The variable vaned diffuser has been used to widen the operating range of turbocharger compressors under high-pressure-ratio conditions. The effects of variable vaned diffusers on compressor performance and aerodynamic noise are investigated with the numerical approach in this paper. First, the numerical approach is validated using the compressor with a fixed diffuser. Then, a variable diffuser features three rotating centers, each with a distinct rotation angle. Finally, the aerodynamic performance, fluctuation pressure characteristics, and aerodynamic noise of the compressor with variable vaned diffuser are analyzed. The results indicate that the use of a variable vaned diffuser shifts compressor operating range toward lower flow rates with positive rotation angles, while negative rotation angles shift the operating range toward higher flow rates. The diffuser can effectively expand the compressor’s operating range within a rotation angle range of 0°–5° without significantly affecting its pressure ratio and efficiency. Compared to the rotation angle, the movement of the rotation center from the leading edge to the trailing edge has a relatively small impact on the compressor’s performance. Additionally, the rotation center affects the compressor’s noise, likely due to changes in the diffuser inlet and outlet radii caused by the rotation center, which influence the dynamic-static interference between the diffuser, volute, and impeller. Although the variation in the rotation center interferes with the results of the rotation angle’s effect on the compressor’s aerodynamic noise, a general trend can still be derived. Specifically, the variable-rotation angle diffuser with positive rotation angles increases the compressor’s sound pressure level (SPL), while negative rotation angles generally reduce the compressor’s noise. This is because the diffuser with positive rotation angles increases fluctuating pressures in the inlet duct, impeller passage, and diffuser passage, while negative rotation angles reduce fluctuating pressures in the inlet duct and impeller passage.

ABSTRACT Throughout the 50-year history of self-psychology, the concept of the nuclear self has been disputed. Intersubjectivity holds that, due to phenomenological circumstances, the self can never be static in a relationship but is always dynamic in the milieu. While the emphasis on dynamic interactions is welcomed, the abandonment of the nuclear self in its entirety forgoes Kohut’s emphasis on authenticity and misses the dynamic mechanics between the authentic self-organization and the ever-shifting selfobject milieu the self-structure adapts to. As an attempt to bridge the two concepts closer together, this paper uses the ecological systems model developed Urie Bronfenbrenner, ecological psychology developed by JJ Gibson, and pairing them with intersubjective systems theory to delineate specific operations and sectors of the intersubjective field that surrounds the nuclear self. This resulted in the emergence of two core concepts: the entangled self and the authentic self. These concepts use systemic thinking to extend the nuclear self-concept, the trailing edge, and the leading edge beyond the dyad, and clinical work is extended beyond empathy to empowerment strategies.

This study investigates cavitation evolution in the M350HD-60 mixed-flow pump impeller using a multi-method approach combining Rothalpy, Liutex vortex identification, Fourier transform, and wavelet analysis. Three cavitation stages (critical, severe, and fracture) were analyzed through vapor fraction distribution, vortex evolution, Rothalpy distribution, and pressure fluctuations. Results demonstrate that cavitation development significantly increases the vapor volume fraction, peaking at 0.78% near the suction side outlet during fracture cavitation. Liutex vortex analysis reveals concentrated vortex structures predominantly along the trailing edges of both suction and pressure surfaces. Rothalpy distribution analysis indicates cavitation-induced expansion of high-enthalpy regions toward the suction surface trailing edge and tip clearance diffusion toward adjacent blades. Frequency domain analysis identifies 48.33 Hz (twice shaft frequency) as the dominant pressure fluctuation frequency across all cavitation stages, with 24.17 Hz (shaft frequency) as secondary frequency. Notably, the suction surface leading edge monitoring point (S1) exhibits pronounced high-frequency (1600–2200 Hz) pressure fluctuations with amplitude escalation during cavitation progression. Continuous wavelet transform further reveals that critical cavitation produces the most intense low-frequency (19.33–96.67 Hz) pressure fluctuations with periodic energy variations. As cavitation progresses, overall energy amplitudes decrease, but periodic high-frequency fluctuations intensify at S1, located at the front edge and tip of the blade suction surface. This study combines the Rothalpy and Liutex methods to quantify the cavitation effect in mixed-flow pumps, providing new insights into the identification and performance evaluation of cavitation stages in hydraulic machinery.

Appropriate numerical methodologies should be selected for accurate, efficient computational simulations. This study is a comprehensive comparative analysis of the flow phenomena within an axial-flow pump that are predicted using numerical approaches: unsteady Reynolds-averaged Navier–Stokes (URANS), detached-eddy simulation (DES), and large-eddy simulation (LES). The shear stress transport k−ω turbulence model, combined with reattachment modification, is used for URANS prediction, while the wall-adapting local eddy-viscosity model for subgrid-scale (SGS) closure is used for LES. The grid resolution is verified to minimize the dependence of LES predictions on the SGS model. The numerical predictions are compared with the experimental data to assess the accuracy and reliability of the three approaches. The flow characteristics of the axial-flow pump involve cavitation and vortex structures generated by separation flows, tip leakage vortices (TLV), and trailing-edge (TE) vortices and their wake. In URANS, these phenomena are underestimated and have simple structures, limited spatial resolutions, and reduced temporal dependence. URANS predicts the TLV as a nearly straight structure, whereas DES and LES resolve it as an intricate spiral vortex. However, DES overpredicts vortex structures and vorticity intensities in certain regions. LES provides the most detailed and comprehensive depiction of flow phenomena, capturing numerous small-scale, highly convoluted vortex structures that illustrate their formation, evolution, and dissipation. URANS and DES exhibit limitations in resolving complex TE vortices, but LES effectively captures them as vortex shedding that gradually dissipates downstream. Additionally, LES reproduces the laminar–turbulent transition in near-wall flows, which cannot be achieved by URANS and DES.

The convection velocity is an important parameter for characterizing traveling vortices in turbulent flow, and its calculation methods are evolving with the measurement technologies. Using high-frequency particle image velocimetry and the synchronized far field sound pressure measurements, different methods are explored to calculate the convection velocity, i.e., the velocity decomposition, the velocity cross correlation, the vortex time trajectory, the frequency-wave number contour, as well as the time delay between velocity and noise signal methods. The methods have been applied on a test case of airfoil trailing edge with vortex shedding, which includes laminar separation bubble, acoustic feedback loop, and tonal noise generation phenomena. A relative standard deviation of 2.71% of the convection velocities has been noticed from the five methods under the same flow condition. The cross correlation methods show the advantage of convection velocity determination along the chordwise direction. The frequency-wave number method seems the most robust method for its global calculation in terms of spatial and time domain. At the end, all the methods have been applied to investigate the trend of convection velocity vs free stream velocity and angle of attack. The convection velocity increases as the angle of attack decreases and flow speed increases, which is ascribed to the separation bubble moving upstream.

Novel herringbone riblets for mitigating flow separation in a linear diffuser cascade

High-advance-ratio rotorcraft face reverse flow effects on a substantial portion of the retreating blades. Similar to a leading-edge vortex, the reverse flow dynamic stall vortex was found to have a significant impact on unsteady blade loading and pitching moment evolution due to its strength and proximity to the blade surface. The present work aims to assess how reverse flow dynamic stall vortex formation and advection are affected by trailing-edge curvature and how the blade pitching moment can be reduced by altering the center of pressure. Experimental and numerical data at an advance ratio of 1.00 and high collective blade pitch angles revealed that vorticity transport within the reverse flow dynamic stall vortex is dominated by the shear flux at the aerodynamic leading edge. A blunt trailing edge reduced this shear flux and consequently the dynamic stall vortex growth significantly. Unlike in the case of a hovering rotor, the convection term was found to switch direction in the reverse flow region, which is likely related to vortex shedding in reverse flow. The selective use of blunt trailing-edged blade sections at inboard stations could mitigate severe pitching moments that lead to high pitch link loading.

Abstract Wingtip devices technology in recent decades has become popular to improve the aerodynamic efficiency of aircraft where this device can reduce induced drag even though other induced drag reduction technologies have been applied. However, the application of this technology often constrained by penalty or offset problems from other drag components such as profile drag and increased bending moments at the wing root. To overcome this problem, we can utilize many research results that have been carried out to reduce the increase in profile drag and the increase in bending moments at the wing root so that the benefits obtained by applying wingtip devices are not lost due to the increase in profile drag. Here the research is conducted to find the appropriate configuration in reducing the strength of the tip trailing vortex and distribute the trailing edge vortex more evenly for some existing wingtip devices. Positive results were obtained by analyzing the flow pattern and pressure contour around the wingtip and existing wingtip devices. Efforts to reduce induced drag can also be done by adding additional tip devices at the end of existing wingtip devices without increasing the length of the span. The results, for example, for the double raked configuration, can reduce induced drag from 8% to 10%. This increase does not seem too big but this increase is quite significant in reducing fuel or improving aircraft performance.

The configuration of the blade's trailing edge (TE) significantly impacts the operational efficiency of a centrifugal pump. Modifying its form is highly effective for enhancing the internal turbulent flow and fluctuating pressure. This work aims to numerically examine how the shape of the TE affects the flow and structural characteristics of a low-specific speed centrifugal pump. To elucidate the process behind the impact of TE on pump performance, six representative TEs, including original trailing edge (OTE), Bezier trailing edge (BTE), ellipse trailing edge (ETE), trimmed at the pressure side (TPS), trimmed at the suction side (TSS), and trimmed at both side (TBS) have been examined. An analysis is conducted to investigate the distribution of pressure pulsation, shaft power, and energy loss along the streamwise direction in the pump component. The entropy generation method illustrates the extent and spatial distribution of energy dissipation. A transient structural study is conducted on the impeller, examining various TEs. The findings indicate that TE considerably influences the centrifugal pump performance. A modification in TE has led to an increase in both head and pressure, and the impeller with the ETE would reach the highest efficiency of 81.79% with a 6.4% increase relative to the original model. In addition, the analysis covers structural behaviors, such as total deformation and equivalent stress.

ABSTRACTReliable wind turbine blades with low risk of structural failure require a robust structural failure assessment methodology, involving thorough experimental testing combined with non‐destructive inspection (NDI) techniques for structural health monitoring (SHM). In this study, multiple NDI techniques are demonstrated and compared on an intermediate‐scale fatigue‐rated multi‐axial test rig. Here the effectiveness of a retrofitted shear‐web inserted in the max‐chord region between the trailing edge sandwich panels is demonstrated on the inner 15 m root section of a 34 m wind turbine blade from SSP technology A/S. A dual degree‐of‐freedom load configuration, chosen to maximize out‐of‐plane trailing edge panel deformations, is used to provoke and drive disbonding at the foot of the shear‐web. The disbond propagation is monitored with strain gauges, a wire potentiometer, acoustic emission sensors and digital image correlation (DIC). The wire potentiometer clearly detects disbond growth when trailing edge panel breathing deformation increases from 7.5 to 34 mm. AE sensor data also aligns well with potentiometer outputs, with acoustic sensors offering large coverage and easy blade instrumentation. Simple, reliable and cost‐effective sensor technologies are of key importance for field deployment of structural health monitoring. Combining intermediate scale‐blade testing, as presented in this study, with efficient sensing and continuous monitoring systems provides information that enhances blade reliability through a basic understanding of structural blade behavior.

Manipulation of flow and flow control by way of flow control devices is vital in enhancement of aerodynamic efficiency. Passive flow control devices are widely used in aerodynamic systems for their efficiency and cost effectiveness. Three airfoils are used in this study, the Clark-Y airfoil, NACA 2410 airfoil and the NACA 6412 airfoil. Each airfoil has a span of 0.98m and chord length of 0.3m. This research study incorporates a cylindrical trailing edge with length equal to the wingspan of the airfoil and radius 0.025c onto each airfoil. The aerodynamic performances of each airfoil in comparison with each other are obtained. Ansys software is used for the entirety of this study with lift and drag coefficients monitored through 0°, 6°, 12° and 18° angles of attack. A rectangular domain is generated around the airfoil extending 2c above and below the airfoil, domain inlet and outlet are positioned -1.3c and 10.3c from the leading-edge of the airfoil respectively and domain width equal to the span of the airfoil. The transition SST (four-equation) model is utilized for each CFD simulation with a constant inlet velocity 1.76 m/s, a y+ value 7.9×10-5 m and polyhedral meshing for the rectangular domain. The numerical investigation indicates highest percentage increase in lift coefficient for the NACA 6412 airfoil by 29.7%, 25.67%, 16.8% and 17.63% at 0°, 6°, 12°and 18° angles of attack respectively.

This study numerically investigates clocking effects on pump–turbine hydraulic performance in pump mode. Analyzing the influence of clock position on pressure loss characteristics under three flow conditions and its correlation with internal flow. By integrating local hydraulic loss theory and vortex evolution analysis, the operational mechanism is elucidated. Key results show that the stay vane clock position significantly impacts off-design conditions, causing maximum efficiency differences of 0.855% at 0.8Qd and 0.805% at 1.2Qd. At the design condition, guide vane clocking position has a more pronounced effect, yielding a maximum inter-scheme efficiency difference of 0.330%. The optimal scheme positions the tongue at the guide vane trailing edge and 1/4 of the stay vane flow path, minimizing time-averaged losses and enhancing flow stability. The clocking effect alters the scale and intensity of volute dual-vortex structures, significantly increasing energy loss at vortex interfaces, with volute loss identified as the primary factor in performance variation. This work provides a theoretical foundation for applying clocking effects in pump–turbine engineering.

The excavation of high-speed subgrade has formed a large number of subgrade landslides, which have always been a potential threat to highway traffic, and the stability of landslides has an important impact on ensuring the normal operation of highways and traffic safety. In this paper, the on-site engineering geological investigation of a high-speed subgrade landslide is carried out, and the ring shear test is carried out by taking soil samples from slip zone, and the evolution relationship between the friction angle and cohesion in slip zone soil with shear displacement is analyzed by using the Moore-Coulomb theory, and the dynamic evolution law of the shear strength of slip zone soil is revealed. Combined with the typical residual thrust model and the finite element numerical model, the deformation failure mechanism and dynamic stability of the landslide were systematically analyzed. The following conclusions were drawn: The landslide slid again under the inducement of rainfall and gravity, and the overall performance was collapse-slip failure. The friction angle in slip zone soil shows the attenuation trend of the logistic model, and the cohesion shows the attenuation trend of the power function model. With the continuous deformation of landslide, the deformation displacement of landslide gradually showed an increasing trend, and the deformation of the slip zone gradually penetrated from the leading edge and the trailing edge, and the simulation results were basically consistent with the results of the landslide field investigation. With the increase of landslide displacement, the stability of landslide gradually decreases from the peak stability, and finally maintains the residual stability, which is between 1.07 and 1.08. Monitoring and early warning measures should be carried out at any time in the later stage. The landslide stability evaluation has an important safety early warning effect on the normal operation and traffic safety of the expressway.

This paper presents an experimental application of reactive control to jet installation noise based on destructive interference. The work is motivated by the success of previous studies in applying this control approach to mixing layers (Sasaki et al. Theor. 2018b Comput.FluidDyn. 32, 765–788), boundary layers (Brito et al. 2021 Exp.Fluids62, 1–13; Audiffred et al. 2023 Phys.Rev.Fluids8, 073902), flow over a backward-facing step (Martini et al. 2022 J.FluidMech. 937, A19) and, more recently, to turbulent jets (Maia et al. 2021 Phys.Rev.Fluids6, 123901; Maia et al. 2022 Phys. Rev. Fluids7, 033903; Audiffred et al. 2024b J. FluidMech. 994, A15). We exploit the fact that jet–surface interaction noise is underpinned by wavepackets that can be modelled in a linear framework and develop a linear control strategy where piezoelectric actuators situated at the edge of a scattering surface are driven in real time by sensor measurements in the near field of the jet, the objective being to reduce noise radiated in the acoustic field. The control mechanism involves imposition of an anti-dipole at the trailing edge to cancel the scattering dipole that arises due to an incident wavepacket perturbation. We explore two different control strategies: (i) the inverse feed-forward approach, where causality is imposed by truncating the control kernel, and (ii) the Wiener–Hopf approach, where causality is optimally enforced in building the control kernel. We show that the Wiener–Hopf approach has better performance than that obtained using the truncated inverse feed-forward kernel. We also explore different positions of the near-field sensors and show that control performance is better for sensors installed for streamwise positions downstream in the jet plume, where the signature of hydrodynamic wavepacket is better captured by the sensors. Broadband noise reductions of up to 50 % are achieved.

To investigate the effect of normal manufacturing errors on the aerodynamic performance of supersonic cascade, a five-dimensional geometric variability model of the profile caused by normal manufacturing errors has been constructed based on Gaussian process and principal component analysis. A surrogate model has been proposed using the non-intrusive chaos polynomial method based on sparse grid technology, to predict the effect of manufacturing errors on the aerodynamic performance and flow of supersonic cascade under different conditions. Finally, based on a loss source model that is proposed to quantified the losses of various parts of the flow field, the corresponding flow mechanism has been explained. The results show that under the influence of random manufacturing errors: (1) In terms of aerodynamic performance, the total pressure loss coefficient of the supersonic cascade is approximately normally distributed, with no significant difference between the mean value and the nominal value but a huge deviation (16%∼25%) under different working conditions. For each working condition, the total pressure loss coefficient is most sensitive to the manufacturing errors of the leading edge, and is more sensitive to the manufacturing error of the suction surface than to the manufacturing error of the pressure surface, with the sensitivity gradually decreasing from the leading edge to the trailing edge. (2) In terms of flow field distribution, the mean flow field distribution differs significantly from the nominal flow field distribution at the area of shock, accompanied by huge fluctuations. And there are differences in the flow fluctuations under different working conditions. (3) The mechanism is that the manufacturing error of the leading edge would affect the bow shock strength and the acceleration process at leading edge, which will cause different degrees of impact on the wave pattern under different conditions, ultimately leading to cascade losses with different degrees of deviation.

The present study reports the outcome of an experimental study of organic vapor trailing edge flows. As a working fluid, the organic vapor Novec 649 was used under representative pressure and temperature conditions for organic Rankine cycle (ORC) turbine applications characterized by values of the fundamental derivative of gas dynamics below unity. An idealized vane configuration was placed in the test section of a closed-loop organic vapor wind tunnel. The effect of the Reynolds number was assessed independently from the Mach number by charging the closed wind tunnel. The airfoil surface roughness and the trailing edge shape were evaluated by experimenting with different test blades. The flow and the loss behavior were obtained using Pitot probes, static wall pressure taps, and background-oriented schlieren (BOS) optics. Isentropic exit Mach numbers up to 1.5 were investigated. Features predicted via a simple flow model proposed by Denton and Xu in 1989 were observed for organic vapor flows. Still, roughness affected the downstream loss behavior significantly due to shockwave boundary-layer interactions and flow separation. The new experimental results obtained for this organic vapor are compared with correlations from the literature and available loss data.

Truss-type lattice structures exhibit great application potential for turbine blade cooling. However, current research on lattice structures is limited to rectangular cooling channels, leaving their heat transfer characteristics in the wedge-shaped channels of turbine blades unclear. This study employed transient liquid crystals (TLC) technique and numerical simulations to investigate the flow and heat transfer characteristics of Kagome and Body Centered Cubic (BCC) lattice structures within a wedge-shaped channel, representing the trailing edge of a turbine blade. Results from a traditional pin-fin channel were used as a comparison benchmark. The findings indicate that the decrease in the height of the wedge-shaped channels along the flow direction leads to mainstream acceleration, resulting in a continuous enhancement of heat transfer on the channel walls. Unlike rectangular channels, the pressure loss caused by the lattice structures in the wedge-shaped channels is comparable to that of the pin fins, thereby improving the overall thermal efficiency. Additionally, the unique topology of the Kagome lattice structure causes low-momentum vortex pairs behind its central intersection to continuously rise in the wedge-shaped channel, ultimately washing over the top endwall and resulting in a linear increase in the heat transfer level. Overall, this study reveals that replacing pin fins with lattice structures at the turbine trailing edge can enhance the cooling performance without significantly impacting the pumping power.

As the core hydraulic model to absorb the fluid into the propulsion system and guide the operating direction of the navigating underwater vehicle, the rudder plays an important role in determining the flow stability of the underwater vehicle. Installed with an independently developed high-speed water-jet pump with a rotating speed of 17 500 r/min, a hydraulic model of a high-speed autonomous underwater vehicle (AUV) with a cruising speed of 50 kn was constructed, and the operational performances for the high-speed underwater vehicle under different bionic rudders were analyzed. A comparative analysis leads to the following conclusions: (1) The bionic leading edge, the bionic trailing edge, and the bionic leading–trailing edge can all improve the underwater vehicle operating performances at different cruising speeds. At the design speed of 50 kn, the underwater vehicle with the bionic leading–trailing edge achieves head increase in 0.81 m, power reduction of 1.81 kW, efficiency increase in 0.31%, and thrust increase in 65.74 N; (2) in relative to the bionic leading edge, the bionic trailing edge can greatly decrease the flow losses in the propulsion system with the entropy production theory, reducing the entropy generation rate of the inlet channel and impeller by 1.48 and 2.04 W/K, respectively; (3) the external sound field analysis reveals that the three bionic rudders all can reduce the noise, and the bionic trailing edge and the bionic leading and trailing edges have the better noise reduction effects at the near field, reducing noise by 0.68 and 0.72 dB, respectively; (4) via the bionic mechanism analysis with pressure pulsation and mode decomposition, it was found out that the bionic trailing edge of the rudder body significantly improves the pressure pulsations at the inlet of the water-jet propulsion channel, so that operating performances of the propulsion system as well as the underwater vehicle can be improved. In summary, the design of the bionic rudder enhances flow stability in the AUV propulsion system, boosts the overall performance of the AUV, reduces energy consumption, and contributes to the efficient operation of the AUV.

In this research, the vortex-induced vibration (VIV) mechanism is investigated from the viewpoints of vibration response, aerodynamic characteristics, and vortex shifting based on a three-dimensional large eddy simulation of a 5:1 rectangular cylinder at different vibration stages. An explanation of the self-limiting amplitude characteristics of the prolate cylinder under VIV is given with emphasis on the flow field point of view. With the increase in the reduced velocity, the phase shift of the vortex core relative to the vibration velocity gradually increases, resulting in the increase in the aerodynamic force phase angle relative to the vibration velocity, which is the main reason for the deviation of the maximum amplitude velocity from the resonance velocity. In addition, the position of the vortex core center gradually moves to the trailing edge with the increase in the reduced velocity, which results in a more significant contribution of the distributed aerodynamic force near the trailing edge to the vibration amplitude. From the standpoint of flow field evolution based on dynamic mode decomposition, the vibration-frequency and Strouhal-frequency modes are in a competitive relationship, and the energy changes between the two modes and the vorticity strength in the flow field influence the VIV development stage of the rectangular cylinder.

Abstract Unsteady flow loss mechanisms in compressors are critical for aerothermodynamic performance. This study proposes a method integrating entropy generation modeling and control volume analysis to evaluate unsteady losses. Using axially, spanwise, and azimuthally divided control volumes with nonlinear harmonic simulations, time-averaged and unsteady entropy generation distributions were analyzed in a transonic axial compressor. Results identified high entropy generation in rotor region, localized at the mid-to-rear chord, trailing edge, and blade tip. Key mechanisms include: 1. Shock wave/boundary layer interaction causing trailing edge boundary layer thickening and entropy generation rise. 2. Shock wave/leakage vortex interaction at the blade tip, involves mixing between the post-shock leakage flow and secondary leakage flow from adjacent passages, generating high entropy generation. 3. Rotor wake and stator leading edge interaction, inducing unsteady low-pressure zones and entropy generation fluctuations in the stator domain. The method effectively quantifies entropy generation and clarifies flow physics, aiding compressor design optimization.