Ralf Deiterding

University of Southampton · Aerodynamics and Flight Mechanics Research Group

The authors examine the effects of inhomogeneity in the equivalence ratio on detonation propagation by using a set of two-dimensional numerical simulations of the detailed reaction chemistry of an H 2 /air mixture. A random field of fluctuations but with statistical characteristics is introduced, and several combinations of the root mean square (RM...

This numerical study investigates the effects of adding a small amount of ignition promoters for controlling the wedge-induced oblique shock wave (OSW) to oblique detonation wave (ODW) transition in a premixed hydrogen–air mixture at hypersonic speeds. The time-dependent two-dimensional compressible Euler equations for multiple thermally perfect sp...

The oblique detonation induced by a two-dimensional semi-infinite wedge is simulated numerically with the Navier-Stokes equations and a detailed H 2 /air reaction model based on the open source program AMROC Adaptive Mesh Refinement in Object-oriented C++. A spatially seventh-order-accurate WENO scheme is adopted for the convective flux discretizat...

This study presents an improved ghost-cell immersed boundary method for geometrically complex boundaries in compressible flow simulations. A bilinearly complete extrapolation scheme is developed for the reconstruction of the ghost-cell. The second-order accuracy of the improved ghost-cell method (GCM) is shown in unit test cases and is also theoret...

A generic solver in a structured Cartesian adaptive mesh refinement framework is extended to simulate unsteady shock-induced combustion problems on a structured curvilinear mesh. A second-order accurate finite volume method is used with a grid-aligned Riemann solver for inviscid thermally perfect gas mixtures. To solve these reactive problems, deta...

Seeking to better understand the physical phenomena underlying detonation wave propagation through small holes (especially the phenomenon of detonation re-initiation or its failure), we investigated the propagation of a detonation wave along a tube filled with a hydrogen-oxygen mixture diluted with argon, in the presence of obstacles with a small o...

We studied the mechanisms of flame acceleration (FA) and deflagration to detonation transition (DDT) triggered by a combination of solid and jet obstacles. The Navier–Stokes equations with a detailed hydrogen–air kinetics model were utilized. Vast Kelvin–Helmholtz instabilities generate intensive turbulence–flame interactions, leading to an increas...

View Video Presentation: https://doi.org/10.2514/6.2021-3529.vid Direct gas injection in the shocked or compressed region has importance in many applications from drag control to ignition and pressure gain combustion. This numerical study is focused on direct light gas injection into the stagnation zone of a blunt nose at hypersonic speed, aiming t...

View Video Presentation: https://doi.org/10.2514/6.2021-3658.vid A modular laboratory rotating detonation engine (RDE) for combined mass flow rates below 10 g/s has been designed. Since a large chamber diameter to width ratio is used, first tests with stoichiometric ethylene-oxygen mixtures have revealed detonation modes with one, two and three sep...

Modes of detonation wave propagation in annular channels were investigated numerically by using the adaptive mesh refinement technique. Two-dimensional, reactive Euler equations with a detailed hydrogen/oxygen reaction model were adopted in the computations to simulate the detonation dynamics in the annular geometry. Considering both the decoupling...

The difference of flow characterization at the different stages of flame acceleration and detonation transition in tubes with smooth wall, solid obstacles, and fluidic jets is studied, especially the effects of flow instabilities on the process. The two-1 dimensional viscous unsteady reactive Navier-Stokes equations with detailed chemistry model ar...

This volume collects the most important contributions from four minisymposia from ICIAM 2019. The papers highlight cutting-edge applications of Cartesian CFD methods and describe the employed algorithms and numerical schemes. An emphasis is laid on complex multi-physics applications like magnetohydrodynamics, combustion, aerodynamics with fluid-str...

We detail the verification of the WALE large eddy simulation turbulence model for application in cell-based lattice Boltzmann methods, as implemented in our generic Cartesian structured adaptive mesh refinement framework AMROC. We demonstrate how to effectively apply the test case of decaying homogeneous isotropic turbulence to verify the core WALE...

A rescaling methodology is developed for high-fidelity, cost-efficient direct numerical simulations (DNS) of flow through porous media, modelled at mesoscopic scale, in a hypersonic freestream. The simulations consider a Mach 5 hypersonic flow over a flat plate with coolant injection from a porous layer with 42 % porosity. The porous layer is desig...

A combined numerical-experimental investigation is presented with focus on the effects of boundary-layer instabilities and transition on the wall cooling performance in a Mach 5 low-enthalpy flow over a flat plate, with coolant injection achieved through a row of slots. The numerical study has been performed through direct numerical simulation (DNS...

Plasma disturbances affect satellites and spacecraft and can cause serious problems to telecommunications and sensitive sensor systems on Earth. Considering the huge scale of the plasma phenomena, data collection at individual locations is not sufficient to cover this entire relevant environment. Therefore, computational plasma modelling has become...

The present work studies numerically the quasi-steady propagation of a hydrogen/oxygen detonation in a supersonic model combustor consisting of a cavity and an expanding wall. The two-dimensional reactive compressible Navier-Stokes equations with one-step and two-species reaction model are solved using a hybrid sixth-order Weighted Essentially Non-...

Numerical simulations are employed to investigate the dynamical separation of an initially stationary sphere from the surface of a two-dimensional ramp in hypersonic flow. We consider the inviscid limit, which is effectively equivalent to assuming the sphere radius to be much larger than the ramp boundary-layer thickness. Of particular interest is...

In rotating detonation engines and explosion accidents, detonation may propagate in an inhomogeneous mixture with inert layers. This study focuses on detonation propagation in a stoichiometric H2/O2/N2 mixture with multiple inert layers normal to the detonation propagation direction. One- and two-dimensional simulations considering detailed chemist...

In the current study, the separation of equal-sized spheres from initial touching configurations at Mach 20 is examined through numerical simulations using a coupled CFD/FEA solver. Comparison of computational results with free-flight wind tunnel trajectories is conducted, and modest dependence on viscosity is observed, namely in the form of enhanc...

The conventional lattice Boltzmann method is restricted to Cartesian grids, making it remarkably expensive for capturing thin boundary layers, and therefore impractical for most relevant problems in aerodynamics. In this paper, a finite difference approach is taken to solve the discrete-velocity Boltzmann equation in generalised curvilinear coordin...

We detail the verification of the WALE large eddy simulation turbulence model for application in cell-based lattice Boltzmann methods, as implemented in our generic Cartesian structured adaptive mesh refinement framework AMROC. We demonstrate how to effectively apply the test case of decaying homogeneous isotropic turbulence to verify the coreWALE...

Plasma disturbances affect satellites, spacecraft and can cause serious problems to telecommunications and sensitive sensor-systems on Earth. Considering the huge scale of the plasma phenomena, data collection at individual locations is not sufficient to cover this entire relevant environment. Therefore, computational plasma modelling has become a...

Second-order curved shock theory is developed and applied to planar and axisymmetric curved shock flowfields. Explicit equations are given in an influence coefficient format, relating the second-order gradients of pre-shock and post-shock flow parameters to shock curvature gradients. Two types of applications are demonstrated. First, the post-shock...

Dynamic mesh adaptation methods require suitable refinement indicators. In the absence of a comprehensive error estimation theory, adaptive mesh refinement (AMR) for nonlinear hyperbolic conservation laws, e.g. compressible Euler equations, in practice utilizes mainly heuristic smoothness indicators like combinations of scaled gradient criteria. As...

Compressible multi-material flows are characterized by complex flow structures with a broad range of length scales and discontinuities associated with material interfaces and shock waves. High order and high resolution numerical methods are required to capture material interface as sharply as possible and to increase the resolution of complex struc...

The main objective of this work is to identify the end-gas combustion mode transition under different initial thermodynamic conditions and to focus on the role of pressure waves in autoignition formation and detonation development in the confined space by a group of two-dimensional (2D) numerical simulations with detailed chemistry of H₂...

Two-dimensional numerical simulation is performed with the open-source program AMROC to study the effects of transverse jets (act as fluidic obstacles within a detonation tube) on the flame acceleration and deflagration to detonation transition (DDT). The slot transverse jets have been studied and compared with conventional solid obstacles in tubes...

The present work describes latest advancements in the context of high-fidelity numerical simulations of flow through porous media in a hypersonic freestream. The aim of this work is to find an appropriate solution to the challenging requirement of accurately resolving complex multiscale flow features combined with minimum computational cost, as wel...

In the present work, detonation stabilization in the supersonic flow is numerically investigated in the straight channel with suction boundaries. The two-dimensional reactive Navier–Stokes equations, together with a one-step reaction model, are solved using a second-order-accurate finite volume method solver based on the Structured Adaptive Mesh Re...

A second-order central time-explicit method is implemented to solve the Lattice Boltzmann Equation in generalized curvilinear coordinates in order to simulate fluid flows with non-uniform grids and curved boundaries. Several test cases are used for verification, including the Taylor-Green vortex in two-dimensions, the square lid-driven cavity and t...

In this paper, we present our recent work on single relaxation Lattice Boltzmann method and Large Eddy Simulation (LES) models, namely the dynamic Smagorinsky and wall-adapting local eddy-viscosity (WALE). Initially, forced and decaying homogeneous isotropic turbulence cases were run to compare direct numerical simulations with LES. Moreover, the T...

Here, short duration direct numerical simulations of shock water cylinder interaction in a two-dimensional channel are conducted to study shock wave attenuation at time scales smaller than the cylinder convection time. Four different cylinder configurations, i.e., 1x1, 2x2, 3x3, and 4x4, are considered, where the total volume of water is kept const...

Computational magnetohydrodynamics (MHD) for space physics has become an essential area in understanding the multiscale dynamics of geophysical and astrophysical plasma processes, partially motivated by the lack of space data. Full MHD simulations are typically very demanding and may require substantial computational efforts. In particular, computa...

Results from Direct Numerical Simulations (DNS) of the Navier-Stokes equations are presented for the case of a Mach 5 low-enthalpy flow over a flat plate with coolant injection achieved through a row of slots. In particular, a slotted flat-plate configuration with four equally-spaced span-periodic slots has been considered, representative of a real...

In this paper, we verify the newly implemented Large Eddy Simulation (LES) models, namely the Dynamic SMAgorinsky (DSMA) and the Wall-Adapting Local Eddy-viscosity (WALE) in our Lattice Boltzmann Method (LBM) solver. The test cases of Forced Homogeneous Isotropic Turbulence (FHIT) and Taylor Green Vortex (TGV) were employed for this purpose. Direct...

In the present work, dynamic detonation stabilization in expanding channels is numerically investigated by injecting a hot jet into a hydrogen–oxygen combustible mixture flowing at supersonic speed. The two-dimensional reactive Navier–Stokes equations and one-step two-species reaction model are solved using a hybrid sixth-order WENO-Centered Differ...

The main objective of this work is to comprehensively provide a fundamental understanding of the entire process of the flame-pressure wave interactions with end-gas autoignition and detonation development in a confined chamber by two-dimensional numerical simulations with a stoichiometric hydrogen/air mixture. The flame dynamics, pressure wave prop...

The main objective of this work is to comprehensively provide a fundamental understanding of the entire process of the flame-pressure wave interactions with end-gas autoignition and detonation development in a confined chamber by two-dimensional numerical simulations with a stoichiometric hydrogen/air mixture. The flame dynamics, pressure wave prop...

As velocities of high speed trains increase, the loads created by pressure waves ahead and after a train have become an important design criterion. Predictive aerodynamic simulation of these transient phenomena requires an efficient approach to simulate the air flows around vehicles that move through a geometrically complex environment. Here, we de...

High fidelity DNS simulations of the complex flow physics of a hypersonic boundary layer interacting with the coolant flow of a porous surface require a multiscale simulation approach. We employ a high-order hybrid WENO scheme, multiblock domain treatment in conjunction with massively parallel computating and an efficient mesh adaptation methodolog...

In this work, the trajectories of spherical particles shed from the surface of a simple two-dimensional ramp in high-speed flow are examined numerically and experimentally. First, inviscid numerical simulations are performed, examining the interactions of the particle solely with the ramp-generated oblique shock, then including the effects of the r...

Computational magneto-hydrodynamics (MHD) for space physics has become an essential area in understanding the multi-scale dynamics of geophysical and astrophysical plasma processes, partially motivated by the lack of space data. Full MHD simulations are typically very demanding and may require substantial computational efforts. In particular, comp...

Compressible two-phase flows were simulated based on the five-equationmodel under the Adaptive Mesh Refinement (AMR) framework to balance therequirements between space resolution and computational cost. And the simulation system was established in an open source software AMROC (Adaptive Mesh Refinement Object-oriented C++). A combination of Godunov...

Detonation initiation has been extensively investigated in the past several decades. In the literature, there are many studies on detonation initiation using huge blast energy and obstacles to respectively achieve direct detonation initiation or deflagration to detonation transition (DDT). However, there are few studies on detonation initiation wit...

The fluidic jet turbulator has been a novel perturbation generator in the pulse-detonation engines research field for the past few years. In this paper, an experiment is performed to study the deflagration to detonation transition (DDT) process in a detonation chamber with a reactive transverse methane–oxygen mixture jet in crossflow (JICF). The je...

Adequate resolution of the flow field is vital to ensure that simulations are sufficiently spatially converged. However, a too finely resolved mesh can lead to excessive computational times. Adaptive Mesh Refinement (AMR) algorithms are able to balance these two constraints by increasing the resolution only where it is needed. In this work, a block...

Flow at hypersonic speeds is characterised by severe heat loads at the wall that can lead to the failure of the vehicle structure. Most passive-cooling thermal protection systems (TPS) make use of a low-density porous material to decrease the thermal conductivity and the heat transfer in the inner structure. Porosity plays in turn an important role...

A consistent mesh refinement study, relating to the prediction of aerodynamic forces about an experimentally validated reference train geometry, is presented in this paper. The flow about a high-speed train has a multi-scale character which poses challenges for the design of computationally effective meshes. The purpose of this study is to assist i...

In the present work the propagating modes of detonation wave in supersonic hydrogen-air mixtures are investigated in narrow rectangular channels. To clarify the effect of the detonation wave interaction with the boundary layer on the evolution and propagation of detonation phenomenon, high-speed laser schlieren experiments and adaptive Navier-Stoke...

We present an adaptive parallel solver for the numerical simulation of ideal magnetohydrodynamics in two and three space dimensions. The discretisation uses a finite volume scheme based on a Cartesian mesh and an explicit compact Runge--Kutta scheme for time integration. Numerically, a generalized Lagrangian multiplier approach with a mixed hyperbo...