Certain types of vibrationally convective instability of a two-dimensional fluid layer in zero gravity

1988 ◽  
Vol 22 (5) ◽  
pp. 657-660 ◽  
Author(s):  
L. M. Braverman
Keyword(s):  
Convective Instability ◽  
Fluid Layer ◽  
Zero Gravity ◽  
Two Dimensional

scholarly journals Toward understanding the multiscale spatial spectrum of solar convection

2012 ◽  
Vol 8 (S294) ◽  
pp. 361-363
Author(s):  
A. V. Getling ◽  
O. S. Mazhorova ◽  
O. V. Shcheritsa
Keyword(s):  
Convective Instability ◽  
Convective Flow ◽  
Large Scale ◽  
Fluid Layer ◽  
Boussinesq Equations ◽  
Spatial Spectrum ◽  
Small Scale ◽  
Two Dimensional ◽  
Solar Convection

AbstractConvection is simulated numerically based on two-dimensional Boussinesq equations for a fluid layer with a specially chosen stratification such that the convective instability is much stronger in a thin subsurface sublayer than in the remaining part of the layer. The developing convective flow has a small-scale component superposed onto a basic large-scale roll flow.

Plane turbulent jets in a bounded fluid layer

1992 ◽  
Vol 241 ◽  
pp. 587-614 ◽  
Author(s):  
T. Dracos ◽  
M. Giger ◽  
G. H. Jirka
Keyword(s):  
Experimental Investigation ◽  
Cross Section ◽  
Fluid Layer ◽  
Three Dimensional ◽  
Turbulent Jets ◽  
Two Dimensional ◽  
Vortical Structures ◽  
Secondary Currents ◽  
Fluid Layers ◽  
Bounding Surfaces

An experimental investigation of plane turbulent jets in bounded fluid layers is presented. The development of the jet is regular up to a distance from the orifice of approximately twice the depth of the fluid layer. From there on to a distance of about ten times the depth, the flow is dominated by secondary currents. The velocity distribution over a cross-section of the jet becomes three-dimensional and the jet undergoes a constriction in the midplane and a widening near the bounding surfaces. Beyond a distance of approximately ten times the depth of the bounded fluid layer the secondary currents disappear and the jet starts to meander around its centreplane. Large vortical structures develop with axes perpendicular to the bounding surfaces of the fluid layer. With increasing distance the size of these structures increases by pairing. These features of the jet are associated with the development of quasi two-dimensional turbulence. It is shown that the secondary currents and the meandering do not significantly affect the spreading of the jet. The quasi-two-dimensional turbulence, however, developing in the meandering jet, significantly influences the mixing of entrained fluid.

On Extension of “Heatline” and “Massline” Concepts to Reacting Flows Through Use of Conserved Scalars

2002 ◽  
Vol 124 (4) ◽  
pp. 791-799 ◽  
Author(s):  
Achintya Mukhopadhyay ◽  
Xiao Qin ◽  
Suresh K. Aggarwal ◽  
Ishwar K. Puri
Keyword(s):  
Diffusion Coefficients ◽  
Reacting Flows ◽  
Scalar Transport ◽  
Zero Gravity ◽  
Two Dimensional ◽  
Total Enthalpy ◽  
Mass Fractions ◽  
New Formulation ◽  
Elemental Mass ◽  
Qualitative Picture

A new formulation for extending the concept of heatlines and masslines to reacting flows through use of conserved scalars has been proposed. The formulation takes into account the distinct diffusion coefficients of different species. Results have been obtained for a number of two-dimensional nonreacting and reacting free shear flows under normal and zero gravity. For nonreacting flows, total enthalpy and elemental mass fractions have been used as the transported conserved scalars. For reacting flows, mixture fractions, defined as normalized elemental mass fractions and enthalpy, have been employed. The results show this concept to be a useful tool for obtaining better insights into the global qualitative picture of scalar transport for both nonreacting and reacting flows.

Flow analysis of biconvective heat and mass transfer of two-dimensional couple stress fluid over a paraboloid of revolution

2020 ◽  
Vol 34 (11) ◽  
pp. 2050110 ◽  
Author(s):  
Ahmed Zeeshan ◽  
Zeeshan Ali ◽  
Mohammad Rahimi Gorji ◽  
Farooq Hussain ◽  
S. Nadeem
Keyword(s):  
Boundary Layer ◽  
Couple Stress ◽  
Fluid Layer ◽  
Flow Analysis ◽  
Couple Stress Fluid ◽  
Two Dimensional ◽  
Nonlinear Odes ◽  
Similarity Transformations ◽  
Paraboloid Of Revolution ◽  
Stream Functions

In this paper, two-dimensional non-Newtonian couple stress fluid flow over the upper horizontal surface of a paraboloid (uhsp) (shaped like a submarine or any aerodynamical automobile) is investigated. At the freestream, a stretching of the fluid layer is assumed along with catalytic surface reaction which tends to induce the flow in the fluid-saturated domain. The problem is modeled by engaging laws of conservation for mass, momentum, heat and concentration. Velocity components are converted to stream functions and similarity transformations to reduce the dependent and independent variables in the partial differential equation describing the flow. Stream functions ideally satisfy continuity equation and transformation to reduce the PDEs to the system of coupled nonlinear ODEs. The numerical solution of these equations is obtained using the shooting-RKF method. The graphical results show that both the lateral and horizontal velocities decrease by increasing the couple stress material parameter and cause the temperature to rise. The thermal boundary layer decreases subject to the thickness parameter and has appositive effects on concentration boundary layer. Finally, numerical results have also been tabulated.

Throughflow effects on convective instability in superposed fluid and porous layers

1991 ◽  
Vol 231 ◽  
pp. 113-133 ◽  
Author(s):  
Falin Chen
Keyword(s):  
Porous Layer ◽  
Convective Instability ◽  
Fluid Layer ◽  
Critical Rayleigh Number ◽  
Vertical Direction ◽  
Single Layer ◽  
Layer Depth ◽  
Onset Of Convection ◽  
Precise Control ◽  
Porous Layers

We implement a linear stability analysis of the convective instability in superposed horizontal fluid and porous layers with throughflow in the vertical direction. It is found that in such a physical configuration both stabilizing and destabilizing factors due to vertical throughflow can be enhanced so that a more precise control of the buoyantly driven instability in either a fluid or a porous layer is possible. For ζ = 0.1 (ζ, the depth ratio, defined as the ratio of the fluid-layer depth to the porous-layer depth), the onset of convection occurs in both fluid and porous layers, the relation between the critical Rayleigh number Rcm and the throughflow strength γm is linear and the Prandtl-number (Prm) effect is insignificant. For ζ ≥ 0.2, the onset of convection is largely confined to the fluid layer, and the relation becomes Rcm ∼ γ2m for most of the cases considered except for Prm = 0.1 with large positive γm where the relation Rcm ∼ γ3m holds. The destabilizing mechanisms proposed by Nield (1987 a, b) due to throughflow are confirmed by the numerical results if considered from the viewpoint of the whole system. Nevertheless, from the viewpoint of each single layer, a different explanation can be obtained.

scholarly journals The validity of two-dimensional models of a rotating shallow fluid layer

2020 ◽  
Vol 900 ◽  
Author(s):  
David G. Dritschel ◽  
Mohammad Reza Jalali
Keyword(s):  
Fluid Layer ◽  
Two Dimensional ◽  
Dimensional Models ◽  
Image Position

Abstract

Direct numerical simulation of instabilities in a two-dimensional near-critical fluid layer heated from below

2001 ◽  
Vol 442 ◽  
pp. 119-140 ◽  
Author(s):  
S. AMIROUDINE ◽  
P. BONTOUX ◽  
P. LARROUDÉ ◽  
B. GILLY ◽  
B. ZAPPOLI
Keyword(s):  
Boundary Layer ◽  
Critical Point ◽  
Stokes Equations ◽  
Fluid Layer ◽  
Vertical Direction ◽  
Single Layer ◽  
Bulk Temperature ◽  
Two Dimensional ◽  
Piston Effect ◽  
The Stability

An analysis of the hydrodynamic stability of a fluid near its near critical point – initially at rest and in thermodynamic equilibrium – is considered in the Rayleigh–Bénard configuration, i.e. heated from below. The geometry is a two-dimensional square cavity and the top and bottom walls are maintained at constant temperatures while the sidewalls are insulated. Owing to the homogeneous thermo-acoustic heating (piston effect), the thermal field exhibits a very specific structure in the vertical direction. A very thin hot thermal boundary layer is formed at the bottom, then a homogeneously heated bulk settles in the core at a lower temperature; at the top, a cooler boundary layer forms in order to continuously match the bulk temperature with the colder temperature of the upper wall. We analyse the stability of the two boundary layers by numerically solving the Navier–Stokes equations appropriate for a van der Waals' gas slightly above its critical point. A finite-volume method is used together with an acoustic filtering procedure. The onset of the instabilities in the two different layers is discussed with respect to the results of the theoretical stability analyses available in the literature and stability diagrams are derived. By accounting for the piston effect the present results can be put within the framework of the stability analysis of Gitterman and Steinberg for a single layer subjected to a uniform, steady temperature gradient.

The effective film viscosity coefficients of a thin floating fluid layer

1997 ◽  
Vol 344 ◽  
pp. 335-337 ◽  
Author(s):  
ALASTAIR D. JENKINS ◽  
KRISTIAN B. DYSTHE
Keyword(s):  
Shear Stress ◽  
Thin Layer ◽  
Tangential Stress ◽  
Constitutive Relation ◽  
Shear Viscosity ◽  
Fluid Layer ◽  
Tangential Velocity ◽  
Two Dimensional ◽  
Viscosity Coefficients ◽  
Lower Fluid

We derive a constitutive relation, relating the tangential stress, tangential velocity, thickness h, and viscosity μ, for a thin layer of Newtonian fluid on top of a fluid substrate. We find that the upper layer exerts a viscous tangential shear stress on the lower fluid, behaving as if it were a film with a two-dimensional shear viscosity equal to μh, and a dilatational viscosity 3μh.

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