Selective Roughness in the Boundary Layer to Suppress Flow-Induced Motions of Circular Cylinder at 30,000

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Hongrae Park ◽  
Michael M. Bernitsas ◽  
R. Ajith Kumar
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Passive Control ◽  
Flow Direction ◽  
Water Channel ◽  
Maximum Amplitude ◽  
Cylinder Surface ◽  
Complex Flow ◽  
Strong Suppression ◽  
Wide Range

A passive control means to suppress flow-induced motions (FIM) of a rigid circular cylinder in the TrSL3, high-lift, flow regime is formulated and tested experimentally. The developed method uses passive turbulence control (PTC) consisting of selectively located roughness on the cylinder surface with thickness about equal to the boundary layer thickness. The map of “PTC-to-FIM,” developed in previous work, revealed robust zones of weak suppression, strong suppression, hard galloping, and soft galloping. PTC has been used successfully to enhance FIM for hydrokinetic energy harnessing using the VIVACE Converter. PTC also revealed the potential to suppress FIM to various levels. The map is flow-direction dependent. In this paper, the “PTC-to-FIM” map is used to guide development of FIM suppression devices that are flow-direction independent and hardly affect cylinder geometry. Experiments are conducted in the Low Turbulence Free Surface Water Channel of the University of Michigan on a rigid, horizontal, circular cylinder, suspended on springs. Amplitude and frequency measurements and broad field-of-view visualization reveal complex flow structures and their relation to suppression. Several PTC designs are tested to understand the effect of PTC roughness, location, coverage, and configuration. Gradual modification of PTC parameters, leads to improved suppression and evolution of a design reducing the VIV synchronization range. Over a wide range of high reduced velocities, VIV is fully suppressed. The maximum amplitude occurring near the system’s natural frequency is reduced by about 63% compared to the maximum amplitude of the smooth cylinder.

Selective Roughness in the Boundary Layer to Suppress Flow-Induced Motions of Circular Cylinder at 30,000

2011 ◽  
Author(s):  
Hongrae Park ◽  
Michael M. Bernitsas ◽  
R. Ajith Kumar
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Passive Control ◽  
Flow Direction ◽  
Water Channel ◽  
Maximum Amplitude ◽  
Cylinder Surface ◽  
Complex Flow ◽  
Strong Suppression ◽  
Wide Range

A passive control means to suppress flow-induced motions (FIM) of a rigid circular cylinder in the TrSL3, high-lift, flow regime is formulated and tested experimentally. The method developed uses passive turbulence control (PTC) consisting of selectively located roughness on the cylinder surface with thickness about equal to the boundary layer thickness. The map of “PTC-to-FIM”, developed in previous work, revealed robust zones of weak suppression, strong suppression, hard galloping, and soft galloping. PTC has been used successfully to enhance FIM for hydrokinetic energy harnessing using the VIVACE Converter. The same technology revealed the potential to suppress FIM to various levels. The map is flow-direction dependent. In this paper, the “PTC-to-FIM” map is used to guide development of FIM suppression devices that are flow-direction independent and hardly affect cylinder geometry. Experiments are conducted in the Low Turbulence Free Surface Water Channel of the University of Michigan on a rigid, horizontal, circular cylinder, suspended on springs. Amplitude and frequency measurements and broad field-of-view visualization reveal complex flow structures and their relation to suppression. Several PTC designs are tested to understand PTC direction, roughness, thickness, and coverage. Gradual modification of PTC parameters, leads to improved suppression and evolution of a design reducing the VIV synchronization range, fully suppressing VIV in a wide range, and reducing the maximum occurring near the system’s natural frequency by about 60% compared to the maximum amplitude of the smooth cylinder.

scholarly journals High Order Accurate Numerical Simulation of Vortex-Induced Vibrations of a Cooled Circular Cylinder Case using Solution Dependent Weighted Least Square Gradient Calculations

2021 ◽  
Vol 321 ◽  
pp. 04005
Author(s):  
Chandrakant Sonawane ◽  
Priyambada Praharaj ◽  
Anand Pandey ◽  
Atul Kulkarni
Keyword(s):  
Circular Cylinder ◽  
Natural Frequencies ◽  
Flow Direction ◽  
Weighted Least Squares ◽  
Fluid Structure Interaction ◽  
Maximum Amplitude ◽  
Flowing Fluid ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Wide Range

In this paper, the fluid-structure interaction problem: vortex-induced vibration of a cooled circular cylinder involving thermal buoyancy is numerically investigated. The elastically mounted cylinder having a temperature lower than the flowing fluid is modelled using mass-spring-damper hence allowed to vibrate in the transverse direction to the flow direction. The gravity is acting opposite to the flow direction. In-house fluid-structure interaction solver is developed based on Harten Lax and van Leer with contact for artificial compressibility Riemann solver. The arbitrarily Lagrangian-Eulerian formulation is employed here, and the mesh is dynamically moved using radial basis function-based interpolation. The solution-dependent weighted least squares based gradient calculations are developed to achieve higher-order accuracy over unstructured meshes. The laminar incompressible flow at Reynolds number, Re = 200, and Prandtl number, Pr = 0.71, is simulated for the mass ratio of 1 and reduced damping coefficient of 0.001. The flow is investigated for Richardson number (-1, 0) and over a wide range of natural frequencies of the cylinder. The heat transfer characteristics from a cylinder are captured and compared with the existing literature results. From the study, it can be observed that in the presence of the thermal boundary layer, the oscillation of the cylinder increases to its maximum amplitude, particularly for values of natural frequencies (0.063 – 0.3).

Potential Flow Solution for Crossflow Impingement of a Slot Jet on a Circular Cylinder

1976 ◽  
Vol 98 (2) ◽  
pp. 249-255 ◽  
Author(s):  
H. Miyazaki ◽  
E. M. Sparrow
Keyword(s):  
Boundary Layer ◽  
Nusselt Number ◽  
Circular Cylinder ◽  
Potential Flow ◽  
Closed Form Solution ◽  
Form Solution ◽  
Stream Velocity ◽  
Cylinder Surface ◽  
Stagnation Region ◽  
Flow Solution

A closed-form solution has been obtained for the potential flow about a circular cylinder situated in an impinging slot jet. Among other results, the potential flow solution yields the free stream velocity for the boundary layer adjacent to the cylinder surface. A basic feature of the solution is the division of the flow field into subdomains, thereby making it possible to employ harmonic functions that are appropriate to each such subdomain. The boundary conditions on the free streamline and the conditions of continuity between the subdomains are satisfied by a combination of least squares and point matching constraints. Numerical evaluation of the solution was carried out for cylinder diameters greater or equal to the nozzle width and for a range of dimensionless separation distances between the nozzle and the impingement surface. Results are presented for the velocity and pressure distributions on the cylinder surface, for the position of the free streamline, and for the velocity gradients at the stagnation point. The latter serve as input information to the Nusselt number and skin friction expressions that are given by boundary layer theory. Comparisons were made with available experimental results for the pressure distribution, velocity gradient, and Nusselt number, and good agreement was found to prevail in the stagnation region.

Influence of Chord Length and Inlet Boundary Layer on the Secondary Losses of Turbine Blades

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Helmut Sauer ◽  
Robin Schmidt ◽  
Konrad Vogeler
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Flow Direction ◽  
Velocity Ratio ◽  
Main Flow ◽  
Chord Length ◽  
Displacement Thickness ◽  
Wide Range ◽  
Main Flow Direction

In this paper, results concerning the influence of chord length and inlet boundary layer thickness on the endwall loss of a linear turbine cascade are discussed. The investigations were performed in a low speed cascade tunnel using the turbine profile T40. The turning of 90 deg and 70 deg, the velocity ratio in the cascade from 1.0 to 3.5 as well as the chord length of 100 mm, 200 mm, and 300 mm were specified. In a measurement distance of one chord behind the cascade in main flow direction, an approximate proportionality of endwall loss and chord was observed in a wide range of velocity ratios. At small measurement distances (e.g., s2/l=0.4), this proportionality does not exist. If a part of the flow path within the cascade is approximately incorporated, a proportionality to the chord at small measurement distances can be obtained, too. Then, the magnitude of the endwall loss mainly depends on the distance in main flow direction. At velocity ratios near 1.0, the influence of the chord decreases rapidly, while at a velocity ratio of 1.0, the endwall loss is independent of the chord. By varying the inlet boundary layer thickness, no correlation of displacement thickness and endwall loss was achieved. A calculation method according to the modified integral equation by van Driest delivers the wall shear stress. Its influence on the endwall loss was analyzed.

Map of Passive Turbulence Control to Flow-Induced Motions for a Circular Cylinder at 30,000

2013 ◽  
Author(s):  
Hongrae Park ◽  
Michael M. Bernitsas ◽  
Che-Chun Chang
Keyword(s):  
Circular Cylinder ◽  
Amplitude Ratio ◽  
Damping Ratio ◽  
Water Channel ◽  
University Of Michigan ◽  
Strong Suppression ◽  
Variable Parameters ◽  
Turbulence Control ◽  
The University ◽  
Passive Turbulence Control

Passive turbulence control (PTC) in the form of two straight roughness strips with variable width, and thickness about equal to the boundary layer thickness, is used to modify the flow-induced motions (FIM) of a rigid circular cylinder. The cylinder is supported by two end-springs and the flow is in the TrSL3, high-lift, regime. The PTC-to-FIM Map, developed in previous work, revealed zones of weak suppression, strong suppression, hard galloping, and soft galloping. In this paper the sensitivity of the PTC-to-FIM Map to: (a) the width of PTC covering, (b) PTC covering a single or multiple zones, (c) PTC being straight or staggered is studied experimentally. Experiments are conducted in the Low Turbulence Free Surface Water Channel of the University of Michigan. Fixed parameters are: cylinder diameter D = 8.89cm, m* = 1.725, spring stiffness K = 763N/m, aspect ratio l/D = 10.29, and damping ratio ζ = 0.019. Variable parameters are: circumferential PTC location αPTC ∈ [0°−180°], Reynolds number Re ∈ [30,000–120,000], flow velocity U ∈ [0.36m/s–1.45m/s]. Measured quantities are: amplitude ratio A/D, frequency ratio fosc/fn,w, and synchronization range. As long as the roughness distribution is limited to remain within a zone, the width of the strips does not affect the FIM response. When multiple zones are covered, the strong suppression zone dominates the FIM.

scholarly journals Flow-induced vibrations of a rotating cylinder

2014 ◽  
Vol 740 ◽  
pp. 342-380 ◽  
Author(s):  
Rémi Bourguet ◽  
David Lo Jacono
Keyword(s):  
Symmetry Breaking ◽  
Flow Direction ◽  
Cross Flow ◽  
Maximum Amplitude ◽  
Rotating Cylinder ◽  
Free Vibrations ◽  
Cylinder Surface ◽  
Single Vortex ◽  
Flow Induced Vibrations ◽  
The Impact

AbstractThe flow-induced vibrations of a circular cylinder, free to oscillate in the cross-flow direction and subjected to a forced rotation about its axis, are analysed by means of two- and three-dimensional numerical simulations. The impact of the symmetry breaking caused by the forced rotation on the vortex-induced vibration (VIV) mechanisms is investigated for a Reynolds number equal to $100$, based on the cylinder diameter and inflow velocity. The cylinder is found to oscillate freely up to a rotation rate (ratio between the cylinder surface and inflow velocities) close to $4$. Under forced rotation, the vibration amplitude exhibits a bell-shaped evolution as a function of the reduced velocity (inverse of the oscillator natural frequency) and reaches $1.9$ diameters, i.e. three times the maximum amplitude in the non-rotating case. The free vibrations of the rotating cylinder occur under a condition of wake–body synchronization similar to the lock-in condition driving non-rotating cylinder VIV. The largest vibration amplitudes are associated with a novel asymmetric wake pattern composed of a triplet of vortices and a single vortex shed per cycle, the ${\rm T} + {\rm S}$ pattern. In the low-frequency vibration regime, the flow exhibits another new topology, the U pattern, characterized by a transverse undulation of the spanwise vorticity layers without vortex detachment; consequently, free oscillations of the rotating cylinder may also develop in the absence of vortex shedding. The symmetry breaking due to the rotation is shown to directly impact the selection of the higher harmonics appearing in the fluid force spectra. The rotation also influences the mechanism of phasing between the force and the structural response.

The Passive Control of Unsteady Flow Structure Downstream of a Circular Cylinder in Shallow Water

2013 ◽  
Author(s):  
Tahir Durhasan ◽  
Engin Pınar ◽  
Muhammed M. Aksoy ◽  
Göktürk M. Özkan ◽  
Hüseyin Akıllı ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Shallow Water ◽  
Flow Structure ◽  
Vortex Shedding ◽  
Passive Control ◽  
Outer Cylinder ◽  
Water Channel ◽  
Stream Velocity ◽  
Image Velocimetry ◽  
Perforated Cylinder

In the present study, it was aimed to suppress the vortex shedding occurred in the near wake of a circular cylinder (inner cylinder) by perforated cylinder (outer cylinder) in shallow water flow. The inner cylinder (Di) and outer cylinder (Do) have fixed diameters, such as Di = 50 mm and Do = 100 mm, respectively. The effect of porosity, β, was examined using four different porosity ratios, 0.3, 0.5, 0.6 and 0.8. In order to investigate the effect of arc angle of outer cylinder, α, four different arc angles, α = 360°, 180°, 150° and 120° were used. The experiments were implemented in a recirculating water channel using the particle image velocimetry, PIV technique. The depth-averaged free-stream velocity was kept constant as U∞ = 100 mm/s which corresponded to a Reynolds number of Re = 5000 based on the inner cylinder diameter. The results demonstrated that the suppression of vortex shedding is substantially achieved by perforated outer cylinder for arc angle of α = 360° at β = 0.6. Turbulence Kinetic Energy statistics show that porosity, β, is highly effective on the flow structure. In comparison with the values obtained from the case of the bare cylinder, at porosity β = 0.6, turbulence characteristics are reduced by %80. Also, the point, which the values of maximum TKE, shift to a farther downstream compared to the case of bare cylinder.

scholarly journals Flow past a circular cylinder on a β-plane

1982 ◽  
Vol 306 (1496) ◽  
pp. 533-556 ◽  
Keyword(s):  
Aspect Ratio ◽  
Circular Cylinder ◽  
Large Scale ◽  
Flow Direction ◽  
Water Channel ◽  
Unsteady Flows ◽  
Boundary Layer Separation ◽  
Coriolis Parameter ◽  
The North ◽  
Flow Past

With a view to obtaining a fuller understanding of the interactions between topography and large-scale geophysical flows, a series of laboratory investigations have been performed on the flow past a right circular cylinder in a rotating water channel. For large-scale flows on a spherical Earth the variation of the Coriolis parameter, F = 2Ωsinϕ , with latitude, ϕ, is commonly written (Pedlosky 1979) as F = f + β 0 y where f = 2Ωsinϕ o , β o = 2Ωcosϕ o /R E , y is the distance to the north from the reference latitude ϕ o , and R E and Ω( = 7.29 x 10 -5 s-1 ) are the radius and rotation rate of the Earth respectively. In this paper we shall discuss laboratory experiments in which the variation of F can be simulated. We shall refer to those studies in which β = 0 (i.e. the Coriolis parameter is uniform over the latitudinal extent of the region under investigation) as f-plane experiments. Models for which β o is non-zero will be referred to as β-plane experiments. In the experiments the β-effect has been simulated by tilting the upper and lower surfaces of the channel so that the depth of the fluid varies in the cross-stream direction. Flow patterns have been obtained over a range of five independent non-dimensional parameters: Rossby and Ekman numbers, cylinder aspect ratio, β-parameter and flow direction (‘eastward’ or ‘westward’). A dramatic difference in downstream behaviour is found between f-plane, β-plane westward and /plane eastward flows. In particular, the β-plane eastward flows are characterized by bunching and pinching of streamlines in the wake region, the generation of damped stationary Rossby waves and downstream acceleration. Compared with f-plane flows the β-effect is shown to inhibit boundary layer separation from the cylinder for eastward flow and to enhance the separation for westward flow. Data are presented from all cases to show the asymmetry of the downstream flows and the transitions from fully attached to unsteady flows. Under otherwise identical conditions the downstream extent of the separated bubble region is much greater for β-plane westward flow than, in turn, for f-plane and β-plane eastward flows. In addition, the data indicate that the size of the bubble increases with increasing Rossby number and decreases with increasing Ekman number and cylinder aspect ratio. For eastward flow the bubble size decreases with increasing β-parameter and for westward flow it increases with increasing β-parameter. Unsteady flows are investigated and instances of asymmetrical vortex shedding are presented.

Premature boundary layer transition caused by surface static pressure tappings

1988 ◽  
Vol 92 (912) ◽  
pp. 63-68 ◽  
Author(s):  
P. E. Roach ◽  
J. T. Turner
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Static Pressure ◽  
Cross Flow ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Wide Range ◽  
Boundary Layer Interaction

Summary Experiments have been performed to study the influence of multiple surface static pressure tappings on transition of the boundary layer on a circular cylinder in cross-flow. A wide range of tapping and cylinder dimensions have been examined to demonstrate that the tappings can act in the same way as trip wires or other surface roughness to reduce the Reynolds number at which transition occurs. Hence, the pressure distribution around the cylinder may be influenced by the presence of the tappings, leading to incorrect measurements. Examination of the data has resulted in a correlation which should make it possible to avoid this tapping/boundary layer interaction in future experiments involving similar cylindrical bodies.

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