An experimental study of shear-enhanced convection in a mushy layer

2008 ◽  
Vol 612 ◽  
pp. 363-385 ◽  
Author(s):  
JEROME A. NEUFELD ◽  
J. S. WETTLAUFER
Keyword(s):  
Shear Flow ◽  
Flow Direction ◽  
Flow Speed ◽  
Experimental Results ◽  
Mushy Layer ◽  
Engineering Systems ◽  
Controlled Cooling ◽  
A Value ◽  
Constant Rate ◽  
Theoretical Predictions

The influence of an external shear flow on the evolution of a solidifying array of dendritic crystals, termed a mushy layer, is investigated through controlled cooling of an aqueous ammonium chloride solution in a laboratory flume. The controlled cooling produces a mushy layer that grows at a constant rate from the base of the flume over which a laminar shear flow is applied. We find a critical flow speed above which a spatiotemporal variation of the solid fraction of the layer appears with a planform transverse to the flow direction. The presence of this distinctive pattern of spanwise crevasses is compared with a simplified stability analysis in which the motion of the external fluid over the corrugated mush–liquid interface produces a pressure perturbation that drives flow and phase change within the mushy layer. This flow leads to a pattern of solidification and dissolution that is compared to the experimental results. The physical mechanism underlying the pattern formation is confirmed by the agreement between the theoretical predictions and experimental results. Finally, the comparison between theory and experiment provides a value for the mushy layer permeability, the evolution of which is of relevance to a host of geophysical, biological and engineering systems.

The Development of the Reynolds Stress Tensor in a Turbulent Shear Flow

1970 ◽  
Vol 92 (4) ◽  
pp. 836-842
Author(s):  
S. J. Shamroth ◽  
H. G. Elrod
Keyword(s):  
Shear Flow ◽  
Stress Tensor ◽  
Linear Model ◽  
Reynolds Stress ◽  
Experimental Results ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Reynolds Stress Tensor ◽  
Theoretical Predictions

The development of the normalized Reynolds stress tensor, uiuj/q2, in the region upstream of a fully developed, turbulent shear flow is investigated. An inviscid, linear model is used to predict values of the normalized Reynolds stress tensor as a function of position. The theoretical predictions are then compared with experimental results.

Relaxation behind shock waves in ionizing neon

1991 ◽  
Vol 227 ◽  
pp. 617-640 ◽  
Author(s):  
T. J. Mcintyre ◽  
A. F. P. Houwing ◽  
R. J. Sandeman ◽  
H.-A. Bachor
Keyword(s):  
Excited States ◽  
Heavy Particle ◽  
Experimental Results ◽  
Quasi Equilibrium ◽  
Collisional Excitation ◽  
A Value ◽  
Theoretical Predictions ◽  
Current Kinetic ◽  
Equilibrium Region

Experiments in ionizing neon are described in which heavy-particle and electron densities are measured and compared with the current kinetic model. The experimental results allow a determination of the atom-atom collisional excitation cross-section constant, giving a value of (8±2) × 10−20 cm2/eV for the range of conditions examined. The population of two of the excited-state levels of the atom are measured and compared with theoretical predictions. The experimental populations are found to follow the expected behaviour in the quasi-equilibrium region, but are several orders of magnitude higher than predicted in the nonequilibrium zone. These findings suggest that the depopulation of excited states through ionizing collisions occurs more slowly than expected. Absorption linewidths and line shifts are also measured in the quasi-equilibrium region and found to compare well with theory. A small precurson population is also observed and population measurements in this region are compared with other experimental results in argon and krypton.

Molecular and Textural Ordering of Thermotropic Polymers in Shear Flow

1996 ◽  
Vol 461 ◽  
Author(s):  
A Romo-Uribe ◽  
P. T. Mathers ◽  
K. P. Chaffee ◽  
C.D Han
Keyword(s):  
Shear Flow ◽  
Flow Direction ◽  
The State ◽  
Molecular Order ◽  
Macroscopic Behavior ◽  
Constant Rate ◽  
Shear Orientation ◽  
Degree Of Orientation ◽  
High Degree ◽  
Dynamic Scattering

ABSTRACTThe texture and microstructural order present in mesomorphic polymers and their relation to their macroscopic behavior has been investigated using rheological, optical and dynamic scattering (WAXS and SALS) experiments. Shear orientation is observed under constant rate-of-deformation conditions where this orientation is always parallel to the flow direction. However, the high degree of orientation suggested by optical and SALS measurements is not reflected in the degree of molecular order observed in WAXS experiments. After cessation of flow, a rapid relaxation of stress is observed, while only little microstructural relaxation is found; i.e., the state of orientation is very stable

Dynamics of the Oscillogyro

1973 ◽  
Vol 15 (3) ◽  
pp. 210-217 ◽  
Author(s):  
D. Ormandy ◽  
L. Maunder
Keyword(s):  
Previous Analysis ◽  
Experimental Results ◽  
Constant Rate ◽  
Theoretical Predictions ◽  
Gyroscopic Instrument ◽  
Tuning Frequency

A previous analysis of the dynamics of this novel form of gyroscopic instrument is extended to include its response to vibratory inputs. Experimental results are presented which confirm the theoretical predictions both for constant-rate inputs and for vibratory excitation. In particular, it is shown that the tuned oscillogyro, which is the usual operational form of the instrument, is sensitive to excitation at twice the tuning frequency.

Shear-enhanced convection in a mushy layer

2008 ◽  
Vol 612 ◽  
pp. 339-361 ◽  
Author(s):  
JEROME A. NEUFELD ◽  
J. S. WETTLAUFER
Keyword(s):  
Shear Flow ◽  
Flow Speed ◽  
External Flow ◽  
Liquid Interface ◽  
Mushy Layer ◽  
Dynamic Parameters ◽  
Bulk Fluid ◽  
Layer Mode ◽  
Buoyancy Driven Convection ◽  
The Stability

We investigate the effect of an external shear flow on the buoyant instabilities inherent in the directional solidification of a dendritic mushy layer. In the presence of an external shear flow, perturbations of the mush–liquid interface lead to perturbed flow in the bulk fluid that create pressure variations along the mush–liquid interface. These pressure variations drive flow in the mushy layer. A numerical analysis of the stability of the system provides the critical porous-medium Rayleigh number as a function of both the external flow speed and the wavenumber of the interfacial perturbations. In the limit of zero external flow we recover the so-called boundary and mushy layer modes of buoyancy-driven convection first established by Worster (J. Fluid Mech., vol. 237, 1992b, p. 649). We find that the application of an external flow can significantly reduce the stability of both the boundary and mushy layer modes. The resultant forced mushy layer mode gives rise to the formation of channels of reduced solid fraction perpendicular to the applied flow that are distinct from the planform found in the absence of an external flow. The stability of the system is examined as a function of the principal thermodynamic and dynamic parameters, and the results are applied to the solidification of sea ice in the presence of vigorous oceanic flow.

scholarly journals Simulation of Flexible Fibre Particle Interaction with a Single Cylinder

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 191
Author(s):  
Naser Hamedi ◽  
Lars-Göran Westerberg
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Particle Interaction ◽  
Orientation Angle ◽  
Factors Affecting ◽  
Single Cylinder ◽  
Flow Past ◽  
Fibre Suspension

In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.

scholarly journals Quantitative Experimental and Theoretical Investigations on the Interaction of Shock Waves with Magnetic Fields

1969 ◽  
Vol 24 (10) ◽  
pp. 1449-1457
Author(s):  
H. Klingenberg ◽  
F. Sardei ◽  
W. Zimmermann
Keyword(s):  
Magnetic Fields ◽  
Shock Waves ◽  
Physical Model ◽  
Spectroscopic Method ◽  
Experimental Results ◽  
Dimensional Theory ◽  
One Dimensional ◽  
Theoretical Investigations ◽  
Theoretical Predictions ◽  
Interaction Of Shock Waves

Abstract In continuation of the work on interaction between shock waves and magnetic fields 1,2 the experiments reported here measured the atomic and electron densities in the interaction region by means of an interferometric and a spectroscopic method. The transient atomic density was also calculated using a one-dimensional theory based on the work of Johnson3 , but modified to give an improved physical model. The experimental results were compared with the theoretical predictions.

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