Internal flow effect on the cross-flow vortex-induced vibration of a cantilevered pipe discharging fluid

This paper presents a qualitative analysis of controlling the cross-flow fan noise by using porous stabilizers. The stabilizer was originally a folded plate. It is changed into a porous structure which has a plenum chamber and vent holes on the front wall. In order to investigate the influences of using the porous stabilizers, experiments are carried out to measure the cross-flow fan aerodynamic performances and sound radiation. Meanwhile, the internal flow field of the fan is numerically simulated. The results show that the porous stabilizers have not produced considerable effect on the cross-flow fan's performance curve, but the noise radiated from the fan is strongly affected. This indicates the feasibility of controlling the cross-flow fan noise by using the porous stabilizers with selected porosity.

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Secondary instability of cross-flow vortices in Falkner–Skan–Cooke boundary layers

Journal of Fluid Mechanics ◽

10.1017/s0022112098001931 ◽

1998 ◽

Vol 368 ◽

pp. 339-357 ◽

Cited By ~ 63

Author(s):

MARKUS HÖGBERG ◽

DAN HENNINGSON

Keyword(s):

Growth Rate ◽

Shear Layer ◽

Boundary Layers ◽

Growth Rates ◽

High Frequency ◽

Cross Flow ◽

Low Frequency ◽

Secondary Instability ◽

The Cross ◽

Flow Vortex

Linear eigenvalue calculations and spatial direct numerical simulations (DNS) of disturbance growth in Falkner–Skan–Cooke (FSC) boundary layers have been performed. The growth rates of the small-amplitude disturbances obtained from the DNS calculations show differences compared to linear local theory, i.e. non-parallel effects are present. With higher amplitude initial disturbances in the DNS calculations, saturated cross-flow vortices are obtained. In these vortices strong shear layers appear. When a small random disturbance is added to a saturated cross-flow vortex, a low-frequency mode is found located at the bottom shear layer of the cross-flow vortex and a high-frequency secondary instability is found at the upper shear layer of the cross-flow vortex. The growth rates of the secondary instabilities are found from detailed analysis of simulations of single-frequency disturbances. The low-frequency disturbance is amplified throughout the domain, but with a lower growth rate than the high-frequency disturbance, which is amplified only once the cross-flow vortices have started to saturate. The high-frequency disturbance has a growth rate that is considerably higher than the growth rates for the primary instabilities, and it is conjectured that the onset of the high-frequency instability is well correlated with the start of transition.

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On Vortex Induced Vibration in Two-Degree-of-Freedoms of Flexible Cylinders

Volume 4: Pipeline and Riser Technology ◽

10.1115/omae2011-49698 ◽

2011 ◽

Author(s):

Weiping Huang ◽

Weihong Yu

Keyword(s):

Natural Frequency ◽

Current Velocity ◽

Coupling Effect ◽

Great Influence ◽

Cross Flow ◽

Flexible Cylinder ◽

Fluid Structure ◽

Vortex Induced Vibration ◽

Flow Vortex ◽

Lock In

In this paper, an experimental study on the in-line and cross-flow vortex-induced vibration (VIV) of flexible cylinders is conducted. The relationship of two-degree-of-freedoms of vortex-induced vibration of flexible cylinders is also investigated. The influence of natural frequency of flexible cylinders on vortex shedding and VIV are studied through the experiment in this paper. Finally, A nonlinear model, with fluid-structure interaction, of two-degree-of-freedom VIV of flexible cylinders is proposed. It is shown that the ratio of the frequencies and amplitudes of in-line and cross flow VIV of the flexible cylinders changes with current velocity and Reynolds number. The natural frequency of flexible cylinder has great influence on the vortex-induced virbation due to the strong fluid-structure coupling effect. Under given current velocity, the natural frequency of flexible cylinder determines its forms of vibration (in circular or ‘8’ form). The ratio of the VIV frequencies is 1.0 beyond the lock in district and 2.0 within the lock in district respectively. And the ratio of the VIV amplitudes is 1.0 beyond the lock in district and 1/3 to 2/3 within the lock in district. The results from this paper indicates that in-line vibration should be considerated when calculating the vibration response and fatigue damage.

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Model Testing on Cross-Flow Vortex-Induced Vibration in Combined In-Line Current and Oscillatory Flows

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 6 ◽

10.1115/omae2010-20934 ◽

2010 ◽

Author(s):

Franc¸ois Moreau ◽

Shan Huang

Keyword(s):

Reynolds Number ◽

Current Flow ◽

Velocity Ratio ◽

Cross Flow ◽

Test Results ◽

Oscillatory Flows ◽

Vortex Induced Vibration ◽

Towing Tank ◽

Towing Speed ◽

Flow Vortex

The cross-flow vibration of a cylinder in co-linear steady and oscillatory flows is investigated in towing tank for the inline Keulegan Carpenter number varying from 5 to 27 and for the reduced velocity varying from 3 to 19. The reduced velocity is defined by adding together the towing speed and the maximum in-line oscillating velocity. The ratio between the maximum in-line oscillating velocity and the total in-line velocity, i.e. including the towing speed, varies from 0.1 to 0.8. The Reynolds number is in the sub-critical regime. The model test results show that cross-flow vortex-induced vibration (VIV) in combined wave and current flow is significantly different from that in current or wave alone. The response is very much dependent upon the velocity ratio between the current and wave particle velocity.

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Cross-flow vortex-induced vibration reduction of a long flexible cylinder using 3 and 4 control rods with different configurations

Applied Ocean Research ◽

10.1016/j.apor.2019.101900 ◽

2019 ◽

Vol 91 ◽

pp. 101900 ◽

Cited By ~ 4

Author(s):

Yan Lu ◽

Yangyang Liao ◽

Bin Liu ◽

Wanhai Xu

Keyword(s):

Vibration Reduction ◽

Cross Flow ◽

Flexible Cylinder ◽

Vortex Induced Vibration ◽

Flow Vortex ◽

Control Rods

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Simulation of Cross-Flow Vortex-Induced Vibration of Single Tube Based on Two-Way Fluid-Solid Interaction Method

Volume 8: Computational Fluid Dynamics (CFD) and Coupled Codes; Nuclear Education, Public Acceptance and Related Issues ◽

10.1115/icone25-66955 ◽

2017 ◽

Author(s):

Wang Zengzeng ◽

Lu Tao ◽

Liu Bo

Keyword(s):

Nuclear Fuel ◽

Vortex Shedding ◽

Vibration Frequency ◽

Cross Flow ◽

Time History ◽

Pressurized Water ◽

Vortex Induced Vibration ◽

The Cross ◽

Control Equation ◽

Fluid Solid Interaction

The fatigue damage and lift force caused by vortex induced vibration occur very often in the core of the Pressurized Water Reactor (PWR) [1] It is extremely complex to illustrate the mechanism of vibration which induced by Cross-flow. With the spacer grids and wings, the flow direction which in axial direction at the inlet will change and create swirls, so there are many flow directions in the nuclear fuel component. Assumed the tube endure cross-flow only in this article to simplify the fluid model. Most researchers in this field often ignore the displacement of structure induced by the cross flow because the value is so small that not enough to change the fluid region. In truth conditions, the motion of the cylinder caused the wake oscillation and strengthen the vortex shedding, in turn, the vortex shedding will aggravate the vibration amplitude. According that, one way FSI (Fluid Solid Interaction) can’t capture the influence from the cylinder vibration. In this article, Two-way FSI method was executed to get the vibration in time history in order to get the random vibration induced by the cross flow more close to the actual project. Using Finite Volume Method to discrete the fluid control equation and finite element method to discrete structure control equation combined with moving mesh technology. An interface between the fluid region and the structure region was created to transfer the fluid force and the structure displacement. Coupling CFD code and CSD (Computational Solid Dynamics) code to solve the differential equation and obtain the displacement of the cylinder in time history. A Fast Fourier Transfer (FFT) has been done to get the vibration frequency. An Analysis of the vortex shedding frequency and vibration frequency to find the correlation between the vortex shedding and the vibration frequency has been done. A modal analysis for the cylinder without water has been done to get the natural frequency. Results shows the cylinder has different response to the vortex shedding at different position of the cylinder in the same condition. There are more works need to be done aim to get the vibration mechanism in tandem tube and parallel tube to get clearly mechanism of vortex induced vibration in nuclear fuel assembly. The research of the vortex induced vibration in this article is a key to get on the follow research in more tubes array in different methods.

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Study on Performance and Internal Flow of Cross-Flow Wind Turbine

Volume 2: Symposia, Parts A, B, and C ◽

10.1115/fedsm2003-45101 ◽

2003 ◽

Author(s):

Kazuki Takeuchi ◽

Junichiro Fukutomi ◽

Hidetoshi Kodani ◽

Hironori Horiguchi

Keyword(s):

Wind Turbine ◽

Pressure Difference ◽

Main Part ◽

Cross Flow ◽

Internal Flow ◽

Power Coefficient ◽

Construction Costs ◽

Outer Flow ◽

Output Coefficient ◽

The Cross

The wind turbine has become more popular in recent years, but on the other hand, the developments of small wind-turbine have been legging behind. Because, the energy density of wind is small, since the efficiency of the main part of a wind turbine is very low. The construction costs become comparatively high-priced. Then, the main part of this subject is to show that, by collecting and sucking out more winds, a wind turbine is made to pass many winds and the new cross-flow wind turbine that increases an output coefficient is proposed. The cross-flow wind turbine has high torque and low speed characteristics and the structure are very simple. So, it can be used in a large wind velocity region. However, even if the power coefficient is high, it is about 10%. The purpose of this paper is to show how we can improve the power coefficient by applying a casing, which has a nozzle and a diffuser. This research was made to clear up fundamental characteristics of the interaction between outer flow and inner flow. Three kinds of cross-flow wind turbines were designed. The nozzle and diffuser have been designed suitable for the performance of wind turbine. The flow simulations by CFD have been carried out for various types of casings at 20 m/s with Fluent Ver5.0. All Wind tunnel experiments were performed at 20m/s. The case of casing 2, which have plate arranged near the separation point of cylinder, also experimented. The rotor that is settled in the casing 1 shows a larger power coefficient than the case without a casing. The casing of the cross-flow turbine makes a pressure difference between inflow and outflow. The pressure difference increases the mass flow rate. Therefore much more wind passes through into the cross-flow turbine. In this experiment, the power coefficient increased 1.5 times in the case with casing. A still higher output coefficient could be obtained in the case where it is shown by the casing 2.

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Internal Flow Characteristics of Cross-Flow Hydraulic Turbine With the Variation of Nozzle Shape

Volume 2: Fora, Parts A and B ◽

10.1115/fedsm2007-37541 ◽

2007 ◽

Cited By ~ 2

Author(s):

Young-Do Choi ◽

Jea-Ik Lim ◽

You-Taek Kim ◽

Young-Ho Lee

Keyword(s):

Flow Characteristics ◽

Cross Flow ◽

Internal Flow ◽

Close Relation ◽

Hydraulic Turbine ◽

Impulse Turbine ◽

Runner Blade ◽

Turbine Performance ◽

Nozzle Shape ◽

The Cross

The purpose of this study is to examine the optimum configuration of nozzle shape to further optimize the cross-flow hydraulic turbine structure and improve the performance. The results show that CFD analysis for the cross-flow turbine can be adopted as a useful method to examine the internal flow and turbine performance in detail. Pressure on the runner blade in Stage 1 and velocity at nozzle outlet have close relation to the turbine performance. The performance characteristics of cross-flow turbine have both impulse turbine and reaction turbine simultaneously.

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