cfd for ballast water & bio-fouling management · cfd for ballast water & bio-fouling ......

CFD for Ballast Water & Bio-fouling Management

Vivek V. RanadeCatalysis, Reactors & Separation Unit (CReST)

Chemical Engineering DivisionNational Chemical Laboratory

Pune 411008

[email protected]

OUTLINE

• Ballast Water & Bio-fouling Management– Key issues

• Computational Fluid Dynamics


– What is CFD?– Methodology– Sample applications

• Closure

BALLAST WATER/ BIO-FOULING

• Filling/ draining: water hammer• Sloshing• Cleaning: high velocity jets• Mixing/ exchange/ ballast water treatment


g g• Corrosion

– Microbial– Flow assisted

• Film formation: stability & break-up• Valves/ diodes/ piping circuit• Handling large quantities of water/ complex protocols

BALLAST WATER EXCHANGE

• Replace coastal water with open ocean water during a voyage– Emptying and refilling ballast tanks (sequential exchange)– Flow-through dilution/ continuous exchange


• Concerns about – Biological effectiveness– Ship safety and operational issues

• Excess bending moment/ shear stress, propeller immersion, minimum forward draft, sloshing … for sequential exchange

• Flushing by fresh water, stratification, over pressurization … for continuous exchange

SLOSHING

CFD for Ballast Water & Bio-fouling ManagementFrom Lee et al., Ocean Engineering 34 (2007) 3–9

WATER TREATMENT

• Use of Biocides– Mixing of very small quantities in huge volume

• Heat TreatmentUV

Exposure time distribution


• UV

• Ultrasonic Cavitation• Hydrodynamic Cavitation

Pressure profiles, mixing


• Filling/ draining: water hammer• Sloshing• Cleaning: high velocity jets• Mixing/ exchange/ ballast water treatment


g g• Corrosion

– Microbial– Flow assisted

• Film formation: stability & break-up• Valves/ diodes/ piping circuit• Handling large quantities of water/ complex protocols


• Detailed Modeling of Fluid Dynamics is Essential

• Conventional Methods– Analytical fluid mechanics

Restricted to very simple flows


• Restricted to very simple flows– Scale models

• Restricted validity/ difficult to extrapolate• Time consuming/ expensive

• COMPUTATIONAL FLUID DYNAMICS (CFD)

WHAT IS CFD?

• Solution of Mass, Momentum and Energy Balances on Digital Computers

• Major Features


– No restrictive assumptions / approximations– Can handle complex geometry of industrial process equipment– Can incorporate variety of processes simultaneously

• Can lead to:– Accurate insight of underlying fluid dynamics– A bridge between theory and experiments– Process data which can not be obtained from experiments

COMPUTATIONAL FLOW MODELING

• Enhanced understanding of theory through numerical experiments– Bridge between theory and experiments

• Detailed analysis at early stage in design cycle for less money, less risk and less time


less risk and less time

• May provide data which is not possible to obtain experimentally– High pressure/ temperatures– Corrosive conditions

• Screening of alternative design configurations

• Sounds too good to be true ! Is there any catch some where?

COMPUTATIONAL FLOW MODELING

• Uncertainties / Limitations:– Inadequacies of the underlying mathematical model & input data

• Turbulence• Multiphase flows• Complex Rheology• Chemical reactions


– Inaccuracies of the numerical technique (discretisation and round-off errors)

– Computational constraints– Interpretation of results

• Despite the Limitations, CFD has Enormous Potential !

– Necessary to develop appropriate methodology to harness this potential

CReST @ NCL

• Multi-scale Modeling Capabilities to Provide Complete Solutions for Reactor/ Product Engineering

Simulation of Drop Impact on Flat Surface: Understanding wetting


Simulation of Fluidized Bed Reactor: multi-scale approach

Top portion of industrial thermo-siphon loop reactor modeled using hybrid approach

Separate model to simulate erosion of

support hooks

METHODOLOGY

• Development & Creative Use of Computational Models for Better Reactor, Process & Product Engineering


APPLICATIONS

• Optimizing Ballast Water Exchange Strategies

• Ballast Water Treatment Technology– Based on hydrodynamic

cavitation• Modeling of cavitating flows• Devising effective

it ti h b f


cavitating chamber for destruction of microbes

• Adjust number density of cavities and intensity of collapse as per the requirements

– Patented cavitating devices for water dis-infectionJ-type side

Ballast Tank

BALLAST WATER DISPOSAL

• Flow-Through Exchange Method– 300% of a tank’s full capacity of clean water from the deep ocean

must be pumped into each tank to achieve an acceptable 95% volumetric exchange.

• Sequential Exchange (empty / refill)


q g ( p y )– Involves emptying tanks of high-risk ballast water at sea before

refilling them with clean water from the deep ocean.

• Dilution Method– Tank is partially filled and filling deep ocean water will dilute to

original ballast water to 5%

• Exchange to take place no less than 200 nautical miles from coast & at water depth of at least 200 m

FLOW THROUGH EXCHANGE


From Eames et al., Mar. Pollut. Bull. (2007), doi:10.1016/j.marpolbul.2007.10.032

TYPES OF BALLAST TANKS

Hopper Upper Wing


pp pp gBallast Tank

J-type side Ballast Tank

Regular Double Bottom tank

DOUBLE BOTTOM BALLAST TANK

1.5 m


Geometric Details :1. Volume of tank = 410 m3

2. Flow rate = 1000 m3/hr

30 m

9.12 m

sec147641.01000

4103

3

==== hrshr

mm

ratepumpingvolumeTankτ

PORT CONFIGURATIONS

Outlet-1 Outlet-1

Outlet-2


inlet

Single port

cfd for ballast water & bio-fouling management · cfd for ballast water & bio-fouling ......

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