Research

Current Projects

Multirotor Aerodynamic Interactions for Distributed Propulsion

A confluence of technological advances have enabled emerging opportunities to use flight systems for demanding delivery, transportation, and monitoring applications. These new applications require highly-integrated solutions, often with distributed propulsion systems. Distributed propulsion systems can allow for greater redundancy, control authority, performance, and maneuverability. However, the use of many rotors in close proximity creates strong aerodynamic interactions between rotors and lifting surfaces. CFD and wind tunnel testing can be used to assess these interactions, but these approaches are too expensive to accommodate divergent design exploration. We are developing an analysis and design methodology based on a vortex particle method to more accurately capture wake interactions and perform novel design studies for air taxi applications.

UAS Trajectory Optimization with Multiple Mission-Level Objectives

Many UAS missions have competing objectives and those missions may be supported by different types of aircraft. For example, consider a public service unit that needs to simultaneously monitor a wildfire, track a moving suspect, and search for a lost hiker. We are working on methods to optimally fulfill multiple objectives, that are dynamic (e.g., priorities and tasks may change), and utilize a heterogenous fleet (e.g., fixed wing and rotorcraft).

Conceptual Design of High Altitude Long Endurance Aircraft Using Multidisciplinary Optimization

Aircraft can be used to provide internet in developing areas of the world at a lower cost than deploying new satellites. The challenge is that such aircraft need to be persistent (i.e., stay airborne for months at a time). This drives the aircraft design to very large wing spans in order to reduce lift-dependent drag, and to very high altitudes where wind speeds are low. The performance requirements are demanding necessitating a multidisciplinary design optimization approach considering tradeoffs in aerodynamic performance, structural dynamics, weight, solar energy capture, battery storage, electric propulsion, and cost. We are developing design tools and methodologies, and working on different aircraft design concepts and strategies to help make telecommunication access available in more parts of the world.


Efficient High-Fidelity Aeroelastic Analysis and Design of Long Endurance Aircraft

Related to the above project, ultra-efficient wings that are simultaneously lightweight and large in span, are highly flexible and create unique unsteady aerodynamic and structural dynamic challenges. We are working on high-fidelity approaches to analyze and design such configurations. These challenges are applicable not only to flexible aircraft wings, but also to wind turbine blades and other aeroelastic applications.

High fidelity design often require some manual steps translating between CAD, FEA meshes, and CFD meshes. Isogeometric analysis (IGA) is a generalization of finite element analysis that allows us to operate directly on the geometry without translation from CAD. In addition, with IGA we can provide exact gradients of structural outputs. By tightly coupling structural analyses with computational fluid dynamics, and deriving coupled gradients, we can perform efficient analysis and design of flexible aircraft.


Wind Farm Optimization Under Uncertainty

Effective wind farm optimization involves a large number of design variables and contains many sources of uncertainty (e.g., wind direction, wind speed, turbulence levels, wake model parameters, etc.). We are developing methodology for large-scale optimization under uncertainty with applications in improving the robustness of wind farm energy capture.


Integrated Wind Farm Layout Optimization and Wind Turbine Design

Efficient wind farm layout design is a significant challenge, and today’s wind farms underperform energy capture expectations by around 10-20%. We seek to efficiently combine turbine, layout, and controls optimization in an integrated manner.

We also seek solutions to enable more efficient wind turbine design that include fatigue considerations that are traditionally computationally expensive and noisy.


Quantitative Characterization of Essential Tremor for Future Tremor Suppression

Essential tremor (ET) is one of the most common movement disorders, estimated to affect 1-12 million people in the US. We are developing optimization models in collaboration with the BYU Neuromechanics Research Group to help establish the mechanical origin of the tremor.


Past Projects


VAWT Wake Model Development

Vertical axis wind turbines (VAWTs) are a promising technology for offshore applications and in the built environment. Performance of wind farms is highly dependent on effective integration, and this research is focused on developing engineering wake models for VAWTs to enable farm optimization.


Aeroelastic Rotor Design

We are exploring simultaneous airfoil and blade design through a range of fidelities including pretabulated data, panel methods, 2D CFD, and 3D CFD. We are also exploring full turbine design (rotor, drivetrain, tower, etc.) with coupled aeroelastic models.


Power Estimates for a Novel Vertical Axis Wind Turbine Design

Characterizing the performance of complex vertical axis wind turbine shapes cannot be done with textbook analysis methods. We are investigating the performance of novel VAWT designs using a combination of wind tunnel testing with a custom-built torque sensor, and 3-dimensional unsteady RANS simulations.


Unmanned Aerial Vehicle Trajectory Optimization

Robust UAV trajectory optimization is steeped with challenges including static and dynamic obstacles, performance variability, uncertain environmental conditions, component failures, etc. We are exploring convex optimization approaches, exploratory gradient-based approaches, and UAV aerodynamic performance modeling.


Acoustic Impacts on Wind Farm Layout

Acoustics can play an important role in wind farm design and we are interested in understanding its impact through optimization and in developing better acoustic models for wind farms.


Passive-Flow Control Devices for Low Reynolds Number Propellers

We are conducting wind tunnel tests to characterize performance of novel UAV propeller concepts.


Wind Turbine Design Optimization and Tool Development (Postdoc at NREL)

Efficient extraction of wind energy is a complex, multidisciplinary process. We have developed a number of open-source integrated wind turbine analysis tools as part of the WISDEM toolset. Many of these tools provide exact gradients through automatic differentiation and/or adjoint methods. These tools have supported a number of turbine design studies.


Formation Flight (PhD at Stanford)

We explore a safer approach to formation flying of transport aircraft, which we term extended formation flight. Extended formations take advantage of the persistence of cruise wakes and extends the streamwise separation between the aircraft by at least five wingspans. At large distances, considerations such as wake rollup, atmospheric effects on circulation decay, and vortex motion become important to consider. We examine the wake rollup process in the context of extended formations and develop appropriate physics-based models.