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1
Khalid Ahmed, Nayaz, and Martin Hecht. "A boundary condition with adjustable slip length for lattice Boltzmann simulations." Journal of Statistical Mechanics: Theory and Experiment 2009, no. 09 (September 29, 2009): P09017. http://dx.doi.org/10.1088/1742-5468/2009/09/p09017.
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Hwang, W. M., and C. Z. Yu. "Optimal Synthesis of the Adjustable Knock-Out Cam-Follower Mechanism of a Bolt Former." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 219, no. 8 (August 1, 2005): 767–74. http://dx.doi.org/10.1243/095440605x31553.
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This paper presents a feasible method for improvements to the adjustable knock-out cam-follower mechanism of a bolt former. On the basis of the results of analysing an existing knock-out mechanism of a bolt former, the design requirements for a new mechanism are developed. In order to meet some specific requirements and that the displacement, velocity, and acceleration curves of the follower motion are continuous, the new cam profile consists of two circular arcs and a fifth-degree or sixth-degree polynomial segment. For the cam profile with a sixth-degree polynomial segment, besides the six specified boundary conditions, a variable condition is used as a design variable for the optimization design. The maximum strike velocity between the knock-out screw and knock-out pin for all knock-out strokes is minimized by using the golden section method. The kinematic characteristics of the new knock-out camfollower mechanism synthesized are better than those of the existing mechanism. The method presented is illustrated by an example.
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Samii, Ali, and Vahid Lotfi. "High-order adjustable boundary condition for absorbing evanescent modes of waveguides and its application in coupled fluid–structure analysis." Wave Motion 49, no. 2 (March 2012): 238–57. http://dx.doi.org/10.1016/j.wavemoti.2011.10.001.
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Herbert, Eric, Cyprien Morize, Aurélie Louis-Napoléon, Christophe Goupil, Pierre Jop, and Yves D’Angelo. "Buoyancy-driven destabilization of an immersed granular bed." Journal of Fluid Mechanics 843 (March 26, 2018): 778–809. http://dx.doi.org/10.1017/jfm.2018.141.
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Under suitable conditions, an immersed granular bed can be destabilized by local thermal forcing and the induced buoyant force. The destabilization is evident from the triggering and establishment of a dense fluid-like granular plume. Varying the initial granular layer average height $h$, a time series of the free layer surface is extracted, allowing us to dynamically compute the underlying volume of the granular layer. Different observed phenomena, namely the initial interface deformation, the lowering of the average granular interface (i.e. decrease of the granular layer volume) and the emission of a plume, are analysed. We show that the phenomenon is mainly driven by heat transfer, for large $h$ and also involves a variable height thermal boundary condition and Darcy flow triggering, for small $h$. Simple modelling with no adjustable parameters not only allows us to capture the observed scaling power laws but is also in quantitative agreement with the obtained experimental data.
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Ukita, Jinro, and Douglas G. Martinson. "An efficient adjustable-layering thermodynamic sea-ice model formulation for high-frequency forcing." Annals of Glaciology 33 (2001): 253–60. http://dx.doi.org/10.3189/172756401781818194.
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AbstractRecent observations suggest that high-frequency forcing events have profound influence on the air-sea-ice interactions in the polar region. Studying these events with sea-ice models requires close examination of the model sensitivity that may arise from the high-frequency variability of the forcing. We show that the maximum layer thickness is dictated by the time-scale of the forcing variability and that the computation of the surface temperature develops enhanced sensitivity at high-frequency forcing. We resolve these constraints by developing an "adjustable-layering" thermodynamic formulation for ice and snow that re-computes the number of layers required each time-step to satisfy this maximum thickness, which preserves the total enthalpy and general internal thermal gradients. The conservation equations form a tri-diagonal system ideal for a fast and efficient implicit solution. Furthermore, we resolve the issue of the high sensitivity of the surface flux balance by solving the linearized version of the flux boundary condition simultaneously with the overall conservation system. In this paper we develop the analyses specifying the model requirements, describe the model system and test its algorithmic implementation.
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Zhang, Jun, Xin Wu Zeng, Yi Bo Wang, Zhen Fu Zhang, and Dan Chen. "Numerical Simulation of the Buried Object Detection Based on Underwater Plasma Acoustic Source." Applied Mechanics and Materials 105-107 (September 2011): 80–83. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.80.
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Detection and classification of buried objects is of great importance in underwater counterterrorism and archaeology. To penetrate the sediment, a low frequency intensive acoustic source is needed. Underwater plasma acoustic source (UPAS) with high voltage discharge has the advantage of adjustable pulse length, high source level output and no pollution to the environment, which can satisfy these needs. In this paper, we introduced the UPAS, including its basic mechanism, structure and pressure output. Then we build up an elastic wave propagation model, solved it with finite difference and staggered grid methods, and combined with certain source and boundary condition, we simulated and analyzed the pressure wave propagation in time domain with an aluminum cylinder buried in sediment, from the results we validated the effectiveness of UPAS in the application of buried object detection.
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Sekularac, Milan, and Novica Jankovic. "Experimental and numerical analysis of flow field and ventilation performance in a traffic tunnel ventilated by axial fans." Theoretical and Applied Mechanics 45, no. 2 (2018): 151–65. http://dx.doi.org/10.2298/tam171201010s.
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To investigate air flow in longitudinally ventilated traffic tunnels, a scaled model of a typical road-traffic tunnel with an appropriate ventilation system based on axial ducted fans, is designed and built in the Lab. The focus of this paper is the airflow in a bi-directional traffic, two-lane tunnel. At the scale ratio of approx. 1:20, at 20.52m length it represents ? 400m of a realscale tunnel. The model consists of two parallel tunnel tubes, where the main tunnel (with a hydraulic diameter of ???1 ? 0.4m) has the geometry of a scaled road traffic-tunnel. The second tunnel (???2 ? 0.16m) has a smaller size and is circular in cross-section, used only to simulate airflow towards an evacuation tunnel tube. Thus the two tunnels are connected by the evacuation passages, equipped with adjustable escape doors. By a combination of experimental and numerical work, the air flow-field and the performance of the ventilation system are investigated. The velocity field and its turbulence properties exiting the fans were determined experimentally using hot-wire anemometry. These data were further processed to be used in the tunnel flow computations by CFD. The efficiency of momentum transfer (????, Kempf factor) of the longitudinal tunnel ventilation is determined. The effect that the imposed boundary conditions and the level of their detail, have within a CFD computation of tunnel airflow, with respect to accuracy, velocity distribution and computed ????. Finally a traffic-loaded (traffic ?jam?) case of flow is studied through experiment and CFD. The difficulty in assessing the required thrust of the plant in traffic-jam tunnel conditions is discussed, and the ventilation efficiency is estimated. Based on later results, the two limiting shapes of axial velocity distribution with respect to height above the road, in this type of tunnel and traffic, are estimated. The last result can be used as a realistic boundary condition (as inlet b.c. and/or initial condition) for numerical studies of flow and fire scenarios in such tunnels with the traffic load critical for design.
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Canuto, V. M., M. S. Dubovikov, M. Luneva, C. A. Clayson, and A. Leboissetier. "Mixed layer mesoscales: a parameterization for OGCMs." Ocean Science Discussions 7, no. 2 (April 29, 2010): 873–917. http://dx.doi.org/10.5194/osd-7-873-2010.
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Abstract. We derive and assess a parameterization of the mixed layer vertical and horizontal mesoscale fluxes of an arbitrary tracer. The results, which are obtained by solving the mesoscale dynamic equations and contain no adjustable parameters, are expressed in terms of the large scale fields resolved by coarse resolution OGCMs (ocean global circulation models). The new model can be put in the right perspective by considering the following. Thus far, the lack of a mixed layer mesoscale model that naturally satisfies the required boundary condition (the vertical flux must vanish at the surface), was remedied by extending the stream function modeled for the adiabatic deep ocean into the mixed layer using an arbitrary tapering function chosen to enforce the required boundary condition. The present model renders the tapering schemes unnecessary for the vertical flux automatically vanishes at the ocean surface. The expressions we derive for the vertical and horizontal mesoscale fluxes are algebraic and should be used in conjunction with any of the available mesoscale models valid in the adiabatic deep ocean. We also discuss a new feature representing the effect of sub-mesoscales on mesoscales. It is shown that in the case of strong wind, one must add to the mean Eulerian velocity that enters the parameterization of the mesoscale fluxes a new term due to sub-mesoscales whose explicit form we work out. The assessment of the model results is as follows. First, previous eddy resolving results indicated a robust re-stratification effect by mesoscales; we show that the model result for the mesoscale vertical flux leads to re-stratification (its second z-derivative is negative) and that it is of the same order of magnitude but opposite sign of the vertical flux by small scale turbulence, leading to a large cancellation. Second, since mesoscales act as a source of the eddy kinetic energy, we compare the predicted surface values vs. the Topex-Poseidon. Third, we carry out an eddy resolving simulation and assess both z-profile and magnitude of the model vertical flux against the simulation data. The tests yield positive results. A more stratified mixed layer has implication for the oceanic absorption of heat and CO2, a feature whose implications on climate predictions we hope to explore in the future.
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Wang, Hui Ping, and Qiao Jin. "Study of the Baseline Finite Element Model of a Cable-Stayed Bridge Based on the Field Inspection Data." Advanced Materials Research 243-249 (May 2011): 1908–16. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.1908.
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For steel cable-stayed bridges which have been operating for many years, their static and dynamic parameters have been being changed because of corrosion and overloading. Therefore, an adjustable numerical model, describing and orienting all the various phases of the safety status of bridges, is needed for a theoretical guide of daily maintenance or periodical repair for them. In order to build such a model reflecting the different phases of working conditions of a bridge, a link between the model and the present condition of the targeted bridge should be erected by periodical field inspections for the structure. In this paper, backed on a practical engineering example, the Shengli cable-stayed bridge of Dongying, a finite element model (FEM) based on the periodical field inspection data was proposed, which could possess a strategy modified correspondingly according to parts or all of the results in the field inspections. Specifically, for the initial FEM, three important issues in the modeling of such a complicated bridge, such as simulation of boundary conditions, equivalence of orthotropic steel deck, and implementation of accurate cable tensions, were firstly studied. Then, the initial finite element model built was modified in terms of the optimization principle by minimizing the difference between the static deflections resulting from the field inspection and those calculated by the FEM before being modified. Lastly, dynamic results from the field inspection were compared with those from the optimized FEM to justify feasibility and reasonability of the developed three-dimension FEM which could reflect one or some certain properties of the structure we were emphatically paying attention to. This model-building and model-modifying method for the baseline FEM of the Shengli cable-stayed bridge also provided reference for the similar existing cable-stayed bridges.
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Schulz, M. "Non-spherical source-surface model of the heliosphere: a scalar formulation." Annales Geophysicae 15, no. 11 (November 30, 1997): 1379–87. http://dx.doi.org/10.1007/s00585-997-1379-1.
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Abstract. The source-surface method offers an alternative to full MHD simulation of the heliosphere. It entails specification of a surface from which the solar wind flows normally outward along straight lines. Compatibility with MHD results requires this (source) surface to be non-spherical in general and prolate (aligned with the solar dipole axis) in prototypical axisymmetric cases. Mid-latitude features on the source surface thus map to significantly lower latitudes in the heliosphere. The model is usually implemented by deriving the B field (in the region surrounded by the source surface) from a scalar potential formally expanded in spherical harmonics, with coefficients chosen so as to minimize the mean-square tangential component of B over this surface. In the simplified (scalar) version the quantity minimized is instead the variance of the scalar potential over the source surface. The scalar formulation greatly reduces the time required to compute required matrix elements, while imposing essentially the same physical boundary condition as the vector formulation (viz., that the coronal magnetic field be, as nearly as possible, normal to the source surface for continuity with the heliosphere). The source surface proposed for actual application is a surface of constant F̃ ≡ r-kB̃, where r is the heliocentric distance and B̃ is the scalar magnitude of the B field produced by currents inside the Sun. Comparison with MHD simulations suggests that k ≈ 1.4 is a good choice for the adjustable exponent. This value has been shown to map the neutral line on the source surface during Carrington Rotation 1869 (May–June 1993) to a range of latitudes that would have just grazed the position of Ulysses during that month in which sector structure disappeared from Ulysses' magnetometer observations.
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Kurahashi-Nakamura, Takasumi, André Paul, Guy Munhoven, Ute Merkel, and Michael Schulz. "Coupling of a sediment diagenesis model (MEDUSA) and an Earth system model (CESM1.2): a contribution toward enhanced marine biogeochemical modelling and long-term climate simulations." Geoscientific Model Development 13, no. 2 (March 2, 2020): 825–40. http://dx.doi.org/10.5194/gmd-13-825-2020.
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Abstract. We developed a coupling scheme for the Community Earth System Model version 1.2 (CESM1.2) and the Model of Early Diagenesis in the Upper Sediment of Adjustable complexity (MEDUSA), and explored the effects of the coupling on solid components in the upper sediment and on bottom seawater chemistry by comparing the coupled model's behaviour with that of the uncoupled CESM having a simplified treatment of sediment processes. CESM is a fully coupled atmosphere–ocean–sea-ice–land model and its ocean component (the Parallel Ocean Program version 2; POP2) includes a biogeochemical component (the Biogeochemical Elemental Cycling model; BEC). MEDUSA was coupled to POP2 in an offline manner so that each of the models ran separately and sequentially with regular exchanges of necessary boundary condition fields. This development was done with the ambitious aim of a future application for long-term (spanning a full glacial cycle; i.e. ∼105 years) climate simulations with a state-of-the-art comprehensive climate model including the carbon cycle, and was motivated by the fact that until now such simulations have been done only with less-complex climate models. We found that the sediment–model coupling already had non-negligible immediate advantages for ocean biogeochemistry in millennial-timescale simulations. First, the MEDUSA-coupled CESM outperformed the uncoupled CESM in reproducing an observation-based global distribution of sediment properties, especially for organic carbon and opal. Thus, the coupled model is expected to act as a better “bridge” between climate dynamics and sedimentary data, which will provide another measure of model performance. Second, in our experiments, the MEDUSA-coupled model and the uncoupled model had a difference of 0.2 ‰ or larger in terms of δ13C of bottom water over large areas, which implied a potentially significant model uncertainty for bottom seawater chemical composition due to a different way of sediment treatment. For example, an ocean model that does not treat sedimentary processes depending on the chemical composition of the ambient water can overestimate the amount of remineralization of organic matter in the upper sediment in an anoxic environment, which would lead to lighter δ13C values in the bottom water. Such a model uncertainty would be a fundamental issue for paleo model–data comparison often relying on data derived from benthic foraminifera.
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Noghrehabadi, Aminreza, Mohammad Ghalambaz, Mehdi Ghalambaz, and Afshin Ghanbarzadeh. "A Hybrid Power Series Artificial Bee Colony Algorithm to Obtain a Solution for Buckling of Multiwall Carbon Nanotube Cantilevers Near Small Layers of Graphite Sheets." Applied Computational Intelligence and Soft Computing 2012 (2012): 1–6. http://dx.doi.org/10.1155/2012/683483.
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A hybrid power series and artificial bee colony algorithm (PS-ABC) method is applied to solve a system of nonlinear differential equations arising from the distributed parameter model of multiwalled carbon nanotube (MWCNT) cantilevers in the vicinity of thin and thick graphite sheets subject to intermolecular forces. The intermolecular forces are modeled using van der Waals forces. A trial solution of the differential equation is defined as sum of two polynomial parts. The first part satisfies the boundary conditions and does contain two adjustable parameters. The second part is constructed as not to affect the boundary conditions, which involves adjustable parameters. The ABC method is applied to find adjustable parameters of trial solution (in first and second part). The obtained results are compared with numerical results as well as analytical solutions those reported in the literature. The results of the presented method represent a remarkable accuracy in comparison with numerical results. The minimum initial gap and the detachment length of the actuator that does not stick to the substrate due to the intermolecular forces, as important parameters in pull-in instability of MWCNT actuator, are evaluated by obtained power series.
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Abraham, D. B., L. F. Ko, and N. M. Švrakić. "Ising Model with Adjustable Boundary Conditions: Exact Results for Finite Lattice Mass Gaps." Physical Review Letters 61, no. 21 (November 21, 1988): 2393–96. http://dx.doi.org/10.1103/physrevlett.61.2393.
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Yang, Liuming, Yang Yu, Guoxiang Hou, Kai Wang, and Yeping Xiong. "Boundary conditions with adjustable slip length for the lattice Boltzmann simulation of liquid flow." Computers & Fluids 174 (September 2018): 200–212. http://dx.doi.org/10.1016/j.compfluid.2018.08.002.
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Bonnecaze, Roger T., Herbert E. Huppert, and John R. Lister. "Particle-driven gravity currents." Journal of Fluid Mechanics 250 (May 1993): 339–69. http://dx.doi.org/10.1017/s002211209300148x.
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Gravity currents created by the release of a fixed volume of a suspension into a lighter ambient fluid are studied theoretically and experimentally. The greater density of the current and the buoyancy force driving its motion arise primarily from dense particles suspended in the interstitial fluid of the current. The dynamics of the current are assumed to be dominated by a balance between inertial and buoyancy forces; viscous forces are assumed negligible. The currents considered are two-dimensional and flow over a rigid horizontal surface. The flow is modelled by either the single- or the two-layer shallow-water equations, the two-layer equations being necessary to include the effects of the overlying fluid, which are important when the depth of the current is comparable to the depth of the overlying fluid. Because the local density of the gravity current depends on the concentration of particles, the buoyancy contribution to the momentum balance depends on the variation of the particle concentration. A transport equation for the particle concentration is derived by assuming that the particles are vertically well-mixed by the turbulence in the current, are advected by the mean flow and settle out through the viscous sublayer at the bottom of the current. The boundary condition at the moving front of the current relates the velocity and the pressure head at that point. The resulting equations are solved numerically, which reveals that two types of shock can occur in the current. In the late stages of all particle-driven gravity currents, an internal bore develops that separates a particle-free jet-like flow in the rear from a dense gravity-current flow near the front. The second type of bore occurs if the initial height of the current is comparable to the depth of the ambient fluid. This bore develops during the early lock-exchange flow between the two fluids and strongly changes the structure of the current and its transport of particles from those of a current in very deep surroundings. To test the theory, several experiments were performed to measure the length of particle-driven gravity currents as a function of time and their deposition patterns for a variety of particle sizes and initial masses of sediment. The comparison between the theoretical predictions, which have no adjustable parameters, and the experimental results are very good.
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Xu, Weiping, and Elizabeth K. Ervin. "Parameters Affecting the Transient Response of an Impacting Beam." Shock and Vibration 20, no. 5 (2013): 907–19. http://dx.doi.org/10.1155/2013/196057.
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Impact causes shock waves that may be unexpected and damaging. A computationally efficient impact model with a generic beam which is discrete in time and continuous in space was undertaken; an Euler-Bernoulli beam with adjustable boundary conditions and variable contact location is numerically studied under a pulse loading. Experiments on a cantilever beam were carried out to verify the effects of influential parameters. A half-sine pulse excitation was applied through a mechanical shaker, and the deflection was captured by a high speed camera. Numerous test cases were conducted that varied pulse duration, pulse amplitude, and clearance. Decreasing the pulse duration lowers all deflection amplitudes, but the time in contact is insensitive. No gap causes minimal beam response, and increasing gap generates greater deflection. Representative test cases were selected for validating the theoretical model. When comparing numerical simulation with experimental results, satisfactory agreement for amplitude and duration can be reached even with raw input parameters. The contribution of this study is the incorporation of unique pulse loading, changeable boundary conditions, adjustable contact/impact situations, comprehensive parameter studies, and high speed photography.
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Wu, Fong-Gong, and Chii-Zen Yu. "Parametric Design and Kansei Engineering in Goblet Styling Design." Mathematical Problems in Engineering 2020 (March 19, 2020): 1–8. http://dx.doi.org/10.1155/2020/8259698.
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In this study, we developed a computer-aided product design method for goblet styling design based on two methods. The first was parametric design derived from an adjustable cam mechanism, which was used for shape generation, and the second was Kansei engineering, which was used for shape evaluation. In the shape generation method, motion curves from an adjustable cam were used. Designers can collect feature point data from existing products to define the boundary conditions of adjustable cam motion equations; furthermore, adjustable motion curves allow parametric design. Through adjusting a single parameter, motion curves were changed to be used as projective curves for the styling design of goblets. Then, a coordinate transformation method was applied to support the three-dimensional styling design of goblets. In the shape evaluation method, some goblet stylings were regularly selected to determine adjective degrees by production design experts. Adjective degrees for goblets that had not been selected were determined through interpolation. Market demand was defined as the preference of customers for specific adjective degrees for goblets.
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Abraham, D. B., L. F. Ko, and N. M. Švrakić. "Transfer matrix spectrum for the finite-width Ising model with adjustable boundary conditions: Exact solution." Journal of Statistical Physics 56, no. 5-6 (September 1989): 563–87. http://dx.doi.org/10.1007/bf01016767.
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Zhu, Ai Hua. "Simulation Analysis of Adjustable Movable Blade Axial Flow Fan." Advanced Materials Research 945-949 (June 2014): 236–41. http://dx.doi.org/10.4028/www.scientific.net/amr.945-949.236.
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This paper focuses on the study on the installation angle of the adjustable movable blade axial flow fan.At first, the airfoil and the corresponding series of fan is selected, and detailed calculation of the blade section is performed to obtain the chord length and the thickness of the fan airfoil at different circumferential surfaces, as well as the coordinate value of each section. Then, a three-dimensional solid modeling of the fan with different installation angles in Pro/E is used for mesh generation and boundary conditions arrangement in Gambit. Finally, an analogue simulation is carried out in fluent to analyze the velocity of the blade, the backpressure and turbulence generated by the airflow on the blade.
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Engelhardt, I., J. G. De Aguinaga, H. Mikat, C. Schüth, O. Lenz, and R. Liedl. "Complexity versus simplicity: an example of groundwater model ranking with the Akaike Information Criterion." Hydrology and Earth System Sciences Discussions 9, no. 8 (August 21, 2012): 9687–714. http://dx.doi.org/10.5194/hessd-9-9687-2012.
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Abstract. A groundwater model characterized by a lack of field data to estimate hydraulic model parameters and boundary conditions combined with many piezometric head observations was investigated concerning model uncertainty. Different conceptual models with a stepwise increase from 0 to 30 adjustable parameters were calibrated using PEST. Residuals, sensitivities, the Akaike Information Criterion (AIC), and the likelihood of each model were computed. As expected, residuals and standard errors decreased with an increasing amount of adjustable model parameters. However, the model with only 15 adjusted parameters was evaluated by AIC as the best option with a likelihood of 98%, while the uncalibrated model obtained the worst AIC value. Computing of the AIC yielded the most important information to assess the model likelihood. Comparing only residuals of different conceptual models was less valuable and would result in an overparameterization of the conceptual model approach. Sensitivities of piezometric heads were highest for the model with five adjustable parameters reflecting also changes of extracted groundwater volumes. With increasing amount of adjustable parameters piezometric heads became less sensitive for the model calibration and changes of pumping rates were no longer displayed by the sensitivity coefficients. Therefore, when too many model parameters were adjusted, these parameters lost their impact on the model results. Additionally, using only sedimentological data to derive hydraulic parameters resulted in a large bias between measured and simulated groundwater level.
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Li, Yu Wen, Mei Juan Zhou, and Gan Zhou. "Rapid Research and Design Parameterization of Outdoor Double Intelligent Cabinet." Applied Mechanics and Materials 741 (March 2015): 270–73. http://dx.doi.org/10.4028/www.scientific.net/amm.741.270.
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It is inevitable requirement of modern engineering rapid design for outdoor double intelligence cabinet.Taking VB as the tool,rapid parameter module of geometric parameters and boundary conditions of double intelligent cabinet was designed，the exhaust air of fan as adjustable object,then Fluent software for numerical simulation of temperature was called quickly ,using VB to display Fluent calculation results,the rapid parameter module can timely show the significant influence of exhaust air to the inside temperature.It has important guiding significance to practical engineering.
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Malik, Suheel Abdullah, Ijaz Mansoor Qureshi, Muhammad Amir, and Ihsanul Haq. "Nature Inspired Computational Technique for the Numerical Solution of Nonlinear Singular Boundary Value Problems Arising in Physiology." Scientific World Journal 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/837021.
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We present a hybrid heuristic computing method for the numerical solution of nonlinear singular boundary value problems arising in physiology. The approximate solution is deduced as a linear combination of some log sigmoid basis functions. A fitness function representing the sum of the mean square error of the given nonlinear ordinary differential equation (ODE) and its boundary conditions is formulated. The optimization of the unknown adjustable parameters contained in the fitness function is performed by the hybrid heuristic computation algorithm based on genetic algorithm (GA), interior point algorithm (IPA), and active set algorithm (ASA). The efficiency and the viability of the proposed method are confirmed by solving three examples from physiology. The obtained approximate solutions are found in excellent agreement with the exact solutions as well as some conventional numerical solutions.
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Zhang, Ying, Dongyan Shi, Dongze He, and Dong Shao. "Free Vibration Analysis of Laminated Composite Double-Plate Structure System with Elastic Constraints Based on Improved Fourier Series Method." Shock and Vibration 2021 (March 3, 2021): 1–25. http://dx.doi.org/10.1155/2021/8811747.
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An analytical model of laminated composite double-plate system (LCDPS) is established, which efficiently analyzes the common 3D plate structure in engineering applications. The proposed model combines the first-order shear deformation theory (FSDT) and the classical delamination theory, and then the LCDPS’s vibration characteristics are investigated. In the process of analysis, the improved Fourier series method (IFSM) is used to describe the displacement admissible function of the LCDPS, which can remove the potential discontinuities at the boundaries. Five sets of artificial springs are introduced to simulate the elastic boundary constraints, and the restraints of the Winkler elastic layer can be adjustable. The improved Fourier series is substituted into the governing equations and boundary conditions; then, applying the Rayleigh–Ritz method, we take all the series expansion coefficients as the generalized coordinates. After that, a set of standard linear algebraic equations was obtained. On this basis, the natural frequency and mode shapes of the LCDPS can be obtained by solving the standard eigenvalue problem. By the discussion of numerical examples and the comparison with those of the reports in the literature, the convergence and the reliability of the present approach are validated. Finally, the parametric investigations of the free vibration with complex boundary conditions are carried out, including the influence of boundary conditions, lamination scheme, plate geometric parameters, and elastic coefficient between two plates.
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Hearst, R. Jason, Guillaume Gomit, and Bharathram Ganapathisubramani. "Effect of turbulence on the wake of a wall-mounted cube." Journal of Fluid Mechanics 804 (September 9, 2016): 513–30. http://dx.doi.org/10.1017/jfm.2016.565.
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The influence of turbulence on the flow around a wall-mounted cube immersed in a turbulent boundary layer is investigated experimentally with particle image velocimetry and hot-wire anemometry. Free-stream turbulence is used to generate turbulent boundary layer profiles where the normalised shear at the cube height is fixed, but the turbulence intensity at the cube height is adjustable. The free-stream turbulence is generated with an active grid and the turbulent boundary layer is formed on an artificial floor in a wind tunnel. The boundary layer development Reynolds number ($Re_{x}$) and the ratio of the cube height ($h$) to the boundary layer thickness ($\unicode[STIX]{x1D6FF}$) are held constant at $Re_{x}=1.8\times 10^{6}$ and $h/\unicode[STIX]{x1D6FF}=0.47$. It is demonstrated that the stagnation point on the upstream side of the cube and the reattachment length in the wake of the cube are independent of the incoming profile for the conditions investigated here. In contrast, the wake length monotonically decreases for increasing turbulence intensity but fixed normalised shear – both quantities measured at the cube height. The wake shortening is a result of heightened turbulence levels promoting wake recovery from high local velocities and the reduction in strength of a dominant shedding frequency.
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Xu, Kun, and George A. McMechan. "3D scalar-wave absorbing boundary conditions with optimal coefficients in the frequency-space domain." GEOPHYSICS 77, no. 3 (May 1, 2012): T83—T96. http://dx.doi.org/10.1190/geo2011-0412.1.
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To improve the computational efficiency for the solution of the 3D Helmholtz equation in the frequency-space domain, high-order compact forms of finite differences are preferred. We applied a pointwise Padé approximation to develop a 3D 27-point fourth-order compact finite-difference (FD) stencil in the grid interior, with a space-differentiated source term, for the scalar-wave equation; this has similar high-accuracy (4–5 grid points per the shortest wavelength) to another 27-point fourth-order FD stencil using a parsimonious mixed-grid and staggered-grid combination, but is much simpler. For absorbing boundary conditions (ABCs), a damping zone is expensive, and a perfectly matched layer can not be straightforwardly introduced into the compact FD form for the second-order wave equation. Thus, we developed 3D one-way wave equation (OWWE) ABCs with adjustable coefficients. They have different angle approximations and FD forms for the six faces, twelve edges, and eight corners in 3D models to fit with the interior compact FD form. By adjusting the coefficients to the optimum, the OWWE ABCs have wider-angle absorbing ability than those without optimal coefficients. Finally, all the interior and boundary FD forms were combined into a sparse complex-valued impedance matrix of the frequency-space modeling equation, and solved for each frequency. Because the storage of the sparse impedance matrix was determined by the 3D discrete grid size, the OWWE ABCs with only one outer layer needed the minimum grid size compared with other ABCs, thus were the most efficient for the solution of the impedance matrix. The modeling algorithm was performed on multicore processors using a MPI parallel direct solver. Numerical tests on homogeneous and heterogeneous models gave satisfactory absorbing effects.
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Matheou, Georgios, and Daniel Chung. "Large-Eddy Simulation of Stratified Turbulence. Part II: Application of the Stretched-Vortex Model to the Atmospheric Boundary Layer." Journal of the Atmospheric Sciences 71, no. 12 (November 26, 2014): 4439–60. http://dx.doi.org/10.1175/jas-d-13-0306.1.
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Abstract The buoyancy-adjusted stretched-vortex subgrid-scale (SGS) model is assessed for a number of large-eddy simulations (LESs) corresponding to diverse atmospheric boundary layer conditions. The cases considered are free convection, a moderately stable boundary layer [first Global Energy and Water Exchanges (GEWEX) Atmospheric Boundary Layer Study (GABLS)] case, shallow cumulus [Barbados Oceanographic and Meteorological Experiment (BOMEX)], shallow precipitating cumulus [Rain in Cumulus over the Ocean (RICO)] and nocturnal stratocumulus [Second Dynamics and Chemistry of the Marine Stratocumulus (DYCOMS-II) field study RF01]. An identical LES setup, including advection discretization and SGS model parameters, is used for all cases, which is a stringent test on the ability of LES to accurately capture diverse conditions without any flow-adjustable parameters. The LES predictions agree well with observations and previously reported model results. A grid-resolution convergence study is carried out, and for all cases the mean profiles exhibit good grid-resolution independence, even for resolutions that are typically considered coarse. Second-order statistics, for example, variances, converge at finer resolutions compared to domain means. The simulations show that 90% of the turbulent kinetic energy (at each level) must be resolved to obtain sufficiently converged mean profiles. This empirical convergence criterion can be used as a guide in designing future LES runs.
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TIAN, ZHI-WEI, SHENG CHEN, and CHU-GUANG ZHENG. "LATTICE BOLTZMANN SIMULATION OF GASEOUS FINITE-KNUDSEN MICROFLOWS." International Journal of Modern Physics C 21, no. 06 (June 2010): 769–83. http://dx.doi.org/10.1142/s0129183110015464.
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In this study, microscale gaseous flows in the transitional regime have been investigated by lattice Boltzmann method (LBM). In the existing microflows LBM models, the Knudsen layer correction function has been introduced into the models. According to the kinetic theory rigorously, we choose a proper expression of correction function, and then determine its adjustable parameter. A substitute high-order boundary conditions treatment is adopted to capture the velocity slip, without any difficulties in computing the high-order velocity derivatives. The numerical results of two typical microflows show that: the present results agree with the analytical solutions better than the existing LBM simulations. Evident improvements can also be found, especially for finite Kn microflows.
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Ibrahim, Wubshet, and Lelisa Kebena Bijiga. "Neural Network Method for Solving Time-Fractional Telegraph Equation." Mathematical Problems in Engineering 2021 (May 27, 2021): 1–10. http://dx.doi.org/10.1155/2021/7167801.
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Recently, the development of neural network method for solving differential equations has made a remarkable progress for solving fractional differential equations. In this paper, a neural network method is employed to solve time-fractional telegraph equation. The loss function containing initial/boundary conditions with adjustable parameters (weights and biases) is constructed. Also, in this paper, a time-fractional telegraph equation was formulated as an optimization problem. Numerical examples with known analytic solutions including numerical results, their graphs, weights, and biases were also discussed to confirm the accuracy of the method used. Also, the graphical and tabular results were analyzed thoroughly. The mean square errors for different choices of neurons and epochs have been presented in tables along with graphical presentations.
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Zoumakis, N. M., and G. A. Efstathiou. "Parameterization of Inversion Breakup in Idealized Valleys. Part II: Thermodynamic Model." Journal of Applied Meteorology and Climatology 45, no. 4 (April 1, 2006): 609–23. http://dx.doi.org/10.1175/jam2354.1.
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Abstract A simple thermodynamic parameterization based on a modified version of the Whiteman and McKee inversion destruction model is presented to simulate the evolution of vertical temperature structure during the inversion breakup period in idealized valleys under clear, undisturbed weather conditions. The proposed method adopts simplified semiempirical parameterizations of radiation and surface energy budgets at the valley floor and sidewalls and an empirical scheme for the partitioning of energy in the valley atmosphere, eliminating the need for selecting arbitrary values for the adjustable model parameters. The model accurately simulates the changes with time of the height of the inversion top and the depth of the convective boundary layer during the breakup of nocturnal temperature inversions in a wide range of valley topography. The theoretical estimates were validated and compared with dynamical model predictions and actual measurements. Because of its simplicity and its fair agreement with observations, the proposed method may be useful in applications in boundary layer, air pollution, and complex terrain meteorology. It is recognized that more work is necessary before the validity of the suggested procedure can be fully established.
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Chen, Y. Y., R. J. Hsiao, and M. C. Huang. "Fuzzy Solutions for Two-Dimensional Navier-Stokes Equations." Journal of Mechanics 34, no. 1 (November 23, 2015): 1–10. http://dx.doi.org/10.1017/jmech.2015.92.
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AbstractA new methodology via using an adaptive fuzzy algorithm to obtain solutions of “Two-dimensional Navier-Stokes equations” (2-D NSE) is presented in this investigation. The design objective is to find two fuzzy solutions to satisfy precisely the 2-D NSE frequently encountered in practical applications. In this study, a rough fuzzy solution is formulated with adjustable parameters firstly, and then, a set of adaptive laws for optimally tuning the free parameters in the consequent parts of the proposed fuzzy solutions are derived from minimizing an error cost function which is the square summation of approximation errors of boundary conditions, continuum equation and Navier-Stokes equations. In addition, elegant approximated error bounds between the exact solution and the proposed fuzzy solution with respect to the number of fuzzy rules and solution errors have also been proven. Furthermore, the error equations in mesh points can be proven to converge to zero for the 2-D NSE with two sufficient conditions.
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Shen, Zhiqiang, and Hongzhi Zhong. "Static and Vibrational Analysis of Partially Composite Beams Using the Weak-Form Quadrature Element Method." Mathematical Problems in Engineering 2012 (2012): 1–23. http://dx.doi.org/10.1155/2012/974023.
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Deformation of partially composite beams under distributed loading and free vibrations of partially composite beams under various boundary conditions are examined in this paper. The weak-form quadrature element method, which is characterized by direct evaluation of the integrals involved in the variational description of a problem, is used. One quadrature element is normally sufficient for a partially composite beam regardless of the magnitude of the shear connection stiffness. The number of integration points in a quadrature element is adjustable in accordance with convergence requirement. Results are compared with those of various finite element formulations. It is shown that the weak form quadrature element solution for partially composite beams is free of slip locking, and high computational accuracy is achieved with smaller number of degrees of freedom. Besides, it is found that longitudinal inertia of motion cannot be simply neglected in assessment of dynamic behavior of partially composite beams.
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Vogel, Kristina, Thorsten Greinert, Monique Reichard, Christoph Held, Hauke Harms, and Thomas Maskow. "Thermodynamics and Kinetics of Glycolytic Reactions. Part I: Kinetic Modeling Based on Irreversible Thermodynamics and Validation by Calorimetry." International Journal of Molecular Sciences 21, no. 21 (November 6, 2020): 8341. http://dx.doi.org/10.3390/ijms21218341.
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In systems biology, material balances, kinetic models, and thermodynamic boundary conditions are increasingly used for metabolic network analysis. It is remarkable that the reversibility of enzyme-catalyzed reactions and the influence of cytosolic conditions are often neglected in kinetic models. In fact, enzyme-catalyzed reactions in numerous metabolic pathways such as in glycolysis are often reversible, i.e., they only proceed until an equilibrium state is reached and not until the substrate is completely consumed. Here, we propose the use of irreversible thermodynamics to describe the kinetic approximation to the equilibrium state in a consistent way with very few adjustable parameters. Using a flux-force approach allowed describing the influence of cytosolic conditions on the kinetics by only one single parameter. The approach was applied to reaction steps 2 and 9 of glycolysis (i.e., the phosphoglucose isomerase reaction from glucose 6-phosphate to fructose 6-phosphate and the enolase-catalyzed reaction from 2-phosphoglycerate to phosphoenolpyruvate and water). The temperature dependence of the kinetic parameter fulfills the Arrhenius relation and the derived activation energies are plausible. All the data obtained in this work were measured efficiently and accurately by means of isothermal titration calorimetry (ITC). The combination of calorimetric monitoring with simple flux-force relations has the potential for adequate consideration of cytosolic conditions in a simple manner.
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Kantartzis, N. V., A. I. Dimitriadis, and T. D. Tsiboukis. "Combined FVTD/PSTD Schemes with Enhanced Spectral Accuracy for the Design of Large-Scale EMC Applications." Advanced Electromagnetics 1, no. 3 (October 16, 2012): 41. http://dx.doi.org/10.7716/aem.v1i3.46.
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A generalized conformal time-domain method with adjustable spectral accuracy is introduced in this paper for the consistent analysis of large-scale electromagnetic compatibility problems. The novel 3-D hybrid schemes blend a stencil-optimized finite-volume time-domain and a multimodal Fourier-Chebyshev pseudo-spectral time-domain algorithm that split the overall space into smaller and flexible areas. A key asset is that both techniques are updated independently and interconnected by robust boundary conditions. Also, combining a family of spatial derivative approximators with controllable precision in general curvilinear coordinates, the proposed method launches a conformal field flux formulation to derive electromagnetic quantities in regions with fine details. For advanced grid reliability at dissimilar media interfaces, dispersion-reduced adaptive operators, which assign the proper weights to each spatial increment, are developed. So, the resulting discretization yields highly rigorous and computationally affordable simulations, devoid of lattice errors. Numerical results, addressing detailed comparisons of various realistic applications with reference or measurement data verify our methodology and reveal its significant applicability.
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Fulcher, Lewis, Alexander Lodermeyer, George Kähler, Stefan Becker, and Stefan Kniesburges. "Geometry of the Vocal Tract and Properties of Phonation near Threshold: Calculations and Measurements." Applied Sciences 9, no. 13 (July 8, 2019): 2755. http://dx.doi.org/10.3390/app9132755.
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In voice research, analytically-based models are efficient tools to investigate the basic physical mechanisms of phonation. Calculations based on lumped element models describe the effects of the air in the vocal tract upon threshold pressure (Pth) by its inertance. The latter depends on the geometrical boundary conditions prescribed by the vocal tract length (directly) and its cross-sectional area (inversely). Using Titze’s surface wave model (SWM) to account for the properties of the vocal folds, the influence of the vocal tract inertia is examined by two sets of calculations in combination with experiments that apply silicone-based vocal folds. In the first set, a vocal tract is constructed whose cross-sectional area is adjustable from 2.7 cm2 to 11.7 cm2. In the second set, the length of the vocal tract is varied from 4.0 cm to 59.0 cm. For both sets, the pressure and frequency data are collected and compared with calculations based on the SWM. In most cases, the measurements support the calculations; hence, the model is suited to describe and predict basic mechanisms of phonation and the inertial effects caused by a vocal tract.
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Alsarraf, Jalal, Khaled Alawadhi, Abdulwahab Alnaqi, and S. A. M. Swilem. "A new approach using hybrid power series – cuckoo search optimization algorithm to solve electrostatic pull-in instability and deflection of nano cantilever switches subject to van der waals attractions." International Journal of Engineering & Technology 6, no. 2 (May 2, 2017): 29. http://dx.doi.org/10.14419/ijet.v6i2.7488.
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A hybrid Power Series (PS) and Cuckoo Search via L´evy Flights (CS) optimization algorithm (PS-CS) method is utilized to obtain a solution for the deflection and pull-in instability of a nano cantilever switch in the presence of the van der Waals attractions, electrostatic forces and fringing filed effects. In order to obtain a relation for deflection of the beam, a trial solution including adjustable coefficients, satisfying the boundary conditions of the governing, is proposed. The cuckoo search optimization algorithm is executed to find the ad-justable parameters of the trial solution satisfying the governing equation of the nanobeam. The results are compared with the available results in the literature as well as numerical solution. The results indicate the remarkable accuracy of the present approach. The minimum initial gap and the critical free standing detachment length of the nano actuator that does not stick to the substrate due to the van der Waals attractions, as an important parameter in pull-in instability of the nano switches, is calculated. Utilizing the results of the PS-CS, the stress distribution inside the nano actuator is determined at the onset of the pull-in instability.
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Cicconofri, Giancarlo, and Antonio DeSimone. "A study of snake-like locomotion through the analysis of a flexible robot model." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, no. 2184 (December 2015): 20150054. http://dx.doi.org/10.1098/rspa.2015.0054.
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We examine the problem of snake-like locomotion by studying a system consisting of a planar inextensible elastic rod with adjustable spontaneous curvature, which provides an internal actuation mechanism that mimics muscular action in a snake. Using a Cosserat model, we derive the equations of motion in two special cases: one in which the rod can only move along a prescribed curve, and one in which the rod is constrained to slide longitudinally without slipping laterally, but the path is not fixed a priori (free-path case). The second setting is inspired by undulatory locomotion of snakes on flat surfaces. The presence of constraints leads in both cases to non-standard boundary conditions that allow us to close and solve the equations of motion. The kinematics and dynamics of the system can be recovered from a one-dimensional equation, without any restrictive assumption on the followed trajectory or the actuation. We derive explicit formulae highlighting the role of spontaneous curvature in providing the driving force (and the steering, in the free-path case) needed for locomotion. We also provide analytical solutions for a special class of serpentine motions, which enable us to discuss the connection between observed trajectories, internal actuation and forces exchanged with the environment.
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Rama Chandra Manohar, K., Somagani Upendar, V. Durgesh, B. Sandeep, Ksk Rahim mallik, Gurram Narendra Santosh Kumar, and Sk Hasane Ahammad. "Modeling and Analysis of Kaplan Turbine Blade Using CFD." International Journal of Engineering & Technology 7, no. 3.12 (July 20, 2018): 1086. http://dx.doi.org/10.14419/ijet.v7i3.12.17766.
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Fluid assumes a basic part in huge numbers of the items that we experience each day from clear applications, for example, water treatment frameworks and auto and flying machine streamlined features to limit pushing. CFD investigation which empowers item outline and examination in a virtual domain has revolutionized liquid progression via robotizing the arrangement, notwithstanding for issues that are numerically substantial. By recognizing physical powers and stream attributes that are in some cases difficult to gauge or pick up knowledge into, CFD arrangements can help an organization drastically enhance time to showcase. Kaplan Turbine is Reaction, Axial and Adjustable Flow Turbine. In this Project displaying of Kaplan Turbine Will be finished by expecting shaft diam-eter, sprinter breadth and profile of the edge in Cero parametric Software. Computational Fluid Dynamic Analysis will have performed by im-porting the model in to CFD Software Ansys Fluent by expecting Initial Boundary Conditions (i.e. bay weight and Velocity. By Fixing Blade Twist point and differing flexible edge. Diverse CAD models will draw, and variety of stream parameters can be created along the turbine (i.e. weight and Velocity) in Ansys familiar Software. The above examinations to be performed for various Blade bend points. Suit-capable charts will be created between stream parameters. By this we will be in the situation to judge, which point is the most best one (the most best edge is the one which changes over the entire weight and speed of the liquid into valuable shaft work).
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Hayley, Kevin, Alexis Valenza, Emma White, Bruce Hutchison, and Jens Schumacher. "Application of the Iterative Ensemble Smoother Method and Cloud Computing: A Groundwater Modeling Case Study." Water 11, no. 8 (August 9, 2019): 1649. http://dx.doi.org/10.3390/w11081649.
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Numerical groundwater modelling to support mining decisions is often challenging and time consuming. Simulation of open pit mining for model calibration or prediction requires models that include unsaturated flow, large magnitude hydraulic gradients and often require transient simulations with time varying material properties and boundary conditions. This combination of factors typically results in models with long simulation times and/or some level of numerical instability. In modelling practice, long run times and instability can result in reduced effort for predictive uncertainty analysis, and ultimately decrease the value of the decision-support modelling. This study presents an early application of the Iterative Ensemble Smoother (IES) method of calibration-constrained uncertainty analysis to a mining groundwater flow model. The challenges of mining models and uncertainty quantification were addressed using the IES method and facilitated by highly parallelized cloud computing. The project was an open pit mine in South Australia that required predictions of pit water levels and inflow rates to guide the design of a proposed pumped hydro energy storage system. The IES calibration successfully produced 150 model parameter realizations that acceptably reproduced groundwater observations. The flexibility of the IES method allowed for the inclusion of 1493 adjustable parameters and geostatistical realizations of hydraulic conductivity fields to be included in the analysis. Through the geostatistical realizations and IES analysis, alternative conceptual models of fractured rock aquifer orientation and connections could be conditioned to observation data and used for predictive uncertainty analysis. Importantly, the IES method out-performed finite difference methods when model simulations contained small magnitude numerical instabilities.
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Shen, I. Y. "Hybrid Damping Through Intelligent Constrained Layer Treatments." Journal of Vibration and Acoustics 116, no. 3 (July 1, 1994): 341–49. http://dx.doi.org/10.1115/1.2930434.
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This paper is to propose a viable hybrid damping design that integrates active and passive dampings through intelligent constrained layer (ICL) treatments. This design consists of a viscoelastic shear layer sandwiched between a piezoelectric constraining cover sheet and the structure to be damped. According to measured vibration response of the structure, a feedback controller regulates axial deformation of the piezoelectric layer to perform active vibration control. In the meantime, the viscoelastic shear layer provides additional passive damping. The active damping component of this design will produce adjustable and significant damping. The passive damping component of this design will increase gain and phase margins, eliminate spillover, reduce power consumption, improve robustness and reliability of the system, and reduce vibration response at high frequency ranges where active damping is difficult to implement. To model the dynamics of ICL, an eighth-order matrix differential equation governing bending and axial vibrations of an elastic beam with the ICL treatment is derived. The observability, controllability, and stability of ICL are discussed qualitatively for several beam structures. ICL may render the system uncontrollable or unobservable or both depending on the boundary conditions of the system. Finally, two examples are illustrated in this paper. The first example illustrates how an ICL damping treatment, which consists of an idealized, distributed sensor and a proportional-plus-derivative feedback controller, can reduce bending vibration of a semi-infinite elastic beam subjected to harmonic excitations. The second example is to apply an ICL damping treatment to a cantilever beam subjected to combined axial and bending vibrations. Numerical results show that ICL will produce significant damping.
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Russ, John C. "Monte Carlo Modelling of Secondary Electron Yield from Rough Surfaces." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 1 (August 12, 1990): 422–23. http://dx.doi.org/10.1017/s0424820100180860.
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Monte-Carlo programs are well recognized for their ability to model electron beam interactions with samples, and to incorporate boundary conditions such as compositional or surface variations which are difficult to handle analytically. This success has been especially powerful for modelling X-ray emission and the backscattering of high energy electrons. Secondary electron emission has proven to be somewhat more difficult, since the diffusion of the generated secondaries to the surface is strongly geometry dependent, and requires analytical calculations as well as material parameters. Modelling of secondary electron yield within a Monte-Carlo framework has been done using multiple scattering programs, but is not readily adapted to the moderately complex geometries associated with samples such as microelectronic devices, etc.This paper reports results using a different approach in which simplifying assumptions are made to permit direct and easy estimation of the secondary electron signal from samples of arbitrary complexity. The single-scattering program which performs the basic Monte-Carlo simulation (and is also used for backscattered electron and EBIC simulation) allows multiple regions to be defined within the sample, each with boundaries formed by a polygon of any number of sides. Each region may be given any elemental composition in atomic percent. In addition to the regions comprising the primary structure of the sample, a series of thin regions are defined along the surface(s) in which the total energy loss of the primary electrons is summed. This energy loss is assumed to be proportional to the generated secondary electron signal which would be emitted from the sample. The only adjustable variable is the thickness of the region, which plays the same role as the mean free path of the secondary electrons in an analytical calculation. This is treated as an empirical factor, similar in many respects to the λ and ε parameters in the Joy model.
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Schuschnig, Uwe, Ashley Norris Weigand, Manfred Keller, Klopfer Elisabeth, Axel Krüner, and Martin Luber. "R458 – Drug Delivery to the Sinuses- Basics and Aerosol Dynamics." Otolaryngology–Head and Neck Surgery 139, no. 2_suppl (August 2008): P198. http://dx.doi.org/10.1016/j.otohns.2008.05.617.
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Problem Drug delivery to the sinuses via aerosols appears to be a very difficult task, since the paranasal cavities are virtually non-vented cavities. However, there is a scientifically traceable approach to transport aerosol to the sinuses via pressure differences using so-called “vibrating” or “sonic” aerosols which suggests that pressure fluctuations increase aerosol diffusion and ventilate dead spaces by flow induction. Methods The influence of droplet size, vibration frequency and flow rate on drug delivery to the nasal and paranasal cavities was studied in a human nasal cast model (NC). One ml of a Levofloxacin solution (100 mg/ml) was aerosolized into the NC by a VibrENT prototype nebulizer generating a slow, high density aerosol (MMD = 3.7μm) via a perforated vibrating membrane in connection with an adjustable pulsation source. Results Total paranasal cavity deposition was highest (-20 % of label claim) configured with ostia of 1 and 3 mm in diameter and sinus volumes of 7, 12 and 23 ml when VibrENT was operated at flow rates below 3 1/min and a pulsation frequency of 36 Hz. Delivery efficiency decreased at higher frequencies, higher flow rates and with larger aerosol droplets. Omission of pulsation resulted in no paranasal deposition and a drop in nasal cavity deposition from more than 50% to about 6%. Drug deposition to the sinuses is also significantly (p<0.01) affected by the ostium diameter and sinus volume, being lowest (∼0.2 %) at a large ostium diameter (6 mm) and a low sinus volume (7 ml). Conclusion It is possible to deliver aerosol to the sinuses but physical boundary conditions like pulsation frequency, aerosol size and flow rate have to be considered for an efficient transport as well as sinus anatomy. PARI VibrENT addresses these requirements. Significance Efficient drug transport to the sinuses enables novel therapeutic approaches.
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Sutardi, S., and Agung E. Nurcahya. "Experimental Study on the Effect of Vortex Generator on the Aerodynamic Characteristics of NASA LS-0417 Airfoil." Applied Mechanics and Materials 758 (April 2015): 63–69. http://dx.doi.org/10.4028/www.scientific.net/amm.758.63.
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Boundary layer flow structure developing on an airfoil surfaces strongly affects drag and lift forces acting on the body. Many studies have been done to reduce drag, such as introducing surface roughness on the airfoil surface, gas injection, attachment of vortex generators, or moving surface on the airfoil. Previous results showed that the attachment of vortex generators has potentially been able to control boundary layer separation compared to other controlling devices. This study is focused on the evaluation of the effect of vortex generator attachment on the NASA LS-0417 airfoil profile as this profile is commonly used in wind turbine blade application. The models of this experimental study are NASA LS-0417 profiles, with and without vortex generator. The chord length of the profile is 110 mm, while the span is 210 mm. Profile of the vortex generator is a symmetrical profile of NACA 0012 configured in counter rotating and attached on the upper surface of the main profile. The chord length of the vortex generator is 7 mm with two different values of the height (h): 1 mm and 2 mm. The experiment was conducted in an open loop wind tunnel with maximum attainable freestream velocity of approximately 19 m/s and the turbulence intensity at the tunnel centerline is approximately 0.8%. The wind tunnel cross section is octagonal of 30 cm x 30 cm and of 45 cm to 60 cm adjustable length. The study was performed at two different freestream velocities of 12 m/s and 17 m/s corresponding with Reynolds numbers (Re) of 0.83 x 105 and 1.18 x 105 based on the airfoil chord length and the freestream velocity. Angle of attact (α) was varied from 0o to 24o. Drag and lift were measured using a force balance with measurement uncertainty of approximately 0.77% and 2.47% at measured drag of 0.65N and at measured lift of 0.202N, respectively. A flow visualization study using oil flow method was conducted to obtain qualitaive picture of flow structure on the airfoil surface. Results of this study showed that attachment of the vortex generator on the NASA LS-0417 profile has not been able to improve the profile performance compared to that of unmodified profile. There, however, seems Reynolds number effect on the airfoil performance flow conditions performed in this study. At lager Re, there is an increase in CL/CD of approximately 36% at angle of attack (α) 6o. Next, based on the flow visualization results, attachment of the 2mm vortex generator on the airfoil NASA LS-0417 surface results in an advancement of boundary layer separation at the two Re’s conducted in this study. Finally, the 2mm vortex generator accelerates airfoil stall at approximately 16o, while the 1mm vortex generator is relatively no effect on the airfoil stall angle.
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van der Voort, Jelle, and Michiel van der Stam. "Unlocking the full Potential of Lithography for Advanced Packaging." International Symposium on Microelectronics 2018, no. 1 (October 1, 2018): 000043–50. http://dx.doi.org/10.4071/2380-4505-2018.1.000043.
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Abstract Advanced Packaging technologies and applications are developing rapidly in order to support the ever increasing demand for integrating functionality in small and thin devices with low power consumption, high bandwidth, low latency- all at low cost of ownership. Lithography is the key enabling technology for developing and manufacturing such devices. Advanced Packaging processes, in particular Fan-Out, drive towards redistribution patterns with smallest feature sizes of a few micron today and towards 1 micron in the future. These feature sizes must be realized in production processes with multiple layers stacked on top of each other which need to be accurately aligned. In order to meet economic boundary conditions, routine operation on 300 mm wafers (possibly strongly warped) is required with high throughput. Kulicke & Soffa Liteq B.V. developed together with key partners, a novel Lithography system which is focused specifically to meet the challenging requirements of Advanced Packaging, both for current and future applications. The high quality optics used is capable to project the optimally sized reticle field with lowest possible aberrations on the wafer. The system includes Reticle Masking blades (REMA), which delivers high flexibility and high speed for multi-pattern jobs. The magnification of the optics is adjustable for optimal intra-field overlay performance. The reticle is illuminated by a high power UV laser. This novel setup creates many advantages for imaging, Cost of Ownership and throughput. The illumination and projection optics is combined with modern mechatronics to handle warped wafers with minimal overhead times. The design has a strong focus on contamination control. Wafer Edge Processing functions are integrated in the system to support the use of state-of-the-art plating processes. The modularity of the system architecture makes it possible to extend functionality and performance into the future. In this paper we will introduce the novel LITEQ 500 projection stepper, present imaging results and demonstrate the flexibility and high throughput potential of reticle masking for complex multi-pattern jobs.
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Alboussière, Thierry, and Yanick Ricard. "Rayleigh–Bénard stability and the validity of quasi-Boussinesq or quasi-anelastic liquid approximations." Journal of Fluid Mechanics 817 (March 16, 2017): 264–305. http://dx.doi.org/10.1017/jfm.2017.108.
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The linear stability threshold of the Rayleigh–Bénard configuration is analysed with compressible effects taken into account. It is assumed that the fluid under investigation obeys a Newtonian rheology and Fourier’s law of thermal transport with constant, uniform (dynamic) viscosity and thermal conductivity in a uniform gravity field. Top and bottom boundaries are maintained at different constant temperatures and we consider here mechanical boundary conditions of zero tangential stress and impermeable walls. Under these conditions, and with the Boussinesq approximation, Rayleigh (Phil. Mag., vol. 32 (192), 1916, pp. 529–546) first obtained analytically the critical value $27\unicode[STIX]{x03C0}^{4}/4$ for a dimensionless parameter, now known as the Rayleigh number, at the onset of convection. This paper describes the changes of the critical Rayleigh number due to the compressibility of the fluid, measured by the dimensionless dissipation parameter ${\mathcal{D}}$ and due to a finite temperature difference between the hot and cold boundaries, measured by a dimensionless temperature gradient $a$. Different equations of state are examined: ideal gas equation, Murnaghan’s model (often used to describe the interiors of solid but convective planets) and a generic equation of state with adjustable parameters, which can represent any possible equation of state. In the perspective to assess approximations often made in convective models, we also consider two variations of this stability analysis. In a so-called quasi-Boussinesq model, we consider that density perturbations are solely due to temperature perturbations. In a so-called quasi-anelastic liquid approximation model, we consider that entropy perturbations are solely due to temperature perturbations. In addition to the numerical Chebyshev-based stability analysis, an analytical approximation is obtained when temperature fluctuations are written as a combination of only two modes, one being the original symmetrical (between top and bottom) mode introduced by Rayleigh, the other one being antisymmetrical. The analytical solution allows us to show that the antisymmetrical part of the critical eigenmode increases linearly with the parameters $a$ and ${\mathcal{D}}$, while the superadiabatic critical Rayleigh number departs quadratically in $a$ and ${\mathcal{D}}$ from $27\unicode[STIX]{x03C0}^{4}/4$. For any arbitrary equation of state, the coefficients of the quadratic departure are determined analytically from the coefficients of the expansion of density up to degree three in terms of pressure and temperature.
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Ye, Hong Ling, Xing Zhang, and Nan Wei. "Topology Optimization Design of Adjustable Thermal Expansion Metamaterial Based on Independent Continuous Variables." International Journal of Applied Mechanics, May 12, 2021, 2150032. http://dx.doi.org/10.1142/s1758825121500320.
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This paper presents a topology optimization method to construct adjustable thermal expansion metamaterials. The negative thermal expansion (NTE) and extreme positive thermal expansion (EPTE) microstructures are designed, respectively. First, the effective elastic modulus and the effective thermal expansion coefficient of microstructure are derived by the multiscale asymptotic homogenization theory based on the periodic characteristics of the metamaterial. Second, a topology optimization model aiming at extreme thermal expansion coefficient is established and solved based on independent continuous topological variables, which is subjected to the effective elastic modulus and structure weight fraction. Then a cross-precision progressive optimization method is provided to save the computation time and make a smoother boundary. In addition, the specific topological feature for the initial configuration is discussed. Five holes are the necessary condition to obtain adjustable thermal expansion metamaterials for four-axisymmetric structures. Finally, a transformation strategy from NTE to EPTE and the change law of thermal expansion coefficient bounds with effective elastic modulus are studied. Numerical examples show that the NTE and EPTE can be designed in the range of effective elastic modulus from 0.01 to 0.05. The proposed method provides a reference for the novel configuration design of metamaterials.
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"The turbulent boundary-layer rough-wall pressure spectrum at acoustic and subconvective wavenumbers." Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences 415, no. 1848 (January 8, 1988): 141–61. http://dx.doi.org/10.1098/rspa.1988.0007.
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The rough-wall turbulent boundary-layer wall pressure spectrum differs from that on a smooth wall because the strengths of the turbulence Reynolds stresses responsible for the pressure fluctuations are increased by surface roughness, and because the near fields of those enhanced pressure sources are redistributed in wavenumber by diffraction by the roughness elements. In this paper, analyses are performed that indicate that, except at very low frequencies, the diffractive component dominates the spectrum in the low-wavenumber and acoustic domains. The diffraction calculations are performed exactly for a plane wall roughened by a distribution of rigid hemispherical bosses, and a comparison is made with corresponding predictions obtained when only the first non-trivial term is retained in an expansion of the rough-wall boundary condition about that for a plane wall. These calculations take no account of interstitial flows and possible wake formation by the roughness elements, and an empirical model of the spectrum is proposed to incorporate these effects and recommended for use in applications. The values of adjustable coefficients that enter the proposed formula are estimated by reference to published experimental data on the radiation of sound by a rough-wall boundary layer. Such data are incomplete, however, and further experiments need to be performed to validate the model.
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Xing, Haojie, Xiaojun Li, Hongjing Li, Zhinan Xie, Shaolin Chen, and Zhenghua Zhou. "The Theory and New Unified Formulas of Displacement-Type Local Absorbing Boundary Conditions." Bulletin of the Seismological Society of America, December 8, 2020. http://dx.doi.org/10.1785/0120200155.
Full textAbstract:
ABSTRACT A series of classical absorbing boundary conditions (ABCs), including paraxial-approximation ABCs, Liao’s multi-transmitting formula (MTF), Higdon ABCs, and some other related techniques, have the common feature that the motion of an arbitrary artificial boundary node at each timestep is directly predicted from the motions of some adjacent nodes at several previous timesteps. They are expressed in somewhat equivalent forms, contain similar control parameters, and have comparable accuracy and stability in numerical simulations. This study develops a theoretical framework called displacement-type (a more exact name would be “prediction-type” or “extrapolation-type”) local ABCs to merge these boundary conditions. The idea of this theory mainly originates from the versatility of MTF, which uses a unified formula to approximate the propagation of outgoing waves through each boundary node. This idea can be generalized to other displacement-type local ABCs to unify their expressions and to optimize their applications. These ABCs have two basic control parameters; one is the boundary order, and the other is adjustable computational wave velocities. Considering the poor performance of paraxial ABCs and the slight imperfections in MTF and Higdon ABCs, we propose two new unified formulas to be the starting points of expressing, evaluating, and applying displacement-type local ABCs. One formula is an optimized MTF by introducing various computational wave velocities. The other formula is a generalized Higdon boundary formula, which is established in a unified local coordinate and uses the adjustable computational wave velocities. The rule of choosing boundary parameters for the absorption of acoustic and elastic waves is discussed in detail. Numerical tests validate the proposed theory and formulas. Issues on numerical stability are briefly reviewed and tested in simulation examples. This is still an active research topic related to displacement-type local ABCs.
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Zhang, Hao, Xiaoyu Zhang, and Min Zhu. "Experimental Investigation of Thermoacoustic Instabilities for a Model Combustor With Varying Fuel Components." Journal of Engineering for Gas Turbines and Power 134, no. 3 (December 30, 2011). http://dx.doi.org/10.1115/1.4004212.
Full textAbstract:
In this study, a combustion facility was constructed that includes a flexible fuel supply system to produce synthesis gas using a maximum of three components. The rig with lean premixed burner is able to operate at up to five bars. The length of the inlet plenum and the outlet boundary conditions of the combustion chamber are adjustable. Experiments were carried out under a broad range of conditions, with variations in fuel components including hydrogen, methane and carbon monoxide, equivalence ratios, thermal power and boundary conditions. The dynamic processes of self-excited combustion instabilities with variable fuel components were measured. The mechanisms of coupling between the system acoustic waves and unsteady heat release were investigated. The results show that instability modes and flame characteristics were significantly different with variations in fuel components. In addition, the results are expected to provide useful information for the design and operation of stable syngas combustion systems.
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Eichler, Christian, and Thomas Sattelmayer. "Experiments on Flame Flashback in a Quasi-2D Turbulent Wall Boundary Layer for Premixed Methane-Hydrogen-Air Mixtures." Journal of Engineering for Gas Turbines and Power 133, no. 1 (September 14, 2010). http://dx.doi.org/10.1115/1.4001985.
Full textAbstract:
Premixed combustion of hydrogen-rich mixtures involves the risk of flame flashback through wall boundary layers. For laminar flow conditions, the flashback mechanism is well understood and is usually correlated by a critical velocity gradient at the wall. Turbulent transport inside the boundary layer considerably increases the flashback propensity. Only tube burner setups were investigated in the past, and thus turbulent flashback limits were only derived for a fully developed Blasius wall friction profile. For turbulent flows, details of the flame propagation in proximity to the wall remain unclear. This paper presents results from a new experimental combustion rig, apt for detailed optical investigations of flame flashbacks in a turbulent wall boundary layer developing on a flat plate and being subject to an adjustable pressure gradient. Turbulent flashback limits are derived from the observed flame position inside the measurement section. The fuels investigated cover mixtures of methane, hydrogen, and air at various mixing ratios. The associated wall friction distributions are determined by Reynolds-averaged Navier-Stokes (RANS) computations of the flow inside the measurement section with fully resolved boundary layers. Consequently, the interaction between flame back pressure and incoming flow is not taken into account explicitly, in accordance with the evaluation procedure used for tube burner experiments. The results are compared with literature values, and the critical gradient concept is reviewed in light of the new data.
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Chen, Yu, Zhichun Yang, Zhaolin Chen, Kui Li, and Shengxi Zhou. "Design, modeling, and experiment of a multi-bifurcated cantilever piezoelectric energy harvester." Journal of Intelligent Material Systems and Structures, March 15, 2021, 1045389X2110014. http://dx.doi.org/10.1177/1045389x211001456.
Full textAbstract:
A multi-bifurcated cantilever piezoelectric energy harvester (BCPEH) is designed and verified to achieve a wide and adjustable response frequency band. The theoretical model is derived based on the Euler-Bernoulli beam theory and continuity boundary conditions to investigate the dynamic response of the BCPEH. The displacement frequency response function and the voltage frequency response function of the BCPEH are deduced based on the Galerkin method, and the theoretical results of a typical multi-bifurcated cantilever piezoelectric energy harvester, the Y-shaped BCPEH, are verified by the finite element method (FEM) and experiments. In addition, by comparing experimental output power of the Y-shaped BCPEH with that of the traditional cantilever-based piezoelectric energy harvester with the same mass of the bifurcated part at the beam-tip, it demonstrates that the Y-shaped BCPEH has a wider operational frequency band. Moreover, it is found that the Y-shaped BCPEH can be designed with an asymmetric configuration to adjust its response frequency distribution. The number of resonant frequencies and the output power of the asymmetric Y-shaped BCPEH are higher than that of the symmetric Y-shaped BCPEH. And the Y-shaped BCPEH has even better performance than L-shaped BCPEH. This study provides a new design concept for enhanced energy harvester.