Freshness and quality of fruits and vegetables as well as product saleable weight depend on heat and moisture transfer rate during air-cooling in the cool storages. The main objective of this study ...was to evaluate and develop a validated CFD model for predicting the temperature and velocity fields in a cold storage. In this study the air temperature, velocity, and non-uniform airflow in cold storage have been studied experimentally and numerically. Experimental and numerical models were employed to investigate cold storage's airflow field, flow pattern, and temperature field. The temperature and the velocity fields were measured in the cold storage filled with two potato pallets by using a hot wire anemometer and thermocouple with a programmable data logger computer. The experimental data was recorded at 60 points of temperature, and 27 points of velocity from three levels; high, middle, and bottom. Numerically the SB (Solid Block) technique was used to assess four turbulence models (Standard k-ε, Realizable k-ε, Standard k-ω, and SST k-ω) to compare with the experimental results for validation. The results of the validation were agreed with the experimental. The comparisons between the numerical results and experimental results revealed that the Shear Stress Transport (SST k-ω) model shows the best performance with the smallest absolute errors for temperature and velocity respectively. As well as the results revealed that the bottom and the top of the room was subjected to fresher and cooler air with relatively higher velocity. According to the study validation and finding, using the SST k-ω model is the best model for investigation in a cold storage, and for the improvement and evaluation of more complex cold storage, to achieve the balance distributions of air velocity, air temperature, and other heat transfer phenomena.
We have developed a comprehensive catalog of the variable differential rotation measured near the solar photosphere. This catalog includes measurements of these flows obtained using several ...techniques: direct Doppler, granule tracking, magnetic pattern tracking, global helioseismology, as well as both time-distance and ring-diagram methods of local helioseismology. We highlight historical differential rotation measurements to provide context, and thereafter provide a detailed comparison of the MDI-HMI-GONG-Mt. Wilson overlap period (April 2010 – Jan 2011) and investigate the differences between velocities obtained from different techniques and attempt to explain discrepancies. A comparison of the rotation rate obtained by magnetic pattern tracking with the rotation rates obtained using local and global helioseismic techniques shows that magnetic pattern tracking measurements correspond to helioseismic flows located at a depth of 25 to 28 Mm. In addition, we show the torsional oscillation from Sunspot Cycles 23 and 24 and discuss properties that are consistent across measurement techniques. We find that acceleration derived from torsional oscillation is a better indicator of long-term trends in torsional oscillation compared to the residual velocity magnitude. Finally, this analysis will pave the way toward understanding systematic effects associated with various flow measurement techniques and enable more accurate determination of the global patterns of flows and their regular and irregular variations.
Microturbulence (
ξ
) is a key parameter introduced in stellar spectroscopy to explain the strength of saturated lines by formally incorporating an additional thermal broadening term in the line ...opacity profile. Although our Sun can serve as an important testing bench to check the usual assumption of constant
ξ
, the detailed behavior of how
ξ
varies from the disk center through the limb seems to have never been investigated so far. In order to fill this gap, local
ξ
values on the solar disk were determined from the equivalent widths of 46 Fe
i
lines at 32 points from the center to the limb by requiring the consistency between the abundances derived from lines of various strengths. The run of
ξ
with
θ
(angle between the line of sight and the surface normal) was found to be only gradual from ≈ 1.0 km s
−1
(at
sin
θ
=
0
: disk center) to ≈ 1.3 km s
−1
(at
sin
θ
≈
0.7
: two-thirds of radial distance); but thereafter increasing more steeply up to ≈ 2 km s
−1
(at
sin
θ
=
0.97
: limb). This result further suggests that the microturbulence derived from the flux spectrum of the disk-integrated Sun is
≈
20
% larger than that of the disk-center value, which is almost consistent with the prediction from 3D hydrodynamical model atmospheres.
The methods for reducing the observations from the 150-foot tower telescope on Mt. Wilson are reviewed, and a new method for determining the poleward and rotational velocity deviations is described ...and applied. The flows we study are smaller than global and change with the solar cycle, so we describe them as poleward and rotational deviations rather than meridional circulation when we discuss solar surface flows. Due to a calibration problem with the data prior to 1983, only observations between 1983 and 2013 are presented at this time. After subtraction of latitude-dependent averages over the 30-year period of observation, the residual deviations in both the poleward and the rotational velocity are well synchronized and correspond to what is widely recognized as torsional oscillations. Both flow components need to be included in any model that replicates the torsional oscillations.
Abstract
Solar active regions (ARs) play a fundamental role in driving many of the geoeffective eruptions, which propagate into the solar system. However, we are still unable to consistently predict ...where and when ARs will occur across the solar disk by identifying preemergence signatures in observables such as the Doppler velocity (without using helioseismic methods). Here we aim to determine the earliest time at which preemergence signatures, the horizontal divergent flow (HDF) in particular, can be confidently detected using data from the Solar Dynamics Observatory’s Helioseismic and Magnetic Imager. Initially, we follow previous studies using the thresholding method, which searches for significant increases in the number of pixels that display a specific line-of-sight velocity. We expand this method to more velocity windows and conduct a basic parameter study investigating the effect of cadence on the inferred results. Our findings agree with previous studies with 37.5% of ARs displaying an HDF, with average lead times between the HDF and flux emergence of 58 minutes. We present a new potential signature of flux emergence, which manifests as cadence-independent transient disruptions to the amplitudes of multiple velocity windows and recover potential preemergence signatures for 10 of the 16 ARs studied, with lead times of 60–156 minutes. Several effects can influence both the estimated times of both HDF and flux emergence suggesting that one may need to combine Doppler and magnetic field data to get a reliable indicator of continued flux emergence.
Analog modeling of a flat-ramp-flat fault system was performed and its geometry and displacement field were compared to those of different kinematic models such as classical fault bend folding, fault ...parallel flow, incline-shear, curvilinear hinge, and backlimb trishear. To obtain the displacement vectors of the analog experiment, a Particle Image Velocimetry was performed. All analyzed kinematic models could explain the general configuration of the fault bend folding. However, only backlimb trishear could represent the geometry, directions of particle displacements, and relations between the displacements’ vectors. We propose in this paper that the combination of different asymmetry angles and different apical angles of the backlimb trishear model for each bend in a fault bend fold could be a very versatile and general kinematic model for simulating fault bend folds. Backlimb trishear apical angle can be used to control the shape of the hinges of a fold, while the asymmetry can be used to convolve the velocity of the particles above the fault. Both apical angle and asymmetries different from zero imply thickness changes. Fault bend folds with high inclination forelimbs can be reproduced with high positive asymmetries in the anticline bends of the fault.
•Analog model was performed to obtain the velocity field during deformation.•Documentation of velocity vectors comes from particle image velocimetry.•Backlimb trishear can represent the geometry and directions of particles velocities.•Steeper-dipping forelimbs can be reproduced using high positive asymmetries.•Backlimb trishear apical angle can be used to control the shape of the hinges.
A growing number of long-span bridges are under construction across straits or through valleys, where the wind characteristics are complex and inhomogeneous. The simulation of inhomogeneous random ...wind velocity fields on such long-span bridges with the spectral representation method will require significant computation resources due to the time-consuming issues associated with the Cholesky decomposition of the power spectrum density matrixes. In order to improve the efficiency of the decomposition, a novel and efficient formulation of the Cholesky decomposition, called “Band-Limited Cholesky decomposition,” is proposed and corresponding simulation schemes are suggested. The key idea is to convert the coherence matrixes into band matrixes whose decomposition requires less computational cost and storage. Subsequently, each decomposed coherence matrix is also a band matrix with high sparsity. As the zero-valued elements have no contribution to the simulation calculation, the proposed method is further expedited by limiting the calculation to the non-zero elements only. The proposed methods are data-driven ones, which can be applicable broadly for simulating many complicated large-scale random wind velocity fields, especially for the inhomogeneous ones. Through the data-driven strategies presented in the study, a numerical example involving inhomogeneous random wind velocity field simulation on a long-span bridge is performed. Compared to the traditional spectral representation method, the simulation results are with high accuracy and the entire simulation procedure is about 2.5 times faster by the proposed method for the simulation of one hundred wind velocity processes.
It is shown that the average meridional velocities of sunspot groups linearly depend on their average longitudinal velocities (solar rotation) with a high correlation coefficient of -0.95. The ...relationship differs for small, short-lived and large, long-lived groups. The meridional motions of sunspots do not have any pronounced global distribution law with latitude, but depend on their individual longitudinal velocities in a rotating coordinate system close to the Carrington one. The found relations indicate that the Coriolis force may play a role in driving the meridional motions of sunspot groups.
Fluid flows in an eight-strand tundish with tunnel filters have been investigated with physical modeling and mathematical simulation methods. This paper mainly studies the effect of tunnel filters ...install location and turning corner angle on the flow characteristics. In 1/3 scale tundish model experiments, RTD curves were used to study the flow characteristics in tundish with different configurations. The molten steel flow velocity and temperature fields were calculated by the commercial CFD package FLUENT. The result shows that tunnel filters play an important role in promoting flow characteristics. Suppose the tundish was divided into two regions by baffles, defined as sub-tundish a and sub-tundish b. The tunnel filters distinguished and enhanced the metallurgical function of each region, that is sub-tundish a is the inclusion collision and aggregation region and the main metallurgical function of sub-tundish b is uniform the temperature and remove large inclusions. The corner angle of tunnel filters has a great influence on the dead volume fraction, and the install location plays a key role in the assignment proportion of plug volume between sub-tundish a and sub-tundish b. By overall evaluation and contrast analysis, the tundish equipped with 120° tunnel filters long distance to the pouring point, was identified as the optimal tundish configuration. Industrial experiment verified the simulation results and had proved that the tundish with tunnel filters can effectively improve the removal efficiency of small inclusion(>5 µm).
We study large-scale subsurface flows associated with locations of high and low magnetic activity in the near-surface shear layer (NSSL). The flows were derived with ring-diagram analysis applied to
...Helioseismic and Magnetic Imager
(HMI) Dopplergrams using 30
∘
tiles. The zonal and meridional flows of the high- and low-activity subsets show the expected variation with the solar cycle with the low-activity subset showing flow precursors of cycle activity. We then focus on temporal averages of these flows. The average zonal flow of the high-activity subset is faster than that of the low-activity one at 0
∘
and 15
∘
, while they are about the same size at 30
∘
latitude. The amplitudes of the average meridional flow of the high-activity subset is smaller than those of the low-activity one at 30
∘
and comparable at 15
∘
latitude. The differences between the high- and low-activity subsets indicate the contribution of active regions to the flow pattern. The extra zonal flow of active regions increases with increasing depth, while the extra meridional flow converges near locations of activity. The converging flow is strongest at depths less than about 5 Mm, decreases with increasing depth, and is rather constant at depths greater than about 10 Mm. We then calculate the radial gradients of both flow components and find that those of the high-activity subset are generally more negative than those of the low-activity one. The extra radial gradients of active regions are about the same for both flow components, while the radial gradient of the zonal flow is about one order of magnitude larger than that of the meridional flow. Finally, we determine the radial extent of the NSSL using the radial gradient of the zonal flow and find that the NSSL extends to about 29 Mm at high-activity locations compared to 35 Mm at low-activity ones, or to about 83% of its depth at low-activity locations.
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