Poojitha D. Yapa

Poojitha D. Yapa
Professor
130 Rowley Laboratories
Clarkson University
PO Box 5710
Potsdam, NY 13699-5710

Phone: 315-268-7980
FAX: 315-268-7985
E-mail: pdy@clarkson.edu
Research Site

Education
Ph.D. - Clarkson University, Potsdam, NY, 1983
M.Eng. - Asian Institute of Technology, Bangkok, Thailand, 1979
B.Sc. Eng. (Honors) - University of Moratuwa, Sri Lanka, 1976

Teaching
CE 574 Hydrodynamic Dispersion
CE 572 Shallow Water Hydrodynamics
CE 330 Water Resources Engineering I
ES 330 Fluid Mechanics
ES 220 Statics
CE 301 Engineering Measurements

Research Interests
Modeling of deep water oil and gas jets/plumes, Modeling of surface oil spills, Modeling physico-chemical processes oil undergo in ocean conditions, Modeling Geothermal Vents underwater, Modeling CO2 and CH4 hydrate in deepwater, Oil transport and spread in ice covered waters, Impact on the ecosystem due to oil spills, Sediment plumes and their effect on the ecosystem, Web based model systems, Integration of GIS and oil spill models

Vistiting Appointments
January to June 2007 Erskine Fellow, Department of Civil Engineering, University of Canterbury, Christchurch, New Zealand,
June-July 2004 Visiting Researcher, School of Marine Science, Tokai University, Shizuoka, Japan, on leave from Clarkson University
1999 to 2000 Visiting Professor / Gledden Senior Visiting Fellow, Centre for Water Research, The University of Western Australia, Perth, Australia,
Sep. 1992 to Aug. 1993 Invited Research Fellow, Department of Civil Engineering, Science University of Tokyo, Japan.
June to Aug. 1992 Visiting Researcher, Environmental Assessment Dept., National Inst. for Resources and Environment, Tsukuba, Japan.

Models Developed (selected)
CDOG (Comprehensive Deepwater Oil and Gas) Model
CDOG developed at Clarkson University by Prof. Yapa and his students was the model used by NOAA to simulate the behavior of oil during the recent Horizon deep water spill in the gulf of Mexico.

CDOG simulates the behavior of oil and gas accidentally released from deep water. This is a three-dimensional model. In deepwater, the ultra-high pressure and cold temperature causes phase changes in gasses. These effects combined with deepwater currents in some regions presents extraordinary challenges to modeling jets/plumes from deepwater oil and gas blowouts.

The following processes are considered in CDOG model: phase changes of gas, associated changes in thermodynamics and its impact on the hydrodynamics of the jet/plume. Hydrate formation, hydrate decomposition, gas dissolution, non-ideal behavior of the gas, and the jet/plume hydrodynamics and thermodynamics.

CDOG can take 3-D currents, salinity, water temperature (hence water density) that varies both spatially and temporally. CDOG model has been used to numerically simulate the large scale and unique field experiments conducted in Norway at a cost of US $2.5 million. The field experiments consisted of two oil and methane gas releases and one methane gas only release from a deepwater location (844 m water depth). The comparisons between the simulations and the observations are good. CDOG model has also been used to simulate various anticipated deepwater blowout scenarios. It can be and has been used during real emergencies and for contingency planning.

MEGADEEP (Methane Gas in Deepwater) Model
MEGADEEP is a three-dimensional computational model specifically designed to simulate the transport and fate of gasses (methane and natural gas) and hydrates accidentally released in deepwater. It takes the following processes into account:  Mass conservation, hydrodynamics and thermodynamics of the plume (dynamic phase), Advection/Diffusion of the plume (passive phase), Possible gas separation from the plume, Gas dissolution, Hydrate formation and dissociation; Hydrate dissolution, Cracking and reformation of   hydrate shells, Gas bubble breakup and coalescence.

MEGADEEP simulations compare well with the data from  "Deespill" large scale field experiments and deepwater gas experiments conducted in Monterey Bay, CA.

SPEED   (Sediment Plume and Environmental Effect from Deep-sea Mining)
SPEED model is a three-dimensional numerical model which can simulate sediment plumes released upwards (due to momentum of the mining tool) or downwards at a higher up release station. Both near-field dynamics phase and far-field passive advection-diffusion phase are considered. In the near field, the model is based on a Lagrangian integral control volume technique; for the far field, the Lagrangian parcel method is applied. Both fixed source and moving source releases can be handled by the model. The effects of different particle sizes, sediment concentration and flocculation on settling velocities are taken into account. A multiple grid scheme is applied when the mining domain is very large or mining time is very long.

In addition to the sediment transport, the model simulates the chemical distribution due to sediment transport, estimates the mortalities of benthos due to deposited sediment and assesses the effects on photosynthesis due to sediment plume. The model is able to handle heavy metals, organic chemicals, nutrients and minerals. The partitions of chemicals between water and sediment are considered. The mortality of benthos is calculated based on LC50 and first order kill rate. The effect on photosynthesis of sediment plume in the euphotic zone is estimated based on the relationship between photo-synthetically active radiation and net primary productivity.

COMBOS3D (Three-Dimensional Comprehensive Oil Spill Model for Surface and Underwater spills)
This is a three-dimensional model that can simulate surface water oil spills or oil spills that originate as jets or plumes underwater. COMBOS3D model can simulate fate and transport of oil after a spill. It considers the following processes: Advection, Horizontal Diffusion, Spreading, Vertical mixing (3-D Dispersion in water column), Evaporation, and Dissolution. It can also simulate the behavior of oil gas mixtures from under water. The model has been extensively tested against available data. The comparisons between the model simulations and experiments were excellent, and can be found in Zheng and Yapa (1998) and Yapa et. al (1999).

COMBOS3D can simulate oil spills from moving sources such as a broken ship that keeps moving after an accident. For simulating oil processes such as emulsification, oil-sediment interactions and photo-oxidation see our model DEPOSE.

COMBOS3D has been used in many practical applications: Oil spills in Japan including potential spills in Tokyo Bay, and Prestige spill simulation (off the coast of Spain and Portugal).

DEPOSE    (A Model for simulating Dissolution, Evaporation, Photo-Oxidation, Sedimentation, and Emulsification after an oil spill)
This model simulates the physical-chemical behavior of oil after a spill. In addition to advection/ diffusion, and vertical mixing of oil DEPOSE simulates oil Emulsification, Oil- sediment interaction, Evaporation, Dissolution, and Photo-oxidation.

SHIP LEAK     (A Model to Simulate Oil Leaks form Sunken Ships)
This is simplified version of COMBOS3D specifically designed to simulate oil leaks from sunken ships. It has the capability of handling ship leaks from deep water. Ship leak model is capable of handling multiple releases with different starting times. Further, it has the ability to simulate the leaks from moving ships.

WINROSS - An Integrated Oil and Chemical Spill Model For the St. Lawrence River Oil Spill Response
This is based on our River Oil Spill Simulation Model (ROSS). WinROSS is designed to run under windows. It is completely interactive and GUI Menu based. Data input, running the models (flow model an oil spill model), and output visualization all can be done from the GUI. The model is two-dimensional and has two-layers (surface and water column). It uses the Lagrangion Parcels Method. The model was originally designed and implemented as an integrated part of the St. Lawrence River Oil Spill Preparedness Plan and used by the St. Lawrence Seaway Development Corporation.

ROSS2 is a 2-Dimensional 2-Layer Model was developed specifically for River Oil Spill Simulation. ROSS has been applied to St. Clair, St. Mary's, Detroit, and St. Lawrence Rivers. ROSS2 of was applied to Ohio-Monangahela-Allegheny river system.  See our publications for details.

Selected Publications
Yapa, P.D. (2010). "Coastal Pollution due to Oil Spills," in H. J. S. Fernando (ed) , Handbook of Environmental Fluid Dynamics, Taylor & Francis Books Inc., (in progress).

Yapa, P. D,  Dasanayaka, L. K., Bandara, U. C., and Nakata, K. (2010).  "A Model to Simulate the Transport and Fate of Gas and Hydrates Released in Deepwater, Journal of Hydraulic Research, IAHR. (accepted for publication)

Dasanayaka, L. K., and Yapa, P. D. (2009). "Role of Plume Dynamics on the Fate of Oil and Gas Released Underwater," Journal of Hydro-Environment Research, IAHR/Elsevier, March, 243-253

Nakata, K., Yapa, P. D, Dasanayaka, L. K.,  Bandara, U. C., and Suzuki, S. (2008). "Shinkaiiki  kara rouhi ni shite methan gasu kyodou soku modaruno kaihatsu -in Japanese (English translation : A Model for Methane gas in Deepwater)," Aquabiology, Seibutsu Kenkyusha, Tokyo, Japan, August, Vol. 30., No. 4.

Xie, H., Yapa, P. D., and Nakata, K. (2007) "Modeling Emulsification after an Oil Spill in the Sea,"  Journal of Marine Systems, Elsevier, 68 (2007), 489-506.

Chen, F.H. and Yapa, P. D., (2007). "Estimating the Oil Droplet Size Distributions in Deepwater Oil Spills," Journal of Hydraulic Engineering, ASCE, February, Vol. 133. No. 2,  197-207

Xie, H. and Yapa, P. D. (2006) "Developing A Web-Based System For Large Scale Environmental Hydraulics Problems With An Application To Oil Spill Modeling, , Journal of Computing in Civil Engineering, ASCE,  May, Vol. 20 (3), 197-209.

Chen, F.H, Yapa, P. D., and Nakata, K. (2004). "Simulating the Biological Effect of Oil Spills in Tokyo Bay by Using A Coupled Oil Spill - Toxicity Model," Journal of Advanced Marine Science Technology, AMTEC, Tokyo, Japan, 9(2), 131-155.

Xie, H. and Yapa, P.D. (2003). "Simulating the Behavior and the Environmental Effect of Sediment Plumes from Deepwater Mining," Journal of Advanced Marine Science Technology, AMTEC, Tokyo, Japan, 9(1), 7-35.

Chen, F.H. and Yapa, P.D. (2004). "Modeling Gas Separation From a Bent Deepwater Oil and Gas Jet/Plume," Journal of Marine Systems, Elsevier, the Netherlands, Vol 45 (3-4), 189-203

Zheng, L., Yapa, P. D., and Chen, F.H. (2003). "A Model for Simulating Deepwater Oil and Gas Blowouts - Part I: Theory and Model Formulation" Journal of Hydraulic Research, IAHR, August, 41(4), 339-351

Chen, F.H. and Yapa, P.D. (2003). "A Model for Simulating Deepwater Oil and Gas Blowouts - Part II : Comparison of Numerical Simulations with "Deepspill" Field Experiments", Journal of Hydraulic Research, IAHR, August,  41(4), 353-365

Zheng, L. and Yapa, P.D. (2002). "Modeling Gas Dissolution in Deepwater Oil/Gas Spills," Journal of Marine Systems, Elsevier, the Netherlands, March, 299-309

Yapa, P. D., Zheng, L, and Chen, F.H. (2001). "A Model for Deepwater Oil/Gas Blowouts," Marine Pollution Bulletin, The International Journal for Marine Environmental Scientists/Engineers, Elsevier Science Publications, UK, Vol. 43, No. 7, 234-241.

Chen, F.H. and Yapa, P.D. (2001). "Estimating Hydrate Formation and Decomposition of Gases Released in a Deepwater Ocean Plume," Journal of Marine Systems, Elsevier, the Netherlands, Vol. 30/1-2, 21-32

Zheng, L. and Yapa, P.D. (2000). "Buoyant Velocity of Spherical and Non-Spherical Bubbles/ Droplets," Journal of Hydraulic Engineering, ASCE,  November, 852-855

Yapa, P.D., Zheng, L., and Nakata, K. (1999). "Modeling Underwater Oil/Gas Jets and Plumes," Journal of Hydraulic Engineering, ASCE, May, 481-491

Yapa, P.D., and Weerasuriya, S.A., (1997). "Spreading of Oil Spilled under Floating Broken Ice," Journal of Hydraulic Engineering, ASCE, August,  676-683.

Yapa, P.D. (editor and contributor), (1996). "State-of-the-Art Review of Modeling Transport and Fate of Oil Spills," by the ASCE Task Committee on Modeling of Oil Spills, Journal of Hydraulic Engineering, ASCE, Double Length Paper, November, 594-609.

Yapa, P.D., Zheng, L., and Kobayashi, T., (1996). "Application of Linked-List Approach to Pollutant Transport Models," Journal of Computing in Civil Engineering, ASCE,  Vol. 10 (1), January 88-90.

Yapa, P.D., (1994). "Oil Spill Processes and Model Development," Journal of Advanced Marine Technology, AMTEC, Tokyo, Japan, March, 1-22.

Yapa, P.D., Shen, H.T., and Angammana, K., (1994). "Modeling Oil Spills in a River-Lake System," Journal of Marine Systems, Elsevier, the Netherlands, March, 453-471.

Weerasuriya, S.A., and Yapa, P.D., (1993). "Uni-directional Spreading of Oil under Solid Ice," Canadian Journal of Civil Engineering, February, 50-56.

Yapa, P.D., and Chowdhury, T., (1990). "Spreading of Oil Under Ice Covers," Journal of Hydraulic Engineering, ASCE, December, 1468-1483.