Low speed experiments are carried out on the aerodynamic properties of three oblate spheroids and a sphere with their axis of symmetry parallel to the oncoming stream for the REYNOLDS number 1.7-8.5×105.The length ratios of the minor axis to the major one are 5/6, 4/6 and 3/6. The curves of drag coefficient versus REYNOLDS number for spheroids are shown to be similar to that of a sphere with translation to the higher regions of REYNOLDS number and drag coefficient with increasing flatness of spheroid. The flattest one, however, behaves like a circular disk, no critical region being found in the REYNOLDS number tested in the present experiment. The drastic change in the pressure distribution from subcritical to supercritical regions and the appearance of the second separation line occur simultaneously for the sphere and the fullest model but this is not the case of the model with moderate flatness. This model seems to have a transient region in which the pressure distribution is of the supercritical type but separation is not axisymmetric, varing its position periodically, and when the line turns to near axisymmetric type and at the same time the pressure on the backside of the model rises, drag reduction occurs. The flattest model reveales no remarkable changes both in the pressure distribution and in the separation line. Applying the CEBECI-SMITH method, calculations are also made of the laminar boundary layers in the subcritical range, giving distributions of boundary layer thickness, shape factor, surface shearing stress and the position of the separation line. The agreement between the measured and the calculated separation angles are fairly good except for the flattest spheroid.
A small perturbation analysis is presented of a curved turbulent half-jet for an incompressible fluid. Expressing the small parameter as a power function of the streamwise coordinate x, nonsimilar flow fields are treated where x-axis is the free streamline of a curved irrotational flow to which the free shear layer is matched. Omitting conveniently the difference term of the two components of the normal stress in the REYNOLDS equation and using the SAWYER's expression for shear stress, approximate analysis is carried out, with boundary conditions imposed accurately and approximately to the first order and the second order solutions, respectively. Some velocity distributions are calculated on a similar flow, a flow along a circular arc, and a flow like an impinging jet. The results are presented graphically.
Interaction of supersonic flow (with nose Mach number MN_??_8) with radial jets, are investigated experimentally by using the shock tunnel, and some results are compared with theory. A hemisphere-cylinder and a cone-cylinder, both with radial jet nozzles, are used as models, The results of pressure measurements and SCHLIEREN photographs are shown as follows. In the case of the hemisphere-cylinder, the side boundary of the radial jet, injected from the cylindrical surface, acts like a forward-facing step, and the viscous interaction produces a dead water region in front of the radial jet. In the experimental case the detached main shock, emanating from the hemisphere nose, runs far outside from both the body surface and the jet-interaction region, and the so-called plateau pressure can be seen in the dead water region. In the case of the cone, also the jet acts like a forward-facing step, and produces a dead water region. In the present case, however, the main shock from the nose of the cone, runs rather closely to the body surface, and there can be seen direct interaction between the main shock and the jet when the jet stagnation pres. sure is high. In such a case, the surface pressure in the dead water region also goes up compared to that without jet, but its distribution does not show a clear plateau pattern but a rather wavy one. The outer boundary of the dead water region, calculated from the experimental pressure distributions, compares well with SCHLIEREN photograph.
In this paper we propose the rational computational strategy for the contact problems included the effect of plastic large deformations in order to analyse an axisymmetric progressive plastic buckling of cylindrical shell under an axial compression. The major contents of this study are summarized as follows; 1) the description of the procedure to introduce the constrained conditions forced on the contact surfaces to the incremental virtual work principle through LAGRANGE's multipliers. 2) the explanation of the logic that determine the contact state at each deformation stage and supply the informations for following step. 3) the introduction of the triple iterative scheme of computation which would combine two nonlinear terms, namely the effective plastic loads and the frictional slide loads, and the factor controlling the amplitude of displacement increments at the stage when contact condition change. In connection with this formulation we use the standard FE technique. The result of computation in the case of Al-Alloy tube confirms us that the present strategy is feasible to examine the collapse process and is applicable to certain class of contact problems.
In this paper, the relation between dragcoefficient and project ratio used for design was chosen as a subject of the study. We investigated the wind force acting on pipe-towers by wind tunnel tests and, on the basis of experimental results, clarified that relation. And also the project ratio was applied in stead of the repletion ratio which has been used. As a result the expression of PD (kg) for arbitrary angle was improved to given the simplified empirical equation. But one thing which we would like to mention here is that this wind load means the hours mean of it acting on pipe-towers, etc. Therefore, the vibration with the vortex envolved in slip stream of the tower is not considered. The tower section is delt with nothing but the square section which is well used for a number of free standing tower.
The pressure distribution for circular-arc airfoil calculated with inviscid theory is generally in good agreement with the experiments over the surface of the airfoil except for the vicinity of the surface shock wave. The said discrepancy in the surface pressure distribution near the shock wave can be considered by the interaction of shock wave with boundary layer. As there is a strong coupling between the inner boundary layer and the outer inviscid flow, the solution must be developed simultaneously in both regions. In the present transonic investigation, a boundarylayer integral approach is combined with a finitedifference relaxation method to calculate the viscous interactions. The pressure distribution is obtained for the attached turbulent flow on circular-arc airfoil at zero angle of attack, and the results remarkably agrees with the experiment of KNECHTEL.