Planar Wave Propagation Through a Tapered Flagellated Nanoswimmer

Plane wave propagation in layered piezoelectric phononic crystals is considered. The wavefields are calculated in terms of the transfer matrix method providing a sustainable solution through the exploitation of T-matrix in Jordan form. Representation based on eigenvalues of transfer matrix leads to numerical stability, it allows estimation of wave energy transmission coefficients for analysis of filtration properties. The results of parametric studies of elastic wave propagation in piezoelectric phononic crystal are presented.

In this letter, an analytic stochastic model for the propagation of plane waves in two parallel urban streets is developed. The received power at the end of the topology is obtained and three solution cases of significant and practical interest are identified and studied in detail. In addition, a linear approximation method is proposed for the same problem. Numerical results are provided to analyze the nature of the propagation with respect to the parameters, symmetry of the topology and the applicability of the approximation method. The proposed analytic model is simple, yet it can capture the basic mechanism of propagation and can be used as an early indication before the application of large-scale methods in practical scenarios.

This paper presents a problem-oriented approach, designed for the numerical simulation of seismic wave propagation in models containing geological formations with complex properties such as anisotropy, attenuation, and small-scale heterogeneities. Each of the named property requires a special treatment that increases the computational complexity of an algorithm in comparison with ideally elastic isotropic media. At the same time, such formations are typically relatively small, filling about 25% of the model, thus the local use of computationally expensive approaches can speed-up the simulation essentially. In this paper we discuss both mathematical and numerical aspects of the hybrid algorithm paying most attention to its parallel implementation. At the same time essential efforts are spent to couple different equations and, hence, different finite-difference stencils to describe properly the different nature of seismic wave propagation in different areas. The main issue in the coupling is to suppress numerical artifacts down to the acceptable level, usually a few tenth of the percent.

Anisotropy is widely-used nowadays in seismic processing as it may characterize fractured reservoirs, pre-stressed state of formations etc. However, numerical simulation of seismic wave propagation in anisotropic media requires the use of advanced, computationally-intense algorithms. Meanwhile anisotropic formations take relatively small part, several percents, of the model. In this situation it is reasonable to develop a finite-difference algorithm coupling the anisotropy-oriented scheme with efficient standard staggered grid, or Virieux, scheme. So, that the computationally-intense algorithm is used only inside the anisotropic formations, while the Virieux scheme is used in the major isotropic part of the model. The coupled scheme may be almost as efficient as Virieux scheme but providing full detailed knowledge about wave propagation in anisotropic formations.

The need for filaments is currently increasing but the prices offered in the market are very expensive. This research develops a new extruder machine with HDPE material. The high quality filaments are characterized by high durability and constant diameter. The variables used in this research are temperature, screw speed, towing speed and blower. Based on ANOVA processing using Minitab it is known that all variables have no effect on the uniformity of diameter and ovality response. Based on the results of this research that the bottle cap tensile strength (HDPE) has a value of 15.7 so that it is still far below the PLA tensile strength.

Drilling of micro-cooling holes in turbine blades on hard material like Inconel 625 is one of the noteworthy applications of micro-drilling. An experimental investigation on the hole quality assessment and drill bit tool life while micro-drilling of Inconel 625 is not explored in detail. This paper presents the experimental study and multi-response optimization of test parameters of Inconel 625 in micro-drilling conditions using desirability approach. Test parameters are micro-drill diameter, spindle speed, and feed rate. The micro-drilling test, based on the Taguchi L27 design, is performed on a 2-mm plate thickness of Inconel 625 with uncoated micro-drill. After each drilling test, the hole properties including hole diameter, circularity error, overcut, taper ratio, cylindricity and hole damage factor are measured, and the results are examined. In addition to that, the number of micro-holes that can be drilled is analysed to observe the lifelong tool performance on hole quality assessment. As a result, the number of holes drilled before tool breakage is 25 in magnitude. The deviation in hole diameter, cylindricity, circularity error, roundness, overcut, taper ratio, and hole damage factor obtained is increased to 5.5%, 87.2%, 50.5%, 5.7%, 77.4%, 20% and 5.4% from 1st hole to 25th hole at an optimal level of high tool diameter, low speed, and high feed rate. The most significant drilling parameters for the above-studied response factor are tool diameter and spindle speed. From the results, the 0.8 mm is the most suitable tool diameter for hole quality achievements and productivity in practical micro-drilling applications.

This paper investigates the nonlinear bending behavior of sandwich plates with functionally graded auxetic 3D lattice core. First and foremost, an auxetic 3D lattice metamaterial with negative effective Poisson’s ratio (EPR) is designed and examined via theoretical and finite element methods with experimental verifications using specimens fabricated by 3D printing. Furthermore, three functionally graded configurations of the auxetic 3D lattice core through the plate thickness direction are proposed and compared with the uniform distribution case. Full-scale finite element modeling and nonlinear thermal-mechanical analysis are performed for the sandwich plates, with the temperature-dependent material properties of both core and face sheets taken into account. Numerical results revealed that the auxetic core can remarkably reduce the lateral deflections, with comparison to their non-auxetic counterpart with positive EPR. Parametric studies are further carried out to demonstrate the effects of functionally graded configurations, temperature rises, facesheet-to-core thickness ratios, boundary conditions, and strut radii on the nonlinear bending load-deflection curves, along with EPR-deflection curves in the large deflection region.

This paper intentions to study the effect of using different tapered longitudinal section manifolds rather than the uniform one, in a Z shaped flat plate solar collector on; the uniformity of flow distribution, pressure drop, and consequently temperature profile. To this end, a 3D CFD model is planned to mimic a parallel piping network of Z configuration. Considering both fluid and piping body domains, and moreover, the inlet and outlet junctions, that would affect the resulted system pressure drop. The system has the following specifications: uniform header diameter of 20 mm, manifold and header lengths of 1150 mm, ten tubes, tubes diameter of 7 mm, tubes length of 1780 mm, horizontally mounted, and, with imposed solar radiation. Different taper ratios of the manifold, from 1.0 to 2.4 are studied against inlet ReD ranges from 300 to 2100. The model is validated with existing experimental outcomes from literature and showed an excellent agreement. Two indices are used to quantify the flow distribution uniformity. Generally the results concluded that, for enhanced flow distribution uniformity, an optimum taper ratio is important to be defined per each ReD.

Simulation and testing to develop an Intelligent Blade for wind turbines is presented in this paper. The concept blade has an integrated sensor system for structural health monitoring that will continuously monitor the condition of the blade, warn of initiating damage, and provide instant information that can be used to regulate loading in the blade to reduce or prevent fatigue damage. This can decrease maintenance costs, improve the reliability of wind power, and may make wind energy more affordable. Modeling and simulation of wave propagation in a plate was performed and different configurations of active and passive piezoceramic sensor systems were evaluated and shown to be capable of measuring propagating strain waves and identifying damage. A preliminary experiment to determine the damage detection capability of the sensors was done during a static test of a wind turbine blade. The stress wave propagation characteristics of the blade were monitored as the load level on the blade was increased until blade failure occurred. The effects of the blade stress and curvature on wave propagation need further study, but the results indicate that the technique has the potential for the detection of evolving damage in composite wind turbine blades.

The paper presents the results of numerical analyses carried out for 2D models of aluminum plates undergoing crack propagation. Different types of numerical analyses were performed to show the area of applicability of a non-local discrete formulation of mechanical continua for NDE and QNDE. The authors’ interests dealt with: Lamb wave propagation, higher harmonics generation, the phenomenon of clapping, and wave generation and its propagation for growing crack. In the first case a 2D model allowed to find the displacements for the vertical cross-section along the direction of wave propagation and therefore assess its disturbance when introducing a notch. In-plane components of the displacements were considered for the latter 3 cases, in turn. The above cases and elaborated non-local numerical models were discussed in terms of detection of propagating crack. Apart from theoretical aspects of the presented work, the obtained results seem to be of great importance for improvement of experiments in terms of sensor distribution and required accuracy.

Accurate simulations of seismic wave propagation in complex geological structures with great and rapid variations of topography are of primary interest for environmental and industrial applications. Unfortunately, difficulties arise for such complex environments, due essentially to the existence of shadow zones, head waves, diffractions and edge effects. Usually, methods and codes are tested against "validated" ones, but one might wonder which method/code ultimately approaches the "real" solution. An original approach for seismics is to compare synthetic seismic data to controlled laboratory data for a well-described configuration, in order to analyze the respective limitations of each method/code. This is one of the objectives of the BENCHIE project, which brings together laboratories in France, Norway and Russia. In this presentation we will present some preliminary results provided by both laboratory experiments conducted in a tank and numerical simulations of wave propagation. The laboratory data have been obtained by zero-offset acquisitions at different ultrasonic frequencies on the Marseille model which is made up of anticlines, fault and truncated pyramid. The numerical results have been obtained by two methods: the Spectral-Element Method and the Tip-Wave Superposition Method.

Modeling concepts are utilized whenever relationships are described between two or more quantities. One of the most elementary cardiovascular models is the relationship between mean arterial blood pressure and mean arterial blood flow in a vascular bed, described as vascular resistance. For simulation purposes, the electrical analogy is conventionally used where voltage (V) is analogous to pressure (P) and current (I) is analogous to flow (Q), such that the equivalent ohmic resistance (R) is obtained from the relationship P = Q.R. This analogy to Ohm’s Law (V=I.R) implies a linear relationship, such that R can be determined for any value of P and Q. However, the physiological constituents of R, that is, vascular geometry and blood viscosity, are also functions of P and Q. Hence the relationship between P and Q is inherently non-linear, with the degree of nonlinearity depending on the anatomical location along the arterial tree and so the value of velocity of blood flow. This concept applying to steady values of P and Q is extended to time varying signals, P(t) and Q(t), where steady state oscillations are described in the frequency (ω) domain such that the relationship between oscillatory pressure (P(ω)) and flow (Q(ω)) is vascular impedance (Z(ω)), and where R is the zero-frequency value of Z(ω).The non-linearities are also inherent in the impedance model, since the elastic properties of the arterial wall makes constitutive parameters such as wave speed and vessel diameter pressure dependent. However, in the range of pressure excursions during the cardiac cycle, the effects of non-linearity are relatively small, hence allowing closed form expressions of impedance based on vascular and blood properties, such that the input impedance spectrum can describe the complete hemodynamics of the vascular bed. When applied to the ascending aorta or the pulmonary artery, it describes the dynamic load on the left and right ventricles respectively. When the impedance model is applied to distributed structures such as branching vascular trees, it can be used to investigate underlying concepts related to optimal functions determined by allometric relationships of cardiovascular parameters (eg heart rate) and body size. Simulation of wave propagation in arterial models can be used determine factors that contribute to the change in pulse waveform throughout the arterial tree and inclusion of non-linear properties, such as pressure-dependent elasticity, can simulate changes in arterial hemodynamics due to gravitational effects on arteries, as occurs with changes from supine to upright posture.KeywordsArterial TreeImpedance ModelAllometric RelationshipArterial Blood FlowPulse WaveformThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In this study, a theoretical analysis is presented for estimating the in-plane geometric nonlinear elastic stability behavior of steel members with tapered elements under dynamic loads. Beam-column approach is adopted for modeling the structural members as beam-column elements. The formulation is based on the Eulerian description taking into consideration the influence of axial force on bending stiffness. The changes in member chord length due to axial deformation and flexural bowing are also considered. In the dynamic analysis, the system mass properties have been represented using both lumped and consistent mass matrices. The consistent mass matrix is derived in three components: translational, rotational, and axial inertia. The formulation of the mass matrices in local and global coordinate systems of tapered members, which incorporates geometric nonlinearity, has been presented. A parametric study is conducted to examine the effects of number of tapered elements, tapering the prismatic members, time step size, and tapering ratio. The dynamic responses of tapered members have been shown to be significantly affected by these parameters.

In this study, a combination of two fundamental frequencies f1=485 KHz and f2 = 515 KHz. The source transducers are placed on the surface of the sand 25 cm above the bottom and 20 cm below the water surface in the tank of dimension 74 × 47 × 43.5 cm simulating a seabed with sand of maximum particle size of 5 mm. Burger's equation is the simplest model for describing the second order nonlinear effects in the propagation of high amplitude plane waves and, in addition, the dissipative effects in media. Typically, the interactions of two acoustic waves at a discontinuity in a dispersive but homogeneous medium will generate harmonics and intermodulation terms. This is numerically modeled in Matlab using the finite difference time domain method with Neumann boundary conditions and practically verified with measurements from the tank. The measured and simulated results have shown significant agreement with the theory. For instance, second order intermod term show 2 dB decreases in amplitude for 7 mm increase in thickness at constant density of plywood. Also if the thickness is kept same, e.g., 5 mm, there is 10 dB drop in same intermod term for change in density from plywood 550 kg/m3 to copper 8930 kg/m3.

This work is inspired by the observation, that gas hydrate bearing sediments have a high velocity in combination with high attenuation. We study numerically the influence of different gas hydrate locations within the pore space on transmitted p-waves. From the wave propagation simulations on the micro--scale it can be seen, that different positions of the gas hydrate in the pore space results in almost the same effective velocities and attenuation, as long as the gas hydrate had contact to the sediment grains. This changes in the case of a suspension, here the attenuation increases and the effective velocity decreases. The resulting p-wave versus gas hydrate saturation plot is in a qualitatively good agreement with experimental results obtained for the Mallik 2L-38 well.