Graduate Research

A graduate student working on a research project in a lab

Graduate students advised by MME faculty are enrolled in the Mechanical Engineering graduate program (MCH) or other graduate programs at Miami. Graduate students in the MCH program perform either thesis-based or project research, depending on the option they have chosen.

We have numerous MME faculty actively involved in research. The general areas include materials, system dynamics and control, thermo-fluid sciences, medical devices and mechatronics, manufacturing systems, and learning technologies. Students interested in pursuing graduate research are encouraged to consult individual faculty regarding their research interests.

Research is performed in  MME department laboratories, on Miami's Redhawk supercomputing cluster, in laboratories of other departments, or in laboratories worldwide.

Recent external collaborations have included the Air Vehicles and Materials directorates at Wright-Patterson Air Force Base, DuPuy Orthopaedics, Ethicon Endosurgery, General Electric, and Edison Welding Institute.

Current & Past Projects

Optimization of Control Surface Parameters Towards Active Aeroservoelastic Control Using the Method of Receptances

In order to further the capabilities of high performance aircraft, receptance based active aeroelastic control (AAC) strategies have been developed to eliminate flutter instabilities and to increase flutter boundaries in avoiding structural fatigue or potential failure. This method relies completely on frequency response functions obtained from embedded sensors and actuators along a given wing planform. It does not need accurate aeroelastic model for controller design and it has been shown to be effective for designing AAC for controlling desired aeroelastic modes.  In order to maximize the functionality of the single and multiple input AAC control by the available control surfaces, an optimization study of a given wing configuration is needed. This includes, but is not limited to, the sizing and placement of control surfaces, the number of needed control surfaces, and the optimal actuator parameters associated with the control surfaces.  The design parameters for the optimization studies considered for this study include the size of the individual control surfaces for the case of fixed/chosen number of control surfaces on the wing configuration, and the optimal number and location of control surfaces on a given wing configuration. The objective is to minimize the controller norms (control efforts required by the control surfaces) to extend the open loop flutter boundaries. Optimization process involved the developments of the controller with (i) unique control gain parameters for an entire flight envelope, (ii) capabilities of partial pole assignment to suppress the prescribed aeroelastic modes without influencing any other modes, and (iii) ability to incorporate actuator dynamics such that AAC can be implemented for wide range of actuators without the spill-over of actuator modes. A multivariate optimization problem is developed and various optimization strategies such as the genetic algorithm and multi-start gradient based approaches were used to estimate the optimal sizing and placement parameters for the control surfaces. Numerical optimization studies involving simplified wing models and a delta fighter wing model are investigated in demonstrating the effectiveness of the controller performance with the optimal control surface configurations.

Reduction of Vibration by Oscillating Boundaries and its Application in Rotordynamics

The lifespan of the structural components deteriorate when they are subjected to vibration environment, leading to potential fatigue and failure. In these scenarios vibration control or isolation plays a major role in preventing failure and improving the product life. For example, in the field of rotordynamics, rotating components are naturally subjected to vibration, due to inherent unbalance in the rotor systems. There rotor systems such as motors, pumps and turbines are essential in transportation and energy industries.   In industry, during their operations the rotor system is subjected to range operating speeds (vibration environment) and they need to satisfy the industrial standard (limits) of acceptable vibration amplitude. The dynamics of these systems needs to be understood such that a better control strategy can be implemented to satisfy the safety standards and to avoid any potential catastrophic failure. Traditionally, passive and active control designs are implemented to minimize the undesirable vibration. In some cases, these methods may not be feasible, economical or practical. Therefore, the research objective of this project is to investigate a new mechanism for reducing, eliminating and/or controlling the vibration of a given structure, by oscillating the boundaries of the structure. The hypothesis is that by continuously moving the support position, the natural frequency of the system can be manipulated. This avoids the system to stay near the resonance and therefore not allow for the response to grow continuously reaching catastrophic levels. To investigate this approach, at first, a vibrating beam was investigated to understand the relationship between the natural frequency and the motion of the end support. By using associated discrete finite dimensional models, time and frequency domain analyses were carried and the results were compared with available analytical solutions for accuracy. This approach is further tested in complex rotor models, which are defined by large degrees of freedom and have speed dependent properties. The large rotordynamic systems subjected to oscillating boundaries are modeled in finite element framework and then solved numerically in modal co-ordinates. The relationship among the critical speeds of the rotors, frequency and amplitude of boundary (bearing) support and stability of the overall system is investigated. The parametric studies demonstrate that the overall vibration of the system can be minimized by prescribing the boundary (bearing) oscillation.   

Structural Response of Conical Structures due to Combined Thermal and Structural Loading using Reduced Order Modeling

The idea of being able to travel at hypersonic velocities during atmospheric flight presents a near-infinite list of possibilities for the advancement of air travel. This includes the technology that will allow for the development of commercialized hypersonic flight as the first step towards routine commercial space flight. The types of vehicles that will be able to make these voyages will need to be specially engineered in order to withstand the environmental conditions in-flight without the structures of these vehicles being subjected to fatigue and failure during operation. The hypersonic aircraft design problem is a complex application of mechanical engineering that provides a unique challenge to most engineers.

The major reason that the hypersonic aircraft design problem is a complex application is that there are three main aspects of mechanical engineering integrated into the problem: structural mechanics, thermodynamics, and aerodynamics. These three aspects of design are heavily linked, and have a considerable effect each other. Additionally, all design aspects directly affect the structural response for a given set of flight conditions. For example, the thermal loading on the exterior of the aircraft cause by friction associated with the fluid flow can have a major effect on the structural response due to thermally-induced changes in the material properties.

The method that has been utilized by most of the literature currently available in this research area to examine these linked effects is the reduced order modeling technique. The use of these methods results in a modal system that is representative of the important modes in the physical model described by a system of coupled differential equations written in matrix form. The modal system is determined using decomposition methods that reduced the physical system from a larger dimension n to a smaller dimension r capturing only those modes of the system that are necessary to describe the response of the system. The resulting decoupled system of ordinary differential equations can then be solved to find the closed-form solutions to the original system by way of reversing the order of transformations used in the decomposition process. The main objective of this work is to, after developing a reduced-order model for both the structural and thermal loads on the structure, determine whether the structural and thermal reduced-order models of the system can interact in such a way that the total structural response is observable using the combined models.

A Numerical Model of a Two-Pass, Cross-Flow Conformal Heat Exchanger for Aerospace Applications

Heat exchangers have seen widespread use in aerospace applications to properly manage aircraft and propulsion system heat loads. However, these heat exchangers are typically large (in terms of volume and weight relative to flowrate), non-conformal and costly to implement. There is motivation for heat exchangers to be better integrated into flow paths, both for packaging and performance improvements. Recent advances in additive manufacturing have presented the potential to create highly conformal and better optimized heat exchangers. These additively manufactured, flexible geometry heat exchangers have the potential to reduce pressure losses and increase thermal performance when compared to rectilinear, traditionally manufactured heat exchangers.

In this work, a computational tool was developed to predict the thermal-hydraulic performance of an annular two-pass, cross-counterflow heat exchanger. Area ruling was used to keep velocities nearly constant in the heat exchanger core. Computational tool outputs include heat transfer rate, outlet temperature, pressure loss characteristics, heat exchanger weight, and volume as a function of user-supplied geometric inputs. A brief optimization was performed across multiple mass flow rates to determine best designs. Pumping power and modified volume goodness were used to perform optimization. Using the geometries provided by the computational tool, a heat exchanger will be manufactured using additive techniques and tested across a range of conditions. The experimental results will help validate the computational tool.