A large-scale perpendicular cavitating vortices (PCVs), at the trailing edge of attached cavitation on the blade suction side near the tip region, has been found recently due to the great impact on performance breakdown in an axial waterjet pump. However, the trajectory and dynamics of this structure have been given scant attention. In this study, some visualized experiments were carried out to elucidate the PCVs for different conditions. The high-speed imaging coupled with numerical computations show that the vortical cloud cavitation is induced by the combination of tip leakage vortex (TLV) and radial re-entrant jets from the hub to blade tip. Moreover, the trajectory and intensity of PCVs depend on the operating conditions strongly, whether the other parameters, e.g. blade number and blade geometries, are modified. When taken the blade number into consideration, as a consequence of flow passage width and blade loading distributions, the dynamics and strength of PCVs vary considerably. Furthermore, an optimum clearance geometry is seen to eliminate corner vortex and clearance cavitation when the clearance edge is rounded on the pressure side. However, the more intensive tip leakage vortex cavitation is observed due to the increased amount of leakage flux. Additionally, in the original blade with sharp edges, the PCVs is relative weak and has a loose structure, resulting in the multiple interaction with the next blade. These phenomenon are responsible for the severe performance degradation and flow instabilities in the tip region of an axial-flow pump.

Complex fluids refer to those with internal microstructures whose evolution affects the macroscopic dynamics of the material, especially the rheology [7]. Examples include polymer solutions and melts, liquid crystals, gels and micellar solutions. Such materials often have great practical utilities since the microstructure can be manipulated via processing flow to produce outstanding mechanical, optical or thermal properties. A good example is main-chain liquid-crystalline polymers (LCPs). Their molecular backbone is rodlike, with a degree of rigidity, such that the polymer assumes an anisotropic orientational order due to spontaneous alignment of the molecules. This order, further enhanced by extensional flows, leads to exceedingly high strength and modulus in the Kevlar fiber, a commercially successful product of du Pont. An important way of utilizing complex fluids is through composites. By blending two immiscible components together, one may derive novel or enhanced properties from the composite, and this is often a more economical route to new materials than synthesis. Moreover, the properties of composites may be tuned to suit a particular application by varying the composition, concentration and, most importantly, the interfacial morphology. Take polymer blends for example [11]. Under optimal processing conditions, the dispersed phase is stretched from drops into a fibrillar morphology. Upon solidification, the long fibers act as in situ reinforcement and impart great strength to the composite. The effect is particularly strong if the fibrillar phase is liquid crystalline [2]. The dispersed phase may also be solid as in colloidal dispersions, or gas as in thermoplastic foams. From a scientific viewpoint, the essential physics in all such composites is the coupling between interfacial dynamics and complex rheology of the components. Despite their practical importance, our current knowledge of two-phase complex fluids is very limited. The main difficulty is that these materials have a myriad of internal boundaries, which move, deform, break up and reconnect during processing. This leads to a seemingly intractable mathematical problem, and also hampers experimental observation and measurement. A secondary difficulty is that the rheology of each component alone is highly complex, with the internal microstructure coupled with the flow field. Thus, these materials feature dynamic coupling of three disparate length scales: molecular conformation inside each component, mesoscopic interfacial morphology and macroscopic hydrodynamics. An understanding of the interfacial dynamics in complex fluids is a major fundamental challenge as well as a significant practical need. The problem involves several traditional disciplines: mathematical modeling, numerical computation, soft-matter physics, fluid mechanics, material science and engineering. An objective of the workshop is to explore new research directions in the context of multi-disciplinary interactions.

A three-dimensional lattice Boltzmann method based on the Uehling-Uhlenbeck Boltzmann-BGK equation is presented. The method is directly derived by projecting the kinetic governing equation onto the tensor Hermite polynomials and various hydrodynamic approximation orders can be achieved. The intrinsic discrete nodes of the three-dimensional Gauss-Hermite quadrature provide the natural lattice velocities for the semiclassical lattice Boltzmann method. Simulations of the lid-driven cubic cavity flows based on D3Q19 lattice model for several Reynolds numbers and different particle statistics are shown to illustrate the method. The results indicate distinct characteristics of the effects of quantum statistics.

An incompressible turbulent planar mixing layer is composed of two different flow types in its flow field, namely a shear layer in the central region and two free streams in each outer high- and low-speed sides. Shear layer is formed right after the trailing edge of the splitter plate and develops stream-wisely through successively distinct regions, namely the near field region and the self-preserving region. A new definition of the mixing length (lω) is proposed on the basis of an effectively pure shear-induced vorticity component (ΩSH) by means of a triple decomposition method, that is, lω = yH - yL where yH and yL are the two transverse positions, at which |ΩSH| normalized with the maximum ∂U/∂y at the virtual origin is equal to 0.05, in the high- and low-speed free stream sides, respectively. It is shown that the linear growth rate of lω along stream-wise distance can be, then, used as one of the necessary and sufficient conditions for identifying the achievement of the self-preserving state in turbulent mixing layer.

As there are frequent needs to install a micro wind turbine generator in a residential area, we have developed such a downwind-type turbine rotor having the following specifications: The rotor has the tip diameter of 1.5 m and three two-dimensional NACA0018 blades of 0.15 m chord whose material is light, soft and pliable foam plastic for perfect safety. From the wind tunnel test under the wind speed less than 14 m/s, it is clarified that the downwind turbine generator having soft blades has the low noise and the self-output-control characteristics, which are regarded as favorable for its actual operation. The latter feature is primarily attributed to bending and torsional elastic-deformation of the soft blade. The remarkable aerodynamic performances are summarized in this paper.

Flows around vortex generators (VGs), which serve as one of the important flow control methods, are investigated by solving Reynolds-Averaged Navier-Stokes (RANS) equations. The influences on the main flow of VGs are intended to explore. To validate computational schemes, the flow around a single VG on a flat plane is computed to acquire basic knowledge of this kind of flow. Then transonic flow past a standard model, named by ONERA-M6 wing, is predicted to investigate the flow features of shockwave/boundary-layer interactions (SWBLI). Investigation is focused on a supercritical wing. Firstly, the effects of a row of VGs on the airfoil with the same cross-section design are calculated with periodical boundaries in transonic conditions. Then, VGs on the whole supercritical wing are analyzed with strong SWBLI. Lastly, VGs are mounted more upwind (about 3.5% local chord) to explore the effects at low speed and high incidence condition. The numerical results show that seven VGs on the wing can effectively suppress the separations behind the strong SWBLI and decrease spanwise flow and wing-tip vortex in transonic condition. VGs can also decrease the large scope of separation over the wing at low speed with high angle of attack.

This study employs a digital Particle Image Velocimetry (PIV) to obtain detailed velocity distributions and flow visualization for an inclined jet through a forward expanded hole into mainstream over a concave surface at three different blowing ratios (M) of 0.5, 1.0, and 1.5. In this study, measurements are made in three different cases to identify the interaction between the ejected flow and the mainstream. These three cases are particles seeded in the ejected flow only, particles seeded in the mainstream only, and particles seeded in both the ejected flow and the mainstream. Measured results show that the blowing ratio can significantly affect the flow field of an ejected flow into the mainstream. From the 2D velocity measurement on the central plane of the injection hole at M=1.0, measured results show that a strong interaction occurs between the ejected flow and the mainstream at the leeward side of the ejected jet. In this region, the mainstream is entrained into the center plane that produces an outward radial velocity to lift the ejected flow away from the concave wall. In this study, there is no obvious radial velocity of the jet flow to up-lift itself on the central plane. The decay of the lift-off velocity from the mainstream along the streamwise direction is a cause for reattachment of a jet flow on the concave surface.