Hydrodynamic `modelling of Large-Scale Cooling Water Outfalls ...

Hydrodynamic modelling of large-scale cooling water outfalls with a dynamically coupled near field – far field modelling system ICDEMOS 2014 Robin Morelissen, Deltares

16 april 2014

Introduction

Increasing amount of coastal activities/industries that use and discharge water world-wide; power plants, desalination plants, waste water outfalls, etc.

1 - Impact on the environment and need to comply with

EIA criteria and regulations 2 - The design needs to be optimised for

efficient/economic operation (e.g. recirculation) Therefore, it is necessary to be able to assess the outfall

plume behaviour accurately, e.g. by means of numerical modelling

16 april 2014

Modelling outfalls

Outfall plume behaviour over different scales; close to outfall (turbulence, metres) to effects/impacts kilometres away (large scale ambient flow)

No single model can cover these different scales efficiently and

accurately

Source: MEDRC, Dr.-Ing. Tobias Bleninger & Prof. G.H. Jirka, Ph.D. and Domenichini et al.

16 april 2014

Coupling models

Cover different time and space scales by coupling near field and far field models

Coupling methods: - No coupling (direct insertion, undiluted source) - One-way, fixed near field solution - One-way, time-varying near field solution - Two-way, dynamic near field – far field coupling

Source: Choi & Lee 2007

Source: Bleninger 2006

Development of the Delft3D-CORMIX coupling

Coupling Delft3D with CORMIX: − physically suitable location for coupling to the far field model (including

boundary interaction) − include many different outfall configurations and flow conditions that

are included in CORMIX. Intermediate zone

Near-field

Far-field

Current Plume boundary

Near-field plume centreline

Typical coupling location

Preferred coupling location

DESA

Working principle dynamically coupled models

Run several time steps in far field model (Delft3D)

Translate ambient conditions to near field model

Run near field model (CORMIX)

Translate near field model results to far field model (DESA)

Case Study - Application of coupled modelling system

• New large submerged outfall diffusers and submerged intakes

• Existing surface outfalls


Design criteria in the Case Study: 1 – Minimised extent of the +1°C temperature contour at

the surface 2 – Safe design of intake, i.e. most conservative

temperature increase at the submerged intakes

Physical phenomena in field data and reproduced by coupled model 1 - Varying location where plume surfaces due to tide

Validation of coupled modelling system

Physical phenomena in field data and reproduced by coupled model 2 - Surface excess temperature in non-stratified conditions

(+1.5°C at surface instead of +4°C in traditional (not coupled) modelling approach)


18°C

~19.5°C

Coupled

Traditional

Physical phenomena in field data and reproduced by coupled model 3 - Plume visibility at the surface and colder plume at the surface

(under stratified ambient conditions)


Physical phenomena in field data and reproduced by coupled model 4 – More realistic vertical mixing and safer prediction of intake temperature


Conclusions

Coupling of near and far field models is required to accurately and efficiently assess the characteristics of the outfall plume on all spatial scales

Validation: observed physical phenomena in field data and reproduced

by coupled model (and not in traditional modelling methods) The dynamically coupled modelling approach can make a substantial

difference in the development of plants - Environmental impact not overestimated (smaller footprint) - Safer design intake (for intake temperature)

16 april 2014

Round Table Discussion – Tuesday

16 april 2014

Questions?

Contact information: Robin Morelissen, Deltares

[email protected]

Hydrodynamic `modelling of Large-Scale Cooling Water Outfalls ...

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