The effect of nozzle geometry on the flow characteristics of small water jets

A wide variety of processes make use of plain orifice nozzles. Fuel injectors for internal combustion engines incorporate these nozzles to generate finely atomized sprays. Processes such as jet cutting, jet cleaning, and hydroentanglement, on the other hand, use similar nozzles, but require coherent jets. The spray or jet characteristics depend on the stability of the flow emerging from the orifice. This problem has been extensively researched for nozzles with diameters above 300 μm. Much less is known about the characteristics of jets produced by nozzles with smaller diameters, where viscous effects and small geometric variations due to manufacturing tolerances are likely to play an increasing role. Results are presented of a wide-ranging investigation of geometry effects on the flow parameters and jet characteristics of nozzles with diameters between 120 and 170 μm. Nozzles with circular cross-section and conical, cone-capillary and capillary axial designs were investigated. For conical and cone-capillary nozzles, the effect of cone angle and effects due to interactions between adjacent nozzles in the multi-hole cone-capillary nozzles were studied. For capillary nozzles, the effects of diameter variations and inlet edge roundness for capillary nozzles were considered. Furthermore, the effect of varying the aspect ratio (ratio of major and minor axes) of elliptical nozzles was studied. Flowrate and jet impact force measurements were carried out to determine the discharge coefficient C, velocity coefficient C, and contraction coefficient C of the nozzles for supply pressures between 3 and 12 MPa. Visualizations of the jet flow were carried out in the vicinity of the nozzle exit in order to identify near-nozzle flow regimes and to study jet coherence. The relationship between nozzle geometry, discharge characteristics, and jet coherence is examined. © IMechE 2006.

A “very limited” effect or a “seismic” impact? A study of the impact of the Human Rights Act 1998 on the Courts of Northern Ireland

This article focuses on the question of what impact the Human Rights Act 1998 has had in practice on the courts of Northern Ireland. How frequently are human rights arguments made in the course of cases in this jurisdiction, and to what extent do such arguments affect outcomes of cases? In order to assess the impact of the Act, the use of the European Convention on Human Rights in the Northern Irish courts during four periods of time is examined. These are, firstly, prior to the passing of the Act in November 1998; secondly, between the Act’s passing and its coming into force in October 2000; thirdly, the first three years after the coming into force of the Act (October 2000 until October 2003); and fourthly, the three years between October 2006 and October 2009.

Order without law? An anatomy of Hamas security: The Executive Force (Tanfithya)

In the struggle to assert and consolidate its power, the Hamas movement of the Palestinian territories has devised several strategies for control. In recognition that control of security remains a key goal for any power-seeker, following its election victory in January 2006, Hamas entered into a fierce and ultimately successful conflict with Fatah for control of the Palestinian Authority Ministry of Interior and Palestinian Security Forces (PSF) in the Gaza Strip. One way in which Hamas was able to achieve this objective was through the creation of its own internal ‘police’ force called the Tanfithya (Executive Force or EF). This article details an anatomy of the EF and the implications of this force in terms of Hamas' confrontation with opponents and its attempts at governance. It also examines the extent to which the EF can be considered to be a model of Islamic policing and its impact on secular rivals in the Gaza Strip.

Predicting low-velocity impact damage on a stiffened composite panel

An intralaminar damage model, based on a continuum damage mechanics approach, is presented to model the damage mechanisms occurring in carbon fibre composite structures incorporating fibre tensile and compressive breakage, matrix tensile and compressive fracture, and shear failure. The damage model, together with interface elements for capturing interlaminar failure, is implemented in a finite element package and used in a detailed finite element model to simulate the response of a stiffened composite panel to low-velocity impact. Contact algorithms and friction between delaminated plies were included, to better simulate the impact event. Analyses were executed on a high performance computer (HPC) cluster to reduce the actual time required for this detailed numerical analysis. Numerical results relating to the various observed interlaminar damage mechanisms, delamination initiation and propagation, as well as the model’s ability to capture post-impact permanent indentation in the panel are discussed. Very good agreement was achieved with experimentally obtained data of energy absorbed and impactor force versus time. The extent of damage predicted around the impact site also corresponded well with the damage detected by non destructive evaluation of the tested panel.

Exploring the impact of institutional and organizational factors on the reaction of MNCs to the global financial crisis

This paper analyses some of the factors that impact multinational companies' (MNCs) reaction to the global financial crisis. This paper reports the results from a large-scale study of its impact on MNCs in Australia, considering occurrences of site closures, offshoring, outsourcing, labour force reductions, reductions in working hours, salary reductions, and reductions in training and travel. Evidence showed that MNC reactions varied according to certain institutional and organizational effects. For example, MNCs originating from liberal-market economies are more likely to have offshored and outsourced production and reduced employment. The implications for understanding of MNC behaviour are discussed. © 2013 Copyright Taylor and Francis Group, LLC.

Cyclic nanoindentation and nano-impact fatigue characterisation of functionally graded TiN/TiNi shape memory film

This paper investigates the mechanism of nanoscale fatigue of functionally graded TiN/TiNi films using nano-impact and multiple-loading-cycle nanoindentation tests. The functionally graded films were deposited on silicon substrate, in which TiNi films maintain shape memory and pseudo elastic behavior, while a modified TiN surface layer provides tribological and anti-corrosion properties. Nanomechanical tests were performed to comprehend the localized film performance and failure modes of the functionally graded film using NanoTestTM equipped with Berkovich and conical indenter between 100 μN to 500 mN loads. The loading mechanism and load history are critical to define film failure modes (i.e. backward depth deviation) including the shape memory effect of the functionally graded layer. The results are sensitive to the applied load, loading type (e.g. semi-static, dynamic) and probe geometry. Based on indentation force-depth profiles, depth-time data and post-test surface observations of films, it is concluded that the shape of the nanoindenter is critical in inducing the localized indentation stress and film failure, including shape recovery at the lower load range. Elastic-plastic finite element (FE) simulation during nanoindentation loading indicated that the location of subsurface maximum stress near the interface influences the backward depth deviation type of film failure. A standalone, molecular dynamics simulation was performed with the help of a long range potential energy function to simulate the tensile test of TiN nanowire with two different aspect ratios to investigate the theory of its failure mechanism.

Numerical analysis of impact events in a centrifugal impact pin mill

Milling is an important operation in many industries, such as mining and pharmaceutical. Although the comminution process during milling has been extensively studied, the material fragmentation mechanisms in a mill are still not well understood partly because of the lack of an understanding on the local stressing and dynamic information under operational conditions in mills. This paper presents a DEM simulation of particle dynamics and impact events in a centrifugal impact pin mill. The main focus is the statistical characteristics of the dominant stressing modes during the milling process. The frequency, velocity and force of the different impact events between particles and mill components, or between particles, are analysed. © 2013 AIP Publishing LLC.

Dynamically mechanical and nano-impact (fatigue) analysis of touch screen thin films deposited on polyethylene terephthalate substrate

Nano-scale touch screen thin film have not been thoroughly investigated in terms of dynamic impact analysis under various strain rates. This research is focused on two different thin films, Zinc Oxide (ZnO) film and Indium Tin Oxide (ITO) film, deposited on Polyethylene Terephthalate (PET) substrate for the standard touch screen panels. Dynamic Mechanical Analysis (DMA) was performed on the ZnO film coated PET substrates. Nano-impact (fatigue) testing was performed on ITO film coated PET substrates. Other analysis includes hardness and the elastic modulus measurements, atomic force microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR) and the Scanning Electron Microscopy (SEM) of the film surface.
Ten delta of DMA is described as the ratio of loss modulus (viscous properties) and storage modulus (elastic properties) of the material and its peak against time identifies the glass transition temperature (Tg). Thus, in essence the Tg recognizes changes from glassy to rubber state of the material and for our sample ZnO film, Tg was found as 388.3 K. The DMA results also showed that the Ten delta curve for Tg increases monotonically in the viscoelastic state (before Tg) and decreases sharply in the rubber state (after Tg) until recrystallization of ZnO takes place. This led to an interpretation that enhanced ductility can be achieved by negating the strength of the material.
For the nano-impact testing using the ITO coated PET, the damage started with the crack initiation and propagation. The interpretation of the nano-impact results depended on the characteristics of the loading history. Under the nano-impact loading, the surface structure of ITO film suffered from several forms of failure damages that range from deformation to catastrophic failures. It is concluded that in such type of application, the films should have low residual stress to prevent deformation, good adhesive strength, durable and good resistance to wear.