@article{Adhikari2022,author={Adhikari, Nirajan and Alexeenko, Alina},doi={10.2514/1.T6271},journal={Journal of Thermophysics and Heat Transfer},month=jan,number={1},pages={118--128},title={{Development and Verification of Nonequilibrium Reacting Airflow Modeling in ANSYS Fluent}},volume={36},year={2022},}
2021
PoF
A general form of Macheret–Fridman classical impulsive dissociation model for nonequilibrium flows
The rate of dissociation behind a strong shock in thermochemical nonequilibrium depends on the vibrational excitation of the molecules, hence the rates become a function of translational-rotational and vibrational temperatures. The Macheret–Fridman (MF) model provides analytical expressions for nonequilibrium dissociation rates assuming the collision of molecules to be in the impulsive limit. However, the original form of the model was limited to the dissociation of homonuclear molecules. In this work, we present a general form of the Macheret–Fridman classical impulsive model by considering the dissociation of a heteronuclear molecule and present macroscopic rates applicable for modeling dissociation in computational fluid dynamics (CFD). The nonequilibrium dissociation rates from the MF-CFD model compared well with the available quasiclassical trajectory (QCT) data for some important reactions in the air. Additionally, we also present a comparison of the average vibrational energy removed in a dissociation reaction predicted by the MF-CFD model with QCT data for several reactions in air and propose some improvements to the model. The developed MF-CFD model was used to investigate various nonequilibrium flow problems and the results were compared with available experimental data. In general, the results from the MF-CFD model are promising and the model shows a possibility of becoming the standard tool for investigating nonequilibrium flows in CFD.
@article{Adhikari2021,author={Adhikari, N. and Alexeenko, A. A.},doi={10.1063/5.0047341},journal={Physics of Fluids},month=may,number={5},pages={056109},publisher={AIP Publishing LLC},title={{A general form of Macheret–Fridman classical impulsive dissociation model for nonequilibrium flows}},volume={33},year={2021},}
2020
AIAA
Modeling Nonequilibrium Aerothermochemistry in a General Purpose CFD Solver
@inproceedings{Adhikari2020,address={Montreal, Canada},author={Adhikari, Nirajan and Alexeenko, Alina},booktitle={23rd AIAA International Space Planes and Hypersonic Systems and Technologies Conference},doi={10.2514/6.2020-2408},month=mar,number={AIAA 2020-2408},pages={1--12},publisher={American Institute of Aeronautics and Astronautics,},title={{Modeling Nonequilibrium Aerothermochemistry in a General Purpose CFD Solver}},year={2020},}
JPharmSci
Sensitivity Study to Assess the Robustness of Primary Drying Process in Pharmaceutical Lyophilization
The objective of this work is to apply a sensitivity study to assess the robustness of the primary drying step of pharmaceutical lyophilization with respect to deviations in process parameters. The sensitivity study can provide valuable information regarding the effect of process input parameters on the product quality that can aid in designing robust lyophilization processes. In this study, the output response is related to its inputs using Smolyak sparse grid generalized polynomial chaos method, and the sensitivity was calculated using elementary effects method. Sensitivity of chamber pressure and shelf temperature on product temperature of 2 sucrose-based and one mannitol-based formulation was studied, and the results were analyzed in terms of risk of adverse effects due to process deviations on the product quality. The study revealed that the sensitivity varies among formulations, and preliminary information regarding the possible impact of process deviations can be obtained from the process cycle diagram. The product temperature showed greater sensitivity toward the change in the shelf temperature than toward change in the chamber pressure for the greater part of the primary drying stage. An aggressive process-deviation scenario at the late stage of primary drying was also studied for different formulations, and the results were consistent with the sensitivity study.
@article{ADHIKARI20201043,title={Sensitivity Study to Assess the Robustness of Primary Drying Process in Pharmaceutical Lyophilization},journal={Journal of Pharmaceutical Sciences},volume={109},number={2},pages={1043-1049},year={2020},issn={0022-3549},doi={10.1016/j.xphs.2019.10.012},author={Adhikari, Nirajan and Zhu, Tong and Jameel, Feroz and Tharp, Ted and Shang, Sherwin and Alexeenko, Alina},keywords={lyophilization, freeze-drying, mechanistic modeling, mathematical models, quality by design, uncertainty quantification, sensitivity, process deviation, excursion study, product robustness}}
2018
Springer
Grid Generation About High-Lift Wing Configurations
The current guidelines provided by the 3rd AIAA CFD High Lift Prediction Workshop for building unstructured meshes representing high-lift wing configurations are demonstrated and discussed. Specifically, Pointwise grid generation software is used to generate general multi-element unstructured grids about the NASA High Lift Common Research Model and the Japanese Aerospace Exploration Agency Standard Model with and without nacelles and pylons. Several modifications to the guidelines that enhance grid quality are presented. Additionally, the user-defined parameters within Pointwise that govern the mesh generation process are reviewed in detail.
@inbook{Adhikari2018,author={Adhikari, Nirajan and Nichols, D. Stephen},editor={L{\'o}pez Mejia, Omar Dar{\'i}o and Escobar Gomez, Jaime A.},title={Grid Generation About High-Lift Wing Configurations},booktitle={Numerical Simulation of the Aerodynamics of High-Lift Configurations},year={2018},publisher={Springer International Publishing},address={Cham},pages={9--26},isbn={978-3-319-62136-4},doi={10.1007/978-3-319-62136-4_2},}
Springer
Incompressible Solutions About High-Lift Wing Configurations
Accurately predicting the performance of high-lift wing configurations with Computational Fluid Dynamics is an active area of research for academia and industry alike. The compressible Navier–Stokes equations are usually used in these studies to predict the complex flow field generated by high lift wing configurations. However, since these configurations are applied in low-speed conditions where }}Mach \backslashle 0.2}}, the compressible equations can exhibit some numerical stiffness caused by the quasi-incompressible nature of air under these conditions. Instead of using preconditioned compressible equations to alleviate these numerical issues, this work proposes the use of the incompressible Navier–Stokes equations to predict these flow fields. Specifically, the incompressible solutions about the Japanese Aerospace Exploration Agency Standard Model configuration with and without nacelles and pylons are compared with experiment at multiple angles of attack to demonstrate the effectiveness of this approach.
@inbook{Adhikari2018b,author={Adhikari, Nirajan and Nichols, D. Stephen},editor={L{\'o}pez Mejia, Omar Dar{\'i}o and Escobar Gomez, Jaime A.},title={Incompressible Solutions About High-Lift Wing Configurations},booktitle={Numerical Simulation of the Aerodynamics of High-Lift Configurations},year={2018},publisher={Springer International Publishing},address={Cham},pages={27--43},isbn={978-3-319-62136-4},doi={10.1007/978-3-319-62136-4_3},}