Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session H05: Detonation and Explosives 
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Chair: Mark Short, LANL Room: 204 
Monday, November 25, 2019 8:00AM  8:13AM 
H05.00001: The Effects of Parasitic Combustion on Detonation Wave Propagation Supraj Prakash, Venkat Raman Rotating detonation engines (RDEs) are a feasible approach to realizing pressure gain combustion. However, practical implementation of these devices requires the use of nonpremixed discrete fueloxidizer injection. Turbulent mixing of the fuel and oxidizer streams enforces reactant stratification inside the combustor annulus. Parasitic deflagrative combustion of the freshlyinjected fueloxidizer mixture introduces partiallyburnt gases to the detonation wave and diminishes heat release. Numerical studies of fullscale RDE systems have suggested that up to 3550\% preburning of the fueloxidizer mixture is prevalent within the combustor. The primary objective of this work is to understand the interaction of the detonation wave and a spatiallyinhomogeneous mixture. To this end, a highfidelity numerical simulation approach is utilized to understand how partiallyburnt mixtures affect the detonation wave structure by inducing different fractional levels of reactant mixture preburning with reference to the fullyburnt equilibrium state. The effect of preburning on detonation wave stability and characteristics are discussed to provide insight into the difference between theoretical ChapmanJouguet detonation and the detonative combustion observed in practical combustors. [Preview Abstract] 
Monday, November 25, 2019 8:13AM  8:26AM 
H05.00002: Quantification of Detonation Augmentation by Secondary Waves in a Rotating Detonation Combustor Fabian Chacon, Mirko Gamba In this work we will investigate the system of waves present in a laboratory scale rotating detonation combustor (RDC). These devices are of scientific interest because of the theoretical efficiency gain that can be achieved through the utilization of these devices in a jet engine or other conventional combustor. However, the flow fields within RDCs are complex and not fully understood, nor are many of the mechanisms behind some of the phenomena associated with a RDC. One such phenomena is termed secondary waves: waves (apart from detonation) which have some associated pressure oscillation, chemical reactions, or both travelling at a consistent speed while the combustor is under operation. In particular, we will use a newly developed analysis technique that allows for the quantification of spatial distributions of pressure throughout the operation of the RDC. This will allow for determining the impact that the secondary wave has on the pressure rise of the detonation wave when they collide in the channel. Understanding how significant the impact of these collisions are, will allow for greater understanding of the role these secondary waves will play into the operability and stability of a RDC and its integration into a practical system. [Preview Abstract] 
Monday, November 25, 2019 8:26AM  8:39AM 
H05.00003: Effects of nonpremixed injection schemes on the detonation structure in rotating detonation engines Takuma Sato, Venkat Raman Recently, RDEs has been getting more attention as the pressure gain combustor. Because it uses the detonation in the combustion process, the reactant mixture can get additional compression due to the shock wave. Although a series of simulations have been conducted in the community, most of them are limited in the canonical problems and the premixed assumption in a 2D geometry. In the real RDEs system, the nonpremixed injection system creates a complex detonation structure due to the incomplete mixing and the stratification of the fuel and oxidizer. However, the measurement of the detailed flame structure is hard to obtain in the experiment due to the harsh environment of the system. With this mind, the goal of this study is to understand the detailed 3D detonation structure by simulating the full system RDEs system. Because the flowfield is highly unsteady in time and space, the 3D averaged flowfield will be extracted from the simulation. The heat release distribution in the space will be extracted to understand the combustion process in the detonation chamber. The mixing process of the nonpremixed injection system will be discussed by varying the mass flow rate. Finally, the comparison between the Euler and NavierStokes equations will be discussed.~ [Preview Abstract] 
Monday, November 25, 2019 8:39AM  8:52AM 
H05.00004: Analysis of mode transition in Rotating Detonation Engines using detailed numerical simulations Prashant Tarey, Praveen Ramaprabhu, Jacob McFarland, Douglas Schwer Detonation Engines (RDE) can operate in single or multiple detonation wave modes, while the mode of operation depends on several factors including the equivalence ratio, mass flow rate etc. In this work, we analyze the mechanism of mode transition through detailed numerical simulations of a 2D unrolled RDE geometry with discrete injectors. We systematically vary the equivalence ratio of the hydrogenair mixture in our simulations with 1step chemistry. The different modes of operation and the parameter boundaries separating them, were investigated and compared with experimental$^{\mathrm{1}}$ results. Our results show that the number of waves is proportional to the equivalence ratio as well as the detonation cell width. The effect of the detonation modes on thrust and detonation height were also investigated. The compressible Euler simulations were solved on a Cartesian grid with Adaptive Mesh Refinement, using the Piecewise Parabolic Method (FLASH$^{\mathrm{2}})$, while a secondorder accurate, Immersed Boundary Method was implemented to model the discrete injectors. $^{\mathrm{1}}$A. George et al., Proc. Comb. Inst., 36 (2), 2691, (2017). $^{\mathrm{2}}$B. Fryxell et al., Astrophys. J., Suppl. Ser. 131, 273 (2000). [Preview Abstract] 

H05.00005: ABSTRACT WITHDRAWN 
Monday, November 25, 2019 9:05AM  9:18AM 
H05.00006: Numerical Investigation of the Accuracy of Particle Image Velocimetry Technique in GasPhase Detonations Sai Sandeep Dammati, Yoram Kozak, Kareem Ahmed, Alexei Poludnenko In this study, we numerically investigate the accuracy of the Particle Image Velocimetry (PIV) technique for the flow characterization in highspeed, compressible regimes, and in particular in gasphase detonations. A twodimensional, planar detonation at atmospheric conditions is modeled using a simplified singlestep Arrhenius kinetics. The upstream flow is uniformly seeded with particles representing the $Al_2 O_3$ PIV particles used in experiments, along with initially colocated massless Lagrangian tracers used to recover the correct particle trajectories in the flow field. Massless Lagrangian particles are integrated using both 2nd order and 4th order time integrators to further assess the errors in the reconstructed Lagrangian trajectories. By comparing the trajectories of massive particles with those of the tracer particles, we address the following questions: a) How do PIV particles affect the detonation wave, in particular its velocity and cellular structure? b) How closely do massive PIV particles follow the flow pathlines? c) What is the accuracy of the flow field reconstructed using the PIV particles? Finally, we discuss the implications for the use of the PIV technique as a diagnostic tool for highspeed reacting flows such as detonations in detonationbased engines [Preview Abstract] 
Monday, November 25, 2019 9:18AM  9:31AM 
H05.00007: Studies of Flame Stability and Thermal Choking Limits in Scramjets with Hydrogen, Methane, and Ethylene Fuels Wenhai Li, Ladeinde Foluso A few results on flame stability and thermal choking in a simplified model of the scramjet engine will be presented for hydrogen, methane, and ethylene fuels which are injected in crossflow to a supersonic airflow in a combustor. The parameter space investigated includes a range of air stagnation temperatures ($T_{0})$, jettofreestream momentum flux ratios ($J)$, and the three fuels. The analysis is done via the largeeddy simulation and within the context of the flamelet approach. Preliminary results show that hydrogen and ethylene have similar thermal chocking limits in terms of $T_{0}$ and $J$, while the methane flames are quite difficult to maintain under the current test conditions. [Preview Abstract] 
Monday, November 25, 2019 9:31AM  9:44AM 
H05.00008: Modeling of the Cellular Structure of Detonation in Liquid Explosives Luke Edwards, Mark Short Detonation waves propagating in some liquid explosives such as nitromethane (NM) are known to exhibit complex cellular patterns reminiscent of those observed in gaseous explosives. Such cellular structures in NM/diluent mixtures have been recorded by framing camera images (Fickett and Davis 1979). The origins of such instabilities are disputed, ranging from hydrodynamically generated instabilities to failure waves propagating into the detonation reaction zone from the NM/confiner boundary. Detonation front shapes measurements by streak camera imaging in NM/diluent mixtures, on the other hand, mostly show smoothly curved shock fronts, which appear to contradict the observed presence of cellular instabilities. We also know that detonations in NM mixtures are carbon rich, which results in a spatially elongated zone of carbon coagulation behind a much thinner main reaction layer. In this work, we examine the potential origin of the observed cellular detonation instabilities in NM mixtures via an asymptotic theory that explicitly accounts for the long carbon coagulation region. The theory explores why the presence of cellular instabilities may not manifest themselves on the detonation shock front. [Preview Abstract] 
Monday, November 25, 2019 9:44AM  9:57AM 
H05.00009: Steady Detonation Propagation in Thin Channels with Strong Confinement Mark Short, Stephen Voelkel, Carlos Chiquete We examine asymptotically the dynamics of 2D steady detonation wave propagation and failure for a strongly confined high explosive (HE), where the width of the explosive is small relative to the reaction zone length. An energy balance equation is derived which shows how the longitudinal acceleration of subsonic flow behind the detonation shock is influenced both by chemical reaction and by the effects of HE boundary streamline deflection, specifically via the induced rate of change of mass flux through the detonation wave. The latter serves to either counteract or reinforce the acceleration of longitudinal flow depending on the gradient of the boundary streamline deflection. The analysis is valid for general equationsofstate and chemical reaction rates in the HE. The energy equation represents an eigenvalue problem for the detonation phase speed. We explore specific results for the ideal and stiffenedgas equations of state, along with a pressuredependent reaction rate for which changes in the pressure exponent and reaction order are also studied. We consider the influences of both straight and curved HE boundary streamline shapes. The asymptotic analysis reveals significant physical insights into how detonation propagation and failure is affected by strong confinement. [Preview Abstract] 
Monday, November 25, 2019 9:57AM  10:10AM 
H05.00010: The effect of the thermodynamic closure on shocktodetonation transition modeling in condensedphase high explosives Carlos Chiquete, Mark Short, Stephen Voelkel The need for accurate prediction of detonation initiation and propagation in high explosives (HEs) has lead to various empirical constitutive models for the HE's equation of state (EoS) and reaction rate. These experimentally calibrated models are used at the continuum level where it is possible to efficiently calculate detonation wave motion at the engineering scale. A transition from the (solid) reactant to the (gas) product state occurs via a single irreversible reaction, requiring a closure condition between the two phases which must then coexist in a single material element. Different closures have been used in the past, for example, pressuretemperature equilibrium. However, analysis of more physical, explicitly 2phase modeling approaches where each phase's thermodynamic state can evolve have shown that temperature equilibration occurs over a much longer time scale than the corresponding reaction zone scale. Nevertheless, this "nonphysical" closure has been shown to capture the shocktodetonationtransition (SDT) for many HEs. To clarify this, we systematically vary the closure condition and isolate its effect by fixing the EoS models and reaction rate form. Computational results using the various closures will then be compared and contrasted with respect to SDT data. [Preview Abstract] 
Monday, November 25, 2019 10:10AM  10:23AM 
H05.00011: Analysis of Detonation Driving Zone in CondensedPhase High Explosives at Varied Confinements Stephen Voelkel, Carlos Chiquete, Mark Short Lateral yielding of confiners used in detonations of condensedphase high explosives (HEs) introduces streamline divergence into the flow and subsequently reduces the steady detonation's phase velocity to below its planar ChapmanJouguet (CJ) limit. The resulting phase velocity is determined by the subsonic flow region behind the shock front, denoted the detonation driving zone (DDZ). The DDZ itself is dependent on the HE material properties, the thickness of the charge, and the confiner properties. Holding all else equal, at infinite thickness the phase velocity approaches the CJ limit. As the thickness decreases, so to does the phase velocity until the thickness reaches some critical value, below which the detonation is unable to sustain itself. In this work, we consider an idealized HE material and simulate steady detonations over a wide range of confinements. For each confinement, simulations at varied thicknesses between the CJ and critical limits are performed and analyzed. Correlations of the DDZ with the phase velocity are presented, with a specific focus on structures and relations that are independent of the confinement. Furthermore, we show that properties within the DDZ correlate with the critical thickness. [Preview Abstract] 
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