Vol. 11, No. 3 (2023): Regular Issue

The gas-kinetic unified algorithm solving the Boltzmann modeling velocity distribution function equation is developed and employed to study gas dynamic problems covering various flow regimes. Based on the computable modeling of Boltzmann equation, the modeled velocity distribution function equation covering to various flow regimes is presented. The discrete velocity ordinate method is developed and applied to remove the velocity space dependency of the distribution function. Based on the uncoupling technique on molecular movement and collision in the DSMC method, the gas-kinetic finite difference scheme is constructed to directly solve the discrete velocity distribution functions by using the unsteady time-splitting method from computational fluid dynamics. The discrete velocity numerical integration method with the Gauss-type weight function is developed to evaluate the macroscopic flow variables at each point in the physical space. The parallel implementation for the gas-kinetic numerical method is investigated to solve the three-dimensional complex flows. To validate the accuracy and feasibility of the present numerical method, one-dimensional shock wave problems, supersonic flows past two-dimensional circular cylinder and three-dimensional hypersonic flows past sphere and spacecraft shape covering various flow regimes are simulated with different Knudsen numbers and Mach numbers. The computational results are found in good agreement with the related theoretical, DSMC, N-S, and experimental data. The computing practice has confirmed that the present gas-kinetic algorithm probably provides a promising approach to resolve the hypersonic aerothermodynamics problems with the complete spectrum of flow regimes from the gas-kinetic point of view of solving the unified Boltzmann model equation.

A numerical method has been established and applied to compute the chemical non-equilibrium flow involving ablative chemical reaction and flow interference effect in near space, where the chemical non-equilibrium Navier-Stokes equation is solved by taking account of 23 species including the ablative products. The computational results of electron number density in plasma sheath for sphere-cone RAMC(Radio Attenuation Measurement C plan)-II are well compared with those of flight experiments. The reliability of the present method has been validated, and the varying feature of the electron number density with flight altitude has been revealed. The present numerical method is applied to compute the Teflon ablative flow field and flow interference in near space past sphere-cone body with different altitudes. It is indicated that the effect of ablative products on electron number density is mainly limited in the region of boundary layer while the phenomena of Teflon ablation are obvious at moderate and low altitudes. The decrease of temperature in the boundary layer is caused by the Teflon ablation which results in the increase of the number of negative ions. On the other hand, the number of chemical species F- increases continuously with the decrease of flight altitude resulted from the reaction between electron and electrophilic species of Teflon-air reactive mixtures. These factors cause the reduction of electron number density in the boundary layer, specially flow interference and characteristics around the wreckages generated by multiple disintegration of the Tiangong-type vehicle in expiration of service during off-orbit reentry.

In order to precisely simulate the thermodynamic nonequilibrium feature in hypervelocity streaming and plume expansion flows, the discrete energy transfer procedure considering quantum effect in direct simulation Monte Carlo method is presented. The formulas of rotational energy for non-rigid rotator model and vibrational energy for anharmonic oscillator model on diatomic molecules are given. The calculation of quantum energy levels at equilibrium distribution is described. The energy transfer models of rotation-translation and vibration-translation as well as their implementation are derived. Two dimensional hypersonic flow around a cylinder of Nitrogen with different flight speeds is computed and analyzed. The comparison of the thermodynamic nonequilibrium process between continuous and discrete energy modes indicate the necessity of energy transfer model considering quantum effect for precise simulation of the thermodynamic nonequilibrium feature in high temperature flow field. The simulation of vacuum plume expansion also demonstrates the significant quantum effect of rotation mode.

A hybrid N-S/DSMC method is presented and applied to solve the three-dimensional hypersonic transitional flows by employing the MPC (modular Particle-Continuum) technique based on the N-S and the DSMC method. A sub-relax technique is adopted to deal with information transferring between the N-S and the DSMC. The hypersonic flows around a plate and a blunt cone under different Kn numbers are simulated by using the hybrid N-S/DSMC method. The present computations are found in good agreement with other experimental results. The present method provides an efficient way to predict the hypersonic aerodynamics in near-continuum transitional flow regime.

Depending upon Lotka-Volterra model along with biological parameters, intuitionistic fuzzy in nature, this paper deals with harvesting system of prey species and predator species. Our aim is to analyze the prey-predator model whose numerical values are imprecise in nature. To get rid of the vagueness, we use the concept of triangular intuitionstic fuzzy numbers. We first develop the crisp model under some important assumptions. Then the crisp model is transformed into intuitionistic fuzzy model by using the concept of Hukuhara derivative and then it is crispified with the help of Yager's Ranking method. We investigate existence of the equilibrium points of above mentioned crispified system and the condition of the local stability of those points is obtained by analyzing the eigen values of the variational matrix. Then the condition of global stability is described by using suitable Lyapunov function. The economic aspects along with the harvesting policies at optimal stage are described. The existence of the limit cycle of the fuzzy prey-predator model is analyzed by using Bendixon-Dulac-test. Furthermore, numerical simulations are presented in tabular form and graphical form to support the theoretical results.

In this paper, a new aircraft icing prediction scheme is proposed to obtain the aircraft icing shape from common meteorological parameter. Machine learning modeling is used to establish the mapping between meteorological parameters and in-cloud microphysical parameters based on a random forest algorithm. The outputs of machine learning model, median volume diameter (MVD) and liquid water content (LWC), are utilized as input parameters to simulate ice accretion for a specific airfoil, and the final icing shape is determined. The present work shows that in-cloud microphysical parameters might have some relationship with common meteorological parameters, and random forest showsbetter performance in prediction of in-cloud microphysical parameters. The research work has brought about a quantitative prediction scheme of aircraft icing that shows high engineering practical value in route planning, aviation meteorological warning and airworthiness certification, etc.

This paper calculated the water footprint (WF) of chilled chicken meat processing under alternative scenarios, including the contribution analysis to the Sustainable Development Goals (SDG). Volumetric WF was calculated according to the WF Network approach. The contribution of the system to the SDGs was analyzed using a qualitative screening approach. The results showed a WF of 136.1 liters for processing 1 kg of chilled chicken meat, with 0.7 liters from blue water and 135.4 liters from grey water. The wastewater treatment processes accounted for 99.5% of the total WF. According to scenarios analysis, to reduce the total WF of chilled chicken, it is necessary to invest in wastewater treatment technologies. The SDG analysis revealed potential positive contributions of the system to SDGs 2, 3, 6, 12, and 14 if the improvement scenarios are put in practice. The WF-SDG analysis was beneficial to evaluate the role of chicken meat processing in the search for SDGs, and to evaluate how the improvement opportunities can influence the system's relationship to the SDG. The methodology for connecting the SDGs to environmental metrics can be replicated for any type organizations, enabling the integration of the SDGs in production chains. Connecting environmental metrics to the SDGs can indicate directions for production systems seeking sustainability improvements. Thus, it becomes beneficial for society's search for 17 SDGs. There are few studies concerning WF and the SDGs, especially regarding industrialized products. Thus, this paper can contribute to this gap.