Search results for "Outflow"
showing 10 items of 111 documents
A new approach for deducing the stage-discharge relationship of triangular in plan sharp-crested weirs
2013
Abstract In this paper, the outflow process of a triangular in plan sharp-crested weir is studied using the dimensional analysis and the incomplete self-similarity theory. The new stage-discharge is theoretically deduced and its testing is carried out using measurements available in literature.
X-ray Emission from Protostellar Jets
2008
Long-term FRII jet evolution: Clues from three-dimensional simulations
2018
We present a long-term numerical three-dimensional simulation of a relativistic outflow designed to be compared with previous results from axisymmetric, two-dimensional simulations, with existing analytical models and state-of-art observations. We follow the jet evolution from 1~kpc to 200~kpc, using a relativistic gas equation of state and a galactic profile for the ambient medium. We also show results from smaller scale simulations aimed to test convergence and different three-dimensional effects. We conclude that jet propagation can be faster than expected from axisymmetric simulations, covering tens of kiloparsecs in a few million years, until the dentist drill effect produced by the gr…
The nearest X-ray emitting protostellar jet (HH 154) observed with Hubble
2008
Context. The jet coming from the YSO binary L1551 IRS5 is the closest astrophysical jet known. It is therefore a unique laboratory for studies of outflow mechanisms and of the shocks occurring when expanding material hits the ambient medium as well as of how the related processes influence the star- (and planet-) forming process. Aims. The optical data are related to other data covering the spectrum from the optical band to X-rays with goal of understanding the energetics of low-mass star jets, in general, and of this jet in particular. We study the time evolution of the jet, by measuring the proper motions of knots as they progress outwards from the originating source. Methods. The nebulos…
The nearest X-ray emitting protostellar jet observed with HST
2009
The HH 154 jet coming from the YSO binary L1551 IRS5 is one of the closest (about 150 pc) astrophysical jet known. It is therefore a unique laboratory for studies of outflow mechanisms and of the shocks forming at the interaction front between the expanding material and the ambient medium. The substructures (knots) observed within the HH 154 jet were imaged in several spectral bands using the Hubble Space Telescope. This allows us to derive a simple characterization of the physical conditions in different structures as well as to measure the proper motion of the knots in the jet, their flux variability and shock emission over a time base of about ten years. These knots in the jet undergo si…
Experimental Study of the Stage-Discharge Relationship for an Upstream Inclined Grid with Longitudinal Bars
2013
AbstractIn this paper, the outflow process of an upstream inclined grid with longitudinal bars is studied by using the dimensional analysis and the incomplete self-similarity theory. Next, the theoretical analysis shows that a power equation can be used for establishing the stage-discharge equation. The coefficient and an exponent of the power equation depend on the slope angle and the void ratio. Finally, this new stage discharge is tested by using measurements obtained by laboratory runs conducted in this investigation.
Closure to “Experimental Study of the Stage-Discharge Relationship for an Upstream Inclined Grid with Longitudinal Bars” by C. Di Stefano and V. Ferro
2014
The discusser would like to thank the authors of the original paper for investigating the outflow process of an upstream inclined grid with longitudinal bars using the dimensional analysis and the incomplete self-similarity theory. The discusser, however, would like to add a few points. Using the theoretical analysis the authors of the original paper showed that a power equation can be used for establishing the stage-discharge equation of an upstream inclined grid with longitudinal bars. The authors of the original paper also showed that the coefficient and exponent of the power equation depend on the slope angle and the void ratio. They proposed a stage-discharge equation
New stage-discharge relationship for inclined non-rectangular weirs
2018
Abstract In this paper, the outflow process of inclined non-rectangular weirs is studied applying the dimensional analysis and the incomplete self-similarity theory. At first, a new stage-discharge equation, applicable for the non-rectangular weirs having a different geometrical shape (parabolic, semicircular, inverted semicircular), is theoretically deduced using a characteristic width. Then, this power stage-discharge relationship (Eq. (17) ) is calibrated and tested using measurements carried out by Raiknar for parabolic, semicircular and inverted semicircular weirs having different inclination respect to the vertical (10°, 20°, 30°, 40° and 45°). For each geometrical shape, the analysis…
The kinematics of water masers in the stellar molecular outflow source, IRAS 19134+2131
2004
Using the Very Large Array (VLA) and the Very Long Baseline Array (VLBA), we have observed water maser emission in the proto-planetary nebula candidate IRAS 19134+2131, in which the water maser spectrum has two groups of emission features separated in radial velocity by ∼100 km s^−1. The blue-shifted and red-shifted clusters of maser features are clearly separated spatially by ∼150 mas, indicative of a fast collimated flow. However, not all of the maser features are aligned along the axis of the flow, as is seen in the similar high-velocity water maser source, W43A. Comparing the VLA and VLBA maps of the water maser source, we find 4 maser features that were active for 2 years. Using only V…
In silico pace-mapping: prediction of left vs. right outflow tract origin in idiopathic ventricular arrhythmias with patient-specific electrophysiolo…
2019
Abstract Aims A pre-operative non-invasive identification of the site of origin (SOO) of outflow tract ventricular arrhythmias (OTVAs) is important to properly plan radiofrequency ablation procedures. Although some algorithms based on electrocardiograms (ECGs) have been developed to predict left vs. right ventricular origins, their accuracy is still limited, especially in complex anatomies. The aim of this work is to use patient-specific electrophysiological simulations of the heart to predict the SOO in OTVA patients. Methods and results An in silico pace-mapping procedure was designed and used on 11 heart geometries, generating for each case simulated ECGs from 12 clinically plausible SOO…