Effect of sinusoidal vertical gust on the pressure distributions on and flow structures around a rectangular cylinder

2021 ◽  
Vol 62 (7) ◽  
Author(s):  
Ming Li ◽  
Qiusheng Li ◽  
Haoyun Shi
Keyword(s):  
Flow Structures ◽  
Pressure Distributions ◽  
Rectangular Cylinder

Fluid Flow Structures in Staggered Banks of Cylinders Located in a Channel

1995 ◽  
Vol 117 (1) ◽  
pp. 36-44 ◽  
Author(s):  
M. J. Braun ◽  
V. V. Kudriavtsev
Keyword(s):  
Fluid Flow ◽  
Numerical Experiments ◽  
Reynolds Numbers ◽  
Flow Structures ◽  
Wall Jet ◽  
Square Channel ◽  
Pressure Distributions ◽  
Geometric Configurations ◽  
Model Fluid ◽  
Flow Through

This paper contains numerical experiments that model fluid flow through a staggered array of cylinders and represents a continuation of work previously performed by the authors (Braun et al., 1993; Kudriavstsev et al., 1993). The results shown here concentrate on the analysis of the physics of flow and pressure distribution in (i) one row of cylinders, and (ii) seven rows of cylinders. The test section is the same square channel described by Braun et al. (1993). The numerical experiments were run in transient mode at Reynolds numbers (Re = umaxd/v) ranging from 86 to 869. The primary purpose of this paper is to report qualitative results regarding the attached near-wall jet phenomenon and to discuss its flow mechanics. The authors compare various stages of the transient evolution of the flow structures for geometric configurations that contain one, and seven rows of pins respectively. The associated pressure distributions in the arrays of pins are also discussed.

Simulation on Performances of Vertical Axis Wind Turbine

2010 ◽  
Author(s):  
Chien-Chang Chen ◽  
Cheng-Hsiung Kuo
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Vertical Axis ◽  
Flow Structures ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent ◽  
Moment Coefficient ◽  
Pressure Distributions ◽  
The Moment ◽  
Starting Torque

This study employs the commercialized computational fluid dynamics software (Ansys/Fluent), with the user’s defined technique, to simulate the unsteady flow structures around the small-size vertical axis wind turbines (VAWT) with three straight blades. This study addresses the effects of the collective variations of the pitch angle (within ± 10°) on the performance of the VAWT system. The results of the transient (acceleration) stage will be employed to evaluate the self-starting ability. While the vertical axis wind turbine (VAWT) reaches a steady rotating stage, the detailed flow structures, the vorticity fields, the pressure distributions around, and the forces on the airfoils at various azimuthal positions will be addressed. For the blades with a negative pitch angle (θ = −10°), has the peak value of the moment coefficient within one revolution is the largest which will provide the largest starting torque to drive the VAWT system more easily. However, in this case, the moment coefficients are negative within some part of the period. This cancels part of the positive moment within one revolution, thus the efficiency is reduced at this pitch angle. For the case with positive pitch angle (θ = 10°), the area under the moment coefficient curve is the smallest and the time elapse of large moment coefficient is relatively short. Thus the efficiency and the starting torque are the lowest among thee pitch angles.

scholarly journals Wind effect on staggered cylinders of square and rectangular sections with variable longitudinal spacings

1970 ◽  
Vol 38 ◽  
pp. 52-57 ◽  
Author(s):  
MKM Hossain ◽  
MQ Islam ◽  
AC Mandal ◽  
S Saha
Keyword(s):  
Cross Sections ◽  
Cross Flow ◽  
Wind Effect ◽  
Total Force ◽  
Upstream Side ◽  
Pressure Distributions ◽  
Square Cylinders ◽  
Rectangular Cylinder ◽  
Identical Dimension ◽  
Mean Pressure

An experimental investigation of mean pressure distributions on a group of cylinders with square and rectangular cross-sections in a uniform cross flow is presented here. The group consists of one rectangular and two square cylinders of identical dimension. The rectangular cylinder is placed centrally in the upstream side and the other two square cylinders are placed symmetrically in the downstream side with respect to tunnel axis. Surface pressure distributions on the cylinders are measured for various longitudinal spacings of the cylinders. Wind loads are obtained in terms of drag coefficients, lift coefficients and total force coefficients. The drag on an isolated cylinder is higher in general than that on the same cylinder while it becomes part of a group. Keywords: Wind load, staggered cylinders. DOI: 10.3329/jme.v38i0.901 Journal of Mechanical Engineering Vol.38 Dec. 2007 pp.52-57

Flow in a Single Stage Centrifugal Fan With Vaneless Diffuser and Peripheral Louver Outlets

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Hongmin Li
Keyword(s):  
Working Conditions ◽  
Flow Model ◽  
Energy Analysis ◽  
Single Stage ◽  
Flow Structures ◽  
Centrifugal Fan ◽  
Vaneless Diffuser ◽  
Leakage Loss ◽  
Flow Energy ◽  
Pressure Distributions

This paper presents an analysis on the air flows in a single stage centrifugal fan with a vaneless diffuser and peripheral louver outlets. The performance data of the fan are obtained experimentally. A numerical fluid flow model is developed. The agreements between the numerical and experimental results are reasonably good. The performances of the fan under various working conditions are explained by the flow structures and pressure distributions. Flow energy analysis shows that the major energy losses in the fan are the impeller loss, the diffuser loss, and the gap leakage loss. Suggestions on the design and application of fans with such architecture are given.

3-D Flow Structures Around and Fluid-Dynamic Forces Acting on a Rectangular Cylinder in Oscillatory Flow

2003 ◽  
Author(s):  
Takahiro Yasuda ◽  
Atsushi Okajima ◽  
Minoru Moriyoshi
Keyword(s):  
Oscillatory Flow ◽  
Three Dimensional ◽  
Flow Patterns ◽  
Flow Structures ◽  
Inertia Force ◽  
Water Tank ◽  
Height Ratio ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Rectangular Cylinder

Three-dimensional flow structures around and fluiddynamic forces acting on a rectangular cylinder in oscillatory flow were investigated by numerical simulation using finite volume method. The computations were carried out for three kinds of cross-sections with width/height ratio (d/H) d/H = 0.6, 1.0 and 2.0 and for the amplitude of oscillating flow in the range of 2.5 ≤ the Keulegan-Carpenter number (KC) ≤ 25, the Stokes number (β) = 95. The calculated flow patterns and the drag and inertia force coefficients of Morison equation acting on the cylinder were compared with the experimental ones using a U-tube water tank. In this paper, we note how the KC number and the width/height ratio of the cylinders affect the unsteady and three-dimensional flow structures such as the “longitudinal vortices” and “transverse street” which formed in the case of a circular cylinder fixed in oscillatory flow, and how the CD and the CM values of Morison coefficients change corresponding to the change of the behavior of the flow patterns. Furthermore the relationship between spanwise correlation coefficient of the transverse force R(x3), where x3 is the spanwise position from the bottom of the cylinder, and three-dimensional vortex structures were investigated.

Circumferential Flow Differences in the Double-Sided Centrifugal Compressor With Non-Balanced Inlets

2016 ◽  
Author(s):  
Ce Yang ◽  
Yixiong Liu ◽  
Wangxia Wu ◽  
Lei Jing ◽  
Benjiang Wang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Axial Velocity ◽  
Static Pressure ◽  
Internal Flow ◽  
Circumferential Direction ◽  
Flow Structures ◽  
Blade Passage ◽  
Pressure Distributions ◽  
Inlet Conditions

A double-sided centrifugal compressor consists of two impellers whose inlets are non-balanced, with one side of the impeller connected to the straight duct, and the other connected to the bending duct. This leads to the differences in the inlet conditions of the double-sided impeller, resulting in the differences in the flow structures of the rear impeller along the circumferential direction. In this work, aiming at analyzing the flow structures of the rear impeller, diffuser and volute internal in three flow rate conditions, the internal flow field of the double-sided centrifugal compressor was calculated in a numerical method. It is found that the inlet bending duct results in significant inlet axial velocity difference of the rear impeller along circumferential direction. The axial velocity differences at high span positions become more obvious with the increase of the flow rate. Moreover, the jet-wake structures among the blade passage outlets are also various. At the high static pressure zones of the volute, corresponding blade passage wake regions increase and their sizes are also influenced by the inlet distortion. The circumferential distributions of the static pressure in the diffuser agree well with that in the volute. In the diffuser, the non-uniform degrees of the static pressure distributions are roughly the same at different radius positions and are weakening with the decrease of the flow rate.

scholarly journals Wake behind a Compound Wing in Ground Effect

2020 ◽  
Vol 8 (3) ◽  
pp. 156 ◽  
Author(s):  
Saeed Jamei ◽  
Adi Maimun ◽  
Rasul Niazmand Bilandi ◽  
Nor Azwadi ◽  
Simone Mancini ◽  
...  
Keyword(s):  
Ground Effect ◽  
Lower Surface ◽  
Flow Structures ◽  
Physical Domain ◽  
Turbulent Model ◽  
Computational Simulations ◽  
Crucial Point ◽  
Pressure Distributions ◽  
Reverse Taper ◽  
Wing In Ground Effect

Flow structure is a crucial point for the conceptual design of Wing-in-Ground effect (WIG) crafts. In this study, pressure distributions around a compound wing, velocity and the turbulent intensity distribution in the wake area after trailing of the wing, have been investigated numerically. Computational simulations were completed regarding various angles of attack in-ground-effect. Two parts made up the compound wing: The first composed by one rectangular wing in the center, the second composed by a reverse taper wing, consisting of an anhedral angle at the side. A realizable k-ε turbulent model exhibited the flow field in the physical domain about the wing surface. The numerical results of the compound wing were validated using the data provided by wind tunnel tests. The flow structures around the compound wing were compared with that of a rectangular wing for different conditions. It was found that the pressure distribution on the rectangular wing was weaker than at the lower surface for the compound wing. However, the suction effect on the upper surface of the rectangular wing was higher. Also, the velocity defect and the turbulence level in the wake area was greater behind the compound wing.

Numerical Model of a Deep Surge Cycle in Low-Speed Centrifugal Compressor

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Grzegorz Liśkiewicz ◽  
Michał Kulak ◽  
Krzysztof Sobczak ◽  
Matthew Stickland
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Pressure Rise ◽  
Flow Structures ◽  
Centrifugal Blower ◽  
Cycle Frequency ◽  
Low Speed ◽  
Pressure Distributions ◽  
Important Input ◽  
Efficient Protection

Abstract In this article, a numerical model of the full surge cycle is presented for the low-speed centrifugal blower and compared with the experiment. Surge phenomenon is very dangerous for the compressor operation. Therefore, the possibility of studying its physics experimentally is strongly limited. The application of numerical methods allows one to safely analyze surge physics without causing risks to the operating crew. This article presents a description of the applied numerical method and exhaustive analysis of the flow structures observed at consecutive stages of the surge cycle. The surge is known to be very difficult to be simulated due to large timescale and region of influence. This study also shows the importance of an appropriate choice of the simulation definition and the boundary conditions. The presented method allows gathering information about features such as the regions of flow reversal, pressure distributions, pressure rise, cycle frequency, and others. All the aforementioned information provides important input to the efficient antisurge system design. The model has been validated by a comparison with the experimental data. Thanks to simulation, standardized antisurge solutions could be possibly replaced with more efficient protection schemes tailored to a given machine.

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