Outflows high velocity

We assume the velocity of the jet s outflow into the air to be small. If this velocity is large enough, then stability of the jet s surface will be influenced by the dynamics of the environment, in particular, the forces of viscous fiiction and the change of pressure. Therefore, breakup of high-velocity jets has a different character. Indeed, a jet flowing out into a gas with a small velocity breaks up into rather large drops, while at a high velocity of outflow it breaks up into a set of fine drops of various sizes. 

In the present eonfiguration, air inlet boundaries are assumed to be Pressure Inlet while outflow boundaries are assumed Pressure Outlet . Pressure inlet boundary conditions were used to define the total pressure and other scalar quantities at flow inlets. Pressure outlet boundary conditions were used to define the static pressure at flow outlets. At the nozzle inlet, the air pressure was varied. At the nozzle outlet, the pressure was supposed to be the external pressure (one atmosphere). At the wall of the nozzle standard wall function boundary condition was applied. Although the high velocity of air stream was a heat source that will increase the temperature in the nozzle, the nozzle length was very short and the process oecurs in a very short time. For simplification, it was assumed that the process is adiabatic i.e. no heat transfer occurred through walls. The flow model used was viscous, compressible airflow [1, 6-10]. The following series of equations were used to solve a compressible turbulent flow for airflow simulation [1,6-12] ... 

FIGURE 18 Illustration of the formation of a P Cygni profile (emission line near the rest wavelength, with blue-shifted absorption) in a spectral feature, resulting from high-velocity outflow of gas from a stellar atmosphere. 

Figure 2 shows 2fon spectra with wider coverage than Fig. 1. Ih the four central sources the 2.06 line is stronger than HI Bry. Althou this could be interpreted in terms of normal He/H, two pieces of evidence suggest otherwise. First, the normally weak He I 4-3 blend at 2.113/mi is about one-third the strength of H 1 Br7(2.166/mi). In nebulae with He/H=0.1 where helium is nearly hilly He H, this ratio is no greater than 0.1. Second, each Bry line has a blue shoulder (especially prominoit in IRS 15NE and IRS 15SW). While this could be interpreted as a very high velocity outflow whose bade side is obscured, it can also be imderstood as emission from He I Bry components. The strongest of these are blueshifted with respect to HI Bry by 200 and 700 km/sec. However, the lines are too weak and too blended to provide an accurate estimate of the intensity ratios.

The ladk of extended Br 7 emission may be explained by the high obscuration of IRS 1 and no high velocity shocks in the outflow. Tamura and Yamashita (1992) interpret their H2 S(l) 1-0 and HI Br 7 observations in terms of a J-shock excitation model by McKee and HoUenbach (1984) where a fast YSO wind impacts ambient molecular material, causing dissociation, ionization, and recombination emission. Tamura and Yamashita apply the McKee and HoUenbach model and predict shock velodties of 100 km s which correspond to FWZI Br 7 line widths of 200 km s . Our CSHELL Br 7 spectrum shows FWZI values of Av = 30 km s, fax bdow the line widths required to produce the line flux observed by Tamura and Yamashita. Furthermore, the observed widths correspond to shock velocities of only 15 km s, not frtst enough to be an ionizing J-shock. 

Figure 2. shows our 2.122 on narrow-band image superimposed on the velocity integrated J=2-l CO contour maps of the outflow. Figure 2a shows the relationship to the extremely high velocity (57 10 km/s with respect to the cloud) CO contours, while 2b shows the blue-shifted lobe integrated from Vlsr = -60 to 0 km/s... 

Figure 3.9 Stratification-circulation diagrams used to describe a spectrum of circulation and geomorphometric types of estuaries that can be defined by stratification. Estuarine types are as follows Type 1 estuaries are those without upstream flow requiring tidal transport for salt balance Type 2 estuaries are partially mixed (e.g., Marrows of the Mersey (NM) (UK), James River (J) (USA), Columbia River estuary (C) (USA) Type 3 estuaries are representative of fjords [e.g., Siver Bay (S), Strait of Juan de Fuca (JF) (USA)] and Type 4 estuaries indicative of salt wedge estuaries [e.g., Mississippi River (M) (USA)]. The basic classification parameters are as follows the stratification is defined by SS/Sq where SS is the difference in the salinity between surface and bottom water and So is the mean-depth salinity, both averaged over a tidal cycle and Us/Uf, where U is the surface velocity (averaged over a tidal cycle) and Uf is the vertically averaged net outflow. The subdivisions a and b represent values where SS/Sq <0.1 and SS/Sq >0.1, respectively subscripts h and 1 refer to high and low river flow. The curved line at the top represents the limit of surface freshwater outflow. (From Hansen and Rattray, 1966, as modified by Jay et al., 2000, with permission.)...

Figure 2.11 The HH-30 object, a young stellar object showing two thin jets flowing out from the central region of an accretion disk. The outflow velocity in the jets is 90-270 km s-1. The two bowl-shaped regions are starlight scattered by the dust in the uppermost layers of the disk. The dark lane in between is the accretion disk seen side-on. The radial optical depth in the disk is too high for starlight to penetrate in this direction. The radial extension of the disk is 425 AU. (Photo credit Hubble Space Telescope, NASA/ESA and STScI.)...

Inlet swirl inflow conditions are discussed below. The outflow boundary conditions at the combustor outlet involve advection of all flow and species variables with Uc, where the instantaneous mean streamwise outlet boundary velocity Uc is periodically renormalized to ensure that the time-averaged mass flux coincides with that at the inlet these convective boundary conditions are enforced in conjuction with soft relaxation of the outflow pressure to its ambient value. Two types of outlets were considered (Fig. 11.1). Viscous wall regions in the combustor cannot be practically resolved for the moderately-high Reynolds... 

In the case of highly mobile interface between dispersed phase and dispersion medium (as in foams and emulsions) the condition of zero fluid flow velocity at interface (non-slip condition), determining the validity of Reynolds equation, may not be obeyed. In this case the decrease in the film thickness occurs at a greater rate. However, in foam and emulsion films stabilized by surfactant adsorption layers the conditions of fluid outflow from an interlayer are close to those of outflow from a gap between solid surfaces even in cases when surfactant molecules do not form a continuous solid-like film. This is the case because at surfactant adsorption below Tmax the motion of fluid surface leads to the transfer of some portions of surfactant adsorption layer from central regions of film to peripherical ones, adjacent to the Gibbs-Plateau channels. As a result, the value of adsorption decreases in the center of film, but increases at the periphery, which stipulates the appearance of the surface... 

Particle velocity effects. Particle velocity can cause Doppler broadening of spectral lines. The effect is extremely small for interstellar clouds at 10 K but is appreciable for clouds near high temperature stars. Outflows of gas from pulsing stars exhibit a red Doppler shift when moving away at high speed and a blue shift when moving toward us. 

At a high level of superheat the liquid evaporates completely within a stable and stationary evaporation discontinuity at the liquid surface. This expansion discontinuity is a deflagration with sonic outflow velocity (Chapman-Jouget condition). The evaporation rate at the surface is given by gas... 

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