Projects – Research Experience for Undergraduates

Fluid Mechanics with Analysis Using Computations and Experiments

Multi-materials fluid flow for 3D printing of deployable materials

Faculty Mentor: Dr. Tahidul Haque, Mechanical Engineering

Project Description: The growth of the flexible and wearable electronics field hinges on polymeric functional composites for their morphing and actuation performances. At present, we are observing a growing demand for deployable structures for robotics, energy, and biomedical fields. However, the rapid processing technology of distributed sensing in soft polymers is still underdeveloped. Therefore, the objective of this project is to develop customizable additive manufacturing (AM) methods of simultaneous fluidic flow of LM and elastomers to form robust actuation of morphing structures. Primarily, research will focus on the multi-module direct ink writing (DIW) processes of core-shell fibers consisting of LM-elastomer core and LCE shell and their incorporation in autonomous morphing locking (AML) materials. We hypothesize that the core made by embedding LM network in elastomers with a chemical group that covalently bonds with LCE will maintain connectivity without migration of LM droplets during actuation. We will determine the rheological behavior to understand the effect of flow rate as a function of extrusion pressure. Outcome of the project will be the knowledge of the effect of fluid dynamics to design the LM-LCE microstructure, enabling self-sufficient actuation of load-bearing systems for soft robotics, wearable prosthetics, and communication devices.

REU Participant’s Role: The student will get the opportunity to mix and characterize the fluidic flow behavior of different materials. They will work with viscometers to understand the non-Newtonian behavior of the inks and examine the curing quality of printed parts using differential scanning calorimetry. Through an iterative design of nozzle diameter and flow pressure, the students will establish a process-structure-property relation for the composites, leading to a personalized manufacturing protocol for morphing devices.

Unsteady Flow on Axisymmetric Bodies at High Incidence

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

Project Description: Projectiles are expected to perform maneuvers at high angles of incidence to achieve tactical advantages. These slender bodies with conical noses experience large side forces and yaw moments due to flow asymmetry at high angles of incidence. As the angle of incidence of a projectile is increased to moderate angles, the attached flow rolls up into a symmetric vortex pair and the separation becomes asymmetric at high angles of attack, producing large side forces and yaw moments. The vortex asymmetry is due to small perturbations near the tip. The objective of this project is to determine the dynamic switching of the vortex asymmetry direction with the small perturbation. This can be determined by rotating the nose and identifying the response of the vortex asymmetry.

REU Participant’s Role: The experiments will take place in subsonic wind tunnel, and the flow field on the axisymmetric body 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.

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.

Leading-Edge Vortex Breakdown of Delta Wings undergoing Dynamic Pitching and Rolling Motions

Faculty Advisor: Dr. Paul Hubner/Dr. Redha Wahidi, Aerospace Engineering and Mechanics

Project Description: Delta wings with high sweep angles are commonly used in highly maneuverable combat aircrafts and supersonic aircrafts. The flow structure on slender delta wings (normally with sweep angles ( > 65°) at high angles of attack consists of two counter-rotating leading-edge vortices (LEVs), which create a low-pressure region on the suction side of the wing resulting in high lift forces that are as much as twice as high as that of a two-dimensional airfoil. For a stationary delta wing at sufficiently high angles of attack, the LEV expands suddenly, a phenomenon known as a vortex breakdown, which has adverse effects on the lift and pitching moment of the wing. The two main parameters that impact the vortex breakdown are the adverse pressure gradient that the LEV is subjected to and the critical value of its swirl intensity. Increasing any of these parameters by increasing the angle of attack or decreasing the sweep angle promotes an earlier breakdown. The vortex breakdown becomes more complex for a pitching wing at high angles of attack with emphasis on the wing kinematics represented by the reduced frequency. Also, for a pitching wing, a long convective time is required for the vortex breakdown to reach the steady state location after the wing motion has seized. The project aims to explore the universality of the pitching convective time for rolling motion and combined pitching and rolling motions.

REU Participants’ Role: The experiments will take place in subsonic wind tunnel and water tunnel. Qualitative flow visualization and quantitative flow field measurements will be used to determine the breakdown location. The student will be involved in 3D printing of models, setting up experiments in the wind tunnel and water tunnel, develop flow visualization experiments and contribute to writing computer codes to analyze the 3D-PIV data.

Bio-inspired Boundary Layer Control

Faculty Advisor: Dr. Amy Lang, 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.

Internal Combustion Engine Flows

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

Project Description: One of the most significant factors influencing internal combustion engine performance is the fluidic interaction between air and fuel during the intake, compression and combustion processes. Optimizing these interactions can reduce emissions while increasing power and efficiency. Visualizing the air and fuel flows—both individually and simultaneously—helps build a fundamental understanding that supports such optimization efforts. Multiple diagnostic methodologies have been used to characterize these phenomena, including Particle Image Velocimetry (PIV), Planar Laser-Induced Fluorescence (PLIF), and Schlieren/shadowgraphy, among others. These techniques can be applied to analyze either steady-state flow structures or transient mixture development.

The University of Alabama’s engine flow laboratory can conduct both types of assessments by utilizing a steady-flow bench and a reciprocating optical engine, with PIV applied to each test platform. Comparing results from these systems will help identify the relative influence of each flow stream. The goal of this project is to understand and apply the differences observed between the platforms to characterize air–fuel interactions during the mixture preparation process.

REU Participant’s Role: The student will collaborate with a graduate and undergraduate research team to perform flow visualization experiments on both a steady-flow bench and a reciprocating optical engine. The resulting data will be used to validate CFD simulations and to evaluate the usefulness of steady-flow measurements for such validation. Subsequent project stages will extend testing to a running engine and quantify performance impacts associated with flow optimization.

The student will gain hands-on experience with the steady-flow bench, the optical engine, and the associated laser-based and optical imaging techniques, while also developing an understanding of experimental and computational tools used to optimize engine performance.

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.

Investigation of the Lifecycle of Shocklets in Compressible Turbulence

Faculty Advisor: Dr. John Panickacheril John, Aerospace Engineering and Mechanics

Project Description: Compressible turbulence occurs in a wide range of engineering applications and astrophysical phenomena. Examples include inertial confinement fusion, high-speed aerodynamics, supernova explosion, and formation of stars. At high compressibility conditions, in addition to small-scale vortical structures, random shocklets are formed in the flow-field. These structures are very difficult to resolve and can cause numerical instabilities in coarser grids. This project aims to investigate and understand the formation, propagation and dissipation of shocklets and their interaction with the vortical structure in compressible turbulence through highly resolved direct numerical simulations. The insights gained from the project will result in new approaches to modeling small-scale intermittency and subgrid-scale modeling for Large Eddy simulations of compressible turbulence.

REU Participants’ Role: The REU student will part of the team that develops a Lagrangian module in the current in house cDNS code. The student will gain experience in conducting simulations using high performance computing resources along with a gentle introduction to turbulence theory/modeling and shock dynamics.