Taku Nonomura

This paper presents a computational study of the flow and flow-induced acoustic fields of a supersonic jet impinging on an inclined flat plate. For the numerical simulations, we solved three-dimensional compressible Navier-Stokes equations with a modified weighted compact nonlinear scheme. We analyzed the simulation results mainly from the viewpoint of the acoustic emission and propagation mechanism, and we investigated the acoustic field characteristics such as directivity, their spectra, and a

A new technique for a finite-difference weighted essentially nonoscillatory scheme (WENO) on curvilinear grids to preserve freestream is introduced. This technique first divides the standard finite-difference WENO into two parts: (1) a consistent central difference part and (2) a numerical dissipation part. For the consistent central difference part, the conservative metric technique is directly adopted. For the numerical dissipation part, it is proposed that the metric term should be frozen for

A new dynamic mode decomposition (DMD) method is introduced for simultaneous system identification and denoising in conjunction with the adoption of an extended Kalman filter algorithm. The present paper explains the extended-Kalman-filter-based DMD (EKFDMD) algorithm which is an online algorithm for dataset for a small number of degree of freedom (DoF). It also illustrates that EKFDMD requires significant numerical resources for many-degree-of-freedom (many-DoF) problems and that the combinatio

A novel dynamic mode decomposition (DMD) method based on a Kalman filter is proposed. This paper explains the fast algorithm of the proposed Kalman filter DMD (KFDMD) in combination with truncated proper orthogonal decomposition for many-degree-of-freedom problems. Numerical experiments reveal that KFDMD can estimate eigenmodes more precisely compared with standard DMD or total least-squares DMD (tlsDMD) methods for the severe noise condition if the nature of the observation noise is known, thou

The coefficients of higher order weighted compact nonlinear scheme (WCNS) and the resolutions of the family of higher order WCNS are investigated. The coefficients of seventh and ninth order WCNS are calculated by using MATHEMATICA. Seventh and ninth WCNS can resolve the discontinuity without numerical oscillations as well as fifth order WCNS. Seventh and Ninth order WCNS have the higher resolution on the one-dimensional shock-entropy interaction problem with few grid points than fifth order WCN

The effects of plate angle on acoustic waves from a supersonic jet impinging on an inclined flat plate at angles of 30, 45, and 60 deg are numerically investigated. Three-dimensional compressible Navier–Stokes equations are solved using the modified weighted compact nonlinear scheme. Similar to previous studies, the acoustic fields indicate that there are at least three types of acoustic waves in all of the cases considered herein: 1) Mach waves generated from the shear layer of the main jet, 2)