Pavel Popov, Post-doctoral Researcher, Department of Mechanical

SEMINAR
Department of Aerospace Engineering
Computationally Efficient Algorithms for the
Simulation of Rocket Engine Acoustic Instability
Tuesday, March 24, 2015, 4:00 p.m. | HRBB 131
Pavel Popov
Post-doctoral Researcher
Department of Mechanical & Aerospace Engineering
University of California, Irvine
ppopov@uci.edu
ABSTRACT
This talk addresses the problem of screeching acoustic instability in rocket engine combustion
chambers, which is a well-known phenomenon in rocket operation. Screeching instability is
caused by the high energy release of combustion, which can reinforce acoustic oscillations,
causing them to grow to destructive amplitudes. The specific focus of this work is on designs
that are conditionally unstable, so that small-amplitude perturbations inside the combustion chamber decay, but a large
departure from the steady-state operating conditions can lead to the growth of an acoustic wave of significant magnitude.
Such instability-initiating perturbations may come in the shape of a pressure disturbance within the combustion chamber,
an injector blockage or whole-body acceleration of the entire chamber.
A computational procedure has been developed for the prediction of acoustic instabilities in cylindrical and rectangular
combustion chambers: the governing equations are solved on multiple, coupled grids, which are either one- or twodimensional. This allows for a fast simulation, even in a serial run, which enables the exploration of a particular rocket
engine’s stability characteristics over a large parameter space. Comparisons are made between computational results
and experimental data obtained at Purdue University: for a rectangular, seven-injector combustion chamber, the present
computational approach shows good agreement with experiment.
A new computational tool for the analysis of stochastic systems, the Polynomial Chaos Expansion (PCE) method, is used
to solve the stochastic equations in the case when the disturbance is random. In addition to predicting the onset of
acoustic instability, this computational approach can be utilized for the development of strategies to arrest the growth
of an acoustic instability, via an intentional secondary perturbation similar to that which triggered the instability. Results
exploring the stability characteristics of cylindrical and rectangular rocket engine combustion chambers are presented,
and directions for the future development of this computational approach are discussed.
BIO
Pavel Popov received his B.S., M.S. and Ph.D. degrees from the
Sibley School of Mechanical and Aerospace Engineering in
Cornell University; he concluded his graduate research in 2012,
working on particle/finite volume algorithms for turbulent
reactive flows under the supervision of Prof. Stephen Pope.
Presently, Pavel is a post-doctoral researcher in UCI’s
Department of Mechanical and Aerospace Engineering,
performing computational research of rocket engine instability
in collaboration with Profs. William Sirignano and Athanasios
Sideris. In addition to his research work, Pavel has taught
Fluid Mechanics and Heat Transfer classes in UCI. His research
interests include combustion and its applications to propulsion
systems, computational fluid dynamics, high-performance
computing, and stochastic processes.
Fig. 1: Pressure field (in Pa)¬ inside a rectangular combustion chamber during three stages of the development and suppression of a
combustion instability. Left: growing acoustic wave caused by initial
acceleration pulse. Center: suppression of acoustic instability by outof-phase second pulse. Right: decay of acoustic instability to original
operating conditions.