49,071 research outputs found
Effects of the complex mass distribution of dark matter halos on weak lensing cluster surveys
Gravitational lensing effects arise from the light ray deflection by all of
the mass distribution along the line of sight. It is then expected that weak
lensing cluster surveys can provide us true mass-selected cluster samples. With
numerical simulations, we analyze the correspondence between peaks in the
lensing convergence -map and dark matter halos. Particularly we
emphasize the difference between the peak value expected from a dark
matter halo modeled as an isolated and spherical one, which exhibits a
one-to-one correspondence with the halo mass at a given redshift, and that of
the associated -peak from simulations. For halos with the same expected
, their corresponding peak signals in the -map present a wide
dispersion. At an angular smoothing scale of , our
study shows that for relatively large clusters, the complex mass distribution
of individual clusters is the main reason for the dispersion. The projection
effect of uncorrelated structures does not play significant roles. The
triaxiality of dark matter halos accounts for a large part of the dispersion,
especially for the tail at high side. Thus lensing-selected clusters
are not really mass-selected. (abridged)Comment: ApJ accepte
SIMULATION STUDY ON WATERFLOOD FRONT: BLOCK HADE OF TARIM OILFIELD IN NORTHWEST CHINA
Block Hade consist of a deep thin sandstone reservoir of two sub-layer reservoirs. The thickness is
about 1.5 m for each layer. The two-layer âstaircaseâ horizontal well is used for recovery. In order
to determine water displacement front and edge water movement, tracer test is conducted in the
reservoir. But the cycle of field tracer monitoring is about 150-360 days. This prevented the efficient
monitoring of waterflood swept area and waterflood advance direction and velocity, after the cycle
of tracer monitoring. Conservation of mass with respect to tracer flow and history performance
matching of tracer enabled the study of water-flood front and edge-water advance. The simulation result
is basically consistent with the monitored field tracer results. Therefore, numerical model can be used to
conduct a longer monitoring period. It can make up for the disadvantage of the complexity of the
tracer monitoring setup, its implementation, and time-consuming monitoring cycle. The water-flood
front, water-flood swept area, advancing velocity and the predominant water injection direction can be
obtained. Furthermore, it is possible to evaluate and predict the injection-production well interaction and
can also provide a reliable basis to deploy reasonable flood patterns to enhance oil recovery
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Hydrodynamic Analysis of Binary Immiscible Metallurgical Flow in a Novel Mixing Process: Rheomixing
This paper presents a hydrodynamic analysis of binary immiscible metallurgical flow by a numerical simulation of the rheomixing process. The concept of multi-controll is proposed for classifying complex processes and identifying individual processes in an immiscible alloy system in order to perform simulations. A brief review of fabrication methods for immiscible alloys is given, and fluid flow aspects of a novel fabrication method â rheomixing by twin-screw extruder (TSE) are analysed. Fundamental hydrodynamic micro-mechanisms in a TSE are simulated by a piecewise linear (PLIC) volume-of-fluid (VOF) method coupled with the continuum surface force (CFS) algorithm. This revealed that continuous reorientation in the TSE process could produce fine droplets and the best mixing efficiency. It is verified that TSE is a better mixing device than single screw extruder (SSE) and can achieve finer droplets. Numerical results show good qualitative agreement with experimental results. It is concluded that rheomixing by a TSE can be successfully employed for casting immiscible engineering alloys due to its unique characteristics of reorientation and surface renewal
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