Influence Mechanism Research Articles

Spatiotemporal evolution and influencing factors of flood resilience in Beibu Gulf Urban Agglomeration

In the context of global climate change and rapid urbanization, enhancing flood resilience is essential for mitigating urban flood risk. However, few studies have conducted long-term, cross-scale dynamic evaluations of flood resilience and analyzed its influencing factors and mechanisms. Taking the Beibu Gulf urban agglomeration as the study area, a long-term, cross-scale dynamic evaluation index system based on the “Robustness-Resistance-Recovery” (3Rs) framework were adopted to assess the spatiotemporal evolution of flood resilience from 2000 to 2020. Furthermore, the optimal parameters-based geographical detector model is employed to identify the key influencing factors and mechanisms. The results reveal that pre-flood robustness is lower in coastal areas and higher in inland regions. In the during-flood stage, cities with greater comprehensive power exhibit stronger resistance. Post-flood recovery is higher in city centers and marginal mountainous areas, while coastal and inland low-lying regions show lower recovery. The flood resilience of urban agglomerations has improved in recent years, largely due to the enhancement of urban flood control infrastructure and healthcare capacity. However, disparities between cities persist. From 2000 to 2020, economic factors have been the primary drivers of improved flood resilience, while ecological factors have gained increasing importance over the past decade. These findings provide valuable insights for flood prevention, mitigation, and resilience management in urban agglomerations. The proposed dynamic evaluation index system offers a reference framework for evaluating flood resilience in other regions.

Parental norms and attitudes in Relation to Children’s sugar consumption − A mediation analysis of the “Are You Too Sweet?” intervention study

Parental influence on children’s dietary behaviour makes parents an obvious target for prevention strategies with nutritional foci. Mediation analysis is considered a valuable tool for understanding the underlying mechanisms of influence in intervention studies aimed at implementing behaviour change strategies.The present study used data from the multi-component cluster-randomised intervention “Are You Too Sweet?” with 153 Danish children (5–7 years) to explore mediating effects and role of parental determinants on added sugar intake in children.A pre-and post-intervention questionnaire evaluated parental knowledge, practices, self-efficacy, norms, and attitudes. Children’s dietary intake was estimated from a seven-day dietary record. Associations between children’s added sugar intake and parental responses and changes in responses following the intervention were evaluated using linear mixed models. Exploring potential behaviour change pathways of the intervention was done using mediation analyses.Children’s reduction in added sugar consumption was partly mediated by changes in parental norms and attitudes regarding limiting sugar-rich foods and drinks to special occasions. Parental knowledge of guidelines on the intake of sugar-rich discretionary foods and drinks increased as an intervention effect but did not demonstrate a mediating effect. No significant changes or mediating effects were found in parental self-efficacy or practices.The findings highlight parental norms and attitudes regarding restricting sugar-rich foods and drinks to special occasions as modifiable and a mediator for reducing added sugar intake in the “Are You Too Sweet?” intervention study.Trial registration: Retrospectively registered at ISRCTN: ISRCTN10409779.

Role of Apolipoprotein E in Alzheimer's Disease Pathogenesis, Prognosis and Treatment.

Alzheimer's disease (AD) is an incurable and progressive neurodegenerative disease with increasing prevalence worldwide. Previous trials of anti-amyloid and anti-tau immunotherapy indicate that additional research needs to be conducted on other mechanisms to find curative or disease-modifying therapy. This review focuses on apolipoprotein E (ApoE), a critical protein in brain lipid metabolism that acts specifically in the clearance and transport of lipids and cholesterol. The ApoE4 allele confers substantial gene dose-dependent risk of developing AD and lowers the age of onset of AD, although the mechanisms of influence remain incompletely understood. The other isoforms bring different levels of AD risk. ApoE2 is protective while ApoE3 is the most common isoform and is considered neutral. An overview is presented of the latest information on the role of ApoE in AD pathogenesis with an emphasis on pathways that are involved in AD development and interactions with crucial processes in different cell types in the brain. Elucidating the key interactions of ApoE with multiple aspects of brain function can be useful for designing novel ApoE-targeted therapeutic approaches.

New insights into biofouling worsening induced by salinity stress in membrane bioreactor: Response of quorum sensing system and its regulation role

Severe worsening of biofouling under salinity stress remains one of the biggest hinderances to membrane bioreactor (MBR) treating saline wastewaters and other membrane technologies applied in saline conditions e.g. seawater desalination. The underlying influential mechanism of salinity stress on biofouling was firstly investigated from the perspective of quorum sensing (QS); Response of QS to salinity stress and its role in regulating biofouling behavior were clarified. Results showed that high salinity stress (over 20 g/L of NaCl) greatly stimulated QS activity, acyl-homoserine lactones (AHLs) were increased by over 200 % and 300 % in mixed liquor and cake layer, respectively; C4-OXO-HSL, C8-OXO-HSL, C10-OXO-HSL and C12-OXO-HSL became the dominant AHLs and showed strong correlations (R2＞0.95) with changes of fouling tendency and extracellular polymeric substances (EPS) characteristics. Metagenomic sequencing further revealed that balance between QS and quorum quenching (QQ) was broken when salinity was over 20 g/L; QS related bacteria and genes were significantly enriched, meanwhile QQ related bacteria and genes were radically suppressed. QS enhancing (by exogenous AHLs) and suppressing experiments (by vanillin) collectively verified the critical regulation role that QS played in biofouling worsening under high salinity stress (mainly via altering EPS characteristics); More importantly, it was demonstrated that suppressing the highly activated QS under high salinity stress was a feasible way to curb the worsening of biofouling. Present study provided new insights into biofouling worsening induced by high salinity stress in MBR; Also, the findings could help to understand biofouling phenomenon in other membrane processes facing salinity stress.

Influence mechanism of the principal stress axis rotation effect on the propagation of blast-induced cracks under in-situ stress

In-situ stress plays a pivotal role in controlling both the propagation speed and trajectory of blast-induced cracks. Previous studies have primarily placed emphasis on the qualitative analysis of the propagation morphology of such cracks, but the principal stress axis rotation effect under static-dynamic coupling loading was ignored. Consequently, the mechanical mechanism of the propagation of blast-induced cracks has not been figured out yet. In this study, a combination of laboratory tests, theoretical analysis, and numerical simulations was employed to explore the influence mechanism of the principal stress axis rotation effect on the propagation of blast-induced cracks under in-situ stress. The results suggest that the hydrostatic pressure does not change the propagation trajectory of blast-induced cracks, but a higher hydrostatic pressure will inhibit both their propagation speed and length. In contrast, the deviatoric stress can change the propagation trajectory of blast-induced cracks, and a higher deviatoric stress makes it easier for blast-induced cracks to deflect to the maximum loading stress direction. Besides, the propagation of blast-induced cracks exhibits different features in different stages under in-situ stress. In the zone near the blast source, the dynamic stress is dominant; the maximum principal stress of the mass points is distributed in the radial direction; and blast-induced cracks expand mainly along the radial direction. On the contrary, in the zone far from the blast source, the static load is dominant; the maximum stress direction of the mass point alters to the maximum loading stress direction; and blast-induced cracks deflect from the radial direction to the maximum loading stress direction. Therefore, the propagation of blast-induced cracks under in-situ stress is a dynamic process in which dynamic and static stresses compete for crack initiation, and the changes in both stress value and principal stress direction are identified as the main reasons for the deflection of blast-induced cracks.

Energy-Preserving Perturbation Method for Thermally Induced Dynamics in Aerospace Tensegrity Structures

Tensegrity structures are emerging as pivotal components in the assembly of ultralarge modular spacecraft in orbit, primarily due to their exceptional volume-to-mass ratio and robust controllability. During on-orbit operations, given the low damping and high flexibility of tensegrity, its vibration-induced deformations affect the magnitude of the heat flux, presenting a typical force–shape coupling problem. This paper introduces an energy-preserving matrix perturbation solution designed to efficiently and accurately address the thermally induced vibration challenges in tensegrity. This method effectively mitigates the energy dissipation and numerical instability issues. Furthermore, the analysis incorporates the impact of the axial component of heat flux on structural vibration, uncovering the influence mechanism of this often-overlooked slow variable on the dynamic behavior of tensegrity. The proposed method demonstrates a deviation of less than 1% between the thermal response and the results obtained from finite element analysis, while achieving a 70% reduction in computation time. The varying axial thermal load leads to a rapid decrease in system frequency, resulting in divergent thermal vibrations. Additionally, the significant dynamic stress can potentially surpass the structural stress limits. These findings underscore the critical importance of considering such effects in the design and calculation of tensegrity structures for aerospace applications.

Unveiling the dynamic flows and spatial inequalities arising from agricultural methane and nitrous oxide emissions

Tracing the spatial transfer and heterogeneity of agricultural methane (CH4) and nitrous oxide (N2O) emissions in China is a prerequisite for the sustainable transformation of agricultural systems. In this study, we established a research framework for evaluating agricultural CH4 and N2O flows and convergence. Using this framework, we established an inventory of China's agricultural CH4 and N2O emissions calculated according to the IPCC inventory guidelines, built a food trade model to simulate the spatial transfer, and revealed the regional differences. Finally, we analyzed the influence mechanism by combining extended Kaya identity and the logarithmic mean divisia index (LMDI) model. We found that inter-regional transfer of agricultural CH4 and N2O emissions in China have intensified, increasing from 56.14 % of total transfers in 2000 to 67.28 % in 2019. The spatial inequalities of agricultural CH4 and N2O increased, and emission intensity varied more within regions than between regions, with per capita emissions showing a club convergence with “intragroup convergence and intergroup divergence”. Although the contribution of agricultural CH4 and N2O emissions varies across provinces, controlling emissions intensity and land use intensity while maintaining GDP per capita is the key to emission mitigation. Our study provides theoretical support for prioritizing policies to mitigate agricultural CH4 and N2O emissions.

Quantitative Assessment of Sand Particulates in Gas-Water Slug Flow Using Deep Learning

Summary The weak collision response excited by micrometer-scale sand particulates is prone to overmixing with strong slug noise, significantly reducing the characterization and monitoring accuracy of sand particulate information in slug flows. Therefore, we developed a quantitative assessment method for sand particulates in slug flow that combines triaxial vibration monitoring and deep learning. First, a migration behavior characterization method of sand particulates is proposed combining nonlinear statistics, multifrequency coherence, and multiscale time frequency. The multifrequency response characteristics corresponding to the multiscale flow behavior of the sand-carrying slug flow were successfully characterized on the 2D time-frequency plane, namely, the mixed sand migration behavior [Intrinsic Mode Function 1 (IMF1)], liquid slug sand carrying (IMF2), forward liquid film and Taylor bubble sand carrying (IMF3), and reflux liquid film sand carrying (IMF4). Furthermore, the influence mechanism of gas superficial velocity (1.5–3.5 m/s), liquid superficial velocity (0.95–2.14 m/s), and sand content (0–20 g) on the triaxial vibration response of slug particulate flow with different migration behaviors is elucidated. Finally, a convolutional neural network (CNN)-gated recurrent unit (GRU)-self-attention mechanism (SATT) model for sand content assessment is developed based on the characterized multiscale migration behavior information and achieves an average recognition accuracy of 95.55% for data sets representing different sand migration behaviors in slug flow. This provides a new method for precisely identifying and monitoring sand production information of multiphase pipe flow.

Investigating the influence mechanism of aluminum doping amount on the density and grain size of AZO target through phase-field simulation

This study proposes a three-phase model (primary, secondary, and pore phases) utilizing the phase-field method to simulate sintering densification in AZO targets. The impact of secondary phase content and dimensions on the densification of AZO targets was investigated. The findings indicated that the density of the AZO target exhibited an initial increase followed by a subsequent decline with the augmentation of the secondary phase content and size. Conversely, the grain size demonstrated a continuous reduction. The Brook kinetic equation yields activation energies for grain growth of 607.40kJ/mol, 999.32kJ/mol, and 1093.20kJ/mol for 1wt%, 2wt%, and 3wt% Al2O3, respectively. Furthermore, the viability of the model was corroborated through experimentation. Based on the simulation outcomes, AZO targets doped with 2wt% Al₂O₃ achieved 99.78% densification, an average grain size of 3.92 μm, and a resistivity of 1.38 mΩ·cm.

A multi-stage game framework for new route promotion: Behavioral strategy and dynamic evolution of shippers, carriers, and governments

New freight routes are being planned and emerging globally, but often rely on government subsidies to enhance their competitiveness during the initial promotional phase. This study proposes a multi-stage game framework to explore the influence mechanism of behavioral strategies among three stakeholders: shipper, carrier, and government. Based on the assessment of shippers’ route choice preferences, we examine the dynamic evolution of carriers’ and governments’ behavioral strategies in the practical context of bounded rationality and dynamic learning. We theoretically derive the evolutionary paths and stable outcomes of dynamic systems across eight scenarios encompassing all the possible practical values to be taken, which provide broader and more valuable decision support for new route promotion. Finally, the feasibility and validity of the proposed model are verified by the actual case of the New International Land-Sea Trade Corridor. The findings indicate that government subsidies are not always effective and provide a precise subsidy range that can incentivize carriers to switch to the new route. Moreover, the study clarifies the impact of key factors such as subsidy, tax, route reliability, transportation time, and time value of cargo on the promotion of new routes through numerical simulation, and provides feasible management recommendations for government and route operations.

Coupled computational fluid dynamics-discrete element method for simulating the interactions between ship-induced waves and riprap on restricted waterway banks

In inland waterways, waves generated by passing boats cause the movement of riprap used for bank protection and stabilization. Previous studies have mainly concerned the natural channel erosion problem caused by wind-generated waves and neglected the research and findings on shipping behavior. This work presents a coupling of the computational fluid dynamics model and the discrete element method. The aim is to first study the interactions between ship waves in the confined channel and the movements of the riprap of the banks and shorelines and second to analyze the stability of these armourstones under the actions of various ship velocities and draught depths. These varying conditions exert influence on the ship-induced waves, the crucial point being the drawdown amplitude, and consequently create more intense flow behavior in the near-shore region, which results in instability and destruction of the overall structure of the armor protection layer. The higher ship velocity and the larger draught depth lead to the aggravation of instability processes of the blocs composing the protective layer. There is a critical phenomenon in the influence mechanism of vessel velocity, whereas the variation process induced by draught depth is relatively linear. In addition, the stability of the blocs also depends on their shapes, sizes, and the initial positions within the protective layer. This study could contribute to the high-quality development of inland navigation.

Orthogonal experimental investigation on permeability evolution of unconsolidated sandstones during geothermal fluid reinjection: a case study in the Minghuazhen Formation, Tianjin, China

Geothermal fluid reinjection (GFR) is vital for sustainable sandstone hydrothermal geothermal resource extraction. However, the permeability damage mechanisms of sandstone geothermal reservoirs due to reinjection remain unclear. This study aimed to investigate the permeability evolution of unconsolidated sandstone during GFR through an orthogonal experiment. The influence mechanism of the factors, including temperature, injection rate, confining pressure, geothermal fluid concentration (GFC), and depth, on sandstone permeability is also discussed. The results showed the sandstone samples suffered permeability damage in 34.62∼72.73%. Particle clogging emerged as the primary mechanism responsible for the permeability damage, serving as a crucial bridge in understanding the influences of the factors on sandstone permeability. Efficient GFR requires the optimization of reinjection conditions tailored to the characteristics of geothermal reservoirs. Sensitivity analysis showed that the order-sensitive characteristic of permeability damage to the factors was injection rate > GFC > temperature > depth > confining pressure. Through the optimization of reinjection parameters, the heat exploitation performance under the worst permeability damage case can be improved by 1.77∼1.93 times. This study could offer valuable insights into the challenges and considerations associated with GFR in sandstone reservoirs.

Experimental study on the effect of CO2 desublimation on heat transfer

Revealing the influence mechanism of CO2 desublimation on heat transfer is crucial for developing new liquefied natural gas heat exchangers. In this paper, an experimental platform for CO2 desublimation was built to investigate and analyze the intrinsic connection between CO2 desublimation and heat transfer, and systematically elaborated the mechanism of the influence of CO2 desublimation on heat transfer under different operating conditions based on the values of the heat transfer coefficient and CO2 thermal resistance. The results of the study show that CO2 can rapidly start condensation on the cooling surface when the gas flow rate is too fast (60 kg/h), which leads to a weakening and then strengthening of the effect of CO2 condensation on the heat transfer as the gas flow rate increases. In addition, as the cooling temperature drops, the amount of heat exchange between CO2 and the refrigerant decreases, and the magnitude of the changes in the values of the heat exchange coefficient and CO2 thermal resistance increases, with the value of the heat exchange coefficient decreasing by up to 39.9 %. Compared with the gas flow rate, the cooling temperature was the main factor affecting CO2 desublimation, and it has a more significant effect on heat transfer. This experimental study provides a theoretical basis for the design of a new type of liquefied natural gas heat exchanger and provides valuable insights into the mechanism of CO2 desublimation.

Insight into the effect of Gd-doping on conductance and thermal matching of CeO2 for solid oxide fuel cell

GDC (Gd-doped CeO2) play a dual role in solid oxide fuel cell (SOFC), effectively blocking the reaction between YSZ (Y2O3-doped ZrO2) electrolyte and high-performance cathode materials such as La0.6Sr0.4Co0.2Fe0.8O3-δ, and improving the low-temperature oxygen ion transport in composite cathodes. It is crucial to systematically investigate the influencing mechanism of Gd-doping on conductance and thermal matching of CeO2 for high-efficiency and stable SOFC. In this paper, the physical phase, morphology and electrochemical performance of Ce1-xGdxO2-δ (x=0.1, 0.15, 0.2, 0.25) were characterized, and the thermal matching between GDC and other cell components was investigated by finite-element thermal stress calculations and cold-heat-cycling tests. The results indicate that Ce0.8Gd0.2O2-δ obtains the optimum conductivity, whether in the low temperature segment affected by the grain boundary with the space charge layer, or in the activation energy controlled medium temperature segment. Moreover, the finite-element calculation shows that the thermal stresses of the electrolyte facing the barrier layer and the barrier layer facing the cathode decrease gradually with the increase of Gd-doping. Consequently, the cell with Ce0.8Gd0.2O2-δ applied to the composite cathode and the barrier layer presents the optimal output performance of 0.87 W⋅cm-2 at 750 °C, and the cell performance decreased by only 1.15% after 50 thermal cycles between 25-800 °C. This is significant for improving the long-term operational stability of SOFC under thermal cycling conditions.

Catalytic modification of MgH2 hydrogen storage properties by La–Ni catalysts

In this paper, it is experimentally demonstrated that the La–Ni catalyst contributes to the hydrogen storage performance of MgH2. Firstly, La–Ni (La: Ni = 1: 5.7) catalysts are prepared by CaH2 reduction method, and then MgH2+x wt.% La–Ni (x = 0, 3, 5, 7) composite alloys were prepared by ball milling method. The present work focuses on the structural and hydrogen ab/desorption properties of the composite alloys, and analysis the modulatory effect and influence mechanism of different La–Ni catalyst additions on the hydrogen storage properties of MgH2. The findings show that the composite alloys have the same diffraction peaks and that the main phase of the composite alloys is the MgH2 phase, with the addition of the LaNi5 phase, the Mg2Ni phase and a small amount of Mg phase. The mutual reversible transformations of LaH3 and Mg2Ni and Mg2NiH4 play a catalytic role in the hydrogen ab/desorption process. Moreover, the addition of La–Ni catalyst plays a dramatic improvement effect on the kinetic performance of MgH2 ab/desorption. When the addition of La–Ni catalyst is 5 wt.%, the composite alloy exhibits the most excellent hydrogen uptake and release kinetics. The MgH2+5 wt.% La–Ni composite alloy absorbs 4.2 wt.% H2 within 2 min at 473 K and releases 3.43 wt.% H2 within 150 min at 503 K. Fitting the hydrogen release activation energy of the composite alloys shows that the hydrogen release activation energy of the composite alloys decreases first and then increases, and there is a minimum hydrogen release activation energy of 101.81 kJ/mol H2 when the addition amount x = 5 wt.%.

Influence of in-situ lunar temperature on the pore structure and solid phases of alkali-activated lunar regolith simulant

The construction of extraterrestrial bases has become an indispensable step in the active exploration of deep space. In this study, alkali-activated lunar regolith simulant (AALRS) activated by sodium hydroxide (SH) and sodium silicate (SS) were prepared and then cured at various lunar temperatures. The compressive strength was tested, and the pore structure characteristics were characterized using mercury intrusion porosimetry (MIP), followed by further in-depth quantitative analysis through fractal theory. The solid phases were characterized using thermogravimetry analysis (TGA) and scanning electron microscopy (SEM). It is found that all the fractal curves are divided into three regions, and the fractal dimensions in all regions are between 2 and 3, suggesting the pores of AALRS paste always have self-similar physical significance. The fractal dimension D1 of the small pore is the largest, followed by fractal dimension D3 of the great pore and fractal dimension D2 of the middle pore. The increase in modulus and temperature leads to an increase in the pore surface area, fractal dimension, amount of N-A-S-H gel and compressive strength and a decrease in total pore volume and characteristic pore diameter, which is mainly attributed to the nucleation effect of soluble Si. The turning pore diameter at the micrometer scale and excessive porosity of AALRS paste, which is distinctly different from that of common cementitious materials, demonstrates looser pore structure of AALRS paste. Based on these results, the influence mechanism of in-situ lunar temperature on the performance of AALRS paste is profoundly discussed and elucidated, which provides a deep understanding of designing and tailoring the various properties of AALRS material.

Characteristic analysis and diagnosis method optimization of scroll compressor pressure pulsation signal under voltage fluctuation

Under off-design conditions, scroll compressors can lead to reduced efficiency, motor damage, and even cause safety problems such as leaks or explosions. To solve the above problems, this paper analyzes the influence mechanism of different voltages on the spectrum of pressure pulsation signal and modulation signal and provides theoretical support for fault diagnosis and enhances the interpretability of the model. A voltage fault diagnosis method of scroll compressor based on Time-frequency Principal component Convolutional Network (TPCN) model is proposed. By demodulation analysis of the pressure pulsation signal of the low-pressure inlet and high-pressure outlet of the refrigerant in the scroll compressor, the spectrum information of the principal component modulation signal under different voltages is obtained. The pooling strategy is used to accurately identify and extract the fault information in the modulated signal spectrum as the input data of the model. The input data is divided into the training set and the test set according to the ratio of 8:2 to complete the training and testing of the fault diagnosis model. The experimental results show that the accuracy of TPCN model for the diagnosis of 5 types of faults reaches 100 %. The average accuracy of the model is 100 %, which indicates that the model has good stability.

Laboratory-scale simulation study of pyrolysis process in a fixed-bed gasifier for municipal solid waste pellets: Effects of temperature distribution and residence time

In this study, stepwise heating pyrolysis was designed to simulate the pyrolysis process of municipal solid waste (MSW) pellet in an updraft fixed bed gasifier at a laboratory scale. Differences in pyrolysis product between fixed bed stepwise heating pyrolysis (FBS, ranging from 300 °C to 800 °C) and continuous heating pyrolysis (FBC, maintained at 800 °C) were revealed. The impact of residence time at various temperature ranges on MSW pyrolysis was also investigated. Results indicated that compared to FBC, the gas yield of FBS decreased by 30.74%, while its liquid yield increased by 11.96%. It was primarily due to the lower heating rate reduced the secondary conversion of aliphatic hydrocarbons, oxygenated compounds, and monoaromatic hydrocarbons (MAHs) within liquid products. In addition, the composition of MSW pyrolysis products was changed by adjusting the residence time. Maintaining a uniform residence time of 5min for MSW pellets at each temperature was considered optimal for gas yield, which was mainly attributed to the enhanced cracking of long-chain aliphatic and polycondensation of MAHs and polycyclic aromatic hydrocarbons (PAHs). Besides, the volatiles (C- and O-containing compounds) of the char were almost completely released. The underlying influence mechanism of residence time on the pyrolysis behavior of MSW was also proposed, which could provide insights for the implementation of MSW gasification.

Potential influence mechanism of Mn and Co ions in the process of electrowinning of copper

The presence of impurity ions in the electrolyte during copper electrolysis influences anode performance and cathode quality. Lead anode corrosion causes resource loss and environmental pollution, emphasizing the need to study these impurities. The effects of Co2+ and Mn2+ on Pb-0.06 %Ca-1.2 %Sn anodes and cathode copper are investigated, establishing optimal ion concentrations. Mn2+ facilitates the growth of MnO2 on the PbO2 surface, enhancing corrosion resistance and catalytic activity, especially at a concentration of 2 mg/L. Additionally, the presence of Co2+ leads to the formation of Co3O4 and MnO2, further improving corrosion resistance and promoting oxygen evolution. A pilot experiment with Mn2+ at 2 mg/L and Co2+ at 120 mg/L achieves a current efficiency of 98.4 % and reduces the cell voltage to 1.817 V, successfully meeting energy-saving and efficiency-enhancing objectives.

Two-dimensional boundary layer receptivity to finite periodic disturbances

Receptivity is the focus and frontier of the research on boundary layer transition and flow drag reduction, but the temporal and spatial evolution of Tollmien–Schlichting waves (T-S waves) is not yet fully investigated, limiting the development of highly efficient laminar flow control techniques. In the present study, the local receptivity problem of the laminar boundary layer on a zero-pressure-gradient flat plate is investigated by using the direct numerical simulation, considering both the temporal and spatial evolution characteristics of the T-S waves. External disturbances at fixed frequencies are introduced in the form of velocity pulsations with different periods to excite T-S waves. The temporal and spatial evolution characteristics of the T-S waves excited by different forms and periods of disturbances are studied. It is found that the amplitude, frequency, and wave velocity of the T-S wave induced by the external multi-period disturbances are different from those induced by the constant disturbances. These conclusions are the same as those of T-S wave induced by wall inhalation. After a further investigation on this particular phenomenon, the influence mechanism of external disturbances on the receptivity process is revealed. This new research finding enriches the instability theory and provides a reference for more efficient applications on active laminar flow control technologies.