Dr. Amy Lang, alang@eng.ua.edu, http://aem.eng.ua.edu/people/lang/lang.asp

Dept of Aerospace Engineering and Mechanics

This research is primarily interested in 2D and 3D patterned surfaces with micro-cavities where vortices embedded within the cavities of the microgeometry lead to the formation of a partial slip condition thus favorably increasing the momentum in the boundary layer close to the wall.  Dr. Lang is investigating the biomimetic microgeometry of a bristled shark skin as a possible means by which the shortfin mako uses it skin to either delay transition or control separation, thereby decreasing drag and allowing for faster swimming speeds.  The figure shows fluorescent dye visualization of the embedded vortices found to form in a bristled shark skin model.  By scaling down the water tunnel velocity, the size of the denticles can be scaled up 100 times on the model (typical shark scale size is 0.2 mm) for experiments.  

REU Participant's Role: The students will be involved in various phases of building and testing 2D and 3D microgeometry models.  They will be using flow visualization (fluorescent dye and particle streaking) and TR-DPIV (under supervision of a graduate student) to study the boundary layer and cavity flow fields under either turbulent or laminar flow boundary layer conditions in the water tunnel and take drag measurements in the Couette flow facility. 

Dr. Ajay Agrawal, aagrawal@eng.ua.edu

Department of Mechanical Engineering

In recent years, quantitative Rainbow Schlieren Deflectometry (RSD) technique has been developed and applied to non-intrusively obtain temperature and species concentration measurements in non-reacting and reacting flow configurations.  In the RSD technique, the knife-edge of a convection Schlieren system is substituted with a computer generated color filter to relate the angular ray deflection to color (or hue) in the rainbow Schlieren image.  The figure shows a RSD image of a laminar flame. Unique features of the RSD technique are: no lasers are involved and, hence, the apparatus is relatively inexpensive; the technique is robust and it can accept minor mechanical vibrations and misalignments; the measurements are obtained across the whole field; and high spatial resolution (on the order of 0.1 mm) and temporal resolution (on the order of 5000 Hz) can be attained in systems with field of view of 100 mm or more.  Recently, we have developed a miniature RSD apparatus using the principles of the macro-scale rainbow Schlieren apparatus. 

Dr. Chris Brazel, cbrazel@eng.ua.edu, http://www.bama.ua.edu/~cbrazel/

Hyperthermia treatment is a clinically-proven method used in cancer treatment whereby a high grade fever is induced either throughout the body or in a region of the body (approximately 42-45 ^oC). Cancer cells are much more susceptible to these temperatures than healthy cells, thus hyperthermia treatment can effectively kill cancer cells while minimizing the effect on healthy cells and tissues. The challenge of heating tumors efficiently with minimal side effects has kept this method from being used as widely as surgery, chemotherapy and radiation therapy. Magnetic materials such as cobalt ferrite, iron platinum and magnetite are being studied in the Brazel laboratory to determine candidate materials that have Curie temperatures around 50 ^oC, so that the likelihood of serious tissue damage can be minimized, while still achieving effective temperatures for hyperthermia.

REU Participant's Role:  Students working on this project will be involved with an established cross-disciplinary research team and will conduct both experimental as well as calculation/modeling work. In particular, REU students will use the confocal microscopy technique which through the use of fluorescent dyes visualizes the localization of nanoparticles within the synthesized magnetic fluids.  Student data will contribute to the development of mathematical models to better understand the relationship between magnetic nanoparticle size and composition, fluid dynamics (eddy flows), and thermal diffusion.

Dr. Paul Hubner, phubner@eng.ua.edu, http://phubner.eng.ua.edu/

Department of Aerospace Engineering and Mechanics

Micro air vehicle (MAV) designs that employ biologically-inspired, flexible wing structures have the ability to passively control wing shape to improve stability, alleviate gust divergence and increase lift.  The out-of-plane deformations due to aerodynamic loading on the membranes  demonstrate the ability of the wing to create adaptive washout or adaptive billowing. These wings deviate from conventional high Reynolds number designs (Re > 200,000) due to the presence of a leading-edge separation bubble.  Factors such as wing shape and planform, surface roughness, angle-of-attack, freestream turbulence and membrane properties can influence the formation of the separation bubble.  The membrane compliancy can lead to dynamic fluid-structure coupling.  An improved understanding of this coupling and its potential passive control effect is the primary objective of this research effort.

REU Participant's Role: The students will perform flow visualization surveys over flexible, membrane wing geometries to assess the extent of the separation bubble position and size, or lack or reattachment, as well as unsteady shear layer structures.  They will assist in model design and fabrication, test configuration, image acquisition and data post processing. 

Dr. Semih Olcmen, solcmen@eng.ua.edu

Department of Aerospace Engineering and Mechanics

Shock waves occur on every vehicle moving faster than the speed of sound and result in much unwanted flow phenomena. The flow field downstream of the shock wave experiences increase in static temperature and pressure and decrease in total pressure. While the increase in static temperature results in high heat transfer rates to the vehicle, increase in static pressure leads to increased drag. Reduced total pressure is an indicator of the available useful work that can be extracted from a fluid and increased internal energy (thus temperature) of the fluid. Increased heat transfer rates require extra shielding (thus weight) on vehicles. Interaction of the shock waves with each other may even result in catastrophe by softening, melting, or even incinerating vehicle structure. Dr. Semih Olcmen and his group are continuing to study the flow field generated by the interaction of a large supersonic free jet and of a choked sonic counter-flowing small jet. The research has demonstrated that a counter-flow jet injected into the large jet with about 1% mass flow rate of the large jet can be used to attenuate/modify the shock structures as shown in the figure.

REU Participant's Role: REU participants will learn about many different experimental techniques in a hands-on fashion and will be exposed to laboratory environment. The student will be separately responsible for a part of the project. Students will be required to write data acquisition/reduction programs, do their own experiments, analyze data and write reports.

Dr. Paul Puzinauskas, ppuzinauskas@eng.ua.edu

This project will use steady flow testing to characterize intake flow configuration effects on in-cylinder flow structures. This will be done with a combination of bulk angular momentum measurements and PIV analysis. A subsequent portion of the investigation will characterize how these structures develop in an unsteady engine using CFD and quantify how they affect engine performance through dynamometer testing. The bulk angular momentum will be measured using an impulse swirl meter as shown in the figure. Such measurements give a good indication of the overall strength of the mean motion in a particular direction , but can be misleading when counter rotating structures are present. Such structure pairs have the potential to be significant turbulence producers, but their counter-rotating orientation can cancel much of their individual momentum when measured in total. The PIV measurements will be made to identify if such a condition exists and also should be able to guide potential intake modifications to enhance the desired in-cylinder flow structures.

REU Participant's Role: The student will execute the steady bulk flow and PIV analysis with interaction from a graduate student. Several base intake configurations will be tested for swirling or tumbling flow and these base configurations will be refined based on the results generated by the student and through feedback from the CFD and engine testing efforts.

Dr. Muhammad Sharif, msharif@eng.ua.edu, http://aem.eng.ua.edu/people/msharif/sharifindex.htm

Department of Aerospace Engineering and Mechanics

The associated flow physics of an impinging jet issuing from a small orifice onto a surface is quite complex due to flow turning, fluid entrainment, and the development of boundary and shear layers and various interactions among these phenomena. The impinging jet configuration is encountered in numerous industrial and engineering applications. Among these include cooling of a hot surface, cooling of electronic components, drying of a surface, turbine blade cooling, and airplane wing leading edge de-icing.  In the design and operation of these applications the knowledge of the heat transfer coefficient distribution along the cooling surface is very important. Presently very little information about the heat transfer coefficient distribution for these applications is available in open literature. This study involves detailed numerical heat transfer analysis for turbulent jets impinging on curved surfaces. Heat transfer correlations in terms of the variation of the Nusselt number on the surface as a function the jet exit Reynolds number and other geometric and flow parameters will be formulated. In particular, heat transfer correlations will be developed for the turbine blade cooling and airplane wing leading edge de-icing applications.

REU Participant's Role: The students will be involved in various phases in developing the numerical model of the problem including mesh generation, problem set up, program execution, and analyzing the results. Working closely with the faculty and graduate students, they will gain hands on experience with state of the art CFD solution procedure and data visualization techniques.