Assessment of scale resolving turbulence models in the TAU code for canonical shock-turbulence interaction

This report contains the detailed description of the study of the canonical shock-turbulence interaction (STI) problem performed with the DLR’s TAU CFD solver. STI studies reported in the literature are typically performed with high-order (> 2nd) accurate numerical schemes for space- and time discretizations. Instead, TAU, being a code used for both industrial and academic purposes, contains second-order accurate numerics. The motivation of this work is to understand how such a solver copes with the canonical STI setup which requires low dissipation to describe the turbulence accurately while higher dissipation is needed to avoid numerical issues in the shock capturing process. To this end, the scale-resolving capability of TAU has been carefully investigated for several STI’s where turbulence has been described with a Large Eddy Simulations (LES) method

Turbulence Chemistry Interaction via Eddy Dissipation Model for Scramjet Analysis and Design

This paper considers the Eddy Dissipation Model to address the combustion process inside scramjet engines designed to operate at high flight Mach numbers. The aim is to demonstrate the most appropriate use of the model for design purposes. To this end, two hydrogen-fueled experimental scramjet configurations with different fuel injection approaches are studied numerically. In the case of parallel fuel injection, it is demonstrated that relying on estimates of ignition delay from a one-dimensional kinetics program can greatly improve the use of the EDM. In the second case, the transverse injection of hydrogen resulted in an overall good agreement of the model with experimental pressure traces except in the vicinity of the injection location. Overall, the EDM appears to be a suitable tool for scramjet combustor design incorporating a parallel or transverse fuel injection mechanism

Turbulence Chemistry Interaction via Eddy Dissipation Model for Scramjet Analysis and Design

This paper considers the Eddy Dissipation Model to address the combustion process inside scramjet engines designed to operate at high flight Mach numbers. The aim is to demonstrate the most appropriate use of the model for design purposes. To this end, two hydrogen-fueled experimental scramjet configurations with different fuel injection approaches are studied numerically. In the case of parallel fuel injection, it is demonstrated that relying on estimates of ignition delay from a one-dimensional kinetics program can greatly improve the use of the EDM. In the second case, the transverse injection of hydrogen resulted in an overall good agreement of the model with experimental pressure traces except in the vicinity of the injection location. Overall, the EDM appears to be a suitable tool for scramjet combustor design incorporating a parallel or transverse fuel injection mechanism

Modeling Scramjet Supersonic Combustion Via Eddy Dissipation Model

Scramjet technology has gained considerable interest in multi-stage to orbit design concepts due to its reusability and high specific impulse at high-Mach regimes. The aim of the present work is to introduce Reynolds Averaged Navier-Stokes CFD calculations in the design phase of scramjet vehicles and increase the fidelity of engine performance assessment. The turbulence-chemistry interaction is described by the Eddy Dissipation Model (EDM) introduced by Magnussen and Hjertager, which assumes that turbulent motions and not chemistry is the main driver in the rate of combustion. The use of the EDM is explored by application to three hydrogen fueled scramjet test cases. The model requires constants to be prescribed, which have found to be case dependent. Optimal values for the cases simulated are discussed along with appropriateness of the model for general design simulations. The advantage in computational cost is demonstrated by comparison with a no-model finite-rate chemistry approach

Turbulence chemistry interaction via eddy dissipation model for scramjet analysis and design

This paper considers the Eddy Dissipation Model to address the combustion process inside scramjet engines designed to operate at high flight Mach numbers. The aim is to demonstrate the most appropriate use of the model for design purposes. To this end, two hydrogen-fueled experimental scramjet configurations with different fuel injection approaches are studied numerically. In the case of parallel fuel injection, it is demonstrated that relying on estimates of ignition delay from a one-dimensional kinetics program can greatly improve the use of the EDM. In the second case, the transverse injection of hydrogen resulted in an overall good agreement of the model with experimental pressure traces except in the vicinity of the injection location. Overall, the EDM appears to be a suitable tool for scramjet combustor design incorporating a parallel or transverse fuel injection mechanism

Scramjet combustion modeling using eddy dissipation model

In order to aid in the design of scramjet propulsion systems at high Mach number operation, this works considers the Eddy Dissipation Model (EDM) to describe the combustion process inside an open-access Computational Fluid Dynamics (CFD) solver. Typical CFD modeling approaches for turbulent supersonic reacting flows are associated with a high computational cost. This in turn inhibits the use of CFD in scramjet combustor design or in higher level preliminary designs such as the trajectory optimization process of a scramjet powered vehicle.;Instead, low-fidelity models are preferred to charaterize the propulsion system in the latter type of application. The EDM relies on simplified assumptions regarding the combustion process whose validity is thought to be prevalent at high Mach number scramjet operation. It is therefore a suitable candidate model in order to introduce more routinely CFD in scramjet preliminary design phases. As part of the present work, first steps include the selection of an open-source CFD solver followed by several validation studies.;After its implementation, a critical numerical analysis of the EDM is performed by considering three hydrogen-fueled experimental scramjet configurations with different fuel injection approaches. Its application is further investigated with a mainly kinetically controlled scramjet design where the underlying assumptions of the EDM are not valid anymore. Finally, the EDM is applied to a combustor design problem demonstrating the metrics of interest that can be relied on for this task.In order to aid in the design of scramjet propulsion systems at high Mach number operation, this works considers the Eddy Dissipation Model (EDM) to describe the combustion process inside an open-access Computational Fluid Dynamics (CFD) solver. Typical CFD modeling approaches for turbulent supersonic reacting flows are associated with a high computational cost. This in turn inhibits the use of CFD in scramjet combustor design or in higher level preliminary designs such as the trajectory optimization process of a scramjet powered vehicle.;Instead, low-fidelity models are preferred to charaterize the propulsion system in the latter type of application. The EDM relies on simplified assumptions regarding the combustion process whose validity is thought to be prevalent at high Mach number scramjet operation. It is therefore a suitable candidate model in order to introduce more routinely CFD in scramjet preliminary design phases. As part of the present work, first steps include the selection of an open-source CFD solver followed by several validation studies.;After its implementation, a critical numerical analysis of the EDM is performed by considering three hydrogen-fueled experimental scramjet configurations with different fuel injection approaches. Its application is further investigated with a mainly kinetically controlled scramjet design where the underlying assumptions of the EDM are not valid anymore. Finally, the EDM is applied to a combustor design problem demonstrating the metrics of interest that can be relied on for this task

Study of a supersonic reacting wall jet with a variable turbulent Prandtl and Schmidt number approach

Within the context of supersonic combustion modeling in air-breathing propulsion, the turbulent Prandtl and turbulent Schmidt numbers have a profound effect on the resulting predictions. This work considers a Scalar Fluctuation Model (SFM) introducing two extra transport equations in order to specify variable values for turbulent Prandtl and turbulent Schmidt numbers within a Reynolds-Averaged Navier-Stokes (RANS) framework relying on a gradient diffusion hypothesis for both the turbulent heat and mass flux. The SFM is applied in conjunction with a two-equation linear eddy viscosity model. In order to study the effect of the different modeling choices, the supersonic reacting wall jet experiment of Burrows and Kurkov [24] is considered. A strong effect of Turbulence Chemistry Interaction (TCI) through an assumed PDF approach on the SFM is observed and needs to be enabled in order for predictions to be within experimental observation bounds in terms of ignition delay. Overall, the presented SFM methodology could be a viable candidate for supersonic combustion studies

Turbulence chemistry interaction via eddy dissipation model for scramjet analysis and design

This paper considers the Eddy Dissipation Model to address the combustion process inside scramjet engines designed to operate at high flight Mach numbers. The aim is to demonstrate the most appropriate use of the model for design purposes. To this end, two hydrogen-fueled experimental scramjet configurations with different fuel injection approaches are studied numerically. In the case of parallel fuel injection, it is demonstrated that relying on estimates of ignition delay from a one-dimensional kinetics program can greatly improve the use of the EDM. In the second case, the transverse injection of hydrogen resulted in an overall good agreement of the model with experimental pressure traces except in the vicinity of the injection location. Overall, the EDM appears to be a suitable tool for scramjet combustor design incorporating a parallel or transverse fuel injection mechanism

The risk of COVID-19 death is much greater and age dependent with type I IFN autoantibodies

International audienceSignificance There is growing evidence that preexisting autoantibodies neutralizing type I interferons (IFNs) are strong determinants of life-threatening COVID-19 pneumonia. It is important to estimate their quantitative impact on COVID-19 mortality upon SARS-CoV-2 infection, by age and sex, as both the prevalence of these autoantibodies and the risk of COVID-19 death increase with age and are higher in men. Using an unvaccinated sample of 1,261 deceased patients and 34,159 individuals from the general population, we found that autoantibodies against type I IFNs strongly increased the SARS-CoV-2 infection fatality rate at all ages, in both men and women. Autoantibodies against type I IFNs are strong and common predictors of life-threatening COVID-19. Testing for these autoantibodies should be considered in the general population