Vortex-Induced Vibration (VIV) is a possible phenomenon in situations where a bluff body interacts with a fluid flow. There are many potential areas where this phenomenon could be observed such as in heat exchanger tube bundles, marine structures, bridges, power transmission lines etc. Due to VIV, the structures could be subjected to very large transverse vibrations which may lead to their fatigue failure. Hence, controlling vortex-induced vibrations or if possible, suppressing them is of paramount importance in practical situations, particularly in a situation like marine deep water environment where the fault diagnosis and repair would be extremely difficult. This could be achieved by passive and active control means. In this paper, a review of the passive control of VIV through various means is presented particularly emphasizing some recent inventions patented in this area. The review indicates that, in practical applications especially in marine engineering situations, passive control measures such as employing a streamline fairing or a helical strake, prolong the life of offshore structures by protecting them from vortex-induced vibrations. The paper includes recent patents on this topic and concludes with a note on the current and future developments expected in the passive control of VIV.
In this paper, a numerical study on the structural behaviour of three-dimensional cracked structures have been presented. The stiffness matrix of the cracked element is found as the inverse of the compliance matrix. This matrix is given by the sum of the compliance matrix of the intact element and an additional compliance matrix which contains all the flexibilities given by the presence of the crack. The flexibilities are related to the stress intensity factors. A simple method for obtaining approximate stress intensity factors is applied. It takes into account the elastic crack tip stress singularity while using the elementary beam theory. Moreover, crack depth and location are modelled as random variables in order to take into account the unavoidable uncertainty that always affects damaged structures. A simple and accurate method for the probabilistic characterization of the linear elastic response of cracked structures with uncertain damage is employed. According to this method, the uncertainties are transformed into superimposed deformations depending on the distribution of internal forces and an iterative procedure is established to solve the resultant equations. Numerical tests evidence excellent accuracy for multicracked structures with large fluctuation of damage. Present manuscript also discusses relevant patents.
Over the past decade significant improvements have been made in wall shear stress (WSS) sensor technologies. Due to the need to resolve flow structures on the order of 100 μm at frequencies up to 10 kHz, classes of microelectromechanical (MEMS) sensors have been developed to overcome these limitations. Three main classes exist, including floating element, thermal, and optical MEMS flow sensors. A handful of new patents have been issued in all three of these classes. For floating element MEMS flow sensors recent US patents. For thermal MEMS flow sensor. Floating element sensors have the advantage that they provide a direct measurement, while thermal sensors use an empirical formulation based upon the heat transfer from the sensor to the flow. Floating element sensors suffer from error associated with pressure gradients, cross-axis sensitivity to acceleration and vibration inputs, and fabrication issues including misalignment between the floating element and gap, debris becoming trapped in the gap between the floating element and the sensor mount and a compromise between durability and sensitivity. Thermal sensors are more mature as they are based on well established methods; however, the major flaw with this technique is the difficulty associated with minimizing heat transfer between the sensing element and the substrate. The third class of sensors, optical MEMS flow sensors, are quickly emerging as perhaps the most accurate and reliable of the three techniques.
This paper reviews the recent development of displacement-based theories for laminated composite plates as well as corresponding finite element models. Discussion focuses on the accuracy and efficiency of various theories, and the detailed expression of typical displacement theories used herein is also presented. To objectively assess these theories, Paganos cylindrical bending problems are chosen for comparison of various theories. Numerical results show that the global-local theories are more suitable for prediction of transverse shear stresses directly from constitutive equations in comparison with other theories. However, the zig-zag theories satisfying the interlaminar continuity of transverse shear stresses are still unable to accurately predict transverse shear stresses directly from constitutive equations, in which in order to obtain satisfactory transverse shear stresses, 3D equilibrium equations have to be adopted. In addition, free vibrations and stability of soft-core sandwiches are also considered to further assess various displacementbased laminated plate theories. Numerical results show that the global displacement theories will encounter difficulties to accurately predict the dynamic and the buckling response of so special structures. However, the global-local theories satisfying the continuity of transverse shear stresses at interfaces are still suitable for the dynamic and the buckling problems of soft-core sandwiches. In addition, this paper also includes some information of recent patents on the processes for the fabrication of composite metal object as well as functionally graded materials, and the methods of making nanofibre yarns, ribbons and sheets et al.
The atomizer serves as an energy conversion mechanism to convert a volume of the liquid into a multiplicity of small droplets and then ejects these droplets so as to produce a high ratio of surface to mass in the liquid phase and thereby achieve high rates of mixing and evaporation. For the current needs, a compact configuration arrangement is needed to meet the design requirements of small volume and high maintenance availability. As compared with the traditional design, the new atomizer designs should possess better energy conversion efficiency (from pressure to kinetic energy). The technique of combining two or more principles has well served in the field of atomization in the past. The drawbacks of one type of atomizer can be overcome by combining it with other types of atomizer, in what is generally referred to as a “hybrid atomizer”. The atomizer discussed in this paper combines the principles of twin-fluid internally mixed atomizers and conventional pressure swirl atomizers to produce a spray the characteristics of which can be controlled over a wide range of operating conditions.
In terms of a common engineering material, modern duplex stainless steels emerged in the early 1980s, developed from cast alloys. Their popularity stems from an attractive combination of properties, including high strength and excellent resistance to chloride stress corrosion cracking. The present paper gives a brief review of the history and some recent developments of duplex stainless steel grades and the improvements made on the standard S32205 DSS lowering the Ni and Mo contents to produce an economical alternative of the well-known grade or in the case of the superduplex S32750 grade increasing the content of Cr, Mo and Nor elevating the content of Cr, N, Cu and W in combination with relatively lower contents of Ni and Mo to improve the strength, toughness and corrosion properties for the oil industry. Parallel to the development of higher-alloy duplex grades for corrosive conditions, there has recently been a great interest in leaner compositions for wider purposes with lower amounts of expensive alloying elements. In this respect, a new patent correspond to the type S32101 DSS has been developed. Finally, the most modern applications in the field of oil and petrochemical industry are described and the major uses of the three main grades, lean, 2205 and 2507, are commented.
Absorption cooling offers the possibility of using heat to provide cooling. For this purpose heat from a conventional boiler can be used or waste heat and solar energy. When the latter systems are used absorption systems minimize also the adverse effects of burning fossil fuels and thus protect the environment. Absorption systems fall into two major categories, depending on the working fluids. These are the ammonia-water systems, in which ammonia is the refrigerant and lithium bromide-water systems in which water vapor is the refrigerant. This paper initially introduces the two systems and then outlines recent patents in this area. The future trends of research in this area would be on other refrigerant pairs which will be more effective.
Innovative investigations, discoveries and recent patents regarding superelastic shape memory alloy (SMA), a novel material, are briefly discussed in this review paper. Known as a functional material, SMA can recover large strains in two ways: shape memory effect (SME) and pseudoelasticity. SME is by virtue of temperature induced martensitic transformation while pseudoelasticity (also called superelasticity) happens because of stress induced martensitic transformation (SIMT). SMA is one of the most widely used functional materials in many adaptive structures, as well as in medical and biomedical applications. Because of SME, SMA can be mainly used for active control of adaptive structures. On the other hand, having pseudoelasticity SMA can be used for passive damping of a vibrating structure. Superelastic SMA is also widely used for applications like: antenna of portable phones, headband of headphones, in the ballpoint pens and eyeglass frames etc. This study will focus mainly on pseudoelasticity of SMA and its potential characteristics.
Currently, electrochemical plating, conversion coatings, anodizing, deposition of thin films (organic, inorganic or hybrid), laser surface alloying, cladding and organic coatings are employed to improve surface properties such as hardness or corrosion resistance. For example, the development of new “smart” coating systems implies not only mechanical covering of the protected surface with a dense barrier coating but also provides active properties which can allow continued physical or chemical protection, even after partial mechanical damage of the coating, by self-healing effects. In other cases, the active properties imply biological effects, by releasing of chemicals from “drug delivery” systems, or photoelectric effects due to doping the surface with adequate elements. These “smart” properties can be achieved by inclusion of specific additives into the coating system and can stimulate the superficial reactions after some damage. The sol-gel coating process is one of the most promising methods to create protecting coatings producing sensitive inorganic surfaces in general. In this environmentally friendly process, inorganic or inorganic-organic hybrid polymers are obtained by controlled hydrolysis and condensation reactions of molecular precursors. This article compares examples of the recent patents of active coatings and some of their important industrial utilizations.
In this work, we take an interest in the dynamic behavior study of structures coupled with fluids. We find these coupled systems in several industrial applications, therefore their sizes are important and their parameters should not be supposed deterministic. Our principal target is to test and validate methodologies which consist in condensing the system (that means to reduce the number of unknowns) and carrying out the stochastic study with noniterative methods. These methodologies will enable us to solve these problems, without using the classical methodology which consists in making a direct modal calculation combined with the Monte Carlo simulation which is a very greedy (in CPU) iterative method. The example of a voluminal structure immersed in water is studied to validate the proposed methodologies. The results of this study coincide with the references results and tend to show that it will be interesting to apply the proposed methodologies in the global conception process of recent patents, as the geothermal exchange systems.