http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Raj, L. Prince,Singh, S.,Karchani, A.,Myong, R.S. Elsevier 2017 Computers & fluids Vol.157 No.-
<P><B>Abstract</B></P> <P>Super-parallel performance of a mixed explicit discontinuous Galerkin method is reported for the second-order Boltzmann-based nonlinear coupled constitutive models of rarefied and microscale gases. One of the challenging issues in the discontinuous Galerkin (DG) method is the higher computational cost compared with the traditional finite volume method (FVM) for a given set of grids. In the present study, we focus on the computational cost of a mixed modal explicit DG method for solving the conservation laws in conjunction with the first- and second-order Boltzmann-based constitutive models, in particular, in the context of parallelization of the implicit algebraic constitutive equations of rarefied and microscale gases in continuum and transition regimes. The computational cost of the Navier-Stokes-Fourier (NSF) and nonlinear coupled constitutive relation (NCCR) solvers is investigated in the serial and parallel frameworks. It was shown that the computational cost of the NCCR solver behaves nonlinearly with respect to the number of elements, due to the dependence of the number of iterations of the NCCR solver on the flow structure and the degree of thermal non-equilibrium. Such nonlinear dependence was clearly demonstrated from numerical solutions of three representative flows; flat plate, cylinder, and wedge. Ultimately, this nonlinear behavior of computational cost associated with nonlinear performance of the DG-NCCR solver resulted in an unexpected super-parallel performance in parallel processing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A super-parallel DG solver for the second-order constitutive models of rarefied and microscale gases is developed. </LI> <LI> Parallel implementation of a mixed DG method is achieved for triangular meshes. </LI> <LI> Computational cost of the serial and parallel solvers is investigated for various rarefied and microscale conditions. </LI> <LI> Super-parallel performance of the second-order algebraic NCCR model is reported for the first time. </LI> </UL> </P>
Ice accretion and aerodynamic effects on a multi-element airfoil under SLD icing conditions
Prince Raj, L.,Lee, J.W.,Myong, R.S. Elsevier 2019 AEROSPACE SCIENCE AND TECHNOLOGY Vol.85 No.-
<P><B>Abstract</B></P> <P>The impingement behavior of large water droplets, their interactions with the solid wall and the subsequent ice accretion and aerodynamic effects have become a key issue in in-flight aircraft icing. In this study, ice accretion and aerodynamic effects on a multi-element airfoil were investigated under the recently introduced Appendix O icing envelope. Supercooled large droplet (SLD) dynamics were taken into account by employing a unified computational approach. Ice accretion was simulated using a partial differential equation (PDE) based solver, instead of the commonly used control volume method. The numerical solver of the SLD impingement was built on the droplet deformation and droplet–wall interaction splash models. The unified solvers for clean air, large droplet impingement, ice accretion, and the aerodynamic analysis of ice effects—all of which are based on a single unstructured upwind finite volume framework—were first validated using available experimental data and then applied to investigate ice accretion and the resulting aerodynamic effects on multi-element airfoils for various flight conditions and, in particular, near-freezing SLD icing conditions. Interestingly, two counter-intuitive results were found when comparing the ice accretion and associated aerodynamic degradation for non-SLD and SLD cases. Moreover, considering runback ice was shown to be essential in the design of an ice protection system (IPS) for the multi-element wing.</P>
L. Prince Raj,E. Esmaeilifar,B. Sengupta,H. Jeong,R. S. Myong 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.4
The aircraft industry often uses computational methods to quantify ice accretion, investigate aerodynamic penalties, and conduct certification processes. The computational simulation of aircraft icing is computationally intensive owing to three consecutive runs of air, droplet, and ice accretion solvers. This study developed a parallel code using MPI and Coarray methods to reduce the computation time of an FVM-based ice accretion solver. The computational results were validated by comparison with the experimental data. The parallel performance of the MPI and Coarray methods were compared and found to be similar on the airflow solver. Further, the Coarray-based implementation on the water droplet solver showed good speedup and efficiency for the given number of mesh elements and processors.