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Flow patterns and cleaning behaviour of horizontal liquid jets impinging on angled walls
Liquid jets are widely used in cleaning operations in the food sector. Morison and Thorpe (2002) reported an experimental investigation of the flow patterns and cleaning behaviour of horizontal jets impinging on vertical walls. The Wilson et al. (2012) model, which described Morison and Thorpe's flow pattern data well, is extended to describe the flow pattern generated by a liquid jet, approaching a surface at a given angle to the horizontal, impinging on a plate inclined at a known angle to the vertical. The results are compared with experimental data collected for horizontal water jets impinging on inclined Perspex and glass plates. Tests employed nozzle diameters of 1, 2 and 3mm at room temperature, using flow rates of 0.78–2.23gs−1, 3.7–9.9gs−1 and 7.1–17.3gs−1 (0.025–0.062m3h−1) respectively. These are lower than industrial cleaning flow rates. The angle at which the horizontal jet impinged on the plate was varied from 30° to 120°. Two important dimensions are evaluated: (i) the width of the fast moving radial flow zone on the plate (the region bounded by the film jump, the feature similar to a hydraulic jump) at the plane of impingement; (ii) the distance on the plate to which the radial flow zone extends above the point of impingement. Both are described reasonably well by the model. Empirical relationships are reported for the width of the wetted region at the level of impingement, and the maximum width of the draining film. A short study of cleaning of layers of washable paint on glass, similar to the tests reported by Morison and Thorpe, show that the cleaning model recently developed by Wilson et al. (2014) gives a good description of the initial cleaning of such layers using an impinging stationary coherent water jet.A PhD scholarship for TW from Chengda Engineering Co. is gratefully acknowledged.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.fbp.2014.09.00
The effect of geometry parameters and flow characteristics on erosion and sedimentation in channels junction using finite volume method
One of the most critical problems in the river engineering field is scouring,
sedimentation and morphology of a river bed. In this paper, a finite volume
method FORTRAN code is provided and used. The code is able to model the
sedimentation. The flow and sediment were modeled at the interception of the
two channels. It is applied an experimental model to evaluate the results.
Regarding the numerical model, the effects of geometry parameters such as
proportion of secondary channel to main channel width and intersection angle
and also hydraulic conditionals like secondary to main channel discharge ratio
and inlet flow Froude number were studied on bed topographical and flow
pattern. The numerical results show that the maximum height of bed increased to
32 percent as the discharge ratio reaches to 51 percent, on average. It is
observed that the maximum height of sedimentation decreases by declining in
main channel to secondary channel Froude number ratio. On the assessment of the
channel width, velocity and final bed height variations have changed by given
trend, in all the ratios. Also, increasing in the intersection angle
accompanied by decreasing in flow velocity variations along the channel. The
pattern of velocity and topographical bed variations are also constant in any
studied angles
Recovering Solar Toroidal Field Dynamics From Sunspot Location Patterns
We analyze both Kitt Peak magnetogram data and MDI continuum intensity
sunspot data to search for the following solar toroidal band properties: width
in latitude and the existence of a tipping instability (longitudinal m=1 mode)
for any time during the solar cycle. To determine the extent which we can
recover the toroidal field dynamics, we forward model artificially generated
sunspot distributions from subsurface toroidal fields we assigned certain
properties. We analyzed two sunspot distribution parameters using MDI and model
data: the average latitudinal separation of sunspot pairs as a function of
longitudinal separation, and the number of sunspot pairs creating a given angle
with respect to the E-W direction. A toroidal band of 10 degrees width with a
constant tipping of 5 degrees best fits MDI data early in the solar cycle. A
toroidal band of 20 degrees width with a tipping amplitude decreasing in time
from 5 to 0 degrees best fits MDI data late in the solar cycle. Model data
generated by untipped toroidal bands cannot fit MDI high latitude data and can
fit only one parameter at low latitudes. Tipped toroidal bands satisfy chi
squared criteria at both high and low latitudes. We conclude this is evidence
to reject the null hypothesis - that toroidal bands in the solar tachocline do
not experience a tipping instability - in favor of the hypothesis that the
toroidal band experiences an m=1 tipping instability. Our finding that the band
widens from ~10 degrees early in the solar cycle to ~20 degrees late in the
solar cycle may be explained in theory by magnetic drag spreading the toroidal
band due to altered flow along the tipped field lines.Comment: This paper is accepted to Astrophysical Journal, September 2005 issu
Sonar acoustics
The problem of producing a model to determine the beam pattern produced by a sonar set in the form of a circular cylinder with hemispherical end caps is studied. The beam width and the position of the beam centre are also considered and the results of the models are compared with experimental findings. Possible reasons for the discrepancies between these theoretical and experimental results are examined, providing insight into developing more sophisticated mathematical models. The beam patterns were produced using a combination of Matlab and Fortran 77 programs incorporating subroutines from the NAG library. Experimental results and data are included with the kind permission of Thomson Marconi Sonar Systems Ltd
Getting the most out of a post-column EELS spectrometer on a TEM/STEM by optimising the optical coupling
Ray tracing is used to find improved set-ups of the projector system of a JEOL ARM 200CF TEM/STEM for use in coupling it to a Gatan 965 Quantum ER EELS system and to explain their performance. The system has a probe aberration corrector but no image corrector. With the latter, the problem would be more challenging. The agreement between the calculated performance and that found experimentally is excellent. At 200kV and using the 2.5mm Quantum entrance aperture, the energy range over which the collection angle changes by a maximum of 5% from that at zero loss has been increased from 1.2keV to 4.7keV. At lower accelerating voltages, these energy ranges are lower e.g. at 80kV they are 0.5keV and 2.0keV respectively. The key factors giving the improvement are an increase in the energy-loss at which the projector cross-over goes to infinity and a reduction of the combination aberrations that occur in a lens stack. As well as improving the energy-loss range, the new set-ups reduce spectrum artefacts and minimise the motion of the diffraction pattern at low STEM magnification for electrons that have lost energy. Even if making the pivot points conjugate with the film plane gives no motion for zero-loss electrons, there will be motion for those electrons that have lost energy, leading to a false sense of security when performing spectrum imaging at low magnifications. De-scanning of the probe after the objective lens is a better way of dealing with this problem
Dynamics of gravity driven three-dimensional thin films on hydrophilic-hydrophobic patterned substrates
We investigate numerically the dynamics of unstable gravity driven
three-dimensional thin liquid films on hydrophilic-hydrophobic patterned
substrates of longitudinal stripes and checkerboard arrangements. The thin film
can be guided preferentially on hydrophilic longitudinal stripes, while fingers
develop on adjacent hydrophobic stripes if their width is large enough. On
checkerboard patterns, the film fingering occurs on hydrophobic domains, while
lateral spreading is favoured on hydrophilic domains, providing a mechanism to
tune the growth rate of the film. By means of kinematical arguments, we
quantitatively predict the growth rate of the contact line on checkerboard
arrangements, providing a first step towards potential techniques that control
thin film growth in experimental setups.Comment: 30 pages, 12 figure
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