Prediction of Broadband Noise from Symmetric and Cambered Airfoils

Aerodynamic sound generation and self-noise mechanisms from lifting surfaces such as airfoil involve the fields of classical acoustics and fluid mechanics. In this paper, trailing edge noise production is evaluated using empirical model for NACA 0012 and NACA 6320 airfoils. The sound pressure levels from trailing edge surface are calculated for different flow configurations. The growth of boundary layer thickness and displacement thickness, for different chord lengths and Mach numbers with varying angles of attack, is illustrated for NACA 0012. The sound pressure levels were computed numerically between 00 to 60 angles of attack and at constant chord length of 1.2m using Brookes Pope Marcolini method. The results showed a change of ~2-5dB in peak amplitude for mid frequencies region of spectrum. The effects of varying chord length and Mach number on sound pressure levels are illustrated for both airfoils. The relative velocity field for airfoils was computed using the boundary element method. The combined effect of thickness and camber on sound power level is demonstrated at a 40 angle of attack and for a Mach number of 0.191. Validation of sound pressure levels is done based on the results obtained for NACA0012 for similar flow conditions

Numerical study on the hydrate rich sediment behaviour during depressurization

Exploratory studies have been carried out to identify the potential natural gas hydrate reserves for commercially producing gas. While extracting the gas from the hydrate-bearing sediments using various dissociation techniques, there will be a significant loss of strength in these sediments. It is well known that the behavior of gas hydrate sediments is governed by Thermo Hydro Mechanical Chemical ­ THMC coupled process during the gas extraction. Thus, in this study, in order to understand the influence of depressurization at the well-bore and the permeability of the hydrate reservoir on the sediment deformation characteristics, a 2D (plane strain condition) hydrate reservoir is simulated (using a multiphase numerical schema). From the study, it is observed that the flow response, i.e., the rate of change of gas pressure near the well-bore, decreases with the increase in the duration of the extraction. The maximum settlement occurs for reservoirs having low well-bore pressure (higher amount of depressurization) and high intrinsic permeability. Additionally, these same reservoir conditions also lead to maximum cumulative gas production. Thus, the continuous gas extraction results in a highly porous medium that is stabilized primarily due to the geomechanical changes

Trailing Edge Bluntness Noise Characterization for Horizontal Axis Wind Turbines [HAWT] Blades

Wind turbine noise is becoming a critical issue for many offshore and land-based wind projects. In this work, we analyzed trailing edge bluntness vortex shedding noise source for a land-based turbine of size 2 MW and blade span of 38 m using original Brooks Pope and Marcolini (BPM)and modified BPM noise model. A regression-based curve fitting approach has been implemented to predict the shape function in terms of thickness to chord ratio of aerofoils used for blade. For trailing edge height of 0.1% chord, computations for sound power level were done at wind speed of 8 m/s, 17 RPM. The results showed that present approach for thickness correction predicts the noise peak of ∼78dBA at f ∼ 10 kHz which is ∼15dBA lower than that predicted from original BPM. The results were also validated using experiment data from GE 1.5sle, Siemens 2.3 MW turbines with blade lengths between 78 m and 101 m which agreed within 2% at high frequencies, f > 5 kHz. In addition, results from present approach for trailing edge bluntness noise agreed well with modified BPM by Wei et al. at high frequencies, f ∼ 10 kHz where it becomes dominant. The slope of noise curves from present approach, and modified BPM methods are lower when compared with original BPM

Robotic Assisted versus Manual Percutaneous Coronary Intervention - Systematic Review and Meta-Analysis.

INTRODUCTION: Robotics in percutaneous coronary intervention (R-PCI) has been one such area of advancement where potential benefits may include reduced operator radiation exposure, improved outcomes, and reduced rate of adverse events. Limited data exist about the benefits of R-PCI vs. conventional manual PCI (M-PCI). We appraised the latest evidence in the form of a meta-analysis of observational and retrospective studies. METHODS: A comprehensive literature search was performed in PubMed, Embase, and Cochrane to identify relevant clinical studies. Summary effects were calculated using a DerSimonian and Laird random-effects model as the pooled odds ratio or mean differences with 95% confidence intervals. All studies adhering to the inclusion criteria of direct comparisons between R-PCI and M-PCI were evaluated. RESULTS: Seven studies with a total of 2,230 patients were identified. There was significant decrease in the chest-level operator radiation exposure (MD= -442.32; 95% CI = -675.88 to -208.76), fluoroscopy time (MD = -1.46; 95% CI -2.92 to 0.00) and amount of contrast used (MD= -18.28; 95% CI -24.16 to -12.41) in the robotic group as compared to the manual group. PCI time and the procedural success rate was not statistically different between the two groups. Clinical outcomes of major adverse cardiac events, all-cause mortality, and myocardial infarction were not different between the two groups. CONCLUSION: Robotic PCI is associated with reduced operator radiation exposure, fluoroscopy time, and amount of contrast used. While there is a significant reduction in the procedural characteristics with robotic PCI, the clinical outcomes are not different compared to manual PCI. R-PCI is safe and effective with potential benefits to both the operator and the patient simultaneously

Nutrition assessment and MASH severity in children using the Healthy Eating Index

BackgroundPediatric metabolic-associated fatty liver disease (MAFLD) is a global health problem, with lifestyle modification as its major therapeutic strategy. Rigorous characterization of dietary content on MAFLD in children is lacking. We hypothesized an objectively measured healthier diet would positively modulate MAFLD.MethodsDiet was assessed using the Nutrition Data System for Research in children enrolled from 10 tertiary clinical centers to determine the Healthy Eating Index (HEI, 0-100) and individual food components.ResultsIn all, 119 children were included (13.3 ± 2.7 y), 80 (67%) male, 67 (18%) White, and 90 (76%) Hispanic, with an average body mass index Z-score of 2.2 ± 0.5. Diet was classified as low HEI < 47.94 (n = 39), mid HEI ≥ 47.94 and < 58.89 (n = 41), or high HEI ≥ 58.89 (n=39). Children with high HEI (healthier diet) had lower body weight (p = 0.005) and more favorable lipids. Mean serum triglycerides for low, mid, and high HEI were 163, 148, and 120 mg/dL, respectively; p = 0.04 mid versus high, p = 0.01 low versus high. Mean HDL was 38, 41 and 43 mg/dL; p = 0.02 low vs high. Less severe steatosis was noted with added sugar ≤ 10% of calories (p = 0.03). Higher lobular inflammation is associated with a higher percentage of calories from fat (OR (95% CI) = 0.95 (0.91-1.00), p = 0.04).ConclusionsIn children with MAFLD, high HEI is associated with lower body weight and more favorable lipids, while added sugar and fat intake has individual histologic features. Differential consumption of major dietary components may modify both metabolic risk factors and histologic liver injury, highlighting the importance of objective diet assessments in children with MAFLD