Control of the velocity distribution is a fundamental and an important problem in many engineering problems. In this paper results of theoretical investigation of axisymmetrical flow through a gauze or a screen and a gauze shape of producing shear flow at far downstream are presented. The analytical method in this paper is based upon the linearized theory in which a method of asymptotic expansion is used. The empirical values of gauze resistance which are related with the velocity distributions for upstream and downstream of the gauze, the gauze shape, and the gauze coefficient are used to analyze the steady, inviscid, and rotational fluid flow. The shape of gauze and the velocity distributions are calculated by means of using the FOURIER-BESSEL expansion. It is seen that the using of fifteen zeros of Bessel functions is enough to carry out the numerical calculation with high accuracy for these examples.
The main feature of the flow past a slender delta wing is the existence of leading-edge separation. It has been shown in many investigations that this separation greatly contributes the wing performance. But no papers exist about a slender parawing with leading-edge separation. In the present paper, the flow over a slender one-lobed parawing with leading-edge separation is considered by using the simple model of BROWN and MICHAEL and the slender body theory, assuming the flow field to be conical. Wing shape, vortex position and strength can be found from a set of non-linear simultaneous equations which describe the stream surface condition of the wing and the statical balance between the surface tension and the pressure jump through the wing, together with the zeroforce condition on the vortex system. The solutions are obtained for various values ofλand K, i.e. the wing tension and the incidence parameter, respectively, by making use of NEWTON-RAPHSON's numerical procedure. Normal force and pressure distribution are also calculated from the values that specify the wing shape, the vortex position and strength. It is shown that the wing shape is a little different from the attached flow solution because of high negative pressure on the upper surface caused by a separation vortex and that the maximum normal force occurs at a certain value of λin the case where K is large.
Noise measuring tests of a low-bypass-ratio turbofan engine were conducted, using the hybrid bulk-resonator type acoustic treatment in the fan section and the lobe type internal mixer in the exhaust section. The bulk-resonator type acoustic treatment is composed with a thin layer of polyamid fiber felt protected by the perforated sheet metal on its surface and backed by an air cavity behind the felt layer. Test results revealed that this kind of acoustic treatment was effective for reduction of fan noise thru broad frequency rang from approach to take-off power, and the mixing nozzle was effective for jet noise reduction in high power range with a slight thrust loss which was not considered to be caused only by installation of the mixing nozzle.
A computer oriented asymptotic expansion of a singular integral function is presented. The function dealt with appears in the kernel of the integral equation which is solved for pressure distributions of subsonic unsteady lifting surfaces. Values of the function can be accurately computed in short times by using the present expansion. The expansion series includes terms which are calculated with the aid of a recurrence formula. Every singular part is, however, explicitly written as an initial term. Other approximations are evaluated by comparing them with the present results.