Disk-Outflow Coupling: Energetics Around Spinning BlacK Holes

The mechanism by which outflows and plausible jets are driven from black hole systems still remains observationally elusive. This notwithstanding, several observational evidences and deeper theoretical insights reveal that accretion and outflow/jet are strongly correlated. We model an advective disk-outflow coupled dynamics, incorporating explicitly the vertical flux. Inter-connecting dynamics of outflow andaccretion essentially upholds the conservation laws. We investigate the properties of the disk-outflow surface and its strong dependence on the rotation parameter of the black hole. The energetics of the disk outflow strongly depend on the mass, accretion rate, and spin of the black holes. The model clearly shows that the outflow power extracted from the disk increases strongly with the spin of the black hole, inferring that the power of the observed astrophysical jets has a proportional correspondence with the spin of the central object. In the case of blazars (BL Lacs and flat spectrum radio quasars, FSRQs), most of their emission are believed to be originated from their jets. It is observed that BL Lacs are relatively low luminous than FSRQs. The luminosity might be linked to the power of the jet, which in turn reflects that the nuclear regions of the BL Lac objects have a relatively low spinning black hole compared to that in the case of FSRQs. If extreme gravity is the source that powers strong outflows and jets, then the spin of the black hole, perhaps, might be the fundamental parameter to account for the observed astrophysical processes in an accretion powered system.

An experimental study of suddenly expanded rectangular jet flow field

Flow through a rectangular Passage which is expanded suddenly into another rectangular duct of larger Cross-sectional area has been studied experimentally with stagnation Pressures from 3.5 atmospheres to 1.25 atmospheres. The length to height ratio of the enlarged duct varied from 5.769 to 1.923 and three models with length to height ratios 5.769, 3.846, and 1.923 were studied. The influence of stagnation Pressures and length to height ratio of the enlarged duct on base pressure and flow field mean pressures in the enlarged duct is discussed. The results of the present investigation indicate that the oscillatory nature of the mean pressure flow field in the enlarged portion with rectangular cross-section is appreciably different from that for circular cross-section at similar flow conditions.

Absorption of Electromagnetic Waves in Astrophysical Plasmas

We study parametric Decay Instabilities (PDI) using the kinetic description, in the homogeneous and unmagnetic plasmas. These instabilities cause anomalous absorption of the incident electromagnetic (e.m) radiations. The maximum plasma temperatures reached are functionas of luminocity of the non-thermal radio radiation and the plasma parameters.

Radio wave heating of astrophysical plasmas

The coherent plasma process such as parametric decay instability (PDI) has been applied to a homogeneous and unmagnetized plasma. These instabilities cause anomalous absorption of strong electromagnetic radiation under specific conditions of energy and momentum conservation and thus cause anomalous heating of the plasma. The maximum plasma temperatures reached are functions of luminosity of the radio radiation and plasma parameters. We believe that these processes may be taking place in many astrophysical objects. Here, the conditions in the sources 3C 273, 3C 48 and Crab Nebula are shown to be conducive to the excitation of PDI. These processes also contribute towards the absorption of 21cm radiation

Abrasive Jet Machining - Process variables and current applications

brusive Jet Machining (AJM) or Micro Blast Machining is a non-traditional machining process, wherein material removal is effected by the erosive action of a high velocity jet of a gas, carrying fine-grained abrasive particles, impacting the work surface. The AJM process differs from conventional sand blasting in that the abrasive is much finer and the process parameters and cutting action are carefully controlled. The process is particularly suitable to cut intricate shapes in hard and brittle materials which are sensitive to heat and have a tendency to chip easily. In other words, AJM can handle virtually any hard or brittle material. Already the process has found its ways Into dozens of applications; sometimes replacing conventional alternatives often doing jobs that could not be done in any other way. This paper reviews the current status of this non-conventional machining process and discusses the unique advantages and possible applications.

Jet interaction in liquid-liquid coaxial injectors

Interaction between two conical sheets of liquid formed by a coaxial swirl injector has been studied using water in the annular orifice and potassium permanganate solution in the inner orifice. Experiments using photographic techniques have been conducted to study the influence of the inner jet on outer conical sheet spray characteristics such as spray cone angle and break-up length. The core spray has a strong influence on the outer sheet when the pressure drop in the latter is low. This is attributed to the pressure variations caused by ejector effects. This paper also discusses the merging and separation behavior of the liquid sheets which exhibits hysteresis effect while injector pressure drop is varied.

Water Modeling Study Of The Jet Characteristics In A Continuous-Casting Mold

The jet characteristics and the fluid flow pattern in a continuous slab caster have been studied using a water model. The fluid jet is studied under free fall and submerged discharge conditions. In the latter case, the jet was followed by dye-injection technique and image analyser was used to find out the effect of nozzle parameters on jet-spread angle, jet-discharge angle and the volume entrainment by the jet. All free-fall jets with nozzle port angle zero and upward are found to be spinning. Some of the free-fall jets with downward nozzle-port angle are found to be spinning and rest are smooth. The spinning direction of the jets are found to change with time. The well depth, port diameter and the inner diameter of the nozzle have a clear effect on the free-fall jets with downward port angle. The jet-spread angle is found to be about 17-degrees for smooth jets. The spread angle for spinning jet increases as the nozzle-port angle is increased from downward 25 to upward 15-degrees. The jet-discharge angle is always downward even when the nozzle-discharge ports are angled upward. The extent of volume entrainment by the spinning jet is higher and it increases as the nozzle-port angle is increased from 25 downward to 15-degrees upward.

Data rectification and detection of trend shifts in jet engine path measurements using median filters and fuzzy logic

Filtering methods are explored for removing noise from data while preserving sharp edges that many indicate a trend shift in gas turbine measurements. Linear filters are found to be have problems with removing noise while preserving features in the signal. The nonlinear hybrid median filter is found to accurately reproduce the root signal from noisy data. Simulated faulty data and fault-free gas path measurement data are passed through median filters and health residuals for the data set are created. The health residual is a scalar norm of the gas path measurement deltas and is used to partition the faulty engine from the healthy engine using fuzzy sets. The fuzzy detection system is developed and tested with noisy data and with filtered data. It is found from tests with simulated fault-free and faulty data that fuzzy trend shift detection based on filtered data is very accurate with no false alarms and negligible missed alarms.

Noise and outlier removal from jet engine health signals using weighted FIR median hybrid filters

The removal of noise and outliers from measurement signals is a major problem in jet engine health monitoring. Topical measurement signals found in most jet engines include low rotor speed, high rotor speed. fuel flow and exhaust gas temperature. Deviations in these measurements from a baseline 'good' engine are often called measurement deltas and the health signals used for fault detection, isolation, trending and data mining. Linear filters such as the FIR moving average filter and IIR exponential average filter are used in the industry to remove noise and outliers from the jet engine measurement deltas. However, the use of linear filters can lead to loss of critical features in the signal that can contain information about maintenance and repair events that could be used by fault isolation algorithms to determine engine condition or by data mining algorithms to learn valuable patterns in the data, Non-linear filters such as the median and weighted median hybrid filters offer the opportunity to remove noise and gross outliers from signals while preserving features. In this study. a comparison of traditional linear filters popular in the jet engine industry is made with the median filter and the subfilter weighted FIR median hybrid (SWFMH) filter. Results using simulated data with implanted faults shows that the SWFMH filter results in a noise reduction of over 60 per cent compared to only 20 per cent for FIR filters and 30 per cent for IIR filters. Preprocessing jet engine health signals using the SWFMH filter would greatly improve the accuracy of diagnostic systems. (C) 2002 Published by Elsevier Science Ltd.

Turbulence measurements in an ‘equilibrium’ axisymmetric wall jet Journal

This paper reports measurements of turbulent quantities in an axisymmetric wall jet subjected to an adverse pressure gradient in a conical diffuser, in such a way that a suitably defined pressure-gradient parameter is everywhere small. Self-similarity is observed in the mean velocity profile, as well as the profiles of many turbulent quantities at sufficiently large distances from the injection slot. Autocorrelation measurements indicate that, in the region of turbulent production, the time scale of ν fluctuations is very much smaller than the time scale of u fluctuations. Based on the data on these time scales, a possible model is proposed for the Reynolds stress. One-dimensional energy spectra are obtained for the u, v and w components at several points in the wall jet. It is found that self-similarity is exhibited by the one-dimensional wavenumber spectrum of $\overline{q^2}(=\overline{u^2}+\overline{v^2}+\overline{w^2})$, if the half-width of the wall jet and the local mean velocity are used for forming the non-dimensional wavenumber. Both the autocorrelation curves and the spectra indicate the existence of periodicity in the flow. The rate of dissipation of turbulent energy is estimated from the $\overline{q^2}$ spectra, using a slightly modified version of a previously suggested method.