Predictions of Momentum Transfer Between Rotating Cylinders: The Narrow Gap Problem

1972 ◽  
Vol 39 (1) ◽  
pp. 33-35 ◽  
Author(s):  
I. Catton ◽  
P. Ayyaswamy
Keyword(s):  
Momentum Transfer ◽  
Taylor Number ◽  
Rotating Cylinders ◽  
Comparison With Experiment ◽  
Number Comparison ◽  
Wide Range ◽  
Secondary Motion ◽  
Marginal State ◽  
Range Of Values ◽  
Molecular Viscosity

The contributions to momentum transfer by secondary motion, which arises beyond the marginal state of stability in a layer of fluid confined between rotating cylinders is calculated by an integral method. The procedure invokes the “shape assumption” due to Stuart. Results are presented in terms of an effective viscosity to molecular viscosity ratio that is a function of Taylor number. Comparison with experiment is found to be excellent over a wide range of values of the Taylor number (up to 1000 times the critical value).

The flat plate boundary layer. Part 1. Numerical integration of the Orr–-Sommerfeld equation

1970 ◽  
Vol 43 (4) ◽  
pp. 801-811 ◽  
Author(s):  
R. Jordinson
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Plate Boundary ◽  
Mean Flow ◽  
Comparison With Experiment ◽  
Wide Range ◽  
The Mean ◽  
Sommerfeld Equation ◽  
Range Of Values ◽  
Flat Plate Boundary Layer

Numerical space-amplified solutions of the Orr-Sommerfeld equation for the case of a boundary layer on a flat plate have been calculated for a wide range of values of frequency and Reynolds number. The mean flow is assumed to be parallel and given by the appropriate component of the Blasius solution. The results are presented in a form suitable for comparison with experiment and are also compared with calculations of earlier authors.

Flow Stability in Rotating Cylinders With a Porous Lining

2009 ◽  
Author(s):  
M. Subotic ◽  
F. C. Lai
Keyword(s):  
Flow Instability ◽  
Three Dimensional ◽  
Flow Stability ◽  
Taylor Number ◽  
Rotating Cylinders ◽  
Wide Range ◽  
Fluid Layers ◽  
Stabilizing Effect ◽  
Porous Sleeve ◽  
Porous Lining

The effects of porous sleeve properties on the flow stability in rotating cylinders are numerically investigated in this study. To this end, three-dimensional momentum equations for the porous and fluid layers are formulated separately in terms of velocity and vorticity. These equations are then numerically solved over a wide range of parameters (10−2 ≤ Da ≤ 10−5, 2000 ≤ Ta ≤ 5000) to determine the critical Taylor number for the onset of flow instability for various porous sleeve properties. The results obtained show that the presence of a porous sleeve in general has a stabilizing effect on the flow in the annulus.

The stability of elastico-viscous flow between rotating cylinders. Part 1

1964 ◽  
Vol 18 (1) ◽  
pp. 33-43 ◽  
Author(s):  
R. H. Thomas ◽  
K. Walters
Keyword(s):  
Viscous Flow ◽  
Viscous Liquid ◽  
Narrow Channel ◽  
Cell Length ◽  
Taylor Number ◽  
Relative Rotation ◽  
Rotating Cylinders ◽  
Concentric Cylinders ◽  
Secondary Motion ◽  
The Stability

Consideration is given to the flow of an idealized elastico-viscous liquid contained in the narrow channel between two concentric cylinders, the motion being due to the relative rotation of the cylinders. It is shown that the presence of elasticity in the liquid lowers the value of the critical Taylor number at which instability occurs. The secondary motion arising at the onset of instability has the usual cellular pattern, the cell length being decreased by the presence of elasticity in the liquid.

scholarly journals Entanglement entropy in cubic gravitational theories

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Elena Cáceres ◽  
Rodrigo Castillo Vásquez ◽  
Alejandro Vilar López
Keyword(s):  
Entanglement Entropy ◽  
Gravitational Theory ◽  
Riemann Tensor ◽  
Holographic Entanglement Entropy ◽  
Gravitational Theories ◽  
Entropy Functional ◽  
Wide Range ◽  
Splitting Problem ◽  
Range Of Values

Abstract We derive the holographic entanglement entropy functional for a generic gravitational theory whose action contains terms up to cubic order in the Riemann tensor, and in any dimension. This is the simplest case for which the so-called splitting problem manifests itself, and we explicitly show that the two common splittings present in the literature — minimal and non-minimal — produce different functionals. We apply our results to the particular examples of a boundary disk and a boundary strip in a state dual to 4- dimensional Poincaré AdS in Einsteinian Cubic Gravity, obtaining the bulk entanglement surface for both functionals and finding that causal wedge inclusion is respected for both splittings and a wide range of values of the cubic coupling.

scholarly journals A Comparison of Some Methods of Deriving the Instantaneous Unit Hydrograph

1985 ◽  
Vol 16 (1) ◽  
pp. 1-10 ◽  
Author(s):  
V. P. Singh ◽  
C. Corradini ◽  
F. Melone
Keyword(s):  
Peak Flow ◽  
Central Italy ◽  
Effective Rainfall ◽  
Unit Hydrograph ◽  
Time To Peak ◽  
Wide Range ◽  
Instantaneous Unit Hydrograph ◽  
Similar Accuracy ◽  
Two Parameters ◽  
Range Of Values

The geomorphological instantaneous unit hydrograph (IUH) proposed by Gupta et al. (1980) was compared with the IUH derived by commonly used time-area and Nash methods. This comparison was performed by analyzing the effective rainfall-direct runoff relationship for four large basins in Central Italy ranging in area from 934 to 4,147 km2. The Nash method was found to be the most accurate of the three methods. The geomorphological method, with only one parameter estimated in advance from the observed data, was found to be little less accurate than the Nash method which has two parameters determined from observations. Furthermore, if the geomorphological and Nash methods employed the same information represented by basin lag, then they produced similar accuracy provided the other Nash parameter, expressed by the product of peak flow and time to peak, was empirically assessed within a wide range of values. It was concluded that it was more appropriate to use the geomorphological method for ungaged basins and the Nash method for gaged basins.

Lubricating motion of a sphere towards a thin porous slab with Saffman slip condition

2019 ◽  
Vol 867 ◽  
pp. 949-968 ◽  
Author(s):  
Sondes Khabthani ◽  
Antoine Sellier ◽  
François Feuillebois
Keyword(s):  
Slip Length ◽  
Solid Sphere ◽  
Slip Condition ◽  
Darcy Law ◽  
Slab Thickness ◽  
Wide Range ◽  
Sphere Radius ◽  
Permeability Parameter ◽  
Interface Slip ◽  
Range Of Values

Near-contact hydrodynamic interactions between a solid sphere and a plane porous slab are investigated in the framework of lubrication theory. The size of pores in the slab is small compared with the slab thickness so that the Darcy law holds there. The slab is thin: that is, its thickness is small compared with the sphere radius. The considered problem involves a sphere translating above the slab together with a permeation flow across the slab and a uniform pressure below. The pressure is continuous across both slab interfaces and the Saffman slip condition applies on its upper interface. An extended Reynolds-like equation is derived for the pressure in the gap between the sphere and the slab. This equation is solved numerically and the drag force on the sphere is calculated therefrom for a wide range of values of the slab interface slip length and of the permeability parameter $\unicode[STIX]{x1D6FD}=24k^{\ast }R/(e\unicode[STIX]{x1D6FF}^{2})$, where $k^{\ast }$ is the permeability, $e$ is the porous slab thickness, $R$ is the sphere radius and $\unicode[STIX]{x1D6FF}$ is the gap. Moreover, asymptotics expansions for the pressure and drag are derived for high and low $\unicode[STIX]{x1D6FD}$. These expansions, which agree with the numerics, are also handy formulae for practical use. All results match with those of other authors in particular cases. The settling trajectory of a sphere towards a porous slab in a fluid at rest is calculated from these results and, as expected, the time for reaching the slab decays for increasing slab permeability and upper interface slip length.

The State of the Art of Rubber-Seal Technology

1987 ◽  
Vol 60 (3) ◽  
pp. 381-416 ◽  
Author(s):  
B. S. Nau
Keyword(s):  
State Of The Art ◽  
Test Procedure ◽  
Working Party ◽  
The State ◽  
Supporting Evidence ◽  
Wide Range ◽  
Lip Seals ◽  
Alternative Hypotheses ◽  
Series Of Experiments ◽  
Range Of Values

Abstract The understanding of the engineering fundamentals of rubber seals of all the various types has been developing gradually over the past two or three decades, but there is still much to understand, Tables V–VII summarize the state of the art. In the case of rubber-based gaskets, the field of high-temperature applications has scarcely been touched, although there are plans to initiate work in this area both in the U.S.A. at PVRC, and in the U.K., at BHRA. In the case of reciprocating rubber seals, a broad basis of theory and experiment has been developed, yet it still is not possible to design such a seal from first principles. Indeed, in a comparative series of experiments run recently on seals from a single batch, tested in different laboratories round the world to the same test procedure, under the aegis of an ISO working party, a very wide range of values was reported for leakage and friction. The explanation for this has still to be ascertained. In the case of rotary lip seals, theories and supporting evidence have been brought forward to support alternative hypotheses for lubrication and sealing mechanisms. None can be said to have become generally accepted, and it remains to crystallize a unified theory.

scholarly journals Framing the Values of Vernacular Architecture for a Value-Based Conservation: A Conceptual Framework

2021 ◽  
Vol 13 (9) ◽  
pp. 4974
Author(s):  
Obafemi A. P. Olukoya
Keyword(s):  
Vernacular Architecture ◽  
Conservation Strategy ◽  
Participatory Process ◽  
Value Assessment ◽  
A Value ◽  
Wide Range ◽  
Flexible Framework ◽  
Value Model ◽  
Contextual Values ◽  
Range Of Values

While a growing number of researchers have provided series of tough critiques of the typology-led heritage value assessment over the recent years, the impacts have been constrained by the continued obsession with expanding the list of the predetermined value typologies rather than escaping its limitations. While these sustained debates have provided important insights, this article argues that operationalizing these predetermined ‘one-size-fits-all’ value typologies is symptomatic of a number of shortcomings, especially in the context of capturing the pluralities of values in contextualized heritage such as vernacular architecture. It also often undermines inclusivity and participation in the valuing processes. However, rather than simply rejecting the values-based paradigm, this article proposes a conceptual value assessment framework that is informed by the theorization of vernacular architecture as a contextualized heritage. The proposed Vernacular Value Model (VVM) puts forward the ‘when(s)’ and ‘how(s)’ of amalgamating both technical and normative processes to capture the range of contextual values present in built vernacular heritage. To this end, this article posits that by drawing on such a proposed flexible framework, the conservation strategy for built vernacular heritage can be propagated as an inclusive and participatory process which captures the wide range of values for a more sustainable practices for conservation.

Respiratory Mechanics of Sound Production in Chickens and Geese

1978 ◽  
Vol 72 (1) ◽  
pp. 229-250
Author(s):  
J. H. BRACKENBURY
Keyword(s):  
Respiratory System ◽  
Simultaneous Measurement ◽  
Sound Production ◽  
High Pressures ◽  
Respiratory Mechanics ◽  
Air Flow ◽  
Tracheal Pressure ◽  
Wide Range ◽  
Range Of Values ◽  
Respiratory Movements

1. Air flow, air sac pressure and tracheal pressure were measured in chickens and geese during a variety of different vocal and non-vocal activities. 2. Air flow and air sac pressure may rise to 500 ml s−1 and 60 cmH2O (6 103 N/m2) respectively during a crow in the chicken. During a sequence of honks in the goose the corresponding values are 650 ml s−1 and 25 cmH2O(2.5 × 10 3 N/m2) respectively. 3. The volume of air delivered through the respiratory system during a single crow is more than 400 ml, almost equivalent to the total volume of the lung air sac system. 4. The efficiency of the chicken syrinx as a sound producing instrument, estimated by comparing the sound energy radiated with the energy consumed in the expulsion of air during a crow, appears to be less than 2 %. 5. Cutting the paired sternotrachealis muscles had no effect on vocalization. 6. The measured rates of clucking, cheeping and honking in adult chickens, young chicks and adult geese respectively are comparable to the characteristic rates of panting in these animals. This points to a similarity in the nature of the respiratory movements involved in each case. 7. Simultaneous measurement of tracheal flow and pressure indicate that the glottis is capable of controlling air flow over a wide range of values in the presence of high pressures. During defaecation the valve is closed whilst during coughing it is wide open.

Stress Analysis of Pseudo-Plastic Flow Between Rotating Cylinders

2011 ◽  
Author(s):  
Nariman Ashrafi ◽  
Habib Karimi Haghighi
Keyword(s):  
Dynamical System ◽  
Stress Analysis ◽  
Plastic Flow ◽  
Galerkin Projection ◽  
Narrow Gap ◽  
Rotating Cylinders ◽  
Flow Parameters ◽  
Wide Range ◽  
Stress Components ◽  
Mathematica Software

Stress analysis of Pseudo-Plastic flow between rotating cylinders is studied in the narrow gap limit. The Galerkin projection method is used to derive dynamical system from the conservation of mass and momentum equations. Flow parameters were obtained using IMSL and also verified by Mathematica Software. Stresses are computed in a wide range of the Pseudo-Plastic effects. Azimuthal stress was found to be far greater than other stress components. All stress components increased as Pseudo-Plasticity decreased. Furthermore, complete stress and viscosity maps are presented for different scenarios in the flow regime.

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