The cumulant lattice Boltzmann method (LBM) has been recently used to simulate multiphase-multicomponent flows by applying an external force. Furthermore, the mass and momentum are not conserved when an external force is used. In the classical approach, the third-order derivatives in density necessitate information from a large stencil of neighbors, which affects parallelization and is computationally expensive. In this paper, we propose an equilibrium distribution function in the moment space, which includes diagonal and off diagonal elements of the pressure tensor. Consequently, the interfacial tension effect can be exerted into this equilibrium function, circumventing the need for an external force. The Cahn–Hilliard equation can be coupled to the method to track the interface at multiphase-multicomponent flows. This function is applied on the moment, central, and cumulant LBM and transferred back to the discrete space to be used in Bhatnagar–Gross–Krook LBM. These key advantages include simplicity, easy-to-implement, and high parallelization capability due to removing high-order derivatives. An immiscible two-component flow between two parallel plates is simulated and compared with the analytical solution at different viscosities for the moment LBM and the cumulant LBM. Numerical results are in good agreement with analytical solutions. Moreover, a dispersed droplet in a continuous phase under shear flow is simulated to show the capability of the proposed method in the breaking-up process modeling. It is demonstrated that spurious velocities are less affected by decreasing the viscosity and cumulant LBM with the proposed function, while the interfacial tension is calculated accurately. Finally, the method has been extended for three dimensions, and two cases of a three-dimensional breakup of a liquid thread and collision of two equal droplets are studied to show the ability of this method to simulate the coalescence and breakup process.

The strategic European paper “Flightpath 2050” claims dramatic reductions of noise for aviation transport scenarios in 2050: “...The perceived noise emission of flying aircraft is reduced by 65%. These are relative to the capabilities of typical new aircraft in 2000...”. There is a consensus among experts that these far reaching objectives cannot be accomplished by application of noise reduction technologies at the level of aircraft components only. Comparably drastic claims simultaneously expressed in Flightpath 2050 for carbon dioxide and NOX reduction underline the need for step changes in aircraft technologies and aircraft configurations. New aircraft concepts with entirely different propulsion concepts will emerge, including unconventional power supplies from renewable energy sources, ranging from electric over hybrid to synthetic fuels. Given this foreseen revolution in aircraft technology the question arises, how the noise impact of these new aircraft may be assessed. Within the present contribution, a multi-level, multi-fidelity approach is proposed which enables aircraft noise assessment. It is composed by coupling noise prediction methods at three different levels of detail. On the first level, high fidelity methods for predicting the aeroacoustic behavior of aircraft components (and installations) are required since in the early stages of the development of innovative noise reduction technology test data is not available. The results are transferred to the second level, where radiation patterns of entire conventional and future aircraft concepts are assembled and noise emissions for single aircraft are computed. In the third level, large scale scenarios with many aircraft are considered to accurately predict the noise exposure for receivers on the ground. It is shown that reasonable predictions of the ground noise exposure level may be obtained. Furthermore, even though simplifications and omissions are introduced, it is shown that the method is capable of transferring all relevant physical aspects through the levels.

A detailed numerical study of turbulent flow through a micro-orifice is presented in this work. The flow becomes turbulent due to the orifice at the considered Reynolds numbers (∼ ${10}^4$ ). The obtained flow rates are in good agreement with the experimental measurements. The discharge coefficient and the pressure loss are presented for two input pressures. The laminar stress and the generated turbulent stresses are investigated in detail, and the location of the vena contracta is quantitatively reproduced.

Surfactants play a critical role in the physics of paint and coating formulations, affecting key rheological properties such as viscosity, yield stress, and thixotropy. This paper proposes a new three-dimensional phase-field model that uses the cumulant lattice Boltzmann method (LBM) to simulate soluble surfactants. Although current phase-field models commonly use Langmuir's relationship, they cannot calculate interfacial tension analytically, or the LBM models used are unstable when viscosities are low. However, the proposed method overcomes these limitations through two main features. First, the main parameters for modeling and controlling the surfactant's strength and interaction with other phases are directly obtained from a given initial interfacial tension and bulk surfactant, eliminating the need for trial-and-error simulations. Second, a new equilibrium distribution function in the moment space that includes diagonal and off diagonal elements of the pressure tensor is used to minimize Galilean invariance violation. Additionally, there is no need to use an external force to recover multiphase flows, which could break mass conservation. Furthermore, this method has significant potential for parallelization since only one neighbor's cell is used for discretization. The method shows Langmuir relation behavior and is validated with analytical solutions for various interfacial tensions and surfactant concentrations. Moreover, the paper demonstrates the influence of interfacial tension and surfactants on spurious velocities, indicating the method's stability at low viscosities. The dynamics of droplets in the presence of the surfactants is studied in spinodal decomposition and under various external forces. The method accurately simulates the breaking-up and coalescence for these cases. Furthermore, the method successfully simulates the breakage of a liquid thread at a high viscosity ratio.