Pressure Gradient Research Articles

Investigating Pressure Gradient Dynamics in Two-phase Fluid Flow through Porous Media: An Experimental and Numerical Analysis

Investigating Pressure Gradient Dynamics in Two-phase Fluid Flow through Porous Media: An Experimental and Numerical Analysis

Human Amniotic Epithelial Cell Transplantation is Safe and Well Tolerated in Patients with Compensated Cirrhosis: A First-in-Human Trial.

Placenta-derived human amniotic epithelial cells (hAEC) exhibit anti-inflammatory and anti-fibrotic effects in cirrhosis models. We conducted a first-in-human phase I clinical trial to assess the safety and tolerability of hAEC in adults with compensated cirrhosis. We examined increasing and repeated doses of hAEC in 9 patients in 3 cohorts. Cohort 1 patients received 0.5 × 106/kg hAEC in one IV infusion. Cohort 2 patients received 1 × 106/kg hAEC in one IV infusion. The patients in cohort 3 received 1 × 106/kg hAEC on days 0 and 28. Here, we report follow-up to post-infusion day 56 (D56), during which no serious adverse events occurred. Six patients experienced no study-related adverse events, while 3 patients reported mild (grade 1) headaches that were possibly infusion-related. A transient decrease in serum platelet count occurred in all patients, which returned to baseline screening values by day 5. FIB-4 values to assess fibrosis were significantly lower at D56. Although not statistically significant, serum AST levels and liver stiffness measurements at D56 were lower than those at baseline. The hepatic venous pressure gradient, a measure of portal hypertension, declined in 4 patients, did not change in 3 patients, and increased in 2 patients. In conclusion, intravenous infusion of allogeneic hAEC in patients with compensated cirrhosis at the doses used in this study was safe and well tolerated, with no difference observed between 1 and 2 doses. Decreased hepatic inflammation, liver stiffness, and portal hypertension support larger studies aimed at identifying patients who may benefit from this therapy. Clinical Trial registration: The trial was prospectively entered on the Australian Clinical Trials Registry (ANZCTR12616000437460).

Chemical dynamics in a radioactive platinum -cerium oxide-water mixture within a vibrating Riga channel subject to sudden pressure gradient onset

Chemical dynamics in a radioactive platinum -cerium oxide-water mixture within a vibrating Riga channel subject to sudden pressure gradient onset

Self-expandable transcatheter valve is a potentially useful option for a failing small surgical aortic bioprosthetic valve.

Trans-catheter aortic valve implantation inside a failing surgical aortic valve bio-prosthesis has become an alternative for patients at high risk for redo surgical aortic valve replacement. However, the correlation between the size of the failing surgical aortic valve and the occurrence of prosthesis-patient mismatch after trans-catheter implantation is still controversial. The aim of this study is to analyze and report the results in Japanese patients. Thirty patients who underwent trans-catheter aortic valve implantation inside a failing surgical aortic valve at our hospital were retrospectively reviewed with results from echocardiography and computed tomography. The patients' mean age was 84.5 ± 4.8years. The mean body surface area was 1.42 ± 0.13 m2. The cohort was divided into two groups according to the size of the failing bio-prosthesis: small (≦19mm) and large (> 19mm). There were no significant differences in mean pressure gradient (12.2 ± 4.0mmHg vs. 11.1 ± 1.2mmHg; p = 0.54) and effective orifice area index (1.00 ± 0.26cm2/m2 vs. 0.99 ± 0.25cm2/m2; p = 0.92) between the groups at 6months after trans-catheter implantation. The incidence of moderate (38.5% vs. 28.6%; p = 0.59) and severe (0% vs. 7.1%; p = 0.33) prosthesis-patient mismatch was equivalent. There was no significant difference in survival between the two groups (log-rank test p-value = 0.08). Trans-catheter implantation inside a failing small aortic valve did not increase the frequency of prosthesis-patient mismatch in this Japanese cohort.

Challenges and perspective on the modelling of high-Re, incompressible, non-equilibrium, rough-wall boundary layers

The present paper gives an overview of the recent modelling activities under NATO-STO AVT-349, focussed on the understanding and modelling of boundary layers for incompressible, high-Reynolds-number flows subject to non-equilibrium conditions such as strong pressure gradients, three-dimensionality, and surface roughness and heterogeneity. For this, we consider simpler cases where the above flow conditions are present separately or in a reduced number of combinations. First, we focus on the effect of roughness on the outer flow and the problems associated to its characterisation and prediction, with a particular emphasis on the conditions necessary for outer-layer similarity to hold. We then focus on how the presence of adverse and favourable pressure gradients affects the effect of roughness, and to what extent the figures used to quantify it are still useful under such conditions. We also consider the effect of surface heterogeneity, the shortcomings when modelling it and how these can be addressed. We then focus on the effect on the outer layer of pressure gradients and non-equilibrium conditions, to what extent similarity holds in those conditions, and how RANS models perform for such flows, identifying routes for their improvement to handle pressure gradients and non-equilibrium. We also discuss the use of data-driven and machine-aided methods in closure models.

Development of a neural network model for peeling–ballooning stability analysis in the KSTAR tokamak pedestals

The neural network model, MISHKA-NN is developed to mitigate the computational burden associated with the linear ideal magnetohydrodynamic (MHD) stability analysis of the pedestal based on the peeling–ballooning (P–B) model. By utilizing both 1D plasma profiles (current density, pressure gradient, and safety factor) and 0D parameters (plasma geometry, total current, and toroidal mode number), the model predicts linear growth rate of edge-localized ideal MHD instability in a given equilibrium state. By enabling the prediction of each instability within a second, the model reduces the time required for plotting a pedestal P–B stability diagram ( j−α diagram) from approximately 100 CPU hours to a few CPU minutes. Notably, even with the utilization of parametric pressure and current profiles and plasma boundary shapes for the training dataset, the model shows a satisfactory level of performance in benchmarking the j−α diagram for the reconstructed equilibrium from a KSTAR tokamak experiment. We anticipate the model to serve as a versatile alternative to 2D linear MHD stability codes, alleviating numerical costs.

Impact of Pressure and Temperature on Charge Accumulation Characteristics of Insulators in Direct-Current Gas-Insulated Switchgear

Direct-current gas-insulated switchgear (DC GIS) is an important device for promoting the lightweight and compact design of offshore wind power platforms. Gas pressure and temperature gradients are crucial factors that must be considered during the design process of the DC GIS. In this study, the multi-physics coupling model of basin insulators considering surface charge accumulation was established, and the corresponding real-sized insulator surface charge measurement platform was constructed. The effects of gas pressure and temperature gradient on the surface charge accumulation characteristics were investigated, respectively. The results show that the effect of gas pressure on the surface charge distribution characteristics depends on the dominant mode of surface charge. When volume conduction is dominant, the effect of gas pressure on the surface charge is negligible. However, when gas conduction is dominant, the accumulation of a uniform charge pattern on the insulator surface increases with the rise in gas pressure. Furthermore, due to gas convection, the temperature of the upper part of the DC GIS is significantly higher than that of the lower part, which leads to a temperature difference between the upper and lower surfaces of the insulator. The charge density on the insulator upper surface near the central conductor rises with the increase in load current.

Prognostic Value of Aortic Valve Calcification in Nonsevere Aortic Stenosis with Preserved Ejection Fraction.

Aortic valve calcification(AVC) is prognostic in patients with aortic stenosis(AS). We assessed the AVC prognostic value in nonsevere AS patients. We conducted a retrospective study of 395 patients with nonsevere AS, LV ejection fraction ≥50%. The Agatston method was used for computed tomography AVC assessment. The log-rank test determined the best AVC cutoffs for survival under medical surveillance: 1185 AU in men and 850 in women, lower than the established-cutoffs for severe AS(2064AU in men and 1274 in women). Patients were divided into three AVC groups based on these cutoffs: low(<1185 AU men and <850 women), sub-severe(1185-2064AU men and 850-1274 women) and severe(>2064AU men and >1274 women). Of 395 patients(mean age 73 ± 12 years, 60.5% men, aortic valve area 1.23 ± 0.30cm2, mean pressure gradient 28 ± 8 mmHg), 218 underwent aortic valve intervention(AVI) and 158 deaths occurred during follow-up, 82 before AVI. Median survival time under medical surveillance was 2.1[0.7-4.9]years. Compared to the low AVC group, both sub-severe and severe AVC groups had higher risk for all-cause death under medical surveillance after comprehensive adjustment including echocardiographic AS severity and coronary artery calcium score(all p ≤ 0.006); while mortality risk was similar between sub-severe and severe AVC groups(all p ≥ 0.2). This mortality risk pattern persisted in the overall survival analysis after adjustment for AVI. AVI was protective of all-cause death in the sub-severe and severe AVC(all p ≤ 0.01), but not in the low AVC groups. Sub-severe AVC is a robust risk-stratification parameter in patients with nonsevere AS and may inform AVI timing.

Bionic noise reduction design of axial fan impeller

Fans are integral equipment widely employed in both industrial settings and daily life. However, a persistent challenge in fans design lies in the inherent conflict between aerodynamic performance and noise levels. Improving aerodynamic efficiency often results in a compromise of acoustic performance. To tackle this issue, we employed the bionic design method to craft a novel axial fan impeller featuring a bionic curved hub and bionic serrated leading edges. The impact of structural optimization on the aerodynamic and acoustic properties of the impeller, as well as the influence of optimization parameters on these properties, were systematically investigated through numerical simulations. The bionic impeller was then fabricated using 3D printing, and the aerodynamic and noise performance of the impeller were experimentally evaluated by integrating it into an external air conditioner. Comparison of the flow field and sound field data between the optimized and prototype impellers revealed noteworthy outcomes. The curved wall at the bionic hub’s tail effectively diminished the pressure gradient on the hub surface, directing the airflow toward the rear end of the hub. This design enhancement significantly reduced the turbulent area behind the prototype impeller’s hub. Additionally, under the appropriately designed, the bionic serrated structure could effectively reduce the contact area between the blade’s leading edge and incoming flow. This led to the dispersion of stress concentrations and the inhibition of strong turbulence generation. Notably, the experimental results indicated a 3.7% increase in air volume flow rate and a 2.3 dB reduction in noise for the optimized impeller compared to the prototype. This successful mitigation of the trade-off between aerodynamic performance and noise level underscores the effectiveness of our bionic design approach.

Interventions for renal artery stenosis: Appraisal of novel physiological insights and procedural techniques to improve clinical outcome.

Randomized clinical trials failed to show additional benefit of renal artery stenting on top of medical therapy. Instead of writing an obituary on renal artery stenting, we try to explain these disappointing results. A transstenotic pressure gradient is needed to reduce renal perfusion and to activate the renin-angiotensin-aldosterone system. In only a minority of patients included in trials, a transstenotic pressure gradient is measured and reported. Like the coronary circulation, integration of physiological lesion assessment will allow to avoid stenting of non-significant lesions and select those patients that are most likely to benefit from renal artery stenting. Renal artery interventions are associated with peri-procedural complications. Contemporary techniques, including radial artery access, no-touch technique to engage the renal ostium and the use of embolic protection devices, will minimize procedural risk. Combining optimal patient selection and meticulous technique might lead to a netto clinical benefit when renal artery stenting is added to optimal medical therapy.

Hypersonic turbulent boundary layer over the windward side of a lifting body

In the present study, we performed direct numerical simulations for a hypersonic turbulent boundary layer over the windward side of a lifting body, the HyTRV model, at Mach number $6$ and attack angle 2 $^{\circ }$ to investigate the global and local turbulent features, and evaluate its difference from canonical turbulent boundary layers. By scrutinizing the instantaneous and averaged flow fields, we found that the transverse curvature on the windward side of the HyTRV model induces the transverse opposing pressure gradients that push the flow on both sides towards the windward symmetry plane, yielding significant effects of the azimuthal inhomogeneity and large-scale cross-stream circulations, moderate and azimuthal independent influences of adverse pressure gradient, and negligible impact of the mean flow three-dimensionality. Further inspecting the local turbulent statistics, we identified that the mean and fluctuating velocity become increasingly similar to the highly decelerated turbulent boundary layers over flat plates in that the mean velocity deficit is enhanced, and the outer layer Reynolds stresses are amplified as it approaches the windward symmetry plane, and prove to be self-similar under the scaling of Wei &amp; Knopp (J. Fluid Mech., vol. 958, 2023, A9) for adverse-pressure-gradient turbulent boundary layers. Conditionally averaged Reynolds stresses based on strong sweeping and ejection events demonstrated that the Kelvin–Helmholtz instability of the strong embedded shear layer induced by the large-scale cross-stream circulations is responsible for the turbulence amplification in the outer layer. The strong Reynolds analogy that relates the mean velocity and temperature was refined to incorporate the non-canonical effects, showing considerable improvements in the accuracy of such a formula. On the other hand, the temperature fluctuations are still transported passively, as indicated by their resemblance to the velocity. The conclusions obtained in the present study provide potentially profitable information for turbulent modelling modification for the accurate predictions of skin friction and wall heat transfer.

The pressure-derived microvascular resistance reserve and its correlation to Doppler MRR measurement-a proof of concept study.

Microvascular resistance reserve (MRR) is a recently introduced specific index of coronary microcirculation. MRR calculation can utilize parameters deriving from coronary flow reserve (CFR) assessment, provided that intracoronary pressure data are also available. The previously proposed pressure-bounded CFR (CFRpb) defines the possible CFR interval on the basis of resting and hyperemic pressure gradients in the epicardial vessel, however, its correlation to the Doppler wire measurement was reported to be rather poor without the correction for hydrostatic pressure. We aimed to determine the pressure-bounded coronary MRR interval with hydrostatic pressure correction according to the previously established equations of CFRpb adapted for the MRR concept. Furthermore, we also aimed to design a prediction model using the actual MRR value within the pressure-bounded interval and validate the results against the gold-standard Doppler wire technique. Hydrostatic pressure between the tip of the catheter and the sensor of the pressure wire was calculated by height difference measurement from a lateral angiographic view. In the derivation cohort the pressure-bounded MRR interval (between MRRpbmin and MRRpbmax) was determined solely from hydrostatic pressure-corrected intracoronary pressure data. The actual MRR was calculated by simple hemodynamic equations incorporating the anatomical data of the three-dimensionally reconstructed coronary artery (MRRp-3D). These results were analyzed by regression analyses to find relations between the MRRpb bounds and the actual MRRp-3D. In the derivation cohort of 23 measurements, linear regression analysis showed a tight relation between MRRpbmax and MRRp-3D (r 2 = 0.74, p < 0.0001). Using this relation (MRRp-3D = 1.04 + 0.51 × MRRpbmax), the linear prediction of the MRR was tested in the validation cohort of 19 measurements against the gold standard Doppler wire technique. A significant correlation was found between the linearly predicted and the measured values (r = 0.54, p = 0.01). If the area stenosis (AS%) was included to a quadratic prediction model, the correlation was improved (r = 0.63, p = 0.004). The MRR can be predicted reliably to assess microvascular function by our simple model. After the correction for hydrostatic pressure error, the pressure data during routine FFR measurement provides a simultaneous physiological assessment of the macro- and microvasculature.

Unfolding of shocked hydrodynamic instability at SF[formula omitted] elliptical interface: Physical insights from numerical simulations

The Richtmyer–Meshkov (RM) instability widely exists in variety of industrial and scientific applications, such as in inertial confinement fusion, astrophysics explosions, supersonic combustion, bubble dynamics and cavitation. This study investigates the unfolding physical phenomena of RM instability at SF6 elliptical bubbles using numerical simulations. In contrast to cylindrical bubble, both shocked horizontal/vertical-aligned elliptical bubbles with different aspect ratios are considered, emphasizing the aspect ratio effects on flow morphology, complex wave patterns, interface deformation, vorticity generation, and interface features. For this purpose, a two-dimensional system of compressible Navier–Stokes-Fourier equations for multicomponent flows are solved using by a mixed modal discontinuous Galerkin method. Numerical simulations illustrate that the aspect ratio of elliptical bubbles have a significant influence on the vortex dynamics and the associated RM instability flows in contrast to the cylindrical bubble. In horizontal-aligned elliptical bubbles, some additional complex waves pattern, including inward jet and secondary vortex rings are observed. While, in vertical-aligned elliptical bubbles, the interface between two primary vortex rings is always vertical and has a “hippocampus” appearance due to the enhancement of downstream velocity. The baroclinic vorticity due to misalignment of density and pressure gradients at interface affects the bubble deformation and induces the Kelvin–Helmholtz instability, which leads to turbulent mixing. It is observed that the complexity of the vorticity fields is enhanced with increasing aspect ratios. Further, these aspect ratio effects result in integral diagnostic of important spatially integrated fields, and various interface features.

Usage of high-fidelity large eddy simulation to improve the turbulence modeling of Reynolds averaged navier stokes simulation in film cooling applications via a neural network

In this study, high-Fidelity Large eddy simulation (LES) data was used to create a surrogate turbulence model to enhance the estimation of turbulent heat flux in a Reynolds averaged Navier Stokes (RANS) solver for film cooling applications. The LES simulation (A flat plate film cooling application with a Reynolds number of 17,382, a blowing ratio of 1 and a density ratio of 2) was validated by comparison with experimental data. A correlation analysis was performed to identify the most influential parameters, and temperature gradient, velocity gradient, turbulent dissipation rate, shear strain rate, and turbulent viscosity ratio were selected as the most effective parameters. A second model was developed to create a Galilean-invariant model that remains unaffected by changes in the coordinate system. Neural network was applied to the LES training data to propose a modified surrogate dynamic turbulent Prandtl number to be applied to the k − ε realizable RANS simulation. The first surrogate model was implemented to two different geometries, one geometry was a flat plate film cooling similar to the training data but with different flow conditions, and another one was a more complex geometry with pressure gradient. The second model was only implemented on the second geometry and produced similar results. The surrogate models predicted a more accurate thermal field near the cooling wall (up-to 58 % error reduction) with a computational time complexity similar to the base RANS solver.

Large-Eddy Simulations of Flow over a Backward-Facing Ramp with a Wall-Mounted Cube

Passive flow control devices, such as vortex generators (VGs), can effectively modulate the turbulent boundary layer flow near regions of adverse pressure gradients, but the interactions between the salient flow structures produced by VGs and those of the separated flow are not fully understood. In this study, a spatially evolving turbulent boundary layer interacting with a wall-mounted cube ahead of a backward-facing ramp is investigated using wall-resolved large-eddy simulations for a Reynolds number of 19,600, based on the inlet boundary layer thickness and freestream velocity. Different cube configurations are examined to isolate the effects of cube height and streamwise position. The large counter-rotating flow produced by the larger cubes generated more turbulent kinetic energy, thereby resulting in smaller separated regions over the ramp. Although significantly lower levels of turbulent kinetic energy dissipation than production are observed in the outer flow regions of the horseshoe vortex and in the induced counter-rotating flow, the spatial distribution of dissipation is similar to that of the turbulent kinetic energy. When the upstream position of an isolated single cube, relative to the leading ramp edge, is more than three cube heights, the streamwise decay of the counter-rotating flow results in lower levels of turbulent kinetic energy.

A triboelectric nanogenerator based on a spiral rotating shaft for efficient marine energy harvesting of the hydrostatic pressure differential

Equipment used in underwater sensing and exploration typically relies on cables or batteries for energy supply, resulting in a limited and inconvenient energy supply and marine environmental pollution that hinder the sustainable development of distributed ocean sensing networks. Here, we design a deep-sea differential-pressure triboelectric nanogenerator (DP-TENG) based on a spiral shaft drive using modified polymer materials to harness the hydrostatic pressure gradient energy at varying ocean depths to power underwater equipment. The spiral shaft structure converts a single compression into multiple rotations of the TENG rotor, achieving efficient conversion of differential pressure energy. The multi-pair electrode design enables the DP-TENG to generate a peak current of 61.7 μA, the instantaneous current density can reach 0.69 μA cm−2, and the output performance can be improved by optimizing the spiral angle of the shaft. The DP-TENG can charge a 33 μF capacitor to 17.5 V within five working cycles. It can also power a digital calculator and light up 116 commercial power light-emitting diodes, demonstrating excellent output capability. With its simple structure, low production cost, and small form factor, the DP-TENG can be seamlessly integrated with underwater vehicles. The results hold broad prospects for underwater blue energy harvesting and are expected to contribute to the development of self-powered equipment toward emerging “smart ocean” and blue economy applications.

Threshold pressure gradient in fractured reservoirs: Experimental simulation and mathematical modeling

Aiming to solve the problems of unclear fluid flow laws and controlling factors in fractured reservoirs, as well as the lack of a mathematical model of threshold pressure gradient (TPG) considering fracture structural parameters, research on the structural characterization of fractured reservoirs, physical simulation of fluid flow, and TPG prediction models has been carried out. Physical simulations demonstrate that fluid flow in fractured reservoirs under stress is nonlinear and exhibits TPG. The TPG displays a significant positive exponential relationship with confining pressure and water saturation. As the confining pressure or water saturation increases, the effective opening of fractures decreases. The TPG will increase dramatically when the fracture opening decreases to the critical thickness for the rapid increase in TPG. On the basis of the fluid flow law study, the TPG fractal prediction model is further developed based on fractal dimension of fracture length distribution (Df), fractal dimension of tortuosity (DT), water saturation (Sw), maximum fracture width (wmax), limit shear stress (η0), and sample characteristic length (L0). The results predicted by the model show good agreement with physical simulations (with average relative error of 7.56%). Experimental simulation and mathematical modeling of TPG in fractured reservoirs can reveal the fluid flow mechanism and improve the accurate evaluation of production capacity during different development processes.

Comparison of Fluid Dynamics of Different Flow Geometries in an Iron Flow Battery Prototype

Introduction: Renewable energy sources demand is increasing in the world due to their less environmental effect. Solar and wind energy, which requires largescale electrical energy storage, are major contributors to this growth. The iron flow battery is one of the Redox flow battery technologies, which is encouraging for electrical energy storage because of their long lifetime, flexibility to increase storage, and minimum chemical hazard compared to conventional batteries Method: In this research, the engineering design and fabrication of a locally made Iron flow battery prototype is described. Then, electrolyte flow simulation was carried out through COMSOL Multiphysics to compare the fluid velocity and pressure profiles in three different flow geometries such as plain, parallel, and serpentine, to select the most compatible flow pattern for the Iron flow battery. Result: The resulting velocity profiles indicated that plain flow had stagnated points, the parallel flow had uneven velocity distribution, and serpentine flow had a uniform and high-velocity profile. The simulation results of pressure profiles showed the serpentine, parallel, and plain flows had inlet pressures of 34.38 Pa, 10.01 Pa, and 0.254 Pa, respectively. Conclusion: Given that pumping power is directly proportional to the pressure gradient, the power requirement of electrolyte pumps from highest to lowest is as serpentine flow, parallel flow, and plain flow.

An innovative modification to the Menter shear-stress transport turbulence model employing the symbolic regression approach

Drawing from the non-equilibrium link between the production Pk and dissipation ε of turbulent kinetic energy (TKE), we advocate for the introduction of a limiter to modulate the TKE production term within the Menter shear-stress transport (SST) model. The original SST model is made more sensitive to the adverse pressure gradient (APG) by Bradshaw's assumption. Bradshaw's assumption introduces the equilibrium condition Pk/ε = 1 in most regions of the turbulent boundary layer. In the APG flows with Pk≫ε, the equilibrium condition suppresses the magnitude of TKE (k) within the boundary layer, resulting in an early separation problem. To address this issue, we employ the symbolic regression (SR) to scrutinize the physical correlation between Pk/ε and local turbulence parameters, obtaining an approximate function FSR that encapsulates the relationship between Pk/ε, Sk/ε, and y+ in the APG flow. Following its incorporation into the original SST model in the form of a limiter, the FSR evolves into the SST-Symbolic Regression Evolution model. The SST-SRE is then applied to four cases with APGs. The modification leads to an increase in the skin-friction coefficient Cf in the APGs region and causes a downstream shift in the separation location, improving the consistency with high-accuracy data and experimental results. It is demonstrated that this correction can improve the early separation problem in the Menter SST turbulence model.

Exploring the Aerodynamic Effect of Blade Gap Size via a Transient Simulation of a Four-Stage Turbine

With the impact of size on low-pressure turbines (LPTs) increasing, the gap between the blades has shrunk, inevitably influencing the unsteady effects inside the turbine. In this study, the aerodynamic effect of the blade gap size is investigated using a compressible unsteady Reynolds-averaged Navier–Stokes (URANS) model on the basis of a four-stage LPT. Simulations are conducted in which the gap between the third-stage stator (S3) and rotor (R3) varies from 0.2 to 0.8 times the axial chord length of the R3 blade. The multi-stage environment reflects the complexity of real low-Reynolds flow fields. Computational fluid dynamics is used to analyze the flow field in detail. The results demonstrate that in the small-gap (AG-0.2) case, the turbulence kinetic energy (TKE) level of the S3 wake close to the R3 leading edge is four-thirds of that in the large-gap (AG-0.8) case. The higher intensity of the wake impacting on the blade results in a higher inverse pressure gradient in the rear part of the R3 suction surface, which increases the profile loss. However, the AG-0.2 case leads to fewer losses caused by the passage vortex in the hub area under the influence of the higher intensity of the wake.