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Poojitha D. Yapa

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

Phone: 315-268-7980
FAX: 315-268-7985
Research Site

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

CE 574 Hydrodynamic Dispersion
CE 572 Shallow Water Hydrodynamics
CE 595 Computing Algorithms for Water Resources Problems
CE 430 Water Resources Engineering II
CE 330 Water Resources Engineering I
ES 330 Fluid Mechanics
ES 220 Statics
CE 301 Engineering Measurements

Research Interests
Modeling deep water oil and gas jets/plumes, Modeling surface oil spills, Modeling physico-chemical processes that oil undergo in ocean conditions, Modeling Hydrothermal Vents in deepwater, Modeling CO2 and CH4 hydrates in deepwater, Oil transport and spread in ice covered waters, Oil and Gas droplet sizes in water, 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

Short Narrative Biography
Poojitha D. Yapa, a Professor of Civil and Environmental Engineering at Clarkson University, Potsdam, NY, USA has B.Sc (Honors) in Civil Engineering and M.Sc in Hydraulic engineering. He received his Ph.D. in Civil and Environmental Engineering from Clarkson University. His research has focused on “environmental hydraulics problems”. For over 25 years his research has been focused on oil spill modeling. This includes not only trajectory modeling, but modeling physico-chemical processes that oil undergo when spilled in the ocean or rivers. In the last 15 years his modeling has been on deepwater oil, gas, and hydrates, studying the complex processes they undergo during the travel from deepwater to the surface. Prof. Yapa and his students developed computer models such as CDOG, MEGADEEP, and ADMS for modeling the behavior of oil and gas when released in deepwater. The work has been published in leading journals.
Prof. Yapa received the prestigious Erskine fellowship from New Zealand and Gledden Fellowship from Australia for long term visits to their Universities. He has also been invited to Universities in Japan, Portugal, Singapore, and Sri Lanka for extended stays. He has given over 50 invited seminars in 9 countries. He has numerous publications in leading Hydraulic Engineering and research journals and has been the associate editor of hydraulic journals of American Society of Civil Engineers (ASCE) as well as the International Association of Hydraulic Research (IAHR). Prof. Yapa chaired the Task Committee on Modeling of Oil Spills formed by the ASCE. He was a member of the advisory committee to NOAA on GNOME Model. He was also a member of Task Committee on Best Practices in Oil Spill Modeling, CRRC/NOAA. During the Horizon oil spill Gulf of Mexico Prof. Yapa was invited by The US government to be an adviser to NOAA on Deepwater plumes as well as a member of the Flow Rate Task Group (FRTG) that calculated the oil discharge rate. International Association of Hydraulic Research (IAHR) appointed Prof. Yapa to be the chair of a most recently formed Task group to look into oil spill related research problems. He received United States Geological Services (USGS) director’s award for exemplary services to the nation for the work he did during 2010 Deepwater Horizon oil spill response.

Visiting Appointments
Jan. to June 2007 Erskine Fellow, Department of Civil Engineering, University of Canterbury, Christchurch, New Zealand,
June to July 2004 Visiting Researcher, School of Marine Science, Tokai University, Shizuoka, Japan
Aug. 1999 to June 2000 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)
ADMS ~pronounced  ˈadams’ -(Advanced Deepwater Modeling Suite)
ADMS consists of a suite of models/modules to simulate the fate and transport of oil, gas, and hydrates when released from shallow to ultra-deep water. The simulations allow gas hydrate formation, dissociation as well as hydrate dissolution. The suite includes CDOG, MEGADEEP and several unnamed modules. In addition to simulating oil, gas, hydrates allowed by CDOG, the ADMS suite allows multiple gas bubbles, separation of gas at different levels, self-calculation of bubble sizes based on newly published research (Bandara and Yapa 2011), bubble break up and coalescence during transport. The models also simulate the transport and fate of dissolved gas and its impact on oxygen depletion. The Advanced capabilities modules can do the following
•    Calculating the oil droplet size and gas bubble size distribution
•    Simulating bubble/droplet break up and coalescence simulation during deepwater simulations for oil and gas
•    Multiple gas bubble sizes in simulations (original CDOG considered only one gas bubble size)
•    Gas and hydrate dissolution and tracking the transport and dispersal of dissolved gas

MOHTV ~pronounced 'mō-tiv’  (Model for Hydrothermal Vents)
MOHTV is a model developed to simulate the behavior of underwater hydrothermal vent plumes. Physical, Chemical, and Biological processes take place in hydrothermal vents due to the discharge of hot water rich in minerals. MOHTV models these processes to determine the quantities of chemicals produced their spread in the ocean water column, and the extent of their spread on the ocean floor.  The model is 3-dimensional and can take time and spatially varying conditions into account. It takes hydrodynamics and thermodynamics into account together with physico-chemical reactions that take place. The model simulation results are compared with available field data. The model has also been used to simulate the formation, transport, and deposition of minerals at a few sites in the Pacific Ocean. Biological processes are expected to be incorporated into the model at a later time. The biological processes are expected to further affect the overall behavior of the plume including the distribution of mineral particles and production of chemicals.

CDOG ~pronounced 'sea dog’  (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 2010 Horizon deepwater 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 the water density) that varies both spatially and temporally. CDOG model has been used to numerically simulate the large scale and unique field experiments (Deepspill) 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. The results of these simulations have been published in a series of technical papers in leading journals (see this site and the our own research website for the list).  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  "Deepspill" large scale field experiments and deepwater gas experiments conducted in Monterey Bay, CA. See Yapa et al. (2010)

OCEAN_CO2 Modeling the Ecological Impact of CO2 Releases in ocean waters
OCEAN_CO2 is developed to simulate the ecological impact due to CO2 gas releases from moderate ocean depths. It can simulate CO2 releases from a single point, or releases spread over an area (non-point source). The model uses multi-species Lagrangian parcels approach to model CO2 in both gas and dissolved gas phases (i.e. the changes in the gas released as well as the changes in the ambient water due to the dissolved gas). OCEAN_CO2 calculates dissolved CO2 concentration, pH, and TCO2 in water. Model results comparisons are done with data from natural CO2 releases in Kagoshima Bay, Japan and they are reasonably good.

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 the 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 Rivers
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. GUI allows user to input data, run the models (flow model and oil spill model), and visualize output. The model is two-dimensional and has two-layers (surface and water column). It uses the Lagrangian 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. ROSS has been applied to St. Clair, St. Mary's, Detroit, and St. Lawrence Rivers. ROSS2 is a 2-Dimensional 2-Layer version of ROSS. It can simulate the oil transport and spread on the water surface as well as water column. ROSS2 was applied to Ohio-Monangahela-Allegheny river system.  See our publications for details.

Selected Publications
Yapa, P.D. (2012). “Modeling Oil Spills to Mitigate Coastal Pollution,” in H. J. S. Fernando (ed) , Handbook of Environmental Fluid Dynamics, Taylor & Francis Books Inc., Dec., 243-255.
Yapa, P. D., Wimalaratne, M. R., Dissanayake, A. L., and De Graff Jr., J. A.  (2012) “How does oil and gas behave when spilled underwater,” Journal of Hydro-Environment Research, IAHR/Elsevier, 6, 275-285
Yapa, P. D., and Dissanayake, A. L (2012). “Discussion on A Model to Simulate the Transport and Fate of Gas and Hydrates Released in Deepwater, Journal of Hydraulic Research, IAHR. Vol. 50, No. 6 (2012), pp. 646–649
Dissanayake, A. L., DeGraff Jr., J. A., Yapa, P. D.,  Nakata, K., Ishihara, Y., and Yabe, I. (2012). Modeling the Impact of CO2 Releases in Kagoshima Bay, Japan,” Journal of Hydro-Environment Research, IAHR/Elsevier, 6 (2012) 195-208.
Bandara, U. C., Yapa, P. D., Xie H., (2011). “Fate and Transport of Oil in Sediment Laden Marine Waters,”. Journal of Hydro-Environment Research, IAHR/Elsevier, 5, 145-156.
Bandara, U. C., and Yapa, P. D., (2011). Bubble Sizes, Break-up and Coalescence in Deepwater Gas/Oil Plumes, Journal of Hydraulic Engineering, ASCE, 137,729-738.
Yapa, P. D, Dasanayaka, L. K., Bandara, U. C., and Nakata, K. (2010).  “A Model (MEGADEEP)  to Simulate the Transport and Fate of Gas and Hydrates Released in Deepwater, Journal of Hydraulic Research, IAHR. October, 48(5), 559-572
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
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.
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.