STUDY ON THE FUEL AIR MIXING INDUCED BY A SHOCK WAVE PROPAGATING INTO A H_2-AIR INTERFACE

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｆｕｅｌａｉｒｍｉｘｉｎｇｉｎａｓｈｅａｒｌａｙｅｒｆｌｏｗｉｓａｎｉｍｐｏｒｔａｎｔｐｒｏｂｌｅｍｉｎｓｔｕｄｙｉｎｇｃｏｍｐｒｅｓｓｉｂｌｅｆｌｏｗａｎｄｓｕｐｅｒｓｏｎｉｃｃｏｍｂｕｓｔｉｏｎ ,ｓｕｃｈａｓｆｕｅｌｄｉｆｆｕｓｉｏｎａｎｄｍｉｘｉｎｇｉｎａＳｃｒａｍｊｅｔ[1].Ｒｏｓｈｋｏ[2 ]ｓｔｕｄｉｅｄｅｘｐｅｒｉｍｅｎｔａｌｌｙｔｈｅｐｈｅｎｏｍｅｎｏｎｏｆｆｕｅｌａｉｒｍｉｘｉｎｇｉｎａｓｕｂｓｏｎｉｃｓｈｅａｒｆｌｏｗａｎｄｆｏｕｎｄｌａｒｇｅ ,ｃｏｈ…     

REMARKS ON THE PAPER“THE EXTINCTION BEHAVIOR OF THE SOLUTIONS FOR A CLASS OF REACTION -DIFFUSION EQUATIONS”

ＴｈｅｆｏｌｌｏｗｉｎｇＬｅｍｍａｓｔａｔｅｄ (ｉｎ :ＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓａｎｄＭｅｃｈａｎｉｃｓ (ＥｎｇｌｉｓｈＥｄｉｔｉｏｎ) ,2 0 0 1 ,2 2 ( 1 1 ) :1 3 52 -1 3 56)ｗａｓａｐｐｌｉｅｄｔｏｄｅｓｃｒｉｂｅｔｈｅａｓｙｍｐｔｏｔｉｃｂｅｈａｖｉｏｒｓｏｆｓｏｌｕｔｉｏｎｓｏｆａｃｌａｓｓｏｆｒｅａｃｔｉｏｎ＿ｄｉｆｆｕｓｉｏｎｅｑｕａｔｉｏｎ .Ｏｎａｃｃｏｕｎｔｏｆｔｈｅｓｐｅｃｉａｌｐｒｏｐｅｒｔｙｏｆｔｈｅｓｕｐｅｒｓｏｌｕｔｉｏｎ(ｉ.ｅ .,ａｎｏｎｚｅｒｏｓｏｌｕｔｉｏｎ…     

A numerical study for small amplitude T-S waves in a supersonic boundary layer

ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｅｎｔｌｙ ,ｔｈｅｐｒｏｂｌｅｍｏｆｔｒａｎｓｉｔｉｏｎｉｎｓｕｐｅｒｓｏｎｉｃｂｏｕｎｄａｒｙｌａｙｅｒｓｈａｓａｔｔｒａｃｔｅｄｍｏｒｅａｎｄｍｏｒｅａｔｔｅｎｔｉｏｎｄｕｅｔｏｉｔｓｔｅｃｈｎｉｃａｌｉｍｐｏｒｔａｎｃｅ .Ｕｐｔｏｎｏｗ ,ｍｏｓｔａｎａｌｙｓｅｓｗｅｒｅｌｉｎｅａｒａｎａｌｙｓｉｓ,ａｎｄｄｅｔａｉｌｅｄｅｘｐｅｒｉｍｅｎｔｓａｒｅｖｅｒｙｒａｒｅ .Ｓｏｍｅｐｅｏｐｌｅｈａｖｅｔｒｉｅｄｔｏｅｘｔｅｎｄｔｈｅｎｏｎｌｉｎｅａｒｔｈｅｏｒｙｏｆｈ…     

THE INTERACTION PROBLEM BETWEEN THE ELASTIC LINE INCLUSIONS

ＩｎｔｒｏｄｕｃｔｉｏｎＯｆａｌｌｔｈｅｆｉｂｅｒ＿ｒｅｉｎｆｏｒｃｅｄｃｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌｓ,ｔｈｅｓｈｏｒｔ＿ｆｉｂｅｒｃｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌｎｏｔｏｎｌｙｓｔｒｅｎｇｔｈｅｎｓｔｈｅｍａｔｒｉｘｂｕｔａｖｏｉｄｓｄｅｆｅｃｔｉｏｎｓｏｆｔｈｅｌｏｎｇ＿ｆｉｂｅｒｃｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌａｓｗｅｌｌ.Ｔｈｅｍｉｃｒｏ＿ｍｅｃｈａｎｉｃｓａｂｏｕｔｉｔｓｕｃｈａｓｆｒａｃｔｕｒｅ ,ｆａｔｉｇｕｅａｎｄｄａｍａｇｅｉｓｖｅｒｙｃｏｍｐｌｅｘ .Ｉｎｔｈｅｐｒｅｖｉ…     

Blow-Up Estimates for a Non-Newtonian Filtration System

ＩｎｔｒｏｄｕｃｔｉｏｎａｎｄＰｒｏｂｌｅｍｉｎｔｈｅＲｅｓｅａｒｃｈｏｆＴｏｒｏｉｄＴｈｅｓｔｒｕｃｔｕｒｅｏｆｐｏｓｉｔｉｖｅｓｏｌｕｔｉｏｎｓｆｏｒｑｕａｓｉ＿ｌｉｎｅａｒｒｅａｃｔｉｏｎ＿ｄｉｆｆｕｓｉｏｎｓｙｓｔｅｍｓ (ｎｏｎｌｉｎｅａｒＮｅｗｔｏｎｉａｎｆｉｌｔｒａｔｉｏｎｓｙｓｔｅｍｓ)ａｎｄｓｅｍｉ＿ｌｉｎｅａｒｒｅａｃｔｉｏｎ＿ｄｉｆｆｕｓｉｏｎｓｙｓｔｅｍｓ (Ｎｅｗｔｏｎｉａｎｆｉｌｔｒａｔｉｏｎｓｙｓｔｅｍｓ)ｉｓａｈｏｔｔｏｐｉｃｉｎｔｈｅｓｔｕｄｙｏｆｎｏｎｌｉｎｅａｒｄ…     

Modeling and analysis of a coupled rigid-flexible system

ＩｎｔｒｏｄｕｃｔｉｏｎＭａｎｙｍｅｃｈａｎｉｃａｌｓｙｓｔｅｍｓｓｕｃｈａｓｒｏｂｏｔｍａｎｉｐｕｌａｔｏｒ,ｔｕｒｂｉｎｅｂｌａｄｅｓ,ｈｅｌｉｃｏｐｔｅｒｐｒｏｐｅｌｌｅｒａｎｄｍａｎ＿ｍａｄｅｓａｔｅｌｌｉｔｅｗｉｔｈｆｌｅｘｉｂｌｅａｔｔａｃｈｍｅｎｔｓａｒｅｃｏｍｐｏｓｅｄｏｆｒｉｇｉｄａｎｄｆｌｅｘｉｂｌｅｂｏｄｉｅｓ．Ｔｈｅｙａｒｅｃａｌｌｅｄｃｏｕｐｌｅｄｒｉｇｉｄ＿ｆｌｅｘｉｂｌｅｓｙｓｔｅｍｓ．Ｃｏｒｒｅｃｔｐｒｅｄｉｃｔｉｏｎｓｏｆｔｈｅｂｅｈａｖｉｏｒｏｆｆｌｅｘｉｂｌ…     

Linear and Nonlinear Aerodynamic Theory of Interaction between Flexible Long Structure and Wind

ＩｎｔｒｏｄｕｃｔｉｏｎＡｌｏｎｇｗｉｔｈｔｈｅｉｎｃｒｅａｓｅｏｆｔｈｅｆｌｅｘｉｂｉｌｉｔｙｏｆｓｌｅｎｄｅｒｓｔｒｕｃｔｕｒｅｓｅｔｉｎｔｈｅｗｉｎｄｆｉｅｌｄ ,ｓｕｃｈａｓｔｈｅｌｏｎｇ＿ｓｐａｎｂｒｉｄｇｅａｎｄｈｉｇｈ＿ｒｉｓｅｂｕｉｌｄｉｎｇ ,ｔｈｅａｃｔｉｏｎｓｏｆｕｎｓｔｅａｄｙａｅｒｏｄｙｎａｍｉｃｆｏｒｃｅｓｗｉｌｌａｃ ｃｅｌｅｒａｔｅ,ａｎｄｈｏｗｔｏｓｏｌｖｅｔｈｅａｅｒｏｅｌａｓｔｉｃｐｒｏｂｌｅｍｓｉｓｇｅｔｔｉｎｇｍｏｒｅｉｍｐｏｒｔａｎｔ.Ｔｈｅａｅｒｏｅｌａｓ…     

PANSYSTEMS METHODOLOGY AND CONSTRUCTION OF MAGIC SQUARES

ＩｎｔｒｏｄｕｃｔｉｏｎＡｒｅｆｉｎｅｄｅｐｉｔｏｍｅｏｆｖａｒｉｏｕｓｐａｎｓｙｓｔｅｍｓｍｅｔｈｏｄｓｉｓｔｏｃｏｍｐｒｅｈｅｎｄａｎｄｏｐｅｒａｔｅａｂｏｕｔ 2 0ｐａｎｓｙｓｔｅｍｓｃａｔｅｇｏｒｉｅｓｗｈｉｃｈｃａｎｂｅｅｘｐａｎｄｅｄａｓｔｈｅｆｏｌｌｏｗｉｎｇｐｉｔｈｙｆｏｒｍｕｌａｓｅｘｐｒｅｓｓｉｏｎｓ:Ｔｈｅｐａｎｄｅｒｉｖａｔｉｖｅｓ (ｏｒｔｈｅｃｈａｎｇｅ＿ｃｈａｎｇｅｒｅｌａｔｉｏｎｓ)ｏｆｔｈｅｅｘｔｅｒｉｏｒ＿ｉｎｔｅｒｉｏｒ(ｏｒｔｈｅｆｕｎｃｔｉｏｎ＿ｓｔｒｕｃｔｕ…     

Self-Similar Solutions of Fracture Dynamics Problems on Axially Symmetry

ＩｎｔｒｏｄｕｃｔｉｏｎＣｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌｓａｒｅａｌｍｏｓｔｍａｄｅｕｐｏｆｆｉｂｅｒａｎｄｍａｔｒｉｘｗｉｔｈａｎｉｓｏｔｒｏｐｉｃｍａｃｒｏｓｔｒｕｃｔｕｒｅ ,ｗｈｏｓｅｖａｒｉｏｕｓｓｔｒｕｃｔｕｒｅｓａｒｅｅａｓｙｔｏａｐｐｅａｒａｐｅｎｎｙ＿ｓｈａｐｅｄｍｉｃｒｏｃｒａｃｋｉｎｔｈｅｐｒｏｃｅｓｓｏｆｔｈｅｉｒｗｏｒｋ.Ｗｈｅｎｉｔｅｘｔｅｎｄｓｇｒａｄｕａｌｌｙ ,ｔｈｅｓｔｒｕｃｔｕｒｅｗｉｌｌｌｅａｄｔｏｄｅｓｔｒｕｃｔｉｏｎ .Ｉｔｉｓｗｅｌｌ＿ｋｎｏｗｎｔｈａｔ…     

A discrete algorithm for complex frequency-domain convolutions

ＩｎｔｒｏｄｕｃｔｉｏｎＩｔｉｓｗｅｌｌ＿ｋｎｏｗｎｔｈａｔｔｈｅＬａｐｌａｃｅｔｒａｎｓｆｏｒｍｏｆｔｈｅｐｒｏｄｕｃｔｏｆｔｗｏｔｉｍｅ＿ｄｏｍａｉｎｓｉｇｎａｌｓｅｑｕａｌｓｔｈｅｃｏｍｐｌｅｘｆｒｅｑｕｅｎｃｙ＿ｄｏｍａｉｎｃｏｎｖｏｌｕｔｉｏｎｏｆｉｎｄｉｖｉｄｕａｌＬａｐｌａｃｅｔｒａｎｓｆｏｒｍｓｏｆｔｗｏｓｉｇｎａｌｓ.Ｇｅｎｅｒａｌｌｙ,ｔｈｅｃｏｎｖｏｌｕｔｉｏｎｏｆｔｗｏｃｏｍｐｌｅｘｆｒｅｑｕｅｎｃｙ＿ｄｏｍａｉｎａｎａｌｙｔｉｃａｌｆｕｎｃｔｉｏｎｓｉｓｃａｌｃｕｌａｔｅ…     

Tip gap height effects on the aerodynamic performance of a cavity squealer tip in a turbine cascade in comparison with plane tip results: part 2—aerodynamic losses

Tip gap height effects on aerodynamic losses downstream of a cavity squealer tip have been investigated in a linear turbine cascade for power generation, in comparison with plane tip results. Three-dimensional flow fields are measured with a five-hole probe for tip gap height-to-chord ratios of h/c = 0.5, 1.0, 1.5 and 2.0%. The cavity squealer tip has a full length squealer with its rim height-to-chord ratio of 5.51%. For a fixed value of h/c, the tip leakage vortex for the cavity squealer tip is always weaker than that for the plane tip, and the flow field in the passage vortex region for the cavity squealer tip is less influenced by the tip leakage flow than that for the plane tip. For the cavity squealer tip, there is no appreciable change in local aerodynamic loss with h/c in the passage vortex region, but local aerodynamic loss in the tip leakage vortex region increases with h/c. The roles of the cavity squealer tip in reducing aerodynamic loss in comparison with the plane tip case are twofold: (1) the cavity squealer tip decreases the leakage flow discharge in the region from the leading edge to the mid-chord, which leads to an aerodynamic loss reduction in the passage vortex region and (2) it also decreases the leakage flow discharge downstream of the mid-chord, which results in an aerodynamic loss reduction in the tip leakage vortex region.     

The effects of surface injection through a perforated square cylinder on some aerodynamic parameters

The surface pressure distribution and the vortex shedding frequency were investigated for the flow around perforated horizontal and diagonal square cylinders with surface injection through various surfaces. For this purpose, surface pressure measurements on each square cylinder (horizontal and diagonal) and vortex shedding frequency measurements in the wake region were performed at three different Reynolds numbers in a wind tunnel. The parameters considered were injection coefficient, position of perforated surface (i.e., top, rear, top-rear and all), pressure coefficient, drag coefficient, and the Strouhal number. The results showed that pressure coefficient distribution, drag coefficient, and the Strouhal number were influenced by the position of the perforated surface and by the injection coefficient. The surface injections through the top-rear, rear and all surfaces of a diagonal square cylinder reduce the drag coefficient for the all Reynolds numbers, while the injection through all surfaces only reduces the drag coefficient of a horizontal square cylinder. The other aerodynamic parameter Strouhal number can also be controlled by injection through certain surfaces of a horizontal square cylinder.     

Effects of camberwise varying tip injection on loss and wake characteristics of a low pressure turbine blade

This paper presents the results of an experimental study that investigates the effects of camberwise varying tip injection on the total pressure loss and wake flow characteristics downstream of a row of Low Pressure Turbine (LPT) blades. This injection technique involves spanwise jets at the tip that are issued from a series of holes distributed along the camber line. The injection from each hole is individually and separately controlled using a computer driven solenoid valve and therefore the flow injection geometrical pattern at the tip can be adjusted to any desired variation. Three different injection cases are investigated including triangular, reversed triangular and uniform injection patterns. Here, triangular and reversed triangular cases refer to discrete blowing from the blade tip in which the blowing velocity increases (triangular) or decreases (reverse triangular) linearly from the leading to trailing edge along the camber. For uniform injection, the injection velocity is kept constant for all injection holes. The total mass injection from the tip is kept the same for all injection cases. The experiments are conducted in a continuous-flow wind tunnel with a linear cascade test section and measurements involve Kiel probe traverses 0.5 axial chords downstream of the blades covering a region between 85% and 100% span as well as two-dimensional Particle Image Velocimetry (PIV) measurements on 50%, 85% and 95% spanwise planes. For all injection cases, results show that tip injection reduces the total pressure loss levels in general. Highest measured overall loss reduction occurs in the case of reversed-triangular injection. The least effective waveform is observed to be triangular injection. There is significant reduction in the extent of the low momentum zone of the leakage vortex with injection. This effect is much less pronounced for the passage vortex. On the other hand, complex flow patterns are observed within the passage vortex, especially in the case of reversed-triangular injection, such as a possible embedded vortical structure along the passage vortex core, which creates double peaks in the velocity and turbulent kinetic energy fields.     

Oblique impingement of a circular jet in a cross flow

The distributions of temperature and dye concentration produced by a cross flow jet impinging on a flat surface are examined experimentally. Measurements show that for sufficiently high jet injection speeds, a ground vortex region upstream of the jet develops. The dimensionless gross geometrical features of this recirculating region are related by a simple linear law and are independent of the jet — surface spacing or the injection speed ratio.     

TOPOLOGY AND VORTEX STRUCTURES OF A CURVING TURBINE CASCADE WITH TIP CLEARANCE (Ⅱ)- TOPOLOGICAL FLOW PATTERN AND VORTEX STRUCTURE IN THE TRANSVERSE SECTION OF A BLADE CASCADE

By means of ink trace visualization of the flows in conventional straight, positively curved and negatively curved cascades with tip clearance, and measurement of the aerodynamic parameters in transverse section, and by appling topology theory, the topological structures and vortex structure in the transverse section of a blade cascade were analyzed. Compared with conventional straight cascade, blade positive curving eliminates the separation line of the upper passage vortex, and leads the secondary vortex to change from close separation to open separation, while blade negative curving effects merely the positions of singular points and the intensities and scales of vortex. Foundation items: 973 Project of China; the Doctoral Foundation of Education Ministry of China (EDAF24403003) Biography: YANG Qing-hai (1969−)     

On the transition process of a swirling vortex generated in a rotating tank

In this study, we investigate the transition of a swirling vortex from a one-celled to a two-celled vortex structure in a rotating tank. The main idea is to initiate the flow by siphoning fluid out of the tank and then to lift the siphoning mechanism out of the water within a short period of time. Before it reaches a state of quasi-two-dimensionality, the core region of the vortex can be roughly divided into three stages. (1) A siphoning stage induces the formation of the one-celled vortex. (2) A downward jet impingement stage triggers the transition of the vortex into the two-celled one. (3) A detachment stage of the inner cell leads to a cup-like recirculation zone, which is pushed upward by an axial flow from the boundary layer. This eventually develops into a stable quasi-two-dimensional barotropic vortex. The core region is enclosed by an outer region, which is in cyclostrophic balance. In the siphoning stage, the flow pattern can be well fitted by Burgers’ vortex model. However, in the post-siphoning stage, the present data show a flow pattern different from the existing two-celled models of Sullivan and Bellamy-Knights. Flow details, including flow patterns, velocity profiles, and surface depressions were measured and visualized by particle tracking velocimetry and the dye-injection method with various colors. The one-celled and two-celled flow structures are also similar to the conceptual images of the one- and two-celled tornadoes proposed in the literature. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

TOPOLOGY AND VORTEX STRUCTURES OF A CURVING TURBINE CASCADE WITH TIP CLEARANCE (Ⅰ)- EXPERIMENTAL MODEL AND TOPOLOGICAL FLOW PATTERNS ON BOTH ENDWALLS AND BLADE SURFACES

By means of ink trace visualization of the flows in conventional straight, positively curved and negatively curved cascades with tip clearance, and measurement of the aerodynamic parameters in the transverse section, and by appling topology theory, the structures on both endwalls and blade surfaces were analyzed. Compared with conventional straight cascade, blade positive curving eliminates the separation line of the upper passage vortex and leads the secondary vortex to change from close separation to open separation, while blade negative curving effects merely the positions of singular points and the intensities and scales of vortex. Foundation items: 973 Project of China; the Doctoral Foundation of Education Ministry of China (EDAF24403003) Biography: YANG Qing-hai (1969−)     

A typhoon-like vortex solution of incompressible 3D inviscid flow

This letter obtains a typhoon-like vortex solution by solving the Bragg-Hawthorne equation. The solution describes spiral paths of fluid material element on the Bernoulli surface, whereas some new exact solutions are obtained which are bounded in the whole region. The first one is a continued umbrella vortex solution, which is a typhoon-like vortex. The second one is a multi-planar solution, which is periodic in z-coordinate. Within each layer, there is an umbrella vortex solution similar to the first one. The above explicit solutions can be applied to the study of radial structure of typhoon. Both the solutions and the approaches used in the present work can also be applied to other complex flows.     

Evolution of an initially columnar vortex terminating normal to a no-slip wall

The early evolution of an initially columnar vortex normal to a solid wall was examined. The vortex was generated by a pair of flaps in a water tank. Detrimental effects from the wall during the vortex generation were avoided by producing the vortex normal to a free surface and subsequently bringing a horizontal plate into contact with the surface. Digital particle image velocimetry (DPIV) measurements of the velocity and vorticity, together with laser induced fluorescence (LIF) visualizations, in a meridional plane revealed a toroidal structure with the appearance of an axisymmetric vortex breakdown bubble. Agreement was found between the measurements and numerical simulations of the axisymmetric Navier–Stokes equations. The results show that the flow in the effusive corner region is dominated by a Bödewadt-type spatially oscillatory boundary layer within the core region and a potential-like vortex boundary layer at large radii. The toroidal structure results from the interaction between these two boundary layers, leading to the roll up of a dominant shear layer within the Bödewadt structure, and does not develop from the columnar vortex itself.     

Rankine combined vortex interaction with a rectangular prism

Large eddy simulation is utilised to study the three-dimensional interaction between a travelling Rankine combined vortex and a rectangular prism. The study examines the strength and the topology of a vortex during the interaction with a prism that is much wider than the vortex core diameter. The physics of the interaction is revealed for the straight (β = 0°) and the oblique (β = 45°) impacts. For both cases, the low-level portion of the vortex undergoes displacements in the streamwise and the lateral directions. Also the vortex shape and the core vorticity are substantially disrupted. Behind the prism the full vortex circulation is recovered after a considerable distance. This created a low-velocity region. The sheltering effect of the prism is noticed for both straight and oblique impacts. The flow velocities in the sheltering region, right behind the prism, are reduced by more than 42% compared to the maximum flow speeds before the interaction.