Nobuhiko Yamasaki

Improved Hybrid Prediction of Fan Noise

To predict fan noise level, the hybrid scheme, i.e., the combinational approach of a numerical simulation based on the three-dimensional unsteady Reynolds-averaged NavierStokes (URANS) equations and an analytical calculation based on the three-dimensional linear singularity theory, is to be improved. It takes into account the acoustic effects on the unsteady loading on the rotor blades as well as the stator vanes. The calculated noise level is compared more favorably with the experimental data, and the superiority of the improved hybrid scheme is confirmed.

Unsteady Aerodynamic Forces on Vibrating Annular Cascade Blades: Cross-Validation of the Linear Unsteady CFD Calculations Using the TVD Scheme and the Double Linearization Theory

The paper presents the formulation to compute numerically the unsteady aerodynamic forces on the vibrating annular cascade blades. The formulation is based on the finite volume method, the type, and the TVD scheme, following the UPACS code developed by NAL, Japan. By applying the TVD scheme to the linear unsteady calculations, the precise calculation of the peak of unsteady aerodynamic forces at the shock wave location like the delta function singularity becomes possible without empirical constants. As a further feature of the present paper, results of the present numerical calculation are compared with those of the double linearization theory (DLT), which assumes small unsteady and steady disturbances but the unsteady disturbances are much smaller than the steady disturbances. Since DLT requires far less computational resources than the present numerical calculation, the validation of DLT is quite important from the engineering point of view. Under the conditions of small steady disturbances, a good agreement between these two results is observed, so that the two codes are cross-validated. The comparison also reveals the limitation on the applicability of DLT.Copyright