Inertial Resistance Research Articles

A mechanical model for spherical fragments penetrating gelatine

The behaviour and effects of a spherical fragment penetrating a simulant and those of biological tissue are similar. To accurately describe the interaction between spherical fragments and muscle tissue, this study first discusses the wounding mechanism and establishes a mechanical model considering the effects of strain rate based on the properties of gelatine, which is a widely used representative simulant in physical surrogates for muscle tissue. Subsequently, experiments wherein gelatine was penetrated by spherical fragments with diameters of 3, 4, and 4.8 mm were conducted. The inertial and viscous resistance coefficients were identified using the least squares method and the experimental results obtained for the 4-mm spherical fragment. Numerical calculations show that the mechanical model agrees well with the experimental values. Further, the mechanical model's ability to adequately describe the motion of spherical fragments penetrating gelatine with good generality is proved. The proposed model can therefore provide a scientific basis for small arms ammunition design and protection evaluation.

Flywheel Inertial Resistance vs Heavy Slow Resistance in Patellar Tendinopathy

Flywheel Inertial Resistance vs Heavy Slow Resistance in Patellar Tendinopathy

A Multilayer Polymer-Film Inertial Microfluidic Device for High-Throughput Cell Concentration.

We report here a novel multilayer polymer-film inertial microfluidic (MPIM) device with complex three-dimensional (3D) fluidic paths for realizing the massive parallelization of multiplexing functional channels. The proposed MPIM device is fabricated by simply stacking different polymer-film channel layers and adhesive layers. As a prototype demonstration, an MPIM device with multiplexing radially arrayed serpentine channels has been designed and fabricated. Seven functional layers are stacked in a vertical direction to create the 3D fluidic paths for realizing the functions of inertial cell concentration, fluid convergence, and flow resistance adjustment in an all-in-one device with a thickness of only 1.4 mm. Then, the physics and the concentration performances of our MPIM device are explored. The results indicate that our MPIM device is capable of concentrating various particles at a throughput up to 8 mL/min. Finally, we successfully apply our MPIM device to the high-throughput concentration of microalgae and trace tumor cells from large background fluids. We envision the wide application of our MPIM device as a low-cost "on-chip centrifuge" for the concentration of various bioparticles.

Flow dynamic in a packed bed filled with Ni‐Al2O3 porous catalyst: Experimental and numerical approach

AbstractNumerical simulations and experiments have been carried out to explore the effect of particle shapes on the pressure drop and the loss factor in a packed fixed bed filled with a porous catalyst. The packed bed is presented by the Ni‐Al2O3 catalyst of the different shapes. The commercial program ANSYS Fluent is used for the analysis; more than 20 mln cells are used for computational fluid dynamics (CFD) modeling. The catalyst particles were set as a porous medium with the viscous resistance coefficients and the inertial resistance coefficients. The comparison of the pressure drops between the experimental and simulation results show a good correlation with the divergence of results <8%. To determine the effect of the porosity properties of the medium on the numerical results, two cases of CFD modeling were realized (with taking into account the porous medium properties and without it). The discrepancy between results increases with an increasing gas flow rate.

Estimation of the Non‐Darcy Coefficient Using Supercritical CO2 and Various Sandstones

AbstractNon‐Darcy flow (also known as high‐velocity flow, inertial flow, etc.) often occurs in the near‐well region of a reservoir during injection or production. This flow needs to be characterized and its origins fully understood, as it is a critical factor in reducing well productivity. The Forchheimer equation, which describes fluid flow considering an inertial effect, can be adopted to analyze non‐Darcy flow. In particular, the non‐Darcy coefficient in the equation represents inertial resistance in a porous medium and is an empirical value that depends on the pore geometry and fluid properties. This study, as part of research on geological CO2 storage, reports non‐Darcy flow tests with a high flow rate and examines the non‐Darcy coefficient by using supercritical CO2 and various sandstones. The dependence of the coefficient on the properties of the supercritical CO2 was also assessed in a series of non‐Darcy tests under different pore pressures. The coefficient varied with the properties of the supercritical CO2 and sandstone. As the permeability of sandstone increased, the non‐Darcy coefficient decreased nonlinearly and converged to a value. The results also indicate that the coefficient is reduced with a decreasing ratio of density to viscosity for the supercritical CO2. An equation predicting the coefficient was derived, having the advantage that both the hydraulic properties of rock and the fluid properties can be considered simultaneously in a dimensionally correct analysis.

Optimal Design of Piping Systems Using a Vibration Control Device Generating an Inertial Resistance Force

Optimal Design of Piping Systems Using a Vibration Control Device Generating an Inertial Resistance Force

Permeability of the porous Al2O3 ceramic with bimodal pore size distribution

Porous Al2O3 ceramics with bimodal pore size distribution were fabricated by partial sintering with monodispersed PMMA micro balls as pore agent. The porosity of the fabricated porous Al2O3 is increased with content of the pore agent increase, the bulk density and bending strength are decreased, accordingly. Relations between pressure drop and flow velocity of the air through the porous Al2O3 fit the Forchheimer's equation well for compressible fluid. Due to pores introduced by the pore agent, the Darcy permeability and inertial permeability of the porous Al2O3 are increased obviously. For given flow velocity, with increase of the PMMA content, the Forchheimer's number of the fluid through the porous Al2O3 is decreased, which results in decrease of the inertial resistance ratio to the total pressure drop. The porous Al2O3 ceramics with pores introduced by the monodispersed PMMA micro balls show higher permeability while the filtration selectivity is not deteriorated.

Experimental Investigation of Forchheimer Coefficients for Non-Darcy Flow in Conglomerate-Confined Aquifer

A conglomerate-confined aquifer (CCA) plays an important role in affecting the safety and environmental protection during energy mining. In this study, the Forchheimer coefficients and associated seepage characteristics of the CCA were studied for different hydrogeological conditions via integrating theoretical analysis, hydromechanical experiment, and field investigation. Empirical models related to the intrinsic permeability (k) and inertial resistance (β) were developed based on theoretical and experimental solutions, governed by the parameters of particle size, initial porosity, and stress. The non-Darcy flow was obtained through experiments conducted with different ratios of the aggregate particle subjected to stress ranging from 1.43 MPa to 4.38 MPa, and a discharge model associated with k and β was proposed. The aggregate particle and filling material of the CCA presented positive and negative effects on the interconnected pores, respectively, accompanied by wedging and wall effects. Distribution state of the aggregate particle and the filling material was affected by the stress, resulting in the reduction of the hydraulic conductivity and the weakening of the wedging and wall effects in the CCA. In addition, the transportation effect and broken effect occurred for the lower and higher stress situations and contributed to the shrinkage of the interconnected pores. Finally, the models of the CCA were validated using a normalized objective function (NOF), a linear slope γ function, and field measurements.

Influence of inertial resistance squat exercise protocol based on novel exercise intensity determination on physical fitness of older adult women

<p>The aim of the study was to examine practical implications and actual effects of the 8-week progressive resistance exercise protocol with the custom-made inertial device on sit-to-stand, 6- MWT, functional reach, up-and-go test results and Rate of Perceived exertion (RPE) among older adult women (age 65-74). Thirty-seven healthy volunteers were randomly assigned to the control group (n = 11) and to two exercise – inertial (n = 12) and traditional (n = 14) – groups. The participants performed hip belt squats on the inertial device and kettlebell squats, respectively. Exercise intensity was relatively adjusted using mass moment of inertia (MMI) of the cylindrical weight and %1RM. Time under tension was equalized between groups by the type of the exercise executed. Tests were performed before and after the intervention. Moreover, RPE was monitored after each exercise set. We used two-way repeated measures ANOVA to assess exercise-related differences in test results and to assess intensityrelated differences in RPE. The Senior Fitness Test results significantly differed in pre and post measurements, regardless of the group. A significant time x group interaction was only found in Sit-to-stand test results. RPE results significantly varied from each other across intensities. Statistically different results among groups were only found at the highest intensity (70%). The results indicate that inertial resistance exercise using the novel exercise intensity determination on the inertial device is a useful and less strenuous alternative to traditional resistance exercise among older adult women while performing squats.</p>

Deactivation of gyroscopic inertial forces

An inertial gyroscope in engineering manifests several unexplainable properties which physical nature is still unknown in classical mechanics. The new study demonstrates that the origin of the gyroscopic effects is more complex than presented in known publications. The gyroscopic effects manifest the inertial resistance and precession torques acting around different axes. The first torque is generated by the centrifugal and Coriolis forces and the second one by the common inertial forces and the change in the angular momentum. Blocking of the gyroscope motion around one axis deactivates the resistance torques but the precession torques are acting and the gyroscope turns under the action only of the gravity force. These phenomena are the manifestation of the unknown property of a physical matter that represents the new challenge for the researchers of classical mechanics. Newton’s laws are justified for the simple action, but for complex one should be formulated, validated and written new physical laws. For the example, the rotation of the mass around two axes demonstrates the disappearance of the inertial forces that contradicts the principles of physics. This work presents the mathematical model and practical validation of the deactivation of the inertial forces for the spinning rotor around two axes.

Evaluation of the Non-Darcy Effect of Water Inrush from Karst Collapse Columns by Means of a Nonlinear Flow Model

Karst collapse columns (KCCs) are naturally formed geological structures that are widely observed in North China. Given their influence on normal mining operations and the progress of mining work, collapse columns pose a hidden danger in coal mining under the influence of manual mining. By communicating often with the aquifer, the water inrush from KCCs poses a serious threat to construction projects. This paper adopts three flow field models, namely, Darcy aquifer laminar flow, Forchheimer flow, and Navier–Stokes turbulent flow, based on the changes in the water inrush flow pattern in the aquifer and laneway, and uses COMSOL Multiphysics software to produce the numerical solutions of these models. As the water inrush flow velocity increases, the Forchheimer flow shows the effect of additional force (inertial resistance) on flow in KCCs, in addition to the effect of viscous resistance. After the joint action of viscous resistance and inertial resistance, the inertial resistance ultimately dominates and gradually changes the water inrush from the KCCs to fluid seepage. Forchheimer flow can comprehensively reflect the nonlinear flow process in the broken rock mass of KCCs, demonstrate the dynamic process from the Darcy aquifer to the final tunnel turbulence layer, and quantitatively show the changes in the flow patterns of the water inrush from KCCs.

Early Functional and Morphological Muscle Adaptations During Short-Term Inertial-Squat Training.

Purpose: To assess early changes in muscle function and hypertrophy, measured as increases in muscle cross-sectional areas (CSAs) and total volume, over a 4 weeks inertial resistance training (RT) program.Methods: Ten young RT-naive volunteers (age 23.4 ± 4.1 years) underwent 10 training sessions (2–3 per week) consisting of five sets of 10 flywheel squats (moment of inertia 900 kg⋅cm2). Magnetic resonance imaging (MRI) scans of both thighs were performed before (PRE), and after 2 (IN) and 4 (POST) weeks of training to compute individual muscle volumes and regional CSAs. Scans were performed after ≥96 h of recovery after training sessions, to avoid any influence of acute muscle swelling. PRE and POST regional muscle activation was assessed using muscle functional MRI (mfMRI) scans. Concentric (CON) and eccentric (ECC) squat force and power, as well as maximal voluntary isometric contraction force (MVIC) of knee extensors and flexors, were measured in every training session.Results: Significant quadriceps hypertrophy was detected during (IN: 5.5% ± 1.9%) and after (POST: 8.6% ± 3.6%) the training program. Increases in squat force (CON: 32% ± 15%, ECC: 31 ± 15%) and power (CON: 51% ± 30%, ECC: 48% ± 27%) were observed over the training program. Knee extensor MVIC significantly increased 28% ± 17% after training, but no changes were seen in knee flexor MVIC. No correlation was found between regional muscular activation in the first session and the % of increase in regional CSAs (r = -0.043, P = 0.164).Conclusion: This study reports the earliest onset of whole-muscle hypertrophy documented to date. The process initiates early and continues in response to RT, contributing to initial increases in force. The results call into question the reliability of mfMRI as a tool for predicting the potential hypertrophic effects of a given strengthening exercise.

Numerical simulation of aneurysmal haemodynamics with calibrated porous-medium models of flow-diverting stents

Modelling flow-diverting (FD) stents as porous media (PM) markedly improves the efficiency of computational fluid dynamics (CFD) simulations in the study of intracranial aneurysm treatment. Nonetheless, the parameters of PM models adopted for simulations up until now were rarely calibrated to match the represented FD structure. We therefore sought to evaluate the PM parameters for a representative variety of commercially available stents, so characterising the flow-diversion behaviours of different FD devices on the market.We generated fully-resolved geometries for treatments using PED, Silk+, FRED, and dual PED stents. We then correspondingly derived the calibrated PM parameters—permeability (k) and inertial resistance factor (C2)—for each stent design from CFD simulations, to ensure the calibrated PM model has identical flow resistance to the FD stent it represents. With each of the calibrated PM models respectively deployed in two aneurysms, we studied the flow-diversion effects of these stent configurations.This work for the first time reported several sets of parameters for PM models, which is vital to address the current knowledge gap and rectify the errors in PM model simulations, thereby setting right the modelling protocol for future studies using PM models. The flow resistance parameters were strongly affected by porosity and effective thickness of the commercial stents, and thus accounted for in the PM models. Flow simulations using the PM stent models revealed differences in aneurysmal mass flowrate (MFR) and energy loss (EL) between various stent designs.This study improves the practicability of FD simulation by using calibrated PM models, providing an individualised method with improved simulation efficiency and accuracy.

Effect of Porous Baffles on the Energy Performance of Contact Tanks in Water Treatment

Three-dimensional numerical simulations are performed to evaluate the effect of porous baffles on the efficiency of water treatment contact tanks. A second-order accurate numerical model is employed for the solutions of unsteady flow and tracer transport through the porous baffles. The flow through the porous medium is characterized while using the Darcy-Forchheimer relationship. Large Eddy Simulation (LES) model is used to simulate the instantaneous mixing of the tracer in the chambers of the contact tank. Three different porosities are considered to evaluate the effect of porosity on the hydraulic and mixing efficiencies of the contact tank. Simulated time-averaged flow field shows that porous baffles that are placed at the entrance of each chamber could successfully mitigate short-circuiting and yield plug-flow conditions through the system for low porosities. Flow in the contact tank becomes laminar as the flow velocities decrease due to viscous effects and inertial resistance in the porous zone. For this case, the tracer is transported with bulk flow through the system and leaves the contact tank with a high peak seen in the Residence Time Distribution (RTD) plot. Porous layer increases the hydraulic efficiency of the conventional design from “poor” to “good” according to the baffling factor and increases the overall efficiency from “compromising” to “good” according to the AD index. Comparison of the performance of the porous layer with the previously developed slot-baffle design shows that the slot-baffle design increases the efficiency of the tank with increasing dispersion effects, whereas the porous design increases hydraulic efficiency and reduces the dispersion effects. While the porous design reduces energy efficiency by 33% due to a drastic increase in drag in the flow through porous zone, the slot-baffle design increases the energy efficiency of the conventional design by 67%.

Experimental and numerical study of flow in expanded metal plate for water electrolysis applications

Polymer electrolyte membrane water electrolysis (PEMEC) is a high-yield technique for hydrogen generation from renewable energy. One challenge for commercialisation of the technology is a low-cost and highly efficient flow plate. Flow plates are one of the most expensive parts of an electrolysis system, therefore a thorough study on alternative flow plate manufacturing methods pays off. Expanded metals have low manufacturing cost. Even though they are being used in different industries from electrochemistry to ventilation and air conditioning systems, there is little information available on their fluid flow behaviour. In this paper, the distribution of gas and liquid flow in expanded metal is analysed. Expanded metal flow resistance properties such as porosity, permeability and inertial resistance for two different sizes in both horizontal and vertical directions are determined. Alongside the experiments, two different computational fluid dynamic (CFD) simulations of flow in the experimental setup and the structure of the expanded metal was done.

A new simplified method for measuring the permeability characteristics of highly porous media

Fluid flow through highly porous media is important in a variety of science and technology fields, including hydrology, chemical engineering, convections in porous media, and others. While many methods have been available to measure the permeability of tight solid materials, such as concrete and rock, the technique for measuring the permeability of highly porous media is limited (such as gravel, aggregated soils, and crushed rock). This study proposes a new simplified method for measuring the permeability of highly porous media with a permeability of 10−8–10−4 m2, using a Venturi tube to gauge the gas flowing rate through the sample. Using crushed rocks and glass beads as the test media, we measure the permeability and inertial resistance factor of six types of single-size aggregate columns. We compare the testing results with the published permeability and inertial resistance factor of crushed rock and of glass beads. We found that in a log-log graph, the permeability and inertial resistance factor of a single-size aggregate heap increases linearly with the mean diameter of the aggregate. We speculate that the proposed simplified method is suitable to efficiently test the permeability and inertial resistance factor of a variety of porous media with an intrinsic permeability of 10−8–10−4 m2.

Modeling human orthostatic responses on the Moon and on Mars.

Since manned missions to the Moon and Mars are planned, we conducted active standing tests with lunar, Martian, terrestrial, and 1.8 loads of inertial resistance (+Gz) modeled through defined parabolic flight maneuvers. We hypothesized that the cardiovascular response to active standing is proportional to the +Gz load. During partial-+Gz parabolic flights, 14 healthy test subjects performed active stand-up maneuvers under 1 +Gz, lunar (0.16 +Gz), Martian (0.38 +Gz), and hyper inertial resistance (1.8 +Gz) while heart rate and finger blood pressure were continuously monitored. We quantified amplitudes and timing of orthostatic response immediately following standing up. The maximum early heart rate increase was 21 (SD ± 10)bpm with lunar, 23 (± 11)bpm with Martian, 34 (± 17)bpm with terrestrial +Gz, and 40 (± 11)bpm hyper +Gz. The time to maximum heart rate increased gradually with increasing loads of inertial resistance. The transient blood pressure reduction was most pronounced with hyper +Gz but did not differ significantly between lunar and Martian +Gz. The mean arterial pressure nadir was reached significantly later with Martian and lunar compared to 1 +Gz. Paradoxically, the time for blood pressure to recover was shortest with terrestrial +Gz. While load of inertial resistance directly affects the magnitude of the transient blood pressure reduction and heart rate response to active standing, blood pressure stabilization is most rapidly attained during terrestrial +Gz. The observation might suggest that the human cardiovascular system is tuned to cope with orthostatic stress on earth.

Overturning stability of L-shaped rigid barriers subjected to rockfall impacts

Reinforced concrete barriers are commonly used as defence measures in hilly areas to contain falling boulders and landslide debris. These barriers are conventionally designed to satisfy the conditions of force and momentum equilibrium with a factor of safety. A major limitation of this approach is that the inertial resistance of the barrier is neglected such that the design could be over-conservative. This paper presents a novel displacement-based approach for the assessment of overturning stability of rigid L-shaped barriers subjected to rockfall impacts. Analytical solutions, which are derived based on conservation of momentum and energy, are used to take into account the contributions of the self-weight and, thus, the inertial resistance of the barrier in resisting an impact. The actual amount of energy transferred from the impacting boulder to the barrier is considered by including the coefficient of restitution between the two objects. The accuracy of the analytical solutions has been confirmed by laboratory impact experiments. Numerical assessments conducted using the new solutions indicate that a reasonably sized rigid barrier, due to its own inertial resistance, may adequately withstand the impact action of a heavy boulder rolling down a hillslope without relying on any anchorage to its support. A range of geometric design of the barriers with L-shaped cross sections also has been considered and analysed. The new approach presented in this paper is easy to apply in practice and will be useful for engineers designing concrete barriers as passive rockfall mitigation measures.

New Correlative Models to Improve Prediction of Fracture Permeability and Inertial Resistance Coefficient

Presence of fracture roughness and occurrence of nonlinear flow complicate fluid flow through rock fractures. This paper presents a qualitative and quantitative study on the effects of fracture wall surface roughness on flow behavior using direct flow simulation on artificial fractures. Previous studies have highlighted the importance of roughness on linear and nonlinear flow through rock fractures. Therefore, considering fracture roughness to propose models for the linear and nonlinear flow parameters seems to be necessary. In the current report, lattice Boltzmann method is used to numerically simulate fluid flow through different fracture realizations. Flow simulations are conducted over a wide range of pressure gradients through each fracture. It is observed that creeping flow at lower pressure gradients can be described using Darcy’s law, while transition to inertial flow occurs at higher pressure gradients. By detecting the onset of inertial flow and regression analysis on the simulation results with Forchheimer equation, inertial resistance coefficients are determined for each fracture. Fracture permeability values are also determined from Darcy flow as well. According to simulation results through different fractures, two parametric expressions are proposed for permeability and inertial resistance coefficient. The proposed models are validated using 3D numerical simulations and experimental results. The results obtained from these two proposed models are further compared with those obtained from the conventional models. The calculated average absolute relative errors and correlation coefficients indicate that the proposed models, despite their simplicity, present acceptable outcomes; the models are also more accurate compared to the available methods in the literature.

Modelling of a stirling cryocooler regenerator under steady and steady – periodic flow conditions using a correlation based method

The performance of a Stirling cryocooler depends on the thermal and hydrodynamic properties of the regenerator in the system. CFD modelling is the best technique to design and predict the performance of a Stirling cooler. The accuracy of the simulation results depend on the hydrodynamic and thermal transport parameters used as the closure relations for the volume averaged governing equations. A methodology has been developed to quantify the viscous and inertial resistance terms required for modelling the regenerator as a porous medium in Fluent. Using these terms, the steady and steady – periodic flow of helium through regenerator was modelled and simulated. Comparison of the predicted and experimental pressure drop reveals the good predictive power of the correlation based method. For oscillatory flow, the simulation could predict the exit pressure amplitude and the phase difference accurately. Therefore the method was extended to obtain the Darcy permeability and Forchheimer’s inertial coefficient of other wire mesh matrices applicable to Stirling coolers. Simulation of regenerator using these parameters will help to better understand the thermal and hydrodynamic interactions between working fluid and the regenerator material, and pave the way to contrive high performance, ultra-compact free displacers used in miniature Stirling cryocoolers in the future.