As green renewable energy projects have become more of a global priority, significant advances have been made in the design, analysis, and optimizations of marine propulsors, current turbines and other offshore technologies. In particular, new standards for the Energy Efficiency Design Index (EEDI), which measures a ship’s CO2 emissions, have created new incentives for more efficient propulsors or Energy Saving Devices. Ocean engineers are leaders in the hydrodynamic aspects of renewable energy devices by designing and predicting their performance.
Faculty and students from UT Austin’s Ocean Engineering Group are frequent contributors to advances in naval architecture. The group specializes in computational hydrodynamics, cavitation, separated flows, and wave/body interaction, with applications to the design of marine propulsors and or tidal turbines and devices for the dynamic control of floating offshore structures.
Professor Spyros Kinnas is the impetus behind the success of the department’s ocean engineering program. A consummate teacher and researcher, he created the group when he came to UT Austin in 1995. The objective of the program is to provide aspiring engineers with a strong background in the underlying principles and familiarity with up-to-date computational techniques that are directly applicable to the assessment and design of engineered systems.
A portion of Kinnas’ research involves increasing the efficiency of marine propulsors (open, ducted or podded propellers, contra-rotating propellers, surface-piercing propellers, and water-jets), by predicting and controlling cavitation, which is a significant cause of erosion, noise, and vibration of the ship, as well as loss of thrust. Cavitation is the formation and immediate implosion of cavities in a liquid. Small vapor zones ("bubbles") form as a consequence of boiling of water under ordinary temperatures when subjected to low pressures.
In recent marine applications, the presence of cavitation is inevitable. Reliable computational tools help designers predict and minimize the amount of cavitation without sacrificing efficiency, which is highly desirable. This research has been supported for over 20 years by the US Office of Naval Research (ONR), and the Consortium on Cavitation, a group of international companies and research centers (such as Wärtsilä, Rolls-Royce, SSPA, Kawasaki, ABS, and Andritz Hydro) who regularly use software developed by Kinnas and his students to design their propulsors.
Kinnas’ research on cavitation directly affects the efficiency of sea vessels, thus minimizing their carbon footprint. Similarly, the space shuttle also experiences cavitation instabilities on the blades of the inducer stage of the pumps for the utilized propellants. His group recently received support from Pratt & Whitney Rocketdyne to explore design possibilities for a new shuttle system since his hydrodynamic methods can be applied.
Kinnas is also developing methods to design more effective ocean current/tidal turbines. He has been working on the hydrodynamic analysis of tidal turbines with various numerical methods for over five years. Both he and various graduate students have developed a blade design procedure based on optimization techniques which results into turbines that minimize cavitation and capture more current power than previous designs.
Numerical model of current turbine and its trailing wake (top), and predicted cavity patterns (shown in green color) on the rotor blades inside of a water-jet (bottom).
Another offshore component of UT’s ocean engineering research includes determining and predicting the flow around cylinders (bare or with a fairing) and the associated forces. Students use a flume and Time-Resolved Particle Image Velocimetry (TR-PIV) in the department’s Fluids and Hydraulics Lab to measure flow around cylinders subjected to currents and/or waves, which they then use to validate Computational Fluid Dynamics (CFD) tools.
Their findings can be applied to offshore platforms, which are comprised of many cylindrical or prismatic components (structural elements, floatation parts, risers, tendons, and mooring lines). Industry tries to minimize vortex-induced vibrations which occur on underwater cylinders because they are a source of fatigue damage to several components of offshore structures.
Some recent work performed with support by the Offshore Technology Research Center (OTRC), a joint center between UT Austin and Texas A&M University, addressed the prediction and mitigation of roll motions of FPSO (Floating Production system for Storage and Off-loading) hulls. These offshore platforms are stationary, converted oil tanker hulls that are connected to risers. FPSO hulls have a disconnectable turret and can be moved to a safer location in advance of hurricanes.
Kinnas teaches Fluid Mechanics and Intro to Ocean Engineering (senior course) as well as graduate-level classes on Computational Fluid Mechanics, Boundary Element Methods, and Theory of Propulsors and Turbines. He has received two departmental teaching awards and the Ervin S. Perry Student Appreciation Award which is presented to a faculty member who meets the ideals of “an excellent teacher and a good friend.”
As a young child in Greece, Kinnas fished along the Corinth Canal, which connects the Gulf of Corinth with the Saronic Gulf in the Aegean Sea. He watched ships pass through in amazement, and the canal became his inspiration for a lifelong interest in marine propulsion and fluid mechanics.
Throughout the years, Kinnas has served as an associate editor or on editorial boards for various professional journals. He has also chaired several international conferences in his field. The Ocean Engineering group at UT Austin will host the 4th International Symposium on Marine Propulsors (SMP) in 2015. Previous symposia have been held in Norway, Germany and Australia.
The Ocean Engineering program currently has seven graduate students and visiting scholars. Graduates of the program typically go on to work for research centers and academia or with the offshore industry.
The program’s OTRC also recently completed an offering of its two courses on offshore structures. The courses Fundamentals of Offshore Structures and Applications to the Design of Fixed Offshore Platforms and Design of Floating Systems attracted large numbers of attendees from all over the world. Engineers working in the offshore industry came to receive up-to-date technical knowledge on several aspects of offshore structures.
The next offerings at UT Austin are scheduled for April 14 to May 2, 2014. More information on the two courses.
