Flow Conditions Research Articles

Aminolysis-mediated single-step surface functionalization of poly (butyl cyanoacrylate) microbubbles for ultrasound molecular imaging

Molecular ultrasound imaging with actively targeted microbubbles (MB) proved promising in preclinical studies but its clinical translation is limited. To achieve this, it is essential that the actively targeted MB can be produced with high batch-to-batch reproducibility with a controllable and defined number of binding ligands on the surface. In this regard, poly (n-butyl cyanoacrylate) (PBCA)-based polymeric MB have been used for US molecular imaging, however, ligand coupling was mostly done via hydrolysis and carbodiimide chemistry, which is a multi-step procedure with poor reproducibility and low MB yield. Herein, we developed a single-step coupling procedure resulting in high MB yields with minimal batch-to-batch variation. Actively targeted PBCA-MB were generated using an aminolysis protocol, wherein amine-containing cRGD was added to the MB using lithium methoxide as a catalyst. We confirmed the successful conjugation of cRGD on the MB surface, while preserving their structure and acoustic signal. Compared to the conventional hydrolysis protocol, aminolysis resulted in higher MB yields and better reproducibility of coupling efficiency. Optical imaging revealed that under flow conditions, cRGD- and rhodamine-labelled MB, generated by aminolysis, specifically bind to tumor necrosis factor-alpha (TNF-α) activated endothelial cells in vitro. Furthermore, US molecular imaging demonstrated a markedly higher binding of the cRGD-MB than of control MB in TNF-α activated mouse aortas and 4T1 tumors in mice. Thus, using the aminolysis based conjugation approach, important refinements on the production of cRGD-MB could be achieved that will facilitate the production of clinical-scale formulations with excellent binding and ultrasound imaging performance.Graphical

New insights on cavitating flows over a microscale backward-facing step

This study introduces the first experimental analysis of shear cavitation in a microscale backward-facing step (BFS) configuration. It explores shear layer cavitation under various flow conditions in a microfluidic device with a depth of 60 μm and a step height of 400 μm. The BFS configuration, with its unique characteristics of upstream turbulence and post-reattachment pressure recovery, provides a controlled environment for studying shear-induced cavitation without the complexities of other microfluidic geometries. Experiments were conducted across four flow patterns: inception, developing, shedding, and intense shedding, by varying upstream pressure and the Reynolds number. The study highlights key differences between microscale and macroscale shear cavitation, such as the dominant role of surface forces on nuclei distribution, vapor formation, and distinct timescales for phenomena like shedding and shockwave propagation. It is hypothesized that vortex strength in the shear layer plays a significant role in cavity shedding during upstream shockwave propagation. Results indicate that increased pressure notably elevates the mean thickness, length, and intensity within the shear layer. Instantaneous data analysis identified two vortex modes (shedding and wake modes) at the reattachment zone, which significantly affect cavitation shedding frequency and downstream penetration. The wake mode, characterized by stronger and lower-frequency vortices, transports cavities deeper into the channel compared to the shedding mode. Additionally, vortex strength, proportional to the Reynolds number, affects condensation caused by shockwaves. The study confirms that nuclei concentration peaks in the latter half of the shear layer during cavitation inception, aligning with the peak void fraction region.

Redesigning heat exchanger channels: A local entropy generation approach

This paper proposes a redesign technique for heat exchanger channels based on a Local Entropy Generation (LEG) analysis and numerical simulations. The approach first divides the computational domain into zones and then identifies the zones responsible for increasing irreversibilities due to viscous and heat transfer effects. By evaluating different geometric features and flow conditions, the wall shape is modified (zone by zone) with the configurations that offer the lowest local entropy generation rates. The redesigned channels demonstrate that sudden changes in geometry along the streamwise direction reduce the size of regions with high thermal entropy generation and promote the creation of vortices, thereby reducing the magnitude of thermal irreversibilities. Smooth wall shape transitions might not be desirable when the goal is to improve heat transfer. The redesign process enhances the thermal performance of the system without significantly increasing power demand. The proposed methodology is evaluated using three wavy channels with a non-uniform amplitude-to-wavelength ratio (β1,β2,andβ3) since they allow for better management of wall geometry. As demonstrated for case β1, the LEG analysis enables the construction of new channels with a thermal performance 3.9 % superior to those with a uniform amplitude-to-wavelength ratio of α = 0.16 (best-case scenario), but with approximately 20 % less pumping power. While this study employs wavy channels as a case study, the methodology is broadly applicable to various heat exchanger configurations, including trapezoidal, triangular, and zigzag channels, making it a versatile tool for improving thermodynamic performance across different designs.

Bijel-based mesophotoreactor with integrated carbon nitride for continuous-flow photocatalysis

The integration of continuous-flow technologies with heterogeneous photocatalysis has recently emerged as a promising strategy for the development of sustainable processes. Although conventional packed bed reactors have been extensively utilized in industrial catalytic applications, they face challenges related to energy transfer in the photocatalytic systems. This study presents an innovative approach to address this issue by integrating heterogeneous photocatalysts with an organic polymer, leading to the fabrication of a mesophotoreactor featuring a bijel-based structural configuration. This novel strategy involves hybridizing polypentadecalactone and in situ confining of carbon nitride in a bicontinuous porous mesoarchitecture. The structural and physicochemical properties of the resulting catalytic composite material are evaluated through an array of characterization methods, affirming the successful integration of carbon nitride within the overall structure. The unique bicontinuous porous architecture of the composite and its suitability for industrial applications is verified, as exemplified by its exceptional efficiency in the photodegradation of methylene blue (>99 %) under flow conditions and remarkable stability up to three reaction cycles. A mathematical model is developed to describe continuous photocatalytic processes occurring in the novel tubular mesophotoreactor, with a specific focus on the degradation of the methylene blue dye. This model is successfully validated, leading to results in agreement with the experimental measurements. Additionally, fluid dynamics simulations demonstrate that the mesophotoreactor design allows for the effective diffusion of light through its channels, resulting in higher irradiation levels compared to conventional systems such as packed bed reactors. The innovative design of the catalytic reactor presented in this work offers a versatile and efficient alternative to the conventional heterogeneous systems, significantly broadening the range of applications for photocatalytic processes.

Enhancing Hydraulic Performance and Discharge Efficiency of a Type-C Piano Key Weir Through Stage Incorporation

Weirs are hydraulic constructions typically employed in dam spillways and channel control structures. The shape and size of the crest will determine whether the weir is linear or non-linear. Of the two types, non-linear weirs are often selected due to their ability to allow different discharge levels at the minimal heads. A recently introduced variation of the non-linear kind is the piano key weir. This research undertakes a comprehensive analysis of the hydraulic functionality of the type-C piano key weir under conditions of free flow. The research methodology involved modifying the models by adding stages to the sides and monitoring the effect on the efficacy of discharge, represented by the discharge coefficient. The study further extrapolated formulae linking critical variables to the discharge coefficient, using dimensional analysis and SPSS software. The findings of this study revealed that the introduction of stages significantly bolstered the discharge coefficient in the altered models compared to the standard model. This enhancement was reflected in a 6% and 11% ascent with length expansion of the stages and a 6% and 8% rise with height increase of the stages. Additionally, the model's performance was augmented with a drop in the total head ratio

Mining of dynamic traffic-meteorology-atmospheric pollutant association rules based on eclat method

With the rapid increase of urban vehicles, the atmospheric compound pollutants, notably PM2.5 and O3, have significantly increased and seriously affected public health. Traffic and meteorological conditions are the primary influencing factors of pollutant concentrations, and their spatial and temporal changes affect the dispersion of pollutants. Increasing use of high-resolution big data offers opportunities to explore these correlations. More extensive quantitative studies are essential for effective air pollution control. This study presents an Eclat algorithm to quantitatively reveal the relationship between traffic, meteorology and pollutants with hourly and 5-minute scale data in the urban area of Guangzhou. We establish a research framework covering temporal pollution analysis, multifactor rule mining, and spatial effects. The results show that PM2.5 and O3 exhibit coordinated trends on the daily scale influenced by traffic flow and meteorology conditions, but on the hourly scale, they are negatively correlated. At the 5-minute scale, synchronized variations occur only during specific periods. This finer scale better identifies association rules for high-concentration pollutant scenarios, and non-roadside sites outperform roadside sites in mining these associations. For example, when humidity is below 37%, atmospheric pressure is 1016.2–1020.3 Pa, wind speed is 1.7–2.6 m/s, and the traffic volume on Jiefang North Road exceeds 635 vehicles every 5 min, there is a 92.86% probability that the PM2.5 concentration at GYQ (a non-roadside monitoring site) will exceed 127 μg/m3. These findings enhance our understanding of how dynamic traffic and meteorological conditions impact atmospheric pollutants and provide a scientific basis for regional collaborative pollution prevention.

Heat transfer characterization of SCO2 in non-uniformly heated rectangular cooling tubes under large mass flow and heat flux conditions

A Thermoelectric Conversion System (TECS) with SCO2 as the circulating mass can effectively mitigate the fuel heat sink and electrical energy shortage problems of hypersonic vehicles. However, there is still a lack of research on the use of SCO2 in the harsh thermal conditions in scramjet. In this paper, the heat transfer mechanism of SCO2 in rectangular cooling tubes are numerically analyzed for the first time based on the actual working environment of scramjet. The effects of uneven heat flux (q) axial and circumferential allocations and circumferential and axial tilting of the tube are innovatively considered. Meanwhile, we analyze the heat transfer mechanism of SCO2 under different operating parameters. The results show that the uneven allocation of axial q can suppress the heat transfer deterioration (HTD), and the overall heat transfer coefficient (HTC) can be increased by 11.68 % when the q allocation is Gaussian. The increase of the tube inclination angle can improve its heat transfer performance, and the local HTC can be increased by up to 5.64 % when θ2 = 180°.Increasing the mass flow rate (G) and inlet temperature (Tin) can increase the overall HTC of the tube. This paper can provide guidance for the design and improvement of TECS.

Effects of axisymmetric confinement on vortical structures emanating from round turbulent jets

Confined jets occur in many engineering applications including combustion chambers, jet pumps, and chemical reactors. The effects of axisymmetric confinement on the vortical structures identified in a turbulent jet are investigated using large eddy simulation at a Reynolds number of 30 000 (based on nozzle exit conditions) and expansion ratio (chamber-to-nozzle diameter ratio) of five. The results obtained from the confined jet are compared with those of a free jet under the same nozzle exit flow conditions. A prominent recirculation zone forms between the expanding jet and the confining wall, resulting in early shear layer distortion and a shorter interaction length in the confined jet (0.85 jet diameters) compared to the free jet (1.15 jet diameters). Using the λ2 criterion for vortex identification, two dominant structural modes are identified in the near-exit region of the free jet: ring and helical modes. However, in the confined jet, the helical mode is absent, and the turbulent confined fluid accelerates the breakup of the ring vortices. The interaction of the secondary line vortices with the breaking structures leads to the formation of new hairpin-like vortices, which also contribute to further vortex breakup. These results explain the enhanced mixing performance of confined jets as the mixing is directly tied to the breakup of large vortical structures. Proper orthogonal decomposition modes are also presented to identify the structures/events with the highest contribution to the total turbulent kinetic energy in both flow fields.

Exploring spatial beam shaping in laser powder bed fusion: High-fidelity simulation and in-situ monitoring

Laser beam shaping is a novel and relatively unexplored method for controlling the melt pool conditions during metal additive manufacturing (MAM) processes, but even so it still holds good promise for achieving site-specific tailored properties. In this work, a comprehensive numerical and experimental campaign is carried out to explore this subject within metal laser powder bed fusion (LPBF). More specifically, a multiphysics numerical model is implemented for simulating the heat and fluid flow conditions during LPBF of Ti6Al4V using arbitrary circular beam shapes with various power distributions spanning from a pure Gaussian beam to a pure ring beam profile. The model is subsequently coupled with cellular automata to describe the beam shape effects on the microstructure evolution. Model validation is carried out in a two-fold manner. First, we compare the predicted melt pool cross-section with the one from ex-situ single track experiments, and we find a deviation of less than 9% in melt pool dimensions. Secondly, advanced in-situ X-ray monitoring is carried out to unravel the melt pool dynamics and we find that the predicted morphology closely matches the in-situ X-ray results. Moreover, it is shown that at lower laser power, a bulge of liquid metal forms at the center of the melt pool when employing ring profiles, and this is ascribed to the absence of recoil pressure at the center of the ring beam. Furthermore, increasing the laser power seems to destabilize the melt pool regime, as the central bulge transforms into a liquid metal jet that periodically collapses and breaks up into hot spatter. Based on the results, we believe that our multiphysics modelling methodology, opens up new pathways for predicting how laser beam shaping influences porosity, surface roughness as well as microstructure formation in LPBF processes.

Intensifying interfacial oscillations in falling film flows over rectangular corrugations

Unsteady film flows play an important role in intensifying heat and mass transfer processes, with applications, e.g., in falling film absorbers or reactors. In this context, the influence of surface structure modification on the wave dynamics of falling film flows is experimentally investigated based on localized film thickness time series data. Arrays of rectangular ridges oriented perpendicular to the main flow direction are considered, and an optimum ridge distance is identified, at which particularly strong interfacial oscillations are induced in the falling film. These potentially result from the interaction of the flow with a statically deformed base film under resonance-like conditions. The transient destabilization is amplified in the case of narrow ridge sizes, where inertia-driven flow features are particularly pronounced. With regard to mass transfer applications, the structure-induced increase in gas–liquid interfacial area may be of secondary importance compared to changes in internal flow conditions.

Application of computational fluid dynamics in optimizing microalgal photobioreactors

Developing more efficient microalgal photobioreactors (closed cultivation systems) is impelled by increasing interest in microalgal cultivation to produce high-value products. Compared to open cultivation systems closed photobioreactors (PBRs) offer several advantages, including the potential for high productivity in a small footprint, ability to maintain a controlled environment, and their scalability for commercial production. Computational Fluid Dynamics (CFD) provides a powerful tool to simulate flow conditions of microalgal cultivation systems and analyze operational parameters which may affect cultivation key factors such as light (wavelength, intensity, and period of exposure), accessibility to nutrients, and mixing. Besides, geometric modifications employing CFD can accelerate the design process and considerably reduce the need for a thorough, empirical exploration of reactor configurations and the associated costs. This paper provides a comprehensive review of recent updates on the application of CFD in various microalgal cultivation systems with special focus on different geometry optimization of flat plate photobioreactors.This review examines recent studies that have employed various multiphase and turbulence methods within the CFD framework to simulate fluid flow and turbulence within reactors, aiming to improve flow characteristics and enhance microalgal productivity. Specifically, the application of CFD in optimizing flat plate photobioreactors is explored, with researchers investigating a range of baffles and sparger configurations to enhance microalgal productivity. Additionally, the advantages of adopting CFD are discussed, and the potential future applications of CFD in microalgal cultivation are outlined.

Season-dependent climate sensitivity of the surface runoff of major rivers in Changbai Mountain

Due to the sensitivity of runoff to changes in seasonal snowpack, the changes in surface runoff within high-latitude and high-elevation areas are more complex than in other areas. However, this sensitivity is often overlooked when correlating changes in runoff with meteorological variables. Here, we analyze changes in surface runoff during snowmelt and snowless periods and their sensitivity to climate change from 1960 to 2019 in the upstream watersheds of the Songhua, Yalu, and Tumen Rivers in Changbai Mountain. Most runoff indices, except for low flow in the Yalu River, exhibited decreasing trends during snowmelt and snowless periods. Precipitation was the primary variable responsible for surface runoff during snowless and snowmelt periods. Notably, rainfall replenished all runoff indices during snowless periods, particularly under high flow conditions. The average and high flows were also primarily supplemented by rainfall during snowmelt periods. However, low flow was positively correlated with snowmelt in the Songhua and Tumen Rivers and with temperature in the Songhua, Yalu and Tumen Rivers during snowmelt periods. Additionally, extreme runoff events were closely associated with extreme precipitation. These findings demonstrate the seasonal and index-dependent climate sensitivity of surface runoff within Changbai Mountain, offering insights into the surface runoff response mechanism to climate change in high-altitude mountainous areas. Under future climate change conditions, frequent and intense extreme precipitation events may increase the risk of flooding, owing to the high sensitivity of high flows to precipitation, posing a serious threat to regional ecological security.

Theoretical predictions to facilitate the method development in slalom chromatography for the separation of large DNA molecules

Slalom chromatography (SC) re-emerged in 2024 due to the availability of low adsorption ultra-high pressure liquid chromatography (UHPLC) packed columns/instruments and large modalities being investigated in the context of cell and gene therapies. The physico-chemical principles of SC retention combined with hydrodynamic chromatography (HDC) exclusion have been recently reported. In SC, DNA macromolecules are retarded because: (1) they can be stretched to lengths comparable to the particle diameter, and (2) their elastic relaxation time is long enough to maintain them in non-equilibrium extended conformations under regular UHPLC shear flow conditions. Here, a quantitative HDC-SC retention model is consolidated. A general plate height model accounting for the band broadening of long DNA biopolymers along packed beds is also derived for supporting method development and predicting speed-resolution performance in SC.For illustration, the chromatographic speed-resolution properties in SC are predicted for the separation of specific critical pairs (4.0/4.5, 10/11, and 25/27 kbp) of linear dsDNA polymers. The calculations are performed for two available custom-made particle sizes, dp= 1.7 and 2.5μm, at a constant pressure of 10,000 psi. The predictions are directly validated from experimental data acquired using low adsorption MaxPeakTM 4.6 mm i.d. Columns packed with 1.7μm BEHTM 45 Å (15 cm long column) and 2.5μm BEH 125 Å (30 cm long column) Particles, and by injecting six linear dsDNAs (λ DNA-Hind III Digest). The LC system is very low dispersion ACQUITYTM UPLCTM I-class PLUS System, and the mobile phase is a 100 mM phosphate buffer at pH 8. Maximum resolution is always achieved when the average extended lengths of linear dsDNAs are equal to a critical length, which is proportional to the particle diameter and to the square root of the applied shear rate. Most advantageously, the experimental results reveal that the relaxation times of linear dsDNAs observed under shear flow conditions are two orders of magnitude shorter than those expected in the absence of flow: this enables the detection of the longest linear dsDNAs up to 25 kbp without irremediable loss in column performance. Finally, the retention-efficiency model elaborated in this work can be used to rapidly anticipate and develop methods (selection of particle size, column length, and operating pressure) for any targeted DNA and time-resolution constraints.

Computational investigation of both geometric and fluidic compressible turbulent thrust vectoring, using a Coanda based nozzle

This study addresses the challenge of enhancing aircraft maneuverability, particularly for vertical landing and takeoff, focusing on the fluidic aerial Coanda high efficiency orienting jet nozzle that employs the Coanda effect to achieve thrust vectoring. This research advances understanding of the interplay between geometric and fluidic factors in thrust vectoring. Stationary, turbulent, and compressible flow conditions are assumed, employing Favre-averaged Reynolds-averaged Navier–Stokes approach with the standard k-ε model. Computational solutions were obtained using a pressure-based finite volume method and a structured computational grid. The key findings include thrust vectoring enhancement due to an increase in the total mass flow rate, septum position (at no shock wave-related issues), and Reynolds number. In addition, shock wave formation (at specific mass flow rates and septum positions) considerably affects thrust vectoring. These insights are crucial for optimizing Coanda-based nozzle design in advanced propulsion systems, including in unmanned aircraft vehicles.

Prediction model for self-starting of hypersonic inlets with soft critical unstart mode

The acceleration self-starting performance of hypersonic inlets is of critical importance for the stable operation of scramjet engines. The occurrence of soft unstart during the transition from hard unstart to start is an important flow state that has yet to be fully elucidated. The stability mechanism and corresponding self-starting characteristics of soft unstart remain poorly understood, and there is a pressing need for detailed modeling research in this area. This paper presents a rapid prediction model for the self-starting Mach number of two-dimensional hypersonic inlets with soft critical unstart mode, fully considering the influence of various geometric parameters and Reynolds number in the internal contraction section, and achieving a quantitative analysis of the two-dimensional soft unstart critical flow field. Given the incoming flow conditions and the inlet geometry, the prediction model is capable of accurately representing the actual viscous unstart flow field. It can fully map the unstart separation bubble and its surrounding critical wave structures, and calculate the minimum pressure rise required to maintain the current scale of the main separation bubble and the pressure rise exerted on the unstart separation bubble by the current actual flow field structure. Comparing the relative magnitude of these two pressures determines whether the inlet can transition from soft unstart to start. The proposed prediction model was validated using results from unsteady numerical simulations. The predicted results align well with the simulation results and are significantly better than previous prediction methods.

Investigations on thermal profiles and flow structures in a square channel equipped with staggered vortex turbulators

Given the escalating energy demands today, improving the efficiency of engineering equipment is crucial for optimizing energy use. This study focuses on enhancing heat exchanger performance through passive methods, particularly by installing vortex turbulators. Passive techniques can effectively manage energy costs while enhancing efficiency.The research examines thermal profiles and airflow structures within a square channel heat exchanger (SCHE) equipped with staggered vortex turbulators (SVTs). SVTs feature a unique design combining rectangular winglets and V-pattern baffles. The installation of SVTs aims to intensify vortex strength, thereby increasing SCHE efficiency, convective heat transfer coefficients, and overall heat transfer potential. The study investigates the effects of SVT dimensions (b1/H and b2/H), airflow directions (+x and -x), installation patterns (pattern no. 1 and 2), pitch to height ratios (P/H = 1, 1.5, and 2), and flow attack angles (α = 20°, 30°, and 45°). Computational simulations using the finite volume method with a commercial code (FLUENT) under laminar flow conditions (Reynolds number of 100–2000) provide insights into thermal profiles, fluid temperature distributions, and flow configurations within the SCHE. Staggered arrangement and gap spacing are employed to reduce pressure loss and enhance airflow strength. The results highlight flow structures and heat transfer characteristics in the heat exchanger channels, elucidating the underlying mechanisms of the heat exchange process. Understanding these behaviors is crucial for developing more efficient heat exchangers and vortex generators in the future. Simulation findings demonstrate that SVTs significantly enhance convective heat transfer over smooth channels due to increased vortex strength. Notably, pattern no. 2 SVTs (b1/H = b2/H = 0.20) achieve the highest Nu/Nu0 of 19.21 in the +x flow direction at Re = 2000, α = 30°, and P/H = 1. In conclusion, the study identifies a maximum thermal enhancement factor of 4.38. It underscores the potential of pattern no. 2 SVTs for optimizing heat exchanger performance, offering valuable insights for future developments in thermal management technologies.

On the enhancement of acceptable blockage of open jet wind tunnel by employing modifications based on concepts of boundary layer and jet flow for testing of aero-rotors

The conventional closed and open jet tunnels suffer from various adverse blockage effects that alter the flow conditions generating erroneous results when larger than allowable blockage models are tested. The maximum acceptable blockage is limited to 25% for an open jet tunnel. The physics behind the inferior blockage capacity and their redressal is investigated. Hitherto, numerical models are developed to rectify the blockage troubles that introduce an additional complex case-based mathematical modeling to reckoning the results. In the current paper novel approach to redesigning the tunnel to solve blockage troubles is investigated that facilitates evading of mathematical techniques and securing accurate results straightforwardly. A hypothetical design incorporating the remedies is proposed, capable of conditioning the flow in a manner that debilitates the adverse effects of solid blockage, wake blockage, jet expansion, etc. The hypothesis is theoretically expounded by the boundary layer and jet flow phenomenon. The modified blower-type open jet wind tunnel constitutes a centrifugal blower, long inlet duct, plenum chamber around the test section, and collector. The modified wind tunnel is tested through experiments executed on four different-sized Savonius rotors creating 10%, 30%, 50%, and 60% blockage. The static pressure along the contours of the blades of rotors is obtained. The experimental results are juxtaposed with CFD results carried out at free-wind boundary conditions and standard classic experimental results performed in conventional wind tunnel at 11% blockage. A blockage enhancement of 25% is achieved by the approach of modification in the design of a conventional open jet wind tunnel.

Numerical prediction of passive speed and performance for multistage pump without power drive in natural flow process

With the development of engineering applications and the increase in system complexity, some particular fields, such as liquid rocket engine turbopumps, aircraft engine fuel systems, and marine natural flow cooling systems, are increasingly focusing on the performance characteristics of pumps under natural flow conditions. The pump is in the form of resistance components under natural flow conditions without a power drive. The impeller undergoes passive rotation by the impact of inlet flow. Due to the specificity of its operating conditions and performance indicators, the pump's natural flow performance cannot be evaluated by regular methods. Therefore, this paper proposed a numerical prediction method for pump natural flow performance based on a coupled computational fluid dynamics coupled with six-degrees-of freedom model. The performance of a multistage pump with guide vanes was evaluated under different natural flow conditions, and the accuracy was verified by experimental measurements. The transient variation mode of pump performance parameters with time at the initial stage of natural flow impact was analyzed. The flow field's transient evolution characteristics and the wall shear stress variation during natural flow were investigated. It was found that the impeller's passive rotational speed increases linearly with the natural flow rate, while the hydraulic loss shows an exponentially increasing trend. Meanwhile, the natural flow loss coefficient shows an exponentially decreasing trend and gradually tends to a stable value. The high turbulent kinetic energy inside the impeller is mainly distributed in the flow separation region and large velocity gradients. The distribution of shear stresses is closely related to the flow behavior inside the pump and the geometrical features of the hydraulic components.

In Silico Approach to Model Heat Distribution of Magnetic Hyperthermia in the Tumoral and Healthy Vascular Network Using Tumor-on-a-Chip to Evaluate Effective Therapy

Glioblastoma multiforme (GBM) is the most severe form of brain cancer in adults, characterized by its complex vascular network that contributes to resistance to conventional therapies. Thermal therapies, such as magnetic hyperthermia (MHT), emerge as promising alternatives, using heat to selectively target tumor cells while minimizing damage to healthy tissues. The organ-on-a-chip can replicate this complex vascular network of GBM, allowing for detailed investigations of heat dissipation in MHT, while computational simulations refine treatment parameters. In this in silico study, tumor-on-a-chip models were used to optimize MHT therapy by comparing heat dissipation in normal and abnormal vascular networks, considering geometries, flow rates, and concentrations of magnetic nanoparticles (MNPs). In the high vascular complexity model, the maximum velocity was 19 times lower than in the normal vasculature model and 4 times lower than in the low-complexity tumor model, highlighting the influence of vascular complexity on velocity and temperature distribution. The MHT simulation showed greater heat intensity in the central region, with a flow rate of 1 µL/min and 0.5 mg/mL of MNPs being the best conditions to achieve the therapeutic temperature. The complex vasculature model had the lowest heat dissipation, reaching 44.15 °C, compared to 42.01 °C in the low-complexity model and 37.80 °C in the normal model. These results show that greater vascular complexity improves heat retention, making it essential to consider this heterogeneity to optimize MHT treatment. Therefore, for an efficient MHT process, it is necessary to simulate ideal blood flow and MNP conditions to ensure heat retention at the tumor site, considering its irregular vascularization and heat dissipation for effective destruction.

Deposition of aerosol particles and characteristics of turbulent flow inside wavy pipe using Eulerian-Lagrangian approach

This paper demonstrates a numerical simulation study to understand particle deposition phenomena in wavy pipe configurations comprehensively. The research investigates the intricate dynamics of particle deposition within wavy pipes by utilizing the RNG k-ε turbulence model with enhanced wall treatment for fluid flow simulation and employing a Lagrangian particle tracking model. The finite volume approach is adopted to solve the mathematical model of the current problem. The rate of aerosol particle deposition within a wavy pipe under turbulent flow conditions is systematically explored by varying the size of particles (1 ≤ dp (μm) ≤ 30), Reynolds numbers (5000 ≤ Re ≤ 10,000), and other parameters like wave frequency (3 ≤ f ≤ 7), wave amplitude (5 ≤ a (mm) ≤ 15), and diameter of the pipe (10 ≤ D (mm) ≤ 30). The findings reveal significant correlations between these parameters and deposition efficiency, shedding light on the complex interplay between geometric factors and flow characteristics within the wavy pipe configurations. Notably, larger pipe diameters and higher wave amplitudes are found to enhance deposition rates, while the optimal wave frequencies exist at intermediate values. Additionally, alterations in flow velocity exhibit an inverse relationship with deposition efficiency.