Continuous Release

The continuous release profile extends from the source downwind (Fig. E.1). An elevated, heavy vapour/aerosol release starts out with a circular cross section. Upon touching down, the cross section becomes a truncated ellipse, and the cloud levels off as the vertical component of momentum is converted into downwind and cross-wind momentum. Aerosol droplets may rain out shortly after touchdown. Rain-out produces a pool which spreads and vaporises. If spilled onto water, part of the material may also dissolve. The vapour from the pool is added back to the plume, as a function of time. The plume can become buoyant after evaporating all aerosol droplets and picking up heat by ground conduction, or by condensing water picked up over a wet surface. A buoyant plume lifts off and rises until constrained by the mixing layer.

The Cartesian co-ordinates x, y, z correspond to the downwind, cross-wind (lateral horizontal) and vertical directions, respectively; x=0 corresponds to the point of release, y = 0 to the plume centre-line and z = 0 to ground-level. In addition to these cartesian co-ordinates use is made of the 'cloud' coordinates s and Z Here s is the arclength measured along the plume centre, with s=0 corresponding to the point of release. The concentration profile for continuous release (Plume) is given by [203; 9]:



Fh( y) = exp-

(y )


p us ys z

V2S y



V2s z

and and oy, = standard deviation of horizontal profile of cloud concentration (m)

oz, = standard deviation of vertical profile of cloud concentration (m)

y = the crosswind distance from the cloud axis (m)

Z = distance from Plume center-line (m)

circular cross-section truncated cross-section circular cross-section truncated cross-section

Fig. E.1 UDM cloud geometry for continuous release [203]

The co-ordinate Z indicates the direction perpendicular to the plume centre-line and perpendicular to the y-direction. The angle between the plume centre-line and the horizontal is denoted by 0 = 0(s), and the vertical plume height above the ground by z0 = zcid(s). Thus z and Z are related to each other by z = zcld + Z cos(0).

Was this article helpful?

0 0
Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

Get My Free Ebook

Post a comment