Biomedical subjects

Robin K S Hankin

Publications and source records attributed to Robin K S Hankin.

3 recordsLinked to original sources

PubMed2003

Shallow layer simulation of heavy gas released on a slope in a calm ambient. Part I. Continuous releases.

Although much research considers heavy gas dispersion over flat ground, less is known about the physics of dense gas dispersion on a slope. Here, the appropriateness of shallow layer models for the simple case of releases over a slope in a calm ambient is assessed. This two-part paper assesses the value of shallow layer modelling using the established shallow layer model TWODEE [J. Hazard. Mater. 66 (3) (1999) 211; J. Hazard. Mater. 66 (3) (1999) 227; J. Hazard. Mater. 66 (3) (1999) 239] and the experimental results of Schatzmann et al. [M. Schatzmann, K. Marotzke, J. Donat, Research on continuous and instantaneous heavy gas clouds, contribution of sub-project EV 4T-0021-D to the final report of the joint CEC project, Technical Report, Meteorological Institute, University of Hamburg, February 1991]. Part I considers continuous releases, and part II considers instantaneous releases; both use the same model with the same entrainment coefficients. For continuous releases, cloud arrival times are generally well predicted, and cloud concentrations are generally correct to within a factor of two. Shallow layer models thus appear to be capable of physically accurate simulation of continuous releases over a slope in a calm ambient.

Diffusion↗

PubMed2003

Shallow layer simulation of heavy gas released on a slope in a calm ambient. Part II. Instantaneous releases.

This paper assesses the value of shallow layer modelling for instantaneous releases of heavy gas over a slope using the established computer model TWODEE [R.K.S. Hankin, Heavy gas dispersion over complex terrain, Ph.D. thesis, Cambridge University, 1997; J. Hazard. Mater. 66 (1999) 211; J. Hazard. Mater. 66 (1999) 227; J. Hazard. Mater. 66 (1999) 239] and the experimental results of Schatzmann et al. [M. Schatzmann, K. Marotzke, J. Donat, Research on continuous and instantaneous heavy gas clouds, Contribution of sub-project EV 4T-0021-D to the final report of the joint CEC project, Technical report, Meteorological Institute, University of Hamburg, February 1991]. This is the second of a two-part paper; part I considered continuous releases using the same model, using the same entrainment parameters. Schatzmann et al. carried out instantaneous releases of heavy gas over three slopes; each experiment was repeated five times under nominally identical conditions. The goodness-of-fit measures (GFMs) of Hanna et al. [Atmos. Environ. 27A (15) (1993) 2265] are generalized to account for the multiple releases carried out by Schatzmann et al. Using these statistical GFMs, predicted peak concentrations are generally correct to within a factor of two; and cloud arrival times are generally late.

Air Pollutants↗

PubMed2003

Heavy gas dispersion: integral models and shallow layer models.

Integral models for heavy gas dispersion approximate a dispersing cloud in terms of a small number of variables; each of these is ultimately a function of an independent variable which is usually time (instantaneous releases) or downwind distance (continuous releases). This type of model is used almost exclusively in risk assessment [HSE's risk assessment tool, RISKAT, in: Major Hazards: Onshore and Offshore, October 1992, pp. 607-638; Ann. Rev. Fluid Mech. 21 (1989) 317], but many distinct integral models exist. The code comparison exercise of Mercer et al. [CEA/AEA exchange agreement on external event. Comparison of heavy gas dispersion models for instantaneous releases: final report, Technical Report IR/L/HA/91/6, Health and Safety Laboratory, Sheffield, June 1991; J. Hazard. Mater. 36 (1994) 193] presented the results from a number of integral models in a common format; Mercer found that the range of predictions for some scenarios exceeded three orders of magnitude. Here, the TWODEE shallow layer model [J. Hazard. Mater. 66 (3) (1999) 211; J. Hazard. Mater. 66 (3) (1999) 227; J. Hazard. Mater. 66 (3) (1999) 239] is added to Mercer's code comparison exercise. The physical assumptions used in shallow layer models differ profoundly from those used in integral models and the implications of these differences for risk assessment are discussed. TWODEE was used to simulate four representative cases considered by Mercer. In terms of cloud averaged concentration (CAC) vs. centroid position, the present model gave predictions that were consistent with the integral models used by Mercer. As the model neglects horizontal diffusion for passive clouds, overprediction at large downwind distances was expected, but not generally observed.

Air Pollutants↗