Wall Curvature Research Articles

A High-Fidelity Computational Model for Predicting Blood Cell Trafficking and 3D Capillary Hemodynamics in Retinal Microvascular Networks.

To present a first principle-based, high-fidelity computational model for predicting full three-dimensional (3D) and time-resolved retinal microvascular hemodynamics taking into consideration the flow and deformation of individual blood cells. The computational model is a 3D fluid-structure interaction model based on combined finite volume/finite element/immersed-boundary methods. Three in silico microvascular networks are built from high-resolution in vivo motion contrast images of the superficial capillary plexus in the parafoveal region of the human retina. The maximum tissue area represented in the model is approximately 500 × 500 µm2, and vessel lumen diameters ranged from 5.5 to 25 µm covering capillaries, arterioles, and venules. Blood is modeled as a suspension of individual blood cells, namely, erythrocytes (RBC), leukocytes (WBC), and platelets in plasma. An accurate and detailed biophysical modeling of each blood cell and their flow-induced deformation is considered. A physiological, pulsatile boundary condition corresponding to an average cardiac cycle of 0.9 second is used. Detailed quantitative data and analysis of 3D retinal microvascular hemodynamics are presented, and their relationship to RBC flow dynamics is illustrated. Blood velocity is shown to have temporal oscillations superimposed on the background pulsatile variation, which arise because of the way RBCs partition at vascular junctions, causing repeated clogging and unclogging of vessels. Temporal variations in RBC velocity and hematocrit are anti-correlated in a given vessel, but their time-averaged distributions are positively correlated across the network. Whole blood velocity is 65% to 85% of RBC velocity, with the discrepancy related to the formation of an RBC-free region, adjacent to the vascular endothelium and typically 0.8 to 1.8 µm thick. The 3D velocity and RBC concentration profiles are shown to be oppositely skewed with respect to each other, because of the way that RBCs "hug" the apex of each bifurcation. RBC deformation is predicted to have biphasic behavior with respect to vessel diameter, with minimal cell length for vessels approximately 7 µm in diameter. The wall shear stress (WSS) exhibits a strongly 3D distribution with local regions of high value and gradient spanning a range of 10 to 80 dyn/cm2. WSS is highest where there is faster flow, greater curvature of the vessel wall, capillary bifurcations, and at locations of RBC crowding and associated thinning of the cell-free layer. This study highlights the usefulness of high-fidelity cell-resolved modeling to obtain accurate and detailed 3D, time-resolved retinal hemodynamic parameters that are not readily available through noninvasive imaging approaches. The results presented are expected to complement and enhance the interpretation of in vivo data, as well as open new avenues to study retinal hemodynamics in health and disease.

Influence of parameter variation and interlayer temperature control in wall angle, curvature and measurement methodology of ER70S-6 parts obtained by WAAM

Wire and Arc Additive Manufacturing is characterized for the high deposition rates, enabling the manufacturing of big, complex parts, with smaller relative production cost. However, once the part receives high heat inputs, leading to geometry variation and deformations, it is important to properly measure the part characteristics. Therefore, this work contributes with a measurement methodology for inclined walls deposited by Wire and Arc Additive Manufacturing and its application on walls deposited with different parameters. The main parameter of influence was the use of interlayer temperature control, which increased the angle in 71.0%, and the curvature in 90.3%, lower part.

Left ventricular absolute myocardial work measured by cardiovascular magnetic resonance: a proof-of-concept

Abstract Background Myocardial Work Index (MWI) is a load-independent and non-invasive method for assessing cardiac systolic function [1]. However, MWI does not directly measure absolute myocardial work (AMW), since it does not consider the effect of variations in left ventricular (LV) wall thickness and regional wall curvature. Therefore, a direct comparison of MWI results may be difficult. Cardiovascular magnetic resonance (CMR) is the gold standard for assessing the LV geometry and therefore can be used to directly measure the AMW by calculating the area of the stress-strain curve. Purpose This study aims to measure and compare CMR-based AMW in three groups with different work profiles: healthy subjects, patients with ST-elevation myocardial infarction (STEMI), and patients with severe aortic valve stenosis (AS). Additionally, it aims to compare AMW with strain to provide additional insights into remodelling. Methods A total of 78 participants were included in our study; 38 healthy subjects from the CENS study [2], 19 STEMI patients 3-7 days post-PCI from the ASSAIL study [3], and 21 patients with AS scheduled for operation. Collected data were not adjusted for age or sex. Stress was estimated using Laplace’s equation [4]. Intra-ventricular pressure was calculated from brachial cuff pressure as previously described [5]. Mid-ventricular circumferential strain was calculated using CMR-based tissue phase mapping [4]. AMW was calculated both as Myocardial Work per unit endocardial Surface (MWS, in J/m^2) and per unit Mass (MWM, in mJ/g), both serving as measurements of global circumferential systolic function. Results Mean circumferential strain did not differ significantly between the AS and the healthy groups (p=0.37), but it was significantly lower in the STEMI group compared to the healthy group (p<0.001). MWS was significantly higher in the AS group (p<0.001) and lower in the STEMI group (p<0.001) compared the healthy group. This suggests that each unit of endocardial surface in the myocardium performed, on average, more work in the AS group and less work in the STEMI group relative to the healthy group. MWM was not significantly different between the AS and the healthy group (p=0.74), while in the STEMI group, it was significantly lower (p=0.001) than in healthy subjects. Conclusion Our results indicate that in patients with AS, the myocardium did more work per unit surface, while each gram of the myocardium did the same amount of work. This is likely due to concentric hypertrophy and the increase of afterload. In contrast, in patients with STEMI, the myocardium did, on average, less work per unit surface and per mass. This is expected due to the direct loss of mechanical function in the infarcted myocardium. Our results indicate that AMW enhances traditional strain analysis, improves myocardial function evaluation, and may provide deeper insight into myocardial remodeling in diverse cardiac conditions.

Sella turcica and facial bones: Morphological integration in the human fetal cranium.

The cranial base plays a significant role in facial growth, and closer analyses of the morphological relationship between these two regions are needed to understand the morphogenesis of the face. Here, we aimed to study morphological integration between the sella turcica (ST) and facial bones during the fetal period using geometric morphometrics. Magnetic resonance images of 47 human fetuses in the Kyoto Collection, with crown-rump lengths of 29.8-225 mm, were included in this study. Anatomical homologous landmarks and semilandmarks were registered on the facial bones and the midsagittal contour of the ST, respectively. The shape variations in the craniofacial skeleton and the ST were statistically investigated by reducing dimensionality using principal component analysis (PCA). Subsequently, the morphological integration between the facial bones and ST was investigated using two-block partial least squares (2B-PLS) analysis. PCA showed that small specimens represented the concave facial profile, including the mandibular protrusion and maxillary retrusion. The 2B-PLS showed a strong integration (RV coefficient = 0.523, r = .79, p < .01) between the facial bones and ST. The curvature of the anterior wall of the ST was highly associated with immature facial morphology characterized by a concave profile. The strong integration between the two regions suggested that the anterior ST may be associated with facial morphology. This result quantitatively confirms previous studies reporting ST deformities in facial anomalies and induces further research using postnatal subjects.

A novel laser interferometric method for thin film thickness measurement in gas–liquid intermittent flow

Abstract In horizontal intermittent flow, the long bubbles move toward the center of the pipe due to inertia, forming the thin liquid film above the long bubbles. Accurate measurement of the liquid film thickness is crucial for heat and mass transfer. In this paper, laser interferometric technology is innovatively introduced to measure the film thickness of the intermittent flow, and the thin liquid film is detected with a resolution of 100 nm. Considering the curvature of the circular pipe wall, which leads to divergent reflected light, the effect of the pipe wall on the interference pattern is explored by the ray tracing technique. A two-dimensional interpolation phase retrieval algorithm based on light intensity is proposed to reconstruct the thickness of the liquid film, and the average error is less than 1.86%. Benefiting from the exceptionally high resolution, research is conducted on the thin liquid film at the top of the horizontal intermittent flow, revealing its dependence on the sub-regimes and gas–liquid velocities.

Locomotion analysis of a crawling wave robot in circular canal

In this paper, we analyze the locomotion of a wave robot crawling in a curved canal between rigid walls. We determine the conditions for crawling, considering the robot geometry, orientation, wall curvature, canal width, and friction coefficients. Initially, we present an analytical model of the different cases of crawling and conditions for advancement. We found four cases of crawling: one where the robot touches only the outer wall, two with one contact point each on the outer and inner walls, and a third where the robot has two contact points with the outer wall and one with the inner wall. Subsequently, we introduce a multibody numerical simulation, which accounts for sliding along the wall and over the ground surface. The simulation allows one to validate our analytical results and analyze the robot's behavior under different conditions. Finally, we present validating results of multiple experiments conducted with our SAW robot. This analysis encompasses all types of crawling robots with internal thrust mechanisms that are not based on contact with the side walls of the pipe or canal.

Clip-and-snare method with a pre-looping technique versus conventional method in the treatment of precancerous lesion and early gastric cancer: a retrospective study

BackgroundLow grade intraepithelial neoplasia (LGIN) and high grade intraepithelial neoplasia (HGIN) are potential precancerous lesion of gastric neoplasms. Endoscopic submucosal dissection (ESD) is the first option for the treatment of precancerous lesion and early gastric cancer (EGC). Traction is an effective method to improve efficiency, and reduce complications during ESD. In this study, we shared a useful traction method using the clip-and-snare method with a pre-looping technique (CSM-PLT) for precancerous lesion and EGC.MethodsWe retrospectively analyzed patients received ESD combined with CSM-PLT or conventional ESD from June 2018 to December 2021 in Shenzhen People’s hospital. The primary outcome was resection speed.ResultsForty-two patients were enrolled in ESD combined with CSM-PLT group and sixty-five patients in conventional ESD group respectively. Baseline characteristics were comparable among two groups (P>0.05). There were no significant differences in terms of R0 resection rate, en bloc resection rate (97.6% vs. 98.5%, P = 1.000 and 97.6% vs. 96.9%, P = 1.000, respectively), operation costs (933.7 (644.1-1102.4) dollars vs. 814.7 (614.6-988.3) dollars, P = 0.107), and hospital stays (8.0 ± 3.1 days vs. 7.3 ± 3.2 days, P = 0.236). In addition, no significant difference was observed with respect to complications (P>0.05). However, the resection speed of ESD combined with CSM-PLT was faster than that of conventional ESD (11.3 (9.4–14.9) mm2/min vs. 8.0 (5.8–10.9) mm2/min, P < 0.001), particularly lesions located in anterior wall and lesser curvature. In addition, the association between ESD combined with CSM-PLT and resection speed was still supported after propensity matching scores (PMS).ConclusionsCSM-PLT can help to improve ESD efficiency without reducing the en bloc resection rate or increasing the incidence of complications.

Direct Numerical Simulation Database of High-Speed Flow over Parameterized Curved Walls

This study presents a direct numerical simulation (DNS) database of high-speed turbulent boundary layers (TBLs) subject to pressure gradients due to parametrically varied backward-facing and forward-facing wall curvatures, with an inflow Mach number of 4.9 and a friction Reynolds number of Reτ≃1000 immediately before the onset of wall curvature. The Mach and Reynolds numbers are significantly higher than those reported in the literature for the DNS of pressure-gradient TBLs. The flow conditions and baseline wall geometries are representative of experiments in the high-speed blowdown wind tunnel at the National Aerothermochemistry Laboratory at Texas A&M University. The wall steepness of the baseline geometry for both the backward-facing and forward-facing walls was systematically varied to cause attached, incipiently separated, and fully separated flows. Precomputed flow statistics, including turbulent kinetic energy budgets, are available on the website of the Turbulence Modeling Resource of the NASA Langley Research Center, allowing other investigators to query any property of interest.

Influence of wall curvature on evolution of converged flow generated by crossing shock wave/boundary layer interaction: An experimental study

The curved surfaces widely exist in three-dimensional inward-turning inlets and variable sectional isolators, which determine the downstream evolution of the converged flow generated by the crossing shock wave/boundary layer interaction, thereby affecting the start performance and combustion efficiency of the hypersonic vehicles. In this work, the converged flow subjected to the curved surfaces is experimentally studied with the nanoparticle-based planar laser scattering method and particle image velocimetry. Results show that the velocity profiles of the converged flow on the transverse plane can be normalized at different angles. The upstream separation size is found to be decreased by the downstream convex surface due to the reduction of backpressure, especially in large-radius cases, whereas the converged flow gradually becomes smooth ought to the dependence of the acceleration effect on the velocity. The concave surface shows an opposite effect on the converged flow, which further indicates that a downstream convex surface is preferred for hypersonic inlets to weakens the flow non-uniformity to improve the inlet performance.

Effect of wall curvature on heat transfer and hydrodynamics in a ribbed cooling passage

Simplified rectangular ribbed cooling passages with a flat wall are extensively considered in exploring the internal cooling features of turbine blades, but the realistic blade has a twisted shape inherently. The effects induced by the curved wall have not been clarified in detail. In this work, adopting a verified v2f turbulence model, numerical investigations are completed to evaluate the effects of the curved wall on the internal cooling characteristics of a ribbed channel. Adopting the unified ribbed channel, flat, convex, and concave walls with distinct curvatures are comprehensively evaluated and compared in a wide Re range for the turbulent flow and heat transfer features as well as the flow and thermal performance. It is found that using the flat wall, ribs can typically induce recirculation vortices having a two-dimensional nature. In contrast, the curved wall significantly contributes to the counter-rotating vortex pairs on the spanwise plane. Combined with recirculation vortices offered by the ribs, the turbulent flow of the cooling channel with the curved wall has a remarkable three-dimensional feature. Hence, the turbulent activity and fluid mixing are enhanced greatly along with the raised heat transfer enhancement and friction loss. Particularly, the convex wall with a curvature of K = 4 provides 28.6 % higher heat transfer performance (Nu/Nu0) but 88.4 % higher resistance (f/f0) than the flat wall. Considering the overall cooling performance, the concave wall with a relatively small curvature is suggested with an improvement of up to 32.8 % concerning the factor (Nu/Nu0)/(f/f0) and 9.5 % on (Nu/Nu0)/(f/f0)1/3. Finally, it is highlighted that considering the effect of the wall curvature, the current study stimulates the mechanistic understanding and provides a design guideline for high-performance blade internal cooling.

Global Surface Pressure Pattern for a Compressible Elliptical Cavity Flow Using Pressure-Sensitive Paint

The flow field in a cavity depends on the properties of the upstream boundary layer and the cavity geometry. Comprehensive studies for rectangular cavities have been conducted. This experimental study determines the global surface pressure pattern for elliptical cavities (eccentricities of 0, 0.66 and 0.87) in a naturally developed turbulent boundary layer using pressure-sensitive paint. The ratio between the length (major axis) and the depth is 4.43–21.5, and the freestream Mach number is 0.83. The mean surface pressure distribution of an elliptical cavity resembles that of a rectangular cavity. A change in the value of eccentricity (wall curvature) affects the region for an adverse pressure gradient in an open cavity, an extension of the plateau in a transitional–closed cavity and flow expansion near the front and rear edges. The boundaries between an open, transitional and closed cavities vary.

Viscoelastic circular cell honeycomb helmet liners for reducing head rotation and brain strain in oblique impacts

Rotational head motion is one of the major contributors to brain tissue strain during head impacts, which damages axons and vessels and leads to traumatic brain injury. Helmet technologies have come to market promising enhanced protection against such rotational head motion. We recently introduced novel air-filled viscoelastic cell arrays and showed that their shear response under oblique impacts can be tailored through altering the cell wall curvature. We found that concave cells provide shear stiffness that is a few folds larger than that of convex cells. Here we test whether altering the cell curvature can reduce head rotational kinematics and brain strain and whether the viscoelastic cell arrays outperform the reference EPS foam-based liner. To test these hypotheses, we incorporate the viscoelastic cell arrays in a bicycle helmet liner. We use validated finite element models of the helmet and replace the liner with validated finite element models of the cellular cell arrays. We simulate oblique impacts at different locations to represent a wide range of real-world bicycle head impacts. In all cases, the head kinematics and brain deformation metrics indicate significant improvements with the novel cell arrays over the conventional EPS liner. We show that the shear-compliant cell arrays can reduce head rotational acceleration by as much as 64 % and brain strain by 69 %, but not in all impact locations. Cell arrays with similar axial stiffness yet lower shear stiffness often bottomed out, indicating that a considerable amount of energy is dissipated via cell shearing around the impact zone. Our results show that placement of cells with varying amounts of shear stiffness should be optimised, with the most shear-compliant cells near the crown and the least near the temples. This study shows the promising performance of viscoelastic cell arrays in protecting the head and brain under oblique impacts and provides avenues for optimising the distribution of their compressive-shear properties.

Design and analysis of a wall-climbing robot with passive compliant mechanisms to adapt variable curvatures walls

AbstractMotivated by practical applications of inspection and maintenance, we have developed a wall-climbing robot with passive compliant mechanisms that can autonomously adapt to curved surfaces. At first, this paper presents two failure modes of the traditional wall-climbing robot on the variable curvature wall surface and further introduces the designed passive compliant wall-climbing robot in detail. Then, the motion mechanism of the passive compliant wall-climbing robot on the curved surface is analyzed from stable adsorption conditions, parameter design process, and force analysis. At last, a series of experiments have been carried out on load capability and curved surface adaptability based on a developed principle prototype. The experimental results indicated that the wall-climbing robot with passive compliant mechanisms can effectively promote both adsorption stability and adaptability to variable curvatures.

Radial clearance influence on strain and stress distribution of the polygonal shape deep-drawing operation

In the existing research, polygonal -shaped dies were manufactured based on the dimensions of the design. These dies were then assembled on the deep-drawing device to create polygonal cups (specifically heptagonal cups) for conducting experimental work tests. The process was achieved via a deep-drawing operation to create heptagonal cups with dimensions (diameter D = 40mm and height L = 31.5 mm). For both experimental work and finite element analysis, the cups of heptagonal shapes were formed from flat circular blanks of Low Carbon Steel (thickness to = 0.7 mm) and diameter D = 80mm. A commercial software program, ANSYS, was employed to perform this finite element analysis. The research aims to study the effect of different radial clearance ( RC = 1.1 to,1.2 to, and 1.3 to) between die and punch for heptagonal shape DD operations on the forming load, the height of the cup, thickness distribution, strain and stress distribution along the cup wall (side-wall and wall curvature). The analysis outcomes indicate that the maximum forming force was 51.250 kN with the wall curvature, the maximum effective strain was 0.8231, and the maximum stress was 676 MPa when the [Formula: see text]1.1 to). Additionally, the squeezing process in the mug wall occurred with [Formula: see text]1.1 to).

Fracture Morphology Influencing Supersonic CO2 Transport: Application in Geologic CO2 Sequestration

AbstractGeologic carbon sequestration requires CO2 injection into the storage formation at high‐injecting pressure. Such high pressure could induce choked flow accompanying huge variations in thermodynamic properties of CO2 at a converging‐diverging (CD) fractures in the storage formation. In this study, high‐velocity CO2 transport through CD fractures was investigated to quantify the effect of fracture morphology on occurrence of both choked flow and shockwave that constrain the mass flow rate of fluid. In addition, variations in thermodynamic CO2 properties including Mach Number (Ma), defined by the ratio of fluid velocity to sound speed, and shock properties were investigated. The morphological characteristics of CD fractures were determined by nine properties, such as throat diameter, throat length, inlet diameter, outlet diameter, throat diameters of two‐connected CD fractures, fracture wall curvature, roughness amplitude, and frequency. As a result, the throat diameter crucially affected choked flow occurrence and maximum Ma. When the inlet and outlet diameters varied, the profiles for Ma variation were consistent in the converging and diverging segments, respectively. In addition, regardless of change in the throat length, the position of maximum Ma was nearly constant with showing the position length ratio of 0.13–0.14. However, roughness of fracture wall significantly influenced the Ma variation and occurrence of shock. In particular, backflows segregated from the main CO2 flow were observed near the wall roughness.

Effects of heater positions on magneto-hydrodynamic convection of CuO-water nanofluid flow in a grooved channel

PurposeThis study aims to delve into the coupled mixed convective heat transport process within a grooved channel cavity using CuO-water nanofluid and an inclined magnetic field. The cavity undergoes isothermal heating from the bottom, with variations in the positions of heated walls across the grooved channel. The aim is to assess the impact of heater positions on thermal performance and identify the most effective configuration.Design/methodology/approachNumerical solutions to the evolved transport equations are obtained using a finite volume method-based indigenous solver. The dimensionless parameters of Reynolds number (1 ≤ Re ≤ 500), Richardson number (0.1 ≤ Ri ≤ 100), Hartmann number (0 ≤ Ha ≤ 70) and magnetic field inclination angle (0° ≤ γ ≤ 180°) are considered. The solved variables generate both local and global variables after discretization using the semi-implicit method for pressure linked equations algorithm on nonuniform grids.FindingsThe study reveals that optimal heat transfer occurs when the heater is positioned at the right corner of the grooved cavity. Heat transfer augmentation ranges from 0.5% to 168.53% for Re = 50 to 300 compared to the bottom-heated case. The magnetic field’s orientation significantly influences the average heat transfer, initially rising and then declining with increasing inclination angle. Overall, this analysis underscores the effectiveness of heater positions in achieving superior thermal performance in a grooved channel cavity.Research limitations/implicationsThis concept can be extended to explore enhanced thermal performance under various thermal boundary conditions, considering wall curvature effects, different geometry orientations and the presence of porous structures, either numerically or experimentally.Practical implicationsThe findings are applicable across diverse fields, including biomedical systems, heat exchanging devices, electronic cooling systems, food processing, drying processes, crystallization, mixing processes and beyond.Originality/valueThis work provides a novel exploration of CuO-water nanofluid flow in mixed convection within a grooved channel cavity under the influence of an inclined magnetic field. The influence of different heater positions on thermomagnetic convection in such a cavity has not been extensively investigated before, contributing to the originality and value of this research.

Magneto-nanofluidic thermal transport and irreversibility in semicircular systems with heated wavy bottom under constant fluid volume and cooling surface constraints

PurposeThis study aims to investigate the influence of wall curvature in a semicircular thermal annular system on magneto-nanofluidic flow, heat transfer and entropy generation. The analysis is conducted under constant cooling surface and fluid volume constraints.Design/methodology/approachThe mathematical equations describing the thermo-fluid flow in the semicircular system are solved using the finite element technique. Four different heating wall configurations are considered, varying the undulation numbers of the heated wall. Parametric variations of bottom wall undulation (f), buoyancy force characterized by the Rayleigh number (Ra), magnetic field strength represented by the Hartmann number (Ha) and inclination of the magnetic field (γ) on the overall thermal performance are studied extensively.FindingsThis study reveals that the fluid circulation strength is maximum in the case of a flat bottom wall. The analysis shows that the bottom wall contour and other control parameters significantly influence fluid flow, entropy production and heat transfer. The modified heated wall with a single undulation exhibits the highest entropy production and thermal convection, leading to a heat transfer enhancement of up to 21.85% compared to a flat bottom. The magnetic field intensity and orientation have a significant effect on heat transfer and irreversibility production.Research limitations/implicationsFurther research can explore a wider range of parameter values, alternative heating wall profiles and boundary conditions to expand the understanding of magneto-nanofluidic flow in semicircular thermal systems.Originality/valueThis study introduces a constraint-based analysis of magneto-nanofluidic thermal behavior in a complex semicircular thermal system, providing insights into the impact of wall curvature on heat transfer performance. The findings contribute to the design and optimization of thermal systems in various applications.

VISUALIZATION OF TURBULENT EVENTS VIA VIRTUAL/AUGMENTED REALITY

Mixed reality technology, i.e., virtual (VR) and augmented (AR) reality, has spread from research laboratories to enter the homes of many. Further, the widespread adoption of these technologies has caught the scientific community's attention, which is constantly researching potential applications. Backed by the continued enhancement of high-performance computing in hardware and software, we are applying mixed reality technologies as a scientific visualization tool for fluid dynamics purposes. In particular, we show a virtual wind tunnel (along with the simplified methodology to replicate it) that enables the user to visualize complex and intricate turbulent flow patterns within an immersive environment. Briefly, high spatial/temporal resolution numerical data over supersonic turbulent boundary layers subject to concave and convex wall curvature has been creatively "pipelined" for VR/AR visualization via several scripts, software, and apps, which are further explained and described along the manuscript. The intention is to present a technique of how to visualize fluid flows to be the most convenient for the user, especially if one is slightly unfamiliar with scientific visualization. Whereas VR/AR applications are principally discussed here for flow visualization, the lessons learned can be certainly extended to other disciplines involving three-dimensional time-dependent databases.

Flow evolution of mixed layer on convex curvature wall under hypersonic conditions

With the continuous upgrading of hypersonic vehicles, a new requirement for designing imaging window i.e. conformal window for improving aerodynamic characteristics, is put forward, in which the supersonic cooling film and optical window are required to maintain the same curvature shape as the aircraft body. In this work, the mixed-layer flow evolution on a convex wall (CV) is investigated. A nanoparticle-based planar laser scattering technique is used to design the flow field structure of the mixed layer in &lt;i&gt;Ma&lt;/i&gt; = 6 hypersonic static wind tunnel, and the location of the mixed-layer instability is studied by combing fractal dimension. The results of pressure, and impulse of compression (&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;p&lt;/sub&gt;) evolution along the flow direction are obtained by numerical simulation, showing that the total incoming pressure (&lt;i&gt;P&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt;) has a significant effect on the flow evolution of the mixed layer: as &lt;i&gt;P&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt; increases, the ratio of static pressure (RSP) decreases, that the position of the mixed-layer instability is delayed, and that the flow velocity of the typical vortex structure increases. The favorable gradient existing at the CV wallleads the pressure to drop along the flow direction, and the pressure is enhanced when the supersonic air film along the tangential direction of the wall is under the operating condition. However, as &lt;i&gt;P&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt; increases, the RSP decreases, and the lifting effect of the pressure on the CV decreases. The flow field is affected by the expansion effect of the CV, and &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;p&lt;/sub&gt; decreases along the flow direction. The supersonic air film can weaken the expansion effect on the CV and thus suppressing the decrease of &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;p&lt;/sub&gt;. The change rate of &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;p&lt;/sub&gt; (Δ&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;p&lt;/sub&gt;) is significantly affected by &lt;i&gt;P&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt;, in a range of bending impulse |&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;&lt;i&gt;Φ&lt;/i&gt;&lt;/sub&gt;| = 0.191–3.62, Δ&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;p&lt;/sub&gt; decreases from 178.67% to 12.02% when &lt;i&gt;P&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt; = 0.5 MPa, and Δ&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;p&lt;/sub&gt; decreases from 40.38% to 5.64% when &lt;i&gt;P&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt; = 1.0 MPa. Δ&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;p&lt;/sub&gt; decreases as |&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;&lt;i&gt;Φ&lt;/i&gt;&lt;/sub&gt;| increases, but the decrease becomes less as &lt;i&gt;P&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt; increases. The results reveal the flow evolution law of hypersonic mixed layer under the influence of convex curvature, and provide a certain reference for designing the shape of hypersonic vehicle to achieve aerodynamic drag reduction and thermal protection characteristics.

Comparative study of film cooling performance on curved walls with various hole configurations and blowing ratios

In order to increase turbine efficiency and prevent metal materials from being corroded by high temperatures, one of the great important methods for turbine blade cooling is film cooling. This work explores numerically the effects of various curvature wall on film cooling performance, and the effects of three different hole structures and four various blowing ratios (0.25,0.5,1,1.5) were discussed. Results show that the film cooling effectiveness values of the various configurations (cylindrical hole, shaped-hole, trenched shaped-hole) on the convex wall are 112%, 76%, and 50% higher than that on the concave wall respectively when the blowing ratio is 0.25, which indicates convex wall exhibits a greater potential to release the cooling effects of the jet holes compared with the concave wall and flat wall. Moreover, trenched shaped-holes provide a more uniform protection for wall, especially in terms of the coverage area in the spanwise direction. At the ends of the xs/D = 5 line, the cooling performance of trenched shaped-holes are locally 1320% and 1610% higher than cylindrical holes and shaped-holes, respectively. Additionally, when the blowing ratio is high, compared to curved walls, trenched shaped-holes have the most significant effect on improving the film cooling of flat wall surfaces.