Dissipative Forces Research Articles

Lorentz force influenced entropy generation in couple stress squeezed hybrid-nanofluid flow: Application to cardiovascular hemodynamics

The main aim of this numerical analysis is to demonstrate the effect of Lorentz force and viscous dissipation on the couple stress-squeezed hybrid-nanofluid flow between two parallel plates under the influence of external squeezing. A novel entropy generation effect is also included to describe the temperature distribution in the couple stress hybrid nanofluid regime. However, the couple stress hybrid nanofluid finds its abundant applications in the various fields of medicine and bio-engineering, particularly, in the removal of obstacles in the arteries, cancer treatment, etc. Inspired by these applications of couple stress hybrid nanofluids, the present problem is devised based on the squeezed parallel plate geometry. The unsteady nonlinear, coupled, two-dimensional, partial differential equations are constructed to disclose the flow and heat transport features. A robust Matlab-based Runge–Kutta fourth-order scheme with shooting technique is used to produce the similarity solutions of the governing equations through the deployment of suitable scaling transformations. Accordingly, it is noted that, enhancing Hartmann and Brinkman numbers increase the entropy generation. Increasing couple stress fluid parameter increases the thermal distribution. Velocity profile shows dual behavior for the raising couple stress fluid parameter. Bejan number increases with increasing Brinkman number. Entropy generation increases with enhancing nanofluid volume fraction. Conclusively, the uniqueness and novelty of the present investigation is the addition of magnetic Ohmic heating and viscous dissipation effects which generalizes the former studies and gives a more redefined numerical simulation of flow and heat transport features of couple stress hybrid nanofluid in the squeezing regime.

Arbitrary slip length for fluid-solid interface of arbitrary geometry in smoothed particle dynamics

We model a slip boundary condition at fluid-solid interface of an arbitrary geometry in smoothed particle hydrodynamics and smoothed dissipative particle dynamics simulations. Under an assumption of linear profile of the tangential velocity at quasi-steady state near the interface, an arbitrary slip length b can be specified and correspondingly, an artificial velocity for every boundary particle can be calculated. Therefore, b as an input parameter affects the calculation of dissipative and random forces near the interface. For b→0, the no-slip is recovered while for b→∞, the free-slip is achieved. Technically, we devise two different approaches to calculate the artificial velocity of any boundary particle. The first has a succinct principle and is competent for simple geometries, while the second is subtle and affordable for complex geometries. Slip lengths in simulations for both steady and transient flows coincide with the expected ones. As demonstration, we apply the two approaches extensively to simulate curvy channel flows, dynamics of an ellipsoid in pipe flow and flows within complex microvessels, where desired slip lengths at fluid-solid interfaces are prescribed. The proposed methodology may apply equally well to other particle methods such as dissipative particle dynamics and moving particle semi-implicit methods.

Combined SCD-SPSW system subjected to ground excitation

PurposeIn this study, the application of a novel combined steel curved damper (SCD) and steel plate shear wall (SPSW) system in the 5-, 10- and 15-storey steel moment-resisting frames (SMR) subjected to earthquake excitation has been investigated. The proposed system is called here as the SMR-WD (steel moment resisting–wall damper).Design/methodology/approachAt the beginning of this research, an SMR-W and an SMR-D are separately modeled in ABAQUS software and verified against the available experimental data. After that, three different heights SMR-WD systems (5-, 10- and 15-storey) are designed and simulated. Then, their performances are examined and compared to the corresponding SMR-W under the effects of six actual earthquake records.FindingsThe obtained results show that the proposed system increases the mean values of the base shear for 5-, 10- and 15-storey SMR-WD equal to 27, 20.15 and 16.51%, respectively compared to the corresponding SMR-W. Moreover, this system reduces the drift of the floors so that the reduction in the average values of maximum drift for 5-, 10- and 15-storey SMR-WD is equal to 10, 7 and 29%, respectively with respect to the corresponding SMR-W. The results also reveal that the considered system dissipates more energy than SMR-W so that the increase in the mean values of the energy absorption for 5-, 10- and 15-storey SMR-WD is 30.8, 25.6 and 41.3%, respectively when compared to the SMR-W. Furthermore, it is observed that SMR-WD has a positive effect on the seismic performance of the link beams and panel zones of the frames. By increasing the height of the structure in the SMR-WD, the energy dissipation and base shear force increases and the drift of floors decreases. Hereupon, the proposed SMR-WD system is more useful for tall buildings than SMR-W frames.Originality/valueFor the first time, the application of a novel combined steel curved damper (SCD) and steel plate shear wall (SPSW) system in the 5-, 10- and 15-storey steel moment-resisting frames (SMR) subjected to earthquake excitation has been investigated.

Numerical Analysis of Viscous Polymer Resin Mixing Processes in High-Speed Blade-Free Planetary Blender Using Smoothed Particle Hydrodynamics

High-speed planetary mixers can rapidly and efficiently combine rheological liquids, such as polymer resins and paste materials, because of the large centrifugal forces generated by the planetary motion of the mixing vessel. Only a few attempts have been made to computationally model and analyze the intricate mixing patterns of highly viscous substances. This paper presents meshless flow simulations of the planetary mixing of polymeric fluids. This research utilized the smoothed particle hydrodynamics (SPH) approach for numerical calculations. This method has advantages over the finite-volume method, which is a grid-based computational technique, when it comes to modeling interfacial and free surface flow problems. Newtonian rheology and interfacial surface force models were used to calculate the dissipative forces in the partial differential momentum equation of fluid motion. Simulations of the flow of an uncured polyurethane resin were carried out while it was mixed in a planetary mixer, under various operating conditions. Simulations using SPH were able to accurately reproduce the intricate flow and blending pattern, providing insight into mixing mechanics and mixing index evolution characteristics according to operating conditions for the planetary mixing of polymeric fluids. The simulation results showed that the spiral band, which promotes the mixing performance, is densely and distinctively formed under high-speed operation conditions.

ОБОСНОВАНИЕ РАЦИОНАЛЬНОЙ КОНСТРУКЦИИ СКОЛЬЗУНОВ ТЕЛЕЖКИ ПАССАЖИРСКОГО ВАГОНА

At the first stage, a detailed dynamic solid-state model of a passenger car is developed which has a bolsterless truck. The dynamic model is a system of absolutely rigid bodies interconnected by elastically dissipative linear and nonlinear force elements, hinges and contact forces. The adequacy of the car dynamic model and the reliability of the results obtained are evaluated the results of running tests. Based on the developed solid-state dynamic model, a comprehensive study of the effect of the friction factor on the guide block support surfaces on the safety and dynamic performance of a passenger car under various modes of movement along the track, taking into account irregularities is carried out. As a result of modeling, a range of rational values of friction moments on the support guide blocks is obtained. The composition of the composite material for the support surfaces of the truck guide blocks is selected using neurocomputer modeling methods, the manufacture of the proposed composite material is tested, experimental studies of the characteristics of composite elements confirming their properties and safety were carried out.

Applying the Lagrange multiplier technique to reconstruct a force-free magnetic field

Context. The magnetic field in the solar corona can be reconstructed by extrapolating the data obtained by measuring the magnetic field in the photosphere. It is widely thought that the dynamics of the solar corona is governed by the magnetic field. The magnetic field in the corona can therefore be reconstructed using the physics of force-free fields. Several models have been developed so far to reconstruct the magnetic field, but shortcomings in this regard remain. Therefore, alternative models in this respect can still be proposed. Here we apply the Lagrange multiplier technique to render an optimization model. Aims. The main aim of the present paper is to propose a method of constrained optimization using the vector Lagrange multiplier and compare the results with those of preexisting models. Methods. Our main focus is on the conceptual modification of the optimization models. Since these models are computationally efficient and easy to implement, any possible progressive step would be welcome. The Lagrange multiplier technique is a powerful mathematical tool that has been successfully applied to many areas in physics. It may serve this purpose. In the absence of nonmagnetic forces such as pressure, gravity, and dissipative forces, the coronal medium is dominated by magnetic force. Thus, the function that is considered to be minimized may include a divergence term subject to the constraint force-free term, which yields a solenoidal and force-free magnetic field by an iterative process. Results. The numerical analysis of the proposed model was conducted through an artificial magnetogram and an observational vector magnetogram obtained by SDO/HMI images. The results obtained confirm that (i) the Lagrangian to be minimized in the present model converges slightly faster toward zero, at least for initial iteration steps, (ii) the energy variation during the optimization is compatible with the variations in previous studies, (iii) the numerical results seem to be compatible with a semi-analytical solution as the test case, and (iv) the model is applied to a real magnetogram, and relevant quantities such as magnetic energy content, the current-weighted angle between the current density vector and magnetic field, and the fractional flux errors are computed. Conclusions. The methods and techniques that convert a constrained problem into an unconstrained one are the penalty method, the barrier method, the augmented Lagrangian method, and the Lagrange multiplier technique, for instance. We have employed the Lagrange multiplier technique, by which any constrained condition could be added to the Lagrangian by an appropriate Lagrange multiplier. In our case, the constraint is the force-freeness of the magnetic field and is therefore a special case. The method has the following advantages: (i) The convergence rate is slightly higher for the initial iteration steps, which may help us for time-series events, while several magnetograms must be considered and limited steps of iteration may be needed. (ii) The Lagrangian is introduced based on the Lagrange multiplier technique, which facilitates first fixing a physical compromise such as a divergence-free condition, and subsequently adding any given constraint term. (iii) The quantities obtained by the constrained optimization with the vector Lagrange multiplier model, that is, the relative magnetic energy, the ratio of the magnetic energy to its initial value, the angle between the electric current and the magnetic field, fractional flux errors, the normalized vector error, the vector correlation, and the Cauchy-Schwarz indicator, are comparable with those of the comparison models considered in this article.

Coupled Oscillators in an Agroecosystem: Integrating Direct and Indirect Effects.

AbstractAgricultural pests are increasingly appreciated as subjects of ecology. One particular case, a pest in coffee production, is analyzed here using the conceptual framework of complex systems, increasingly acknowledged as having an obvious home in the field of ecology, notorious for its complex structures. The particular case analyzed here arguably falls under the control of the complexity of the ecological system rather than of a simple magic bullet of population regulation. The system, which has been under study in southern Mexico for the past quarter century, is analyzed through the lens of neutral oscillations of the classical nondissipative Lotka-Volterra system. Based on three consumer/resource pairs (populations of [1] an ant, [2] a scale insect, [3] a beetle predator of the scale insect, [4] a fungal pathogen of the scale insect, and [5] a fly parasitoid of the ant), this five-dimensional system is well known qualitatively. Coupling all agents through both direct effects and trait-mediated indirect effects, the behavior of the neutral oscillation form of the system reveals a complex set of behaviors, including harmonized invariant sets, chaos, and/or quasiperiodicity. Such behaviors are well-known subjects in the science of complex systems and, it is argued, are ultimately sufficient to effect a degree of regulation on the pest, independent of explicit density-dependent feedback. Control of the system is thus seen as arguably actuated through its complexity, independent of any classic dissipative force.

Mathematical analysis for energy transfer of micropolar magnetic viscous nanofluid flow on permeable inclined surface and Dufour impact

This study examined the flow of nanoliquid over an extendible surface in a micro-rotational manner. Nanotechnology recently prioritized nanoparticle dispersion in liquids. Nanoparticles increase the thermal conductivity of conventional liquids, which helps generate and transmit energy. The movement of energy has been chosen as a primary area of study in this examination via permeable oblique surface. Dufour impacts and thermal radiation have both been used in this investigation. Moreover, the viscous dissipative and magnetism force influences are considered on the porous medium. This work makes use of the popular bvp4c computational technique. A proper similarity conversion is managed to convert the flow expressions into nonlinearly differential equations. In the appearance of charts and tables, the physical values are depicted along with various consequences of material limitations. Based on the findings, we were able to determine that the Dufour and Eckert effects are responsible for the increase in the temperature profile contrary to the permeability of the inclined surface also Because of the angle of the surface, the velocity curve is found to be lower. This fundamental finding will help engineers and scientists manage the fluid flow and enhance sophisticated systems that employ it.

Crural and Plantar Fasciae Changes in Chronic Charcot Diabetic Foot: A Cross-Sectional Ultrasound Imaging Study-An Evidence of Fascial Continuity.

Crural fascia (CF) and plantar fascia (PF) are biomechanically crucial in the gait and in the proprioception, particularly in the propulsion phase of the foot during the gait cycle and in the dissipation of forces during weight-bearing activities. Recent studies have revealed an association between increases in PF thickness and diabetes. The purpose of this study was to measure and compare by ultrasound (US) imaging the thickness of the CF and PF at different regions/levels in chronic Charcot diabetic foot patients (group 1) and in healthy volunteers (group 2). A cross-sectional study was performed using US imaging to measure the CF with Pirri et al.'s protocol and PF with a new protocol in a sample of 31 subjects (15 patients and 16 healthy participants). The findings for CF and PF revealed statistically significant differences in the poster region of CF (Post 1: group 1 vs. group 2: p = 0.03; Post 2: group 1 vs. group 2: p = 0.03) and in PF at two different levels (PF level 1: group 1 vs. group 2: p < 0.0001; PF level 2: group 1 vs. group 2: p < 0.0001). These findings suggest that chronic Charcot diabetic foot patients have CF and PF thicker compared to healthy volunteers. The US examination suggests that fascial thicknesses behavior in these patients points out altered fascial remodeling due to diabetes pathology and biomechanical changes.

Whether contact time can evaluate the anti-icing properties of superhydrophobic surface - A research based on the MDPDE method

Impact freezing of droplets on a cold surface has attracted the attention of scholars. This process is vital for practical problems such as the anti-icing of aircraft wings and cables. Researchers have found that superhydrophobic surfaces can reduce the contact time of droplets and delay nucleation. However, whether contact time can evaluate the anti-icing properties of superhydrophobic surface needs further study. Considering the change in droplet temperature, we vary the dissipative force term of the conservative force in the many-body dissipative particle dynamics with the energy conservation (MDPDE) method. Then combined with the experimental results, a nucleation model of the recalescence rate related to the degree of undercooling is achieved. Finally, we obtain a droplet impact freezing model based on the MDPDE method for the first time, and the impact processes of supercooled droplets on the superhydrophobic surface with three different topological microstructures are explored. Effect of Weber number We on the critical adhesion temperature T* of micropillar surface is reversed when the solid fraction φ is different, and φ is the main factor affecting T*of the microcavity surface. When other conditions are the same, T* of the microridge surface is the lowest. And surprisingly, we observed that the contact time of droplets did not fully measure the anti-icing ability of the superhydrophobic surface.

Sliding U-shaped steel damper for multi-directional displacement

A U-shaped steel damper may undergo multi-directional displacements. However, U-shaped energy-dissipation plates with large width-to-thickness ratio may experience unexpected torsional deformation during an out-of-plane displacement and provide an unstable restoring force and energy dissipation. Discussed here is a sliding U-shaped steel damper that uses connecting structures to obtain force-free sliding in out-of-plane directions. Cyclic performances under multi-directional displacements were verified experimentally, and out-of-plane force-free sliding was observed. The energy-dissipation plates only exhibited in-plane plastic deformation and provided a stable restoring force as well as energy dissipation. Equations for the yield and ultimate restoring forces were developed by considering the loading angle, and a finite element model in ABAQUS reproduced physical tests. Connection structures were thus improved for higher stiffness, and lateral sliding that considered the peak vertical force was also proposed. Finally, an analytical hysteretic model for the sliding U-shaped steel damper was abstracted based on the test and simulation results, which shows acceptable agreement with the test results.

The deposition kinetics of barium sulphate scale: model development

The deposition kinetics of barium sulphate scale: model development

Stability analysis of nonstationary mechanical systems with time delay via averaging method

A linear mechanical system with constant matrix of dissipative forces and continuous and bounded matrices of positional forces is studied. It is assumed that there are a large positive multiplier at the vector of dissipative forces and a constant delay in positional forces. The case is considered where the associated delay-free averaged system is asymptotically stable. With the aid of the Lyapunov direct method and the averaging method, conditions are derived under which neither delay nor timevarying perturbations with zero mean values disturb the asymptotic stability. The developed approach is used in the problem of monoaxial stabilization of a rigid body.

Уточнение математической модели межвагонной связи с пружинно-фрикционными поглощающими аппаратами для исследования продольных колебаний грузового поезда

Purpose: To develop an improved model of inter-car coupling equipped with spring-friction absorbing devices of the PMK-110 type. This model should take into account both the features of the power characteristics of absorbing devices of this type and the deformation of the carriage bodies, as well as the energy dissipation of longitudinal forces arising in the train due to the viscous resistance to deformation of the car structure. Methods: Methods of analysis, mathematical and simulation modeling. Results: Based on two existing mathematical models of inter-car couplings with spring-friction absorbing devices, an improved model of inter-car coupling equipped with spring-friction absorbing devices of the PMK-110 type has been developed. It is shown that this model increases the reliability of calculating the values of the longitudinal forces arising in the absorbing devices of the intercar couplings of the train. Practical significance: The proposed model of inter-car coupling can be used in studies of longitudinal vibrations of a train, since it gives more reliable calculation results for all loading modes.

Low-Temperature-Tolerant Strain-Sensing Flexible Composite for Soft Body Armor.

Developing soft body armor with sensing characteristics in various application scenarios is a challenge but important for creating a peaceful world and personal safety, whereas existing materials suffer from indefinite protective effects and stimulus response at subzero temperatures in the long term. Herein, an anti-freezing and flexible puncture-resistance composite with strain-sensing ability is developed by compounding a NaCl-soaked poly(vinyl alcohol) (PVA)/sodium alginate (SA)/glycerol (Gly) hydrogel (PSGN hydrogel) with Kevlar fabric. After freezing-thawing treatment once and NaCl immersion for 10 h, the Kevlar/PSGN-10 composite has excellent puncture-resistance properties and linear, rapid response, wide band, and stable strain-sensing behaviors at 25 and -30 °C. The composite's maximum puncturing force and energy dissipation at -30 °C are 53.92 N and 370 mJ, respectively, increased by 285 and 302% compared with neat Kevlar fabric. The flexibility reduction and the mass addition of the Kevlar/PSGN-10 composite are merely 19 and 40%, respectively, showing superior wearable comfortability and protection efficiency. The composites also reveal remarkable strain-sensing abilities at -30 °C (linear strain sensitivity with GF = 0.27 and R2 = 0.981, a wide working frequency range of 0.16-1.3 Hz, and sensing stability for 1500 cycles). Moreover, the composite could respond to multipart body motion directly, including fingers, elbows, wrists, and knees. Consequently, the Kevlar/PSGN composite developed in this paper is promising for intelligent soft body armor at various temperatures.

A chaotic bio-mechanics model of dairy cow leg

The real knee joint is very complex. When the knee joint performs the leg bending action, the relative motion between the lower surface of the femur and the upper surface of the tibia includes rolling and sliding. Therefore, a simple hinge pair model cannot correctly represents the real knee joint motion. In this work, we build a structure model of cow leg with both sliding and hinge pairs firstly; Then, according to the second kind of Lagrange equation of the structural model with the potential force and dissipative force, the system dynamics model is established. Third, the environmental noise, such as the elasticity of the ground which exerted on the cow’s feet directly, is taken into the nonlinear model, so, a more practical dynamic model of cow leg is constructed. Numerical simulation shows that the model has strong chaotic motion characteristics,and the model with noises is better than one without noises. For the chaotic model, small parameter changes will lead to large changes in the phase orbit diagram, which built a foundation for us to study and identify the pathology of dairy cows based on the dynamic weight time series signals during the process of dairy cows’ progress.

Dual Quaternions Representation of Lagrange's Dynamic Equations

Abstract This paper introduces for the first time, the Lagrange's dynamic equations in dual number quaternion form. Additionally, Rayleigh's dissipation function in dual quaternion form is introduced here allowing for the accounting of dissipative (non-conservative) forces such as motion through a viscous fluid, friction, and spring damping force. As an example, dual quaternions are used here to derive the Lagrange dynamic equations of a robot manipulator.

Experimental characterization and parameter identification of bolted joints under vibratory loading

The paper experimentally investigates the frictional behaviour of bolted joints with varying preload, inclined bolt head interface, and varying contact area between plates subjected to tangential loading. Experimental result shows a reduction macroslip force and energy dissipation with decrease in bolt preload. Similarly, increase in inclination of bolt bearing surface reduces macroslip force and energy dissipation. The reduction in contact area does not affect the tangential stiffness or frictional energy dissipation when contact pressure profile on plate interface is fully developed. For truncated pressure profile, the reduction in contact area reduces both the tangential stiffness and the energy dissipation. The experiments are conducted to determine the energy dissipation during pinning reveals differential pinning for lower displacements. At higher displacements, the crack initiates into the bolt shank which reduces the energy dissipation.

Imaging quantized vortex rings in superfluid helium to evaluate quantum dissipation

The motion of quantized vortices is responsible for many intriguing phenomena in diverse quantum-fluid systems. Having a theoretical model to reliably predict the vortex motion therefore promises a broad significance. But a grand challenge in developing such a model is to evaluate the dissipative force caused by thermal quasiparticles in the quantum fluids scattering off the vortex cores. Various models have been proposed, but it remains unclear which model describes reality due to the lack of comparative experimental data. Here we report a visualization study of quantized vortex rings propagating in superfluid helium. By examining how the vortex rings spontaneously decay, we provide decisive data to identify the model that best reproduces observations. This study helps to eliminate ambiguities about the dissipative force acting on vortices, which could have implications for research in various quantum-fluid systems that also involve similar forces, such as superfluid neutron stars and gravity-mapped holographic superfluids.

Thermal inspection for viscous dissipation slip flow of hybrid nanofluid (TiO2–Al2O3/C2H6O2) using cylinder, platelet and blade shape features

Hybrid nanofluid are the modified class of nanofluids with extra high thermal performances and present different applications in automotive cooling, heat transfer devices, solar collectors, engine applications, fusion processes, machine cutting, chemical processes etc. This thermal research explores the heat transfer assessment due to hybrid nanofluid with of different shape features. The thermal inspections regarding the hybrid nanofluid model are justified with aluminium oxide and titanium nanoparticles. The base liquid properties are disclosed with ethylene glycol material. The novel impact of current model is the presentation of different shape features namely Platelets, blade and cylinder. Different thermal properties of utilized nanoparticles at various flow constraints are reported. The problem of hybrid nanofluid model is modified in view of slip mechanism, magnetic force and viscous dissipation. The heat transfer observations for decomposition of TiO2–Al2O3/C2H6O2 is assessed by using the convective boundary conditions. The shooting methodology is involved for finding the numerical observations of problem. Graphical impact of thermal parameters is observed for TiO2–Al2O3/C2H6O2 hybrid decomposition. The pronounced observations reveal that thermal rate enhanced for blade shaped titanium oxide-ethylene glycol decomposition. The wall shear force reduces for blade shaped titanium oxide nanoparticles.