Dense jet assessment procedure

HR Wallingford has long experience of the assessment of dilution and dispersion of positively-buoyant marine discharges from, for example, power stations and refineries. However, increasingly, assessments of negatively-buoyant discharges are required, particularly for:
• Saline discharges from proposed desalination plants.
• Saline discharges from salt cavern leaching operations.
• Cold discharges from Liquefied Natural Gas (LNG) regasification plants.
Studies of dense discharge dispersion usually involve two-stage approaches: a near-field dilution assessment, based on mixing zone software, such as CORMIX; and a mid- to far-field dilution/dispersion assessment to check longer-term build-up of background concentrations, such as can be carried out using a three-dimensional (3D) advection-diffusion model, for example TELEMAC-3D. HR Wallingford has developed an assessment procedure for undertaking such two-stage analyses of dense discharges, which can be used until the application of fully coupled near- and far-field models becomes practical.
This paper considers current modelling techniques, identifies alternative approaches where appropriate, and presents the above assessment procedure for the analysis of dense discharge dispersion and dilution.
The dense jet assessment procedure was established in the light of experience, and after review of previous studies. Work undertaken recently by various authors is summarised in the early sections of this paper, to introduce an example application of the assessment procedure presented in the later sections.