Flow Deflection in Intersected Tubes

In order to verify the flow interference at the fracture intersections, a group of hydraulic simulations of crossing flow was carried out. The manifold interference effects at the intersection of fractures on water flow has been confirmed extensively either in the normal or in the oblique intersected tubes as well as in the intersected tubes of either equal or variant diameters. Consequently, suggest that the fissure network can no longer be taken as a set of solitary fractures, but as a set of elementary intersected fractures. The deflection effect at fracture intersections on the water flow should be taken into consideration when is dealt with any theory related to the water migration in fractures.

ABRUPT DEFLECTED SUPERCRITICAL WATER FLOW-REVISED THEORY OF SHOCK WAVE

The shock wave angle and depth ratio of the abrupt deflected supercritical water flow due to deflector was investigated experimentally and theoretically. A correction coefficient of the hydro-dynamic pressure ξ was introduced to generalize the momentum equation in the perpendicular direction to the shock front. An extensive series of tests were conducted in a 1 m wide flume with the Froude number ranging from 1.70 to 8.37, the deflection angle ranging from 5° to 40° and the length of deflector ranging from 0.28 m to 1 m. A dimensionless parameter K was defined to depict the ratio of the flow height to flow thickness. Test results show that the val ue of ~, the correction coefficient of the non-hydrostatic pres- sure distribution, decreases with the increase of the value of K An empirical relationship between the value of ξ and the val ue of K was proposed. It is indicated that the relative errors of the results calculated by the revised theory is much smaller than that obtained from the Ippen theory. Finally, a simple explicit expression was suggested to calculate the shock wave height ratio in consideration of the effect of the non-hydrostatic pressure distribution.

ABRUPT DEFLECTED SUPERCRITICAL WATER FLOW IN SLOPED CHANNELS

The effect of the bottom slope on abrupt deflected supercritical water flow was experimentally and theoretically studied. Model tests were conducted in a flume of 1.2 m wide and 2.6 m long with sloped bottom at an angle 35.54°, its length of deflector was 0.2 m and the deflection angles were 15° and 30°. An approximate method for calculating the shock wave angle and depth ratio of the abrupt deflected supercritical water flow was suggested, and a correction coefficient for the hydrodynamic pressure was introduced to generalize the momentum equation in the direction perpendicular to the shock front. It must be noticed that in the sloped channel the shock wave angle and the depth ratio are no longer constant as those in the horizontal channels, but slowly change along the shock front. The calculated results are in good agreement with measured data.

Numerical Simulation of Deflecting Flow in a Symmetric Enlarged Channel

Numerical results of three-dimensional separated flow and heat transfer in a rectangular channel with a sudden expansion are presented in this paper. Numerical simulations of Navier-Stokes and energy equations are carried out using the finite difference method. The results of three-dimensional calculations are compared with the two-dimensional ones, and effects of the aspect ratio of channel upon the flow are shown. The transition from symmetric to asymmetric flow appears at lower Reynolds number as increasing the aspect ratio. The details of local heat transfer characteristics in two different separated flow regions on two downstream walls are clarified. Two-dimensionality of the flow and heat transfer almost disappears for the aspect ratio considered.

Numerical study of camber and stagger angle effects on the aerodynamic performance of tandem-blade cascades

Jet engine manufacturers and designers are seeking for lighter and smaller type of axial compressors.Improving the aerodynamic characteristics of blades is carried out by controlling the boundary layer.One way to control the boundary layer is using tandem blades.Tandem-blade cascades are capable of using highly loaded stages for axial compressors because they provide more works than single-blade cascades.In other words,tandem blades help to achieve a specified total pressure ratio with less number of stages.Therefore,one of the most important problems for researchers is to optimize the aerodynamic parameters of tandem blades.Changing the geometrical parameters of blades is a method to achieve this purpose.In this work,the stagger and camber angle of each blade are first changed while the other geometrical parameters such as overall camber,total stagger angle,the axial overlap,percent pitch and chord ratio are fixed.Secondly,the overall camber angle of tandem blade is changed by increasing the difference between the stagger angle of the first and second blade while the type of two airfoils,axial overlap and percent pitch,overall chord length and overall stagger angle are fixed.The aerodynamic performances of the generated tandem-blade cascades are obtained using two-dimensional numerical solution of flow.For this,a viscous turbulent flow solver is used for solving the Navier-Stokes equations.In these simulations,inlet Mach number is fixed to 0.6.