Peak Jet Research Articles

Multiple Episodes of Remote Brightenings Driven by a Coronal Extreme-ultraviolet Jet on the Sun

Abstract Remote brightening (RB) is compact brightening at footpoints of magnetic loops, which are remotely connecting to and confining an eruption in the solar atmosphere. Here, we report on observations of an RB resulting from an EUV jet with a speed of about 90 km s−1. The loops connecting the RB and the jet have an apparent length of about 59 Mm. Intriguingly, the RB exhibits at least two episodes of brightenings, as characterized by two peaks in its lightcurve. The energies that sustain the first and second peaks of the RB are 6.3 × 1026 erg and 8.4 × 1026 erg, respectively, and comprise a significant proportion of the total energy. The first peak of the RB brightenings coincides with the jet's peak with a time delay of 12 s, while the second peak lags behind by 108 s. Besides the flows of the ejecta, we have identified two additional flows originating from the eruption site. One is relatively cool with a temperature of log 10 ( T / K ) = 5.8 –6.1 and a speed of about 275 ± 15 km s−1. The other is hot with a temperature of log 10 ( T / K ) = 7.0 –7.3 and a much greater speed of about 750 ± 70 km s−1. We attribute the second peak of RB directly to this hot flow, which our numerical experiments suggest is the result of a slow shock wave. Considering the minimal time delay between the first peak of RB and the eruption, we infer that this first episode is due to heating by nonthermal electrons. Our research demonstrates that the dynamics in an RB can offer vital insights into the nature of the corresponding eruption and help understand how energy is distributed throughout the solar atmosphere.

Micro-jet formation induced by the interaction of a spherical and toroidal cavitation bubble.

We investigate experimentally and numerically the interaction between a spherical cavitation bubble and a wall-bounded toroidal cavitation bubble. We demonstrate that shock wave focusing following toroidal bubble initiation induces the formation of micro-jets that pierce the spherical bubble in the torus-axis direction away from the surface, strongest in the anti-phase scenario. The velocity of micro-jets is determined by the initial standoff distance of the spherical bubble from the wall and thus from the toroidal bubble, with peak jet velocities approaching 1000m/s. The micro-jets are triggered by the complex interaction between the torus shock wave and the surface of the spherical bubble. Additionally, the formation of secondary cavitation appears to significantly enhance the micro-jets compared to scenarios without secondary cavitation. Following the formation of micro-jets, a subsequent broad jet pierces the spherical bubble, marking the onset of its collapse. After the collapse, we observe an amplified rebound phase resulting in a more than twofold increase of the bubble volume compared to the initial bubble.

Impact of sex-specific thresholds for low flow in assessment of prognosis in concordantly and discordantly graded aortic valve stenosis.

Sex-specific low flow was recently defined as stroke volume index (SVi) ≤40 ml/m² in men and ≤32 ml/m² in women. We tested the prognostic association of these cut-offs in patients with aortic stenosis (AS) with concordantly and discordantly graded AS (CGASEL and DGASEL) based on pressure recovery adjusted aortic valve area (energy loss, EL). Data from 1351 patients with asymptomatic AS, peak jet velocity <4m/s and preserved left ventricular ejection fraction enrolled in the Simvastatin and Ezetimibe in AS study was used. DGASEL was defined as EL <1.0 cm² with mean aortic gradient <40 mmHg, and CGASEL as EL ≥1.0 cm² with mean aortic gradient <40mmHg. Patients were further grouped into normal and low flow. Outcome was combined all-cause death and hospitalization for heart failure. CGASEL with normal/low flow was present in 915/253 patients, and DGASEL with normal/low flow in 57/126 patients. During median 4.3 years follow-up, event-free survival was lower in patients with DGASEL irrespective of flow compared to CGASEL with normal flow (p<0.05). In Cox regression analysis, DGASEL with normal or low flow were both associated with increased risk of all-cause death and hospitalization for heart failure after adjustment for age, sex, heart rate, randomized study treatment, hypertension, aortic valve replacement and aortic valve calcification (p<0.05). No survival difference was found between patients with normal vs. low flow within groups of DGASEL or CGASEL. Identification of low flow by the proposed sex-specific thresholds of SVi needs more prognostic validation before application in clinical practice.

LncRNA MEG3 promotes aortic valve calcification by inducing osteoblast differentiation via Wnt catenin signaling pathway

Abstract Background Calcific aortic valve stenosis (CAVS) is the most common valvular heart disease in elderly population. This study aimed to investigate the role of long non-coding RNAs (lncRNAs) in the development of CAVS. Methods ldlr-/-mice were feeding with western diet for 6 months to induce CAVS. RNA-seq analysis was performed to identify differentially expressed molecular signaling between aortic valves of CAVS mice and control mice. The degree of aortic stenosis was detected by ultrasound. Calcium salt deposits were detected by Haematoxylin and eosin (H&amp;E) staining, Von Kossa staining and alizarin red S staining. PCR and western blotting were employed to detect osteogenic differentiation markers after various interventions. Results A mouse CAVS model was successfully established, as evidenced by increased thickness and calcium deposition in the aortic valve leaflets and increased transvalvular peak jet velocity. RNA-seq analysis showed that lncRNA MEG3 was significantly enriched in aortic valves of CAVS mice as compared to that of control mice. MEG3 expression in aortic valve, assessed by RNA in situ hybridization and PCR, was also significantly upregulated during the osteoblast differentiation of AVICs in vitro. Gain- and loss-of-function experiments indicate that MEG3 could indeed promote osteoblast differentiation of primary AVICs as evidenced by increased calcified nodule formation and expressions of osteoblast differentiation markers (Runx2 and osterix). Consistent with these in vitro data, MEG3 knockdown in vivo through tail injection of antisense oligonucleotide chain MEG3 (ASO-MEG3) at 6 weeks interval for 12 weeks significantly attenuated aortic valve calcification in CAVS mice. Subsequent KEGG analysis demonstrated that the Wnt/β-catenin signaling pathway was significantly enriched during the CAVS progression. Overexpression of MEG3 activated the Wnt/β-catenin signaling pathway and upregulated osteogenic protein expressions, while this upregulation could be significantly ameliorated by Dickkopf 1, a Wnt/β-catenin pathway inhibitor. Conclusion Present study demonstrates that LncRNA MEG3 could promote aortic valve calcification by inducing osteoblast differentiation via activating Wnt/β-catenin signaling pathway. Our results provide experimental evidence of targeting MEG3 and Wnt/β-catenin signaling pathway as potential promising therapeutic option for prevention and treatment of aortic valve calcification.

Left ventricular mass index and prognosis of symptomatic severe aortic stenosis in women and men

Abstract Background Symptomatic severe aortic stenosis (AS) requires surgical (SAVR) or transcatheter aortic valve replacement (TAVR), and many patients are on the procedure waiting list. The diagnosis of severe AS is based on clinical and echocardiographic criteria, such as left ventricular ejection fraction (LVEF), aortic valve area (AVA), mean transvalvular gradient, and peak aortic jet velocity. However, there is a gap in knowledge regarding the influence of left ventricular mass on the prognosis of these patients, especially considering differences between women and men. Purpose To evaluate the influence of left ventricular mass index (LVMi) on the mortality of women and men with severe AS awaiting SAVR or TAVR. Methods A prospective study analysed the death rate in 531 outpatients with symptomatic severe AS with mean transvalvular gradient ≥40 mmHg, AVA ≤1.0 cm2, or peak aortic jet velocity ≥4.0m/s at echocardiography with the indication for TAVR or SAVR in the period from April 2020 to February 2024. Baseline data included analysis of clinical characteristics, echocardiographic variables, and the presence of coronary artery disease (CAD). Statistical analyses were performed using the Kaplan-Meier (K-M) and Cox proportional hazards methods to analyze mortality rates in women and men. Results The mean age was 74.7±11.6 years, with 283 (53.3%) men. Over a follow-up period of 2.67±1.22 years, death occurred in 165 (31.1%), 148 (86%) due to cardiovascular disease, and 152 (92%) had heart failure (HF) NYHA II to IV, 51 (9,6%) had angina, and syncope in 11 (2.1%) of the patients. Patients who died had lower LVEF (61.4%±8.9% vs. 58.8%±10.8%; p=0.008) and higher LVMi (125.3±32.5 g/m2 vs. 115.5±29.3 g/m2; p=0.001). Angina, syncope, hypertension, dyslipidemia, diabetes, smoking, atrial fibrillation, and CAD prevalence were similar in living patients and in those who died. Both groups had similar echocardiographic data, such as left atrial volume, mean transvalvular gradient, and peak jet velocity. TAVR and SAVR were done in 111 (20.9%) and 162 (30.5%) patients. Of these, 21 (18.9%) and 20 (12.4%) died during follow-up, respectively. Cumulative mortality of all patients was higher with LVMi &amp;gt;115 g/m2 compared to ≤115 g/m2 (p=0.008)(Figure). In women but not in men, cumulative mortality was higher with LVMi &amp;gt;115 g/m2 compared to ≤115 g/m2 (p=0.046). Cox multivariate analysis, adjusted for LVEF, LVMi, CAD, and age, showed LVMi as an independent variable for death [HR=1.50 (95%CI: 1.10-2.05); p=0.011]. LVEF [HR=0.97 (95%CI: 0.95-0.99); p=0.009] and LVMi [HR=1.75 (95%CI: 1.10-2.79); p=0.016] were independent variables for death in women, but not in men. Conclusion Women with higher LVMi and lower LVEF should have valve intervention prioritized.Figure

Discordance between symptomatic response and changes in cardiac structure and function one year after transcatheter aortic valve implantation

Abstract Background Symptomatic improvement is one of the main goals of transcatheter aortic valve implantation (TAVI) in patients with severe symptomatic aortic stenosis. We hypothesized that the degree of symptomatic response after TAVI is associated with improvement in cardiac structure and function after TAVI. Purpose We aimed to evaluate 1) the change in symptomatic burden measured by New York Heart Association (NYHA) and Canadian Cardiovascular Society (CCS) functional class after TAVI, 2) the change in echocardiographic structural and functional parameters after TAVI, and 3) the association of symptomatic response with echocardiographic response as well as long-term survival. Methods In patients undergoing TAVI, we assessed New York Heart Association (NYHA) and Canadian Cardiovascular Society (CCS) functional class at 12 months. Symptomatic response was defined as NYHA/CCS class I or ≥ 1 improvement in NYHA/CCS class compared to baseline at 12 months. Echocardiographic images at baseline and 6-18 months post-TAVI were analysed using an automated, validated, deep-learning workflow. Logistic regression was used to assess association between change in echocardiographic parameters and symptomatic change at 12 months. The association of symptomatic response and echocardiographic changes in the first 12 months after TAVI with survival beyond 12 months, was evaluated by landmark analysis using Kaplan-Meier analysis. Results Among 868 TAVI patients (median age 80 years, 53% female), the majority (74%) had NYHA/CCS class III at baseline and 77% of patients experienced improvement in symptoms at 12 months post-TAVI (Figure 1). Patients without an improvement in symptoms more often had COPD, atrial fibrillation and more heart failure medications compared to responders. Left ventricular systolic function did not show improvement compared to baseline, whereas a modest improvement in left atrial volume index, left ventricular mass index, E/A ratio, E/e’ ratio, mean e’ and tricuspid regurgitation peak jet velocity was observed. Symptomatic response was not associated with echocardiographic response. Beyond 12 months, patients with symptomatic improvement had lower mortality than those without symptomatic improvement (1.5 vs. 2.4 per 10 patient years; p = .001), whereas changes in echocardiographic parameters were not associated with subsequent mortality (Figure 2). Conclusion Patients undergoing TAVI for symptomatic severe aortic stenosis, showed substantial symptomatic improvement at one year after the procedure, whereas only a modest improvement in echocardiographic parameters was observed. Improvement in symptoms was not associated with improvement in echocardiographic measures of cardiac structure and function. Symptomatic improvement, but not improvement in cardiac structure and function at 12 months, was a strong predictor of subsequent survival.Change in NYHA/CCS class after TAVISymptoms and echo versus mortality

Right ventricular myocardial work predicts heart failure hospitalizations irrespective of ejection fraction

Abstract Hospitalization for heart failure worsening (HFW) associates with increased subsequent rehospitalization rate and mortality irrespective of left ventricular ejection fraction (EF). However there’s little evidence regarding predictors of HFW to timely apply preventive measurements. Since right ventricular (RV) dysfunction often associates with more advanced stages of HF we assumed that RV myocardial work (MW) assessment might be used in prediction of HFW. Methods 158 patients with HF (48% female) 58±7 years on guideline directed medical therapy in sinus rhythm and with at least one hospitalization in the last 6 months were enrolled in the study. Patients with HFrEF, HFmrEF and HFpEF were evenly represented. All patients were appropriately decongested prior to the study. The primary outcome was rehospitalization, HFW or cardiovascular death. RVMW was derived from RV global strain, including interventricular septum, and noninvasively estimated pulmonary arterial pressure (PAP). Systolic PAP (sPAP) was measured as the sum of maximum RV and right atrial (RA) pressure gradient (PGmax) from tricuspid regurgitation (TR) jet peak velocity and mean right atrial pressure (RAP) estimated from diameter and collapsing of inferior vena cava. Mean PAP (mPAP) was measured as the sum of PGmean RV-RA by tracing TR jet and RAP. Diastolic PAP was estimated as dPAP = 1.5 × [mPAP − (sPAP/3)]. Then RV global work index (RVGWI), constructive (RVGCW), and efficient work (RVGWE) were derived by the software dedicated for left ventricular MW. Left ventricular global longitudinal strain, left atrial (LA) reservoir strain (LAS), LA pump strain, LA volume index (LAVi), B lines, inferior vena cava, NT-pro-BNP, TAPSE/sPAP and RVMW were also measured. Patients followed up for 12 months. Results 53 events were registered at 12 months of which 42 rehospitalizations due to HFW and 11 CV deaths. Among all parameters in the multivariate analysis lower RVGCW was associated with HFW (HR 0.978, 95% CI 0.973–0.998, p = 0.014). RVGCW was the most powerful predictor of CV events (AUC 0.91) with cut off value of 148 mmHg% that had 96% sensitivity and 88% specificity. Number of patients who died with RVGCW &amp;lt; 148 mmHg% was 8 of 11 (73%) total deaths (HR 0.421, 95% CI 0.083–0.986, p = 0.028). Conclusion RVGCW was a predictor of HFW and 1 year mortality in patients with HF irrespective of EF.

Experimental investigation of a spanwise plasma jet array in a turbulent boundary layer for skin-friction drag reduction

Three different types of particle imaging velocimetry (PIV) measurements, namely planar-PIV, micro-PIV, and stereo-PIV, are integrated to provide a full picture of the interaction between a spanwise plasma jet array and a turbulent boundary layer (TBL) at Reθ = 1208. Quiescent-flow characterization reveals that the plasma actuator array induces a wavy jet. With increasing duty cycle (DC), the peak jet velocity grows yet the height of the jet body decreases. When the TBL is actuated by such a plasma jet array, the spanwise distribution of the relative drag variation exhibits two regions with opposite signs, and the formation of these two regions can be attributed to the upwash and the downwash effects of the plasma-induced vortex, respectively. After spatial-averaging in the plasma actuation zone, net drag reduction (DR = 3.2%) is only achieved at the lowest DC of 10%. Although, by increasing the duty cycle, more drag reduction can be obtained in the upwash zone, the accompanying drag increase in the downwash zone is even prominent.

On-demand jetting of high-viscosity liquid by jet tube impact

The on-demand jetting of high-viscosity liquid has significant applications in fields such as electronic packaging and bioprinting. Conventional methods for high-viscosity liquid jetting often employ a needle propelling the liquid rapidly, which demands high precision in the manufacturing and assembly of the needle and nozzle, and can potentially damage biomaterials. In this study, a novel method utilizing jet tube impact for on-demand high-viscosity liquid jetting is proposed, leveraging the inherent inertia of the liquid to generate the pressure pulse necessary for on-demand jetting. This method reduces the precision requirements for the device, enables device simplification, and avoids harm to biomaterials. The feasibility of this approach for on-demand high-viscosity liquid jetting is validated through experiments, and by combining numerical simulations, the jetting mechanism is revealed and primary factors influencing jetting performance are investigated. It is found that the water hammer pressure wave induced by the liquid inertia during the sudden velocity change of the jet tube is the predominant driving force for jetting, and the peak pressure can exceed 1 MPa and the peak jet velocity can exceed 15 m/s. An increase in the jet tube impact velocity and an extension of the acceleration duration at the same impact velocity both lead to an increase in the pressure wave amplitude. In addition, a decrease in the liquid level height shortens the period of the pressure wave. These factors all have an influence on the jetting performance. This study provides a new insight and theoretical foundation for the on-demand high-viscosity liquid jetting.

Insights into calcific aortic valve stenosis: a comprehensive overview of the disease and advancing treatment strategies

Aortic valve stenosis is a disease characterized by thickening and narrowing of the aortic valve (AV), most commonly due to calcification, which leads to left ventricular outflow obstruction called calcific aortic valve disease (CAVD). CAVD presents as a progressive clinical syndrome with cardiorespiratory symptoms, often with rapid deterioration. The modern-day pathophysiology of CAVD involves a complex interplay of genetic factors, chronic inflammation, lipid deposition, and valve calcification, with early CAVD stages resembling atherosclerosis. Various imaging modalities have been used to evaluate CAVD, with a recent trend of using advanced imaging to measure numerous AV parameters, such as peak jet velocity. Significant improvements in mortality have been achieved with transcatheter AV repair, but numerous therapeutics and modalities are being researched to delay the progression of CAVD. This article aims to provide a comprehensive review of CAVD, explore recent developments, and provide insights into future treatments with various novel modalities.

Novel Noninvasive Index Combining Echocardiography and Computed Tomography for Screening for Pulmonary Hypertension in Patients With Systemic Sclerosis

BackgroundIn patients with systemic sclerosis (SSc), early detection of pulmonary hypertension (PH) improves survival. This study aimed to investigate whether a combination index (cPAT) of the tricuspid regurgitation jet peak gradient and the ratio of pulmonary artery (PA) diameter to aortic diameter measured by computed tomography (CT; PA ratio) can estimate the mean PA pressure (mPAP) and detect PH more accurately than conventional parameters in SSc patients. MethodsA total of 36 SSc patients who underwent PH screening were retrospectively analyzed. All patients were screened for PH between 2013 and 2017 by echocardiography, CT, and right heart catheterization. Patients with mPAP > 20 mm Hg by right heart catheterization were diagnosed as having PH. Additionally, patients with an mPAP > 20 mm Hg, pulmonary vascular resistance > 2 Wood units, and PA wedge pressure ≤ 15 mm Hg, for whom other causes were ruled out, including group 2-5, were defined as having pulmonary atrial hypertension. ResultsOf 36 patients, 29 patients were female (81%), and the average duration of SSc was 7.5 years. The mPAP was significantly correlated with the tricuspid regurgitation jet peak gradient (r = 0.734), the PA ratio (r = 0.584), and the cPAT (r = 0.848). In receiver operating characteristic analysis to identify PH, the cPAT showed the highest area under the curve, 0.906, among the 3 parameters. Additionally, in receiver operating characteristic analysis to identify pulmonary atrial hypertension, the cPAT also showed the highest area under the curve, 0.851, among the 3 parameters. ConclusionsThe cPAT is a new index combining echocardiogram and CT results that provides the most accurate noninvasive assessment of mPAP in SSc patients. The cPAT can also help detect PH early in SSc patients, thereby allowing for earlier treatment.

Wall confinement effects on the dynamics of cavitation bubbles in thin tubes

Cavitation is a common phenomenon in nature and has numerous applications. In contrast to a cavitation bubble in a free domain, a cavitation bubble in a thin tube is restricted by the tube wall, which is expected to significantly affect bubble evolution, but its mechanism is still unclear. In this study, the dynamics of a cavitation bubble in a thin circular tube is studied by numerical simulation, focusing on the confinement effects of the tube. The results show that besides affecting the size and lifetime of the bubble, the confinement effects of the tube lead to the generation of counter jets and a ring jet during the contraction process of the bubble, and the curvature of the two counter jets determines the ring jet's peak velocity. When the bubble deviates from the midpoint of the tube in the axial direction, the two sides of the bubble along the axial direction show asymmetric behaviors, which results in the bubble migrating toward the midpoint. The tube diameter, tube length, liquid viscosity, and initial bubble position can significantly influence the degree of confinement effects, which can be characterized by the variations of several key indicators, such as bubble size, lifetime, degree of deformation, counter jet velocity, ring jet velocity, and axial migration of the bubble.

Prediction of the Individual Aortic Stenosis Progression Rate and its Association With Clinical Outcomes

BackgroundThe progression rate of aortic stenosis differs between patients, complicating clinical follow-up and management. ObjectivesThis study aimed to identify predictors associated with the progression rate of aortic stenosis. MethodsIn this retrospective longitudinal single-center cohort study, all patients with moderate aortic stenosis who presented between December 2011 and December 2022 and had echocardiograms available were included. The individual aortic stenosis progression rate was calculated based on aortic valve area (AVA) from at least 2 echocardiograms performed at least 6 months apart. Baseline factors associated with the progression rate of AVA were determined using linear mixed-effects models, and the association of progression rate with clinical outcomes was evaluated using Cox regression. ResultsThe study included 540 patients (median age 69 years and 38% female) with 2,937 echocardiograms (median 5 per patient). Patients had a linear progression with a median AVA decrease of 0.09 cm2/y and a median peak jet velocity increase of 0.17 m/s/y. Rapid progression was independently associated with all-cause mortality (HR: 1.77, 95% CI: 1.26-2.48) and aortic valve replacement (HR: 3.44, 95% CI: 2.55-4.64). Older age, greater left ventricular mass index, atrial fibrillation, and chronic kidney disease were associated with a faster decline of AVA. ConclusionsAVA decreases linearly in individual patients, and faster progression is independently associated with higher mortality. Routine clinical and echocardiographic variables accurately predict the individual progression rate and may aid clinicians in determining the optimal follow-up interval for patients with aortic stenosis.

A novel mouse model of calcific aortic valve stenosis.

Calcific aortic valve stenosis (CAVS) is one of the most challenging heart diseases in clinical with rapidly increasing prevalence. However, study of the mechanism and treatment of CAVS is hampered by the lack of suitable, robust and efficient models that develop hemodynamically significant stenosis and typical calcium deposition. Here, we aim to establish a mouse model to mimic the development and features of CAVS. The model was established via aortic valve wire injury (AVWI) combined with vitamin D subcutaneous injected in wild type C57/BL6 mice. Serial transthoracic echocardiography was applied to evaluate aortic jet peak velocity and mean gradient. Histopathological specimens were collected and examined in respect of valve thickening, calcium deposition, collagen accumulation, osteogenic differentiation and inflammation. Serial transthoracic echocardiography revealed that aortic jet peak velocity and mean gradient increased from 7 days post model establishment in a time dependent manner and tended to be stable at 28 days. Compared with the sham group, simple AVWI or the vitamin D group, the hybrid model group showed typical pathological features of CAVS, including hemodynamic alterations, increased aortic valve thickening, calcium deposition, collagen accumulation at 28 days. In addition, osteogenic differentiation, fibrosis and inflammation, which play critical roles in the development of CAVS, were observed in the hybrid model. We established a novel mouse model of CAVS that could be induced efficiently, robustly and economically, and without genetic intervention. It provides a fast track to explore the underlying mechanisms of CAVS and to identify more effective pharmacological targets.

TPIV Experimental Investigation of Film Coolant-to-Mainstream Interaction From Shaped Cooling Holes With Various Inlet Geometries

Abstract In this investigation, multiple sets of time-averaged tomographic particle imaging velocimetry measurements are completed for laid-back, fan-shaped film cooling holes with “racetrack” shaped inlets. Traditional 10-10-10, laid-back, fan-shaped holes are inclined 30 deg to the mainstream flow on a flat plate. The inlet cross section varies from round to two elongated racetrack shapes. The cross-sectional area and the outlet-to-inlet area ratio for all the geometries are held constant. The flat plate is installed in a low-speed wind tunnel with a mainstream turbulence intensity of 8% and an average velocity of 21.6 m/s. The blowing ratios of the film jets range from 0.6 to 1.5 and the density ratio is 1. The Reynolds number of the cooling jet varies from 2600 to 8400. The characteristics of the resulting flowfield are coupled with the detailed film cooling effectiveness distributions. It can be noted from the results that the counter-rotating vortex pair generated by the 2:1 inlet is the closest to the surface and weakest in strength, likely caused by the minimum peak jet momentum of the three. The Reynolds stresses downstream of the 2:1 and 4:1 inlets are significantly lower than those downstream of the shaped hole with a round inlet. An inverse relation between volumetric turbulence accumulation (TA), and surface effectiveness (η), can be correlated for the blowing ratios considered. The turbulence accumulation term can thus be used to evaluate the performance of a film cooling hole design with flowfield data.

Characteristics of argon discharge plasma jet: comprehensive effects of discharge voltage, gas flow rate, and external magnetic field

Atmospheric pressure plasma jet has received widespread attention due to its enormous potential applications in various fields, and its discharge conditions play a key role in changing their physical and chemical properties and ultimately determining its application effectiveness. Factors such as discharge voltage, gas flow rate, and the introduction of an external magnetic field intricately influence the performance of plasma jet. The combined effects of any two of these factors can yield enhanced outcomes, while also bringing complexity to the discharge phenomenon. However, there is currently a lack of research on the combined effects of external magnetic field, discharge voltage, and gas flow rate on the characteristics of plasma jets, making it difficult to comprehensively evaluate the discharge characteristics of plasma jet under multiple discharge conditions. Therefore, this paper focuses on an AC excited atmospheric pressure argon plasma jet and investigates the combined effects of external magnetic field, discharge voltage, and gas flow rate on various characteristic parameters of the plasma jet, including macroscopic morphology, discharge power, gas temperature &lt;i&gt;T&lt;/i&gt;&lt;sub&gt;g&lt;/sub&gt;, electron excitation temperature &lt;i&gt;T&lt;/i&gt;&lt;sub&gt;exc&lt;/sub&gt;, electron density &lt;i&gt;n&lt;/i&gt;&lt;sub&gt;e&lt;/sub&gt;, emission intensity of excited state Ar* particles, and number density of ground state ·OH particles by using methods of camera shooting, and electrical parameter measurement, spectroscopic analysis of emission and absorption spectra. The obtained results are shown below. The effect of discharge voltage on the characteristic parameters of the plasma jet is not affected by gas flow rate or the existence of an external magnetic field. The increase of discharge voltage can improve jet performance by enhancing the discharge power, extending the plasma plume length, elevating the gas temperature &lt;i&gt;T&lt;/i&gt;&lt;sub&gt;g&lt;/sub&gt; and electron excitation temperature &lt;i&gt;T&lt;/i&gt;&lt;sub&gt;exc&lt;/sub&gt;, increasing the electron density &lt;i&gt;n&lt;/i&gt;&lt;sub&gt;e&lt;/sub&gt; and emission intensity of excited state Ar* particles, as well as the number density of ground state ·OH particles. The addition of an external magnetic field can improve the jet performance without significantly changing the discharge power, and the extent of this improvement is influenced by the mode of magnetic field action. Notably, the enhancement of jet performance is most significant when the magnetic field selectively targets the plasma plume, excluding direct interaction with electrode discharge region. The effect of gas flow rate on jet performance becomes intricate: it is intertwined with the effect of voltage and the effect of external magnetic field. When an external magnetic field is present, excessive voltage and gas flow rate may reduce the number density of ground state ·OH particles generated by plasma jet. This underscores the need for a detailed understanding when optimizing jet performance under various discharge conditions. Simply combining the optimal conditions for each individual factor does not guarantee the achievement of peak jet performance when all three discharge conditions work synergistically. This study presents valuable insights into the discharge characteristics of plasma jet under different discharge conditions, providing guidance for optimizing the performance of plasma jet and promoting the advancement of atmospheric pressure plasma jet technology in different application fields.

Do postoperative hemodynamic parameters add prognostic value for mortality after surgical aortic valve replacement?

BackgroundAlthough various hemodynamic parameters to assess prosthetic performance are available, prosthesis–patient mismatch (PPM) is defined exclusively by effective orifice area (EOA) index thresholds. Adjusting for the Society of Thoracic Surgeons predicted risk of mortality (STS PROM), we aimed to explore the added value of postoperative hemodynamic parameters for the prediction of all-cause mortality at 5 years after aortic valve replacement. MethodsData were obtained from the Pericardial Surgical Aortic Valve Replacement (PERIGON) Pivotal Trial, a multicenter prospective cohort study examining the performance of the Avalus bioprosthesis. Candidate predictors were assessed at the first follow-up visit; patients who had no echocardiography data, withdrew consent, or died before this visit were excluded. Candidate predictors included peak jet velocity, mean pressure gradient, EOA, predicted and measured EOA index, Doppler velocity index, indexed internal prosthesis orifice area, and categories for PPM. The performance of Cox models was investigated using the c-statistic and net reclassification improvement (NRI), among other tools. ResultsA total of 1118 patients received the study valve, of whom 1022 were eligible for the present analysis. In univariable analysis, STS PROM was the sole significant predictor of all-cause mortality (hazard ratio, 1.40; 95% confidence interval, 1.26-1.55). When extending the STS PROM with single hemodynamic parameters, neither the c-statistics nor the NRIs demonstrated added prognostic value compared to a model with STS PROM alone. Similar findings were observed when multiple hemodynamic parameters were added. ConclusionsThe STS PROM was found to be the main predictor of patient prognosis. The additional prognostic value of postoperative hemodynamic parameters for the prediction of all-cause mortality was limited.

Experimental and numerical investigation of the novel downhole intensifier controlled by electromagnetic valve

Stress release with rock slotting by ultra-high-pressure water jet is an effective method in reducing rock strength in the bottom hole caused by high in-situ stress in deep formation. The characteristics of duration and frequency of the water jet are vital for forming different grooves to release downhole stress. To improve the duration of the high-pressure water jet and modulate different jet frequency, a kind of downhole intensifier controlled by electromagnetic valve was developed and proposed. The water jet performance and the motion characteristics of the plunger of the intensifier were studied in various input pressure and switch frequency of the electromagnetic valve based on experiments, and a series of numerical simulations were conducted considering the input pressure, stroke, and area ratio of the plunger. The results indicate that the output waveform of the intensifier goes like a square shape. Increasing the input pressure and the area ratio of the plunger can enhance the output pressure while the duration of the peak pressure decreased. The stroke of the plunger shows a significant effect on the duration of the peak pressure and jet frequency. Adjusting the switching frequency of the electromagnetic valve can easily change the duration of peak pressure, which is beneficial for forming grooves with different characteristics. The research is believed to provide an important reference in drilling Engineering for deep and ultra-deep wells.

Noise and Jet Momentum of Synthetic Jet Actuators with Different Orifice Configurations

Sound pressure levels and flow characteristics of a synthetic jet actuator (SJA) are investigated experimentally using the following orifice configurations: a) a slender rectangular slot orifice and b) an array of circular orifices with two different orifice diameters. All configurations have similar total orifice neck area, orifice height, and cavity volume, resulting in a similar Helmholtz frequency. Experiments are conducted for orifices mounted on a flat plate under a quiescent condition. The mean jet velocity exhibits resonant peaks at several excitation frequencies, which also gave rise to the sound pressure levels. The resonant frequencies and peak jet velocities were found to depend on the excitation amplitude and orifice configuration. Investigation of the jet momentum penetration into the quiescent air above the different orifice configurations shows that the momentum issuing from the rectangular slot decays much quicker than that of the circular orifices, irrespective of whether the SJA is excited at resonance or not. The most favorable performance (i.e., the highest momentum in the jet core) was obtained with the array of circular orifices having a smaller orifice diameter, even at off-resonance excitations. The work herein shows the possibility of reducing the SJA noise by 8–10 dB by operating the SJA at a frequency away from the Helmholtz frequency while still achieving comparable levels of jet momentum penetration into the crossflow.

Structural–fluidic–acoustic computational modelling and experimental validation of piezoelectric synthetic jet actuators

In this study, coupled structural–fluidic–acoustic modelling of piezoelectric diaphragm driven synthetic jet actuators is conducted computationally for the first time. The aim is to demonstrate the importance of piezoelectric diaphragm structural modelling and the effects of acoustics coupling to compute accurate synthetic jet exit jet velocity. Two different synthetic jet actuator orifice–diaphragm configurations are studied in which the orifice is parallel and adjacent to the diaphragm, namely, opposite and adjacent synthetic jet actuators, respectively. In investigating the aforementioned configurations, cavity acoustic and mechanical resonance frequencies are identified within ± 100 Hz, compared to in-house experimental measurements of laser vibrometry and hot-wire anemometry. The numerical peak jet velocity differs from the experimental value at the diaphragm mechanical resonance by 5.4% and 0.3% for opposite and adjacent synthetic jets, respectively. Further analysis of velocity and vorticity fields showed that no vortex formation is observed in the cavity of the adjacent synthetic jets, despite having similar exit jet velocity of the opposite synthetic jet configuration.