Lateral Separation Distance Research Articles

Enhancing cell separation in a hybrid spiral dielectrophoretic microchannel: Numerical insights and optimal operating conditions.

Reliable separation of circulating tumor cells from blood cells is crucial for early cancer diagnosis and prognosis. Many conventional microfluidic platforms take advantage of the size difference between particles for their separation, which renders them impractical for sorting overlapping-sized cells. To address this concern, a hybrid inertial-dielectrophoretic microfluidic chip is proposed in this work for continuous and single-stage separation of lung cancer cell line A549 cells from white blood cells of overlapping size. The working mechanism of the proposed spiral microchannel embedded with planar interdigitated electrodes is validated against the experimental results. A numerical investigation is carried out over a range of flow conditions and electric field intensity to determine the separation efficiency and migration characteristics of the cell mixture. The results demonstrate the unique capability of the proposed microchannel to achieve high-throughput separation of cells at low applied voltages in both vertical and lateral directions. A significant lateral separation distance between the CTCs and the WBCs has been achieved, which allows for high-resolution and effective separation of cells. The separation resolution can be controlled by adjusting the strength of the applied electric field. Furthermore, the results demonstrate that the lateral separation distance is maximum at a voltage termed the critical voltage, which increases with the increase in the flow rate. The proposed microchannel and the developed technique can provide valuable insight into the development of a tunable and robust medical device for effective and high-throughput separation of cancer cells from the WBCs.

An extended non-lane-discipline-based continuum model through driver behaviors for analyzing multi-traffic flows

Non-lane-discipline environment has an essential role in driver behavior. In this environment, drivers change their driving behavior through the traffic flow, causing perturbations and complexity. To evaluate the effect of driver behavior under non-lane-based discipline on the traffic flow, the present study investigated the physical and dynamic characteristics of drivers on an urban highway in Iran for each vehicle class based on the lateral separation distance (LSD) parameter and strength influence factor. Then, an extended non-lane-discipline-based continuum model was proposed for different traffic conditions. Further, the proposed model was simulated using the adjusted upwind scheme for lane analysis. The field data results indicated that non-lane-based discipline has an important role in changing car drivers’ driving behaviors from typical and sluggish to aggressive behavior compared with lane-based discipline. Moreover, under maximum LSD, due to an increase in the lateral distance, car drivers became aggressive. In addition, there was a high stability region in traffic flow due to the positive effect of driver behavior, under non-lane-discipline environment, on the critical region of density where there was an increase in the traffic flow. However, in the free flow similar to jam density, the effect of the behavior on traffic flow was insignificant. Furthermore, driver behavior under non-lane-based heterogeneous traffic conditions could improve traffic flow. For the case of the car’s traffic flow regarding aggressive behavior under non-lane-based discipline, the capacity of lane reached 1.18–1.45 times higher in cars than that in sluggish behavior under lane-based discipline, respectively. Accordingly, the capacity of the lane was observed to be 1.50–3.41 times higher than that of trucks as the truck proportions decreased from 80% to 0% due to different LSD parameters and strength influence factors. Thus, the extended continuum model can appropriately predict traffic flow considering driver behavior under non-lane-based discipline.

Statistical Models of Interactions between Vehicles during Overtaking Maneuvers

A practical challenge facing the adoption of self-driving vehicles is the complex influence of the lateral dimension in vehicle traffic. This phenomenon has received little attention in the literature and few quantitative descriptions of interactions between vehicles are available for model validation. This paper proposes an analysis of the kinematic variables describing vehicle interactions on both axes during overtaking maneuvers using linear as well as nonlinear and nonparametric models based on real-world highway data. The principal findings are as follows: (a) a mutual influence between pairs of vehicles, especially at small lateral separation distances; (b) the higher the longitudinal velocity, the greater the lateral distances, no doubt to avoid collisions; and (c) lateral accelerations that tend to narrow lateral distance are associated with longitudinal accelerations that tend to widen it. These results are consistent across the different models applied and also with previous studies.

A wind tunnel investigation of yawed wind turbine wake impacts on downwind wind turbine performances and wind loads

In the current work we experimentally explored yawed wind turbine wake impacts on downwind wind turbine performances and wind loads. The lab-scale wind turbine model with a rotor diameter ( D) of 0.442 m and a height of 1 m (=2.26 D) was installed in a closed-circuit boundary layer wind tunnel (test section: 15 m long × 3.6 m wide × 2.0 m high) of the Research Institute for Applied Mechanics (RIAM) of Kyushu University. Power performance tests were initially conducted with a single rotor in isolation in order to characterize a rotor’s power output in stand-alone conditions. A detailed comparison of the tests revealed that the power output decreased rapidly as the yaw angle (γ) increased. It is presumed that the power output decrease in yawed cases is mainly due to the decrease in the effective rotor area and the change in the angle of the incoming wind flow with respect to the wind turbine blade. Next, using two wind turbine models aligned with the dominant inflow direction, the merging wakes behaviors caused by three different lateral separation distances were tested: (a) Case 1 ( y = 0), (b) Case 2 ( y = 0.5 D), and (c) Case 3 ( y = 1 D). Here, the separation distance between the two wind turbine models was fixed at 6 D in all cases. Extremely large power output deficits of 46%–76% were seen in the Case 1 configuration. This is mainly due to the significant wake velocity deficits induced by the upwind wind turbine model. In the Case 2 configuration with γ values of 20° and 30°, a significant increase in the power output of the downwind wind turbines was observed. Similar to Case 1 configuration, these results are considered to be mainly due to the upwind turbine-induced wake velocity deficits and wake deflection. Finally, in the Case 3 configuration, no significant difference was found in all of the results, and the tendency was almost the same. We show that the wake velocity deficits induced by the upwind wind turbine model had almost no effect on the power output of the downwind wind turbine model. We evaluated the total power output of the two turbines. As a result, in the Case 2 configuration with 20° yaw angle, the total power output of the two wind turbine models was the highest due to the increase in the power output of the downwind wind turbine model. In order to investigate the main cause of the significant increase in the power output of the downwind wind turbine model at 20° and 30° yaw angles in the Case 2 configuration, we measured the lateral wind speed distribution at the 6 D position on the downwind side of the upwind wind turbine model by using the ultrasonic anemometer. As a results, it was clarified that the peak of the wake velocity deficits induced by the upwind wind turbine model is clearly shifted away from the downwind turbine such that it experiences a smaller deficit due to wake steering. Also, with wake steering the upwind turbine-induced wake velocity deficits may be smaller due to the reduction in rotor area. Finally, it is extremely important to understand the wind load acting on the downwind wind turbine model operating within the wake region induced by the upwind yawed wind turbine model when the maximum power output is generated. It can be seen that as the yaw angle of the upwind wind turbine model increased, the power output generated by the downwind wind turbine model and the streamwise wind load acting on it also increased. However, it was also clarified that the streamwise wind load acting on the downwind wind turbine model in this situation did not exceed the stand-alone value.

On the Stability of Particle–Particle Interaction during Gravitational Settling

The elevated energy demand and high dependency on fossil fuels have directed researchers’ attention to promoting and advancing hydraulic fracturing (HF) operations for a sustainable energy future. Even though previous studies have demonstrated that the proppant suspension and positioning in slickwater play a vital role during the shut-in stage of the HF operations, minimal experimental work has been conducted on the fundamental proppant–proppant interaction mechanisms, especially a complete mapping of the interactions. This study utilizes high-speed imaging to provide a 2D space- and time-resolved investigation of two-particle (proppant models: 2 mm Ø, 2.6 g·cm−3) interactions during gravitational settling in different initial spatial configurations and rheological properties. The mapping facilitates the identification of various interaction regimes and newly observed particle trajectories. Pure water results at a settling particle Reynolds number (Rep) ~ 470 show an unstable particle–particle interaction regime characterized by randomness while altering pure water to a 25% (v/v) water–glycerin mixture (Rep ~ 200) transitions an unstable interaction to a stable prominent repulsion regime where particles’ final separation distance can extend up to four times the initial distance. This indicates the existence of Rep at which the stability of the interactions is achieved. The quantified trajectories indicate that when particles are within minimal proximity, a direct relation between repulsion and Rep exists with varying repulsion characteristics. This was determined by observing unique bottle-shaped trajectories in the prominent repulsion regimes and further highlighted by investigating the rate of lateral separation distance and velocity characteristics. Additionally, a threshold distance in which the particles do not interact (or negligibly interact) and settle independently seems to exist at the normalized 2D lateral separation distance.

Aerodynamic interaction between tandem overlapping propellers in eVTOL airplane mode flight condition

The architecture of new electric aircraft concepts (eVTOLs) for urban air mobility is typically characterised by multi-propellers in tandem configurations with different degrees of rotor disks overlapping. Consequently, the aerodynamic interaction between front propellers slipstream and rear propellers represents one of the key-phenomena which influenced the performance and design of these novel aircraft configurations. A wind tunnel campaign was performed to investigate the aerodynamic interaction between two propellers in tandem with particular focus to airplane mode flight condition of eVTOLs. A systematic series of tests, including thrust and torque measurements and stereoscopic Particle Image Velocimetry (PIV) surveys, were performed on two co-rotating propellers models. The axial distance was fixed during tests while the lateral separation distance was changed to evaluate the effects of aerodynamic interaction on propellers performance and flow field due to different propeller disks overlapping. Load measurements pointed out a remarkable loss of rear propeller thrust occurring when the degree of overlapping between rotors disks is increased. On the other hand, spectral analysis of measured loads signals showed a higher amount of thrust fluctuations amplitude occurring when the degree of overlapping between propeller disks is partial. Stereo PIV results provided insights on the effects of aerodynamic interaction on rear propeller inflow and wake flow physics. Moreover, numerical simulations performed using a mid-fidelity aerodynamic solver based on vortex particle method (VPM) provided enhanced insights to comprehend the interacting flow mechanisms between front propeller slipstream and rear propeller blades responsible for the detrimental effects observed on rear propeller performance.

Seismic Pounding Response of Neighboring Structure using Various Codes with Soil-Structure Interaction effects: Focus on Separation Gap

Due to the high cost and less availability of land, the buildings are constructed adjacent to each other with a significantly smaller separation gap. Whenever seismic forces act on adjacent structures, they collide and cause significant structural and architectural damage. Soil-Structure Interaction (SSI) effects cause more complications in the adjacent structures. This paper assesses the gap distance between RC bare frame adjacent structures of varying heights in medium and soft soil with and without SSI to avoid the pounding effect of an earthquake. The main objectives are to find the separation distance between adjacent buildings by the provisions of FEMA 356, IS 1893 (Part 1):2002, IS 1893 (Part 1):2016 and EN 1998-1:2004. The separation gap between different codes was then compared to determine the minimum separation required to prevent pounding between the structures. The maximum lateral displacement on the roof and the time period of the adjacent buildings are compared with and without SSI. There is a significant increase in lateral displacement, separation distance, and time period considering SSI. It is found that the Indian code overestimates the separation distance. Thus, this study guides structural engineers to maintain a minimum separation distance between buildings erected on medium and soft soils in high seismic zones of India. Doi: 10.28991/CEJ-2022-08-02-09 Full Text: PDF

On the deviation of mean pressure coefficients in wind loading standards for a low-rise, gable-roofed building with boundary walls

The provisions in wind loading standards routinely overlook the influence of nearby small-size objects on wind loads of low-rise buildings. One such object is boundary walls that significantly modify the surrounding wind field thereby affecting the wind loading of low-rise buildings. To investigate this phenomenon, four low-rise, gable-roofed buildings: one with and three without boundary walls were tested in a boundary layer wind tunnel. The calculated external pressure coefficients (C¯p) were subsequently compared with the provisions given in ASCE 7 (2016), NBCC (2015), EN 1991-1-4 (2005), and AS/NZS 1170.2 (2011). The comparison showed a good agreement for the C¯p calculated using ASCE 7-16 (2016) and AS/NZS 1170.2 (2011) for the building without boundary walls with those of the wind tunnel test. However, all wind loading standards overestimated C¯p of the buildings with boundary walls because they did not account for the shielding effect of boundary walls. The largest discrepancies in magnitude and distribution of wind pressure were observed on the windward wall and the upwind roof slope. These modifications showed a strong dependency on the upstream and lateral separation distances between the building and the boundary walls.

Collision Risk Modeling and Analysis for Lateral Separation to Support Unmanned Traffic Management.

This article investigates the utility and extension of well-established collision risk modeling approaches for lateral separation standard development for unmanned traffic management and network design. The applicability of standard assumptions and simplifications made in the manned environment to a scaled-down unmanned aerial systems (UAS) environment is first investigated. The results are used to derive an iso-risk surface that shows the tradeoff between separation distance and navigation performance for a given risk level or target level of safety. The model is then extended to consider collision risk from one to tracks, and finally to determine the total collision risk and the related iso-risk surfaces for systems of parallel tracks with additions to account for the effects of more than two parallel tracks. The extended model is applied to a case study where airspace design for an urban area is conducted via maximization of the number of same-direction parallel tracks while meeting the target level of safety. The results suggest that lateral separation distances less than 100 m are achievable for small UAS, and that the separation standards are mostly affected by the proportion of poorly navigatingaircraft.

Enhancement in MS‐based peptide detection by microfluidic free‐flow zone electrophoresis

Matrix components are known to significantly alter the ionization of a target analyte in ESI-based measurements particularly when working with complex biological samples. This issue however may be alleviated by extracting the analyte of interest from the original sample into a relatively simple matrix compatible with ESI mass-spectrometric analysis. In this article, we report a microfluidic device that enables such extraction of small peptide molecules into an ESI-compatible solvent stream significantly improving both the sensitivity and reproducibility of the measurements. The reported device realizes this analyte extraction capability based on the free-flow zone electrophoretic fractionation process using a set of internal electrodes placed across the width of the analysis channel. Employing lateral electric fields and separation distances of 75 V/cm and 600µm, respectively, efficient extraction of the model peptide human angiotensin II was demonstrated allowing a reduction in its detection limit by one to three orders of magnitude using the ESI-MS method. The noted result was obtained in our experiments both for a relatively simple specimen comprising DNA strands and angiotensin II as well as for human serum samples spiked with the same model peptide.

All-fiber mode converter based on LP11 coupled-mode for mode division multiplexing systems

In this paper, two LP11 mode converters were reported and compared; one, employing two-mode conventional step index fiber (CSIF) and the other, using two identical multi-step two-mode fiber (MSTMF). In each case, the two fibers constituting the proposed devices were laterally misaligned. With the appropriate adjustments of the lateral displacements (h) and separation distance (d) between the axis of the identical CSIF and MSTMF, all-fiber converters with the coupling efficiencies of 69% and 94% were achieved, respectively. The performance of the two devices is compared in terms of the coupling efficiency (CE) and mode purity (MP) at the outputs. The results based on the coupling power indicate that MSTMF-based device offers higher CE and batter MP than the CSIF-converter. An MP of 84% and 58.8% were respectively determined for the MSTMF and CSIF converters. Therefore, the MSTMF device can be more suitable in mode conversion during mode division multiplexing (MDM) systems due to its high CE and MP.

Large-eddy simulation of the flow in Z-Shape duct

A numerical study is conducted of the transient flow in a z-shape three-dimensional duct using large-eddy simulation (LES) with dynamic eddy viscosity subgrid-scale (SGS) model with a fully structured grid system. The numerical results of the velocity profiles are quantitatively validated against experimental data for z-shape ducts with various lateral separation distance configurations. The framework of the current LES model has been studied and discussed and the performance of LES in predicting the flow in z-shape ducts as a function of separation distances was evaluated. LES predictions of the mean flow velocity profiles are in good agreement (within the experimental uncertainty) with experimental data for the investigated wide range of l/d configurations. This is attributed to the well-resolved large-scale flow structures. Some slight over-predictions and under-predictions were found at certain separation distances. These numerical errors are due to the limited modeling approach to predict small eddies structures with the current SGS model. The main key features of the flow after the first elbow are also identified as separation and re-attachment regions. Some discrepancies are identified for lateral separation distances at sections x/d = 3 and x/d = 5 inside the flow transition regions. These discrepancies are believed to be inherited from the upstream flow numerical errors that arise in the non-uniform flow mixing regions. The potential remedy includes applying finer mesh resolution and/or higher order spatial discretization to accurately resolve the local velocity gradients and the complex flow structures.

Modelling vehicular behaviour using trajectory data under non-lane based heterogeneous traffic conditions

The present study aims to understand the interaction between different vehicle classes using various vehicle attributes and thereby obtain useful parameters for modelling traffic flow under non-lane based heterogeneous traffic conditions. To achieve this, a separate coordinate system has been developed to extract relevant data from vehicle trajectories. Statistical analysis results show that bi-modal and multi-modal distributions are accurate in representing vehicle lateral placement behaviour. These distributions help in improving the accuracy of microscopic simulation models in predicting vehicle lateral placement on carriageway. Vehicles off-centeredness behaviour with their leaders have significant impact on safe longitudinal headways which results in increasing vehicular density and capacity of roadway. Another interesting finding is that frictional clearance distance between vehicles influence their passing speed. Analysis revealed that the passing speeds of the fast moving vehicles such as cars are greatly affected by the presence of slow moving vehicles. However, slow moving vehicles does not reduce their speeds in the presence of fast moving vehicles. It is also found that gap sizes accepted by different vehicle classes are distributed according to Weibull, lognormal and 3 parameter log logistic distributions. Based on empirical observations, the study proposed a modified lateral separation distance factor and frictional resistance factor to model the non-lane heterogeneous traffic flow at macro level. It is anticipated that the outcomes of this study would help in developing a new methodology for modelling non-lane based heterogeneous traffic.

Operational Evaluation of Advisory Bike Lane Treatment on Road User Behavior in Ottawa, Canada

The City of Ottawa has been investigating design solutions to facilitate the addition of cycling facilities, while maintaining parking, to roadways with limited right-of-ways. A pilot project to install advisory bike lanes was initiated. The purpose of this study is to determine how new pavement markings (advisory bike lanes) influence cyclist and motorist interactions and positioning, especially with respect to the distance between motorists and cyclists when passing. The study presents a before–after evaluation of two contrasting pavement indications. Video data were collected in two phases (pre- and post- treatment); each phase consisted of two different days. A number of safety performance parameters were used to assess whether safer conditions existed after the new treatment was installed: (i) the lateral distance between the motor vehicle and cyclist, (ii) the lateral distance between the cyclist and curbside edge/cyclist and buffer edge line, and (iii) the speed of the cyclist and motor vehicle. The findings indicate that the advisory bike lanes created more favorable conditions for cyclist safety and for motor vehicle compliance. These findings are (i) motorists passed cyclists with a greater lateral separation distance, (ii) cyclists positioned themselves further from parking edge line and rode in the middle of the bike lane, (iii) motor vehicle traveling speed decreased (the 85th percentile speed decreased by 5.2% after the installation of the advisory bike lane), and (iv) average cyclist speed increased (the average cyclist speed increased by 7.7% after the installation of the advisory bike lane).

A numerical‐analytical methodology for acquiring the electrical force of carbon nanotube–based nanoactuator assuming an out‐of‐plane electrodes arrangement

AbstractIn this paper, we develop a simple expression to evaluate the electric force acting on a carbon nanotube–(CNT) based nanoactuator assuming a nonparallel actuating plates (out‐of‐plane) arrangement. The actuating force is initiated by the asymmetry of the resultant electric fringing fields caused mainly due to the nonparallel electrodes arrangement. The nanoactuator is designed based on a CNT flexible electrode (nonstationary) and 2 symmetrically located actuating stationary rectangular shaped out‐of‐plane plates. The resultant electric force is mathematically approximated from the outcomes of a planar (2‐D) numerical solution of the electric problem via a finite element–based numerical analysis. The influence of the design geometrical parameters on the resultant electric force are examined. Several key design parameters were inspected: the width and thickness of the stationary actuating electrodes, the radius of the flexible electrode (the CNT), and the lateral and vertical separation distances between the movable and grounded electrodes. Through several simulations, we show the effect of the lateral and vertical offsets as well as the electrodes thickness in the optimization of the performance of the nanoactuator assuming such nonparallel plates actuating configuration. We also simulate the effect on the resultant actuating force level with the electrode thickness as well as the electrodes lateral separation distance.

Hydrokinetic turbine array characteristics for river applications and spatially restricted flows

Multiple hydrokinetic turbines in three array configurations were characterized computationally by employing Reynolds Averaged Navier-Stokes equations. The simulations were conducted for pre-existing turbines operating at their optimum power coefficient of 0.43 which was obtained by design and optimization process. Mechanical power for two adjacent units was predicted for various lateral separation distances. An additional two-by-two turbine array was studied, mimicking a hydro-farm. Numerical simulations were performed using actual physical turbines in the field rather than using low fidelity models such as actuator disk theory. Steady state simulations were conducted using both Coupled and SIMPLE pressure-velocity solvers. Steady three dimensional flow structures were calculated using the k-ω Shear Stress Transport (SST) turbulence model. At a lateral separation distance of 0.5Dt, the turbines produced an average 86% of the peak power a single turbine producing. Interaction effects at lateral separation distances greater than 2.5Dt were negligible. The wake interaction behind the upstream turbines causes a significant performance reduction for downstream turbines within 6Dt longitudinal spacing. Downstream turbines employed for the present study performed around 20% or less of a single unit turbine performance for the same operating conditions. Downstream turbines yielded comparable reductions in power to that of experimental results.

Role of the source to building lateral separation distance in petroleum vapor intrusion

The adoption of source to building separation distances to screen sites that need further field investigation is becoming a common practice for the evaluation of the vapor intrusion pathway at sites contaminated by petroleum hydrocarbons. Namely, for the source to building vertical distance, the screening criteria for petroleum vapor intrusion have been deeply investigated in the recent literature and fully addressed in the recent guidelines issued by ITRC and U.S.EPA. Conversely, due to the lack of field and modeling studies, the source to building lateral distance received relatively low attention. To address this issue, in this work we present a steady-state vapor intrusion analytical model incorporating a piecewise first-order aerobic biodegradation limited by oxygen availability that accounts for lateral source to building separation. The developed model can be used to evaluate the role and relevance of lateral vapor attenuation as well as to provide a site-specific assessment of the lateral screening distances needed to attenuate vapor concentrations to risk-based values. The simulation outcomes showed to be consistent with field data and 3-D numerical modeling results reported in previous studies and, for shallow sources, with the screening criteria recommended by U.S.EPA for the vertical separation distance. Indeed, although petroleum vapors can cover maximum lateral distances up to 25–30m, as highlighted by the comparison of model outputs with field evidences of vapor migration in the subsurface, simulation results by this new model indicated that, regardless of the source concentration and depth, 6m and 7m lateral distances are sufficient to attenuate petroleum vapors below risk-based values for groundwater and soil sources, respectively. However, for deep sources (>5m) and for low to moderate source concentrations (benzene concentrations lower than 5mg/L in groundwater and 0.5mg/kg in soil) the above criteria were found extremely conservative as the model results indicated that for such scenarios the lateral screening distance may be set equal to zero.

Interference effects on the Kelvin wake of a catamaran represented via a hull-surface distribution of sources

Wave-interference effects on the far-field waves created by a catamaran, with identical twin hulls of length L at a lateral separation distance S, that advances at constant speed V along a straight path in calm water of large depth are considered. Systematic computations are performed for 125 Froude numbers Fs≡V/gS (where g denotes the acceleration of gravity) within the range 0.4≤Fs≤3.5, 25 hull spacings s≡S/L within the range 0.2≤s≤0.8, and seven simple mathematically-defined hulls that correspond to a broad range of main hull-shape parameters (beam/length, draft/length, beam/draft, waterline entrance angle), i.e. for 21,875 distinct cases in all. The two dominant wake angles ψi and ψo that correspond to the ray angles ψ=±ψi and ψ=±ψo where the largest divergent waves are found within the Kelvin wake −ψK≤ψ≤ψK with ψK≈19∘28′ are determined numerically via a realistic yet practical method. This practical method, used previously for monohull ships, is based on the numerical determination of the two major peaks of the amplitude function in the Fourier-Kochin representation of far-field ship waves, evaluated via the Hogner approximation and the stationary-phase approximation. The computations show that the hull shape only has a relatively small influence on the wake angles ψi and ψo associated with the dominant waves. A useful practical consequence of this numerical finding is that the two wake angles ψi and ψo can be estimated, without computations, for general catamarans in terms of the Froude number Fs and the hull spacing s via simple analytical approximations, obtained here via parametric computations. The computations also show that lateral interference effects are dominant if s and/or Fs are sufficiently large, i.e. for ‘wide’ and/or ‘fast’ catamarans. Moreover, the computations reported here for catamarans represented via hull-surface distributions of sources show that the basic two-point wavemaker model of interference between the waves created by the twin bows of a catamaran is realistic for wide and/or fast catamarans. However, wave-interference effects are more complicated if both s and Fs are small, i.e. for ‘narrow slow’ catamarans. The numerical analyses of dominant waves considered earlier for monohull ships and here for catamarans show that, although the amplitudes of the waves created by a ship are strongly influenced by the shape of the ship hull, the ray angles where the largest waves are found are mostly a kinematic feature that is only weakly influenced by the hull shape and the related wave amplitude.

Effects of fibre–fibre interaction on stress uptake in discontinuous fibre reinforced composites

The response of discontinuous fibre composites to mechanical loading is regulated to a large extent by the cooperative action of the fibres but the underlying effects of fibre–fibre interaction remain unclear. Here, finite element analysis of a simple 3D representative volume element of an aligned discontinuous fibre composite reveals that the interaction of fibres—described by the fibre–fibre lateral separation distance and axial overlap length—influences the fibre stress uptake during elastic stress transfer. In particular, fibre–fibre lateral separation influences the magnitude of the stress; interestingly axial overlap produces a stepwise stress discontinuity in the fibre.

Numerical model for the calculation of the electrostatic force in non-parallel electrodes for MEMS applications

Abstract In this paper, we investigate the electrical behavior of an electrostatic actuator made of a non-parallel plate's electrodes configuration. The resultant actuation force is caused by the asymmetry of the subsequent electric fringing-fields. This is designed due to the out-of-plane asymmetry of a non-stationary electrode and its two sides actuating stationary electrodes. The electrostatic force is numerically calculated through the results of a two-dimensional numerical solution of the electrostatic problem using Finite-Element Method (FEM). The main objective in this work is to examine the influence of the design parameters on the actuating resultant electrostatic force in this particular arrangement. Four key design parameters were examined: the width and thickness of the electrodes (movable and stationary) as well as the lateral and vertical separation distances between the movable and grounded electrodes. We found out, through several simulations, that both lateral and vertical offsets as well as the electrodes thickness are significant factors in the optimization of the performance of the actuator in such configuration, while the performance seemed to be independent of the electrodes widths. The resultant actuating force level increased with increasing the electrode thickness and with decreasing the electrodes lateral separation distance.