Leading edge serrations as a noise reducing high-lift device for owls

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Owls are stealthy fliers. They reduce the noise level and prevent prey from hearing them. An understanding of the mechanisms underlying silent flight may be an inspiration for the development of engineering solutions where stealth mode or noise reduction is required. Owls reduce aerodynamic noise in an efficient manner. One of the prominent mechanisms is the leading-edge serrations that radiate from the leading-edge and identified by many as the primary noise reducer. These serrations turn the flow over the wing at the leading-edge into the spanwise direction toward the wingtip, thus producing a stationary leading-edge vortex (LEV) that delays flow separation about the owl’s wing. The proposed research will study this unique noise reduction phenomenon resulting from the owl’s leading-edge serrations through both numerical simulations and experiments.

• Client: Start Bootstrap
• Date: 2015
• Service: Web Development

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Bird's aerodynamics

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We investigate the interaciton between birds and turbulence during various flight modes in a hypobaric wind tunnel using high speed time resolved PIV

• Client: Start Bootstrap
• Date: 2015
• Service: Web Development

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Unsteady aerodynamics during flapping flight of birds

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Birds’ unique characteristics such as wing shape, flexibility, feathers, flapping motion, etc., result in high aerodynamic performance. Using various flight modes such as gliding, bounding, and flapping, birds can use a single propulsion system for multiple functions. In low Reynolds number flyers using flapping flight mechanisms, the contribution of unsteady effects on lift and drag is not entirely understood. To gain insight about the unsteady contributions, a controlled study on the near wake flow behind freely flying birds is performed. Long duration, time resolved particle image velocimetry (PIV), combined with high speed imaging is used to characterize the various flow features in the wake that are associated with flapping flight. The specially designed PIV system can sample the flow field for twenty minutes yielding a continuous measurement, sampling several wingbeat cycles consecutively. Time series of the vorticity fields are expressed as composite wake plots, which reveal various characteristics of the wake during the upstroke (US) and downstroke (DS) phase of the flapping as well as the transition between US to DS and vice versa. Comparison between the near wake fields behind the three birds show remarkable similarity in their wake structure. We have identified over multiple wing beat cycles the presence of what appears to be an overlap of two distinct wakes during the transition from US to DS. Over this region, the majority of net positive circulation is accumulated. Indicating this may be a key feature in producing lift, and thus contribute to the observed high aerodynamic performance.

• Client: Start Bootstrap
• Date: 2015
• Service: Web Development

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Scalar dispersion in turbulent environment

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Turbulent mixing of a scalar plays a major role in many processes in engineering applications and environmental flows. In experimental investigations of turbulent mixing, it is necessary to measure the velocity and the scalar concentration fields, simultaneously, since the mixing process can be described as an interaction between velocity and concentration. These provide insight into the development of mathematical models for turbulent mixing and serve as a benchmark for numerical solutions.

Scalar dispersion is also associated with the release of contaminants into the ocean/atmosphere: We study the physical conditions present at the release point of the stormwater outflow pipes offshore North Myrtle Beach, such as tidal currents, ocean surface waves, and stratification conditions. An understanding of these conditions is necessary in order to understand and predict the dispersion of the stormwater plume under various conditions. These conditions are studied via field experiments employing acoustic Doppler velocimeters, temperature probes, and standard meteorological and water level measurement sensors.

• Client: Start Bootstrap
• Date: 2015
• Service: Web Development

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Fluid structure interaction

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Coming soon

• Client: Start Bootstrap
• Date: 2015
• Service: Web Development

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Flight patterns of insects using odor navigation in windy environment

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Several mechanisms control male moth’s navigation towards a female releasing sex pheromone. Optomotor anemotaxis is a visual mechanism for the moth flight direction relative to the ground, mechanoreceptors are used for calculating its speed relative to the air current and chemoreceptors on the antennae for sampling the pheromone concentration in the air. All together result in a zigzagging flight pattern of the male moth that depends on the characteristics of its encounters with the pheromone plume. We investigate how turbulence manifests the male flight behavior in respect to the streamwise current that carries the pheromone, emphasizing a relationship between the flight speed and the turbulent plume properties. The interaction between the moth flight and the flow field characteristics are examined in a wind tunnel where moth trajectory is recorded. Particle image velocimetry (PIV) and scalar imaging technique are utilized for measuring velocities and scalar concentration distribution in the tunnel. The role of turbulence in the moth navigation is evaluated by correlating the moth trajectory path with the flow properties. We have found that the moth’s upwind motion is related to the streamwise variations of the pheromone concentration while the zigzagging motion is correlated with the cross-stream turbulent flow fluctuations.

• Client: Start Bootstrap
• Date: April 2014
• Service: Web Development

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