Masashi Kanamori

Shock wave detection in two-dimensional flow based on the theory of characteristics from CFD data

A method to detect the discontinuity of a shock wave from computational fluid dynamics (CFD) data was developed based on the theory of characteristics and was adopted to replace the inaccurate method that involves observation of the location of steep spatial gradient with respect to the primitive variables, such as pressure. A shock wave is mathematically defined as a convergence of characteristics, in which each type of Riemann invariant is conserved within each characteristic. In the vector field of the characteristics, such convergences are interpreted as critical lines of the streamlines, which are easily identified by calculating the eigenvectors of the vector field of propagation velocity of the Riemann invariant. The use of a triangular cell system enables unique determination of the linearized vector field in each cell and enables analytical identification of the critical line within this field. Shock waves can be successfully extracted using this method. The method can be extended to the detection of moving shock waves by considering the coordinate moving with the shock.

Three-Dimensional Shock Wave Detection Based on the Theory of Characteristics

This paper describes a method to detect three-dimensional, steady inviscid shock waves from computational fluid dynamics data. The method is based on the principle that the collision of the characteristics of the same family causes the generation of a shock wave in a two-dimensional flow. In a three-dimensional flowfield, however, there is an infinite number of characteristics. Therefore, the plane on which the streamline can be treated locally as a planar curve is introduced, and the characteristic as an intersection between the Mach cone and this plane is defined. As a result, the shock waves in a three-dimensional, steady flowfield can be treated by a similar methodology as that in a two-dimensional flowfield.

Shock Wave Detection based on the Theory of Characteristics for CFD Results

A method to detect the discontinuity of a shock wave from computational fluid dynamics (CFD) data was developed based on the characteristics. A shock wave is mathematically defined as a convergence of characteristics. Such convergences are interpreted as critical lines of the streamlines, which are easily identified by calculating the eigenvectors of the vector field for the propagation velocity of the Riemann invariants. Shock waves can be successfully extracted using our method. Three-dimensional shock waves can also be detected successfully by extending the idea for two-dimensional flows and defining the characteristics which contribute the generation of shock waves.

Robust Low-Boom Design Based on Near-Field Pressure Signature in Whole Boom Carpet

An inverse low-boom design method using a reversed equivalent area Ae,r based on off-body pressure distributions is effective because this method captures three-dimensional effects in a flowfield. In this paper, a robust low-boom design method using Ae,r is proposed to consider off-track sonic boom loudness. Computing costs are reduced by applying multipole analysis, which allows the capture of three-dimensional effects, even when an off-body location is close to a body. In terms of robustness, it is difficult to set feasible target Ae,r distributions in a whole boom carpet. Unfeasible targets may lead to results contrary to the design intent. Thus, the target is imposed only on the undertrack Ae,r distribution. In addition, second derivatives of Ae,r having direct relation to the F function are controlled in the whole boom carpet. As a result, second derivatives are successfully controlled as intended by free-form deformation and genetic-algorithm-based optimization. The undertrack Ae,r meets the target ...

Prediction of various sonic boom signatures observed in large scale experiment

Results of predicting sonic boom signatures observed in D-SEND#2 flight test are presented in this study. D-SEND#2 flight test was held in northern Sweden in 2015 in order to demonstrate JAXA’s low-boom design concept. The flight test provides three kinds of waveforms: conventional N wave, diffracted U-shaped waveform, and the low-boom waveform. In this study, the method of predicting one or more waveforms above will be introduced.

Development of nonlinear acoustic propagation analysis tool toward realization of loud noise environment prediction in aeronautics

Shown in this paper is an introduction of a prediction tool for the propagation of loud noise with the application to the aeronautics in mind. The tool, named SPnoise, is based on HOWARD approach, which can express almost exact multidimensionality of the diffraction effect at the cost of back scattering. This paper argues, in particular, the prediction of the effect of atmospheric turbulence on sonic boom as one of the important issues in aeronautics. Thanks to the simple and efficient modeling of the atmospheric turbulence, SPnoise successfully re-creates the feature of the effect, which often emerges in the region just behind the front and rear shock waves in the sonic boom signature.