Research

My CV (pdf) summarizes my past work. Google Scholar Citations lists my publications. My academic publications and presentations are also archived online here. Some additional details are below.

Water jet breakup and trajectory

I am researching the breakup and trajectory of liquid jets, with a focus on fire protection applications. The overall goals of this research are to understand the factors influencing the trajectory of a water jet, predict the trajectory of a water jet, and improve the range of water jets. There is much experimental research on the trajectory of large water jets, but the vast majority of it is poorly characterized and does not measure anything related to the breakup of the jet. Neither does most theories, though mine does. I am currently planning a series of experiments to examine the influence of the breakup length on the trajectory of water jets.

The effect of different nozzle geometries on the breakup and trajectory of large water jets has been known for a long time. Towards understanding the influence of nozzle geometry on turbulent jet breakup, I've developed a new theoretical framework which I call conditional damped random surface velocity (CDRSV) theory. This framework is a fair bit more careful than previous simple theories. For validation of CDRSV theory I compiled a large experimental database using data from long pipes (abstract; more on the data compilation will be published later). Using a regression to relate the pipe friction factor to turbulence intensity and including rough pipes, I was able to estimate the influence of turbulence intensity on many breakup quantities. Current CDRSV theory does not adequately represent the experimental data, but the theory generally does better than previous comparable theories. After my PhD I will investigate improved CDRSV theories.

Publications

B. Trettel and O. A. Ezekoye, "Theoretical range and trajectory of a water jet", in Proceedings of ASME 2015 International Mechanical Engineering Congress and Exposition, Houston, TX, 2015. DOI: 10.1115/IMECE2015-52103. (Currently being rewritten, updated, corrected, and improved for publication in a journal.)

B. Trettel, "Conditional damped random surface velocity model of turbulent jet breakup". Submitted to ICLASS 2018, Chicago, IL, 2018. Preprint DOI: 10.17605/OSF.IO/35U7G.

B. Trettel, "Estimating turbulent kinetic energy and dissipation from internal flow loss coefficients". Submitted to ICLASS 2018, Chicago, IL, 2018. Preprint DOI: 10.17605/OSF.IO/QSFP7.

Lagrangian particles in FDS

For NIST, I develop and test Lagrangian particle methods for the Fire Dynamics Simulator (FDS). Examples of Lagrangian particles include water droplets from fire suppression systems and fuel droplets. Recent work has focused on developing verification tests and fixing bugs in FDS.

Past research

Outflow boundary conditions for buoyancy-driven flows

For my Master's research at UMD, I tested different types of outflow boundary conditions for buoyancy-driven flows. Tim Colonius notes that open boundary conditions present "an open and substantial modeling problem that is no less challenging, and arguably no less important, than subgrid modeling for turbulence." Thus, I explored several different approaches and compared their successes and failures. My Master's thesis is available online. This work was not particularly good, but I was learning at the time. I believe the literature review is the most useful part of this work. Today (2018) I remain interested in improved boundary conditions and am considering returning to this area after my PhD.

Publication

B. Trettel, "Outflow boundary conditions for low-Mach buoyant computational fluid dynamics," MS thesis, University of Maryland, College Park, 2013. URL: http://hdl.handle.net/1903/14700