Strange drift of passive tracers from horizontal blowing out sources in the atmospheric boundary layer
- Dresden Univ. of Technology, Saxony (Germany)
In the past many scientists running a wind tunnel observed the following strange phenomenon. Plumes blowing out from horizontal sources (with the same momentum as the adjacent flow) and located inside the planar boundary layer, drift stronger towards the ground than described physically by the conventional dispersion equation. This effect occurs clearly in regard to greater surface roughness. If the dispersion by Gauss is used in connection with a term of reflection, the descending of a plume only occurs after the reflection of tracers on the surface, contrary to the observations. On the other hand a dispersion model is used to describe this phenomenon, which depends on height diffusivity coefficients and a power law for the mean velocity profile (Berljand, 1982; Smith, 1957). The aim of the investigation is to provide a contribution to the causes for this phenomenon. The influence of the roughness length is explored more closely for the above named model. The paper studies the properties of basic flow inside the atmospheric boundary layer generated by a wind tunnel with an open test section. The neutral atmosphere over a suburb terrain is modeled. The following presents measurements by hot-wire with a four-wire-probe of the higher, statistical moments related to all three velocities and measurements of concentration by a Flame-Ionization-Detector in an atmospheric boundary layer of the model. In this connection it is of special interest to investigate the skewness of vertical velocity. This quantity is important for the Lagrangian dispersion model.
- OSTI ID:
- 435761
- Report Number(s):
- CONF-951135-; ISBN 0-7918-1755-5; TRN: IM9710%%419
- Resource Relation:
- Conference: 1995 International mechanical engineering congress and exhibition, San Francisco, CA (United States), 12-17 Nov 1995; Other Information: PBD: 1995; Related Information: Is Part Of Proceedings of the ASME Heat Transfer and Fluids Engineering Divisions: Fluid mechanics and heat transfer in sprays; Heat, mass and momentum transfer in environmental flows; Measurement techniques in multiphase flow; Multiphase transport in porous media. HTD-Volume 321; FED-Volume 233; Hoyt, J.W. [ed.] [San Diego State Univ., CA (United States)]; O`Hern, T.J. [ed.] [Sandia National Labs., Albuquerque, NM (United States)]; Presser, C. [ed.] [National Inst. of Standards and Technology, Gaithersburg, MD (United States)] [and others]; PB: 761 p.
- Country of Publication:
- United States
- Language:
- English
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