Effects Of Geometry Factors Research Articles

Effects of geometry factors on microvortices evolution in confined square microcavities

Recently, microcavities have become a central feature of diverse microfluidic devices for many biological applications. Thus, the flow and transport phenomena in microcavities characterized by microvortices have received increasing research attention. It is important to understand thoroughly the geometry factors on the flow behaviors in microcavities. In an effort to provide a design guideline for optimizing the microcavity configuration and better utilizing microvortices for different applications, we investigated quantitatively the liquid flow characteristics in different square microcavities located on one side of a main straight microchannel by using both microparticle image velocimetry (micro-PIV) and numerical simulation. The influences of the inlet Reynolds numbers (with relatively wider values Re = 1–400) and the hydraulic diameter of the main microchannel (DH = 100, 133 μm) on the evolution of microvortices in different square microcavities (100, 200, 400 and 800 μm) were studied. The evolution and characteristic of the microvortices were investigated in detail. Moreover, the critical Reynolds numbers for the emergence of microvortices and the transformation of flow patterns in different microcavities were determined. The results will provide a useful guideline for the design of microcavity-featured microfluidic devices and their applications.

Effect of geometry factors on the priority of σ-hole⋯π and π-hole⋯π bond in phosphorescent cocrystals formed by pyrene or phenanthrene and trihaloperfluorobenzenes

The effect of geometric factors on the assembly of luminescent cocrystals between pyrene or phenanthrene and trihaloperfluorobenzenes.

Effects of Wall-Injection Length on Spray and Combustion in a Coaxial Porous Injector

The mixing performance of an injector determines the combustion performance of a bipropellant rocket engine. In the previous study, a novel coaxial porous injector concept was developed to improve the mixing performance of a shear coaxial injector. It demonstrated a higher characteristic velocity efficiency than that of a typical shear coaxial injector. To clarify the efficiency-improving mechanism of a coaxial porous injector, the combustion flowfields of both injectors were visualized using a high-speed shadowgraph technique. The effect of geometry factors on the spray core length and the combustion performance as well as the differences in the reactive spray behavior between the coaxial porous injector and the shear coaxial injector were observed. The coaxial porous injector with a different wall-injection length showed higher characteristic velocity efficiencies, shorter spray core lengths, and thicker phase-change patterns at the spray core boundary. Changes in wall-injection length had a nonmonotonic effect on both the spray core length and the characteristic velocity efficiency. As opposed to the expected results, the coaxial porous injector with the highest combustion efficiency showed the longest spray core length. The phase-change pattern width, caused by the evaporation of liquid fuel droplets, was proportional to the efficiency.

The effect of geometry factors on fenestration energy performance and energy savings in office buildings

Although there have been multiple studies on window thermal properties in energy-efficient fenestration design, the effects of building geometry factors have been studied much less. The study presented in this paper evaluated the role of geometry factors, such as window orientation, window to wall ratio, and room width to depth ratio, on building energy performance in a commercial office building. A series of energy simulations were performed for six climate zones in the United States using a model of a room in a typical office building created in Design Builder, an energy analysis program, to evaluate total annual energy consumption. The simulation results were analyzed to find the combination of parameters yielding the lowest energy consumption and to define potential energy savings for office buildings located in various climate zones. The study showed that geometry factors affect energy consumption significantly in hot climates (Zones 2 and 3) and cold climates (Zones 6 and 7) but only marginally in temperate climates (Zones 4 and 5). Energy savings were on average 3% and 6% reaching a maximum of 10% and 14% in hot climates (Zones 2 and 3) and 1% in temperate and cold climates (Zones 4–7).

Effect of Geometry Factors on Dynamic Fracture Behavior for Mechanical Heterogeneous Welded Joint

Welded joint is a mechanical heterogeneous body, which is composed of base metal, weld metal and heat affected zone (HAZ). Many welded structures endure dynamic load in service. Mechanical heterogeneity has important influence on dynamic fracture behaviour of welded joint. In the present investigation, dynamic fracture parameter of J-integral of undermatched three-point-bending (TPB) welded joint specimens containing longitudinal crack with different geometry were computed. The strain rate near crack tip reaches 103 under the impact velocity of 5m/s, so dynamic properties under corresponding strain rate should be used in dynamic analysis. The results of instrumented impact experiment were used as the input parameters in the computation. Dynamic J-integral was evaluated using virtual crack extension (VCE) method of MARC finite element code in 3-D condition. Dynamic J-integral evaluated by VCE method is path independent. The value of dynamic J-integral curve increases with loading time smoothly, so inertia force has little influence on dynamic J-integral. The values of dynamic J-integral decrease with increase of weld width. When the weld width is bigger than 5mm the influence of base material on weld metal is not evident. The influence of initial crack length on dynamic J-integral is complicate. The value of dynamic J-integral of the computation model with initial crack length of a/W=1/4 is the highest, and that of the computation model with initial crack length of a/W=1/8 is the lowest. The results are helpful for dynamic fracture evaluation of macro-heterogeneous welded joints.

Design free of stress singularities for bi-material components

The disappearance of a stress singularity near the apex in a bi-material interface is investigated based on an eigenvalue investigation in conjunction with finite element analysis. Contours of the combination of critical wedge angles, from which the disappearance conditions of the stress singularity can be found, are obtained. Emphasis is also placed on how to apply these conditions to design components or specimens. Finite element analysis of various joint geometries with both normal and shear loadings is used to demonstrate the possible effects of geometry factors on the stress distributions along the interface. The focus of this paper is the problems associated with elimination of the stress singularities, with the goal of providing an approach for designing singularity-free bi-material joints.