Visualization of Internal Flow Field of Propeller Fan

Propeller fans are required not only to have high performance but also to be extremely quiet. The internal flow field of ventilation propeller fans is even more complicated because they usually have a very peculiar configuration with protruding blades upstream. Thus, many kinds of internal vortices yield which cause noise and their cause and countermeasures are needed to be clarified. The purposes of this paper are to visualize the internal flow of the propeller fan from the static and rotating frame of reference. The internal flow visualization measured from the static frame gives approximately the scale of the tip vortex. The visualization from the rotating coordinate system yields a better understanding of the flow phenomena occurring at the specific blade. The experiment is implemented by using a small camera mounted on the shaft of the fan and rotated it to capture the behavior of the vortices using a laser light sheet to irradiate the blade surface. Hence, the flow field of the specific blade could be understood to some extent. The visualized results are compared with the CFD results and these results show a similar tendency about the generation point and developing process of the tip vortex. In addition, it is found that the noise measurement result is relevant to the effect of tip vortex from the visualization result.

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Studies of Reynolds Number Effects on Wing Tip Vortex Positions by Means of Laser Light Sheet (LLS) and Background Oriented Schlieren (BOS) Technique Under Cryogenic Conditions

Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM) - New Results in Numerical and Experimental Fluid Mechanics VI ◽

10.1007/978-3-540-74460-3_13 ◽

2007 ◽

pp. 104-112 ◽

Cited By ~ 1

Author(s):

D. Pallek ◽

F. Klinge

Keyword(s):

Reynolds Number ◽

Laser Light ◽

Light Sheet ◽

Tip Vortex ◽

Laser Light Sheet ◽

Reynolds Number Effects ◽

Background Oriented Schlieren ◽

Wing Tip Vortex ◽

Wing Tip ◽

Cryogenic Conditions

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Influence of wall roughness on cavitation performance of centrifugal pump

Journal of the Brazilian Society of Mechanical Sciences and Engineering ◽

10.1007/s40430-021-03023-3 ◽

2021 ◽

Vol 43 (6) ◽

Author(s):

Weihui Xu ◽

Xiaoke He ◽

Xiao Hou ◽

Zhihao Huang ◽

Weishu Wang

Keyword(s):

Flow Field ◽

Centrifugal Pump ◽

Internal Flow ◽

Wall Roughness ◽

Blade Surface ◽

Centrifugal Pumps ◽

Three Dimensional Model ◽

Cavitation Inception ◽

Cavitation Performance ◽

Critical Cavitation

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

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Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/99-gt-198 ◽

1999 ◽

Author(s):

Dieter E. Bohn ◽

Karsten A. Kusterer

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Gas Turbines ◽

Leading Edge ◽

Suction Side ◽

Pressure Side ◽

Blade Surface ◽

Cooling Fluid ◽

Flow Phenomena ◽

Vortex Systems

A leading edge cooling configuration is investigated numerically by application of a 3-D conjugate fluid flow and heat transfer solver, CHT-Flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multi-block technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row is on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45°. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical domain includes the internal cooling fluid supply, the radially inclined holes and the complete external flow field of the turbine vane in a high resolution grid. Periodic boundary conditions have been used in the radial direction. Thus, end wall effects have been excluded. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three dimensional and asymmetric jet flow field. Within a secondary flow analysis it can be shown that complex vortex systems are formed in the ejection holes and in the cooling fluid jets. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a good agreement concerning the vortex development. The phenomena on the suction side and the pressure side are principally the same. It can be found that the jets are barely touching the blade surface as the dominating vortex transports hot gas under the jets. Thus, the cooling efficiency is reduced.

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Research on CFD Simulation of the Cement Slurry Mixer

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.621.196 ◽

2012 ◽

Vol 621 ◽

pp. 196-199

Author(s):

Shui Ping LI ◽

Ya Li Yuan ◽

Lu Gang Shi

Keyword(s):

Flow Field ◽

High Performance ◽

Cfd Simulation ◽

Structural Parameters ◽

Internal Flow ◽

Simulation Method ◽

Cement Slurry ◽

Fluid Machinery ◽

Computational Fluid Dynamics Cfd ◽

Machinery Design

Numerical simulation method of the internal flow field of fluid machinery has become an important technology in the study of fluid machinery design. In order to obtain a high-performance cement slurry mixer, computational fluid dynamics (CFD) techniques are used to simulate the flow field in the mixer, and the simulation results are studied. According to the analysis results, the structural parameters of the mixer are modified. The results show the mixer under the revised parameters meet the design requirements well. So CFD analysis method can shorten design period and provide valuable theoretical guidance for the design of fluid machinery.

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Locomotion in scombrid fishes: visualization of flow around the caudal peduncle and finlets of the chub mackerel Scomber japonicus

Journal of Experimental Biology ◽

10.1242/jeb.204.13.2251 ◽

2001 ◽

Vol 204 (13) ◽

pp. 2251-2263 ◽

Cited By ~ 9

Author(s):

Jennifer C. Nauen ◽

George V. Lauder

Keyword(s):

Laser Light ◽

Light Sheet ◽

Flow Speed ◽

The Body ◽

Scomber Japonicus ◽

Laser Light Sheet ◽

Chub Mackerel ◽

Caudal Peduncle ◽

Local Flow ◽

Scombrid Fishes

SUMMARY Scombrid fishes are known for high-performance locomotion; however, few data are available on scombrid locomotor hydrodynamics. In this paper, we present flow visualization data on patterns of water movement over the caudal peduncle and finlets (small fins on the dorsal and ventral body margin anterior to the caudal fin). Chub mackerel, Scomber japonicus, ranging in fork length from 20 to 26 cm, swam steadily at 1.2forklengthss−1 in a recirculating flow tank. Small, reflective particles in the flow tank were illuminated by a vertical (xy) or horizontal (xz) laser light sheet. Patterns of flow in the region near the caudal peduncle were measured using digital particle image velocimetry. Patterns of flow along the peduncle and finlets were quantified using manual particle tracking; more than 800 particles were tracked for at least 12ms over a series of tailbeats from each of four fish. In the vertical plane, flow trajectory and flow speed were independent of the position of the finlets, indicating that the finlets did not redirect flow or affect flow speed. Along, above and below the trailing surface of the peduncle, where the finlets were oriented along the peduncular surface, flow was convergent. Along, above and below the leading surface of the peduncle, where the finlets were absent, the flow trajectory was effectively horizontal. The lack of divergent flow on the leading surface of the peduncle is consistent with cross-peduncular flow formed by the lateral motion of the peduncle interacting with convergent flow resulting from forward movement of the body. In the horizontal plane, particles illuminated by the xz light sheet situated approximately 3 mm below the ventral body surface were tracked within the laser light sheet for up to 40ms, indicating strong planar flow. As the peduncle decelerates, the most posterior finlet is frequently at an angle of attack of at least 20° to the incident flow, but this orientation does not result in thrust production from lift generation. Finlet 5 does redirect cross-peduncular flow and probably generates small vortices undetectable in this study. These data are the first direct demonstration that the finlets have a hydrodynamic effect on local flow during steady swimming.

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