975 research outputs found
Influence of jet exit conditions on the passive scaler field of an axisymmetric free jet
The influence of initial flow conditions on the passive scalar field of a turbulent free jet issuing from the round nozzle is investigated in this paper by a review of the literature and a detailed experimental study. Two sets of distinctly different initial conditions are generated using two nozzle types: a smooth contraction and a long straight pipe. The present measurements of the passive scalar (temperature) field were conducted in a slightly heated air jet from each nozzle at a Reynolds number of 16 000 using identical experimental facilities and a single measurement technique. Significant differences between the flows from the two nozzles are revealed throughout the measured flow region which covers the axial range from 0 to 70 jet exit diameters. The study suggests that the differences observed in the statistics of the scalar field may be related to differences in the underlying turbulence structure of the jet in the near field. The present findings support the analytical result of George (1989) that the entire flow is influenced by the initial conditions, resulting in a variety of self-similar states in the far field.J. Mi, D. S. Nobes and G. J. Natha
Second Order Perturbation Theory for Improved Gluon and Staggered Quark Actions
We present the results of our perturbative calculations of the static quark
potential, small Wilson loops, the static quark self energy, and the mean link
in Landau gauge. These calculations are done for the one loop Symanzik improved
gluon action, and the improved staggered quark action.Comment: 3 pages, LaTeX, Lattice2001(improvement
Planar Doppler velocimetry measurements of flows using imaging fibre bundles
The development of a planar Doppler velocimetry is described. The technique is capable of measuring the three,
instantaneous components of velocity in two dimensions using a single pair of signal and reference cameras. PDV can
be used to measure the instantaneous 3-D velocity of a fluid by using an absorption line filter (ALF) to determine the
Doppler shifted frequency of a narrow line pulsed laser (Nd:YAG) that has been scattered off particles seeded into the
flow. The velocity of the fluid is determined using the Doppler formula and is dependent on the laser direction and the
viewing direction. Hence, only one velocity component of the flow is measured. This component can be measured in
two spatial dimensions using an array detector such as a CCD camera. To capture the three components, three such
measurement heads have been used viewing from different angles. In the technique presented here the three views are
ported from the collection optics to a single imaging plane using flexible fibre imaging bundles. These are made up of a
coherent array of single fibres and are combined at one end as the input plane to the measurement head. The paper
discusses the issues involved in developing a full three-dimensional velocity measurement system
Highly Improved Naive and Staggered Fermions
We present a new action for highly improved staggered fermions. We show that
perturbative calculations for the new action are well-behaved where those of
the conventional staggered action are badly behaved. We discuss the effects of
the new terms in controlling flavor mixing, and discuss the design of operators
for the action.Comment: Contribution to Lattice2001(improvement); 3 page
Visualization of Active Faulting using 3-D GPR Data Recorded Across the Alpine Fault, New Zealand
Three-dimensional (3-D) GPR data were acquired
across braided river sediments cut by the Alpine Fault at Calf
Paddock, New Zealand. We used 100 MHz antennas to obtain
images of the subsurface to a depth of 15 m. Cross-sections and
depth-converted time slices selected from the migrated data volume
show both the structural contrast generated by recent offsets
of the fault and the variable orientation of the dipping structures
within the braided river deposits. A trace-correlation technique is
used to generate dip and dip-direction attribute maps that allow us
to visualize the 3-D orientation of the dipping structures. The
attribute maps reveal at least 3 different reflection patterns and the
presence of minor faulting away from the main fault. A correlation-
based migration technique applied to a 2-D GPR profile resulted
in the successful identification of the main fault and subsidiary
faults at distances up to 50 m from the main fault
High-resolution geophysical surveying at the Springfield Fault, New Zealand
To trace the active Springfield Fault (South Island, New Zealand) and map its character at
shallow depths on a terrace where it exhibits no surface expression, we recorded 3-D georadar
data across an approximately rectangular 110 x 40 m survey area. In addition, we carried out
multi-electrode geoelectric measurements along a 198 m long profile that crossed the
georadar survey area. Although the georadar depth penetration was limited to only ~5 m, the
processed images revealed the presence of a prominent reflecting horizon disrupted by three
main discontinuities. Semi-continuous subhorizontal reflection patterns were interpreted to
represent sedimentary units within the fluvial deposits, whereas three detected discontinuities
were interpreted as fault traces with small near-vertical offsets (~0.4 m). This interpretation
was supported by vertical and lateral changes visible on the final inverted resistivity model
indicating lithological boundaries and fault branches
Leptonic decay constants f_Ds and f_D in three flavor lattice QCD
We determine the leptonic decay constants in three flavor unquenched lattice
QCD. We use O(a^2)-improved staggered light quarks and O(a)-improved charm
quarks in the Fermilab heavy quark formalism. Our preliminary results, based
upon an analysis at a single lattice spacing, are f_Ds = 263(+5-9)(+/-24) MeV
and f_D = 225(+11-13)(+/-21) MeV. In each case, the first reported error is
statistical while the is the combined systematic uncertainty.Comment: Talk presented at Lattice2004(heavy), Fermilab, June 21-26, 2004. 3
pages, 2 figure
Recent results from lattice calculations
Recent results from lattice QCD calculations relevant to particle physics
phenomenology are reviewed. They include the calculations of strong coupling
constant, quark masses, kaon matrix elements, and D and B meson matrix
elements. Special emphasis is on the recent progress in the simulations
including dynamical quarks.Comment: 13 pages, 8 figures, plenary talk at the 32nd International
Conference on High-Energy Physics (ICHEP 2004), August 16-22, 2004, Beijing,
Chin
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