No abstract

In this study, effects of the tip cavity with various depths, widths, and locations on the leakage flow and performance of an axial turbine cascade have been investigated numerically. The blade was a linear model of the tip section of the GE-E 3 high-pressure turbine first-stage rotor blade. The Delayed Detached Eddy Simulation (DDES) model was used in the simulations. The computational results showed that the leakage mass flow rate and mass-averaged total pressure loss decreased as the depth and width of the tip cavity increased. And, it was shown that the cavity near the pressure side is more effective than that near the suction side. These effects depend on a vortex generated behind the pressure side in the cavity, which is changed with the depth, width, and location. The vortex entrains the leakage flow through the clearance toward the bottom of the cavity and in the chord wise direction, which reduces the flow leaking out.

:The moving surface method based on Quette Flow-type momentum addition was proposed as a new flow separation control method in order to suppress the flow separation over a flap at high attack angles and make lift enhancement. The effectiveness of the proposed method as well as the mechanism for suppressing the separation was studied by numerical simulations and experimental measurements in this study. The numerical results show that the moving surface works well to suppress the flap flow separation, so that lift coefficient can be increased significantly. In addition, the moving surface decreases pressure not only in the original separated flow region, but also in the leading edge region. Furthermore, the experimental result agrees with the numerical one in the case of a lower Mach number, which can validate the numerical results. Thus, the moving surface method proposed here is a promising method for controlling the flow separation over the flap.

No abstract

A boomerang thrown properly into the air can fly in an elliptical path and return to the point of origin. In this study, such a motion of the boomerang was numerically simulated to clarify the mechanism of the motion. The simulation was conducted by the double CFD method which is the coupling method of the computational fluid dynamics and the computational flight dynamics. We considered the case that a small flat boomerang was thrown with a translational and a rotational velocity, an angle of the translational velocity from a horizontal plane, and no roll angle. Results showed that the boomerang lifted and traveled in a path with changing roll and pitch angles due to a pressure distribution on its surface, and returned to a point near the origin. Furthermore, an experiment was performed to confirm the validity of the computational results, and the experimental result was qualitatively corresponding to the computational results.