CERC — Environmental Software and Services

ADMS iconTrainingFeature comparisonDownload icon

ADMS 5

World leading software for modelling industrial air pollution

Model options

ADMS 5 include the following options:

Sketch of ADMS features

Plume rise, source buoyancy and momentum[top]

ADMS 5 uses a Runge-Kutta method to solve the conservation equations to estimate plume rise. This allows greater scope to include advanced model options than Briggs empirical expression used in other Gaussian type models. The ADMS 5 method takes into account the effect on the plume of the source buoyancy and momentum, and includes the penetration of boundary layer inversions.

Dry and wet deposition[top]

The rate of dry and wet deposition to the ground can be modelled in ADMS 5. Dry deposition is assumed to be proportional to the near-surface concentration, and deposition velocities can either be entered by the user, or estimated by the model. Wet deposition is modelled through a washout coefficient; irreversible uptake is assumed, and plume strength following wet deposition decreases with downwind distance. There is also an advanced 'falling drop' option for wet deposition of SO2 and HCl which calculates the rate of dissolution and/or degassing in rain drops

Plumes or puffs[top]

ADMS 5 can model both continuous releases, i.e. plumes, in addition to instantaneous and time-dependent releases, i.e. puffs.

Time varying emissions[top]

Emission rates from industrial sources are rarely constant. The variation of the emission rate with time can be modelled in ADMS 5, in addition to corresponding variations in emission temperature, volume flow rate (or exit velocity), source diameter, and plume water content.

Dispersion around buildings[top]

Sketch of building flow

The building effects module in ADMS 5 includes the following features.

Up to 25 buildings can be included in each model run with a Main Building being defined for each source. For each wind direction, a single effective wind-aligned building is defined, around which the flow is modelled.

The flow field consists of a recirculating region (or cavity), with a diminishing turbulent wake downstream.

Concentrations within the cavity, CR, are uniform, and based on the fraction of the release that is entrained. The concentration at a point further downwind is the sum of contributions from two plumes: a ground-based plume from the recirculating flow region and an elevated plume from the non-entrained remainder. The concentration and deposition are set to zero within the user-defined buildings.

Odours[top]

Odours are an important issue in areas where industrial sites are located close to residential areas. The dispersion of odours can modelled using ADMS 5. Odour release rates and concentrations can be specified/calculated in two types of odour units: ou, which are defined in the form of a ratio, and ouE which are a mass measure.

Fluctuations[top]

ADMS 5 is the only regulatory model of its kind to model short time scale fluctuations allowing the calculation of the probability distributions of pollutant concentrations, probabilities of exceedence of specified threshold, and the range of concentration for averaging time as little as a second. The module has applications where estimates of the occurrence of peaks of concentration over short averaging times are important (e.g. odours, flammable & toxic accidental, 15 minute air quality objective for SO2). The module takes into account variations due to both turbulence and changes in meteorology.

Plume visibility[top]

The plume visibility module uses the initial water content of the release and the humidity of the ambient air to determine whether the plume will be visible due to condensed water droplets at each downstream distance. The effect of water on the plume density and the heating and cooling effects of condensation and evaporation are taken into account.

NOx chemistry[top]

The chemistry scheme in ADMS 5 considers the following fast reactions involving NOx and ozone (O3) to determine the NO2 concentration in the dispersing plume(s):

NO + O3NO2 + O2

and a reverse reaction (day time only, hν depends on UV radiation intensity)

3 NO2 + hν → 3 NO + O3

Model validation has shown the method to more accurate than empirically based formulations.

Amine chemistry[top]

An advanced model option allows for chemical reactions of amine to form nitramines and nitrosamines. The module has been developed as a consequence of emerging technologies for Carbon Capture and Storage (CCS) some of which are based on amine extraction of CO2.

Radioactive decay and γ-ray dose[top]

ADMS 5 includes a radioactivity module that predicts the decay of radioactive species released from a source. Users may enter up to 10 parent isotopes in any model run, and up to 50 isotopes (parents and daughters) will be output. Half-lives of over 800 isotopes are included in the model and ADMS 5 can also calculate the associated levels of γ-ray dose.

Dispersion in coastal areas[top]

Sketch of coastline module

For air dispersion modelling in coastal areas, ADMS 5 includes a coastline module to take account of increasing boundary layer height when airflow is from the sea to the land. It may be invoked when the following conditions are satisfied:

  • the sea is colder than the land;
  • there are convective meteorological conditions on land;
  • there is an onshore wind.

Flow over complex terrain[top]

Image of modelled propagation of a plume

ADMS 5 uses CERC's FLOWSTAR, to calculate how the mean airflow and turbulence and hence dispersion and pollutant concentrations are changed over complex terrain.

The model predicts a three-dimensional flow and turbulence field over the region of interest, dependent on input values for the spatial variation of both the terrain height and surface roughness, as well as the local meteorological conditions.

It is recommended that the complex terrain option in ADMS 5 be used in regions where the gradient exceeds 1:10 but does not exceed 1:3 over large areas of the model domain.

Impact of wind turbines on dispersion[top]

The model can allow for the effect on dispersion of one or more horizontal-axis three-bladed wind turbines in the neighbourhood of an emission source.

Link to AERMOD[top]

There is a facility to run the main options of AERMOD to allow the option of using the AERMET meteorological processor.

Next page>



© CERC 2021. All rights reserved. Legal disclaimer.

This site uses cookies to store user preferences about visual presentation.

Display: [Normal] [High contrast] [Printer-friendly]