The present paper proposes a numerical method for the solution of the two-dimensional incompressible viscous flow problems. Numerical technique is described for a general set of equations, namely the BOUSSINESQ equations. The momentum and energy equations are solved by the modified FLIC method, while the pressure equation is solved by the finite element method. The present method is applied to two examples: one is the flow in a rectangular cavity driven by the uniform translation of the top wall, while the other is the flow in a square cavity driven by buoyancy forces that caused by temperature differences. The results thus obtained are compared with those obtained by the other conventional methods to demonstrate the validity of the present approach. The problems treated in the present paper are limited to two-dimensional flow. However, an extension of the present technique to threedimensional flow is straight forward, although it is inevitably accompanied by an increase of computing time.
An acoustic model is obtained through expanding LIGHTHILL's theory. And a method is presented for estimating the noise generated by subsonic jet using the acoustic model. The acoustic characteristic of jet is determined by aerodynamic property of each small volume element in jet flow. And the each volume element is regarded as individual generator. As the result, the predicted overall sound pressure level, sound pressure spectra and acoustic power spectra are compared with experimental data. The intensity distribution of the sound source in jet flow obtained from the present theory agrees with RIBNER's dimensional theory.
Probabilistic property of a nonlinear vibration of a rectangular panel is studied analytically and experimentally. The test model of a rectangular panel with clamped edges was clamped on an electromagnetic shaker and was randomly excited under approximately band-limited white noise of acceleration. In order to prevent thermal effect on the inplane stress condition of the panel, super-invar whose thermal expansion coefficient is 1×10-7 was used as the materials of the test plate and clamping block. Probabilistic quantities of a center deflection and an edge strain were measured through a real time auto-correlator and a FOURIER transformer. The deflection is expanded in the series of independent modes, and a set of nonlinear equations of vibration of multi-degree of freedom, having nonlinear damping terms, are derived in the frame work of the linear viscoelastic stress-strain relation and the large deflection theory of a thin plate. The solution of the equation of three mode approximation are numerically obtained by using a simulation method. A good agreement is observed between the experiment results and the simulation solution. Besides, statistical linearization technique is used to calculate the root mean square and is found to give fairly good approximate solution. It is clarified that the three-mode approximation and nonlinear damping force are required to get a good agreement between theory and experiment.
Originally an airplane is the vehicle which moves toward its nose direction. But strictly speaking, the direction of flight path and that of nose are not the same due to the existence of the angle of attack α and the sideslip angle β (except due to the drift angle). Then, is it possible to control flight attitude (nose direction) and flight path separately by controlling these aerodynamic angles (which are controlled through elevator and rudder)? We begin with this question and first study qualitatively the relation between "flight attitude and path." And then, their quantitative relations, that is, the relations of attitude angles and path angles (these are EULER angles) are derived in explicit and easily applicable forms by means of both algebraic and geometric methods.