The Coastal Engineering & Fluid Mechanics lab led by Dr. Daniel G. MacDonald, Principal Investigator, pursues research in a variety of areas related to coastal physics and engineering. Basic and applied research encompasses the areas of stratified hydrodynamics, turbulence and frontal dynamics—with specific emphasis on estuarine flows, river plumes, and industrial discharges. A significant research focus also lies in the area of marine renewable energy, including wave energy and the development of nearshore wave energy converters (WECs), and the hydrodynamic aspects of other marine renewable technologies.
Daniel G. MacDonald|
SMAST Department of Estuarine & Ocean Sciences
200 Mill Rd, Suite 325
Fairhaven, MA 02719
MeRMADE I (NSF, 2006-2010, Award OCE- 0550096)
MeRMADE II (NSF, 2009-2014, Award OCE- 0850948)
MeRMADE I (2006-2010) focused on understanding the mixing processes and widening of the plume in the highly energetic region just beyond the river mouth, extending seaward 2-5 km. This effort, a combined field observation (UMassD) and numerical modeling (TAMU) program, yielded valuable information about the nature of plume spreading, which is controlled primarily by the difference in density between the river discharge and the ambient ocean water, and the mixing between these two water masses. Mixing, which reduces the ambient density difference, has a tendency to reduce spreading, while the spreading of the plume was found to increase the intensity of mixing processes by enhancing the energy in local turbulence that occurs at scales on the order of 10 cm.
This research has continued in MeRMADE II (2009-2014), which focuses on the transition of this high-energy region outside the mouth to a more passive coastal current that can travel down the coast for 50-100 km or more. To address the complex issues associated with this transition, the experimental laboratory expertise at UW was added to the MeRMADE effort, providing, along with the observational and numerical approaches, a three-pronged strategy to the research. Ph.D. students and PI’s at each of the three campuses interact regularly through videoconferences, and students gain valuable exposure to all three research approaches. Detailed field measurements are used to quantify mixing in the plume and, in particular, to determine where and how it is arrested. Non-rotating and rotating laboratory studies are used to investigate how spreading modifies fundamental mixing processes in the core of the plume and along the front. The broad parameter space studies of the laboratory and the specific observations at the field site are bridged with numerical simulations, which are carried out at both laboratory and river plume scales. Synergy between all three approaches exploits their strengths, exposes their weaknesses and provides valuable cross-fertilization between these often exclusive techniques.
MeRMADE II field efforts have included the release and recovery of approximately 250 individual drifters in the plume region under a variety of environmental conditions. Among other things, these results indicate the importance of wind to plume development (Kakoulaki et al., in prep.), and will be essential in understanding plume spreading processes (Kakoulaki and MacDonald, in prep.). Analysis of moored ADCP data (Wang et al., submitted) has established an understanding of the importance of river discharge, tides and wind in generating near-field turbulence.
(NSF, 2012-2015, Award GEO/EARTH SCIENCES 1148068)
As part of a collaborative effort with faculty from UMass Amherst and Amherst College, we are evaluating the fluid dynamics associated with sedimentation of tie-channel ponds in the tidally influenced reach of the lower Connecticut River. Our working hypothesis is that sedimentation is accomplished through tidal pumping of sediment laden river discharge into tie-channel ponds during periods of moderate discharge (high enough to increase sediment loads, but low enough to maintain a tidal signal). Similar mechanisms may be responsible for sedimentation processes across many coastally influenced regions, and provide a mechanism for the deposition and storage of legacy contaminants.
(Department of Energy / NEMREC, 2010- )
Surface waves are nature’s means of moving energy across the world’s oceans, and as such, represent a rich and constant source of energy. A variety of technologies have been proposed to capture energy from ocean waves over the past several decades. However, wave energy conversion technology today exists primarily in the research and development stage, and most experts consider the state of the technology to be ten to twenty years behind the development of wind energy.
The wave energy field to date has been saturated with an overabundance of conceptual designs, and a lack of return on investment. Our laboratory has been taking a fresh, practical approach compared with recent theoretical designs and prototype development. First we are developing low cost, low maintenance devices that can generate modest amounts of power for local use. Our goal is to develop a basic wave energy converter (WEC) on the order of $1,000, with a mean output of up to 1 kW of electricity. These devices will eliminate the need for separate moorings or support infrastructure by using fixed infrastructure (piers, docks, breakwaters, etc. in the near-shore zone, or fixed/floating oil or wind platforms offshore) to reduce costs. The devices will be modest in size, with the near-shore versions easily handled by a team of two or three individuals without the use of heavy equipment. The majority of the mechanical core of our device will be assembled from off the shelf parts, keeping costs down. However, the most significant part of our design is our unique magnetic coupling system, which allows all mechanical components to be isolated from the marine environment in a sealed tube, reducing the potential for corrosion and biofouling in the marine environment, and keeping maintenance activities to a minimum. Another key advantage to our small scale approach is the ability to bring a product to market within a timeframe of years, as opposed to the decades required for the research and development track necessary for utility scale offshore wave energy farms. Our first generation prototype has demonstrated a proof of concept, but funds are now needed to develop a second generation prototype, which can demonstrate efficiency and survivability in the marine environment, to translate widespread interest into investment.
In collaboration with the Lake Sunapee Protective Association (LSPA), moored instrumentation has been deployed in Lake Sunapee, NH in an effort to understand circulation dynamics, particularly during the stratified summer season. Lake Sunapee is a glacially formed lake with four sub basins separated by relatively shallow sills. Interbasin exchange of water is of interest ecologically, and particularly for understanding the potential transport pathways of invasive species.
(Brayton Point Power Station, 2003-2006)
As part of the Mt. Hope Bay Natural Laboratory, the CEFM lab conducted several observational efforts in Mt. Hope Bay (MA/RI), in an effort to understand physical processes occurring within the Bay, and their relation to a thermal plume discharged from Brayton Point Power Station. Efforts focused on the near field region of the thermal plume and on the passage between Mt. Hope Bay and Narragansett Bay. These studies have helped to delineate the flushing and mixing characteristics of the natural bay environment and the Brayton Point discharge region. Heat budget analyses have indicated some potential drawbacks of mixing zone approaches for thermal discharges, which can result in dilution of excess heat and its isolation from the surface, preventing heat transfer to the atmosphere, and resulting in indefinite storage of heat within the water body.
Natural Hazards & the Ocean is primarily a descriptive course that is intended to educate students about the roles of the oceans in such natural hazards as hurricanes, earthquakes, global warming, and tsunamis. The course will address student curiosity about these ocean-related hazards, by presenting a conceptual understanding of the relevant underlying ocean-atmosphere, and earth-mediated mechanisms. The students will be presented in lecture and through their readings about how the application of the scientific method (a) overturned historical Misunderstandings of Earth geology; (b) explains the far-reaching effects of ocean storm-generated waves; (c) relates deep ocean earthquakes to tsunamis; and (d) relates how dust from the North African deserts is related to hurricane generation. (3 credits)
Analytical study of the physical processes governing waves in the marine environment. Covered topics include surface gravity waves, internal gravity waves, energy flux, group velocity, long waves, linear and nonlinear shallow water waves, and atmospheric forcing. This course will be of interest to any ocean scientist or engineer interested in the physics of waves. (3 credits)
Study of transport processes in the environment. Topics include advection, diffusion, jets, plumes, air-gas transfer, heat transfer, reaction kinetics, sediment-water exchange, sediment erosion/deposition, and ground water transport. The course should be of interest to upper level undergraduates or first year graduate students in ocean science or engineering with an interest on transport processes in the environment. (3 credits)
Fundamental fluid dynamics underpinning ocean turbulence theory. Emphasis is placed on both a mathematical and physical understanding of turbulence and considerable time is spent on classical turbulence theory and its application to ocean processes. Random variables and their quantification are introduced, as are dimensional scaling and analysis and non-dimensional quantities such as the Reynolds, Richardson and Prandtl number. Other course emphases include exchange of energy between the mean flow and turbulent field, turbulent diffusion, modern data analysis techniques and recent observations and newly emerging observational tools and techniques. (Prerequisite: MAR 555, introductory fluid dynamics, or permission of instructor. 3 credits)
Physical processes governing estuarine circulation. Topics include estuarine classification, tides in estuaries, turbulence and mixing in stratified environments, secondary (cross-channel) flows, salt and momentum balances, velocity-induced straining, hydraulic control and the establishment of estuarine fronts, engineered discharges and plumes, and other types of flows important to estuaries. The course will make ample use of homework assignments and problem solving, with examples from the appropriate scientific literature. (3 credits)
Georgia Kakoulaki (Graduate Student)
Using surface Lagrangian drifters Georgia's research is focused on the study of the poorly understood process by which river plumes transition into coastal currents. Her study area is the region where the Merrimack River empties into the Atlantic (Newburyport, Massachusetts) and is part of the Merrimack River Mixing and Divergence Experiment (MeRMADE II).
Georgia graduated from the Technological Educational Institution of Crete. Following graduation she spent three years doing archaeological fieldwork in the Laboratory of Geophysical - Satellite Remote Sensing and Archaeo-environment. She later received a Master's degree from the Coastal Geo-sciences and Engineering program at Christian-Albrechts-University in Kiel, Germany. Her thesis examined the correlation of surface current data (X band radar), with bathymetric maps and a hydrodynamic model (Delft3D).
Brandon Green (Graduate Student)
Brandon's research is focused on the development, numerical modeling, and optimization of novel wave energy converter technologies. He participated in the first phase of development of the microWEC device, a small-scale wave energy converter designed for generating low amounts of power for local consumption. He has worked closely with multiple senior engineering design teams to develop first-and second-generation prototypes of the WEC devices. His thesis involves further developing the numerical model to test against data created with the second generation prototype in a wave tank. In addition to the model-data comparisons, Brandon also focuses on wave data analysis collected from Clark's Cove in New Bedford, MA.
Brandon graduated from Bridgewater State University with a B.S. in physics and mathematics, and he received his M.S. degree in physics from University of Massachusetts Dartmouth. Green and MacDonald are the authors of a manuscript (2013) in the Marine Technology Society Journal (MREC Special Issue) describing the numerical modeling effort associated with the first-generation prototype.
Jianfeng Wang, Ph.D (Visiting Scholar from Ocean University of China, 2012)
Research interests: Currently focused on the importance of river discharge, tidal range, and wind on the variability of Turbulent Kinetic Energy Production in a near-field river plume based on Acoustic Doppler Current Profiler (ADCP) observational data and models.
Fei Chen (Ph.D. 2009)
|Thesis:|| Physical Processes In Near Field Buoyant Plumes: Turbulence, Mixing and |
Adrienne Pappal (M.S. 2006)
|Thesis:||Cobble Habitat Preferences of Juvenile Winter Flounder, Pseudopleuronectes Americanus; and Comparison of Laboratory Observation Techniques|