Boundary Layer Transient Hygroscopic Stresses in Orthotropic Thick Shells Under External Pressure

1994 ◽  
Vol 61 (1) ◽  
pp. 161-168 ◽  
Author(s):  
G. A. Kardomateas ◽  
C. B. Chung
Keyword(s):  
Boundary Layer ◽  
Orthotropic Cylindrical Shell ◽  
Moisture Diffusion ◽  
External Pressure ◽  
Axial Component ◽  
Epoxy Material ◽  
Transient Hygroscopic Stresses ◽  
Layer Region ◽  
Displacement Approach ◽  
Thick Shells

An exact elasticity solution is obtained for the stresses and displacements in an orthotropic cylindrical shell loaded by an external pressure under imposed constant moisture concentrations on the inner and outer surfaces. The material properties are assumed moisture independent and a displacement approach is used. Since the moisture diffusion process is relatively slow, the hygroscopic stresses are confined for practical time values to a boundary layer region near the surfaces. Illustrative results are presented for graphite-epoxy material regarding the boundary layer hygroscopic effect on the stress field with respect to time and the coupling of mechanical loading (external pressure) and moisture diffusion. For this material, it is shown that this effect is more pronounced for the axial component of stress.

scholarly journals The Profile Drag of Yawed Wings of Infinite Span

1951 ◽  
Vol 3 (3) ◽  
pp. 211-229 ◽  
Author(s):  
A.D. Young ◽  
T.B. Booth
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Drag Coefficient ◽  
Experimental Evidence ◽  
Flat Plate ◽  
Transition Point ◽  
Reynolds Numbers ◽  
External Pressure ◽  
Basic Assumptions ◽  
Angle Of Yaw

SummaryA method is developed for calculating the profile drag of a yawed wing of infinite span, based on the assumption that the form of the spanwise distribution of velocity in the boundary layer, whether laminar or turbulent, is insensitive to the chordwise pressure distribution. The form is assumed to be the same as that accepted for the boundary layer on an unyawed plate with zero external pressure gradient. Experimental evidence indicates that these assumptions are reasonable in this context. The method is applied to a flat plate and the N.A.C.A. 64-012 section at zero incidence for a range of Reynolds numbers between 106 and 108, angles of yaw up to 45°, and a range of transition point positions. It is shown that the drag coefficients of a flat plate varies with yaw as cos½ Λ (where Λ is the angle of yaw) if the boundary layer is completely laminar, and it varies as if the boundary layer is completely turbulent. The drag coefficient of the N.A.C.A. 64-012 section, however, varies closely as cos½ Λ for transition point positions between 0 and 0.5 c. Further calculations on wing sections of other shapes and thicknesses and more detailed experimental checks of the basic assumptions at higher Reynolds numbers are desirable.

scholarly journals Local Characteristics of the Nocturnal Boundary Layer in Response to External Pressure Forcing

2017 ◽  
Vol 56 (11) ◽  
pp. 3035-3047 ◽  
Author(s):  
Steven J. A. van der Linden ◽  
Peter Baas ◽  
J. Antoon van Hooft ◽  
Ivo G. S. van Hooijdonk ◽  
Fred C. Bosveld ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Stable Boundary Layer ◽  
Dynamical Behavior ◽  
Geostrophic Wind ◽  
External Pressure ◽  
Near Surface ◽  
Stable Boundary ◽  
Wind Speeds ◽  
Turbulent Characteristics

AbstractGeostrophic wind speed data, derived from pressure observations, are used in combination with tower measurements to investigate the nocturnal stable boundary layer at Cabauw, the Netherlands. Since the geostrophic wind speed is not directly influenced by local nocturnal stability, it may be regarded as an external forcing parameter of the nocturnal stable boundary layer. This is in contrast to local parameters such as in situ wind speed, the Monin–Obukhov stability parameter (z/L), or the local Richardson number. To characterize the stable boundary layer, ensemble averages of clear-sky nights with similar geostrophic wind speeds are formed. In this manner, the mean dynamical behavior of near-surface turbulent characteristics and composite profiles of wind and temperature are systematically investigated. The classification is found to result in a gradual ordering of the diagnosed variables in terms of the geostrophic wind speed. In an ensemble sense the transition from the weakly stable to very stable boundary layer is more gradual than expected. Interestingly, for very weak geostrophic winds, turbulent activity is found to be negligibly small while the resulting boundary cooling stays finite. Realistic numerical simulations for those cases should therefore have a comprehensive description of other thermodynamic processes such as soil heat conduction and radiative transfer.

Approximate Analytical Solutions for Marangoni Mixed Convection Boundary Layer

2010 ◽  
Author(s):  
Yan Zhang ◽  
Liancun Zheng ◽  
Jiemin Liu
Keyword(s):  
Boundary Layer ◽  
Mixed Convection ◽  
Analytical Solutions ◽  
External Pressure ◽  
Immiscible Fluids ◽  
Temperature Fields ◽  
Convection Boundary Layer ◽  
Coupling Condition ◽  
Approximate Analytical Solutions ◽  
Convection Boundary

The paper deals with a steady coupled dissipative layer, called Marangoni mixed convection boundary layer, which can be formed along the interface of two immiscible fluids, in surface driven flows. The mixed convection boundary layer is generated besides the Marangoni convection effects induced flow over the surface due to an imposed temperature gradient, there are also buoyancy effects due to gravity and external pressure gradient effects. We shall use a model proposed by Chamkha wherein the Marangoni coupling condition has been included into the boundary conditions at the interface. The similarity equations are first determined, and the approximate analytical solutions are obtained by an efficient transformation, asymptotic expansion and Pade´ approximant technique. The features of the flow and temperature fields as well as the interface velocity and heat transfer at the interface are discussed for some values of the governing parameters. The associated fluid mechanics was analyzed in detail.

The Effect of Magnetic Field on Compressible Boundary Layer by Homotopy Analysis Method

2021 ◽  
Vol 88 (1-2) ◽  
pp. 125
Author(s):  
R. Madhusudhan ◽  
Achala L. Nargund ◽  
S. B. Sathyanarayana
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Homotopy Analysis Method ◽  
Adverse Pressure Gradient ◽  
Analysis Method ◽  
Boundary Layer Region ◽  
Homotopy Analysis ◽  
Curve Singularities ◽  
Large Injection ◽  
Layer Region

We analyse the effect of applied magnetic field on the flow of compressible fluid with an adverse pressure gradient. The governing partial differential equations are solved analytically by Homotopy analysis method (HAM) and numerically by finite difference method. A detailed analysis is carried out for different values of the magnetic parameter, where suction/ injection is imposed at the wall. It is also observed that flow separation is seen in boundary layer region for large injection. HAM is a series solution which consists of a convergence parameter h which is estimated numerically by plotting <em>h</em> curve. Singularities of the solution are identified by Pade approximation.

Role of mixed nanofluids on fluid flow and intensify energy transfer in a boundary layer region driven by a free convective force

2019 ◽  
Vol 48 (8) ◽  
pp. 3986-3999 ◽  
Author(s):  
B. Ammani Kuttan ◽  
S. Manjunatha ◽  
S. Jayanthi ◽  
B. J. Gireesha
Keyword(s):  
Boundary Layer ◽  
Energy Transfer ◽  
Fluid Flow ◽  
Boundary Layer Region ◽  
Layer Region

Jet Impingement of a Non-Newtonian Fluid

2006 ◽  
Author(s):  
Jiangang Zhao ◽  
Roger E. Khayat
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Hydraulic Jump ◽  
Similarity Solutions ◽  
Surface Velocity ◽  
Free Surface Velocity ◽  
Viscous Boundary Layer ◽  
Boundary Layer Region ◽  
Layer Region ◽  
Viscous Boundary

The similarity solutions are presented for the wall flow which is formed when a smooth planar jet of power-law fluids impinges vertically on to a horizontal plate, and spreads out in a thin layer bounded by a hydraulic jump. This problem is formulated analogous to radial jet flow problem and the solution procedure is accounted for by means of similarity solution of the boundary-layer equation [1] for Newtonian fluids. For the convenience of analysis, the flow may be divided into three regions, namely a developing boundary-layer region, a fully viscous boundary-layer region, and a hydraulic jump region. The similarity solutions of the film thickness and free surface velocity in fully viscous boundary-layer region include unknown constant L, which is solved numerically and approximately in the developing boundary-layer flow region. Comparison between the numerical and approximate solutions leads generally to good agreement, except for severely shear-thinning fluids. The boundary-layer solution depends on two parameters: power-law index n and α, the dimensionless flow parameters. The effect of α on film thickness and free surface velocity is investigated. The relations between the position of the hydraulic jump and dimensionless flow parameter are obtained and the effect of α on the position of the jump is presented.

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