Effect Of Geometrical Configuration Research Articles

Flow characteristics and micro—bubble behaviour in a rotating pipe section with an abrupt enlargement

The flow characteristics and dynamic behaviour of micro-bubbles were investigated experimentally and numerically for swirling flow within rotating pipe sections. In the present investigation, three types of rotating pipe section were used in order to study the effects of geometric configuration upon the flowfield. Experimental data were obtained for locations of the stagnation point and profiles of the parabolic surface. The results obtained from experiments were examined and verified with the aid of numerical analysis. It was found that the air pocket formed at the stagnation point was moved upstream by the effect of the suddenly expanded part when pipe rotation was increased. The reattachment point did not shift downstream as a result of an increase in the Reynolds number. This is due to the fact that the vortex zone at the expanded corner expands or shrinks, depending on the speed of rotation.

A novel approach to the design of complex heat transfer systems: portable computer design-a case study

The paper describes a novel approach to solving heat transfer problems in geometrically complex systems. In the present approach, instead of simulating the detailed complex geometry, templates of components and devices are assumed rather than working on actual components. By varying the template dimensions a systematic study on the effects of geometrical configurations on cooling airflow and heat transfer is made possible. The application of the approach is illustrated drawing examples from heat transfer analysis of portable computers. The purpose of the study is to develop a methodology whereby the packaging designer is freed from the task of performing detailed numerical analysis. Currently available numerical analysis tools such as computational fluid dynamics (CFD) codes are given a role in an undertaking to create databases from which fast design codes are developed.

Boundary integral equations for notch problems in an anisotropic half-space

A crack or a hole embedded in an anisotropic half-plane space subjected to a concentrated force at its surface is analyzed. Based on the Stroh formalism and the fundamental solutions to the half-plane solid due to point dislocations, the problem can be formulated by a system of boundary integral equations for the unknown dislocation densities defined on the crack or hole border. These integral equations are then reduced to algebraic equations by using the properties of the Chebyshev polynomials in conjunction with the appropriate transformations. Numerical results have been carried out for both crack problems and hole problems to elucidate the effect of geometric configurations on the stress intensity factors and the stress concentration.

Bearing Capacity Analysis of Rock Mass Taking Account of Contact Interaction Along Discontinuous Lines

A new stability analysis of rock mass is proposed by taking account of contact interaction along macroscopic discontinuous lines. The lower bound theorem in plasticity is employed with the finite element discretization technique. The joint element is introduced to describe the equilibrium equation in terms of stress in rock and contact traction along discontinuous line. The shearing behavior of joint as sliding and detachment is modeled as a rigid perfectly plastic one. The applicability of proposed method has been investigated in detail in comparison with the upper bound solutions by Tamura (1990). For every case, both computation results matched well indicating that both methods could be applicable to the stability estimation of a rock mass including macroscopic cracks inside. The ultimate bearing capacity of ground which includes discontinuous lines inside has been further assessed to investigate the effect of geometrical configuration and shearing property of discontinuous lines on the total stability. In particular, non-linear shearing property of discontinuous line against confining stress has been brought into the proposed method. The wide applicability of the proposed method to stability estimation of rock mass is clearly confirmed through some numerical studies.

Design and Fabrication of CFRP Interstage Attach Fitting for Launch Vehicles

Lattice structures that are made of carbon-fiber-reinforced plastics (CFRP) have been commonly used for interstage structures in launch vehicles because of their high axial compressive strength-to-weight ratio. The purpose of this research is to investigate the failure behavior of filament wound lattice structures to demonstrate that these structures can be fabricated and formed precisely and automatically. For the failure modes, the general buckling as a shell and excessive stress are considered. Various types of lattice shells under axial compressive loads are presented, and the optimal constraint with the highest compressive failure load is found. The main emphasis is placed on the effects of geometrical configuration of the structure and the manufacturing process. The main geometrical characteristics that affect failure are the winding pattern, winding angle, and the slenderness of the members. The primary advantage of a filament wound lattice structure is that fibers are wound continuously and aligne...

Effect of baffle geometries on crystal size distribution of aluminum potassium sulfate in a seeded batch crystallizer

Effects of geometrical configurations of crystallizers upon the crystal size distribution have been quantitatively investigated using four types of baffles with different geometries, in batch crystallization of aluminum potassium sulfate in a seeded batch crystallizer agitated by a 6-bladed flat paddle. Two evident maxima in size distribution were obtained for a vessel with normal wall baffles, whereas the maximum at larger size disappeared and only single maximum was observed for other types of vessels. The difference was infered to the difference in the ability of agglomeration of crystals depending the geometries.

Compressive Strength of Composite Lattice Structures

This research investigates the strength of composite lattice cylindrical and conical shells under axial compressive loads. The lattice structures are composed of circumferential and helical members, whose cross-sections are rectangular. The failure modes of both cylindrical and conical composite lattice shells are examined. New design constraints to achieve weight efficient structures with high failure loads is presented. Two main failure modes, general buckling as a shell and excessive shear stress in the members, are considered. The main emphasis is placed on the effects of geometrical configuration of the structure and the manufacturing process. Filament winding was used as the method of construction to automate the fabrication process and to minimize manufacturing costs. Numerical results are obtained by finite element analysis which are compared with experimental solutions. The motivation of the present work was to find the optimal winding pattern to which filament winding can be easily applied and still provide the highest strength to weight ratio. The final result of this research includes the numerical and experimental analysis of composite lattice cylindrical and conical shells via filament-winding. This work provides an understanding of composite lattice structures that will be useful in preliminary design of such structures.

A finite-element model of oxygen diffusion in the pulmonary capillaries.

We determined the overall pulmonary diffusing capacity (DL) and the diffusing capacities of the alveolar membrane (Dm) and the red blood cell (RBC) segments (De) of the diffusional pathway for O2 by using a two-dimensional finite-element model developed to represent the sheet-flow characteristics of pulmonary capillaries. An axisymmetric model was also considered to assess the effect of geometric configuration. Results showed the membrane segment contributing the major resistance, with the RBC segment resistance increasing as O2 saturation (SO2) rises during the RBC transit: RBC contributed 7% of the total resistance at the capillary inlet (SO2 = 75%) and 30% toward the capillary end (SO2 = 95%) for a 45% hematocrit (Hct). Both Dm and DL increased as the Hct increased but began approaching a plateau near an Hct of 35%, due to competition between RBCs for O2 influx. Both Dm and DL were found to be relatively insensitive (2-4%) to changes in plasma protein concentration (28-45%). Axisymmetric results showed similar trends for all Hct and protein concentrations but consistently overestimated the diffusing capacities (approximately 2.2 times), primarily because of an exaggerated air-tissue barrier surface area. The two-dimensional model correlated reasonably well with experimental data and can better represent the O2 uptake of the pulmonary capillary bed.

Influence of inlet and outlet configuration on the flow in secondary clarifiers

A numerical model for predicting the flow in clarifiers is presented which accounts for density-affected and turbulent flow as well as for the settling of activated sludge. The reliability of the two-dimensional model is demonstrated through verification by means of a laboratory experiment which was specially designed for this purpose. The numerical model is then applied for an evaluation of inlet and outlet arrangements. The inlet is positioned at the bottom and the inlet aperture is varied. An outlet at the top of the end wall is compared with outlets longitudinally extended at the surface. The alternatives are assessed by analysis of streamline patterns, layer charactersitics and the entrainment into the bottom current, i.e. the increase of its flow rate. The study demonstrates how numerical modelling can be used for systematic evaluation of the effect of geometrical configurations on the flow in secondary clarifiers.

Measurement of particle flow behavior in a pilot-plant multi-solid fluidized bed combustor by using suction probe technique.

Measurements of the solid mass fluxes and particle size distributions were made by using a suction probe in a pilot-plant Multi-Solid Fluidized Bed (MSFB) combustor. The focus of this paper is to understand the flow structure in a MSFB under combustion conditions and the effect of geometrical configuration of the combustion chamber on the internal flow structure and particle size distributions. This paper also presents the applicability of suction probe technique for measuring the particle flow behavior in a hot model MSFB. The measurement results on the radial solid mass fluxes and particle size distribution show that not only the radial solid mass fluxes but also the mean diameter of particle and radial distribution of coarse particles (i.e. large coal particles (>1 mm)) depend on the geometrical configuration of the combustion chamber. The suction probe technique is found to be successful in measuring solid mass fluxes and particle flow behavior under combustion conditions.

Influence of inlet and outlet configuration on the flow in secondary clarifiers

A numerical model for predicting the flow in clarifiers is presented which accounts for density-affected and turbulent flow as well as for the settling of activated sludge. The reliability of the two-dimensional model is demonstrated through verification by means of a laboratory experiment which was specially designed for this purpose. The numerical model is then applied for an evaluation of inlet and outlet arrangements. The inlet is positioned at the bottom and the inlet aperture is varied. An outlet at the top of the end wall is compared with outlets longitudinally extended at the surface. The alternatives are assessed by analysis of streamline patterns, layer characteristics and the entrainment into the bottom current, i.e. the increase of its flow rate. The study demonstrates how numerical modelling can be used for systematic evaluation of the effect of geometrical configurations on the flow in secondary clarifiers.

THERMALLY INDUCED STRESSES IN A TRILAYERED SYSTEM

The objective of this investigation is to conduct a parametric study of thermally induced stresses in trilayered media. In particular, the resulting shear and normal stresses along the media interfaces is analyzed. Because this investigation is concerned only with the failure at the bonding surfaces, the results of bending stresses, although calculated, are not presented. A finite element model utilizing a recently developed element that provides for both axial and lateral displacement continuity is employed. First, the effect of the material property, that is, coefficient of thermal expansion, is examined. Then the effect of geometric configuration, that is, the length and thickness dimensions of the midlayer, is analyzed. Finally, a study of the effect of a nonuniform temperature field on the trimaterial medium is conducted.

A STUDY OF MIXED GEOMETRICAL AND ROTATIONAL EFFECTS ON INTERNAL TURBULENT FLOW AND HEAT TRANSFER

A finite element method based investigation is carried out for the determination of three‐dimensional turbulent flow structures and heat transfer rates of cooling ducts within turbine blades which rotate about an axis orthogonal to their own axis of symmetry. The effects of geometrical configurations, Coriolis forces and coolant inertias on the hydrodynamic and thermal characteristics have been systematically predicted and compared with experimental measurements.

Development of an Intravascular Lung Assist Device

Intravascular lung assist devices (ILADs) must provide sufficient gas transport without excessive pressure drop. In vitro studies of fiber-bundle devices determined the effect of geometric configuration on gas transfer efficiency, the amount of surface area needed to achieve sufficient gas transport, and the relationship between gas transport and blood-side pressure drop. ILADs with cross-flow fibers transfer at least 10 times more O2 than parallel flow ILADs of the same surface area, and six to eight times more CO2. Some tested devices with 0.4–0.6 m2 of surface area can transfer 100 ml/min of both O2 and CO2. Configurations with high gas transport, however, often require moderate pressure drops.

Development of an intravascular lung assist device.

Intravascular lung assist devices (ILADs) must provide sufficient gas transport without excessive pressure drop. In vitro studies of fiber-bundle devices determined the effect of geometric configuration on gas transfer efficiency, the amount of surface area needed to achieve sufficient gas transport, and the relationship between gas transport and blood-side pressure drop. ILADs with cross-flow fibers transfer at least 10 times more O2 than parallel flow ILADs of the same surface area, and six to eight times more CO2. Some tested devices with 0.4-0.6 m2 of surface area can transfer 100 ml/min of both O2 and CO2. Configurations with high gas transport, however, often require moderate pressure drops.

Effects of Weld Configurations on Strain Field

Effects of geometrical configurations of welds on stress and strain distributions are investigated experimentally and theoretically. Three types of weld configurations are analyzed under axial and bending loads. Analyses by using a three-dimensional finite element method are performed, and the results are compared with the experimental ones with good accuracy. Stress and strain concentration factors are also investigated, and the applicability of Neuber’s equation is examined.

The effect of geometric configuration on the light transmission of greenhouses

A computer model was used to investigate the effects of geometric changes in greenhouse cross section on transmissivity. The effects of changing greenhouse wall height, roof height and roof configuration were studied for infinitely long houses and houses with different numbers of spans and types of cladding. Standard diffuse overcast and direct beam irradiances over the winter period only were considered. Results showed that under diffuse conditions, variations in irradiance for low wall heights are produced across multispan houses, and double glazing lowers the transmissivity by about 5%, which is less than expected from laboratory measurements. Under average light, large multispan houses with double glazing and a vertical south-facing roof provide comparable light transmissivity to conventional symmetric multispancs, and therefore offer significant reductions in operating costs. For houses with one or two spans, transmissivities can exceed 100%, and double glazing can enhance rather than reduce transmissivities.

Effect of geometrical configuration of square-planar metal complexes on their RF values obtained by paper chromatography

Effect of geometrical configuration of square-planar metal complexes on their RF values obtained by paper chromatography

Effects of geometric configuration and steric hindrance on rates and mechanisms of oxidation of diaminedichloroplatinum(II) complexes by tetrachloroaurate(III) ions

The oxidation reactions of trans- and/or cis-[PtCl2(NH2R)2] by [AuCI4]– in the presence of [NEt4]CI have been kinetically investigated in acetonitrile (R = H, Me, Et, Prn, Pri, Bun, Bui, Bus, But, CH2But, CH2Ph, or cyclo-C6H11). The rate law for the oxidation of the trans complexes consists mainly of a third-order rate term, kc[PtCl2(NH2R)2][AuCl4–][Cl–], whereas an additional rate term, ka[ PtCI2(NH2 R)2][AuCl4–][CI–]/(1 +kb[CI–]), operates in the case of the cis complexes. A reaction scheme is proposed. The oxidation rates of both cis and trans complexes appear to be reduced by increasing the steric hindrance of the amine, cis complexes being more sensitive towards changes of steric hindrance than traps analogues. Approximate linear relationships correlate the reactivities (log k) of both cis and trans complexes with an amine steric hindrance parameter.

Thermodynamic studies of protein-salt interaction. 2. Effects of geometrical configuration in alkyl-substituted quaternary ammonium salts on their interactions with phycocyanin

Thermodynamic studies of protein-salt interaction. 2. Effects of geometrical configuration in alkyl-substituted quaternary ammonium salts on their interactions with phycocyanin