Measurement of Wake Flow Fields, Including Reverse Flow, of Scale Vehicle Models Using a New 13-Hole Pitot Tube

1996 ◽  
Author(s):  
Ichiro Yamaguchi ◽  
Michitoshi Takagi ◽  
Kazuyuki Kurishima ◽  
Toshiya Mori
Keyword(s):  
Reverse Flow ◽  
Flow Fields ◽  
Pitot Tube ◽  
Wake Flow

scholarly journals Study of Internal Flows in a Mixed-Flow Pump Impeller at Various Tip Clearances Using 3D Viscous Flow Computations

1990 ◽  
Author(s):  
Akira Goto
Keyword(s):  
Reverse Flow ◽  
Three Dimensional ◽  
Interaction Mechanism ◽  
Secondary Flows ◽  
Wake Flow ◽  
Navier Stokes ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Pump Impeller ◽  
Flow Pump

The complex three-dimensional flow fields in a mixed-flow pump impeller are investigated by applying the incompressible version of the Dawes’ 3D Navier-Stokes code. The applicability of the code is confirmed by comparison of computations with a variety of experimentally measured jet-wake flow patterns and overall performances at four different tip clearances including the shrouded case. Based on the computations, the interaction mechanism of secondary flows and the formation of jet-wake flow are discussed. In the case of large tip clearances, the reverse flow caused by tip leakage flow is considered to be the reason for the thickening of the casing boundary layer followed by the deterioration of the whole flow field.

Analysis of the Flow in Vaneless Diffusers With Large Width-to-Radius Ratios

1996 ◽  
Author(s):  
Hua-Shu Dou ◽  
Shimpei Mizuki
Keyword(s):  
Boundary Layer ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Flow Region ◽  
Rotating Stall ◽  
Wake Flow ◽  
Layer Versus ◽  
Dimensional Boundary ◽  
Vaneless Diffusers ◽  
Large Width

The flow in vaneless diffusers with large width-to-radius ratios is analyzed by using three-dimensional boundary-layer theory. The variations of the wall shear angle in the layer and the separation radius of the turbulent boundary layer versus various parameters are calculated and compared with experimental data. The effect of the separation point on the performance of vaneless diffusers and the mechanism of rotating stall are discussed. It is concluded that when the flow rate becomes very low, the reverse flow zone on the diffuser walls extends toward the entry region of diffusers. When the rotating jet-wake flow with varying total pressure passes through the reverse flow region near the impeller outlet, rotating stall is generated. The influences of the radius ratio on the reverse flow occurrence as well as on the overall performance are also discussed.

Tomographic PIV investigation on 3D wake structures for flow over a wall-mounted short cylinder

2017 ◽  
Vol 831 ◽  
pp. 743-778 ◽  
Author(s):  
Hang-Yu Zhu ◽  
Cheng-Yue Wang ◽  
Hong-Ping Wang ◽  
Jin-Jun Wang
Keyword(s):  
Aspect Ratio ◽  
Circular Cylinder ◽  
Dynamic Characteristics ◽  
Large Scale ◽  
Low Frequency ◽  
Streamwise Vortex ◽  
Flow Fields ◽  
Vortex Structures ◽  
Wake Flow ◽  
Wake Field

Tomographic particle image velocimetry (TPIV) measurement with six high-resolution charge-coupled device (CCD) cameras is conducted to investigate flow structures over a finite circular cylinder with an aspect ratio of 2 ($h/d=2$). This short wall-mounted cylinder is fully immersed in a thick turbulent boundary layer ($\unicode[STIX]{x1D6FF}/h=1.025$). Focus is placed on the three-dimensional instantaneous vortex structures and their dynamic characteristics in the wake flow fields. Based on the present results, a refined topological model of the mean wake field behind the finite circular cylinder is proposed, where the spatial locations of the typical vortex structures and their interactions are described in more detail. Among the reported typical vortex structures (i.e. the horseshoe, tip, base, trailing and arch vortex), emphasis is laid on discussion of the tip and arch vortex. The instantaneous 3D M-shape arch vortex and an alternating large-scale streamwise vortex are first found in the present experiment, and their developments are also discussed. Therefore, it is suggested that the instantaneous finite-cylinder wake is dominated by the arch vortex system and the large-scale streamwise vortices. Moreover, in the instantaneous volumetric flow fields, both the antisymmetric and the symmetric wake behaviours are observed. With proper orthogonal decomposition (POD) analysis, the dynamic characteristics of the wake field are clarified. Different from the flow around an infinite cylinder without control, the third and fourth POD modes are characterized by low-frequency symmetric shedding. The low-frequency feature shown in the second mode pair is observed and associated with the occurrence of instantaneous symmetric 3D wake behaviour triggered by the low-aspect-ratio effect and the extension of the separated shear layer. The low frequency seems be attributed to the flapping phenomenon, i.e. oscillation of the recirculation in the backward-facing step flow. It is found that the flapping motion has a modulating effect on the occurrence of the antisymmetric shedding vortex and thus the large-scale streamwise vortex.

Aerodynamic instabilities modeling under asymmetric boundary in a centrifugal compressor for turbocharger

2022 ◽  
pp. 095440702110726
Author(s):  
Chenxing Hu ◽  
Xue Li ◽  
Siyu Zheng
Keyword(s):  
Boundary Conditions ◽  
Centrifugal Compressor ◽  
Reverse Flow ◽  
Pressure Ratio ◽  
Safety Margin ◽  
Wake Flow ◽  
Wave Number ◽  
Vaneless Diffuser ◽  
The Impact ◽  
Continuous Adjoint

The increasing demand for compression systems with high pressure ratio and wide safety margin has set new prerequisites for designers to meet the industrial needs without increasing the manufacturing costs excessively. In this work, the turbulent stability of the vaneless diffuser of the centrifugal compressor was analyzed. Unsteady Reynolds-averaged numerical simulations of the isolated diffuser and full annular diffuser with or without circumferential asymmetric boundary conditions downstream were performed. And a continuous adjoint approach was adopted, which is rarely applied in the stability analysis of compressor flow. Then, the origin of instability under different inflow and outflow conditions was sought with a sensitivity analysis. The prediction of the growth rate reveals that the flow near the shroud dominates the global stability of the diffuser. When connected with an impeller in the upstream direction, the most unstable region is localized at the backflow regions near the outlet. The wave number, however, is altered under the impact of the jet-wake flow. When connected to a circumferential asymmetric condition, the structural sensitivity of the vaneless diffuser with a radius ratio of 1.53 indicates that the interaction between the inlet reverse flow and outlet backflow is responsible for the occurrence of stall. The most unstable regions are localized at the region 90°–135° away from the volute tongue. The present work mainly contributes to the instabilities identification with novel sensitivity methods under asymmetric boundary conditions.

Influence of Oscillating Boundary Layer Suction on Aerodynamic Performance in Highly-Loaded Compressor Cascades

2018 ◽  
Author(s):  
Xu Hao ◽  
Liu Bao ◽  
Cai Le ◽  
Zhou Xun ◽  
Wang Songtao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vortex Shedding ◽  
Large Scale ◽  
Reverse Flow ◽  
Separation Bubble ◽  
Flow Region ◽  
Flow Fields ◽  
Separation Flow ◽  
Oscillating Boundary ◽  
Pod Analysis

Vortex structures of the separation flow fields in compressor cascades controlled by the boundary layer oscillating suction (BLOS) are numerically investigated. The proper orthogonal decomposition (POD) method is adopted to present the variation of characteristics owned by large-scale vortices. It is found that unsteady perturbation re-organizes the aspirated flow fields and, if in a proper situation, reduces the loss furthermore. Through POD analysis, variations of vortical structures are described. The results turn out that the periodic perturbation leads to a vortex shedding process with the same frequency as the excitation. The reason of loss reduction could be summarized by actuated vortices enhancing the momentum of the stagnated fluid in the reverse flow region as well as decreasing the frequencies of vortex shedding. Finally, 3-D numerical results turn out that the oscillation can transform the stable corner separation bubble to vortex rings shedding downstream and hence improve cascade performance.

Near-Wake Flow of a V-Gutter With Slit Bleed (Data Bank Contribution)

1993 ◽  
Vol 115 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Jing-Tang Yang ◽  
Go-Long Tsai
Keyword(s):  
Reverse Flow ◽  
Reynolds Shear Stress ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Data Bank ◽  
Wake Flow ◽  
Near Wake ◽  
Cold Flow ◽  
Flame Holder ◽  
Flow Through

The cold-flow characteristics of a v-shape flame holder with flow bleed from a slit located at the leading edge have been investigated. According to experimental evidence, a nonsymmetric wake structure is developed behind the symmetric slit v-gutter. The flow through the slit induces greater reverse flow and greater back pressure in the near wake. It also provokes more extensive transport across the shear layers and reduces both the turbulent intensity and the Reynolds shear stress of the wake flow. These results indicate that the slit v-gutter can have a better flame holding ability and less pressure loss compared with the traditional v-gutter. In view of fluid dynamics features, the slit v-gutter is indeed a potentially useful design of flame holder.

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