall region; moreover, the two methods of creating the hairpin vortices are established by the image time series. The results demonstrate that the development directions of the near-wall bands, streamwise vortices and hairpin vortices of the spiral flow in the circular pipe develop along the path of the spiral line. The average spanwise period of the low-speed bands in the near-wall region is approximately 120 wall units, the length is more than 900 wall units and the height is not more than 40 wall units. The separation distance of the streamwise vortices is about 119 wall units. It has a certain angle with the wall (approximately 22°). The average burst period of a hairpin vortices is less than 0.015 s.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"49 14","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139126594","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}

{"title":"Structural Design and Performance Study of a Reciprocating Vortex Ring Generator","authors":"M. L. Zhou, †. D.Han, L. Zhu, S. Y. Yu, Y. F. Gao, Q. L. Shi, W. F. He","doi":"10.47176/jafm.17.1.1999","DOIUrl":"https://doi.org/10.47176/jafm.17.1.1999","url":null,"abstract":"Vortex rings can maintain their structure during motion and achieve long-distance transport with low energy consumption, which is a fluid transport method with great energy-saving potential. In this paper, a reciprocating vortex ring generator structure is designed, which can generate two vortex rings during the reciprocating motion of one piston, making full use of the thrust in the reciprocating motion period of the piston and improving the vortex ring generation frequency compared with traditional vortex ring generators. For the characteristics of long-distance transport of vortex rings, an experimental platform is designed and built, and 277 sets of experiments are carried out with different geometric parameters. The results show that the effect of generating two vortex rings could be achieved under other parameter conditions, except for some parameter conditions where the diameter ratio D1/D2 = 4. By analyzing the influence of baffle width ratio, length ratio, and diameter ratio on the moving distance of vortex rings, the performance of the vortex ring generator is preliminarily studied. In 277 sets of experiments, the maximum moving distance ratio x1 of vortex ring 1 is 13.7 when L1/L2 = 2.4, D1/D2 = 2, and w1 = 0.2. And the maximum moving distance ratio x2 of vortex ring 2 is 20 when L1/L2 = 2, D1/D2 = 2.5, and w2 = 0.2.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":"39 11","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139126965","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}