Direct numerical simulation of an oblique jet in a particle-laden crossflow

Jet in crossflow is a classic fluid dynamics problem widely studied in the last decades because of the big quantity of natural and industrial processes in which it is encountered (Mahesh in Annu Rev Fluid Mech 45(1):379–407, 2013 [6]). The present study focuses on the interaction between solid suspended particles and gas turbines film cooling that is a commonly used coolant technique aiming at generating a protective film of cold fluid around the blade profile. Effective cooling systems are crucial to increase turbine inlet gas temperature and to protect turbine blade surfaces from the huge thermal stress generated

Water washing of axial flow compressors: Numerical study on the fate of injected droplets

In turbomachinery applications blade fouling represents a main cause of performance degradation. Among the different techniques currently available, online water washing is one of the most effective in removing deposit from the blades. Since this kind of washing is applied when the machine is close to design conditions, injected droplets are strongly accelerated when they reach the rotor blades and the understanding of their interaction with the blades is not straightforward. Moreover, undesirable phenomena like blades erosion or liquid film formation can occur. The present study aims at assessing droplets dragging from the injection system placed at the compressor inlet till the first stage rotor blades, with a focus on droplets impact locations, on the washing process and the associated risk of erosion. 3D numerical simulations of the whole compressor geometry (up to the first rotor stage) are performed by using Ansys Fluent to account for the asymmetric distribution of the sprays around of the machine struts, IGV and rotor blades. The simulations are carried out by adopting the k-ϵ realizable turbulence model with standard wall functions, coupled with the discretephase model to track injected droplets motion. Droplets-wall interaction is also accounted for by adopting the Stanton-Rutland model which define a droplet impact outcome depending on the impact conditions. The induced erosion is evaluated by adopting an erosion model previously developed by some of the authors and implemented in Fluent through the use of a User Defined Function (UDF). Two sets of simulations are performed, by considering the rotor still and rotating, representative of off-line and on-line water washing conditions, respectively. In the rotating simulation, the Multiple Reference Frame Model is used. The obtained results demonstrate that the washing process differs substantially between the fixed and the rotating case. Moreover, to quantify the water washing effectiveness and the erosion risk, new indices were introduced and computed for the main components of the machine. These indices can be considered as useful prescriptions in the optimization process of water washing systems

Influence of turbulence models in the prediction of cavitation occurrence

In the present paper the effect of turbulence models on cavitation occurrence is evaluated by means of numerical simulations on a NACA 66 (MOD) profile. Cavitation will be assessed through the employment of the widely applied Singhal model, based on the use of the Rayleigh-Plesset equation for bubble dynamics description. Two different turbulence models are used to assess the effect of turbulence on cavitation. For this purpose, Scale Adaptive Simulations (SASs) and Transitional Shear Stress Transport (TSST) simulations are carried out on the NACA test case. Results are discussed for two distinct cavitation numbers comparing experimental data and simulations-obtained values of the non-dimensional pressure coefficients. Moreover, temporal trends and Fast Fourier Transformations (FFTs) will be evaluated for the physical quantities of interest, highlighting the main turbulence-induced fluctuating modes. A direct visualization of the cavity breathing phenomenon is then proposed for the severer cavitating condition case

Rapid and non-destructive method to assess in the vineyardgrape berry anthocyanins under different seasonal andwater conditions

Abstract Background and Aims: Monitoring of anthocyanins (Anth) in winegrape (Vitis vinifera L.) is fundamental for the production of top-quality red wines. This work was aimed at testing a new fluorescence-based sensor for Anth detection in the vineyard. Significance of the Study: The present study showed a new important innovative technology for viticulture. The sensor evaluation of the large spatial and temporal heterogeneity in Anth accumulation can be useful as support parameter in the harvest date decision or for vineyard zoning of phenolic maturity. Methods and Results: Anth in grape (cv. Aleatico) bunches attached to the vine were monitored non-destructively in the field using a fluorescence-based sensor during the 2008 and 2009 seasons and under different water regimes. The ANTHRG index = log(far-red-fluorescenceR/far-red-fluorescenceG), with fluorescence signals excited with red (R) and green (G) light, was inversely correlated through an exponential function (r2 = 0.875) to the Anth concentration derived from the HPLC analysis of berry skin extracts. ANTHRG was effective in detecting the earlier ripening process in 2009 with respect to 2008 and differences in the Anth accumulation between seasons and in relation to different water regimes.Water deficit imposed in 2009 enhanced Anth concentration in berries because of a reduction in berry size but also an increase of Anth biosynthesis. This effect was observed by both destructive and ANTHRG non-destructive measurements. Conclusions: Our results show that the employed fluorescence sensor represents a reliable, rapid and non-invasive tool for monitoring and determining Anth accumulation in situ

Role of endogenous opioids on nociceptive threshold in patients with exercise-induced myocardial ischemia.

To evaluate whether endogenous opioids (EO) play a role in the perception of anginal pain, a randomized double blind clinical trial, using naloxone (N) and placebo (P) and measuring beta-endorphin (beta-ep) plasma levels, was performed. We studied 10 patients with angiographically assessed coronary artery disease (CAD) and stable exercise-induced myocardial ischemia (established by 2 preliminary bicycle ergometric tests) of whom 5 symptomatic (SYM) and 5 asymptomatic (ASYM) and 5 subjects without CAD as a control group (CON). On a third exercise test the beta-ep plasma level (fmol/ml) was measured at rest (SYM 5.4 +/- 2.3 vs ASYM 7.2 +/- 2.3 vs CON 6.8 +/- 2.6, NS), at peak exercise (SYM 4.4 +/- 1.8 vs ASYM 8.0 +/- 4.2 and vs CON 6.2 +/- 2.7, NS) and during recovery (SYM 7.5 +/- 4.2 vs ASYM 7.2 +/- 3.0 vs CON 6.7 +/- 2.5, NS). On 2 subsequent tests patients received N (0.2 mg/kg) or P intravenously and chest pain was evaluated on an analogue scale (score from 1 to 10). After N compared to P we observed: an increased perception of chest pain in SYM (6.8 +/- 1.5 vs 4.2 +/- 1.0; p less than 0.01) without significant changes of the ischemic threshold (total work, heart rate-blood pressure product, ST segment changes, 2D-echocardiographic wall motion abnormalities); no modifications in ASYM and CON.(ABSTRACT TRUNCATED AT 250 WORDS

Application of Vis/Nir spectroscopy to establish peach ripening as affected by rootstock

The objective of this paper was to monitor peach ripeness of “Chimarrita” and “Maciel” cultivars, grafted on different rootstocks, using the pulp firmness parameter, as an indicator of harvest time through equipment based on Vis/Nir spectroscopy. The orchard was installed in 2005, has a "V" conduction system with spacing of 5.0 x 1.5 m, and the cultivars are grafted on seven rootstocks: “Capdeboscq”, “Flordaguard”, “Nemaguard”, “Okinawa”, “Tsukuba”, “Umezeiro” and “Viamão”. After harvesting, the fruits were evaluated by the NIR CASE spectrophotometer, establishing categories of pulp firmness, between 40N and 60N for fruits consumed in a long term and <40N for immediate consumption. The analyzed rootstocks alter the peach ripeness of the “Chimarrita” and “Maciel” cultivars. The “Umezeiro” rootstock anticipates harvest for the “Chimarrita” cultivar. The “Nemaguard”/ “Maciel” combination provides fruits with a superior harvest period than the other ones evaluated. The Vis/Nir Spectroscopy is a useful tool to monitor the harvest of “Chimarrita” and “Maciel” cultivars