Tracking single bubble in Hall-Héroult aluminium cell : an experimental and numerical study

In simulations of the hydrodynamics of the multiphase flow in gas– liquid systems with finite sizes of bubbles, the important thing is to compute explicitly the time evolution of the gas–liquid interface in many engineering applications. The most commonly used methods representing this approach are: the volume of fluid and the phase field methods. The later has gained significant interest because of its capability of performing numerical computations on a fixed Cartesian grid without having to parametrise these objects (Eulerian approach) and at the same time it allows to follow the interface ( for example bubble’s shape) that change the topology. In this paper, both numerical (phase field method) and experimental results for the bubble shapes underneath a downward facing plane is presented. Experiments are carried out to see the bubble sliding motion underneath a horizontal and inclined anode. It is assumed that the bubble formed under the anode surface is deformed (flattened) due to buoyant field before it goes around the anode corner. The bubble elongates to form a tail-like shape. The change in shape of the bubble is almost instantaneous and has a significant effect on the localised hydrodynamics around the bubble, which could influence the dynamics of the flow patterns in the Hall–Héroult cell. This deformation is the main cause of the bubble wake and the induced flow field in the aluminium cell. Various parameters such as bubble size, deformation and its sliding mechanism at different surface tensions are discussed and compared with experimental results

A new sterilization technique of bovine pericardial biomaterial using microwave radiation

Bioprosthetic valves created from chemically treated natural tissues such as bovine pericardial biomaterial are used as heart valve scaffolds. Methods currently available for sterilization of biomaterial for transplantation include the application of gamma radiation and chemical sterilants. These techniques, however, can be problematic because they can be expensive and lead to a reduction in tissue integrity. Therefore, improved techniques are needed that are cost effective and do not disrupt the physical properties, functionality, and lifespan of the valvular leaflets. This study examined a novel technique using nonthermalmicrowave radiation that could lead to the inactivation of bacteria in bovine pericardial biomaterial without compromising valve durability. Two common pathogenic species of bacteria, Escherichia coli and Staphylococcus aureus, were used as test microorganisms. Optimized microwave parameters were used to determine whether inactivation of pathogenic bacteria from bovine pericardium could be achieved. In addition, the effect of microwave sterilization on tissue integrity was examined. The mechanical properties (assessed using dynamic mechanical analysis) and tensile strength testing (using a Universal Tensile Tester) as well as thermal analysis (using thermogravimetric analysis and differential scanning calorimetry) indicated that microwave sterilization did not compromise the functionality of bovine pericardial biomaterial. Scanning electron microscopy imaging and cytotoxicity testing also confirmed that the structure and biocompatibility of transplant biomaterial remained unaltered after the sterilization process. Results from the application of this newmicrowave (MW) sterilization technique to bovine pericardium showed that nearcomplete inactivation of the contaminant bacteria was achieved. It is concluded that nonthermal inactivation of pathogenic bacteria from bovine pericardial biomaterial could be achieved using microwave radiation

Natural convection in domed porous enclosures : non-darcian flow

The natural-convection flow and associated heat transfer in a fluid-saturated porous medium have been investigated using the generalized porous medium approach for a dome-shaped enclosure. Many new features have been predicted with the connective heat transfer and the shape of the top dome cover. The solutions are obtained for a wide range of Darcy and Rayleigh numbers for different offsets and eccentricities of the top dome covers. The detailed parametric study reveals that there is a significant change in heat transfer rate when the offset is between 0.2 and 0.4. Different shapes of conic section, such as circular, elliptical, parabolic, and hyperbolic are used for the top dome cover, and their effects on natural convection and heat transfer rates are studied.<br /

Reviewer's commentary: tissue engineering of biological cardiovascular system surrogates

Abstract not available

Natural convection inside dome shaped enclosures

In the present paper the analysis of heat transfer and free convective motion have been carried out numerically for dome shaped enclosures. The solution method is based on the finite element technique with the frontal solver and is used to examine the flow parameters and the heat transfer characteristics inside dome shaped enclosures of various offsets. In formulating the solution a general conic equation is considered to represent the dome of circular, elliptical, parabolic and hyperbolic shapes. The numerical results indicate that the circular and elliptical shapes of dome give higher heat transfer rate and offset of the dome effects convective heat transfer quite significantly. However, beyond 0.3 top dome offset, the change in overall heat transfer rate is not significant. In addition, the convective phenomenon influenced by a dome shaped cover results in establishing a secondary core region even at a moderate Rayleigh number when compared with an equivalent rectangular enclosure. A good comparison between the present numerical predictions and the previous published data is achieved.<br /

Advances and trends in tissue engineering of teeth

Tooth loss due to several reasons affects most people adversely at some time in their lives. A biological tooth substitute, which could not only replace lost teeth but also restore their function, could be achieved by tissue engineering. Scaffolds required for this purpose, can be produced by the use of various techniques. Cells, which are to be seeded onto these scaffolds, can range from differentiated ones to stem cells both of dental and non-dental origin. This chapter deals with overcoming the drawbacks of the currently available tooth replacement techniques by tissue engineering, the success achieved in it at this stage and suggestion on the focus for future research

A pathway amongst undergraduate learning, postgraduate research and industrial involvement

The effectiveness of an industry-based experimental learning program for engineering undergraduate and postgraduate students at Swinburne University of Technology has been discussed and evaluated. The significance of this program lies in the fact that both types of students will see the relevance of learning and how it is implemented in industry-based problems whilst industry will gain engineering expertise in a specific field. The interaction amongst undergraduate students, postgraduate students, academia and industry personnel was found to be very productive to all parties involved and to the engineering profession in general

Numerical investigation of natural convection inside complex enclosures

In this article, the analyses of heat transfer and free convective motion have been carried out numerically for various structures. The solution is based on a finite element method with the frontal solver to examine the flow parameters and heat transfer characteristics. Several dome configurations--such as flat, inclined, and dome shapes--are considered for the top of the enclosure. A general conic equation is considered to represent the dome as circular, elliptical, parabolic, or hyperbolic shape. The findings from this study indicate that the convective phenomenon is greatly influenced by the shape of the top cover dome and tends to form a secondary core even at a moderate Rayleigh number when compared with an equivalent rectangular enclosure. In addition, the circular and elliptical shapes of the dome give higher heat transfer rate. The effect of various &quot;offset&quot; of the dome and inclined roof on convective heat transfer is also found to be quite significant. However, beyond 0.3 of offset of the top cover for the dome and inclined roof, the change in overall heat transfer rate is minimal. The heat transfer coefficients of dome shaped and inclined roof enclosures are given and discussed.<br /

A non-darcian numerical modeling in domed enclosures filled with heat-generating porous media

Numerical study of the natural-convection flow and heat transfer in a dome-shaped, heat-generating, porous enclosure is considered. The general conic equation for the top dome is used to consider various conical top sections such as circular, elliptical, parabolic, and hyperbolic. The individual effect of fluid Rayleigh, Darcy, and heat-generating parameters on flow patterns and heat transfer rates are analyzed and presented. The predicted results show that the heat-generating parameter has the most significant contribution toward the growth of bicellular core flow. Moreover, there is significant change in temperature distribution in comparison to rectangular enclosures, due to the existence of the domed-shape top adiabatic cover. The results also show that, regardless of Darcy and Rayleigh values, a flat adiabatic top cover tends to yield the highest value of Nusselt number, followed by circular, elliptical, parabolic, and hyperbolic top covers, respectively.<br /

A novel design of a polymeric aortic valve

Introduction: in this paper we propose a novel method for developing a polymeric heart valve that could potentially offer an optimum solution for a heart valve substitute. The valve design proposed will provide superior hydrodynamic performance and excellent structural integrity. A full description of the design process is given together with an analysis of the hemodynamic performance using a 2-way strongly coupled Fluid Structure Interaction (FSI). Method: a polymeric tri-leaflet heart valve is designed based on a patient's sinus of Valsalva (SOV) geometry. The design strategy aims to improve valve hemodynamic performance as well as valve durability by avoiding stress concentrations in the leaflets and reducing the maximum stress level. The valve dynamics and stress levels are also validated by comparing the predicted data to existing experimental and numerical data. Results: the stress distribution in the valve structure is fully characterized throughout the simulation and Von Mises stress is found to be up to 5.32 Mpa during diastole. The results show that an effective orifice area (EOA) and a pressure drop of 3.22 cm^2, and 3.52 mmHg, respectively, can be achieved using the proposed design. Conclusions: the optimized valve demonstrates high hemodynamic performance with no sign of damaging stress concentration in the entire cardiac cycle