The paper studies the dissociation and combustion of a layer of methane hydrate powder at a forced air flow over the upper surface of the layer (the air velocity is directed parallel to the upper surface of the layer). The influence of the layer thickness and air velocity on the combustion of gas hydrate is investigated. The calculated curves for the effect of the heat transfer coefficient, external

The vast majority of research works on low aspect ratio rotating wings report that, at high angle of attack, the leading edge vortex that forms on the upper surface of the wing is stable. This ‘trick’ is used by insects and auto-rotating seeds, for example, to achieve the desirable amount of lift. Yet, a few experimental studies suggest that leading edge vortices might be unstable under similar, low

Data-driven turbulence modelling is becoming common practice in the field of fluid mechanics. Complex machine learning methods are applied to large high fidelity data sets in an attempt to discover relationships between mean flow features and turbulence model parameters. However, a clear discrepancy is emerging between complex models that appear to fit the high fidelity data well a priori and simpler

The effects of buoyancy on turbulent premixed flames are expected to be strong due to the large changes in density between the unburned and fully burned gases. The present work utilises three-dimensional direct numerical simulations of statistically planar turbulent premixed flames under decaying turbulence to study the influence of buoyancy on the evolution of turbulent kinetic energy within the flame

This paper provides a numerical study on n-dodecane flames using Large-Eddy Simulations (LES) along with the Flamelet Generated Manifold (FGM) method for combustion modeling. The computational setup follows the Engine Combustion Network Spray A operating condition, which consists of a single-hole spray injection into a constant volume vessel. Herein we propose a novel approach for the coupling of the

A model to predict soot evolution during the combustion of complex fuels is presented. On one hand, gas phase, \(\hbox {polycyclic aromatic hydrocarbon (PAH)}\) and soot chemistry are kept large enough to cover all relevant processes in aero engines. On the other hand, the mechanisms are reduced as far as possible, to enable complex computational fluid dynamics (CFD) combustion simulations. This is

In free-field operation, many aerodynamic systems are confronted with changing turbulent inflow conditions. Wind turbines are a prominent example. Here, the rotation of the rotor blades causes incoming wind gusts to result in a local change in the angle of incidence for the blade segments, which changes the effective angle of attack and can lead to dynamic non-linear effects like dynamic stall. Dynamic

The flame pocket formation, including reactant pocket, product pocket, soot pocket, and fluid parcel, is a common phenomenon in turbulent combustion occurred as a response of the flame to flow straining and shearing. Understanding pocket behavior is vital to study the flames in such a regime. This work addresses the research need to experimentally measure and track multiple flame pockets in 3D. For

Prediction of differential molecular diffusion remains a great challenge for flamelet modeling of turbulent non-premixed combustion. This work addresses this challenge through a priori and a posteriori testing of flamelet models by using DNS databases to enable a detailed examination of the model capability and limitation for the prediction of differential molecular diffusion under different combustion

Scalar forcing in the context of turbulent stratified flame simulations aims to maintain the fuel-air inhomogeneity in the unburned gas. With scalar forcing, stratified flame simulations have the potential to reach a statistically stationary state with a prescribed mixture fraction distribution and root-mean-square value in the unburned gas, irrespective of the turbulence intensity. The applicability

The unsteady effects of buoyancy-induced instabilities on jet diffusion flames are investigated experimentally under normal gravity conditions. Methane and propane are used as test fuels that are lighter and heavier than ambient air, respectively. A similar Froude (Fr) and Reynolds (Re) number relationship is realized in both hydrocarbon fuels with different tube diameters ranging from 6 to 24.2 mm

The effects of varying turbulence intensity and turbulence length scale on premixed turbulent flame propagation are investigated using Direct Numerical Simulation (DNS). The DNS dataset contains the results of a set of turbulent flame simulations based on separate and systematic changes in either turbulence intensity or turbulence integral length scale while keeping all other parameters constant. All

This paper presents an experimental study on dynamic response of a forced low-swirl methane/air premixed flame with external acoustic excitation over a wide range of driving frequency. Global flame response in terms of gain and phase delay between flame intensity and incoming velocity perturbation is determined. Local flame response is investigated in detail at three typical frequencies: 55 Hz, 105 Hz

The physical mechanism leading to flame local extinction remains a key issue to be further understood. An analysis of large eddy simulation (LES) data with presumed probability density function (PDF) based closure (Chen et al., 2020, Combust. Flame, vol. 212, pp. 415) indicated the presence of localised breaks of the flame front along the stoichiometric line. These observations and their relation to

In this paper, a simple method to locally compute the model coefficient \(C_{DES}\) in Reddy et al. (Int J Heat Fluid Flow 50:103–113, 2014. https://doi.org/10.1016/j.ijheatfluidflow.2014.06.002) is presented. The formula for the coefficient is derived from the structural function \(B_{\beta }\) of Vreman (Phys Fluids 16(10):3670–3681, 2004. https://doi.org/10.1063/1.1785131). It, therefore, does not

The mean and instantaneous flow separation of two different three-dimensional asymmetric diffusers is analysed using the data of large-eddy simulations. The geometry of both diffusers under investigation is based on the experimental configuration of Cherry et al. (Int J Heat Fluid Flow 29(3):803–811, 2008). The two diffusers feature similar area ratios of \(\mathrm{AR}=4.8\) and \(\mathrm{AR}=4.5\)

The underlying mechanisms of three different flow-control strategies on drag reduction in a channel flow are investigated by direct numerical simulations at friction Reynolds numbers ranging from 65 to 85. These strategies include the addition of long-chain polymers, the incorporation of slip surfaces, and the application of an external body force. While it has been believed that such methods lead

The hydrodynamic instability characteristics of non-adiabatic N2-diluted n-butane/air flames generated on McKenna burner were investigated experimentally under atmosphere pressure. In order to capture the quantitative structure of cellular flames, planar laser induced fluorescence technology (OH-PLIF and CH2O-PLIF) was employed, as well as the chemiluminescence imaging was used to record flame morphology

An experiment-based closure framework for turbulent combustion modeling is further validated using the Sydney piloted turbulent partially premixed flames with inhomogeneous inlets. The flames are characterized by the presence of mixed mode combustion. The framework’s closure is “trained” on multi-scalar measurements to construct thermo-chemical scalar statistics parameterized in terms of principal

To understanding the initiating process in the pulse detonation curved-chamber and rotating detonation chamber, this article conducted an experimental study on the flame acceleration and the transition to detonation in the annular channel. With different equivalence ratios of acetylene-air and acetylene-oxygen as explosive mixtures, based on high-speed photography and shadow technology, the propagation

Hybrid RANS-LES methods are supposed to provide major contributions, in particular regarding the analysis and prediction of wall-bounded turbulent flows at high Reynolds numbers. Validation data are often unavailable under these conditions, this means we need reliable hybrid RANS-LES having a proven predictive power. The latter depends on the theoretical foundations of these methods. Inspired by a

A noise source characteristic of an unheated compressible jet is experimentally investigated for the jet with exit Mach number 0.8. Measurements of acoustic pressure fluctuations were performed in the near-field and far-field independently to identify noise source characteristics using the correlation technique. Near-field and far-field acoustic pressure fluctuations were also measured simultaneously

The exact placement of the laminar–turbulent transition has a significant effect on relevant characteristics of the boundary layer and aerodynamics, such as drag, heat transfer and flow separation on e.g. wings and turbine blades. Tripping, which fixes the transition position, has been a valuable aid to wind-tunnel testing during the past 70 years, because it makes the transition independent of the

Combustion simulations with high fidelity turbulence models and detailed chemistry may suffer from high computational power requirements due to the combined cost of time-scale dissipation and small integration steps. Such a limitation can be avoided by employing a hybrid reaction mechanism reduction method called local self-similarity tabulation (LS2T). LS2T directly solves several dominant species

A transitional hybrid RANS–LES model is devised to replicate the flow around a cyclist mannequin which is positioned at the high-drag position. The transitional model of Cakmakcioglu et al. (Proc Inst Mech Eng C J Mech Eng Sci 232(21):3915–3929, 2018) which is a modified Spalart–Allmaras model, is used to simulate the transitional flow with a coarse grid close to the solid walls, while the flow is