Our laboratory research focuses on fluid dynamics and heat transfer in micro- and macro-scale flows.
Volcanic eruptions consist of the sudden release of high pressure gas and particulates from a vent to the atmosphere. The fluid dynamics are complex, as overpressured conditions produce supersonic flow in the near-exit region. This has a significant impact on the entrainment of ambient air into the jet, which alters the plume buoyancy and ultimate behavior. Once the plume ascends, its trajectory is altered by cross winds and atmospheric stratification, which further impact the entrainment. Our current understanding of this behavior is limited due to the difficulty of field measurements, resulting in great uncertainty in the estimate of ash density. Our laboratory uses high-accuracy particle image velocimetry (PIV) methods to determine the entrainment, which is integrated into state-of-the-art plume models for volcanic eruptions.
- Ash aggregation in volcanic plumes
Our laboratory collaborates with Stanford University, Portland State University, and the USGS Cascades Volcano Observatory on a study of ash aggregation within volcanic plumes. Much of the particle matter ejected in an eruption aggregates into larger particles, which aids its fallout from the plume. While many aggregation methods are known, there is little experimental data on their effectiveness, and virtually no fallout models include aggregation. In this NSF-supported study, we are conducting high-resolution measurements of this phenomenon in both homogeneous turbulence and jet flows. Our data will be used to develop a new simulation tool to examine fallout following eruptions.
- Overpressured jet entrainment
- Erodible vent evolution
- Plumes in cross flow
The rapid increase in power dissipation from electronic devices has led to challenging thermal management issues. With heat fluxes of hundreds of watts per square centimeter, even aggressive techniques are being stretched to their limits. Fortunately, micro-scale enhancement methods can extend traditional methods beyond their current usage to meet future thermal loads. Passive techniques include micro-fabricated versions of macro-enhancement methods, such as turbulators, dimples, and pin fins. Active methods include micro-scale jets to augment local heat transfer at hot spots. Our laboratory investigates a range of electronics cooling techniques, including micro-channel enhancement and synthetic jets, to determine their efficacy and potential applicability in electronics devices. We use advanced experimental techniques, such as micro-PIV, as well as computational tools incorporating the micro-scale physics
- Variable-diameter synthetic jet cooling
Our laboratory has developed a unique synthetic jet actuator, which uses oscillating motion near an orifice to generate a time-averaged jet flow. Our device synchronizes the motion with the closure of the aperture, resulting in a significant increase in momentum flow. We have applied the actuator in impingement cooling, demonstrating superior performance to fixed-diameter devices. Along with collaborators at WSU Vancouver and the University of Portland, we are optimizing a new, micro-scale adaptation through computational fluid dynamics (CFD), PIV, and infrared (IR) thermography. This system will apply fluidic methods to simplify the mechanism, permitting high-frequency, miniaturized devices.
- Slot-orifice synthetic jet fluid dynamics
- Groove-enhanced mini-channel heat transfer
- Integral micro-channel cooling
- Diode laser micro-heat exchanger analysis
Modern engineering devices require careful control in order to function appropriately and efficiently. Although many control methods involve large-scale actuators like airplane flaps, smaller micro- and meso-scale devices can also produce macro-scale flow control and enhancement benefits. By applying low-energy driving forces at key locations in a flow system, substantial improvements can be made to the entire structure. Many potential solutions can be derived using biomimetics, where biological characteristics are mimicked in technology development. In their evolution, organisms have developed unique capabilities that may be more efficient than existing engineering designs. Our laboratory explores biomimetic flow devices, particularly involving jet flows, which may be applied in aerospace control and electronics cooling applications. We apply theoretical analysis, computational simulation, and experimental validation to examine the full performance range of these new actuators in order to develop a better fundamental understanding of their physics.
- Manifold design for optimal flow distribution
Our laboratory develops methods for optimal design of manifolds, which produce flow in arrays of channels for electronics cooling, chemical systems, and biomedical devices. We base our designs on the human circulatory system, which efficiently transfers fluid throughout the body while minimizing losses. We use analytical methods to develop our designs along with collaborators at WSU Vancouver, and we study their performance through CFD and micro-PIV.
- Synthetic jet micro-blowing
- Micro-trailing-edge effectors
- Cavity oscillation control
- Segmented wind turbines
ADDITIONAL RESEARCH INTERESTS:
- Renewable energy
- Advanced fluid diagnostic methods