Transitional Flow Research Articles

Damage index correlation in massive granite-porous backfills under hydromechanical triaxial cyclic loading using acoustic emissions and X-ray computed tomography

The characterization accuracy of damage indices in massive and porous composite biomaterials under complex osmotic conditions has long been a challenge in engineering materials science. Establishing correlations between damage indices calculated using different methodologies is crucial to validate and improve defects characterizations. In this study, we investigated the damage index correlation of cylindrical massive granite-porous backfill structural composites under both dry and seepage conditions. A series of triaxial cyclic loading and unloading tests were conducted on specimens under hydromechanical conditions with varying osmotic pressures (0, 1, 3, 5, 7, and 9 MPa) and a confining pressure of 9 MPa involving acoustic emission monitoring and phase-based 3D nondestructive CT scanning. The results revealed the AE energy was lower under osmotic conditions compared to dry conditions. The AE Damage Index (DAE), defined by separating tensile and shear microcracking signals, significantly increased from 0.32 to 0.55 with rising osmotic pressure. 3D mesoscopic fracture visualization provided detailed insights into the fractures in granite and backfill interfaces. The number of small-angle cracks increased with osmotic pressure, and the crack inclination distribution range expanded from 63°- 85° to 49°–80°. The average crack angle showed a significant monotonic decrease with increasing osmotic pressure. An Energy Dissipation Damage Index (DED) was defined, and its correlation with the DAE under dry conditions was modeled using a reciprocal function DED=a/(DAE+bσ3)+c. This novel approach offers insights into the transition points between tensile and shear-dominated failure stages. Furthermore, an exponential function DV=aDAEb(b<0) was used to model the correlation between AE Damage Index and Visual Damage Index (DV) under osmotic conditions. The damage indices derived from different methods can be mathematically correlated, providing a comprehensive evaluation of material damage states. The study found the flow transition between different natural-human medias results in different damage mechanisms, which are all obey the correlation law. These damage mechanisms offered constructive recommendations for engineering applications based on varying ratios of osmotic pressure to confining pressure.

Plasma-based base flow modification on swept-wing boundary layers: dependence on flow parameters

This work examines the control of cross-flow instabilities (CFIs) and laminar–turbulent transition on a swept wing, through the plasma-based base flow modification (BFM) technique. The effect of experimentally derived plasma body forces on the steady boundary layer base flow is explored through numerical simulations. Linear stability theory is subsequently used to predict the net BFM effect on CFIs. Based on these preliminary predictions, experiments are conducted in a low-turbulence wind tunnel where a spanwise-invariant plasma actuator is installed near the wing leading edge and operated at constant input voltage and frequency. Various flow parameters governing the plasma-based BFM technique are investigated, namely the Reynolds number, angle of attack and wavelength of excited stationary CFI modes. Stationary and travelling CFIs are quantified by planar particle image velocimetry while the transition topology and location are recorded by infrared thermography. The results confirm the stabilising effect of BFM on the swept-wing boundary layer. However, the plasma-based BFM is found to render the boundary layer more susceptible to travelling CFIs. In the presence of both net BFM effect and intrinsic plasma unsteady perturbations, the plasma-based BFM technique achieves transition delay with specific combinations of Reynolds number, angle of attack and wavelength of excited stationary CFI modes. The present findings provide insights into the fundamental principles of operating plasma actuators within the context of BFM control.

A Reformulation of the Laminar Kinetic Energy Model to Enable Multi-mode Transition Predictions

AbstractThe paper describes the development of a novel transition/turbulence model based on the laminar kinetic energy concept. The model is intended as a base framework for data-driven improvements. Starting from a previously developed framework, mainly aimed at separated-flow transition predictions, suitable terms for model generalization are identified and reformulated for handling different transition modes, namely bypass and separated-flow modes. The ideology for the definition of new terms has its roots in mixing phenomenological and correlation-based arguments, ensuring generality and flexibility and allowing a variety of lines of action for improving model components via machine-learning approaches. The model calibration, carried out with reference to flat plate test cases subjected to different pressure gradients and freestream turbulence levels, is discussed in detail. Although the constructed model is calibrated on a group of classic flat plat cases, the validation campaign, mostly carried out on gas turbine cascades, demonstrates its ability to predict transitional flows with engineering accuracy. Finally, while the model is not specifically developed for natural transition predictions, satisfactory predictions are obtained in scenarios with low freestream turbulence for flat plate and airfoil flows.

Shearing Liquids of Unequal Viscosity: Can Mixing be Independent of Stirring Rate at a Large Viscosity Ratio?

Mixing liquids with unequal viscosity involves complex flows and a nontrivial diffusive feedback. As an insightful reference case, we study the deformation of a spherical blob with viscosity λη, sheared in a miscible bath with viscosity η. Experiments resolve the transition from unbounded stretching, at low λ, to rollinglike motion, at large λ. In between the blob is transiently substretched before destabilizing into swirling structures. Exact solutions of the flow recover all three regimes and predict a transition ratio λ_{c}≃3.975. We discuss the dramatic impact of the flow transition on mixing and propose scaling laws for the blob mixing time in the limit of large Péclet numbers, suggesting mixing could be independent of shear rate at large λ.

Simulation of special-shaped graded particulate hydraulic transport in deep-sea mining scenarios

Hydrodynamic transport is crucial in deep-sea mining engineering for conveying materials. This study investigates the impact of various particle shapes on slurry transport efficiency and flow characteristics at higher concentrations. A numerical method combining computational fluid dynamics (CFD) and the discrete element method (DEM) within the Euler-Lagrange framework is employed to simulate the flow and hydrodynamic properties of graded heterogeneous coarse particles in a deep-sea hydraulic lift pipe. The reliability of the simulations is verified through comparisons, focusing on feed concentration and particle gradation effects on dynamic characteristics and flow patterns. The study quantitatively analyzes concentration distributions under various flow regimes for different particle shapes and conveying concentrations in a vertical pipeline system. Flow characteristics under clogging conditions are described, considering flow transition and concentration distribution. Additionally, conditions for stable transportation are discussed concerning particle forces and transport reliability.

Comparison of natural convection in liquid gallium under horizontal and vertical magnetic fields

The dynamics of two-dimensional natural convection in liquid metal under the influence of magnetic fields within a confined square enclosure are numerically investigated using a high-accuracy method. The study focuses on the flow transition process influenced by both horizontal and vertical magnetic fields, examining the impacts of temperature difference, magnetic field strength, and orientation on flow characteristics and heat transfer. The range of Rayleigh numbers (Ra) explored is from 104 to 106, while Hartmann numbers (Ha) vary from 0 to 100. Liquid gallium is used as the working fluid with a Prandtl number (Pr) of 0.025. Our investigation reveals rich variations in flow patterns, categorized into unsteady periodic, steady “two-in-one” vortex, and steady single vortex states. As Rayleigh numbers increase, a complex series of flow transitions is observed, leading to enhanced flow dynamics. The transition from a steady state to periodic motion is accompanied by a notable increase in heat transfer efficiency. However, increasing the strength of the magnetic field suppresses the flow. A sufficiently strong suppression transitions the flow from periodic motion back to a steady state, resulting in a gradual decrease in heat transfer efficiency. For the parameters considered, the suppression efficiency of horizontal magnetic fields is stronger than that of vertical ones, especially when Ra>6×105 and Ha=100, with a 14% greater suppression efficiency. A scaling law for heat transfer is also identified: Nu:Ra/Ha2γ, where 14≤γ≤12, independent of the magnetic field orientation.

Torque and heat transfer characteristics in Taylor–Couette turbulence with an axially grooved cylinder

To describe the aerodynamic and thermal effects in the flow between the slotted stator and rotor of electric motors, we have conducted direct and large eddy simulations using the lattice Boltzmann method. The flow between the stator and rotor is influenced by turbulence and Taylor–Couette (TC) vortices. Axial grooves (slots) are incorporated either on the stationary outer cylinder or the rotating inner cylinder. These groove shapes and numbers are designed based on the groove geometry of drive motors used in commercial electric vehicles. The radius ratio of the TC flow configuration in this study is 0.955, and the simulated bulk Reynolds numbers reach up to 21000 which corresponds to the Taylor number of Ta=4.63×108. The characteristics of torque and heat transfer are analysed by comparing cases with and without grooves. Regardless of the groove placement, it is suggested that while the grooved surface effects are not significant on torque and heat transfer performance at Taylor numbers Ta≤107, where Taylor vortices are still evident, the effects become pronounced at Ta≥108 as the flow transitions to the ultimate regime.

Active Fréedericksz Transition in Active Nematic Droplets

Active nematic liquid crystals have the remarkable ability to spontaneously deform and flow in the absence of any external driving force. While living materials with orientational order, such as the mitotic spindle, can self-assemble in quiescent active phases, reconstituted active systems often display chaotic, periodic, or circulating flows under confinement. Quiescent active nematics are, therefore, quite rare, despite the prediction from active hydrodynamic theory that confinement between two parallel plates can suppress flows. This spontaneous flow transition—named the active Fréedericksz transition by analogy with the conventional Fréedericksz transition in passive nematic liquid crystals under a magnetic field—has been a cornerstone of the field of active matter. Here, we report experimental evidence that confinement in spherical droplets can stabilize the otherwise chaotic dynamics of a 3D extensile active nematics, giving rise to a quiescent—yet still out-of-equilibrium—nematic liquid crystal. The active nematics spontaneously flow when confined in larger droplets. The composite nature of our model system composed of extensile bundles of microtubules and molecular motors dispersed in a passive colloidal liquid crystal allows us to demonstrate how the interplay of activity, nematic elasticity, and confinement impacts the spontaneous flow transition. The critical diameter increases when motor concentration decreases or nematic elasticity increases. Experiments and simulations also demonstrate that the critical confinement depends on the confining geometry, with the critical diameter in droplets being larger than the critical width in channels. Biochemical assays reveal that neither confinement nor nematic elasticity impacts the energy-consumption rate, confirming that the quiescent active phase is the stable out-of-equilibrium phase predicted theoretically. Further experiments in dense arrays of monodisperse droplets show that fluctuations in the droplet composition can smooth the flow transition close to the critical diameter. In conclusion, our work provides experimental validation of the active Fréedericksz transition in 3D active nematics, with potential applications in human health, ecology, and soft robotics. Published by the American Physical Society 2024

Linear instability of viscous parallel shear flows: revisiting the perturbation no-slip condition

Linear stability analysis currently fails to predict turbulence transition in canonical viscous flows. We show that two alternative models of the boundary condition for incipient perturbations at solid walls produce linear instabilities that could be sufficient to explain turbulence transition. In many cases, the near-wall behaviour of the discovered instabilities is empirically indistinguishable from the classical no-slip condition. The ability of these alternative boundary conditions to predict linear instabilities that are consistent with turbulence transition suggests that the no-slip condition may be an overly simplified model of fluid–solid interface physics, particularly as a description of the flow perturbations that lead to turbulence transition in wall-bounded flows.

Numerical Simulation of Fixed-Free End Beam’s Modal Behaviour using Two-Way Coupled Fluid-Structure Interaction Approach

The fluid flow velocity stands as a pivotal parameter with a great influence on the mutual interaction between the fluid domain and structure. This paper focuses on structural deformation, structural velocity, von-Mises stress and frequency response of a fixed-free end beam using two-way coupled fluid-structure interaction within ANSYS Workbench. The parameters such as deformed fluid pressure and velocity were analysed across three diverse flow regimes: laminar, transitional and turbulent – each aligned with distinct fluid velocities. The outcomes show that the total deformation, velocity and von-Mises stress distribution of the fixed-free end beam increase as the inlet fluid velocity increases. As a result, the pressure and velocity distribution in the fluid flow which receiving the resultant or leftover structure deflection also increases as the incoming fluid velocity increases. Furthermore, the analysis probes the frequency response in turbulent flow conditions reveals higher values compared to laminar and transitional flows, albeit within the same natural frequency domain. This observation marks significant vibrational characteristics found in the presence of turbulent flow dynamics.

Experimental and Numerical Investigation of Slip Effect on Nanofiber Filter Performance at Low Pressures.

Nanofiber filters are widely used in air filtration applications due to their superior performance over microfiber filters. Velocity slip around nanofibers has been identified as a key factor contributing to their high figure of merit, yet its impact on filter performance, especially particle collection efficiency, remains unclear due to the difficulty in isolating the slip effect as the sole variable. This study combines experimental and simulation methods to investigate the slip effect by adjusting the air molecule mean free path, rather than varying fiber size as done in previous studies. Filter media with mean fiber sizes ranging from 16.2 to 0.084µm are utilized. An image-based regression method is developed to address the challenge of determining the solidity of thin nanofiber layers. The results show that the slip effect is enhanced as the testing pressure decreases, reducing pressure drop by less than 15% for microfiber filters and over 50% for nanofiber filters ≈100nm. The enhanced slip effect at low pressures (i.e., relatively low pressure compared to the ambient environment) significantly improves filtration efficiency, especially for particles larger than 100nm. It also proposes semi-empirical equations for predicting filter performance in slip and transition flow regimes.

Deflagration-to-detonation transition and detonation propagation in supersonic flows with hydrogen injection and downstream ignition

This study investigates the mechanisms of flame acceleration and deflagration-to-detonation transition (DDT) in supersonic flows using transverse hydrogen injection and downstream ignition. Utilizing the graphics processing unit accelerated adaptive mesh refinement approach, we examine the influence of downstream ignition jet pressure on DDT through high-resolution computational simulations. Our results indicate that the transverse injection of hydrogen into the supersonic mainstream generates strong turbulence and numerous vortices due to Kelvin–Helmholtz instability, enhancing fuel mixing efficiency along the flow but deviating from the ideal premixed state. Following the injection of the downstream ignition jet into the supersonic main flow, initial flame acceleration is less effective than in the premixed state due to the non-uniformity of the incoming flow. However, within the boundary layer, the flame remains stable, and the intense turbulence fosters shock–flame interactions. The convergence of multiple compression waves into a shock wave facilitates energy deposition, coupling with the flame to trigger local detonation via the reactive gradient mechanism. The detonation wave exhibits complex wavefront structures, including vertical and oblique fronts induced by boundary layer interactions. Ignition jet pressure significantly impacts the DDT process and detonation wave characteristics, reducing ignition time and affecting the detonation temperature, pressure, and propagation speed. This study provides valuable insights into the dynamics of flame acceleration and DDT in supersonic flows with non-uniform fuel distribution and downstream jet ignition. The findings highlight the critical role of ignition jet pressure in optimizing ignition and detonation processes, offering new perspectives for achieving low-energy, rapid detonation initiation within the tube.

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.

An experimental investigation of supersonic conical cooling films with angles of attack

While the flow mechanisms of two-dimensional supersonic cooling films have been studied in-depth, this paper used the nanoparticle planar laser scattering and particle image velocimetry techniques to investigate the flow of supersonic conical cooling films at different angles of attack (AOAs). The mainstream Mach number was Ma∞=3.8, and the supersonic conical cooling film was tangentially injected via a precisely calibrated Maj=2.8 annular nozzle. Initially, the streamwise boundary layer transition process without cooling film injection was analyzed. The boundary layer transition on the leeward side occurred prematurely, whereas on the windward side, the transition process was notably delayed. Subsequently, the supersonic conical cooling film flow was qualitatively and quantitatively evaluated from the perspectives of turbulent structures, and the time-averaged and statistical characteristics of the velocity field. On the windward side, as the ratio of static pressure decreased, the effective cooling length also decreased with an increase in AOA. On the leeward side, at a small positive AOA, the supersonic conical cooling film mixed with the low-energy fluid within the thickened inner layer of the mainstream boundary layer, which mitigated the growth rate of the mixing layer and ultimately enhanced the effective cooling length. With a further increase in AOA, the supersonic conical cooling film experienced the three-dimensional detrimental effects of crossflow-separation vortices and downwash mainstream on the leeward surface, resulting in a decrease in the effective cooling length.

Distribution of transitional flow deposits in sedimentary environments of mixed sand-mud turbidite system

Predicting facies distribution in turbidite systems is essential for resource exploration and identifying geohazards from an economic standpoint. Models that describe facies distribution depend heavily on understanding the mechanisms of particle transport and deposition. These processes are closely tied to the volume, concentration, and composition of sediment gravity flows, which display a range of behaviours between turbulent and laminar flow extremes. Recently, there has been a rise in studies on transitional flow deposits, although they remain much less understood than fully turbulent or laminar flows.For the first time, the distribution of Structured sandstone–mudstone associated with transitional flow deposits has been quantitatively presented for various sedimentary environments within the turbidite system. The distribution of Structured sandstone–mudstone was analysed for six areas of the Ropianka Fm (Skole Nappe, Polish Outer Carpathians) across twelve sedimentary environments, including channels, channel-levees, channel-mouths, and sub-environments of the depositional lobe. An increased amount of Structured sandstone–mudstone was observed in proximal settings away from the transport axis and in the distal parts of the turbidite system. It was found that flow transformation can occur in both proximal and distal zones of the turbidite system. Structured sandstone–mudstone in proximal zones is more often deposited from diluted mud-laden flows of small volume, where fine-grained cohesive material likely underwent vertical segregation. In contrast, Structured sandstone–mudstone formed basinward tend to be initially formed by larger flows. In proximal part of depositional lobe setting, the flow transformation due to longitudinal or longitudinal and vertical segregation of fine-grained cohesive material occurs slowly. At this point the velocity of sediment gravity flow is too high and the concentration of cohesive particles is too low for common development of cohesive bonds. Flow transformation accelerates in lobe fringe and lobe distal fringe/interlobe, due to flow deceleration, changes in sand-to-mud ratio, and the time required for development of cohesive bonds and the transition to a transitional flow regime, leading to increased deposition of Structured sandstone–mudstone distally.

Experimental study of oil-water two-phase flow patterns in a vertical large diameter pipe

The flow structure and the phase inversion have great influence on the flow measurement in vertical upward oil-water two-phase flow. This paper attempts to investigate the flow patterns in oil-water flows through a vertical upward large pipe with the designed mini-conductance array probes measurement system and the vertical multi-electrode array (VMEA) measurement system. According to the output waveform of the mini-conductance array probes, the oil-in-water flow, transition flow and water-in-oil flow can be identified effectively. The fluctuating signals of the VMEA is processed by the recurrence plot and the time-frequency representation, the results show that the VMEA conductance signal with average measurement characteristics can realize an effective identification of the above three flow patterns, which has a good agreement with the results of the mini-conductance array probes. Finally, via comparing with previous published flow pattern transition boundary models in different pipe diameters, it is founded that the boundary line of the transition to oil-in-water based on the kinematic wave-based model and the observation-based model in the same diameter pipe are consistent with our experimental data. And the pipe diameter affects the flow pattern transition, compared with the boundary in small diameter pipe, the phase inversion requires a larger oil velocity, and the transition zone becomes narrower in large diameter pipe.

Electro-osmotic flow instability of viscoelastic fluids in a nanochannel

The study of the complex rheological properties of viscoelastic fluids in nanochannels will facilitate the application of nanofluidics in biomedical and other fields. However, the flow of viscoelastic fluids in nanochannels has significant instabilities, and numerical simulation failures are prone to occur at high Weissenberg numbers (Wi). In this study, the simplified Phan-Thien-Tanner viscoelastic fluid model is solved using the log-conformation tensor approach, and the effects of rheological parameters of the viscoelastic fluid, such as the Weissenberg number (Wi), extensibility parameter (ε), and viscosity ratio (β), on the flow characteristics and flow instability within the nanochannel are investigated. The results indicate that the variation of rheological parameters of viscoelastic fluids has a significant effect on the flow state and flow instability of fluids in nanochannels. When the rheological parameters are in a specific range, the flow velocity and outlet current in the nanochannel exhibit relatively regular periodic fluctuations. As the flow transitions from an up-and-down moving single-vortex state to a symmetric double-vortex state, the average velocity of the central axis in the nanochannel is increased by about 15%. Furthermore, when Wi increases from 150 to 400, the length and height of the vortex increase by 50% and 100%, respectively.

Towards bespoke gas permeability by functionally graded structures in laser-based powder bed fusion of metals

Permeable, media transporting, components are an integral part in numerous technical applications. In gas turbines combustors, for example, gaseous oxidizer and fuel are transported separately into the burner, where they are injected and mixed, and subsequently combusted. The mixture homogeneity strongly affects the combustion performance and emissions formation and is, amongst other, determined by the spatial distribution of fuel injection ports. In this context, porous media provide the limiting case for a spatial distribution of media-injecting pores, yet is typically associated with a high pressure drop that yields a loss in efficiency. In this study, possibilities of achieving gas permeability in additively manufactured porous structures are investigated. The objective is to selectively functionalize the permeable layers for gaseous media supply with low pressure loss and, when needed, enable a targeted mixing of different gas streams. For this purpose, a laser-based powder bed fusion process (PBF-LB/M) was used in this study. It offers the opportunity to manufacture varying porosities inside complex monolithic metal parts. To produce the porous structures and to achieve gas permeability, the effect of scan rotation angle, hatch distance, build-up direction and length of the porous specimen is investigated. Due to the high temperatures present in combustion systems, the present work utilizes Inconel 718 material. The AM gas permeable specimen are experimentally characterized by means of surface topography, micro X-ray computed tomography (µXRCT) as well as flow and pressure loss test. The results show, that the AM process parameter provide effective control parameters to adjust the permeability. The strongest effect originates from the hatch distance for a given build-up direction. Depending on the scan rotation, the flow transitions from a turbulent pipe flow to a Darcy flow as present in conventional porous media. A structured alignment and connectivity of pores can be realized as evident in the µXRCT results, surface topography and the flow measurements. Residual powder, powder adhering to the pore walls and stochastic closure of pores or channels lead to deviations and need to be considered when designing respective parts. Nonetheless, the results further show that a directional dependence of the permeability and the build-up direction can be realized and controlled. Consequently, when considering the AM build-strategy in the design of components, this directed permeability can be functionalized in the generation of gas transporting and gas mixing layers separately by adjusting the AM processing parameter.

Dynamic Thermomechanical Modeling of Rock‐Ice Avalanches: Understanding Flow Transitions, Water Dynamics, and Uncertainties

AbstractThe rapid melting of glaciers and thawing of permafrost in mountainous regions have heightened the danger of rock‐ice avalanches. These avalanches pose a severe threat due to their potential to transform into water‐saturated debris flows. The catastrophic event in Chamoli, India, on 7 February 2021, illustrates the devastating consequences of such processes. Developing a model capable of predicting the dynamics and extent of these events is imperative for natural hazard science and disaster mitigation. In response, we propose a depth‐averaged rock‐ice avalanche model encompassing four distinct materials: rock, ice, snow, and water. The model integrates crucial physical processes, including frictional heating, phase changes, ground material entrainment, and air‐blast hazards. Through a system of mass and momentum balance equations extended with grain flow and internal energy equations, the model captures heat exchanges and resulting phase changes as the fragmented material flows. Focusing on identifying the primary water source in the flow and testing the model on the 2021 Chamoli event, we quantify water's influence on flow dynamics and regime transitions. However, uncertainties persist in heat transfer physics and quantifying the hydro‐meteorological state of the flow path. Our thermo‐mechanical model enables the simulation of complex avalanches and identifies key flow transitions: powder cloud formation and potential debris flow transformation. The study underscores the pivotal role of water in avalanche dynamics and the challenge of accurately quantifying water content within the flow, necessitating comprehensive ground assessments for effective disaster management.

Study on the transition mechanism of vibrating low-pressure turbine blades based on large Eddy simulation

The low-pressure turbine blades are susceptible to vibration issues due to their thin profiles and large aspect ratios. Blade vibration will significantly affect the evolution of the boundary layer and the flow state. This paper utilizes large eddy simulation to predict the development of the boundary layer on the suction side of low-pressure turbine blades at low Reynolds numbers (Re = 25,000). It introduces different vibration cases to elucidate the mechanisms by which blade vibrations influence boundary layer separation and transition. The study demonstrates that the introduction of vibration cases significantly reduces both the size of the overall spanwise vortices and their roll-up height. A staggered distribution of spanwise vortices, characterized by alternating high and low regions, is observed near the trailing edge of the vibrating blades. The shorter spanwise vortices develop rapidly, nearly traversing the process of hairpin vortices (Λ vortex) generation and development, and directly breaking down into smaller-scale vortices. This accelerates the transition process. Blade vibration primarily promotes turbulence reattachment by facilitating the transition process dominated by the K-H instability mechanism within the separating shear layer. Consequently, it effectively restricts the growth of the separation bubble on the suction side of the blades, significantly reducing aerodynamic losses. Moreover, increasing the vibration frequency within a certain range can amplify these effects, achieving up to a 23% reduction in total pressure loss compared to stationary blades.