CFD for Ballast Water & Bio-fouling Management · CFD for Ballast Water & Bio-fouling ... CFD for...
Transcript of CFD for Ballast Water & Bio-fouling Management · CFD for Ballast Water & Bio-fouling ... CFD for...
CFD for Ballast Water & Bio-fouling Management
Vivek V. RanadeCatalysis, Reactors & Separation Unit (CReST)
Chemical Engineering DivisionNational Chemical Laboratory
Pune 411008
OUTLINE
• Ballast Water & Bio-fouling Management– Key issues
• Computational Fluid Dynamics
CFD for Ballast Water & Bio-fouling Management
– 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
CFD for Ballast Water & Bio-fouling Management
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
CFD for Ballast Water & Bio-fouling Management
• 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
CFD for Ballast Water & Bio-fouling Management
• UV
• Ultrasonic Cavitation• Hydrodynamic Cavitation
Pressure profiles, mixing
BALLAST WATER/ BIO-FOULING
• Filling/ draining: water hammer• Sloshing• Cleaning: high velocity jets• Mixing/ exchange/ ballast water treatment
CFD for Ballast Water & Bio-fouling Management
g g• Corrosion
– Microbial– Flow assisted
• Film formation: stability & break-up• Valves/ diodes/ piping circuit• Handling large quantities of water/ complex protocols
BALLAST WATER/ BIO-FOULING
• Detailed Modeling of Fluid Dynamics is Essential
• Conventional Methods– Analytical fluid mechanics
Restricted to very simple flows
CFD for Ballast Water & Bio-fouling Management
• 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
CFD for Ballast Water & Bio-fouling Management
– 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
CFD for Ballast Water & Bio-fouling Management
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
CFD for Ballast Water & Bio-fouling Management
– 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
CFD for Ballast Water & Bio-fouling Management
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
CFD for Ballast Water & Bio-fouling Management
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
CFD for Ballast Water & Bio-fouling Management
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)
CFD for Ballast Water & Bio-fouling Management
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
CFD for Ballast Water & Bio-fouling Management
From Eames et al., Mar. Pollut. Bull. (2007), doi:10.1016/j.marpolbul.2007.10.032
TYPES OF BALLAST TANKS
Hopper Upper Wing
CFD for Ballast Water & Bio-fouling Management
pp pp gBallast Tank
J-type side Ballast Tank
Regular Double Bottom tank
DOUBLE BOTTOM BALLAST TANK
1.5 m
CFD for Ballast Water & Bio-fouling Management
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
CFD for Ballast Water & Bio-fouling Management
inlet
Single port