scholarly journals Study on the initial velocity distribution of exhaled air from coughing and speaking

Chemosphere ◽  
2012 ◽  
Vol 87 (11) ◽  
pp. 1260-1264 ◽  
Author(s):  
Soon-Bark Kwon ◽  
Jaehyung Park ◽  
Jaeyoun Jang ◽  
Youngmin Cho ◽  
Duck-Shin Park ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Initial Velocity ◽  
Initial Velocity Distribution ◽  
Exhaled Air

FLOW FORMS IN A CHANNEL OF SMALL EXPONENTIAL DIVERGENCE

1934 ◽  
Vol 11 (6) ◽  
pp. 770-779 ◽  
Author(s):  
G. N. Patterson
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Initial Velocity ◽  
Reynolds Numbers ◽  
Transitional Region ◽  
Empirical Equations ◽  
Initial Velocity Distribution ◽  
General Flow ◽  
Theoretical Considerations

The motion of air through a channel of small exponential divergence has been investigated experimentally. A flow form derived by Blasius from theoretical considerations has been shown to exist in the range [Formula: see text] for the Reynolds number. The dependence of the general flow form on the initial velocity distribution where the divergence begins has been studied. It has been found that when this initial velocity distribution is parabolic, indicating a laminar motion in the throat of the channel, the flow form is symmetrical. Further investigations have shown that when the initial velocity distribution indicates that the motion near the walls in the throat of the channel lies in the transitional region between a laminar and a turbulent flow, then the flow form is unsymmetrical. Empirical equations have been obtained which give (1) the initial velocity distribution in the transitional region at R = 75.1, and (2) the motion near the walls where the divergence begins for Reynolds numbers lying in the range [Formula: see text].

On the geometry of simple germs of co-rank 1 maps from ℝ3 to ℝ3

1996 ◽  
Vol 119 (3) ◽  
pp. 469-481 ◽  
Author(s):  
W. L. Marar ◽  
F. Tari
Keyword(s):  
Vector Field ◽  
Velocity Distribution ◽  
Density Distribution ◽  
Initial Velocity ◽  
Critical Values ◽  
Time Dependent ◽  
Positive Density ◽  
Interacting Particles ◽  
Initial Velocity Distribution ◽  
Initial Motion

In this paper we investigate the geometry of simple germs of co-rank 1 maps from ℝ3 to ℝ3. Those of co-dimension 1 have already been dealt with by several authors. In [2], V. I. Arnold considered the problem of evolution of galaxies. For a medium of non-interacting particles in ℝ3 with an initial velocity distribution v = v(x) (and a positive density distribution), the initial motion of particles defines a time-dependent map gt: ℝ3 → ℝ3 given by gt(x) = x + tv(x). At some time t singularities occur and the critical values of gi correspond to points of condensation of particles. Arnold assumed the vector field v is a gradient, that is v = ∇S, for some potential S. J. W. Bruce generalized these results in [4] by dropping the assumption on the velocity distribution and studied generic 1-parameter families of map germs F: ℝ3, 0 → ℝ3, 0.

An Experimental and Numerical Study of Turbulent Swirling Pipe Flows

1998 ◽  
Vol 120 (1) ◽  
pp. 54-61 ◽  
Author(s):  
R. R. Parchen ◽  
W. Steenbergen
Keyword(s):  
Angular Momentum ◽  
Velocity Distribution ◽  
Initial Velocity ◽  
Transport Model ◽  
Numerical Study ◽  
Second Order ◽  
Initial Velocity Distribution ◽  
Pipe Flows ◽  
Swirl Generator ◽  
Rate Of Decay

Both experimental and numerical studies have been performed aimed at the description of the decay of swirl in turbulent pipe flows. Emphasis is put on the effect of the initial velocity distribution on the rate of decay. The experiments show that, even far downstream of the swirl generator, the decay of the integral amount of angular momentum depends on the initial velocity distribution. This suggests that the description of the decay in terms of the widely suggested single exponential, function, is not sufficient. The calculations are based on (i) a standard k – ε model and (ii) models based on an algebraic transport model for the turbulent stresses. It appears that in a weakly swirling pipe flow, second-order models reduce to simple modifications of the standard k – ε model. While the standard k – ε model predicts a decay largely insensitive to the initial velocity distribution, the modified versions of the k – ε model, the ASM and the RSM, predict a strong sensitivity to the initial velocity distribution. Nevertheless, the standard k – ε model seems to predict the rate of decay of the swirl better than the second-order models. It is concluded that the corrections for the streamline curvature introduced by the second-order closures, largely overestimate the effect of rotation on the radial exchange of angular momentum.

Concerning some Solutions of the Boundary Layer Equations in Hydrodynamics

1930 ◽  
Vol 26 (1) ◽  
pp. 1-30 ◽  
Author(s):  
S. Goldstein
Keyword(s):  
Boundary Layer ◽  
Velocity Distribution ◽  
Initial Velocity ◽  
Fractional Power ◽  
Initial Distribution ◽  
Initial Velocity Distribution ◽  
Boundary Layer Equations ◽  
Boundary Wall ◽  
First Case ◽  
Made In

The boundary layer equations for a steady two-dimensional motion are solved for any given initial velocity distribution (distribution along a normal to the boundary wall, downstream of which the motion is to be calculated). This initial velocity distribution is assumed expressible as a polynomial in the distance from the wall. Three cases are considered: first, when in the initial distribution the velocity vanishes at the wall but its gradient along the normal does not; second, when the velocity in the initial distribution does not vanish at the wall; and third, when both the velocity and its normal gradient vanish at the wall (as at a point where the forward flow separates from the boundary). The solution is found as a power series in some fractional power of the distance along the wall, whose coefficients are functions of the distance from the wall to be found from ordinary differential equations. Some progress is made in the numerical calculation of these coefficients, especially in the first case. The main object was to find means for a step-by-step calculation of the velocity field in a boundary layer, and it is thought that such a procedure may possibly be successful even if laborious.The same mathematical method is used to calculate the flow behind a flat plate along a stream. The results are shown in Figures 1 and 2, drawn from Tables III and IV.

scholarly journals Ship Twin-propeller Jet Model used to Predict the Initial Velocity and Velocity Distribution within Diffusing Jet

2019 ◽  
Vol 23 (3) ◽  
pp. 1118-1131 ◽  
Author(s):  
Jinxin Jiang ◽  
Wei-Haur Lam ◽  
Yonggang Cui ◽  
Tianming Zhang ◽  
Chong Sun ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Initial Velocity

The propagation of a sound pulse in the presence of a semi-infinite open-ended channel. I

1950 ◽  
Vol 242 (854) ◽  
pp. 527-556 ◽  
Keyword(s):  
Velocity Distribution ◽  
Asymptotic Behaviour ◽  
General Formula ◽  
Initial Velocity ◽  
Sound Pulse ◽  
Arbitrary Direction ◽  
The Third ◽  
Diffracted Waves ◽  
Unit Pulse ◽  
Operational Methods

The behaviour of a sound pulse approaching and progressing beyond the open end of a semi­ infinite channel is discussed. A succession of diffracted waves is created at the open end for which a general formula is obtained, by operational methods, when the pulse originates inside the channel. With the aid of a simple reciprocity relation the asymptotic behaviour of these diffracted waves can be used to deduce the form of the wave returning along the channel when the original pulse approaches the open end from an arbitrary direction. Ultimately the returning wave becomes sensibly plane and separates into regions of length equal to the width of the channel, the form of the potential depending on the number of diffracted waves which contribute to each particular region. Explicit expressions are obtained for the potential in the first two regions at the head of the returning wave and for the third region when the pulse originates inside the channel. The case of an initial velocity distribution given by the Heaviside unit pulse is treated in detail.

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