CTR events

When I first arrived at CTR as a postdoctoral fellow in 1992, I could feel deep rumblings beneath my feet. I knew that California was famous for its seismic activity but this was of a different kind. It originated from something called the “Dynamic Model”: the greatest idea in turbulence modeling in a long time that “worked” but did not make sense. I would like to talk
about our efforts to make sense of it all and the intellectual atmosphere at CTR in the 1990’s.

Link to video file:
... Read More

At 30 years old, the Germano identity-based dynamic model for turbulence simulations can be said to have become a classic result for the field of turbulence. In this presentation, I will recall how several of its variants (e.g. Lagrangian, scale-dependent, multiplicative) came about and summarize the main ideas underlying these variations on an elegant theme.

Link to video file:
The dynamic model for LES and variations on the theme

In the immediate aftermath of the 1990 Summer Program, there was a flurry of activities at CTR seeking to exploit the dynamic modeling concept in canonical turbulent flows which heretofore had challenged the universality of turbulence models. I will discuss extensions to compressible flow, scalar transport, reacting flows and other potential formulations
of the dynamic modeling concept that were considered.

Link to video file:
At last, Turbulence closure modeling minus tu... Read More

It was a sunny morning in July 1990, the first week of the CTR Summer Program, Massimo Germano, Parviz Moin, Bill Cabot and Ugo Piomelli met to discuss the possible uses of an identity that Massimo Germano had recently derived. This talk will chronicle how the events of that month produced one of the most influential subgrid-scale models for large-eddy simulations.

Link to video file:
https://stanford.box.com/s/8x6oamqqc9v68ot9d860wq411sgiyzk4

Laser-induced breakdown is a versatile means of depositing energy in a fluid and a promising alternative to conventional electrode-spark ignition for combustion systems.  Using numerical simulations we analyze the flow dynamics following the laser pulse and show that it is sensitive to even subtle alterations in the plasma kernel, which lead to qualitative changes in the flow pattern and ejections of hot gas from the laser focal region.  This sensitivity is leveraged in a dual-pulse configuration, in which the timing and positioning of the pulses can be controlled to enhance dispersal of ho... Read More

Direct combustion noise plays a key role in the triggering and dynamics of thermo-acoustic instabilities of modern gas turbines. Moreover, many combustion devices can produce high levels of noise, while being subjected to stringent noise regulations. Achieving a better understanding of the sound production by premixed flames is important for designing safer and quieter combustion devices. The presented research has for goals to study the mechanisms involved in the sound generation process of turbulent premixed jet flames using DNS. State of the art post-processing methods are used to analyz... Read More

Rocket engines and high-power new generations of jet engines and diesel engines oftentimes involve the injection of one or more reactants at subcritical temperatures into combustor environments at high pressures, and more particularly at pressures higher than those corresponding to the critical points of the separate components, which typically range from 13 to 50 bars for most propellants. This class of trajectories in the thermodynamic space has been traditionally referred to as transcritical. However, the fundamental understanding of fuel atomization, vaporization, mixing, and combustion... Read More

The use of computational fluid dynamics for external aerodynamic applications has been a key tool for aircraft design in the modern aerospace industry. In the last decades, large-eddy simulation with near-wall modeling (wall-modeled LES) has gained momentum as a cost-effective approach for both scientific research and industrial applications. In this talk, we discuss current challenges of wall-modeled LES to become a design tool for the aerospace industry.  We focus first on the working principles and performance of wall-modeled LES for external aerodynamic applications, with emphasis on re... Read More

Shock-induced scalar mixing and ignition under canonical shock-turbulence interactions (STI) will be considered first, by means of Direct Numerical Simulation in 3D and 2D, respectively. The effects of relevant physical parameters (shock and turbulence Mach numbers, and Reynolds number) will be highlighted on statistical changes along the shock-normal direction of scalar variance and dissipation-rate budgets, flow topology, and alignments of the scalar gradient with vorticity and strain-rate eigendirections. Shock-induced scalar mixing will also be addressed by tracking the downstream evolu... Read More

An overview of several available methods for prediction of the transition location is presented. Two particular methods are discussed – the eN method, and the empirical, correlation-based, model of Langtry & Menter (2009). The role of stability theory is explored, including local stability theory, incorporation of non-parallel effects (parabolized stability equations), and extensions into the nonlinear regime. Limitations and drawbacks are pointed out and possible future paths for improvement are highlighted. An area of particular interest is the receptivity stage, where environmental d... Read More