Numerical Investigation Research Articles

Numerical investigation on flow-induced wall shear stress variation of metastatic cancer cells in lymphatics with elastic valves.

Hematogenous metastasis occurs when cancer cells detach from the extracellular matrix in the primary tumor into the bloodstream or lymphatic system. Elucidating the response of metastatic tumor cells in suspension to the flow conditions in lymphatics with valves from a mechanical/fluidic perspective is necessary. A physiologically relevant computational model of a lymphatic vessel with valves was constructed using fully coupled fluid-cell-vessel interactions to investigate the effects of lymphatic vessel contractility, valve properties, and cell size and stiffness on the variations in magnitude and gradient of the flow-induced wall shear stress (WSS) experienced by suspended tumor cells. Results indicated that the maximum WSSmax increased with the increments in cell diameter, vessel contraction amplitude, and valve stiffness. The decrease in vessel contraction period and valve aspect ratio also increased the maximum WSSmax. The influence of the properties of the valve on the WSS was more significant among the factors mentioned above. The maximum WSSmax acting on the cancer cell when the cell reversed the direction of its motion in the valve region increased by 0.5-1.4 times that before the cell entered the valve region. The maximum change in WSS was in the range of 0.004-0.028 Pa/µm depending on the factors studied. They slightly exceeded the values associated with breast cancer cell apoptosis. The results of this study provide biofluid mechanics-based support for mechanobiological research on the metastasis of metastatic cancer cells in suspension within the lymphatics.

Strain-induced enhancement of surface self-diffusion on strontium titanate (001) surfaces.

We present a numerical investigation of self-diffusion on strontium titanate TiO2-terminated (001) surfaces via density functional theory. Our calculations first indicate that Ti has the highest diffusion barrier with approximately 2.20 eV, thus representing the rate-limiting step for surface self-diffusion. Furthermore, the higher energy barriers of O and Ti in comparison to O2and TiO2indicate electronic activity with the surface atoms. Under the consideration of equi-biaxial strain as it would be encountered in e.g. heteroepitaxial thin films, the diffusion barriers for surface self-diffusion decrease for both compressive and tensile strains between -6% and 2%. For larger strains, we observe plastic deformations. This possibility to lower the energy barrier paves the way for accelerated and possible new mechanisms of surface diffusion and reconstruction of strontium titanate structures in a wide range of applications.

Seismically resistant progressive collapse behavior of infilled frame structures under seismic loads and column loss: A numerical investigation

This research investigated the seismic performance of multi-story reinforced concrete (RC) frames with infilled walls. The study employed a two-step numerical approach: first, a verification process ensured the model's accuracy by comparing it to past experimental results. Following validation, a parametric study explored various factors influencing the frames' behavior. These factors included the number of stories (3, 6, and 12), the earthquake ground motion (Vrancea, El Centro, and Kahramanmaraş), and the effect of removing an internal column. Additionally, the study examined the impact of incorporating polypropylene (P.P.) fibers into different parts of the structure: the RC frame itself, the mortar between infill wall bricks, or both. The findings revealed significant improvements in seismic performance due to the presence of infill walls. In the three-story frame, the wall reduced plastic drift by a remarkable 98.9 %. Furthermore, strengthening with P.P. fibers demonstrated exceptional effectiveness. For example, on the first floor of the three-story frame, the maximum drift value dropped from 0.751 to a 0.004 for the IRCPM model (fibers in the infill wall mortar only) and even lower (0.003) for the IPPM model (fibers in both the RC frame and infill wall mortar). These results highlight the potent ability of P.P. fibers to improve earthquake resistance. The study also assessed the efficacy of strengthened infill walls as partial replacements for lost columns. When an internal column was removed, the presence of a P.P. fiber-reinforced wall (IPRCL model) helped mitigate the structural impact, reducing the base shear force by 11 % compared to the control model without fibers (CIRCL). Similar trends were observed in taller frames. While including fibers in the RC frame of the 6-story model with a removed column resulted in an 11 % decrease in base shear force, models with fibers in the wall components of the 12-story frame exhibited a 31.62 % increase in base shear force after column removal.

A Numerical Investigation of Particle Swarm Optimization to Improve Film-Cooling Effectiveness from Converging Slot Hole

A Numerical Investigation of Particle Swarm Optimization to Improve Film-Cooling Effectiveness from Converging Slot Hole

Rebound micro-cavitation dynamics with ultrasound fields during histotripsy: a numerical investigation

Rebound micro-cavitation dynamics with ultrasound fields during histotripsy: a numerical investigation

Experimental and numerical investigation on deck system of a 102 m simply supported prestressed UHPC box-girder highway bridge

To address two main challenges (excessive mid-span deflections and numerous cracks in the main girder) in long-span prestressed concrete (PC) box-girder bridges, this paper proposes a long-span simply-supported UHPC box-girder bridge. In comparison to conventional PC box-girder bridges with three-dimensional prestress, the proposed UHPC box-girder consists only one-dimensional (longitudinal) prestress, and the thickness of the bottom/top plate and web of the UHPC box-girder are relatively thin and are strengthened with dense diaphragms and stiffening ribs. The 4th Beijiang River Bridge adopts this type of bridge with a span of 102 m, which is the longest span simply supported prestressed UHPC box-girder highway bridge in the world. Considering the fact that the thickness of the top plate of the UHPC box-girder is relatively thin (only 20 cm) and the transverse prestress is removed from the top plate, thus, under the direct action of wheel loads, the risk of bridge deck cracking may correspondingly increase. To investigate the mechanical behavior of the deck system of UHPC box-girder bridges, a 1:2 scaled experimental specimen associated with the field bridge is tested. The mechanical behavior of the new deck system is investigated and discussed. It is found that because the support strength of the stiffening rib is significantly weaker than that of the web, the UHPC deck slab should still be regarded as a two-way slab rather than a one-way slab in the elastic stage. In addition, although the test load location is unfavorable to the UHPC deck slab and the first crack appears on the UHPC deck slab, this deck system finally suffers from bending failure of the transverse rib. Furthermore, finite element analysis is carried out to study the mechanical behavior of this new deck system. Parametric analysis considers some factors including the reinforcement ratio in the transverse rib, the height of the transverse rib, and the space between transverse ribs. The results provide a good reference for design and optimization in the new deck system of UHPC box-girder bridges.

Numerical Investigation on the Influence of Continuous Rotating Backpropagation Pressure Wave on Turbine Performance

Abstract Researches have shown that the use of a continuous detonation afterburner can improve the propulsion performance of aero engine. However, backpropagation pressure waves (BPW) generated by the pressure gain of detonation will affect the internal flow and performance of turbine. This article simulates BPW through a custom function, and investigates the effects of BPW amplitude, rotation frequency, and propagation mode on turbine performance through three-dimensional simulation. The results show that as the pressure amplitude of the BPW increases, the pressure oscillation at each section of the turbine increases and a local subcritical flow state will appear, leading to the decrease of turbine flowrate and turbine power, as well as an intensification of instantaneous turbine power fluctuations. As the rotation frequency of the BPW increases, the pressure oscillation at each section of the turbine gradually decreases. The flowrate and power of the turbine do not change much, but turbine efficiency gradually decreases. Compared to the aligned mode, the turbine performs better under the influence of BPW in misaligned mode. Compared to the single-wave mode, the fluctuation of transient turbine power is lower under the influence of BPW in the multiwave mode excluding collision mode. Finally, the constraints of equal flowrate region and equal turbine power line on the peak-to-peak value of the BPW were analyzed when the joint operation of the turbine and compressor was not affected. The rotation frequency and mode of BPW will affect the flowrate region and power line.

Numerical and experimental investigation of solute transports through different types of dialyzer membrane

The flow and mass transport through different membrane types from different hemodialyzers are investigated in a co-current direction to emphasize the effect of solute diffusion through the dialyzer membranes. The numerical model consists of the blood flowing in a hollow fiber surrounded by a dialysate flow, where the mass transport and fluid flow were simultaneously calculated. The high flux dialyzers considered in the present study are FINEFLUX FIX-210S eco, ELISIO-210HR, and PEPA FDY-21B, which differ mainly in characteristics of the membrane structure and surface. Urea and maltodextrin solutions are used as model solutes to consider the effect of molecular size difference. The numerically predicted outlet concentrations closely align with experimental values, where the variation between predicted and measured values remain below 10% across all dialyzer types for urea solutions, and specifically below 8% for maltodextrin solution. Among the various dialyzers tested, FINEFLUX membrane could provide the highest maltodextrin clearance (83.09 ml/min) and overall mass transfer area coefficient (KoA) (119.56 ml/min) potentially due to its fast-diffusion characteristic. In this co-current flow study, the results suggest that urea transport is primarily influenced by flow control with minimal impact from boundary layers, while maltodextrin transport is predominantly governed by diffusion control.

The use of nonlinear guided-wave features for detection and assessment of intermetallic compounds within dissimilar joints – an experimental investigation

Abstract Welding dissimilar materials is widely employed in industrial construction and manufacturing to enhance cost-effectiveness and performance, often utilizing non-fusion methods like solid-state and high-energy beam welding. However, a significant challenge is the formation of intermetallic compounds (IMCs) at the joint interface, which can weaken the bond and increase brittleness, leading to hidden internal cracks. Nonlinear ultrasound detection methods are employed as advanced, non-destructive testing techniques for early damage inspection in various materials. This research investigates the assessment of the thickness of the intermetallic layer within dissimilar joints using non-linear ultrasound-wave features. Numerical and experimental investigations were performed using four friction stir welding (FSW) lap joints, between AA5052-H32 aluminum and ASTM 516-70 steel, with various intermetallic thicknesses. The methodology involved examining the generation of second-order harmonic frequency by exciting Lamb waves (LW) at specific frequencies. To determine the necessary LWs' excitation frequency, synchronism, and non-zero power flux conditions were employed. The collected signals were measured and analyzed in the time and frequency domains to understand the behavior of the non-linear parameter β′ with the thickness of the intermetallic layer. The results show that β′ changes in a linear manner with the thickness of the intermetallic compound layer (several micrometers in thickness). This provides strong evidence that nonlinear LW features are sensitive to microstructural variations in the FSW joints, which enables them to effectively evaluate their strength.

Numerical investigation of pulsating bubble dynamics in shallow and deep-sea underwater explosions

Numerical investigation of pulsating bubble dynamics in shallow and deep-sea underwater explosions

Numerical investigation of the asymptotic behavior of tape springs

Numerical investigation of the asymptotic behavior of tape springs

Numerical investigation of the transient fluid flow and heat transfer behavior in self-driven natural circulation cooling loop

An innovative open natural circulation system is proposed in this work, which utilizes the difference of the heat flux loaded on different parts of the pipe to form a self-circulation flow of working fluid. Via CFD simulation established by embedding self-programmed code into commercial software, the transient performance of a three-dimensional natural circulation loop is studied. The results indicate that: applying uniform heat flux on the wall of the loop, the fluid flow state successively experiences three stages, i.e., liquid expansion, partial circulation, and phase change, and finally a vapor plunger blocks the pipe, leading to local heat transfer deterioration and temperature increase; applying non-uniform heat flux, the fluid can be driven to form self-circulation flow, which can not only cool the structure via convection, but also prevent bubbles from accumulating, stabilizing the maximum temperature of the system around the boiling point; further for the loop with a more complex configuration, the self-circulation can be also started but with different start modes. Therefore, the new natural circulation system can achieve effective and adaptive cooling according to the external thermal environment, avoid fluctuation and vapor block phenomenon caused by violent phase change, and reduce the driving equipment and control unit. This work provides a reference for the design of the natural circulation system applied in a non-uniform heating environment. Through transient numerical simulation of the start-up stage, the fluid flow, phase change, and heat transfer characteristics in the natural circulation loop are studied, and the start mode and mechanism are analyzed.

Shear mechanism of UHPC epoxied‐keyed joints in PSUBs: Experimental and numerical investigations

AbstractPrecast segmental ultra‐high‐performance concrete bridge presents broad application prospects. UHPC keyed joints play significant roles in the structural performance of such bridges, which require systematic investigation to comprehend their shear behavior and mechanism thoroughly. This study aimed to explore the shear mechanism of UHPC epoxied‐keyed joints. Experimental and numerical investigations were conducted to investigate the influence of key size, key number, key angle, and reinforcement form on the shear performance. The test results showed that the failure mode was primarily affected by the key number and reinforcement form, which can be divided into three categories: direct shear, segmental shear, and stepwise shear failure. The large‐keyed joints exhibited superior shear performance compared to the three‐keyed joints. The initial shear stiffness, ultimate bearing capacity, and normalized shear stress were 15%, 5.3%, and 5.6% higher, respectively. Furthermore, the mechanism of the two reinforcement forms was clarified. The key rebars mainly improve the ductility of the specimens, while the dowel action of the embedded rebars can enhance the shear efficiency and synergistic force ability of the joints. The numerical simulation results indicated that 2.7% was the best ratio of key rebar, and embedded rebars with larger diameters can strengthen the shear capacity and post‐peak performance of the joints.

Web crippling design of cold‐formed ultra‐high strength steel lipped channels under ITF loading: A numerical parametric investigation

AbstractIn recent years, there has been a compelling need to adopt cold‐formed ultra‐high‐strength steel (CFUSS) in the construction industry owing to its numerous advantages, such as a higher strength‐to‐weight ratio, flexibility in achieving desired shapes, and adaptability over longer spans. Among the various applications, CFUSS lipped channel sections are commonly used as purlins and joists in steel structural systems. However, these sections are susceptible to different failure modes, particularly web crippling, which presents significant challenges. Currently, the current design rules lack specific guidelines for estimating the web crippling capacity of CFUSS sections. To address this crucial gap, the present study focuses on a comprehensive numerical investigation of the web crippling response of CFUSS lipped channel sections under interior‐two‐flange (ITF) loading conditions. Finite element (FE) models were developed using the ABAQUS package, verified against published test data, and subsequently used in an extensive parametric study. The ultimate web crippling capacity obtained from the parametric study was used to evaluate the accuracy of the current design equations in various design standards. The findings revealed that the existing design equations inadequately predicted the ultimate web crippling capacity of CFUSS lipped channel sections subjected to the ITF loading condition. Consequently, a modified design equation is proposed, utilizing the same approach as the current design standards, and a new direct strength method (DSM) approach is developed and verified through reliability analysis. The proposed modified design equations offer promising solutions to ensure safer and more reliable design practices for CFUSS structures in the construction industry.

Numerical investigation on the deformation of railway embankment under normal faulting

Active faults in the earthquake region are consistently regarded as a potential geological hazard to the construction and operation of railway engineering. However, the effects of normal faulting on railway embankments have not been investigated thoroughly. For bridging this knowledge gap, three-dimensional finite element analysis considering the influence of faulting offset, the soil layer’s thickness, the fault dip angle and the embankment cross-fault angle are conducted to clarify the normal faulting effects on the railway embankment. Emphasis is given to the stress and strain characteristic in the fault rupture outcropping regions on the embankment, the deformation of the embankment centerline for design purposes, and the determination of the affected zones for railway embankment preservation. The analysis shows that the normal fault rupture outcropping regions on railway embankment are tensile yield in most cases. The existence of the soil layer and its thickening would widen the affected zones and the regions where the fault ruptures outcrops. The fault dip angle and the cross-fault angle of the embankment have a complex effect on the behaviors of the crossing embankment. The depth of the subsidence zone of the embankment would increase with the decrease of the fault dip angle and the large fault dip angle would change the primary fault rupture to be a compressive one directly above the fault line. If the embankment crosses the fault line obliquely, the curvature radius of the centerline would hardly meet the design code.

Experimental and numerical investigation on temperature analysis and process optimization in friction stir welding of CuZn40 brass alloys

Experimental and numerical investigation on temperature analysis and process optimization in friction stir welding of CuZn40 brass alloys

Numerical investigation on ground and structure response of ancient site in complex strata caused by groundwater fluctuation and rainfall

As more and more ancient sites are discovered around the world, protecting them in situ has become a challenge due to issues such as ground settlement and masonry wall leaks caused by groundwater fluctuation or rainfall. In this study, laboratory tests, borehole tests and field high‐density resistivity detections are conducted to obtain information for numerical modelling, including design parameters. A complex three‐dimensional hydrological–mechanical coupling model is then established to investigate ground settlement and wall deformation caused by groundwater fluctuation and rainfall. The seepage simulation results for the initial state are accurately verified by high‐density resistivity imaging. Both measured data and numerical results indicate that changes in a single water head point mainly result in wall settlement. The pattern of wall deformation changes from settlement to lateral deformation with an increase in the drawdown rate of groundwater level. Furthermore, delayed rainfall and high‐intensity rainfall can increase foundation settlement and wall deformation. Settlement deformation determines the upper limit of the global deformation when wall nodes are mainly affected. In contrast, if lateral spreading dominates wall deformation, it determines the lower limit of the global deformation. This study provides reference for in situ protection and foundation reinforcement of ancient sites.

Finite Element Analysis and Optimization of the Rotational Stiffness of Semi-Rigid Base Connection under Simultaneous Moment and Tension

The base connection is flexible, not fully pinned/fixed, implying a nonlinear moment–rotation relationship. This deviates from a linear response, where rotation is not directly proportional to the applied moment. Numerical investigations using the commercial software ABAQUS were conducted to analyze the steel base plate connections. The finite element (FE) models were verified against previous experimental results. Moreover, numerical findings of a comprehensive parametric investigation were conducted. The studied connections were examined with different configurations, including variations in the diameter, spacing, and number of the anchor bolts; the thickness of the base plate; and the applied axial force. The current study aims to use numerical results combined with the whale optimization algorithm (WOA) and classical genetic algorithm (GA) to derive a formulation for the moment–rotation (M-θr) relationship. The distinctive aspect of this formulation is that it aims to simulate the nonlinear rotational behavior exhibited by flexible base connections under combined moment and tension loads, while also considering various parameters such as bolt number/diameter and plate thickness. The findings indicate that the WOA is capable of obtaining an optimal equation for accurately simulating the M-Ɵr relationship. This underscores the ability of the WOA to effectively address the complexity of the problem and provide a reliable equation for predicting the rotational behavior of such connections. Consequently, the WOA method can be utilized to calculate the rotational stiffness at H/150, offering valuable support for engineering design processes.

Numerical investigation of soot formation in methane/n-heptane laminar diffusion flame doped with hydrogen at elevated pressure

The addition of hydrogen in a dual-fuel mode based on natural gas and diesel offers great potential for improving engine efficiency and reducing emissions. Therefore, detailed numerical simulations have been used to explore the effects of soot formation characteristics of natural gas-diesel dual-fuel engines doped by hydrogen at elevated pressure. Numerical simulations are compared with available experimental data, the effects of H2 addition on soot formation in laminar CH4 + n-heptane, H2 + CH4 + n-heptane, FH2 + CH4 + n-heptane diffusion flames at 2, 4, 6 and 8 atm are simulated, FH2 is added to separate the H2 chemical effects. The results show that the dilution and thermal effects of H2 inhibit soot formation, while the chemical effects of H2 promote soot formation under different pressures. The addition of H2 increases the concentration of H and OH radicals, which promotes the formation of C2H2 and benzene (A1). By simplifying the reaction path and analyzing the production rate of A1, the mechanism of H2 addition to promote A1 formation is illustrated. The concentrations of polycyclic aromatic hydrocarbon (PAH) pyrene (A4), benzo(ghi)fluoranthene (BGHIF) and benzo(a)pyrene (BAPYR) are inhibited at higher pressures that result in lower inception and condensation rates. Therefore, the increase of hydrogen abstraction acetylene addition (HACA) rate is the main reason for the increase of soot formation under chemical effects. While the O2 oxidation rate decreases and the OH oxidation rate increases, that is due to the decrease of O2 concentration and the increase of OH concentration in the soot formation area under chemical effects.

Numerical investigation gaseous ammonia basic jet and mixing characteristics in the constant volume vessel

Ammonia is considered a promising zero-carbon fuel under the dual-carbon targets. Systematically understanding ammonia's basic jet and mixing characteristics can promote its practical application in the engine field. Thus, a three-dimensional computational fluid dynamics (CFD) model of constant volume vessel (CVV) is established in this paper, and the forecasting abilities of the Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) models for the gaseous ammonia jet process are compared based on the experimental data. Then, the ammonia jet development rule and mixing characteristics under different ambient temperatures, ambient pressures, and fuel temperatures are investigated. The variation laws of key data such as penetration distance, jet area, ammonia mass concentration distribution, equivalence ratio, and turbulent kinetic energy are obtained and analyzed. The results show that during the injection process, the airflow on the left and right sides of the jet rotates in opposite directions. A higher temperature and lower pressure within the CVV lead to a larger flammable range for ammonia jets. Moreover, the distribution of ammonia mass concentration on the radial plane shows a dynamic development law with time, meaning that it first increases to a maximum value, then gradually decreases, and finally remains stable. The farther the radial plane is from the nozzle outlet position, the lower the ammonia mass concentration. In addition, the ammonia jet's turbulent kinetic energy has a large core region and symmetrical distribution along the central axis. At the beginning of the injection, the core length is small, gradually increasing with time and finally stabilizing.