The vortex streets in the wake behind a two-dimensional body were studied experimentally in a wind tunnel at the lower Reynolds number than the critical value. There were the regular mode at lower Reynolds numbers than the critical value and the irregular mode at the higher Reynolds numbers of vortex shedding for three types of two-dimensional bodies. In the regular mode, the rearrangement of vortex street took place at the downstream locations in the wake. The streamwise variation of the velocity fluctuations was similar to that in the wake of a circular cylinder. The dimensionless frequency, F=fh2/v, was proportional to the Reynolds number both in the primary and the secondary vortex street. The F-Re graphs for both vortex streets were nearly parallel to each other. The rearrangement of vortex street in the wake of the two-dimensional bodies was found out to be very similar to that for a circular cylinder.
In the development phase of an aircraft gasturbine, the required performances of the gasturbine components, for example fan, compressor, combustor and turbine, are decided after general consideration of the engine total performance. In case of compressor the design value of mass flow, compression ratio, efficiency, and surge margins correspond to these component performances. For accomplishing the required performance, the tedious and expensive works of design for modification, production and tests were laboriously repeated as in the past. As efficiently promoting these development cycle, it is important to get the useful data for two purposes, one is redesign for getting better performance and the other is to fix variable factors adjusting the difference from design values. This paper introduces the practical and useful method describing the relation between component performances of the compressor and the combination of the stator setting angle analyzing by statistical methods based on the experimental data.
A lamination tailoring technique is proposed in order to control a coefficient of thermal expansion of graphite/epoxy composites in a principal direction. This technique consists of two concepts of the thermoelastic invariants and the lamination parameters. The expansion free condition yields to a parabola in the feasible region of the lamination parameters. The calculated curves for a wide range of temperature intersect almost at a point. A laminate with the lay-up construction corresponding to this point exhibits an approximately null coefficient of thermal expansion in one direction in that temperature range. Some experimental results indicate that the present procedure is possible and promising.
Flights against microburst are analysed as optimal control problems. A typical microburst model is used with a Dryden gust model superimposed on it. Control laws are those of an optimal regulator with Kalman-filter for noisy measurements. The result shows the importance of the accurate measurements of ground and air velocity as well as climb rates. The result also shows a control law which is close to optimal and which is feasible for practical use.
Desmarais' method for computing the incomplete Struve function in the unsteady lifting surface kernel function is world-famous. It was adopted in a lifting surface computation method, PCKFM, which is also highly evaluated in USA. As a representative of Desmarais' method, “D 12. 1” is investigated in this report, being compared with the method developed by us previously. It is found that Desmarais' method has an own defect that it becomes erroneous in proximity to the X-axis. Moreover it treats numerically some parts of the singularities of the kernel function, which is a violation of general numerical rules. Thus although there is a little merit resulting from computer time, we could not appreciate the Desmarais' method because of the above-mentioned defects.