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An experimental study has been conducted to investigate and compare the effects of bevelled and double-bevelled circular nozzles on supersonic jet screech at a nozzle-pressure-ratio of 5. In particular, near- and far-field microphone measurements and schlieren visualizations were utilized to look into selected acoustic and flow features associated with jet screech radiation. Results show that bevelled nozzles eliminate jet screech by producing asymmetric shock structures and instability waves that are mismatched in phase and amplitude. In contrast, double-bevelled nozzles produce symmetric shock structures and amplify screech intensity, even when jet-mixing effects have been significantly enhanced. It is further observed that amplified jet screech produced by double-bevelled nozzles are highly unsteady and undergo non-periodic and stochastic temporal variations. Last but not least, double-bevelled nozzles also impact significantly upon screech peak noise locations and confer different changes along different measurement planes. The present study demonstrates that not all bevelled-type nozzles are able to mitigate jet screech, with non-optimal designs amplifying it instead.

This study was designed to examine the effects of the anastomotic angle on the flow and haemodynamic parameter distribution patterns of the proximal anastomoses, with emphasis on identifying site-specific haemodynamic features that could reasonably be expected to trigger the initiation and further development of anastomotic intimal hyperplasia. Particle image velocimetry measurements were carried out with three simplified glass proximal models under a physiological flow condition. The results revealed that the disturbed flow and the induced shear stress patterns including low recirculation flow, stagnation point, high wall shear stress, high temporal wall shear stress gradient, low time-averaged wall shear stress (TAWSS), and high oscillating shear index (OSI) occurred around the anastomotic joints and the flow field at proximal anastomosis was strongly affected by the anastomotic angle. Among the three models investigated, the 45° backward anastomosis is found to have a smaller low-recirculation-flow region along the graft inner wall, non-stationary stagnation, and separation points, a higher TAWSS and smaller high-OSI low-TAWSS and low-OSI high-TAWSS regions.

A mesh-free radial basis function method is presented to analyze the static deflection, free vibration and buckling analysis of laminated composite plates using third-order shear deformation plate theory. The problem domain represented by a set of scattered nodes in its support domain based on the radial basis functions with polynomial reproduction. Based on the third-order shear deformation plate theory, variation forms of the static, free vibration and buckling system equations are formulated in terms of displacements and are discretized. The shape function thus constructed possesses a delta function property, and hence the essential boundary conditions can be implemented with ease as in the conventional finite element method. Several numerical examples are presented to demonstrate the convergence, accuracy and validity of the proposed method. Comparison of results with the exact solution as well as finite element method in the literature suggests that the mesh free radial basis function method yields an effective solution method for laminated composite plates. The effects of the modulus ratio, side-to-thickness ratio, shear correction factor and boundary conditions are discussed.

The meshfree point interpolation method (PIM) based on polynomial function is presented for the static analysis of spatial general shell structures. The formulation of the discrete system equations is derived from stress resultant geometrically exact shell theory of shear flexible shells based on the Cosserat surface. The PIM technique constructs its interpolation functions through a set of arbitrarily distributed points in the problem domain and its shape function has the delta function property. Hence, the implementation of essential boundary conditions can be imposed with ease as in conventional finite element method. An improved matrix triangularization algorithm (MTA) is proposed to obtain proper node enclosure and basis selection in order to overcome the singularity problem in the point interpolation method using a polynomial basis. It is found that the shape functions are generally not compatible to ensure the compatibility of the solution and lead to non-conforming PIM (NPIM) when the energy principles are used to formulate PIM. To obtain compatible shape functions, the enforcement of compatibility is needed along the common edges of the background cells in the problem domain and a background cell-based nodal selection is utilized, which lead to conforming PIM (CPIM). Both NPIM and CPIM are evaluated in the paper. Several benchmark problems for shells are analyzed to demonstrate the validity and efficiency of the NPIM and CPIM. The phenomena of shear locking and membrane locking are illustrated by showing the membrane and shear energies as fractions of the total energy. The convergences and performances are investigated for both conforming and non-conforming PIMs. It is also shown that the NPIM and CPIM with the improved MTA are very easy to implement and very efficient in constructing shape functions in comparison with the Element-Free Galerkin method.

The implementation of the conforming radial point interpolation method (CRPIM) for spatial thick shell structures is presented in this paper. The formulation of the discrete system equations is derived from a stress-resultant geometrically exact theory of shear flexible shells based on the Cosserat surface. A discrete singularity-free mapping between the five degrees of freedom of the Cosserat surface and the normal formulation with six degrees of freedom is constructed by exploiting the geometry connection between the orthogonal group and the unit sphere. A radial basis function is used in both the construction of shape functions based on arbitrarily distributed nodes as well as in the surface approximation of general spatial shell geometries. The major advantage of the CRPIM is that the shape functions possess a delta function property and the interpolation function obtained passes through all the scattered points in the influence domain. Thus, essential boundary conditions can be easily imposed, as in finite element method. A range of shape parameters is studied to examine the performance of CRPIM for shells, and optimal values are proposed. The phenomena of shear locking and membrane locking are illustrated by presenting the membrane and shear energies as fractions of the total energy. Several benchmark problems for shells are analyzed to demonstrate the validity and efficiency of the present CRPIM. The convergence rate of the results using a Gaussian (EXP)radial basis is relatively high compared to those using a multi-quadric (MQ) radial basis for the shell problems.

Previously aortic stiffness is frequently assessed through pulse pressure and pulse wave velocity (PWV) measurements. However, these methods need aortic pressure obtained by catheterization. A new model has been developed to rapidly determine the aortic pressure profile and simultaneously calculate aortic stiffness. Comparison between the aortic pressure result obtained from this and catheterization data demonstrates good agreement, while this method is non-invasive. This totally non-invasive method should be useful in assessing arteriosclerotic disease in clinical setting.