bluuebunny/crossref_metadata_2025 huggingface dataset:
Cheesemaking, compositional and functional characteristics of
low-moisture part-skim Mozzarella cheese from bovine milks
containing κ-casein AA, AB or BB genetic variants
Authors: WALSH CATHERINE D. , GUINEE TIMOTHY P. , HARRINGTON DERMOT , MEHRA RAJ , MURPHY JOHN , FITZGERALD RICHARD J.
Published: July 2002

Low-moisture part-skim Mozzarella cheeses were made, at pilot scale

(450 kg), on five occasions at weekly intervals from milks containing κ-casein
AA, AB
or BB genetic variants. Compared with κ-casein A variant milks, the
κ-casein B
variant milks were associated with higher concentrations of casein
(P<0·001), whey protein (P<0·02)
and
total protein (P<0·001), superior curd-forming properties

(P<0·05) and increased cheese yields (P<0·05).

The moisture-adjusted (to 465 g/kg) cheese yields for the
κ-casein AA, AB and BB cheeses were 91·5, 100·6, and

102·5 kg/1000 kg milk respectively. κ-Casein variant
had no significant effect on the
proteolysis and ripening of uncooked cheese or on the functionality (melt
time,
flowability and stretchability) of the cooked cheese during the course
of a 90 d
ripening period.
Effect of interactions between denatured whey proteins and casein
micelles on the formation and rheological properties of acid skim
milk gels
Authors: LUCEY JOHN A. , TAMEHANA MICHELLE , SINGH HARJINDER , MUNRO PETER A.
Published: July 2002

The effect of interactions of denatured whey proteins with casein
micelles
on the rheological properties of acid milk gels was investigated. Gels
were made by
acidification of skim milk with glucono-δ-lactone at 30°C using
reconstituted skim
milk powders (SMP; both low- and ultra-low-heat) and fresh skim milk (FSM).
The
final pH of the gels was ∼4·6. Milks containing associated or
‘bound’ denatured
whey proteins (BDWP) with casein micelles were made by resuspending the
ultracentrifugal pellet of heated milk in ultrafiltration permeate. Milks
containing
‘soluble’ denatured whey protein (SDWP) aggregates were formed
by heat treatment
of an ultracentrifugal supernatant which was then resuspended with the
pellet. Acid
gels made from unheated milks had low storage moduli, G′,
of <20 Pa. Heating
milks at 80°C for 30 min resulted in acid gels with G′
in the range 390–430 Pa. The
loss tangent (tan δ) of gels made from heated milk increased after
gelation to attain
a maximum at pH ∼5·1, but no maximum was observed in gels made
from unheated
milk. Acid gels made from milks containing BDWP that were made from low-heat
SMP, ultra-low-heat SMP and FSM had G′ of about 250, 270
and 310 Pa respectively.
Acid gels made from milks containing SDWP that were made from ultra-low-heat
SMP or FSM had G′ values in the range 17–30 Pa, but
gels made from low-heat SMP
had G′ of ∼140 Pa. It was concluded that BDWP were important
for the increased
G′ of acid gels made from heated milk. Addition of N-ethylmaleimide
(NEM) to low-heat
reconstituted milk, to block the —SH groups, resulted in a reduction
of the G′
of gels formed from heated milk but did not reduce G′ to
the value of unheated milk.
Addition of 20 mm-NEM to FSM, prior to heat treatment, resulted
in gels with a
lower G′ value than gels made from reconstituted low-heat
SMP. It was suggested
that small amounts of denatured whey proteins associated with casein micelles
during low-heat SMP manufacture were probably responsible for the higher
G′ of gels
made from milk containing SDWP and from milk heated in the presence of
20 mm-NEM,
compared with gels made from FSM.
Characteristics of transport systems of L-alanine in mouse mammary
gland and their regulation by lactogenic hormones: evidence for two
broad spectrum systems
Authors: SHARMA REKHA , KANSAL VINOD K.
Published: July 2002

The characteristics of the transport systems of L-alanine in lactating
mouse mammary gland and their regulation by lactogenic hormones have been
studied. L-alanine uptake was mediated by three Na+-dependent and one Na+-
independent systems. The 2-(methylamino)isobutyric acid-sensitive component of
Na+-dependent uptake exhibited the usual characteristics of system A. Cl−
dependency has been established for system A. The other two Na+-dependent
systems, which we have named BCl−-dependent and BCl−-independent, are described
for the first time. These are systems with broad specificity and were distinguished on
the basis of inhibition analysis, Cl− dependency and the effect of preloading
mammary tissue with amino acids. The Na+-independent route was identified as system L, which operates independent of
Cl−. The A, L and BCl−-independent
transport systems were upregulated in pregnant mouse mammary tissue cultured in
vitro in the presence of lactogenic hormones (insulin plus cortisol plus prolactin).
Insulin alone also upregulated systems A and L to some extent in pregnant mouse
mammary tissue. BCl−-dependent activity was not detected in pregnant mouse
mammary tissue and was not induced by lactogenic hormones in vitro.
Three-dimensional MHD flows in rectangular ducts with internal obstacles
Authors: MÜCK B. , GÜNTHER C. , MÜLLER U. , BÜHLER L.
Published: July 2002

This paper presents a numerical simulation of the magnetohydrodynamic (MHD)
liquid metal flow around a square cylinder placed in a rectangular duct. In the
hydrodynamic case, for a certain parameter range the well-known Kármán vortex
street with three-dimensional flow patterns is observed, similar to the flow around
a circular cylinder. In this study a uniform magnetic field aligned with the cylinder
is applied and its influence on the formation and downstream transport of vortices
is investigated. The relevant key parameters for the MHD flow are the Hartmann
number M, the interaction parameter N and the hydrodynamic Reynolds number, all
based on the side length of the cylinder. The Hartmann number M was varied in the
range 0 [les ] M [les ] 85 and the interaction parameter N in the range 0 [les ] N [les ] 36. Results
are presented for two fixed Reynolds numbers Re = 200 and Re = 250. The magnetic
Reynolds number is assumed to be very small. The results of the numerical simulation
are compared with known experimental and theoretical results. The hydrodynamic
simulation shows characteristic intermittent pulsations of the drag and lift force on
the cylinder. At Re = 200 a mix of secondary spanwise three-dimensional instabilities
(A and B mode, rib vortices) could be observed. The spanwise wavelength of the
rib vortices was found to be about 2–3 cylinder side lengths in the near wake. At
Re = 250 the flow appears more organized showing a regular B mode pattern and
a spanwise wavelength of about 1 cylinder side length. With an applied magnetic
field a quasi-two-dimensional flow can be obtained at low N ≈ 1 due to the strong
non-isotropic character of the electromagnetic forces. The remaining vortices have
their axes aligned with the magnetic field. With increasing magnetic fields these
vortices are further damped due to Hartmann braking. The result that the ‘quasi-two-dimensional’ vortices have a curvature in the direction of the magnetic field can be
explained by means of an asymptotic analysis of the governing equations. With very
high magnetic fields the time-dependent vortex shedding can be almost completely
suppressed. By three-dimensional visualization it was possible to show characteristic
paths of the electric current for this kind of flow, explaining the action of the Lorentz
forces.
Sound generation by coaxial collision of two vortex rings
Authors: INOUE O. , HATTORI Y. , SASAKI T.
Published: July 2002

Sound pressure fields generated by coaxial collisions of two vortex rings with
equal/unequal strengths are simulated numerically. The axisymmetric, unsteady, compressible
Navier–Stokes equations are solved by a finite difference method, not only
for a near field but also for a far field. The sixth-order-accurate compact Padé scheme
is used for spatial derivatives, together with the fourth-order-accurate Runge–Kutta
scheme for time integration. The results show that the generation of sound is closely
related to the change of direction of the vortex ring motion induced by the mutual interaction
of the two vortex rings. For the case of equal strength (head-on collision), the
change of direction is associated with stretching of the vortex rings. Generated sound
waves consist of compression parts and rarefaction parts, and have a quadrupolar
nature. For the case of unequal strengths, the two vortex rings pass through each
other; the weaker vortex ring moves outside the stronger vortex ring which shows a
loop motion. The number of generated waves depends on the relative strength of the
two vortex rings. The sound pressure includes dipolar and octupolar components, in
addition to monopolar and quadrupolar components which are observed for the case
of a head-on collision.
Acoustically generated vorticity in an internal flow
Authors: ZHAO Q. , STAAB P. L. , KASSOY D. R. , KIRKKOPRU K.
Published: July 2002

A mathematical model is formulated to describe the initiation and evolution of intense
unsteady vorticity in a low Mach number (M), weakly viscous internal flow sustained
by mass addition through the sidewall of a long, narrow cylinder. An O(M) axial
acoustic velocity disturbance, generated by a prescribed harmonic transient endwall
velocity, interacts with the basically inviscid rotational steady injected flow to generate
time-dependent vorticity at the sidewall. The steady radial velocity component convects
the vorticity into the flow. The axial velocity associated with the vorticity field
varies across the cylinder radius and in particular has an instantaneous oscillatory
spatial distribution with a characteristic wavelength O(M) smaller than the radius.
Weak viscous effects cause the vorticity to diffuse on the small radial length scale as
it is convected from the wall toward the axis. The magnitude of the transient vorticity
field is larger by O(M−1) than that in the steady flow.

An initial-boundary-value formulation is employed to find nonlinear unsteady
solutions when a pressure node exists at the downstream exit of the cylinder. The complete
velocity consists of a superposition of the steady flow, an acoustic (irrotational) field
and the rotational component, all of the same magnitude.
Theoretical investigation of unsteady flow interactions with a premixed planar flame
Authors: LIEUWEN TIM
Published: July 2002

This paper presents the results of a theoretical study of the interactions between a
laminar, premixed flame front and a plane acoustic wave. Its objective is to elucidate
the processes that damp or drive acoustic waves as they interact with flames. Using
linear analysis, the characteristics of the acoustic field, the flame's movement and
wrinkling in response to acoustic perturbations, and the acoustic energy that is
produced or dissipated at the flame are calculated. These calculations show that the
net acoustic energy flux out of the flame is controlled by competing acoustic energy
production and dissipation processes. Energy is added to the acoustic field by unsteady
heat release processes resulting from the unsteady flux of unburned reactants through
the flame by fluctuations in the flame speed or density of the unburned reactants.
Energy is dissipated by the transfer of acoustic energy into fluctuations in vorticity
that are generated at the flame front because of the misaligned fluctuating pressure
and mean density gradients (i.e. the baroclinic vorticity production mechanism). The
paper concludes by showing how these results can be generalized to determine the
response of planar flames to an arbitrarily complex acoustic field. The principal
contribution of this work is its demonstration that the excitation of vorticity and
fluctuations in the flame speed have significant qualitative and quantitative affects on
the interactions between flames and acoustic waves.
Equations relating structure functions of all orders
Authors: HILL REGINALD J.
Published: July 2002

Exact equations are given that relate velocity structure functions of arbitrary order
with other statistics. ‘Exact’ means that no approximations are used except that the
Navier–Stokes equation and incompressibility condition are assumed to be accurate.
The exact equations are used to determine the structure function equations of all
orders for locally homogeneous but anisotropic turbulence as well as for the locally
isotropic case. The uses of these equations for investigating the approach to local
homogeneity as well as to local isotropy and the balance of the equations and
identification of scaling ranges are discussed. The implications for scaling exponents
and investigation of intermittency are briefly discussed.
Hydrodynamics of locomotion in the squid Loligo pealei
Authors: ANDERSON ERIK J. , QUINN WILLIE , DE MONT M. EDWIN
Published: July 2002

Potential flow analysis, including unsteady effects, has been applied to live swimming
squid, Loligo pealei. Squid were modelled as slender, axisymmetric bodies. High-speed
video records, recorded at frame rates of 125 to 250 Hz, provided time-varying body
outlines which were digitized automatically. Axisymmetric renderings of these body
outlines and the real motion of the squid were used as the input of the potential
flow analysis. Axial and lateral inviscid fluid forces simply due to the flow past the
squid body were calculated from pressures coefficients obtained from the unsteady
Bernoulli equation. Lateral forces were found to play virtually no role in determining
muscle stresses in squid jet propulsion. Axial pressure forces were also found to be
small in comparison to both net force (based on the observed whole body kinematics)
and estimations of skin friction. These findings demonstrate the effects of the highly
adapted shape of squid with regard to hydrodynamics. The work suggests that skin
friction and working fluid intake are the most significant sources of drag on a
swimming squid.
Exact coherent structures in channel flow
Authors: WALEFFE FABIAN
Published: July 2002

Exact coherent states in no-slip plane Poiseuille flow are calculated by homotopy from
free-slip to no-slip boundary conditions. These coherent states are unstable travelling
waves. They consist of wavy low-speed streaks flanked by staggered streamwise vortices
closely resembling the asymmetric coherent structures observed in the near-wall
region of turbulent flows. The travelling waves arise from a saddle-node bifurcation
at a sub-turbulent Reynolds number with wall-normal, spanwise and streamwise dimensions
smaller than but comparable to 50+, 100+ and 250+, respectively. These
coherent solutions come in pairs with distinct structure and instabilities. There is a
three-dimensional continuum of such exact coherent states.
The thermal signature of a vortex pair impacting a free surface
Authors: SMITH GEOFFREY B. , VOLINO R. J. , HANDLER R. A. , LEIGHTON R. I.
Published: July 2002

The action of a rising vortex pair on the thermal boundary layer at an air–water
interface is studied both experimentally and numerically. The objective is to relate
variations in the surface temperature field to the hydrodynamics of the vortex pair
below. The existence of a thermal boundary layer on the water side of an air–water
interface is well known; it is this boundary layer which is disrupted by the action of
the vortex system. Experimentally, the vortices were generated via the motion of a
pair of submerged flaps. The flow was quantified through simultaneous measurement
of both the subsurface velocity field, via digital particle image velocimetry (DPIV),
and the surface temperature field, via an infrared (IR) sensitive imager. The results
of the physical experiments show a clearly defined disruption of the ambient thermal
boundary layer which is well correlated with the vorticity field below. Numerical
experiments were carried out in a parameter space similar to that of the physical
experiments. Included in the numerical experiments was a simple surfactant model
which enabled the exploration of the complex role surface elasticity played in the
vortex–free surface interaction. The results of this combined experimental and numerical
investigation suggest that surface straining rate is an important parameter in
correlating the subsurface flow with the surface temperature field. A model based on
surface straining rate is presented to explain the interaction.
The disappearance of laminar and turbulent wakes in complex flows
Authors: HUNT J. C. R. , EAMES I.
Published: July 2002

The singular effects of steady large-scale external strain on the viscous wake generated
by a rigid body and the overall flow field are analysed. In an accelerating flow strained
at a positive rate, the vorticity field is annihilated owing to positive and negative
vorticity either side of the wake centreline diffusing into one another and the volume
flux in the wake decreases with downwind distance. Since the wake disappears, the
far-field flow changes from monopolar to dipolar. In this case, the force on the body
is no longer proportional to the strength of the monopole, but is proportional to the
strength of the far field dipole. These results are extended to the case of strained
turbulent wakes and this is verified against experimental wind tunnel measurements
of Keffer (1965) and Elliott & Townsend (1981) for positive and negative strains.
The analysis demonstrates why the total force acting on a body may be estimated by
adding the viscous drag and inviscid force due to the irrotational straining field.

Applying the analysis to the wake region of a rigid body or a bubble shows that the
wake volume flux decreases even in uniform flows owing to the local straining flow in
the near-wake region. While the wake volume flux decreases by a small amount for
the flow over streamline and bluff bodies, for the case of a clean bubble the decrease
is so large as to render Betz's (1925) drag formula invalid.

To show how these results may be applied to complex flows, the effects of a sequence
of positive and negative strains on the wake are considered. The average wake width
is much larger than in the absence of a strain field and this leads to diffusion of
vorticity between wakes and the cancellation of vorticity. The latter mechanism leads
to a net reduction in the volume flux deficit downstream which explains why in
calculations of the flow through groups of moving or stationary bodies the wakes
of upstream bodies may be ignored even though their drag and lift forces have a
significant effect on the overall flow field.
Fully developed travelling wave solutions and

bubble formation in fluidized beds
Authors: GLASSER B. J. , KEVREKIDIS I. G. , SUNDARESAN S.
Published: July 2002

It is well known that most gas fluidized beds of particles bubble,

while most liquid

fluidized beds do not. It was shown by Anderson, Sundaresan & Jackson
(1995),

through direct numerical integration of the volume-averaged equations of
motion for

the fluid and particles, that this distinction is indeed accounted for
by

these equations, coupled with simple, physically credible closure relations
for

the stresses and interphase drag. The aim of the present study is to investigate

how the model equations afford this

distinction and deduce an approximate criterion for separating bubbling
and

non-bubbling systems. To this end, we have computed, making use of numerical

continuation techniques as well as bifurcation theory, the one- and

two-dimensional travelling wave solutions of the volume-averaged equations
for a

wide range of parameter values, and examined the evolution of these travelling
wave

solutions through direct numerical integration. It is demonstrated that
whether

bubbles form or not is dictated by the value of Ω =

(ρsv3t/Ag)

1/2, where ρs is the density of
particles, vt is the terminal settling velocity of an isolated

particle, g is acceleration due to gravity

and A is a measure of the particle phase viscosity. When

Ω is large (> ∼ 30), bubbles

develop easily. It is then suggested that a natural scale for A
is

ρsvtdp so that Ω2 is

simply a Froude number.
A parametric study of Mach reflection in steady flows
Authors: LI H. , BEN-DOR G.
Published: July 2002

The flow fields associated with Mach reflection wave configurations
in

steady flows are

analysed, and an analytical model for predicting the wave configurations
is proposed.

It is found that provided the flow field is free of far-field downstream

influences, the

Mach stem heights are solely determined by the set-up geometry for given

incoming-flow Mach numbers. It is shown that the point at which the Mach
stem

height equals

zero is exactly at the von Neumann transition. For some parameters, the
flow becomes

choked before the Mach stem height approaches zero. It is suggested that

the existence

of a Mach reflection not only depends on the strength and the orientation
of the

incident shock wave, as prevails in von Neumann's three-shock theory,
but

also on the

set-up geometry to which the Mach reflection wave configuration is attached.
The

parameter domain, beyond which the flow gets choked and hence a Mach reflection

cannot be established, is calculated. Predictions based on the present

model are found

to agree well both with experimental and numerical results.
Modelling the response of a vibrating-element

density meter in a two-phase mixture
Authors: BILLINGHAM JOHN
Published: July 2002

A vibrating-element density meter is a mechanical oscillator with
known

properties,

for example a tuning fork or a simple rod, driven to vibrate at a known

frequency. The

oscillator is immersed in a fluid and the resonant frequency measured.
The density of

the fluid can then be inferred. We consider an idealized meter immersed
in two-phase

flows of various types, and investigate whether a simple single-phase interpretation

allows us to deduce the density of the mixture. We find that,

when the density contrast

between the two fluids is not great, the simple interpretation

gives good results, for

example in oil/water flows. However, when the density contrast

is significant, for

example in gas/liquid flows, the simple interpretation is highly inaccurate.
The interaction of a shock wave with a laminar
boundary layer at a compression corner in
high-enthalpy flows including real gas effects
Authors: MALLINSON S. G. , GAI S. L. , MUDFORD N. R.
Published: July 2002

The high-enthalpy, hypersonic flow over a compression corner has
been examined
experimentally and theoretically. Surface static pressure and heat
transfer distributions, along with some flow visualization data, were obtained
in a free-piston shock
tunnel operating at enthalpies ranging from 3 MJ kg−1 to
19 MJ kg−1, with the Mach
number varying from 7.5 to 9.0 and the Reynolds number based on upstream fetch
from 2.7×104 to 2.7×105. The flow was
laminar throughout. The experimental data
compared well with theories valid for perfect gas flow and with other relevant
low-to-moderate enthalpy data, suggesting that for the current experimental
conditions,
the real gas effects on shock wave/boundary layer interaction are
negligible. The
flat-plate similarity theory has been extended to include equilibrium
real gas effects.
While this theory is not applicable to the current experimental conditions,
it has been
employed here to determine the potential maximum effect of real gas behaviour. For
the flat plate, only small differences between perfect gas and equilibrium gas flows
are predicted, consistent with experimental observations. For the compression corner,
a more rapid rise to the maximum pressure and heat transfer on the ramp face is
predicted in the real gas flows, with the pressure lying slightly
below, and the heat
transfer slightly above, the perfect gas prediction. The increase in
peak heat transfer
is attributed to the reduction in boundary layer displacement thickness due to real
gas effects.
Spatial numerical simulation of boundary layer

transition: effects of a spherical particle
Authors: SAIKI E. M. , BIRINGEN S.
Published: July 2002

In the present study, the effects of an isolated stationary

spherical particle on the transition process in a flat-plate boundary

layer are examined by a spatial direct numerical

simulation. The full three-dimensional time-dependent incompressible

Navier–Stokes

equations are integrated by a time-splitting method and discretized spatially
by a

high-order finite difference/spectral method. A virtual

boundary technique defining

the no-slip boundary of a sphere is implemented within the Cartesian geometry
of

the computational grid.

Two numerical simulations which consider the effects of the sphere on
the boundary

layer are presented. The subcritical Reynolds number case reveals the appearance

of hairpin vortices shed into the sphere wake which decay as they are convected

downstream. The initial interaction of the sphere and the boundary layer
produces a

three-dimensional isolated disturbance comprising a wave part and a transient
part.

The decaying transient part is convected downstream at the local mean velocity,
while

the wave part induces a decaying Tollmien–Schlichting wave in the
flow field.

In the second case, an increase in the Reynolds number results in a
wedge of

incipient turbulent flow downstream of the sphere. The development of the
wake of

the sphere is dominated by the appearance of an isolated disturbance which
rapidly

breaks down forming a structure resembling a turbulent spot. It is demonstrated
that

the transition induced by a sphere in the boundary layer is due to a mechanism

related to bypass transition.
A Lagrangian direct-interaction approximation

for homogeneous isotropic turbulence
Authors: KIDA SHIGEO , GOTO SUSUMU
Published: July 2002

A set of integro-differential equations in the Lagrangian

renormalized approximation

(Kaneda 1981) is rederived by applying a perturbation method developed
by Kraichnan

(1959), which is based upon an extraction of direct interactions among
Fourier

modes of a velocity field and was applied to the Eulerian velocity correlation
and

response functions, to the Lagrangian ones for homogeneous isotropic turbulence.
The

resultant set of integro-differential equations for these functions has
no adjustable

free parameters. The shape of the energy spectrum function is determined
numerically

in the universal range for stationary turbulence, and in the whole wavenumber
range

in a similarly evolving form for the freely decaying case. The energy spectrum
in

the universal range takes the same shape in both cases, which also agrees
excellently

with many measurements of various kinds of real turbulence as well as numerical

results obtained by Gotoh et al. (1988) for a decaying

case as an initial value problem.

The skewness factor of the longitudinal velocity derivative is calculated
to be

−0.66 for stationary turbulence. The wavenumber dependence of the
eddy

viscosity is also determined.
The measurement of the shear-induced particle
and fluid tracer diffusivities in concentrated
suspensions by a novel method
Authors: BREEDVELD VICTOR , VAN DEN ENDE DIRK , TRIPATHI ANUBHAV , ACRIVOS ANDREAS
Published: July 2002

The shear-induced particle self-diffusivity in a concentrated suspension
(20%–50%
solids volume fraction) of non-colloidal spheres (90 μm average diameter)
was
measured using a new correlation technique. This method is based on the
correlation
between the positions of tracer particles in successive images and can
be used to
determine the self-diffusivity in non-colloidal suspensions for different
time scales.
These self-diffusivities were measured in the velocity gradient and vorticity
directions
in a narrow-gap Couette device for values of the strain γΔt

ranging from 0.05 to 0.5,
where γ is the applied shear rate and Δt is the
correlation time. In both directions, the
diffusive displacements scaled linearly with γΔt
over the range given above and the
corresponding diffusivities were found to be in good agreement with the
experimental
results of Leighton & Acrivos (1987a) and of Phan & Leighton (1993),
even though
these earlier studies were performed at much larger values of
γΔt. The self-diffusivity
in the velocity gradient direction was found to be about 1.7 times larger
than in
the vorticity direction. The technique was also used to determine the shear-induced

fluid tracer by measuring the mean square displacement of 31.5 μm diameter
tracer
particles dispersed in concentrated suspensions (30%–50% solids volume
fraction) of
much larger spheres (325 μm average diameter). These fluid diffusivities
were found
to be 0.7 times the corresponding particle diffusivities when both were
scaled with
γ a2 (2a = 325 μm).
Sound generation by shock–vortex interactions
Authors: INOUE OSAMU , HATTORI YUJI
Published: July 2002

Two-dimensional, unsteady, compressible flow fields produced by
the interactions
between a single vortex or a pair of vortices and a shock wave are simulated

numerically. The Navier–Stokes equations are solved by a finite difference
method.
The sixth-order-accurate compact Padé scheme is used for spatial
derivatives, together
with the fourth-order-accurate Runge–Kutta scheme for time integration.
The detailed
mechanics of the flow fields at an early stage of the interactions and
the basic nature
of the near-field sound generated by the interactions are studied. The
results for both
a single vortex and a pair of vortices suggest that the generation and
the nature of
sounds are closely related to the generation of reflected shock waves.
The flow field
differs significantly when the pair of vortices moves in the same direction
as the shock
wave than when opposite to it.
Deformation of liquid capsules enclosed by
elastic membranes in simple shear flow: large
deformations and the effect of fluid viscosities
Authors: RAMANUJAN S. , POZRIKIDIS C.
Published: July 2002

The deformation of a liquid capsule enclosed by an elastic membrane
in an infinite
simple shear flow is studied numerically at vanishing Reynolds numbers
using a
boundary-element method. The surface of the capsule is discretized into
quadratic
triangular elements that form an evolving unstructured grid. The elastic
membrane
tensions are expressed in terms of the surface deformation gradient, which
is evaluated
from the position of the grid points. Compared to an earlier formulation
that
uses global curvilinear coordinates, the triangular-element formulation
suppresses
numerical instabilities due to uneven discretization and thus enables the
study of large
deformations and the investigation of the effect of fluid viscosities.
Computations are
performed for capsules with spherical, spheroidal, and discoidal unstressed
shapes
over an extended range of the dimensionless shear rate and for a broad
range of the
ratio of the internal to surrounding fluid viscosities. Results for small
deformations of
spherical capsules are in quantitative agreement with the predictions of
perturbation
theories. Results for large deformations of spherical capsules and deformations
of
non-spherical capsules are in qualitative agreement with experimental observations
of
synthetic capsules and red blood cells. We find that initially spherical
capsules deform
into steady elongated shapes whose aspect ratios increase with the magnitude
of the
shear rate. A critical shear rate above which capsules exhibit continuous
elongation is
not observed for any value of the viscosity ratio. This behaviour contrasts
with that
of liquid drops with uniform surface tension and with that of axisymmetric
capsules
subject to a stagnation-point flow. When the shear rate is sufficiently
high and the
viscosity ratio is sufficiently low, liquid drops exhibit continuous elongation
leading
to breakup. Axisymmetric capsules deform into thinning needles at sufficiently
high
rates of elongation, independent of the fluid viscosities. In the case
of capsules in
shear flow, large elastic tensions develop at large deformations and prevent
continued
elongation, stressing the importance of the vorticity of the incident flow.
The long-time
behaviour of deformed capsules depends strongly on the unstressed shape.
Oblate
capsules exhibit unsteady motions including oscillation about a mean configuration

at low viscosity ratios and continuous rotation accompanied by periodic
deformation
at high viscosity ratios. The viscosity ratio at which the transition from
oscillations
to tumbling occurs decreases with the sphericity of the unstressed shape.
Results on
the effective rheological properties of dilute suspensions confirm a non-Newtonian

shear-thinning behaviour.
WKB theory for rapid distortion of
inhomogeneous turbulence
Authors: NAZARENKO S. , KEVLAHAN N. K.-R. , DUBRULLE B.
Published: July 2002

A WKB method is used to extend RDT (rapid distortion theory) to initially inhomogeneous
turbulence and unsteady mean flows. The WKB equations describe turbulence
wavepackets which are transported by the mean velocity and have wavenumbers
which evolve due to the mean strain. The turbulence also modifies the mean flow and
generates large-scale vorticity via the averaged Reynolds stress tensor. The theory is
applied to Taylor's four-roller flow in order to explain the experimentally observed
reduction in the mean strain. The strain reduction occurs due to the formation of a
large-scale vortex quadrupole structure from the turbulent spot confined by the four
rollers. Both turbulence inhomogeneity and three-dimensionality are shown to be
important for this effect. If the initially isotropic turbulence is either homogeneous in
space or two-dimensional, it has no effect on the large-scale strain. Furthermore, the
turbulent kinetic energy is conserved in the two-dimensional case, which has important
consequences for the theory of two-dimensional turbulence. The analytical and
numerical results presented here are in good qualitative agreement with experiment.
The elliptic whistler jet
Authors: HUSAIN HYDER S. , HUSSAIN FAZLE
Published: July 2002

Elliptic jets have decided advantages for technological applications over circular jets;
this paper explores further advantages achieved by jet forcing due to self-excitation.
Using hot-wire measurements and flow visualization, we have studied an elliptic
whistler (i.e. self-excited) air jet of 2:1 aspect ratio which, in contrast to an elliptic jet
issuing from a contoured nozzle, displays no axis switching, but significantly increased
spread in the major-axis plane. Its near-field mass entrainment is considerably higher
(by as much as 70%) than that of a non-whistling jet. Flow visualization reveals
unexpected dynamics of the elliptic vortical structures in the whistler jet compared to
that in the non-whistling jet. Vortices rolled up from the lip of the elliptic pipe impinge
onto the collar, producing secondary vortices; interaction of these two opposite-signed
vortices is shown to cause the different behaviour of the whistler jet.
Non-similarity solutions to the corner
boundary-layer equations
(and the effects of wall transpiration)
Authors: DUCK PETER W. , STOW SIMON R. , DHANAK MANHAR R.
Published: July 2002

The incompressible boundary layer in the corner formed by two intersecting, semi-infinite planes is investigated, when the free-stream flow, aligned with the corner,
is taken to be of the form U∞F(x), x
representing the non-dimensional streamwise
distance from the leading edge. In Dhanak & Duck (1997) similarity solutions for
F(x) = xn were considered, and it was found that solutions exist for only a range
of values of n, whilst for ∞ > n > −0.018, approximately, two
solutions exist. In this paper, we extend the work of Dhanak & Duck to the case
of non-90° corner angles and allow for streamwise development of solutions. In addition,
the effect of transpiration at the walls of the corner is investigated. The governing equations
are of boundary-layer type and as such are parabolic in nature. Crucially, although the
leading-order pressure term is known a priori, the third-order pressure term is not,
but this is nonetheless present in the leading-order governing equations, together with
the transverse and crossflow viscous terms.

Particular attention is paid to flows which develop spatially from similarity solutions.
It turns out that two scenarios are possible. In some cases the problem may
be treated in the usual parabolic sense, with standard numerical marching procedures
being entirely appropriate. In other cases standard marching procedures lead
to numerically inconsistent solutions. The source of this difficulty is linked to the
existence of eigensolutions emanating from the leading edge (which are not present in
flows appropriate to the first scenario), analogous to those found in the computation
of some two-dimensional hypersonic boundary layers (Neiland 1970; Mikhailov et
al. 1971; Brown & Stewartson 1975). In order to circumvent this difficulty, a different
numerical solution strategy is adopted, based on a global Newton iteration
procedure.

A number of numerical solutions for the entire corner flow region are presented.
Onset of plume convection in mushy layers
Authors: CHUNG C. A. , CHEN FALIN
Published: July 2002

A weakly nonlinear analysis is employed to investigate the onset of plume convection
in the mushy layer of a binary solution directionally solidified from below.
An improved mathematical model including the constant pressure condition at the
melt/mush interface is applied to analytically analyse the nonlinear behaviour of
the convection. Results show that, due to the consideration of the constant pressure
condition at the interface, the present analytical results are much better in comparison
with the experiments than those obtained by previous studies, in which the
no-vertical-flow condition at the interface was considered. It is also shown that the
bifurcation to three-dimensional hexagon convection, corresponding to the onset of
plume convection, is subcritical. For the case of small concentration ratio
[Cscr ] (equation (5b)) the channel of the plume is generated at
the top of the mush and grows downwards into the mush. For the case of large
[Cscr ], the channel may be generated
at the interior of the mush and grow upwards to the top of the mush. The possible
parameter regime in which the flow is of a stable down-centre hexagon is discussed.
The role of dissipation and mixing in exchange
flow through a contracting channel
Authors: WINTERS KRAIG B. , SEIM HARVEY E.
Published: July 2002

We investigate the transport of mass and momentum between layers in idealized
exchange flow through a contracting channel. Lock-exchange initial value problems
are run to approximately steady state using a three-dimensional, non-hydrostatic
numerical model. The numerical model resolves the large-scale exchange flow and
shear instabilities that form at the interface, parameterizing the effects of subgrid-scale turbulence. The closure scheme is based on an assumed steady, local balance of
turbulent production and dissipation in a density-stratified fluid.

The simulated flows are analysed using a two-layer decomposition and compared
with predictions from two-layer hydraulic theory. Inter-layer transport leads to a
systematic deviation of the simulated maximal exchange flows from predictions. Relative
to predictions, the observed flows exhibit lower Froude numbers, larger transports
and wider regions of subcritical flow in the contraction. To describe entrainment
and mixing between layers, the computed solutions are decomposed into a three-layer
structure, with two bounding layers separated by an interfacial layer of finite thickness
and variable properties. Both bounding layers lose fluid to the interfacial layer which
carries a significant fraction of the horizontal transport. Entrainment is greatest from
the faster moving layer, occurring preferentially downstream of the contraction.

Bottom friction exerts a drag on the lower layer, fundamentally altering the overall
dynamics of the exchange. An example where bed friction leads to a submaximal
exchange is discussed. The external forcing required to sustain a net transport is
significantly less than predicted in the absence of bottom stresses.
Technocrats and politicians in an authoritarian regime. The ‘ODEPLAN
Boys’ and the ‘Gremialists’ in Pinochet's Chile
Authors: HUNEEUS CARLOS
Published: July 2002

This article analyses the role of the economic team known as the
‘Chicago Boys’ and of the main political faction in Pinochet's Chile, the
‘Gremialists’, founded by Jaime Guzmán in the Catholic University in 1966.
These two sectors of the elite had a common professional and political career and
were the principal civilian groups of the dictatorship who developed a long-term
political strategy that deeply influenced both the economic and political
orientation of the military regime. They shared a long-term power strategy, that
was basically defined by the ‘Gremialists’. The article focuses on the role played
by ODEPLAN in shaping the economic reforms. It demonstrates that the
coherence of the economic model inherent in the implementation of its policies
is to be found in the integration of the policies with a political project, articulated
by the ‘Gremialists’.

I want to make it clear that I am convinced that the main responsibility for all
that is going on in Chile lies not with the military, but rather with the civilian
advisors and the whole climate of adulation and servilism that the economic
right has created around them, The ideology of the government was born in
the most traditional circles of the economic right, disguised under the sign of
‘nationalism’ and shielded behind ‘the courage to declare oneself anti-
Marxist’.
Preservation and minimality in loanword adaptation
Authors: PARADIS CAROLE , LACHARITÉ DARLENE
Published: July 2002

Attractive as might seem the challenge to build a process or performance

model that can account for every behavioural decision, there are a number

of sound reasons to tackle first the still difficult (but hopefully manageable)

task of developing a competence model; of trying to find the underlying

system that informs and constrains (if it doesn't always actually
govern)

choice. (Spolsky 1988: 105)

This article aims at showing the predictability of phonological adaptation,

segment

preservation and deletion in borrowings. It is shown that ill-formed segments
are

preserved and adapted in the vast majority of cases; segment deletion occurs
only

when an ill-formed segment is embedded within a higher level ill-formed
structure,

such as the syllable. This conclusion is based on the study of 15,686 segmental
and

syllabic malformations found in 11,348 loanword forms from five different
corpora

of loanwords. The analysis, which is set within the Theory of Constraints
and Repair

Strategies, is illustrated with the data from a corpus of 545 French loanwords

in Fula.
A Curse from God? Religious and political dimensions of the post-1991 rise of ethnic violence in South Sudan
Authors: Hutchinson Sharon E.
Published: July 2002

Southern Sudanese civilian populations have been trapped in a rising tide of ethnicised, South-on-South, military violence ever since leadership struggles within the main southern opposition movement – the Sudan People's Liberation Army (SPLA) – split into two warring factions in August 1991. This paper traces the devastating impact of this violence on a particularly volatile and fractured region of contemporary South Sudan: the oil rich heartlands of the Western Upper Nile Province. Foregrounding the historical experiences and grassroots perspectives of Nuer civilian populations in this region, the paper shows how elite competition within the southern military has combined with the political machinations of the national Islamic government in Khartoum to create a wave of inter- and intra-ethnic factional fighting so intense and intractable that many Nuer civilians have come to define it as ‘a curse from God’. Dividing Sudan's seventeen-year-long civil war (1983–present) into four distinct phases, the paper shows how successive forms and patterns of political violence in this region have provoked radical reassessments of the precipitating agents and ultimate meaning of this war on the part of an increasingly demoralised and impoverished Nuer civilian population.
Temperature-dependent physiological responses of the dogwhelk Nucella lapillus to cadmium exposure
Authors: Leung Kenneth M.Y. , Taylor Alan C. , Furness Robert W.
Published: July 2002

The combined effects of cadmium (Cd) and temperature on the physiology (oxygen consumption rate (MO2)) and biochemistry (glycogen, metallothionein (MT) and Cd concentrations) of fasted dogwhelks Nucella lapillus were investigated using two Cd concentrations (<0.01 or 500 μg l−1) and two water temperatures (5 or 10°C). After 20 days of exposure, the MO2 of dogwhelks of various sizes (12—32 mm in shell length) were measured individually. Dogwhelks exposed to Cd exhibited significantly lower MO2 at 10°C but not at 5°C when compared with controls at the same temperature. Inhibition of MO2 by Cd increased with increasing water temperature and decreasing animal size. Cadmium exposure caused significant reductions in glycogen concentrations in foot muscle and digestive gland at both temperatures. Cadmium-exposed dogwhelks showed significantly higher MT concentrations in the Leiblein gland at 10°C but not at 5°C, indicating that MT synthesis is temperature dependent and temperature is an important factor affecting toxicity of Cd in N. lapillus. Activity of dogwhelks and oxygen carrying capacity of the haemolymph, were significantly reduced as a result of Cd-exposure at 10°C. In addition, mucus secretion and necrotic cells were observed on the gill surface of Cd-exposed individuals. Therefore, reduction in MO2 may be directly linked to Cd-induced mucus production, structural damage to gills and reduction in oxygen carrying capacity of haemocyanin. However, metabolic depression, including low MO2 and activity, in Cd-exposed N. lapillus may be a strategy to: (i) minimize the uptake and toxicity of Cd; and (ii) minimize energy expenditure to spare energy reserves for detoxification (e.g. MT synthesis) and maintenance (e.g. repair of cellular damage). The results are discussed with reference to the use of MT and glycogen as biomarkers for metal exposure and toxicity in marine molluscs.
A new bathyal amphipod from the Bay of Biscay: Carangolia barnardi sp. nov. (Gammaridea: Urothoidae)
Authors: Jaume D. , Sorbe J.-C.
Published: July 2002

A new species of the cold-temperate austral amphipod genus Carangolia (Gammaridea: Urothoidae) is described from bathyal depths of the Bay of Biscay (north-east Atlantic). It was occasionally sampled in the south-eastern part of the Bay with sledges towed over muddy bottoms between 522 and 924 m water depth. This depth range falls mainly below the mud-line where the proportion of organic carbon increases in response to the deposition of silts and/or clay sediment. Most specimens were sampled by the lower net of the sledges, indicating a close association with the bottom. Abundance was relatively low, ranging between 0·18 and 4·90 ind 100 m−2, latter recorded below 700 m depth. The unusual massive appearance of Carangolia mandibles and its preference for bathyal foraminiferal oozes suggest that it is a specialized foraminifer consumer. The antitropical distribution pattern currently displayed by the genus could be an artefact due to equatorial submergence.