Projects – Research Experience for Undergraduates

Fluid Mechanics with Analysis Using Computations and Experiments

Understanding Blood Flow during Blood Pressure Measurements

Faculty Advisor: Dr. Amanda Koh, Chemical and Biological Engineering

Project Description: Blood pressure is one of the most commonly measured biometrics at medical appointments and are one of the key indicators of cardiac health. Nearly 50% of adults in the United States have high blood pressure, which leads to increased risk of heart attacks, stroke, aneurysms, heart failure, dementia, and deterioration of the eyes and kidneys. As such, it is highly important that blood pressure measurements are accurate. Blood pressure measurements are essentially external quantifications of fluid flow occurring within the brachial artery using an expandable cuff around the upper arm. Recent studies have shown that using a blood pressure cuff that is the incorrect size (miscuffing) leads to inaccurate patient measurements. Miscuffing may occur due to a lack of availability of the correct sizes or failure of a medical professional to measure the upper arm before taking the measurements. While it is known that miscuffing causes inaccurate blood pressure measurements, the impact of the cuff on blood fluid flow is relatively unknown, thus making a better, more accurate blood pressure cuff is a great challenge. To make a universal blood pressure cuff, improve accuracy, and improve public health, we must have a greater fundamental understanding of the impact of the blood pressure cuff on blood fluid flow. Particularly understanding how cuff parameters (e.g., material elasticity or geometry) and vascular stiffness impacts the transmission of cuff pressure to the brachial artery and the resulting fluid flow is critically important.

REU Participant’s Role: REU student will have the opportunity to create simple experimental models of the brachial artery, the surrounding arm, and blood flow using artificial blood and measure critical fluid flow parameters such as wall shear stress and Reynolds numbers as a function of applied pressure for a variety of blood pressure cuff sizes, materials, and geometries.

Propeller Gust Encounter

Faculty Advisor: Dr. Redha Wahidi, Assistant Professor, Aerospace Engineering and Mechanics

Project Description: The aim of this project is to investigate the gust encounter by a propeller. Urban Air Mobility vehicles operations in urban environments creates challenging conditions as they encounter gust (large-scale vortices) originating from the urban infrastructure. This gust encounter of the rotary wing creates additional noise that needs to be reduced publicly accepted levels. The encounter might also affect the stability and control of these vehicles. To simplify the problem, we create 2D gust to interact with a propeller and investigate the effects of the encounter on the thrust developed by the rotor and on the wake of the propeller.

REU Participants’ Role: The experiments will take place in subsonic wind tunnel, and the thrust will be measured using load cells. The flow field in the propeller wake will be measured using 3D particle image velocimetry (3D-PIV). The student will be involved in 3D printing of models, setting the experiments in the wind tunnel, and in writing computer codes to analyze the 3D-PIV data.

Bio-inspired Boundary Layer Control

Faculty Advisor: Dr. Amy Lang, Professor, Aerospace Engineering and Mechanics

Project Description: This research involves gaining inspiration from nature to control boundary layer flow. The two primary projects involve inspiration from sharks and butterflies. Sharks have movable scales on key locations of their body. These micro-roughness elements are hypothesized (and have been shown using real shark skin sample testing in our water tunnel) to be a passive, flow-actuated separation control mechanism. Butterflies, on the other hand, have a roof-shingle pattern of scales (each 0.1 mm in size) that alter the surface drag over the wing depending on flow orientation. Recent flight testing of live Monarchs has shown an on average 40% decrease in joules/flap when the scales are removed from their wings.

REU Participants’ Role: In both cases experiments will be conducted to simplify a complex flow problem and isolate the potential mechanisms leading to engineering flow control applications. The student will be involved in various phases of building and testing rapid-prototyped bio-inspired models and may use DPIV (Digital Particle Image Velocimetry) to measure flow fields.

Assessment of Propeller Location on the Aerodynamics Characteristics

Faculty Advisor: Dr. Paul Hubner, Professor, Aerospace Engineering and Mechanics

Project Description: This project involves investigating the effects of the propeller location on the wing the aerodynamics. Aircraft such as NASA’s X-57 and Electra’s Ultra Short Technology Demonstrator exploit distributed electric propulsion and the concept of blown lift to increase the effective lift of the vehicle, decreasing take-off and landing distances as well as affecting flight control systems. To generate a desirable amount of blown lift, the propeller’s location effect on the generated blown lift needs to be determined.

REU Participants’ Role: The student will assist in the test design and operation as well as the data analysis and presentation to assess the streamwise and vertical position of a single- or dual electric motor/propeller configuration on the aerodynamic characteristics of a wing section. Tests will be performed in a low-speed, open circuit wind tunnel, and will involve measurements of the aerodynamic force.

Internal Combustion Engine Flows

Faculty Advisor: Dr. Paul Puzinauskas, Associate Professor, Mechanical Engineering

Project Description: 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.

Measurements of Reacting Fuel Sprays using High Speed Imaging

Faculty Advisor: Dr. Joshua Bittle, Mechanical Engineering

Project Description: Diesel and gasoline direct injection engines operate with fuel injected directly into the cylinder mere milliseconds prior to ignition in the case of a diesel engine. To enable rapid mixing the fuel is injected at extremely high pressure (~35,000 psi) through nearly invisible holes (<0.1mm). This high pressure, small diameter nozzle creates a finely atomized spray that is able to quickly mix and vaporize in the hot gases in the engine cylinder prior to ignition. To study the spray isolated from the actual engine a constant pressure flow vessel is used with optical grade windows on the sides of the chamber. This allows lighting and camera access to capture high speed (50,000 fps) videos of the sprays to study the penetration speed (>200 mph), spreading angle, liquid and vapor regions, fuel mixture fraction, and other combustion properties throughout the spray. The test chamber is capable of ambient conditions up to of 50 atm and 800°C to study sprays at conditions similar to those near piston top dead center (minimum volume, maximum pressure and temperature) when a typical diesel engine would inject.

REU Participant’s Role: The participant will work with a team of graduate and undergraduate students to perform tests on the using the experimental systems. They will be trained in the system operation, but also the diagnostics including the use of advanced high-speed cameras. The primary experiments are done to support the development and validation of models for numerically predicting the mixture composition at various ambient conditions. There is significant opportunity for data analysis and programming (using Matlab) to develop algorithms for extracting measurements from the spray videos.

Effect of Perturbations on Shock-Interface Interactions

Faculty Advisor: Dr. Ziyang Huang, Assistant Professor, Mechanical Engineering

Project Description: Compressible multiphase flows are ubiquitous in science and engineering problems, such as inertial confinement fusion, supernova explosions, the safety of aerospace and marine systems, and more. Compressible multiphase flows are characterized by the inclusion of both shock waves and material interfaces, and their interaction is one of the most fundamental questions. This project aims to investigate the effect of perturbations on shock-interface interactions via high-fidelity numerical simulations. Here, the perturbations are broadly defined, including both perturbations to physical configurations (interfaces and shocks), which can induce hydrodynamics instabilities, and perturbations from mathematical models that describe the compressible multiphase flows in numerical simulations. Along with theoretical analysis and validation with experimental data, the outcome of the project will quantify the accuracy of the compressible multiphase flow models to represent physical shock-interface interactions and inspire strategies to control hydrodynamic instabilities.

REU Participants’ Role: REU students will perform high-fidelity numerical simulations with an in-house compressible multiphase flow solver to investigate shocks interacting with multiple gases and liquids under various modes of perturbations. The in-house solver is able to simulate an arbitrary number of different materials with adaptive mesh refinement and high-performance computing. Students will also verify and validate their numerical simulations with shock dynamic theory and experimental data from literature, and perform postprocessing and data visualization.

Rainbow Schlieren Deflectometry

Faculty Advisor: Dr. Ajay Agrawal, Professor, Mechanical Engineering

Project Description: 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.

REU Participant’s Role: The students will be involved in applying the RSD technique to study phenomena such as near injector flow of a fuel atomizer, two-phase flow inside micro-channels, turbulent structure of flames, shock-cell structures of under-expanded jets, temperature in heated jets and flames.