Pub Date : 2024-05-08DOI: 10.1134/s0015462824602110
A. N. Nuriev, O. N. Zaitseva, A. M. Kamalutdinov, E. E. Bogdanovich, A. R. Baimuratova
Abstract
Hydrodynamic flows induced by translational oscillations of cylindrical bodies of various cross-sectional shapes are studied. The motion of fluid around oscillating bodies is described using the system of Navier–Stokes equations written in a generalized curvilinear coordinate system. Transition to a given body shape is implemented using a conformal mapping. The problem is solved using the method of successive asymptotic expansions under the assumption that the oscillation amplitudes are small. In each asymptotic approximation, the subproblems are solved numerically using the finite-difference method. Based on the results of the work, estimates of the hydrodynamic effect are obtained, the applicability of the high-frequency asymptotic approximation is estimated, and secondary stationary flows near cylinders are studied, in particular, the occurrence of directed stationary flows near an oscillating asymmetric body is considered with reference to the Joukowski airfoil.
{"title":"Asymptotic Study of Flows Induced by Oscillations of Cylindrical Bodies","authors":"A. N. Nuriev, O. N. Zaitseva, A. M. Kamalutdinov, E. E. Bogdanovich, A. R. Baimuratova","doi":"10.1134/s0015462824602110","DOIUrl":"https://doi.org/10.1134/s0015462824602110","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Hydrodynamic flows induced by translational oscillations of cylindrical bodies of various cross-sectional shapes are studied. The motion of fluid around oscillating bodies is described using the system of Navier–Stokes equations written in a generalized curvilinear coordinate system. Transition to a given body shape is implemented using a conformal mapping. The problem is solved using the method of successive asymptotic expansions under the assumption that the oscillation amplitudes are small. In each asymptotic approximation, the subproblems are solved numerically using the finite-difference method. Based on the results of the work, estimates of the hydrodynamic effect are obtained, the applicability of the high-frequency asymptotic approximation is estimated, and secondary stationary flows near cylinders are studied, in particular, the occurrence of directed stationary flows near an oscillating asymmetric body is considered with reference to the Joukowski airfoil.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939894","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}
Pub Date : 2024-05-08DOI: 10.1134/s0015462824602122
I. V. Sturova
Abstract
The behavior of wave motion arising in an ideal incompressible homogeneous fluid under switching-on periodic bottom disturbances is studied in the linear approximation for the two-dimensional non-stationary problem. In the undisturbed state, the velocities of two-layer fluid flow are linear functions of the vertical coordinate in each of the layers with different gradients and coincide on the boundary of the layers. The upper boundary of fluid can be either free or bounded by the rigid cover. The dispersion dependences and the group velocities of the appearing wave modes are determined. The vertical displacements of the free surface and the interface between the layers are calculated. A comparison with the solution for a single-layer fluid is carried out.
{"title":"Development of the Wave Motion Induced by Near-Bottom Periodic Disturbances in a Two-Layer Shear Current","authors":"I. V. Sturova","doi":"10.1134/s0015462824602122","DOIUrl":"https://doi.org/10.1134/s0015462824602122","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The behavior of wave motion arising in an ideal incompressible homogeneous fluid under switching-on periodic bottom disturbances is studied in the linear approximation for the two-dimensional non-stationary problem. In the undisturbed state, the velocities of two-layer fluid flow are linear functions of the vertical coordinate in each of the layers with different gradients and coincide on the boundary of the layers. The upper boundary of fluid can be either free or bounded by the rigid cover. The dispersion dependences and the group velocities of the appearing wave modes are determined. The vertical displacements of the free surface and the interface between the layers are calculated. A comparison with the solution for a single-layer fluid is carried out.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939739","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}
Pub Date : 2024-05-08DOI: 10.1134/s0015462823603273
V. A. Il’in
Abstract
Electrothermal convection in a poorly conducting fluid in an alternating electric field of a horizontal capacitor is studied. The nonlinear regimes of electric convection in weightlessness are studies at low frequencies of the electric field on the basis of the pentamodal model within the framework of the electroconductive charge formation mechanism. Hysteresis transitions between two different synchronous and subharmonic regimes are found to exist. Transitions to chaos occur by means of either interemittance or a subharmonic cascade.
{"title":"Nonlinear Regimes of Electric Convection of Poorly Conducting Fluids in Weightlessness at Low Frequencies of an Electric Field","authors":"V. A. Il’in","doi":"10.1134/s0015462823603273","DOIUrl":"https://doi.org/10.1134/s0015462823603273","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Electrothermal convection in a poorly conducting fluid in an alternating electric field of a horizontal capacitor is studied. The nonlinear regimes of electric convection in weightlessness are studies at low frequencies of the electric field on the basis of the pentamodal model within the framework of the electroconductive charge formation mechanism. Hysteresis transitions between two different synchronous and subharmonic regimes are found to exist. Transitions to chaos occur by means of either interemittance or a subharmonic cascade.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939850","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}
Pub Date : 2024-05-08DOI: 10.1134/s0015462823603212
Yu. N. Grigor’ev, I. V. Ershov
Abstract
Comparative calculations of the location of the onset of the laminar-turbulent transition zone are performed using the eN-method for two points on the Mars “Pathfinder” entry trajectory. A three-component model of thermochemically nonequilibrium CO2–CO–O mixture is used in the calculations. The set of spatial disturbance frequencies is found using neutral curves for the first unstable modes of temporary disturbances. The transition Reynolds number ReδT is determined from the envelopes of families of N-factor curves at NT = 8. In the hypersonic regime at M = 12.6, taking into account the developed thermochemical nonequilibrium leads to a significant decrease in the static temperature of gas in the lower part of the boundary layer. As a result, the onset of the laminar-turbulent transition zone is displaced downstream by approximately 9% as compared to the case of a perfect gas.
摘要 对火星 "探路者 "进入轨迹上的两个点使用 eN 方法对层流-湍流过渡带的起始位置进行了比较计算。计算中使用了热化学非平衡 CO2-CO-O 混合物的三组分模型。利用临时扰动的第一种不稳定模式的中性曲线找到了一组空间扰动频率。过渡雷诺数 ReδT 是根据 NT = 8 时 N 因子曲线族的包络线确定的。 在 M = 12.6 时的高超声速状态下，考虑到已形成的热化学非平衡会导致边界层下部的气体静态温度显著下降。因此，与完美气体相比，层流-湍流过渡区的起始点向下游移动了约 9%。
{"title":"Estimate of the Onset of Laminar-Turbulent Transition on a Plate in Flight in the Mars Atmosphere","authors":"Yu. N. Grigor’ev, I. V. Ershov","doi":"10.1134/s0015462823603212","DOIUrl":"https://doi.org/10.1134/s0015462823603212","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Comparative calculations of the location of the onset of the laminar-turbulent transition zone are performed using the e<sup><i>N</i></sup>-method for two points on the Mars “Pathfinder” entry trajectory. A three-component model of thermochemically nonequilibrium CO<sub>2</sub>–CO–O mixture is used in the calculations. The set of spatial disturbance frequencies is found using neutral curves for the first unstable modes of temporary disturbances. The transition Reynolds number Re<sub>δ<i>T</i></sub> is determined from the envelopes of families of <i>N</i>-factor curves at <i>N</i><sub><i>T</i></sub> = 8. In the hypersonic regime at M = 12.6, taking into account the developed thermochemical nonequilibrium leads to a significant decrease in the static temperature of gas in the lower part of the boundary layer. As a result, the onset of the laminar-turbulent transition zone is displaced downstream by approximately 9% as compared to the case of a perfect gas.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939847","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}
Pub Date : 2024-05-08DOI: 10.1134/s0015462824600226
Yu. D. Chashechkin, A. Yu. Il’inykh, Sh. Kh. Khaiirbekov
Abstract
The evolution of the regular fine structure of the colored matter distribution produced, when a freely falling multifluid drop spreads in deep water, is for the first time traced using the techniques of engineering photo and video recording. The flow pattern is studied in the initial stage of the formation of a cavity and a crown during the coalescence of a compound drop, whose core is a drop of alizarin ink solution coated with an oil shell. The distributions of the colored fluid at the cavity bottom and the crown walls include streaky structures, whose formation can be due to the processes of the available potential surface energy (APSE) conversion occurring when the contact surfaces of the merging fluids are eliminated. In the experiments the height of the falling drop was varied. The core position in the compound drop was not checked but was determined by separation conditions. The ink core disintegration into fibers was observable in all the experiments. The areas of the cavity and crown surfaces covered by the colored fluid reached maximum at the central position of the core.
{"title":"The Initial Stage of the Coalescence of a Compound Drop in an Impact Regime","authors":"Yu. D. Chashechkin, A. Yu. Il’inykh, Sh. Kh. Khaiirbekov","doi":"10.1134/s0015462824600226","DOIUrl":"https://doi.org/10.1134/s0015462824600226","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The evolution of the regular fine structure of the colored matter distribution produced, when a freely falling multifluid drop spreads in deep water, is for the first time traced using the techniques of engineering photo and video recording. The flow pattern is studied in the initial stage of the formation of a cavity and a crown during the coalescence of a compound drop, whose core is a drop of alizarin ink solution coated with an oil shell. The distributions of the colored fluid at the cavity bottom and the crown walls include streaky structures, whose formation can be due to the processes of the available potential surface energy (APSE) conversion occurring when the contact surfaces of the merging fluids are eliminated. In the experiments the height of the falling drop was varied. The core position in the compound drop was not checked but was determined by separation conditions. The ink core disintegration into fibers was observable in all the experiments. The areas of the cavity and crown surfaces covered by the colored fluid reached maximum at the central position of the core.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939750","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}
Pub Date : 2024-05-08DOI: 10.1134/s0015462824602134
V. N. Kolodezhnov
Abstract
The first Stokes problem is considered for flows of non-Newtonian fluids with effective viscosity varying in accordance with the power law. Self-similar solutions are constructed for the fluids, whose mechanical behavior is described by the Ostwald–de Waele and Herschel–Bulkley rheological models with the corresponding restrictions on the nonlinearity degree exponent n. It is shown that for the Ostwald–de Waele fluid self-similar solutions exist only for 0 < n < 1, which corresponds to the pseudoplastic behavior. At the same time, self-similar solutions for the Herschel–Bulkley fluid can be obtained only at n > 1, when this fluid exhibits the properties of dilatancy.
摘要 针对有效粘度按幂律变化的非牛顿流体的流动，研究了第一斯托克斯问题。结果表明，Ostwald-de Waele 流体的自相似解仅存在于 0 < n < 1 时，即对应于假塑性行为。同时，Herschel-Bulkley 流体的自相似解只能在 n > 1 时获得，此时该流体表现出扩张特性。
{"title":"Self-Similar Solution of the First Stokes Problem for Non-Newtonian Fluids with Power-Law Viscosity","authors":"V. N. Kolodezhnov","doi":"10.1134/s0015462824602134","DOIUrl":"https://doi.org/10.1134/s0015462824602134","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The first Stokes problem is considered for flows of non-Newtonian fluids with effective viscosity varying in accordance with the power law. Self-similar solutions are constructed for the fluids, whose mechanical behavior is described by the Ostwald–de Waele and Herschel–Bulkley rheological models with the corresponding restrictions on the nonlinearity degree exponent <i>n</i>. It is shown that for the Ostwald–de Waele fluid self-similar solutions exist only for 0 <i>< n <</i> 1, which corresponds to the pseudoplastic behavior. At the same time, self-similar solutions for the Herschel–Bulkley fluid can be obtained only at <i>n ></i> 1, when this fluid exhibits the properties of dilatancy.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939849","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}
Pub Date : 2024-05-08DOI: 10.1134/s0015462824600202
A. V. Novikov, A. O. Obraz, D. A. Timokhin
Abstract
The results of the swept wing boundary layer stability investigation are presented for the case, when the wing surface has a region of gas suction through the wall normal to the surface, while the wing is in Mach number 2 flow. In the flow regime considered the predominant boundary layer instability type is the crossflow instability. The gas suction effect on the development of unstable modes in the boundary layer is investigated using the linear stability theory and direct numerical modeling. The numerical modeling of laminar (undisturbed) flow fields with regions of gas suction and disturbed flow fields is carried out by integrating Navier–Stokes equations. An analysis within the framework of the linear stability theory is performed using the ({{e}^{N}})-method. The suction region location is varied with conservation of the integral intensity. It is shown that the mode instability growth can be considerably suppressed at the expense of an optimal disposition of the suction region.
{"title":"Gas Suction Effect on the Crossflow Instability in Flow Past a Swept Wing","authors":"A. V. Novikov, A. O. Obraz, D. A. Timokhin","doi":"10.1134/s0015462824600202","DOIUrl":"https://doi.org/10.1134/s0015462824600202","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The results of the swept wing boundary layer stability investigation are presented for the case, when the wing surface has a region of gas suction through the wall normal to the surface, while the wing is in Mach number 2 flow. In the flow regime considered the predominant boundary layer instability type is the crossflow instability. The gas suction effect on the development of unstable modes in the boundary layer is investigated using the linear stability theory and direct numerical modeling. The numerical modeling of laminar (undisturbed) flow fields with regions of gas suction and disturbed flow fields is carried out by integrating Navier–Stokes equations. An analysis within the framework of the linear stability theory is performed using the <span>({{e}^{N}})</span>-method. The suction region location is varied with conservation of the integral intensity. It is shown that the mode instability growth can be considerably suppressed at the expense of an optimal disposition of the suction region.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939741","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}
Pub Date : 2024-05-08DOI: 10.1134/s001546282360325x
V. A. Ivanova, A. V. Maksimychev, P. L. Men’shikov, A. R. Pashutin, A. M. Perepukhov, A. N. Rozhkov, M. V. Tsar’kov
Abstract
A new method of determining the dimensions and shapes of polymer molecules in solutions is proposed and verified in experiments. The method is based on the measurements of the relaxation of the transverse magnetization intensity of nuclei. It is established that the decaying signal of the spin echo from elongated molecules contains two terms exponentially decaying with time, which correspond to two diffusion coefficients differing by a factor of about two. The signal from molecules with a near-spherical shape contain only one exponent.
{"title":"Determination of the Shape and Dimensions of the Polymer Molecules in Solutions Using Diffusional NMR Relaxation","authors":"V. A. Ivanova, A. V. Maksimychev, P. L. Men’shikov, A. R. Pashutin, A. M. Perepukhov, A. N. Rozhkov, M. V. Tsar’kov","doi":"10.1134/s001546282360325x","DOIUrl":"https://doi.org/10.1134/s001546282360325x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>A new method of determining the dimensions and shapes of polymer molecules in solutions is proposed and verified in experiments. The method is based on the measurements of the relaxation of the transverse magnetization intensity of nuclei. It is established that the decaying signal of the spin echo from elongated molecules contains two terms exponentially decaying with time, which correspond to two diffusion coefficients differing by a factor of about two. The signal from molecules with a near-spherical shape contain only one exponent.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939848","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}
Pub Date : 2024-05-08DOI: 10.1134/s0015462823603066
I. E. Melnikov, E. N. Pelinovsky
Abstract
The exact solutions to the system of equations of the linear theory of shallow water that represent travelling waves with some specific properties on the time propagation interval are discussed. These solutions are infinite when approaching the shore and finite when leaving for deep water. The solutions are obtained by reducing one-dimensional equations of shallow water to the Euler-Poisson-Darboux equation with negative integer coefficient ahead of the lower derivative. An analysis of the wave field dynamics is carried out. It is shown that the shape of a wave approaching the shore will be differentiated a certain number of times. This is illustrated by a number of examples. When the wave moves away from the shore, its profile is integrated. The solutions obtained within the framework of linear theory are valid only on a finite interval of variation in the depth.
{"title":"Linear Waves on Shallow Water Slowing Down near the Shore over Uneven Bottom","authors":"I. E. Melnikov, E. N. Pelinovsky","doi":"10.1134/s0015462823603066","DOIUrl":"https://doi.org/10.1134/s0015462823603066","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The exact solutions to the system of equations of the linear theory of shallow water that represent travelling waves with some specific properties on the time propagation interval are discussed. These solutions are infinite when approaching the shore and finite when leaving for deep water. The solutions are obtained by reducing one-dimensional equations of shallow water to the Euler-Poisson-Darboux equation with negative integer coefficient ahead of the lower derivative. An analysis of the wave field dynamics is carried out. It is shown that the shape of a wave approaching the shore will be differentiated a certain number of times. This is illustrated by a number of examples. When the wave moves away from the shore, its profile is integrated. The solutions obtained within the framework of linear theory are valid only on a finite interval of variation in the depth.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140940021","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}
Pub Date : 2024-05-08DOI: 10.1134/s0015462823602875
S. A. Isaev, O. O. Mil’man, A. A. Klyus, D. V. Nikushchenko, D. S. Khmara, L. P. Yunakov
Abstract
Rapid development of the anomalous enhancement of separated turbulent Re = 6000 air flow and heat transfer in an in-line single-row package of 31 inclined grooves, 0.2 in dimensionless depth, in a singled-out longitudinal region of the wall of a narrow channel is studied. It is due to the interference of vortex wakes behind the grooves and the acceleration in the channel flow core with the formation of a zone of ultrahigh longitudinal velocity. The wave-shaped parameter characteristics are stabilized in the region of approximately 15th groove, whereupon the oscillation amplitudes are moderately reduced. The return flows in the grooves are enhanced with distance from the entry section, the minimum negative friction diminishing from −2 to −4. The total relative heat removal from the structured region increases at q = const by a factor of approximately 2.75 and by the factor of two at T = const with increase in the relative hydraulic losses by the factor of 1.7, as compared with the case of a plane–parallel channel. The relative heat removal from the surface bounded by the contour of the 20th inclined groove amounts to 3.7 (q = const) with increase in the hydraulic losses by the factor of 2.2. An increase in the local maximum of the longitudinal velocity up to a factor of 1.5, as compared with the mean-mass velocity, can be observable.
{"title":"Anomalous Heat Transfer Enhancement in Separated Flow over a Zigzag-Shaped Dense Package of Inclined Grooves in a Channel Wall at Different Temperature Boundary Conditions","authors":"S. A. Isaev, O. O. Mil’man, A. A. Klyus, D. V. Nikushchenko, D. S. Khmara, L. P. Yunakov","doi":"10.1134/s0015462823602875","DOIUrl":"https://doi.org/10.1134/s0015462823602875","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Rapid development of the anomalous enhancement of separated turbulent Re = 6000 air flow and heat transfer in an in-line single-row package of 31 inclined grooves, 0.2 in dimensionless depth, in a singled-out longitudinal region of the wall of a narrow channel is studied. It is due to the interference of vortex wakes behind the grooves and the acceleration in the channel flow core with the formation of a zone of ultrahigh longitudinal velocity. The wave-shaped parameter characteristics are stabilized in the region of approximately 15th groove, whereupon the oscillation amplitudes are moderately reduced. The return flows in the grooves are enhanced with distance from the entry section, the minimum negative friction diminishing from −2 to −4. The total relative heat removal from the structured region increases at <i>q</i> = const by a factor of approximately 2.75 and by the factor of two at <i>T</i> = const with increase in the relative hydraulic losses by the factor of 1.7, as compared with the case of a plane–parallel channel. The relative heat removal from the surface bounded by the contour of the 20th inclined groove amounts to 3.7 (<i>q</i> = const) with increase in the hydraulic losses by the factor of 2.2. An increase in the local maximum of the longitudinal velocity up to a factor of 1.5, as compared with the mean-mass velocity, can be observable.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939876","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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