Split Stream Flow Past a Blunt Trailing Edge with Application to Combustion Instabilities

In shear coaxial injectors, commonly used for cryogenic liquid rocket engines, propellants traveling at different velocities are separated by the inner jet post before they come into contact with each other, mix, and combust. Knowing how the fluids mix and how susceptible they are to hydrodynamic instabilities is paramount for a successful liquid rocket engine. In this study, the wake behind a blunt trailing edge of a long plate, similar to an unwrapped coaxial injector, was studied in a water tunnel. Two fluid streams of different velocities were introduced on opposite sides of the plate. PIV was used to visualize and determine the influence of the velocity ratio of the split stream on the wake behavior. Measurements of the vortex shedding frequency were taken at various velocity ratios and compared with well characterized cases with a uniform free stream. Operating conditions ranged from Reynolds number 6,000 to 22,000 and velocity ratios 0.30 to 1.00

Juglans regia L. tree plantations for wood production in mining area of S. Barbara (AR). Evaluation of N-fixing accessory trees effect

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Split Stream Flow Past a Blunt Trailing Edge with Application to Combustion Instabilities

In shear coaxial injectors, commonly used for cryogenic liquid rocket engines, propellants traveling at different velocities are separated by the inner jet post before they come into contact with each other, mix, and combust. Knowing how the fluids mix and how susceptible they are to hydrodynamic instabilities is paramount for a successful liquid rocket engine. In this study, the wake behind a blunt trailing edge of a long plate, similar to an unwrapped coaxial injector, was studied in a water tunnel. Two fluid streams of different velocities were introduced on opposite sides of the plate. PIV was used to visualize and determine the influence of the velocity ratio of the split stream on the wake behavior. Measurements of the vortex shedding frequency were taken at various velocity ratios and compared with well characterized cases with a uniform free stream. Operating conditions ranged from Reynolds number 6,000 to 22,000 and velocity ratios 0.30 to 1.00

LES-based Study of the Roughness Effects on the Wake of a Circular Cylinder from Subcritical to Transcritical Reynolds Numbers

This paper investigates the effects of surface roughness on the flow past a circular cylinder at subcritical to transcritical Reynolds numbers. Large eddy simulations of the flow for sand grain roughness of size k/D = 0.02 are performed (D is the cylinder diameter). Results show that surface roughness triggers the transition to turbulence in the boundary layer at all Reynolds numbers, thus leading to an early separation caused by the increased momentum deficit, especially at transcritical Reynolds numbers. Even at subcritical Reynolds numbers, boundary layer instabilities are triggered in the roughness sublayer and eventually lead to the transition to turbulence. The early separation at transcritical Reynolds numbers leads to a wake topology similar to that of the subcritical regime, resulting in an increased drag coefficient and lower Strouhal number. Turbulent statistics in the wake are also affected by roughness; the Reynolds stresses are larger due to the increased turbulent kinetic energy production in the boundary layer and separated shear layers close to the cylinder shoulders.We acknowledge “Red Española de Surpercomputación” (RES) for awarding us access to the MareNostrum III machine based in Barcelona, Spain (Ref. FI-2015-2-0026 and FI-2015-3-0011). We also acknowledge PRACE for awarding us access to Fermi and Marconi Supercomputers at Cineca, Italy (Ref. 2015133120). Oriol Lehmkuhl acknowledges a PDJ 2014 Grant by AGAUR (Generalitat de Catalunya). Ugo Piomelli acknowledges the support of the Natural Sciences and Engineering Research Council (NSERC) of Canada under the Discovery Grant Programme (Grant No. RGPIN-2016-04391). Ricard Borrell acknowledges a Juan de la Cierva postdoctoral grant (IJCI-2014-21034). Ivette Rodriguez, Oriol Lehmkuhl, Ricard Borrell and Assensi Oliva acknowledge Ministerio de Economía y Competitividad, Secretaría de Estado de Investigación, Desarrollo e Innovación, Spain (ref. ENE2014-60577-R).Peer ReviewedPostprint (author's final draft

Aeroelastic Flight Data Analysis with the Hilbert-Huang Algorithm

This paper investigates the utility of the Hilbert-Huang transform for the analysis of aeroelastic flight data. It is well known that the classical Hilbert transform can be used for time-frequency analysis of functions or signals. Unfortunately, the Hilbert transform can only be effectively applied to an extremely small class of signals, namely those that are characterized by a single frequency component at any instant in time. The recently-developed Hilbert-Huang algorithm addresses the limitations of the classical Hilbert transform through a process known as empirical mode decomposition. Using this approach, the data is filtered into a series of intrinsic mode functions, each of which admits a well-behaved Hilbert transform. In this manner, the Hilbert-Huang algorithm affords time-frequency analysis of a large class of signals. This powerful tool has been applied in the analysis of scientific data, structural system identification, mechanical system fault detection, and even image processing. The purpose of this paper is to demonstrate the potential applications of the Hilbert-Huang algorithm for the analysis of aeroelastic systems, with improvements such as localized/online processing. Applications for correlations between system input and output, and amongst output sensors, are discussed to characterize the time-varying amplitude and frequency correlations present in the various components of multiple data channels. Online stability analyses and modal identification are also presented. Examples are given using aeroelastic test data from the F/A-18 Active Aeroelastic Wing aircraft, an Aerostructures Test Wing, and pitch-plunge simulation

Prove di potatura su noce (Juglans regia L.) in impianti di arboricoltura da legno

La sperimentazione ha interessato due tipi di interventi cesori: la scoronatura, che prevede l'eliminazione dei rami che superano in altezza la cicatrice della freccia apicale, ed il taglio di ritorno, con l'accorciamento dei rami pi\uf9 bassi di maggiori dimensioni ad una distanza di circa 50 cm dal fusto. La scoronatura ha permesso il mantenimento della dominanza apicale ma non ha evidenziato un maggior numero di ramentti emessi sulla freccia apicale rispetto ai testimoni. Lo sviluppo diametrico dei rami potati con il taglio di ritorno invernale \ue8 stato inferiore rispetto a quello riscontrato sui soggetti non potati. La differenza tra le due prove \ue8 risultata significativa. Inoltre, i rami potati hanno emesso rami di secondo ordine capaci di svilupparsi notevolmente raggiungendo dimensioni paragonabili ai rami di prim'ordine non potati. Il taglio di ritorno sembra quindi utile nel controllo della crescita dei rami di prim'ordine senza provocare riduzioni nello sviluppo dell'albero

Progetto Aero-Termodinamico Di Un Sistema Di Raffreddamento: Analisi Della Procedura

Report of Depart. of Aerospace Eng. of Pisa, DDIA 2004-5, Feb. 2004

A twig canker on Russian olive caused by Phomopsis arnoldiae in Italy.

From the necrotic margin of irregularly shaped cankers on stems and twigs of Russian olive (Eleagnus angustifolia L.) grown in central Italy, Coniothyrium fuckelii Sacc., Penicillium spp., and Phomopsis arnoldiae B. Sutton were isolated. Artificial inoculations were made on stem of 3-year-old, container-grown E. angustifolia seedlings using two isolates each of the three fungi, previously grown on PDA. Controls were treated in the same way but with sterile disks of PDA. Each treatment was replicated with 10 seedlings and incubated in the greenhouse (20 \ub1 2\ub0C, 80% relative humidity, and 12 h of natural light per day). After 30 days, wounds treated with P. arnoldiae showed necrotic lesions that developed into small patches of dead bark that cracked forming cankers. Radial sections through the stem at the canker site showed the presence of mycelium in the vessels, from which P. arnoldiae was reisolated. No disease symptoms or mycelium in the inner tissues were observed in the control plants or in the plants inoculated with the other fungi. The pathogenicity test was repeated twice with the same results. To our knowledge, this is the first report of this disease in Italy

Progetto Aero-Termodinamico di un Sistema di Raffreddamento: Analisi di Sensibilita'

Report of Depart. of Aerospace Eng. of Pisa, DDIA 2004-6, Mar. 2004