Conventional Tip Research Articles

Does the Transillumination Technique Using a Diagnostic White Tip Influence the Degree of Conversion of the Infiltrant Resin? A Case Report With InVitro Insights: A New Technique to Improve the Predictability During the Application of Resin Infiltration: Transillumination Using a Diagnostic White Tip.

This study aimed to evaluate, through a case report combined with invitro study, whether a new diagnostic white tip for the transillumination technique during resin infiltration influences the procedure and degree of conversion (DC). A clinical case report demonstrated resin infiltration using the transillumination technique with a new white diagnostic tip (Radii Xpert LED diagnostic tip, SDI, Bayswater, VIC, AU) along with a light-curing device to enhance aesthetic results. An invitro study assessed the DC of two diagnostic white tips (Radii Xpert LED diagnostic tip [SDI, Bayswater, VIC, AU] and Valo Grand White Light Lens [Ultradent Prod., South Jordan, UT, USA]) compared to that achieved using conventional tips of both light-curing devices. Statistical analysis was performed using two-way ANOVA and Tukey's test (α = 0.05). The clinical case achieved complete masking of the white spot lesion. Invitro, the diagnostic white tips exhibited significantly lower DC values compared to conventional tips (p = 0.001), regardless of the light-curing unit. The diagnostic white tip used in the transillumination technique improves resin infiltration visibility without compromising the degree of conversion. The transillumination technique with the diagnostic white tip enables monitoring of resin infiltration while maintaining effective polymerization.

An adaptive acceleration scheme for phase-field fatigue computations

Abstract Phase-field models of fatigue are capable of reproducing the main phenomenology of fatigue behavior. However, phase-field computations in the high-cycle fatigue regime are prohibitively expensive due to the need to resolve spatially the small length scale inherent to phase-field models and temporally the loading history for several millions of cycles. As a remedy, we propose a fully adaptive acceleration scheme based on the cycle jump technique, where the cycle-by-cycle resolution of an appropriately determined number of cycles is skipped while predicting the local system evolution during the jump. The novelty of our approach is a cycle-jump criterion to determine the appropriate cycle-jump size based on a target increment of a global variable which monitors the advancement of fatigue. We propose the definition and meaning of this variable for three general stages of the fatigue life. In comparison to existing acceleration techniques, our approach needs no parameters and bounds for the cycle-jump size, and it works independently of the material, specimen or loading conditions. Since one of the monitoring variables is the fatigue crack length, we introduce an accurate, flexible and efficient method for its computation, which overcomes the issues of conventional crack tip tracking algorithms and enables the consideration of several cracks evolving at the same time. The performance of the proposed acceleration scheme is demonstrated with representative numerical examples, which show a speedup reaching up to four orders of magnitude in the high-cycle fatigue regime with consistently high accuracy. Graphical abstract

Combining Thermotherapy with Shoot Tip Culture or Cryotherapy for Improved Virus Eradication from In Vitro Actinidia macrosperma.

In recent years, kiwifruit viral diseases have become increasingly prevalent in kiwifruit-producing regions of China, significantly impacting both the yield and quality of kiwifruit. This has emerged as a significant constraint on the healthy and sustainable development of the kiwifruit industry. The use of virus-free propagation materials has been proven the most effective strategy for controlling plant viral diseases. In the present study, shoot tip culture, shoot tip cryotherapy, and their combinations with thermotherapy were established to eradicate Actinidia virus A (AcVA), Actinidia virus B (AcVB), and Actinidia chlorotic ringspot-associated virus (AcCRaV) from Actinidia macrosperma. Additionally, the impact of shoot tip size on virus eradication was evaluated. Among the three confirmed viruses, regardless of the procedure, AcVB was the easiest to eradicate, followed by AcVA and AcCRaV. Combining thermotherapy with shoot tip culture or cryotherapy resulted in a higher virus-free frequency (up to 27.3 and 50%, respectively) than shoot tip culture or cryotherapy alone (0 to 20%). Notably, the combination of thermotherapy and 0.5- to 1-mm shoot tip cryotherapy was shown to be the most effective protocol for virus eradication from A. macrosperma, which produced 50% of regenerated shoots free from all the tested viruses. To the best of our knowledge, this is the first report on virus elimination from kiwifruit infected with multiple viruses based on conventional shoot tip culture and shoot tip cryotherapy.

Numerical investigation of tip clearance designs for oblique-cut fin microchannels

Tip clearance represents a simple design intervention strategy to mitigate the high hydraulic penalties often associated with microchannel heat sinks. This approach has not been widely explored for enhanced microchannel heat sinks, having previously focused only on conventional (uniform) tip clearance design for straight microchannels. In view of this, the present work investigates the performance of an enhanced heat sink, specifically oblique-cut fin microchannels, with tip clearance designs. Two different designs are considered, namely conventional/uniform tip clearance (utc) and a newly conceptualized modulated tip clearance (mtc). Numerical simulations are conducted using ANSYS FLUENT 2022 R1 first for straight microchannels, which are considered the baseline to which oblique-cut fin microchannel designs are compared. The simulations are carried out under laminar flow regime including conjugate heat transfer in a heated solid substrate for flow rates of 250 – 650 mL/min. The results indicate that utc significantly reduces pressure drop though can increase thermal resistance for the oblique channels. The underlying physical mechanisms responsible for this observation are elucidated by examining thermal and flow behaviours in and around oblique cut slots. Based on the flow behaviour in oblique slots with utc, modulated tip clearance (mtc) concept is introduced and investigated. When compared to utc cases, mtc tends to reduce the thermal resistance substantially, though depending upon oblique cut angle and flow rate. However, the Performance Index (PI) shows that utc improves the overall performance in the range of 10–15 % compared to that observed with mtc cases, though the factor of improvement reduces closely to 5 % at 650 mL/min. In addition, the overall performance in terms of heat transfer and hydraulic pumping power further show that utc and mtc design strategies are competitive, and warrant further multi-objective optimization investigations to determine the best design option overall.

Effect of a brush tip on in-office bleaching gels in an attachable syringe: Hydrogen peroxide penetration, bleaching efficacy and amount of gel expended

ObjectiveEvaluate the penetration of hydrogen peroxide (HP) into the pulp chamber, bleaching efficacy (BE) and amount of gel expended during in-office bleaching using an applicator brush tip and conventional tip from different commercial brands. Materials and Methods104 human premolars were randomly distributed into thirteen groups (n = 8) according to the commercial brand: DSP White Clinic 35 % Calcium (DW), Nano White 35 % (NW), Total Blanc One-Step 35 % (TS), Whiteness HP Blue 35 % (WB), Potenza Bianco Pro SS 38 % (PB), Opalescence XTra Boost 40 % (OB), no bleaching (negative control), and application method: applicator brush tip and conventional tip for all groups. Initial HP concentration (%) was determined via titration and pH was measured with digital pH meter. Concentration (µg/mL) of HP into the pulp chamber was measured using UV–Vis spectrophotometry, the BE (ΔE*ab, ΔE00 and ΔWID) was evaluated with a digital spectrophotometer, and the amount of gel expended was evaluated using a precision analytical digital balance. Statistical analysis included two-way ANOVA, Tukey's, and Dunnett's test. Comparison between HP into the pulp chamber vs BE was performed with Person's correlation (α = 0.05). ResultsBrush tip demonstrated a low amount of HP in the pulp chamber compared to the conventional method for all bleaching gels (p < 0.0003), as well as lower amount of gel expended (p < 0.002). The brush tip did not result in a significant difference in BE compared to the conventional (p > 0.05). No correlations were found between both factors (p > 0.05). ConclusionBrush tip showed lower penetration of HP in the pulp chamber and a reduced volume of spent gel when compared to the conventional tip, for all commercial brands. Clinical relevanceBrush tip is recommended for bleaching gels in an attachable syringe due to its ability to reduce the penetration of HP into the pulp chamber and minimize the amount of bleaching gel used.

Improved non-contact vibration measurement via acceleration-based blade tip timing

The conventional displacement-blade tip timing (D-BTT) measurements often rely on Once-Per-Revolution (OPR) sensors to compute expected or theoretical time of arrival (TOA) based on rotational speed. However, integrating OPR sensors within the confined space of aero-engines presents challenges, and estimating theoretical TOA introduces computational errors, particularly for low-amplitude, high-frequency blade vibrations. This paper presents the Acceleration-based Blade Tip Timing (A-BTT) method as a solution. Building upon A-BTT, the acquisition of blade tip vibration acceleration serves not only to capture rapid changes in vibration but also to offer richer data for precise measurement of high-frequency blade vibrations. With only three blade tip timing sensors recording actual TOA without an OPR sensor, A-BTT eliminates the need for estimating expected TOA, thus mitigating calculation errors. Furthermore, by analyzing the relationship between maximum blade tip vibration acceleration and displacement during synchronous blade vibration, vibration parameters, such as natural frequency, can be directly identified without prior information such as engine orders. Simulation and experimental results validate the efficacy of the A-BTT method, demonstrating its successful application to specific aero-engine compressor rotor blades.

Self-retentive double-ended suction tip: A new and innovative concept in dentistry

ABSTRACT Aim: To create an innovative “double-ended and “self-retentive” suction tip that is specifically designed: To provide “dual action; which works under the rubber dam sheet as well above the rubber dam sheet at the same time. Also, to eliminate the need of holding the suction tip (being self-retentive) using a technical tip with which it can be fixed to the rubber dam frame. Methods: Three conventional suction tip with a few chair-side equipments are needed to create this innovative suction tip. It’s clinical applications is also very easy and can effortlessly be grasped. Results: The “double-ended and “self-retentive” suction tip works efficiently and provides desired level of moisture control. Conclusion: This new innovatively created suction device can be easily created chair-side and it can be a solution to provide moisture control “in and out” of the oral cavity.

Aerothermal Performance Robustness and Reliability Analysis of Turbine Blade Squealer Tip With Film Cooling

Abstract The uncertainty quantification in the turbine components' aerodynamic and heat transfer performances is widely considered to be the most challenging topic due to its intricate and nonlinear characteristics. This paper first proposes an efficient uncertainty quantification method based on an original parallel framework combining Polynomial Chaos Expansions (PCE) with two forms (stochastic response surface-based and Galerkin projection-based) and the Universal Kriging method. The rigorous mathematical tests are performed to verify the reliability and computational efficiency of the proposed method, and the results support that this method can dramatically reduce computational samples compared to the conventional PCE method while maintaining computational accuracy. Then, the genetic algorithm was introduced to establish an efficient uncertainty quantification framework, and it is applied to the aerothermal performance robustness investigation of the GE-E3 rotor blade tip with and without film cooling. Based on the findings of uncertainty quantification, the injection of cooling air drastically enhances the unstable tendency of the flow and thermal fields, resulting in the actual aerothermal performance of the squealer tip being much lower than that predicted by deterministic calculations. The setting of the film cooling, although effective in reducing the heat flux around the cooling holes, also induces more chaotic flow and thermal fields, leading to sharp heat flux fluctuations around the cooling holes. Finally, our novel reliability analysis algorithm, rooted in the quantification of uncertainty, corroborates the assertion that the introduction of coolant gas, while extending the operational longevity of turbine blades, confers only marginal improvements in the mitigation of lifespan variability. The comprehensive lifespan assessment elucidates that the mean operational longevity of the conventional squealer tip design stands at an estimated 16,169.44 h, accompanied by a standard deviation of 2,750.31 h. In stark contrast, the mean operational longevity of the squealer tip integrated with film cooling measures a significantly enhanced 17,035.17 h, exhibiting a standard deviation of 2,492.73 h. Consequently, the operational lifespan of the conventional squealer tip experiences a decrement of 10.17% in comparison to the anticipated mean lifespan, whereas the reduction for the film-cooled squealer tip registers at 5.36%.

Effects of the Slotted-Cavity Tip on the Vortices and Aerothermal Performance in the High-Pressure Turbine

To enhance aerodynamic performance in high-pressure turbines, cavity tips are commonly employed. However, these cavity tips tend to generate more vortices than flat tips, leading to an increased thermal load on the blade tips. This study introduces a novel configuration aimed at suppressing vortex intensity by incorporating a slot at the cavity bottom. Through numerical simulations, the impact of slot geometry parameters on vortices and aerothermal performance is investigated. The findings reveal that a slot height of 0–0.1 mm effectively suppresses the pressure side corner vortex within the cavity, while a slot height of 0.2–0.3 mm eliminates it. A slot height of 0.3 mm reduced average heat transfer and the high heat transfer region at the cavity bottom by 22.6% and 92.6%, respectively; however, it was observed that the leakage flow increased by 15.9%. Therefore, this study further combines the slot structure with a winglet to control the leakage flow. The combined structures exhibit superior overall performance compared to the single-slot cavity tip. Compared to the conventional cavity tips, the combined structure achieves a maximum reduction of 27.3% in average heat transfer and 7.9% in leakage flow, along with a decline of 1.9% in total pressure loss.

Effect of the type of application tip for 35% hydrogen peroxide on bleaching efficacy and tooth sensitivity: A randomized clinical trial.

Evaluate the bleaching efficacy (BE) and tooth sensitivity (TS) of in-office bleaching using different application tips. Forty-eight participants were selected (split-mouth), one to receive bleaching with an attached brush tip and one with a conventional tip. The procedure was performed with Whiteness Automixx Plus 35%. The BE was evaluated at the beginning, weekly, one and 12 months post-bleaching with a Vita Easyshade spectrophotometer (ΔE*ab, ΔE00, and WID) and with Vita classical A1-D4 and Vita Bleachedguide shade guides units (ΔSGU). Absolute risk and intensity of TS were recorded using the Visual Analogue Scale. The equivalence of BE was analyzed using the two one-sided t-tests for paired samples. The absolute risk of TS was evaluated using the McNemar test, and the TS intensity was measured with the paired t test (α = 0.05). The equivalence of BE was observed for both groups in all color evaluations (p > 0.05). A lower absolute risk and intensity of TS were observed for the attached brush tip when compared with the conventional tip (p < 0.003 and p < 0.0001). Using an attached brush tip showed the same BE as a conventional tip. However, for the attached brush tip, there was a reduction in TS. The applicator-attached brush tip is recommended for in-office dental bleaching, because of the possible reduction in risk and intensity of TS.

Tip Vortex Study of a Rotor with Double-Swept Blade Tips

An experimental aerodynamic study was conducted, analyzing the wake structure of a four-bladed model rotor with a forward-backward swept tip geometry inspired by the ONERA-DLR “Etude d´un Rotor Aéroacoustique Technologiquement Optimisé”-design. Similar tip designs are used on some modern helicopter main rotors. The experiments were conducted at the Rotor Test Facility Göttingen (RTG) in hover-like conditions using a stereoscopic high-speed particle image velocimetry system. The results are compared with those of a reference rotor using a conventional parabolic blade tip. The test parameters include both constant-pitch cases and pitch-oscillating cases with a cyclic swashplate input. The constant-pitch tests show a two-step stall behavior for the double-swept tip, with the first step characterized by a reduced thrust slope and a reduced rotor efficiency. This effect is explained by a repositioning and a structural change of the tip vortex generation. The pitch-oscillating cases show that the double-swept tip results in an earlier tip stall compared to the parabolic geometry while maintaining high thrust levels. The dynamic tip stall yields a break-down of the wake’s tip vortex system, which is replaced by a spanwise band with small-scale turbulent structures and trailed vorticity, but no large-scale vortices.

On the Aero-Thermal Performance of Rim Film Cooling in the Squealer Tip of a Linear Turbine Cascade

Abstract The present study proposes a novel rim film cooling design, motivated by the fact that the suction-side rim and the cavity floor near the leading edge of a conventional squealer tip with a camber-line film hole array are directly subjected to high-temperature gas. The new design consists of cooling injection for rim-hole or -slot cooling at the leading edge. The parameters of injection geometry and cavity depth are also discussed in this study. The flow physics, leakage flowrate, heat transfer characteristics, and vortices in the cavity are carefully analyzed. The results show that rim film cooling can substantially inhibit tip heat transfer and the amount of hot leakage flow. Compared with the typical design, the maximum and average heat transfer coefficients of the blade tip of the rim slot case are reduced by 12.83% and 5.43%,, respectively. The variation in cavity depth is sensitive to the heat transfer on the cavity floor of the squealer tip blade. With the optimal design, the average and maximum heat transfer coefficients are reduced by 14.42% and 14.21%,, respectively. In addition, the leakage flowrate can be reduced by a maximum of 3.67% by rim injection compared with the conventional squealer tip.

Effect of multi-cavity on the aerothermal performance robustness of the squealer tip under geometric and operational uncertainties

A multitude of uncertainties intertwined within the manufacturing and functioning of gas turbines has often been overlooked in numerous prior investigations regarding the aerothermal performance of blade tips. Consequently, the actual lifespan of the blades falls considerably short of the initially anticipated duration. This study proposes an efficient parallel turbo robustness analysis framework and aims to delve into the uncertain characteristics exhibited by various multi-cavity squealer tips during real-world gas turbine operations. The findings of this research reveal that the inclusion of ribs has an adverse impact on the flow field, leading to heightened chaotic tendencies and a considerable reduction in the expected aerodynamic efficiency of the multi-cavity squealer tip. The leakage flow experiences a notable increase, reaching values of 22.30%, 17.88%, and 24.51% for the three distinct multi-cavity configurations, surpassing the corresponding value of 13.63% observed for the conventional squealer tip. However, integrating the flow field uncertainty into the thermal field uncertainty proves challenging due to the disruption of the cavity vortex system caused by the pressure side ribs. Thus, the heat transfer performance of the multi-cavity squealer tip exhibits superior robustness compared to that of the conventional squealer tip. Furthermore, this paper introduces a novel evaluation index, based on comprehensive uncertainty flow and thermal analyses, to assess the robustness of the aerothermal performance. The present work makes a valuable contribution to the development of digital twins for turbomachinery systems.

Aerothermal optimization of turbine cascade squealer tip with non-uniform squealer height

The squealer tip has significant influence on both the aerodynamic and heat transfer characteristics of the high-pressure turbine blade. However, due to the complexity of parameterization and meshing of the squealer and the complicated flow structure within the over-tip region, the existing squealer designs in the open literature have constant squealer heights. In this paper, the design space to the squealer height with non-uniform squealer height is extended and the new flow features it may bring are investigated. A parameterization system specifically designed for the non-uniform squealer height using five control parameters is implemented to automatically generate the geometry and hybrid meshes. Combining it with the multi-objective optimization system using genetic algorithms, a transonic turbine cascade squealer tip is optimized employing Reynolds-averaged Navier–Stokes k–ω shear stress transport model. The main objective of this study is to obtain a squealer configuration with the lowest total pressure loss coefficient and heat transfer coefficient. The optimum configuration with non-uniform squealer height achieves improvements in both the aerodynamic efficiency and the heat transfer performance, relative to the baseline conventional squealer tip geometry with the constant squealer height. Additionally, this work demonstrates that a flow structure in which the main flow forms a “blanket” below the leakage flow in the squealer is beneficial for aerothermal performance, especially reducing heat transfer losses, which provides valuable insight into the squealer tip design of advanced high-pressure turbines.

Composition and Bioactivity of Chlorogenic Acids in Vegetable and Conventional Sweet Potato Vine Tips.

Sweet potato vine tips are abundant in chlorogenic acid (CGA). In this study, CGA was extracted from vegetable and conventional sweet potato vine tips using ethanol, followed by subsequent purification of the extract through a series of sequential steps. Over 4 g of the purified product was obtained from 100 g of sweet potato vine tip powder, producing more than 85% of purified CGA. The LC-MS analysis of all samples indicated that 4-CQA was the predominant isomer in both sweet potato cultivars. Significant variations of p-coumaroyl quinic acids, feruloyl quinic acids, dicaffeoyl quinic acids, and tricaffeoyl quinic acid were identified, whereas the mono-caffeoyl quinic acids did not vary when the two sweet potato varieties were compared. Compared to conventional sweet potatoes, vegetable sweet potatoes exhibit a high negative correlation between 4-CQA and 5-pCoQA, while showing a high positive correlation between 3,5-CQA and 3-pCoQA. A series of principal component analyses (PCA) using CGA isomers enables a clear differentiation between vine tips derived from vegetable and conventional sweet potatoes. The model of linear discriminant analysis, based on the characteristic CGA, achieved a 100% accuracy rate in distinguishing between vegetable and conventional sweet potatoes. The high purity of sweet potato CGA (SCGA) exhibited potent anti-breast cancer activity. The results demonstrated that SCGA significantly suppressed the clonogenicity of MB231 and MCF7 cells, and impeded the migratory, invasive, and lung metastatic potential of MB231 cells.

Inferring mechanical properties of the SARS-CoV-2 virus particle with nano-indentation tests and numerical simulations

The pandemic caused by the SARS-CoV-2 virus has claimed more than 6.5 million lives worldwide. This global challenge has led to accelerated development of highly effective vaccines tied to their ability to elicit a sustained immune response. While numerous studies have focused primarily on the spike (S) protein, less is known about the interior of the virus. Here we propose a methodology that combines several experimental and simulation techniques to elucidate the internal structure and mechanical properties of the SARS-CoV-2 virus. The mechanical response of the virus was analyzed by nanoindentation tests using a novel flat indenter and evaluated in comparison to a conventional sharp tip indentation. The elastic properties of the viral membrane were estimated by analytical solutions, molecular dynamics (MD) simulations on a membrane patch and by a 3D Finite Element (FE)-beam model of the virion's spike protein and membrane molecular structure. The FE-based inverse engineering approach provided a reasonable reproduction of the mechanical response of the virus from the sharp tip indentation and was successfully verified against the flat tip indentation results. The elastic modulus of the viral membrane was estimated in the range of 7–20 MPa. MD simulations showed that the presence of proteins significantly reduces the fracture strength of the membrane patch. However, FE simulations revealed an overall high fracture strength of the virus, with a mechanical behavior similar to the highly ductile behavior of engineering metallic materials. The failure mechanics of the membrane during sharp tip indentation includes progressive damage combined with localized collapse of the membrane due to severe bending. Furthermore, the results support the hypothesis of a close association of the long membrane proteins (M) with membrane-bound hexagonally packed ribonucleoproteins (RNPs). Beyond improved understanding of coronavirus structure, the present findings offer a knowledge base for the development of novel prevention and treatment methods that are independent of the immune system.

Use of the Interalar Ligament Flap for Tip and Supratip Contouring in Primary Open Structural Rhinoplasty.

Precise tip contouring is paramount to achieve pleasant cosmetic results in rhinoplasty. Loss of tip projection or rotation, supratip deformities, and long-lasting edema may jeopardize the outcome and lead to patient dissatisfaction or to reintervention. Several approaches have been reported, sometimes with considerable drawbacks or conclusions supported mainly by experience. The aim of this study was to describe the interalar ligament flap for tip and supratip contouring and to comparatively assess its efficacy and safety. The study included 147 patients who underwent primary structured open rhinoplasty and were divided into 2 groups: group 1 underwent harvesting and repositioning of the interalar ligament flap, and group 2 underwent conventional tip dissection. Tip edema, supratip definition, and fullness were blindly scored at 2-, 6-, and 12-month postoperative follow-up. Nasolabial angle was measured at 2 and 12 months postoperatively. Univariate analysis and multivariable regression modeling were performed. Supratip definition was significantly higher in group 1 at the 2-, 6-, and 12-month postoperative follow-up visits ( P < 0.05, P < 0.01, and P < 0.01, respectively). Tip edema and supratip fullness were significantly lower in group 1 at each time point ( P < 0.01). Nasolabial angle, and its modification between 2 and 12 months after intervention, did not differ in the 2 groups. All findings were confirmed when controlled for eventual confounders. The interalar ligament flap has proven to be versatile, effective, and consistently reliable in reducing tip edema and improving supratip definition. It may be tailored to the patient, partially folded to improve tip projection, or used to camouflage tip grafts. Therapeutic, III.

Biomechanical Evaluation of Case Hook Designs for Selector Use in Distribution Centers

Case hooks are tools used in distribution centers by selectors to help them reach and pull products located on the back half of a pallet. This study investigated the postural, electromyographic, and usability responses as 4 handle and 3 tip types were used to pull cases forward on a pallet. The data suggest the pistol grip may be most biomechanically advantageous. With the pistol grip, the rake and conventional tips worked well and had good usability scores.

Effect of flow rate ratio and positioning on a lighthouse tip ECMO return cannula.

Extracorporeal membrane oxygenation is a life-saving support therapy in the case of cardiopulmonary refractory failure. Its use is associated to complications due to the presence of artificial surfaces and supraphysiological stress conditions. Thus, knowledge of the fluid structures associated to each component can give insight into sources of blood damage. In this study, an experimentally validated numerical study of a conventional lighthouse tip cannula in return configuration was carried out to characterize the flow structures using water or a Newtonian blood analog with different flow rate ratios and cannula positioning and their influence on hemolysis. The results showed that strong shear layers developed where the jets from the side holes met the co-flow. Stationary backflow regions at the vessel wall were also present downstream of the cannula. In the tilted case, the recirculation was much more pronounced on the wide side and almost absent on the narrow side. Small vortical backflow structures developed at the side holes which behaved like obstacles to the co-flow, creating pairs of counter-rotating vortices, which induced locally higher risk of hemolysis. However, global hemolysis index did not show significant deviations. Across the examined flow rate ratios, the holes on the narrow side consistently reinfused a larger fraction of fluid. A radial force developed in the tilted case in a direction so as to recenter the cannula in the vessel.

Experimental and computational assessment into the heat transfer for the blade multicavity tips

In the gas turbine, the tip region of the shroudless blade is under severe heat load, and thus is seriously ablated. Therefore, an in-depth understanding of the tip heat transfer distributions is of great significance for tip cooling design. In the present work, the heat transfer coefficient distributions of the multicavity tips were measured by a steady-state thermal-analysis method with Infrared camera. The measurements were conducted under two inlet Reynolds number conditions (1.10 × 105, 2.23 × 105) and two tip gaps (1.6 %, 3.5 % Chord length). In addition, the computational simulations verified by the experimental data were conducted to attain the detailed flow field near the tip, and to gain insight into the heat transfer characteristics. Measured results show that additional hot spots are detected behind the rib for the multicavity tips with three or four cavities owing to the leakage flow reattachment. The heat transfer at the suction-side corner is also enhanced by the multicavity tips, whereas a low heat transfer coefficient region is found in the corner in front of the rib. Increasing the inlet Reynolds number would not change the heat transfer patterns, but would evidently increase the heat transfer coefficient values. Adopting a larger tip gap also increases the heat transfer coefficient values, but the effect is not so obviously as the inlet Reynolds number. Compared with the conventional one-cavity tip, the multicavity tips can reduce the aerodynamic losses, and the loss values are reduced by about 2 %.