PRACtically Speaking
The Newsletter of Petroleum Research Atlantic Canada - June 2006Research Profile
Establishing a Method That Can Be Used To Give Detailed Predictions of DP Thruster Wake Effects
Dr. Pengfei Liu, Institute for Ocean Technology, National Research Council Canada, and Adjunct Professor, Memorial University of Newfoundland
Dr. Pengfei Liu is a senior research officer at the Institute for Ocean Technology, National Research Council Canada. In 2001, Dr. Liu together with Dr. Neil Bose from Memorial University and a PhD student from the Institute for Marine Dynamics (IMD) received funding from ACPI, PRAC’s predecessor, to develop numerical and experimental modeling of dynamic positioning (DP) propellers for offshore systems.
Application and use of DP systems have increased in the offshore oil and gas industry as operations move into more hostile and deeper waters. In spite of the increased dependency on DP thrusters, there is a lack of knowledge about the effects of their wakes on other offshore structures and on how to describe and predict this force. Research on this subject is fundamental to the assessment of design loading on various slipstream-submerged equipment associated with such platforms as Floating Production Storage and Offloading vessels.
Figure 1. Propeller wake velocity measurement by the 2D LDV system at IMD’s cavitation tunnel. Images show the LDV laser beams when measuring downstream velocity components of the thruster model without a nozzle.
This research project analyzed the DP thruster near-wake to determine downstream velocity profiles and fluctuation. This can be used to evaluate the effects of current jets from thrusters, thereby enabling design engineers to predict the momentum impacts on structures in the thruster slipstream.
Using two-dimensional Laser Doppler Velocimetry (LDV) in a cavitation tunnel (Figure 1), the research team experimentally measured near-wake velocity components at different cross sectional planes. Each cross sectional plane was divided into seven circular sections and flow velocity components were measured at a number of points distributed over each circular section.
For the numerical modeling component, two different simulation techniques (PROPELLA and CFD Fluent 6.0) were combined. PROPELLA described the detailed potential flow close to the propeller, while the CFD modeled the wake and breakdown of the slipstream in the far-wake.
Figure 2. Experimental and numerical prediction of the hydrodynamic performance of a DP thruster
Results from this experimental work provide a complete description of:
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The DP thruster wake structure and characteristics in the near wake
Energy losses in the wake by tracking the change in velocity at different cross sectional planes downstream
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Effects of the variation of DP thruster operating parameters (speed, pitch ratio, advance coefficient) on the near wake pattern and how the flow pattern is modified by the change in these input parameters
Moreover, the results agree with previous studies done for propeller near wake evaluation. Numerical modeling has been in progress for near wake survey at IMD using the in-house code PROPELLA.
The research findings have drawn a wide interest from the offshore petroleum industry, foreign national laboratories and the defense sector.
PRAC News
Newly Elected Board of Directors
The members of PRAC elected a new nine-member Board of Directors during the Annual General Meeting held on May 10, 2006 in Halifax, Nova Scotia.
Those elected are Liam Mallon (Board Chair), ExxonMobil Canada Ltd.; David Collyer, Shell Canada Ltd.; David Kopperson, EnCana Corporation; Tim Murphy, Chevron Canada Resources; Ruud Zoon, Husky Energy Inc.; Brian Condon, Newfoundland and Labrador Department of Natural Resources; Andrew Noseworthy, Atlantic Canada Opportunities Agency; Alison Scott, Nova Scotia Department of Energy; Dr. Axel Meisen, Memorial University of Newfoundland.
The composition of the new Board reflects changes in PRAC’s by-laws that aim to streamline the governance of the organization and make it more responsive to the research and development needs of industry. “The smaller board is more in line with other member-based organizations and should facilitate decision-making” says Dave Finn, President of PRAC.
“Until recently industry’s perspective on the board was somewhat diluted,” comments Finn. To better fund and facilitate industry-driven research, Finn explains that PRAC members have elected a smaller board with a majority, including the Chair, representing petroleum companies.
PRAC wishes to welcome its new Board members and thank them for their participation.
Call 7 for Research Proposals
Recently PRAC’s Board of Directors approved funding for three projects arising from the seventh call for proposals. PRAC will provide grants totaling $334,000 over three years to these projects which will leverage an additional $1 million from other sources including NSERC and the Geological Survey of Canada.
Successful applicants include:
Dr. Georgia Pe-Piper, Saint Mary’s University – Diagenesis of Lower Cretaceous Rocks in the Scotian Basin
Dr. Juergen Adam, Dalhousie University – 4D Simulation and Seismic Interpretation of Basin Evolution and Salt Mobilization in the Abenaki Sub-basin, the Mohican Graben and their Deepwater Extensions Offshore Nova Scotia
Dr. Michael Enachescu, Memorial University – Structural and Seismic-stratigraphic Architecture and Petroleum Systems of the Laurentian Basin, Offshore Newfoundland and Nova Scotia
A further three proposals have been recommended for funding and will be considered by the Board of Directors in a subsequent meeting. It is anticipated that PRAC will contribute roughly $600,000 in total to this call which was focused exclusively on research related to geoscience and reservoir engineering.
International Ocean Institute
Since 1981 the International Ocean Institute (IOI) has offered an intensive, inter-disciplinary training program. This program is specifically designed to benefit mid-career professionals from developing countries who are responsible for some aspect of marine management/ocean governance.
For the second consecutive year PRAC will organize and deliver part of the energy module for the IOI training program being held in June at Dalhousie University in Halifax.
The purpose of this training program is to provide a deeper understanding of the ever-increasing importance of the oceans and their resources, to assist in forming a core of decision-makers fully aware of the complex issues of ocean management, and to maximize benefits derived from the proper integration of ocean management into national and international development strategies.
The energy module will focus on a range of issues related to the exploration, development and production of oil and gas from the ocean environment and the interaction with other ocean uses. It will also consider the growing importance of renewable energy resources from coastal and offshore areas such as tidal, wind, wave and gas hydrates.
Maritimes Basin Workshop
In conjunction with the New Brunswick Department of Natural Resources, PRAC recently held a workshop entitled Cooperative Hydrocarbon Geoscience in Eastern Canada’s Onshore and Nearshore.
This workshop served as a forum for stakeholder discussions on the current status of hydrocarbon basin studies, exploration activities, and the direction for future research.
Representatives from federal and provincial agencies presented the strategic aims of government-sponsored energy programs and provided overviews of ongoing research in the Early and Late Paleozoic successions.
Participants, including representatives from academia and industry, discussed strategies for leveraging research programs in order to develop opportunities for greater cooperation in the delivery of hydrocarbon research in the Atlantic region. The need for PRAC to facilitate such discussions on an annual basis was identified during this workshop.
Comments & Questions Welcomed!
Please contact communications@pr-ac.ca with any questions or comments about this newsletter and visit the rest of PRAC's website for more information.q
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