Ralf Deiterding

University of Southampton · Aeronautics/Astronautics

A second-order-accurate finite volume method, hybridized by blending an extended double-flux algorithm and a traditionally conservative scheme, is developed. In this scheme, hybrid convective fluxes as well as hybrid interpolation techniques are designed to ensure stability and accuracy in the presence of both material interfaces and shocks. Two co...

The reactive Navier-Stokes equations with adaptive mesh refinement and a detailed chemical reactive mechanism (11 species, 27 steps) were adopted to investigate a detonation engine considering the injection and supersonic mixing processes. Flame acceleration and deflagration-to-detonation transition (DDT) in a premixed/inhomogeneous supersonic hydr...

This work presents a new implementation of compressible magnetohydrodynamic (MHD) models in the context of the generalised Lagrange multiplier (GLM), combined with source term techniques to retain entropy stability, necessary for thermodynamic consistency. The GLM techniques introduce a scalar field, that is evolved along the MHD quantities, in ord...

The unsteady, reactive Navier-Stokes equations with a detailed chemical mechanism of 11 species and 27 steps were employed to simulate the mixing, flame acceleration and deflagration to detonation transition (DDT) triggered by transverse jet obstacles. Results show that multiple transverse jet obstacles ejecting into the chamber can be used to acti...

An unconventional method of flame acceleration propagating upstream in subsonic and supersonic mixtures is proposed to obtain a rapid onset of detonation. The Navier-Stokes equations with adaptive mesh refinement and a detailed hydrogen-air chemistry reaction mechanism of 11 species and 27 steps are employed to simulate the whole flame propagation...

In this study, detonation initiation in supersonic premixed flow is experimentally investigated using hot jets with different strength. Two types of shock interaction models, B/S (bow/separated) and S/S (separated/separated), are observed, respectively. In the case with the high-strength hot jet, the ignition of the combustible mixture is triggered...

Two-dimensional simulations were carried out to investigate the flame acceleration and deflagration-to-detonation transition (DDT) in a combustion chamber filled with a subsonic or supersonic mixture by employing Navier-Stokes equations together with a detailed chemistry reaction mechanism of 11 species and 27 steps under adaptive mesh refinement....

In detonation engines and accidental explosions, a detonation may propagate in an inhomogeneous mixture with non-uniform reactant concentration. In this study, one- and two-dimensional simulations are conducted for detonation propagation in hydrogen/oxygen/nitrogen mixtures with periodic sinusoidal or square wave distribution of the reactant concen...

In explosion accidents, inert layer(s) can be used to dampen or suppress detonation propagation. In detonation engines, the detonation may propagate in an inhomogeneous mixture with inert layer(s). Here, the detonation propagation in hydrogen/oxygen/nitrogen mixtures with a single inert layer normal to the detonation propagation direction was inves...

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 paper describes numerically the rapid deflagration-to-detonation transition (DDT) in detail in a high-frequency pulse detonation rocket engine (PDRE). Different from traditional DDT, reactants are injected into the chamber from near the open end and travel toward the closed end. Previous experiments have implied that the gas-dynamic shock by i...

A combination of solid and transverse jet obstacles is proposed to trigger flame acceleration and deflagration-to-detonation transition (DDT). A numerical study of this approach is performed by solving the reactive Navier-Stokes equations deploying an adaptive mesh refinement technique. A detailed hydrogen-air reaction mechanism with 12 species and...

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 separate detonation heads, depending on mass flow rate. Spectrograms...

The extreme conditions experienced in hypersonic flight can be difficult to reproduce in ground test facilities. As such, the use of computational simulations is vital in the design of Thermal Protection Systems (TPSs) for hypersonic vehicles. Many TPSs use materials that ablate and this leads to changes in shape of the body with time. As such, the...

Numerical simulations of hypersonic viscous flow in thermochemical non-equilibrium over a double wedge with high Mach and high enthalpy inflow conditions are performed to investigate shock pattern transition. First, simulations for varying second wedge angle are conducted in order to classify the shock patterns. Then, the effects of the thermochemi...

A novel mesh refinement sensor is proposed for lattice Boltzmann methods (LBMs) applicable to either static or dynamic mesh refinement algorithms. The sensor exploits the kinetic nature of LBMs by evaluating the departure of distribution functions from their local equilibrium state. This sensor is first compared, in a qualitative manner, to three s...

The rotating detonation engine is a promising realization of pressure gain combustion for propulsion and power generation systems. A rotating detonation engine running on ethylene-oxygen is simulated by using AMROC with a second-order accurate finite volume method and approximate Riemann solvers. Multi-step chemical kinetic mechanisms are employed...

We present the inner workings of our self-developed dynamically adaptive lattice Boltzmann software AMROC-LBM and apply the code to large eddy simulations that investigate the thickening and perturbance of turbulent boundary layers over rough and permeable surfaces. Besides the fluid mechanical results, the computational performance on large-scale...

During the simulations of the magnetohydrodynamic equations, numerical errors might cause the formation of non-physical divergence components in the magnetic field. This divergence compromises the stability and accuracy of the simulations. In order to overcome this problem, several methodologies, called divergence cleaning methods, are proposed. Be...

In this report, Direct Numerical Simulation (DNS) of compressible flow over a set of smooth and rough surfaces is carried out in a turbulent channel flow configuration. The aim is to quantify the Hama roughness function for different rough wall geometries under the effects of compressibility as well as to obtain an estimate for the overall surface...

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...

Lattice Boltzmann schemes are known for their efficiency and low dissipation properties. However, the standard lattice Boltzmann method (LBM) is limited to Cartesian grids, and this approach can be troublesome when approximating thermal flows over curved walls. The present work proposes to solve the two-dimensional lattice Boltzmann equation under...

AMR-LBM-LES simulations are carried out using our in-house parallel software AMROC. It is first successfully used to calculate the aeroacoustic of a 3D airfoil with wall-resolved simulations. To extend the capability of the software, the implementation of an existing wall model is then validated for a 2D airfoil.

Many Thermal Protection Systems (TPS) for hypersonic vehicles use ablating materials. In turn, this causes the vehicles' external geometry to change during flight. In this work a strand/Cartesian Adaptive Mesh Refinement solver has been used to simulate the hypersonic flow over recessing surfaces. This technique uses separate near-body and off-body...

A generic solver in a parallel Cartesian adaptive mesh refinement framework is extended to simulate reactive flows on structured curvilinear meshes. A second-order accurate finite volume method is used with a grid-aligned Riemann solver for inviscid thermally perfect gas mixtures. Detailed, multi-step chemical kinetic mechanisms are employed with a...

In this study, Direct Numerical Simulation (DNS) of compressible flow over a set of smooth and rough surfaces is carried out in a turbulent channel flow configuration. The aim is to quantify the Hamas roughness function for different rough wall geometries under the effects of compressibility. For this study, a flow with bulk Reynolds number 6000 an...

Transpiration-based cooling using porous layer is explored where the coolant is injected into the hypersonic cross-flow, providing a more uniform distribution of the coolant. Three-dimensional direct numerical simulations of flow past a at plate with a porous layer are conducted at M = 5. Conjugate heat flux boundary condition is used as compared t...

In shock tube experiments, the interaction between the reflected shock and boundary layer can induce shock bifurcation and weak ignition. The weak ignition can greatly affect the ignition delay time measurement in a shock tube experiment. In this work, two-dimensional simulations considering detailed chemistry and transport are conducted to investi...

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...

In shock tube experiments, the interaction between the reflected shock and boundary layer can induce shock bifurcation and weak ignition. The weak ignition can greatly affect the ignition delay time measurement in a shock tube experiment. In this work, two-dimensional simulations considering detailed chemistry and transport are conducted to investi...

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...

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...