Body Force Research Articles

Recovery and relaxation of the body after physical activity in sports

The article discusses varieties and variants of relaxation techniques that must be used after intense loads. The concept of "relaxation", the understanding of its role in physical education to support health, harmonious development of student youth, mental, mental and physical health has been extensively researched. Also presented are modern diagnostic systems and hardware for the recovery of athletes' bodies, which increase sports performance and maintain physical and mental health. The main direction of physical education is the formation of a healthy, mentally prepared, socially active, morally stable, physically improved and prepared person for the future profession. The human body is a complex system that monitors and regulates its own condition. At rest and during light loads, all processes take place at a normal pace. But the load that affects the body forces it to use reserve energy reserves, which ensures the normal functioning of the body during heavy exercises. After intense training, it is very important to give the body the opportunity to rest before the next exercise. Therefore, the use of various restorative means and modern methods of relaxation after training and competitive loads is considered as an integral part of physical activities. Recovery from exercise is important for improving athletic performance and preventing injury. Physical activity plays an important role in our lives. They help us strengthen muscles, increase endurance, and improve overall fitness. However, after intense training, our bodies need to recover. Insufficient rest can lead to fatigue, injury, and decreased training performance.

Intelligent neural computing to investigate the heat and mass transmission in nanofluidic system between two rotating permeable disks: Supervised learning mechanism

The prime objective of the present study is to investigate the effectiveness and accuracy of a single-trained artificial neural network. The Levenberg-Marquardt Backpropagated networks are tested for heat and mass transmission in magnetized hybrid nanofluid flow between the rotating permeable system. The reference data to generate different cases for distinct scenarios has been obtained using the Adams method in Mathematica using the ND-Solver function. Additionally, the system of highly nonlinear PDE's is achieved and transformed into ODE's. The effect of body forces such as thermophoresis particle diffusion and Brownian motion are incorporated in the hybrid nanofluid system. Configuration under observation is permeable and under constant impact of the magnetic field. Rosseland thermal radiation approximation relation is utilized to investigate the linear impact of radiation on velocity and temperature profile. The accuracy and effectiveness of the proposed ANNLMB are depicted with performance demonstrations. Mean square error, histogram error, and regression plots are generated for all the scenarios to discuss the varying impact of different key study parameters on the performance of the proposed ANNLMB. Furthermore, the generated reference data is distributed in the following manner 82 %, 9 %, and 9 % for training, testing, and validation, respectively.

Is a direct numerical simulation (DNS) of Navier-Stokes equations with small enough grid spacing and time-step definitely reliable/correct?

Turbulence is strongly associated with the vast majority of fluid flows in nature and industry. Traditionally, results given by the direct numerical simulation (DNS) of Navier-Stokes (NS) equations that relate to a famous millennium problem are widely regarded as ‘reliable’ benchmark solutions of turbulence, as long as grid spacing is fine enough (i.e. less than the minimum Kolmogorov scale) and time-step is small enough, say, satisfying the Courant-Friedrichs-Lewy condition (Courant number < 1). Is this really true? In this paper a two-dimensional sustained turbulent Kolmogorov flow driven by an external body force governed by the NS equations under an initial condition with a spatial symmetry is investigated numerically by the two numerical methods with detailed comparisons: one is the traditional DNS, the other is the ‘clean numerical simulation’ (CNS). In theory, the exact solution must have a kind of spatial symmetry since its initial condition is spatially symmetric. However, it is found that numerical noises of the DNS are quickly enlarged to the same level as the ‘true’ physical solution, which finally destroy the spatial symmetry of the flow field. In other words, the DNS results of the turbulent Kolmogorov flow governed by the NS equations are badly polluted mostly. On the contrary, the numerical noise of the CNS is much smaller than the ‘true’ physical solution of turbulence in a long enough interval of time so that the CNS result is very close to the ‘true’ physical solution and thus can remain symmetric, which can be used as a benchmark solution for comparison. Besides, it is found that numerical noise as a kind of artificial tiny disturbances can lead to huge deviations at large scale on the two-dimensional Kolmogorov turbulence governed by the NS equations, not only quantitatively (even in statistics) but also qualitatively (such as spatial symmetry of flow). This highly suggests that fine enough spatial grid spacing with small enough time-step alone could not guarantee the validity of the DNS of the NS equations: it is only a necessary condition but not sufficient. All of these findings might challenge some of our general beliefs in turbulence: for example, it might be wrong in physics to neglect the influences of small disturbances to NS equations. Our results suggest that, from physical point of view, it should be better to use the Landau-Lifshitz-Navier-Stokes (LLNS) equations, which consider the influence of unavoidable thermal fluctuations, instead of the NS equations, to model turbulent flows.

An Analytic Element Model for Seepage Forces in Fractured Media

There are many situations where groundwater flow has high flow rates, causing large seepage forces. Examples are flows around highly conductive fractures and tunnels. We present a new analytic element for a tunnel in an elastic medium. We combined the analytic element method for groundwater flow with that for linear elasticity, and include the seepage force as a body force in the linearly elastic model. We represent tunnels and fractures as analytic elements. The solution for the case considered is limited to steady state flow and fluid-to-solid coupling. We present examples of the computed seepage forces around a tunnel and a fracture as well as a comparison with another numerical model.

Western US intraplate deformation controlled by the complex lithospheric structure

The western United States is one of Earth’s most tectonically active regions, characterized by extensive crustal deformation through intraplate earthquakes and geodetic motion. Such intracontinental deformation is usually ascribed to plate boundary forces, lithospheric body forces, and/or viscous drag from mantle flow. However, their relative importance in driving crustal deformation remains controversial due to inconsistent assumptions on crustal and mantle structures in prior estimations. Here, we utilize a fully dynamic three-dimensional modeling framework with data assimilation to simultaneously compute lithospheric and convective mantle dynamics within the western United States. This approach allows for quantitative estimations of crustal deformation while accounting for the realistic three-dimensional lithospheric structure. Our results show the critical role of the complex lithospheric structure in governing intraplate deformation. Particularly, the interaction between the asthenospheric flow and lithospheric thickness step along the eastern boundary of the Basin and Range represents a key driving mechanism for localized crustal deformation and seismicity.

Experimental Study on the Evolutionary Law of Transient Saturation Zones in a Red Mud Dam under Rainfall Conditions

Utilizing a laboratory model test, this study seeks to evaluate the distribution patterns of volumetric moisture content, soil pressure, and pore water pressure within the body of a red mud dam, given varying initial conditions of slope types and ratios, during continuous heavy rainfall. The objective is to investigate the failure mechanisms of a red mud dam under distinct operational conditions during rainfall, thereby offering insights for landslide prevention and ensuring dam construction quality. The results suggest that a stepped red mud dam acts as a buffer platform, altering the seepage direction within the dam and minimizing the water seepage path. When the slope ratio is 1:1, the transient saturated zone is located on the slope face of the dam’s body, near the top of the slope, with the saturation time at the first monitoring point occurring 300 s earlier than in a dam with a slope ratio of 1:2. Rainfall affects the distribution of internal forces in the red mud dam body. After rainfall, in the transient saturated zone of the stepped dam body, vertical soil pressure decreases 25% and horizontal soil pressure decreases 6.5%; in the transient saturated zone of the dam with a slope ratio of 1:1, vertical soil pressure decreases 14.8% and horizontal earth pressure decreases 29%; in the transient saturated zone of a dam with a slope ratio of 1:3, the change in soil pressure is small.

Identifying the body force from partial observations of a two-dimensional incompressible velocity field

Identifying the body force from partial observations of a two-dimensional incompressible velocity field

Optimizing electrode arrangement in plasma actuators: a study on induced velocity and efficiency

This study investigates the performance of two types of multi-encapsulated electrode (MEE) plasma actuators, compared to typical dielectric barrier discharge (DBD) plasma actuators, in quiescent air. The objective is to determine whether the multiple encapsulated structure can enhance the performance of the plasma actuator. In the present paper, flow characteristics are investigated by using particle image velocimetry (PIV) and Schlieren visualisation. In addition, the distribution of body force over the gas volume based on the Navier–Stokes equations is calculated from velocity measurements. The obtained results demonstrate that the starting vortex behavior is influenced by electrode arrangement. Specifically, it can be observed that when the first encapsulated electrode is positioned closer to the exposed electrode, then a significantly higher induced velocity can be obtained compared to the baseline condition. In fact, the induced velocity can be increased by up to 1.5 times under this optimize configuration. These results highlight the importance of electrode arrangement in the plasma actuator design. Based on body force estimation, MEE plasma actuators exhibit a significantly higher momentum transfer, particularly in the wall normal direction. The investigation on the mechanical efficiency also reveals that the optimized configuration proposed in the present study can significantly enhance the efficiency. In fact, a four-fold increase in maximum efficiency compared to the typical configuration is observed. These results suggest that the proposed configuration could be considered a promising solution for improving the mechanical efficiency of plasma actuators.

Self-starting and performance improvement of a Darrieus type wind turbine using the plasma actuator

Although the popularity of Darrieus-type vertical axis wind turbines is growing for small-scale electricity generation, these turbines have severe challenges in self-starting. This paper proposes a flow control method, namely, the plasma actuator, to solve the self-starting problem besides enhancing the turbine performance. The Darrieus turbine is numerically investigated using a pressure-based finite volume method to solve the unsteady Reynolds-averaged Navier–Stokes and the γ–Reθt transitional model equations. Simulation of the blade rotation is performed using the sliding mesh technique accompanied by the turbine equation of motion to enable the blade rotational degree of freedom. Furthermore, the body forces associated with the plasma actuator are determined by calibrating the Shyy plasma model parameters. The plasma actuator is assessed at both the constant and free rotational speeds. The constant rotational speed results in plasma off condition show negative torque generation for tip speed ratios lower than 1.5, known as the origin of turbine self-starting challenges. The plasma actuator improves the negative torque by 128% in the tip speed ratio of 0.5 and turns it positive. Also, at larger tip speed ratios, it reduces the negative torque generation and enhances the turbine power production by up to 260%. Furthermore, the plasma actuator in free rotational speed improves the tip speed ratio increment by up to 8%, reducing the total time of turbine self-starting.

Data-driven surrogate modelling of multistage Taylor cone–jet dynamics

The Taylor cone jet is an electrohydrodynamic flow typically induced by applying an external electric field to a liquid within a capillary, commonly utilized in colloidal thrusters. This flow generation involves a complex multiphase and multiphysics process, with stability contingent upon specific operational parameters. The operational window is intrinsically linked to flow rate and applied electric voltage magnitude. High voltages can induce atomization instabilities, resulting in the production of an electrospray. Our study presents initially a numerical investigation into the atomization process of a Taylor cone jet using computational fluid dynamics. Implemented within OpenFOAM, our numerical model utilizes a volume-of-fluid approach coupled with Maxwell's equations to incorporate electric body forces into the incompressible Navier–Stokes equations. We employ the leaky-dielectric model, subjecting the interface between phases to hydrodynamic surface tension and electric stress (Maxwell stress). With this model, we studied the droplet breakup of a heptane liquid jet, for a range of operation of 1.53–7.0 nL s−1 and 2.4–4.5 kV of extraction. First, the developed high-fidelity numerical solution is studied for the jet breakup and acceleration of the droplets. Second, we integrate a machine learning model capable of extending the parametric windows of operation. Additionally, we explore the influence of extractor and acceleration plates on colloidal propulsion systems. This work offers a numerical exploration of the Taylor cone–jet transition and droplet acceleration using novel, numerically accurate approaches. Subsequently, we integrate machine learning models, specifically an artificial neural network and a one-dimensional convolutional neural network, to predict the jet's performance under conditions not previously evaluated by computationally heavy numerical models. Notably, we demonstrate that the convolutional neural network outperforms the artificial neural network for this type of application data, achieving a 2% droplet size prediction accuracy.

Design and Development Chairless Chair

Abstract: It is very difficult to stand and work for overall shift in the company by a worker. This will reduce the efficiency of the worker. The solution to this problem is to have a portable device which has an ergonomic design, low cost exoskeletons. In this work a mechanical ergonomics device that is designed around the shape and function of the human body, with segments and joints corresponding to those of the person it is externally coupled with. It functions as a chair whenever it is needed and is coined as Chair less Chair. Worker in industrial can wear it on legs like an exoskeleton. It locks into place and you can sit down on it. The device never touches the ground, which makes it easier to wear: a belt secures it to the hips and it has straps that wrap around the thighs. These are specially designed and part of the mechanism, but an alternate version works with any footwear and touches the ground only when in a stationary position. The user just moves into the desired pose. It will fit closely to lower part of the body as an external body part on which maximum body forces act upon. It is a cost effective product and any error in design may fail the structure which creates loss. So, these forces should be carefully analyzed during the design of structure. The best way to predict these forces during pre-manufacturing stage is to make an analysis on the structure with the help of software. This helps in estimating the stresses induced on the structure which is one of the most important criteria for evaluation of the model.

Study on Stress Distribution Law of Anchorage Body

In order to reveal the stress distribution law of the anchorage body during the drawing process, through the analysis and research on the anchoring mechanism of the anchor rod, it is found that the bonding mechanism of the interface between the anchor rod and the anchoring material is mainly determined by three factors : bonding force, mechanical interlocking and friction force. The bonding mechanism of the anchorage material-surrounding rock interface is mainly determined by two factors : bonding force and friction force. Then, the mechanical model of anchorage body is established, and the distribution equations of axial force and interfacial shear stress of anchorage body are obtained by theoretical analysis. The axial force and shear stress curves are obtained by substituting the relevant parameters. It is found that the axial force and interfacial shear stress curves are exponentially decreasing. The axial force of the bolt is approximately equal to the load applied on the bolt, and at the end of the anchorage, the axial force approaches zero.

Rigorous benchmarking of an iterative IBM solver by comparison to body-fitted mesh results

This study addresses the validation challenges of Immersed Boundary Method (IBM) solvers by proposing a consistent benchmarking approach. A temporally second-order Arbitrary Lagrangian–Eulerian (ALE) solver implemented in OpenFOAM is verified against lid-driven cavity flow and flow past static and oscillating cylinders. It then serves as the underlying fluid flow solver for a fully implicit diffusive direct forcing IBM solver that achieves temporal second-order accuracy, verified by the static and oscillating cylinder cases. Leveraging the shared numerical framework, the IBM solver is rigorously validated against ALE using identical settings, parameters, and nearly identical grids across twenty test cases, including stationary cylinder flow (Re = 40, 100, 185), oscillating cylinder in quiescent flow (Re = 100, KC = 5), and transversely oscillating cylinders with varying amplitudes and frequencies (16 cases in total). The IBM solver demonstrates robustness (CFL up to 8) and accuracy over a wide Reynolds number range, with relative drag coefficient errors below 7% for all considered cases. Incorporating body force correction, which reduces slip errors at negligible added computational cost, drastically improves accuracy. Proper Rhie–Chow momentum interpolation, including body forces, is critical in the adopted collocated finite volume method. For unsteady problems, the computational cost is greatly reduced without compromising accuracy by using CFL≈1.5−2 with only two outer iterations. The proposed benchmarking framework can be easily used for validation of other IBM approaches and thus potentially help to advance the state of IBM.

Current and density observations on a flow through a contraction and over a bottom elevation at the southern edge of the Cycladic Plateau in the Aegean Sea – East Mediterranean

A CTD/ADCP/surface-drifter survey in fall 2004 reveals the behaviour of a mesoscale unidirectional flow coming from the Cretan sea in the south with depths ∼1000 m and entering a channel-like area of the Cycladic shelf in the north, that forms a contraction which leads to a bottom elevation (sill depth ∼100 m), and finally returning into the Cretan Sea in the lee-side of the sill. The flow decelerates/accelerates upstream/downstream of the sill. The along-stream density contours near the sill bottom are raised prior to reaching the sill, while they deepen in the lee side of it indicating supercriticality. The long-wavelength internal wave speeds with realistic stratification and no-rotation are higher than the section averaged flow speeds and indicate subcriticality. A key element in this apparent paradox is the large height of the sill that potentially increases the body (drag) force exerted on the flow by the sill while flow blocking is also observed upstream of the sill.

A non-boundary-fitted-grid method, based on compact integrated-RBF approximations, for solving differential problems in multiply-connected domains

This paper presents a new non-boundary-fitted-grid numerical technique for solving partial differential equations (PDEs) in multi-hole domains. A multiply-connected domain is converted into a simply-connected domain of rectangular or non-rectangular shape that is discretised using a Cartesian grid. Compact radial basis function (RBF) stencils, which are constructed through integration rather than the conventional differentiation, are used to discretise the field variables. The imposition of inner boundary conditions is conducted by means of body forces that are derived from satisfying the governing equations and prescribed boundary conditions in small subregions. Salient features of the proposed method include: (i) simple pre-processing (Cartesian grid), (ii) high rates of convergence of the solution accuracy with respect to grid refinement achieved with compact integrated-RBF stencils, where both nodal function and derivative values are included in the approximations, (iii) the system matrix kept unchanged for the case of moving holes, and (iv) no interpolation between Lagrange and Euler meshes required. Several linear and nonlinear problems, including rotating-cylinder flows and buoyancy-driven flows in eccentric and concentric annuli, are simulated to verify the proposed technique.

An Improved Body Force Model to Simulate Blade Loading Variation Under Various Operating Conditions in Transonic Axial Flow Compressor

Abstract In order to analyze the unsteady aerodynamic response of compressors with limited computational resources, the development of the body force (BF) model has been pursued for decades. This model can simulate the effects of the compressor blade on the flow by applying a three-dimensional (3D) force field. Indeed, the accuracy of the BF model simulation highly depends on the construction strategy of BF field. However, for a transonic compressor, the influence of shock waves on the spatial distribution of blade loading is significant, which makes the construction of an appropriate BF field challenging. To solve this issue, an accurate BF model is proposed to describe the effects of the blade on the flow with high spatial fidelity in transonic compressors. For verification, a typical transonic fan rotor, NASA-Rotor 67, is selected. The numerical results calculated by the new BF model are compared with those obtained by the Reynolds-averaged Navier–Stokes (RANS) solver. According to the results, the new model can accurately capture the distribution of blade loading in the transonic blade channel at various operating conditions, eventually leading to a good prediction of compressor performance and the radial distribution of flow parameters downstream of the rotor. Moreover, this study discusses the causes of modeling errors and presents the application of the model in inlet distortion simulation at the end.

Efficient Generation of Plasma‐Activated Aerosols with High Concentrations of Reactive Species via Silicon Dioxide Coated Surface Acoustic Wave Devices

AbstractAn effective method to deliver plasma‐activated water onto contaminated surfaces is with a surface acoustic wave (SAW) nebulizer that can efficiently produce plasma‐activated aerosols. While higher reactive species concentrations in the plasma‐activated aerosols promote more efficient bacterial inactivation and hence reduce the amount of aerosols needed to completely eradicate the bacteria colonies, higher concentrations of reactive species themselves are found to lead to lower nebulization rates due to the increased electrical conductivity of the solution. To circumvent this problem, it is shown that coating the SAW substrate with a thin insulating layer of silicon dioxide (SiO2) can significantly mitigate the nebulization rate reduction. Specifically, when the electrical conductivity increases from 0.25 to 4.0 mS cm−1, the 62% drop in the nebulization rate is observed with the uncoated SAW devices is substantially reduced to 19% simply with the SiO2 coating. This can be attributed to the synergistic effects of increased wettability and the suppression of the electrical body force acting on the liquid film. The concomitant increase in the bacterial colony reduction from 17% to 76% demonstrates this solution to be a facile yet effective way of enhancing the efficiency for spray‐based bacterial inactivation on contaminated surfaces.

Experimental investigation on punch shear strength of poly lactic acid specimens for biomedical applications.

The designed biomedical implants require excellent shear strength primarily for mechanical stability against forces in human body. However, metallic implants undergo stress shielding with release of toxic ions in the body. Thus, Fused Deposition Modeling (FDM) has made significant progress in the biomedical field through the production of customized implants. The mechanical behavior is highly dependent on printing parameters, however, the effect of these parameters on punch shear strength of ASTM D732-02 standard specimens has not been explored. Thus, in the current study, the effect of infill density (IFD), printing speed (PTS), wall thickness (WLT), and layer thickness (LYT) has been investigated on the punch shear strength using Response Surface Methodology. The Analysis of Variance (ANOVA) has been performed for predicting statistical model with 95% confidence interval. During the statistical analysis, the terms with p-value lower than 0.05 were considered significant and the influence of process parameters has been examined using microscopic images. The surface plots have been used for discussing the effect of interactions between printing parameters. The statistical results revealed IFD as the most significant contributing factor, followed by PTS, LYT, and WLT. The study concluded by optimization of printing parameters for obtaining the highest punch shear strength.

Numerical heat and mass transfer in magnetized Williamson liquid motion over a sensor wall engulfed in a micro-cantilever system: An application to thin-film fluidic cells

Central focus of this numerical analysis is to investigate the influence of magnetic body force and thermal radiation on the time-dependent electrically conducting two-dimensional viscous incompressible boundary layer flow of non-Newtonian Williamson fluid over a microcantilever sensor surface suspended in a squeezed regime numerically. A novel heat source/sink and Soret effects are included in the respective governing equations. The constructed time-dependent nonlinear coupled partial differential equations are solved by using a bobust RK-4 technique. Increasing magnetic number increases the velocity distribution and decreases the temperature and concentration profiles in the flow regime.Enhancing Soret number increases the mass diffusion profile. Increasing magnetic number suppress the skin-friction coefficient. Heat transport rate booted with rising radiation number and Sherwood number decreased with enlarged Schmidt number in the channel regime. Finally, the numerical accuracy of the present similarity solutions and used numerical method is validated with existing results and observed a remarkable agreement.

A modified local thermal non-equilibrium model of transient phase-change transpiration cooling for hypersonic thermal protection

Aiming to efficiently simulate the transient process of transpiration cooling with phase change and reveal the convection mechanism between fluid and porous media particles in a continuum scale, a new two-phase mixture model is developed by incorporating the local thermal non-equilibrium effect. Considering the low-pressure and high overload working conditions of hypersonic flying, the heat and mass transfer induced by capillary and inertial body forces are analyzed for sub-cooled, saturated and super-heated states of water coolant under varying saturation pressures. After the validation of the model, transient simulations for different external factors, including spatially-varied heat flux, coolant mass flux, time-dependent external pressure and aircraft acceleration are conducted. The results show that the vapor blockage patterns at the outlet are highly dependent on the injection mass flux value and the external pressure, and the reduced saturation temperature at low external pressure leads to early boiling off and vapor blockage. The motion of flying has a large influence on the cooling effect, as the inertial force could change the flow pattern of the fluid inside significantly. The comparison of the results from 2-D and 3-D simulations suggests that 3-D simulation shall be conducted for practical application of transpiration cooling, as the thermal protection efficiency may be overestimated by the 2-D results due to the assumption of an infinite width length of the porous plate.