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Journal articles on the topic 'Boundary layer function'

Author: Grafiati

Published: 3 June 2025

Last updated: 31 July 2025

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1

Omuraliev, Asan, and Ella Abylaeva. "Regularized asymptotics of the solution of systems of parabolic differential equations." Filomat 36, no. 16 (2022): 5591–602. http://dx.doi.org/10.2298/fil2216591o.

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The regularization method for singularly perturbed problems of S. A. Lomov is generalized to constructing the asymptotics of the solution of the first boundary value problem for systems of differential equations of parabolic type with a small parameter at all derivatives.It is shown that the asymptotics of the solution of the problem contains n exponential, 2n parabolic and 2n angle boundary layer functions. The exponential boundary layer function describes the boundary layer along t = 0, the boundary layer along x = 0 and x = 1 is described by parabolic boundary layer functions.

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2

Omuraliev, Asan, and Ella Abylaeva. "Asymptotics of a parabolic problem with a nonsmooth angular function of the boundary layer." Ukrains’kyi Matematychnyi Zhurnal 77, no. 1 (2025): 75. https://doi.org/10.3842/umzh.v77i1.8152.

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UDC 517.9 We construct asymptotic approximations for solving a parabolic problem with nonsmooth angular function of the boundary layer in the case where the perturbation is singular. Unlike the works studied earlier, our algorithm is simple. By choosing a proper regularizing function, we managed to simplify the asymptotic structure of the solution and the construction algorithm. The obtained asymptotics contain only three boundary-layer functions. At the same time, the asymptotics of the solutions constructed earlier contain five boundary-layer components.

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3

Happyanto, Dedid Cahya, and Angga Wahyu Aditya. "Chattering reduction effect on power efficiency of IFOC based induction motor." JURNAL INFOTEL 14, no. 2 (2022): 154–60. http://dx.doi.org/10.20895/infotel.v14i2.753.

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Nowadays, the strategies to control Induction Motor (IM) is growing fast. The vector control strategies give better performance than the scalar control to control IM. IFOC is one of the vector control strategies which more realistic to apply in industry, military, and transportation. However, IFOC requires Sliding Mode Control (SMC) with the Lyapunov function to ensure robustness and stability. The first-order SMC or ordinary SMC uses boundary layers technique such as the saturation function and the tangent-hyperbolic function to overcome the chattering phenomenon. The performance of boundary

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4

Li, Hua, Mark W. Rutland, Masayoshi Watanabe, and Rob Atkin. "Boundary layer friction of solvate ionic liquids as a function of potential." Faraday Discussions 199 (2017): 311–22. http://dx.doi.org/10.1039/c6fd00236f.

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Atomic force microscopy (AFM) has been used to investigate the potential dependent boundary layer friction at solvate ionic liquid (SIL)–highly ordered pyrolytic graphite (HOPG) and SIL–Au(111) interfaces. Friction trace and retrace loops of lithium tetraglyme bis(trifluoromethylsulfonyl)amide (Li(G4) TFSI) at HOPG present clearer stick-slip events at negative potentials than at positive potentials, indicating that a Li<sup>+</sup> cation layer adsorbed to the HOPG lattice at negative potentials which enhances stick-slip events. The boundary layer friction data for Li(G4) TFSI shows that at HO

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5

Saxena, S. K., and R. C. Mehta. "Shock/turbulent boundary-layer interaction with wall function boundary conditions." AIAA Journal 24, no. 7 (1986): 1207–9. http://dx.doi.org/10.2514/3.9420.

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6

Du, Jianting, Rodolfo Bolaños, Xiaoli Guo Larsén, and Mark Kelly. "Wave boundary layer model in SWAN revisited." Ocean Science 15, no. 2 (2019): 361–77. http://dx.doi.org/10.5194/os-15-361-2019.

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Abstract. In this study, we extend the work presented in Du et al. (2017) to make the wave boundary layer model (WBLM) applicable for real cases by improving the wind-input and white-capping dissipation source functions. Improvement via the new source terms includes three aspects. First, the WBLM wind-input source function is developed by considering the impact of wave-induced wind profile variation on the estimation of wave growth rate. Second, the white-capping dissipation source function is revised to be not explicitly dependent on wind speed for real wave simulations. Third, several improv

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7

Rousset, Frédéric. "Inviscid boundary conditions and stability of viscous boundary layers." Asymptotic Analysis 26, no. 3-4 (2001): 285–306. https://doi.org/10.3233/asy-2001-451.

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We study the set of residual boundary conditions for a one‐dimensional hyperbolic system of conservation laws set in x>0 which appears when the diffusion coefficient of Dirichlet's problem for a parabolic perturbation tends to zero. We show that this set is a submanifold in a vicinity of a point where the Evans function of the associated profile of boundary layer is such that D(0)≠0. Next we linearize a multidimensional hyperbolic problem about a constant state in the set of residual conditions and a viscous approximation about the associated profile of boundary layer. We show that the Evan

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8

Algazin, O., and A. Kopaev. "Exact solutions of the Navier boundary value problem for a biharmonic equation with a special right-hand side in an infinite layer." Bulletin of State University of Education. Series: Physics and Mathematics, no. 3 (January 27, 2024): 6–14. https://doi.org/10.18384/2949-5067-2023-3-6-14.

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Aim. Purpose is to find exact solutions of the boundary value problem for the biharmonic equation in an infinite 𝑛𝑛-dimensional layer with Navier boundary conditions. Methodology. The paper considers a boundary value problem for a biharmonic equation in an infinite n-dimensional layer. The paper considers a boundary value problem for a biharmonic equation in an infinite n-dimensional layer 𝑥 ∈ Rn, 0 < y < a with Navier boundary conditions. This problem reduces to the sequential solution of two Dirichlet problems for the Poisson equation, the explicit solutions of which were obtained earl

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9

Saidi, A. R., S. R. Atashipour, and H. Keshavarzi. "Bending Analysis of Thick Laminated Rectangular Plates Using a Boundary Layer Function." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 10 (2010): 2073–81. http://dx.doi.org/10.1243/09544062jmes1849.

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In this article, the governing bending equations of thick laminated transversely isotropic rectangular plates are derived based on third-order shear deformation theory (TSDT). Using a new function, called the boundary layer function, the three coupled governing equations are converted to two decoupled equations. These equations are in terms of the deflection of the plate and the mentioned boundary layer function, which are written in invariant form. By solving the decoupled equations, a Levy-type analytical solution is presented for bending of a transversely isotropic plate. Finally, numerical

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10

Omuraliev, Asan, and Ella Abylaeva. "Singularly perturbed parabolic problem with oscillating initial condition." Filomat 33, no. 5 (2019): 1323–27. http://dx.doi.org/10.2298/fil1905323o.

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The aim of this paper is to construct regularized asymptotics of the solution of a singularly perturbed parabolic problem with an oscillating initial condition. The presence of a rapidly oscillating function in the initial condition has led to the appearance of a boundary layer function in the solution, which has the rapidly oscillating character of the change. In addition, it is shown that the asymptotics of the solution contains exponential, parabolic boundary layer functions and their products describing the angular boundary layers. Continuing the ideas of works [1, 3] a complete regularize

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11

Kubacki, Slawomir, Daniele Simoni, Davide Lengani, and Erik Dick. "An Extended Version of an Algebraic Intermittency Model for Prediction of Separation-Induced Transition at Elevated Free-Stream Turbulence Level." International Journal of Turbomachinery, Propulsion and Power 5, no. 4 (2020): 28. http://dx.doi.org/10.3390/ijtpp5040028.

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An algebraic intermittency model for boundary layer flow transition from laminar to turbulent state, is extended using an experimental data base on boundary layer flows with various transition types and results by large eddy simulation of transition in a separated boundary layer. The originating algebraic transition model functions well for bypass transition in an attached boundary layer under a moderately high or elevated free-stream turbulence level, and for transition by Kelvin–Helmholtz instability in a separated boundary layer under a low free-stream turbulence level. It also functions we

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12

Chalikov and Babanin. "Parameterization of Wave Boundary Layer." Atmosphere 10, no. 11 (2019): 686. http://dx.doi.org/10.3390/atmos10110686.

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It is known that drag coefficient varies in broad limits depending on wind velocity and wave age as well as on wave spectrum and some other parameters. All those effects produce large scatter of the drag coefficient, so, the data is plotted as a function of wind velocity forming a cloud of points with no distinct regularities. Such uncertainty can be overcome by the implementation of the WBL model instead of the calculations of drag with different formulas. The paper is devoted to the formulation of the Wave Boundary Layer (WBL) model for the parameterization of the ocean-atmosphere interactio

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13

Aditya, Angga Wahyu, Ihsan Ihsan, Fachri Husaini, and Faisal Faiiz Ramadhanu. "Rotor Speed Analysis of SMC-based IFOC for Low-Speed Induction Motor Control." ELKHA 15, no. 2 (2023): 106. http://dx.doi.org/10.26418/elkha.v15i2.67321.

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The control of electric motors, particularly three-phase induction motors, has developed rapidly due to their application in industry. Indirect Field Oriented Control (IFOC) is one of the most widely used control systems due to its ease of application. IFOC controls a three-phase induction motor in the same way as a DC motor. However, IFOC requires a Sliding Mode Control (SMC) controller with Lyapunov stability theory to ensure robustness and stability. In exceptional conditions, such as low-speed settings, the SMC-based IFOC requires unique sets to operate with a steady-state error (Ess) at a

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14

Sun, Lei, Xihuan Sun, Yongye Li, and Cheng Wang. "Experimental Study on Flow Structure Characteristics of Gap Flow Boundary Layer Based on PIV." Water 15, no. 22 (2023): 3989. http://dx.doi.org/10.3390/w15223989.

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The boundary layer is the main source of frictional resistance in gap flow, and the study of the flow structure characteristics of the gap flow boundary layer is of great significance for the study of gap flow theory. In this study, the PIV technique was utilized to experimentally investigate the gap flow boundary layers with Reynolds numbers of 16,587–56,870 and gap ratios of 0.6–0.8. The characteristics of the wall friction velocity, the boundary layer thickness, and the wall function of the gap flow boundary layer were analyzed, and the influences of the mean velocity of the gap flow and th

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15

Elipot, S., and S. T. Gille. "Ekman layers in the Southern Ocean: spectral models and observations, vertical viscosity and boundary layer depth." Ocean Science 5, no. 2 (2009): 115–39. http://dx.doi.org/10.5194/os-5-115-2009.

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Abstract. Spectral characteristics of the oceanic boundary-layer response to wind stress forcing are assessed by comparing surface drifter observations from the Southern Ocean to a suite of idealized models that parameterize the vertical flux of horizontal momentum using a first-order turbulence closure scheme. The models vary in their representation of vertical viscosity and boundary conditions. Each is used to derive a theoretical transfer function for the spectral linear response of the ocean to wind stress. The transfer functions are evaluated using observational data. The ageostrophic com

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Elipot, S., and S. T. Gille. "Ekman layers in the Southern Ocean: spectral models and observations, vertical viscosity and boundary layer depth." Ocean Science Discussions 6, no. 1 (2009): 277–341. http://dx.doi.org/10.5194/osd-6-277-2009.

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Abstract. Spectral characteristics of the oceanic boundary-layer response to wind stress forcing are assessed by comparing surface drifter observations from the Southern Ocean to a suite of idealized models that parameterize the vertical flux of horizontal momentum using a first-order turbulence closure scheme. The models vary in their representation of vertical viscosity and boundary conditions. Each is used to derive a theoretical transfer function for the spectral linear response of the ocean to wind stress. The transfer functions are evaluated using observational data. The ageostrophic com

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17

Mahir, M. Sabzaliev, and M. Sabzalieva Ilhama. "Asymptotics of Solution of a Boundary Value Problem for Quasilinear Non-Classical Type Differential Equation of Arbitrary Odd Order." British Journal of Mathematics & Computer Science 22, no. 4 (2017): 1–19. https://doi.org/10.9734/BJMCS/2017/33704.

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In a rectangle domain, a boundary value problem is considered for a singularly perturbed quasilinear non-classical type equation of arbitrary odd order, degenerating into a hyperbolic equation. Asymptotic expansion of the generalized solution of the problem under consideration is constructed to within any positive degree of a small parameter, and the residual term is estimated.

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18

Savic, Slobodan, and Branko Obrovic. "The influence of variation of electroconductivity on ionized gas flow in the boundary layer along a porous wall." Theoretical and Applied Mechanics 33, no. 2 (2006): 149–79. http://dx.doi.org/10.2298/tam0602149s.

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This paper investigates ionized gas flow in the boundary layer when its electroconductivity is varied. The flow is planar and the contour is porous. At first, it is assumed that the ionized gas electroconductivity ? depends only on the longitudinal variable. Then we adopt that it is a function of the ratio of the longitudinal velocity and the velocity at the outer edge of the boundary layer. For both electroconductivity variation laws, by application of the general similarity method, the governing boundary layer equations are brought to a generalized form and numerically solved in a four-param

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19

Pedlosky, Joseph. "The Coastal Bottom Boundary Layer: A Note on the Model of Chapman and Lentz." Journal of Physical Oceanography 37, no. 11 (2007): 2776–84. http://dx.doi.org/10.1175/2007jpo3710.1.

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Abstract The bottom boundary layer of a stratified flow on a coastal continental shelf is examined using the model of Chapman and Lentz. The flow is driven by a surface stress, uniform in the alongshore coordinate, in a downwelling-favorable direction. The stress diminishes in the offshore direction and produces an Ekman pumping, as well as an onshore Ekman flux. The model yields an interior flow, sandwiched between an upper Ekman layer and a bottom boundary layer. The interior has a horizontal density gradient produced by a balance between horizontal diffusion of density and vertical advectio

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20

Chen, Dong Ni, Hui Qi, and Yong Shi. "The Effect on Scattering of SH-Wave in a Layered Half-Space with the Subsurface Circular Cavities." Advanced Materials Research 194-196 (February 2011): 1908–11. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.1908.

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The scattering of SH-wave caused by the subsurface circular cavities in an elastic half-space covered with an elastic layer was discussed, which was based on the complex function method and wave functions expansion method. The solution of scattering of SH-wave was given by using circular boundary of large radius to approximate straight boundary of surface elastic layer. According to boundary conditions, we needed to solve the infinite linear algebraic equations with unknown coefficients in wave functions. Finally, the dynamic stress concentration factors around circular cavities were discussed

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21

Dou, Hua-Shu, Wenqian Xu, and Boo Cheong Khoo. "Stability of boundary layer flow based on energy gradient theory." Modern Physics Letters B 32, no. 12n13 (2018): 1840003. http://dx.doi.org/10.1142/s0217984918400031.

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The flow of the laminar boundary layer on a flat plate is studied with the simulation of Navier–Stokes equations. The mechanisms of flow instability at external edge of the boundary layer and near the wall are analyzed using the energy gradient theory. The simulation results show that there is an overshoot on the velocity profile at the external edge of the boundary layer. At this overshoot, the energy gradient function is very large which results in instability according to the energy gradient theory. It is found that the transverse gradient of the total mechanical energy is responsible for t

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22

Cai, Xin. "Effective Approximation for Elliptic Partial Differential Equation with Periodical Boundary Value Problem." Applied Mechanics and Materials 29-32 (August 2010): 1294–300. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1294.

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Elliptic partial differential equation with periodical boundary value problem was considered. The equation would degenerate to parabolic partial differential equation when small parameter tends to zero. This is a multi-scale problem. Firstly, the property of boundary layer was discussed. Secondly, the boundary layer function was presented. The smooth component was constructed according to the boundary layer function. Thirdly, finite difference scheme for the smooth component is proposed according to transition point in time direction. Finally, experiment was proposed to illustrate that our pre

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23

Ivanovic, Decan, and Vladan Ivanovic. "On injection-ejection fluid influence through different accelerating porous surfaces on unsteady 2d incompressible boundary layer characteristics." Theoretical and Applied Mechanics 32, no. 2 (2005): 131–46. http://dx.doi.org/10.2298/tam0502131i.

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Through the porous contour in perpendicular direction, the fluid of the same properties as incompressible fluid in basic flow, has been injected or ejected with velocity who is a function of the contour longitudinal coordinate and time. The corresponding equations of unsteady boundary layer, by introducing the appropriate variable transformations, momentum and energy equations and two similarity parameters sets, are transformed into generalized form. These parameters are expressing the influence of the outer flow velocity, the injection or ejection velocity and the flow history in boundary lay

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24

Chen, Dong Ni, Hui Qi, and Yong Shi. "The Scattering of SH-Wave Caused by Subsurface Circular Cavities in a Layered Half-Space." Key Engineering Materials 488-489 (September 2011): 226–29. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.226.

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The scattering of SH-wave caused by the subsurface circular cavities in an elastic half-space covered with an elastic layer was discussed, which was based on the complex function method ,wave functions expansion method and big circular arc postulation method in which the circular boundary of large radius was used to approximate straight boundary of surface elastic layer. By the theory of Helmholtz, the general solution of the Biot’s wave function was achieved. Utilizing the complex series expansion technology and the boundary conditions, we could transform the present problem into the problem

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King, Simon, and Andrew Curtis. "Velocity analysis using both reflections and refractions in seismic interferometry." GEOPHYSICS 76, no. 5 (2011): SA83—SA96. http://dx.doi.org/10.1190/geo2011-0008.1.

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The Green’s function between two receiver locations can be estimated by crosscorrelating and summing the recorded Green’s functions from sources on a boundary that surrounds the receiver pair. We demonstrate that when two receivers are positioned far from the source boundary in a marine-type acquisition geometry, the crosscorrelations (the Green’s functions before summation over the source boundary) are dominated by reflected energy which can be used in a semblance analysis to determine the seismic velocity and thickness of the first layer. When these crosscorrelations are summed over the boun

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26

Cai, Xin. "Asymptotic Analysis for Hyperbolic Equation with Neumann Condition." Applied Mechanics and Materials 29-32 (August 2010): 1287–93. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1287.

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The second-order hyperbolic equation with small parameter and Neumann con- dition is considered. This kind of problem loses the boundary conditions both in x = 0 and x = 1, while it also loses two initial boundary conditions in t = 0. The solution changes rapidly near two boundary layers and one initial layer. Firstly, the asymptotic solution was studied. The analytical solution was approximated by the degenerate solution and two boundary layer functions and one initial layer function. Secondly, three transition points were presented ac- cording to Shishkin’s idea. Non-equidistant mesh partiti

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27

Volino, Ralph J., and Terrence W. Simon. "Spectral Measurements in Transitional Boundary Layers on a Concave Wall Under High and Low Free-Stream Turbulence Conditions." Journal of Turbomachinery 122, no. 3 (1997): 450–57. http://dx.doi.org/10.1115/1.1303075.

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The relationship between free-stream turbulence and boundary layer behavior has been investigated using spectral measurements. The power spectral densities of turbulence quantities in transitional and fully turbulent boundary layers were computed and compared to the power spectra of the same quantities measured in the free stream. Comparisons were made using the “transfer function.” The transfer function is the ratio of two spectra at each frequency in the spectra. Comparisons were done in flows with low (0.6 percent) and high (8 percent) free-stream turbulence intensities. Evidence was gather

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28

Meleshko, Sergey V., and Vladislav V. Pukhnachev. "Group Analysis of the Boundary Layer Equations in the Models of Polymer Solutions." Symmetry 12, no. 7 (2020): 1084. http://dx.doi.org/10.3390/sym12071084.

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The famous Toms effect (1948) consists of a substantial increase of the critical Reynolds number when a small amount of soluble polymer is introduced into water. The most noticeable influence of polymer additives is manifested in the boundary layer near solid surfaces. The task includes the ratio of two characteristic length scales, one of which is the Prandtl scale, and the other is defined as the square root of the normalized coefficient of relaxation viscosity (Frolovskaya and Pukhnachev, 2018) and does not depend on the characteristics of the motion. In the limit case, when the ratio of th

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29

Pratama, Muchamad Harry Yudha, and Agus Yodi Gunawan. "EXPLORING PHYSICS-INFORMED NEURAL NETWORKS FOR SOLVING BOUNDARY LAYER PROBLEMS." Journal of Fundamental Mathematics and Applications (JFMA) 6, no. 2 (2023): 101–16. http://dx.doi.org/10.14710/jfma.v6i2.20084.

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In this paper, we explore a cutting-edge technique called as Physics- Informed Neural Networks (PINN) to tackle boundary layer problems. We here examine four different cases of boundary layers of second-order ODE: a linear ODEwith constant coefficients, a nonlinear ODE with homogeneous boundary conditions, an ODE with non-constant coefficients, and an ODE featuring multiple boundary layers. We adapt the line of PINN technique for handling those problems, and our results show that the accuracy of the resulted solutions depends on how we choose the most reliable and robust activation functions w

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30

McMahon, Charles W., Joseph J. Kuehl, and Vitalii A. Sheremet. "A Viscous, Two-Layer Western Boundary Current Structure Function." Fluids 5, no. 2 (2020): 63. http://dx.doi.org/10.3390/fluids5020063.

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The classic oceanographic problem of a 1.5-layer western boundary current evolving along a straight wall is considered. Here, building upon the previous work of Charney, Huang and Kamenkovich, we have derived, solved and validated a new numerical formulation for accounting for viscous effects in such systems. The numerical formulation is validated against rotating table experimental results.

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31

El‐Hawary, H. M. "A deficient spline function approximation for boundary layer flow." International Journal of Numerical Methods for Heat & Fluid Flow 11, no. 3 (2001): 227–36. http://dx.doi.org/10.1108/09615530110385111.

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Zadorin, A. I. "FORMULAS FOR NUMERICAL DIFFERENTIATION ON A UNIFORM GRID IN THE PRESENCE OF A BOUNDARY LAYER." Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki 64, no. 6 (2024): 922–31. https://doi.org/10.31857/s0044466924060039.

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The problem of numerical differentiation of functions with large gradients is considered. It is assumed that for the original function of one variable the decomposition is valid as the sum of a regular component with bounded derivatives up to a certain order and a boundary layer component having large gradients and known with an accuracy of up to a factor. Such a decomposition, in particular, is valid for solution of a singularly perturbed boundary value problem. The topic of the study is relevant, since the application of classical polynomial formulas of numerical differentiation to functions

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Calvert, Velinda, and Mohsen Razzaghi. "Solutions of the Blasius and MHD Falkner-Skan boundary-layer equations by modified rational Bernoulli functions." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 8 (2017): 1687–705. http://dx.doi.org/10.1108/hff-05-2016-0190.

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Purpose This paper aims to propose a new numerical method for the solution of the Blasius and magnetohydrodynamic (MHD) Falkner-Skan boundary-layer equations. The Blasius and MHD Falkner-Skan equations are third-order nonlinear boundary value problems on the semi-infinite domain. Design/methodology/approach The approach is based upon modified rational Bernoulli functions. The operational matrices of derivative and product of modified rational Bernoulli functions are presented. These matrices together with the collocation method are then utilized to reduce the solution of the Blasius and MHD Fa

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Singer, B. A. "Turbulent Wall-Pressure Fluctuations: A New Model for Off-Axis Cross-Spectral Density." Journal of Fluids Engineering 119, no. 2 (1997): 277–80. http://dx.doi.org/10.1115/1.2819131.

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Models for the distribution of the wall-pressure under a turbulent boundary layer often estimate the coherence of the cross-spectral density in terms of a product of two coherence functions. One such function describes the coherence as a function of separation distance in the mean-flow direction, the other function describes the coherence in the cross-stream direction. Analysis of data from a large-eddy simulation of a turbulent boundary layer reveals that this approximation dramatically underpredicts the coherence for separation directions that are neither aligned with nor perpendicular to th

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Mathews, James R., Vianney Masson, Stéphane Moreau, and Hélène Posson. "The modified Myers boundary condition for swirling flow." Journal of Fluid Mechanics 847 (May 29, 2018): 868–906. http://dx.doi.org/10.1017/jfm.2018.326.

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This paper gives a modified Myers boundary condition in swirling inviscid flow, which differs from the standard Myers boundary condition by assuming a small but non-zero boundary layer thickness. The new boundary condition is derived and is shown to have the correct quadratic error behaviour with boundary layer thickness and also to agree with previous results when the swirl is set to zero. The boundary condition is initially derived for swirling flow with constant azimuthal velocity, but easily extends to radially varying swirling flow, with terms depending on the boundary layer model. The mo

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36

Subramanian, Chelakara S., Nagahiko Shinjo, and Sathya N. Gangadharan. "A Study of Hydrodynamic Characteristics of Boundary Layer With Algae Roughness." Marine Technology and SNAME News 41, no. 02 (2004): 60–66. http://dx.doi.org/10.5957/mt1.2004.41.2.60.

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Filamentous algae fouling, such as Enteromorpha clathrata, is a soft and hairylike roughness that sometimes grows even thicker than a normal boundary layer. Typically, such fouling has been treated as traditional roughness functions to yield hydrodynamic characteristics. This technique has been successfully used for a thin fouling layer. However, it may not be applicable on a thicker layer, as the present study found substantial fluid flow within the layer. For such cases, the roughness cannot be treated simply as a passive geometric variable, but its kinematics and interactions with the flow

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Wright, M. C. M., and P. A. Nelson. "Fast boundary layer suction optimization with neural networks." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 214, no. 2 (2000): 107–13. http://dx.doi.org/10.1243/0954410001531854.

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Previous experiments on a flat plate with four suction panels in a wind tunnel have shown that it is possible to optimize the distribution of suction so as to minimize the suction energy required to maintain laminar-turbulent transition at a fixed position. The location of the transition can be detected by surface-mounted microphones. This can form the basis of a ‘smart suction’ system which can adaptively minimize energy consumption in flight. The gradient descent optimization scheme previously employed finite difference estimates of the gradient of transition position as a function of the su

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Vindel, J. M., C. Yagüe, and J. M. Redondo. "Structure function analysis and intermittency in the atmospheric boundary layer." Nonlinear Processes in Geophysics 15, no. 6 (2008): 915–29. http://dx.doi.org/10.5194/npg-15-915-2008.

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Abstract. Data from the SABLES98 experimental campaign (Cuxart et al., 2000) have been used in order to study the relationship of the probability distribution of velocity increments (PDFs) to the scale and the degree of stability. This connection is demonstrated by means of the velocity structure functions and the PDFs of the velocity increments. Using the hypothesis of local similarity, so that the third order structure function scaling exponent is one, the inertial range in the Kolmogorov sense has been identified for different conditions, obtaining the velocity structure function scaling ex

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Grubin, S. E., and V. N. Trigub. "The long-wave limit in the asymptotic theory of hypersonic boundary-layer stability." Journal of Fluid Mechanics 246 (January 1993): 381–95. http://dx.doi.org/10.1017/s0022112093000187.

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This paper discusses the long-wave limit of the asymptotic theory of hypersonic boundary-layer stability for a gas with the Prandtl number ½ < σ < 1 and with the viscosity–temperature law being a power function. The investigation is confined to the local-parallel approximation.In the long-wave limit the vorticity mode starts to interact with the acoustic disturbances in the boundary-layer region. The general solution of the linear problem in the boundary-layer inner region is analysed numerically and analytically. This solution is matched with the long-wave vorticity-mode solution near t

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Brambley, E. J., M. Darau, and S. W. Rienstra. "The critical layer in linear-shear boundary layers over acoustic linings." Journal of Fluid Mechanics 710 (August 31, 2012): 545–68. http://dx.doi.org/10.1017/jfm.2012.376.

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AbstractAcoustics within mean flows are governed by the linearized Euler equations, which possess a singularity wherever the local mean flow velocity is equal to the phase speed of the disturbance. Such locations are termed critical layers, and are usually ignored when estimating the sound field, with their contribution assumed to be negligible. This paper studies fully both numerically and analytically a simple yet typical sheared ducted flow in order to investigate the influence of the critical layer, and shows that the neglect of critical layers is sometimes, but certainly not always, justi

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Teng, Yunfei, Lin Lu, Liang Cheng, Feifei Tong, and Guoqiang Tang. "DEFECT FUNCTION MODELS FOR THE WAVE BOUNDARY LAYERS." Coastal Engineering Proceedings, no. 36v (December 28, 2020): 2. http://dx.doi.org/10.9753/icce.v36v.waves.2.

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The boundary layer flow induced by surface waves has been extensively investigated due to its significance in engineering applications such as sediment transport and hydrodynamic forces on subsea structures. Several forms of defect functions (referred to as DF hereafter) were developed in the past decades, e.g. Sleath (1970, 1982), Nielsen (1985, 2016) and etc., due to their good efficiency in the description of the velocity distribution in one dimensional wave boundary layer (WBL). In this work, two forms of DFs are proposed: (i) DF-I describes the velocity distributions and bottom shear stre

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Schobeiri, M. T., and L. Wright. "Advances in Unsteady Boundary Layer Transition Research, Part I: Theory and Modeling." International Journal of Rotating Machinery 9, no. 1 (2003): 1–9. http://dx.doi.org/10.1155/s1023621x03000010.

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This two-part article presents recent advances in boundary layer research that deal with the unsteady boundary layer transition modeling and its validation. A new unsteady boundary layer transition model was developed based on a universal unsteady intermittency function. It accounts for the effects of periodic unsteady wake flow on the boundary layer transition. To establish the transition model, an inductive approach was implemented; the approach was based on the results of comprehensive experimental and theoretical studies of unsteady wake flow and unsteady boundary layer flow. The experimen

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Hayat, T., Z. Iqbal, M. Qasim, and A. Alsaedi. "Flow of an Eyring-Powell Fluid with Convective Boundary Conditions." Journal of Mechanics 29, no. 2 (2012): 217–24. http://dx.doi.org/10.1017/jmech.2012.135.

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AbstractThe boundary layer flow of an Eyring-Powell fluid over a stretching surface subject to the convective boundary condition is investigated. Nonlinear problem is computed and a comparative study is presented with the existing results in viscous fluid. The constructed differential systems have been solved for homotopic solutions. Convergence of series solutions has been discussed. Special emphasis has been given to the effects of material parameters of fluid (ε), (δ), Biot number (γ) and Prandtl number (Pr) on the velocity and temperature profiles. Tabulated values of Nusselt number and sk

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Lei, Da, Hui Yang, Yun Zheng, Qingzhe Gao, and Xiubo Jin. "A Modified Shielding and Rapid Transition DDES Model for Separated Flows." Entropy 25, no. 4 (2023): 613. http://dx.doi.org/10.3390/e25040613.

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In this paper, the major problems associated with detached eddy simulation (DES) (namely, modeled stress depletion (MSD) and slowing of the RANS to LES transition (RLT)) are discussed and reviewed, and relevant improvements are developed. A modified version for the delayed DES (DDES) method with adaptive modified adequate shielding and rapid transition is proposed; this is called MSRT DDES. The modified shielding strategy can be adjusted adaptively according to the local flow conditions: keeping the RANS behavior in the whole boundary layer when there is no resolved turbulence, and weakening t

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Chernukha, Olha, Petro Pukach, Halyna Bilushchak, Yurii Bilushchak, and Myroslava Vovk. "Advanced Statistical Approach for the Mathematical Modeling of Transfer Processes in a Layer Based on Experimental Data at the Boundary." Symmetry 16, no. 7 (2024): 802. http://dx.doi.org/10.3390/sym16070802.

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In this work, a mathematical model of the transfer process in a layer under the condition of given experimental data on a part of the layer boundary is presented and investigated. Such research is important for the mathematical description of the objects and systems for which, based on physical considerations, it is impossible to correctly impose boundary or initial conditions, even in a sufficiently general form, but there are experimental data on the desired function or its derivative at the boundary of the body or at the initial time. The values of the desired function at the boundary are k

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Fan, Dongyue, and Xueyun Lin. "Gevrey well-posedness of the 2D micropolar boundary layer equations without structural assumption." EPJ Web of Conferences 332 (2025): 01005. https://doi.org/10.1051/epjconf/202533201005.

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In this paper, we are aimed to obtain the well-posedness theory for the 2D micropolar boundary layer system in Gevrey function space with Gevrey index σ ε (1, 3/2 ] in the absence of the structural assumption. This paper first introduces the Gevrey function space. Then it obtains the a priori estimate. It is worth mentioning that we introduce an auxiliary function u which is of great importance to overcome the loss of tangential derivatives in the system. We discover that the 2D micropolar boundary layer system is well-posed in Gevrey function space.

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Siddheshwar, P. G., U. S. Mahabaleswar, and H. I. Andersson. "A New Analytical Procedure for Solving the Non-Linear Differential Equation Arising in the Stretching Sheet Problem." International Journal of Applied Mechanics and Engineering 18, no. 3 (2013): 955–64. http://dx.doi.org/10.2478/ijame-2013-0059.

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Abstract The paper discusses a new analytical procedure for solving the non-linear boundary layer equation arising in a linear stretching sheet problem involving a Newtonian/non-Newtonian liquid. On using a technique akin to perturbation the problem gives rise to a system of non-linear governing differential equations that are solved exactly. An analytical expression is obtained for the stream function and velocity as a function of the stretching parameters. The Clairaut equation is obtained on consideration of consistency and its solution is shown to be that of the stretching sheet boundary l

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Savic, Slobodan, Branko Obrovic, Dusan Gordic, and Sasa Jovanovic. "Investigation of the ionized gas flow adjacent to porous wall in the case when electroconductivity is a function of the longitudinal velocity gradient." Thermal Science 14, no. 1 (2010): 89–102. http://dx.doi.org/10.2298/tsci1001089s.

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This paper studies the laminar boundary layer on a body of an arbitrary shape when the ionized gas flow is planar and steady and the wall of the body within the fluid porous. The outer magnetic field is perpendicular to the fluid flow. The inner magnetic and outer electric fields are neglected. The ionized gas electroconductivity is assumed to be a function of the longitudinal velocity gradient. Using transformations, the governing boundary layer equations are brought to a general mathematical model. Based on the obtained numerical solutions in the tabular forms, the behavior of important non-

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KANG, Juan, and Yao CHENG. "Numerical Integration of the Function with Twin Boundary Layers." Wuhan University Journal of Natural Sciences 30, no. 2 (2025): 139–49. https://doi.org/10.1051/wujns/2025302139.

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Traditional numerical integration requires sufficient smoothness of the integrand to achieve high-order algebraic accuracy. If the function has a boundary layer with large gradient, the composite integration formula on the uniform mesh will produce very large integration errors. In this paper, we study the Newton-Cotes formula based on Lagrange interpolation functions, local [see formula in PDF] projection approximating the integrand, and Gauss integration. On the Shishkin mesh, we establish an optimal-order integration error estimate uniformly in the perturbation parameter. The convergence ra

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WANG, FUYONG, ZHICHAO LIU, LIANG JIAO, CONGLE WANG, and HU GUO. "A FRACTAL PERMEABILITY MODEL COUPLING BOUNDARY-LAYER EFFECT FOR TIGHT OIL RESERVOIRS." Fractals 25, no. 05 (2017): 1750042. http://dx.doi.org/10.1142/s0218348x17500426.

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A fractal permeability model coupling non-flowing boundary-layer effect for tight oil reservoirs was proposed. Firstly, pore structures of tight formations were characterized with fractal theory. Then, with the empirical equation of boundary-layer thickness, Hagen–Poiseuille equation and fractal theory, a fractal torturous capillary tube model coupled with boundary-layer effect was developed, and verified with experimental data. Finally, the parameters influencing effective liquid permeability were quantitatively investigated. The research results show that effective liquid permeability of tig

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