Researchers use Tecplot 360 and CFD to Determine Feasibility of Hydrodynamically-attached Biotelemetry Tags
We share a world inhabited by billions of fascinating creatures, few of which receive as much attention and universal affection as the dolphin. As magnificent, playful swimmers, they can propel themselves at speeds of up to 20 miles per hour through a watery world that is very different from our own. There is much these intelligent animals can teach us, and researchers agree the search for knowledge must be tempered with a proper concern for the well-being of these and other marine animals. One of the greatest challenges for researchers today is figuring out new ways to attach biotelemetry tracking tags that minimize the risk of injury or discomfort.
The Marine Mammal Science Journal recently published a ground-breaking study that describes the first attempt at developing a less invasive way of tracking dolphins for long-term behavioral research. The results of the study, which relied heavily on computational fluid dynamics (CFD), support the theory that biotelemetry tags can be held in place on a dolphin’s dorsal fin by hydrodynamic force. The development of effective hydrodynamic tags could eliminate or minimize the need to pierce the fins of dolphins.
Funded through the German National Science Foundation, the study was conducted by Dr. Vadim Pavlov and his team at the Research and Technology Center Westcoast, University of Kiel in Kiel, Germany. The group used Tecplot 360 to help visualize the CFD results critical to the support of their theory.
Laying the Groundwork for Less Invasive Dolphin Biotelemetry Tags
Currently, researchers attach biotelemetry tags to the dolphins by using either a suction cup or pins. Tags with suction cups are much less invasive and work well for short-term studies, but they tend to fall off after any length of time. For long-term studies, researchers attach the tag with pins that pierce the dorsal fin. Not only can this cause pain, but the presence of the pin and tag can also affect the animal’s behavior, thus biasing the resulting data. There is also significant evidence suggesting that tagged marine animals face a number of health risks. Tagging of free-ranging king penguins (Aptenodytes patagonicus), for example, impairs both survival and reproduction, ultimately affecting population growth rate.1
In their search for a better way to serve the health and well-being of marine mammals, as well as the advancement of science, Pavlov and his team decided to examine the viability of using hydro-dynamically designed tags for telemetry studies. They theorized that a properly designed hydrodynamic tag would remain securely attached to the dorsal fin for long periods of time, while minimizing drag on the dolphin’s body and allowing the animal to propel itself naturally through the water.
Using CFD to Visualize Hydrodynamic Flow
Animation Credit: Dr. Vadim Pavlov, University of Kiel.
Through a series of 35 experiments, Pavlov’s team gathered data around two models: one for a common dolphin with no tag, and the same model with a tag attached. They compared lift and drag efficiency in both models to understand the impact of the attached device. Flow was simulated for a velocity range of two meters per second to 10 meters per second, as well as a range of yaw and pitch angles.
Due to the complexity of the experiments and the amount of data gathered, the research team used the supercomputer facility in the University of Stuttgart, Germany. The simulation results showed an appropriate decrease in lift coefficient associated with the attached tag in 33 of the 35 experiments, indicating that when a dolphin swims, the resulting force would keep a hydrodynamically-designed tag attached securely to the dorsal fin.
Understanding Flow Basics with Tecplot
Faced with enormous amounts of data requiring analysis, Pavlov turned to Tecplot 360 CFD visualization software to help decipher, decode, and visualize the information. The team gained a more thorough understanding of the basic flow around the dorsal fin which verified their hypothesis.
Tecplot 360 allowed Pavlov’s team to observe the absence of edge flow and vortices behind the tag, which confirmed their supposition that a properly designed tag would have less impact on dolphins. “For our study, Tecplot 360 makes it easy to verify ideas more clearly. When you move zones in the areas of interest, move the slices and animate the stream traces, you can get a better idea, for example, where you’ve got some mistakes in the design.”
The scientists were able to easily identify areas for improvement simply because they could simulate flow around the dorsal fin and observe it under many varying conditions and angles.
Enabling Natural Behavior for More Accurate Data
After using CFD analysis and visualization to gain an in-depth understanding of the tag performance, the prototype of a tag was made by the Sea Mammal Research Unit and tested on dolphins at the Conservation Research Center Marineland in Antibes, France. Though no hydrodynamic testing was carried out, the behavioral responses to the short-time attachment of the tag led the team to conclude that the tag did not adversely affect the dolphins’ behavior.
“This is a small but important step in working with live dolphins because these animals are very sensitive to the devices attached to their body,” said Pavlov. “Normally, they try to get rid of any attachment.”
It is expected that the findings of this work will not only benefit dolphin research but also the investigation of other marine animals including seals, sea lions, turtles and penguins. Currently, the impact of rigid artificial devices placed on a living and flexible animal creates a barrier to that creature’s ability to behave in a wholly natural manner.
“I believe the next generation of telemetry tags will be constructed in an animal-friendly manner, based on understanding of the biology of the target species and bearing in mind natural characteristics of the site of attachment,” Pavlov said.
Widespread Benefits in Non-Invasive Tag Methods
The CFD analysis research is a first step in the process. In the next two years, Pavlov and his team expect to conduct live hydrodynamic testing of the novel tag under the wide range of natural dolphin behaviors, including accelerations, maneuvers, and leaping out of the water.
In the conclusion of his journal article, Pavlov said, “The development of non-invasive tags for marine mammals is important both from the perspective of scientific ethics and reliability of the data obtained in telemetry studies.”
Humans are naturally inquisitive and have a drive to learn as much as possible about everything – living or otherwise – that cohabitate on this planet and beyond. However, it is our ethical duty to ensure that we are not causing harm or trauma to the creatures that so fascinate us. With solid CFD visualization tools, such as Tecplot 360, researchers like Dr. Pavlov and his team are able to expand the limits of marine mammal science, and help fully realize a future of humane and safe animal research that may lead to many more discoveries down the road.
1 EISSN: 1476-4687 ISSN: 0028-0836 Nature
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