Interference Between Two Circular Cylinders of Finite Height Vertically Immersed in a Turbulent Boundary Layer

1982 ◽  
Vol 104 (4) ◽  
pp. 529-536 ◽  
Author(s):  
S. Taniguchi ◽  
H. Sakamoto ◽  
M. Arie
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Angle Of Attack ◽  
Circular Cylinders ◽  
Wake Region ◽  
Pressure Distributions ◽  
Finite Height ◽  
Drag And Lift ◽  
Circumferential Pressure

Measurements were made of the circumferential pressure distributions around two cylinders of finite height h and diameter d, spaced a distance s apart and vertically immersed in a turbulent boundary layer. The angle of attack φ and the dimensionless spacing s/d were varied. Drag and lift characteristics of both cylinders were classified into three regions divided by two zero-lift lines, namely 0 ≲ φ ≲ 30 deg, 30 ≲ φ ≲ 120 deg, and 120 ≲ φ ≲ 180 deg, in which interference between the two cylinders was found to be almost negligible for s/d ≳ 4.0, except for an influence in the wake region of the upstream cylinder.

A Model for High-Reynolds-Number Flow Past Rough-Walled Circular Cylinders

1977 ◽  
Vol 99 (3) ◽  
pp. 486-493 ◽  
Author(s):  
O. Gu¨ven ◽  
V. C. Patel ◽  
C. Farell
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Circular Cylinder ◽  
Turbulent Boundary Layer ◽  
Pressure Coefficient ◽  
Empirical Relation ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Circular Cylinders ◽  
Mean Flow

A simple analytical model for two-dimensional mean flow at very large Reynolds numbers around a circular cylinder with distributed roughness is presented and the results of the theory are compared with experiment. The theory uses the wake-source potential-flow model of Parkinson and Jandali together with an extension to the case of rough-walled circular cylinders of the Stratford-Townsend theory for turbulent boundary-layer separation. In addition, a semi-empirical relation between the base-pressure coefficient and the location of separation is used. Calculation of the boundary-layer development, needed as part of the theory, is accomplished using an integral method, taking into account the influence of surface roughness on the laminar boundary layer and transition as well as on the turbulent boundary layer. Good agreement with experiment is shown by the results of the theory. The significant effects of surface roughness on the mean-pressure distribution on a circular cylinder at large Reynolds numbers and the physical mechanisms giving rise to these effects are demonstrated by the model.

scholarly journals Metric for attractor overlap

2019 ◽  
Vol 874 ◽  
pp. 720-755 ◽  
Author(s):  
Rishabh Ishar ◽  
Eurika Kaiser ◽  
Marek Morzyński ◽  
Daniel Fernex ◽  
Richard Semaan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Three Dimensional ◽  
Particle Image Velocimetry Data ◽  
Open Loop ◽  
Operating Conditions ◽  
Wall Turbulence ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Starting Point

We present the first general metric for attractor overlap (MAO) facilitating an unsupervised comparison of flow data sets. The starting point is two or more attractors, i.e. ensembles of states representing different operating conditions. The proposed metric generalizes the standard Hilbert-space distance between two snapshot-to-snapshot ensembles of two attractors. A reduced-order analysis for big data and many attractors is enabled by coarse graining the snapshots into representative clusters with corresponding centroids and population probabilities. For a large number of attractors, MAO is augmented by proximity maps for the snapshots, the centroids and the attractors, giving scientifically interpretable visual access to the closeness of the states. The coherent structures belonging to the overlap and disjoint states between these attractors are distilled by a few representative centroids. We employ MAO for two quite different actuated flow configurations: a two-dimensional wake with vortices in a narrow frequency range and three-dimensional wall turbulence with a broadband spectrum. In the first application, seven control laws are applied to the fluidic pinball, i.e. the two-dimensional flow around three circular cylinders whose centres form an equilateral triangle pointing in the upstream direction. These seven operating conditions comprise unforced shedding, boat tailing, base bleed, high- and low-frequency forcing as well as two opposing Magnus effects. In the second example, MAO is applied to three-dimensional simulation data from an open-loop drag reduction study of a turbulent boundary layer. The actuation mechanisms of 38 spanwise travelling transversal surface waves are investigated. MAO compares and classifies these actuated flows in agreement with physical intuition. For instance, the first feature coordinate of the attractor proximity map correlates with drag for the fluidic pinball and for the turbulent boundary layer. MAO has a large spectrum of potential applications ranging from a quantitative comparison between numerical simulations and experimental particle-image velocimetry data to the analysis of simulations representing a myriad of different operating conditions.

Axisymmetric Turbulent Boundary Layers in Zero Pressure-Gradient Flows

1972 ◽  
Vol 39 (1) ◽  
pp. 25-32 ◽  
Author(s):  
G. N. V. Rao ◽  
N. R. Keshavan
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flows ◽  
Outer Part ◽  
Stability Limit ◽  
Circular Cylinders ◽  
Law Of The Wall ◽  
Probable Effect ◽  
Stress Layer ◽  
The Stability

An experimental and theoretical study of the axisymmetric turbulent boundary layer on circular cylinders over a range of radius Reynolds numbers Ra from 425 to 2 × 105, suggests the existence of a law of the wall in the form u* = A log Y* + B, where Y* = (uτa/ν) log (r/a). The constant A depends only on Ra while B has been found to depend on Ra as well as auτ/ν. It was observed that from the beginning of transition to turbulent flow in the boundary layer, there was a “negative wake” region in the outer part of the boundary layer which progressively disappeared as the flow was swept downstream, giving, at some station, a velocity profile (called here the “marginal profile”), which had no wake component. Further downstream, there was progressively increasing positive wake component. In these regions, it is surmized that the penetration of the viscous effect from the wall to larger distances across the boundary layer (as indicated by the absence of a constant stress layer), as well as the probable effect of viscosity in the wake portion (as in a purely axisymmetric wake), yielded similarlity of the defect (U − u)/uτ, only in terms of the quantity (ruτ/ν) for a given Ra. From a study of the rate of decrease of Cf with Rx in laminar and turbulent flows, there is reason to believe that an initially turbulent boundary layer will undergo relaminarization if Ra is less than about 15,000 which may be compared with the stability limit of 11,000 found by Rao [6].

scholarly journals Flow over Rectangular Cylinders Immersed in a Turbulent Boundary Layer : Part 2 Flow Patterns and Pressure Distributions

1975 ◽  
Vol 18 (125) ◽  
pp. 1269-1276 ◽  
Author(s):  
Mikio ARIE ◽  
Masaru KIYA ◽  
Hisataka TAMURA ◽  
Masao KOSUGI ◽  
Katsuya TAKAOKA
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flow Patterns ◽  
Pressure Distributions ◽  
Rectangular Cylinders

Physics of unsteady blunt-fin-induced shock wave/turbulent boundary layer interactions

1994 ◽  
Vol 273 ◽  
pp. 375-409 ◽  
Author(s):  
Leon Brusniak ◽  
David S. Dolling
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Time History ◽  
Separated Flow ◽  
Flow Region ◽  
Horseshoe Vortex ◽  
Wall Pressure ◽  
Pressure Measurements ◽  
Separation Shock ◽  
Pressure Distributions

Fluctuating wall-pressure measurements have been made on the centreline upstream of a blunt fin in a Mach 5 turbulent boundary layer. By examining the ensemble-averaged wall-pressure distributions for different separation shock foot positions, it has been shown that local fluctuating wall-pressure measurements are due to a distinct pressure distribution, [weierp ]i, which undergoes a stretching and flattening effect as its upstream boundary translates aperiodically between the upstream-influence and separation lines. The locations of the maxima and minima in the wall-pressure standard deviation can be accurately predicted using this distribution, providing quantitative confirmation of the model. This model also explains the observed cross-correlations and ensemble-average measurements within the interaction. Using the [weierp ]i model, wall-pressure signals from under the separated flow region were used to reproduce the position–time history of the separation shock foot. The unsteady behaviour of the primary horseshoe vortex and its relation to the unsteady separation shock is also described. The practical implications are that it may be possible to predict some of the unsteady aspects of the flowfield using mean wall-pressure distributions obtained from either computations or experiments; also, to minimize the fluctuating loads caused by the unsteadiness, flow control methods should focus on reducing the magnitude of the [weierp ]i gradient (∂[weierp ]i/∂x).

scholarly journals Correlation between Large-Scale Streamwise Velocity Features and the Height of Coherent Vortices in a Turbulent Boundary Layer

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 286
Author(s):  
Shaurya Shrivastava ◽  
Theresa Saxton-Fox
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Scale ◽  
Streamwise Velocity ◽  
Wake Region ◽  
Strong Negative Correlation ◽  
Vortex Model ◽  
Image Velocimetry ◽  
Coherent Vortices ◽  
Conditional Averaging

The preferential organisation of coherent vortices in a turbulent boundary layer in relation to local large-scale streamwise velocity features was investigated. Coherent vortices were identified in the wake region using the Triple Decomposition Method (originally proposed by Kolář) from 2D particle image velocimetry (PIV) data of a canonical turbulent boundary layer. Two different approaches, based on conditional averaging and quantitative statistical analysis, were used to analyze the data. The large-scale streamwise velocity field was first conditionally averaged on the height of the detected coherent vortices and a change in the sign of the average large scale streamwise fluctuating velocity was seen depending on the height of the vortex core. A correlation coefficient was then defined to quantify this relationship between the height of coherent vortices and local large-scale streamwise fluctuating velocity. Both of these results indicated a strong negative correlation in the wake region of the boundary layer between vortex height and large-scale velocity. The relationship between vortex height and full large-scale velocity isocontours was also studied and a conceptual model based on the findings of the study was proposed. The results served to relate the hairpin vortex model of Adrian et al. to the scale interaction results reported by Mathis et al., and Chung and McKeon.

Study of Possibility of Simulation of Thick Turbulent Boundary Layer on a Flat Plate of Limited Length

2012 ◽  
Vol 7 (3) ◽  
pp. 44-56
Author(s):  
Vladimir Kornilov
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flat Plate ◽  
Effective Means ◽  
Leading Edge ◽  
Circular Cylinders ◽  
Mean Velocity ◽  
Velocity Scale ◽  
Limited Length ◽  
Fluctuation Boundary

The experiments directed to the study of possibility of simulation of thick equilibrium (according to Clauser) incompressible turbulent boundary layer on a flat plate of limited length have been performed. It is shown that the artificial generators manufactured from circular cylinders (pins) of adjustable height h, which were mounted normal to the wall in a staggered order in two rows in х in vicinity of the plate leading edge are quite effective means of artificial boundary layer thickening. In most cases both the averaged and fluctuation boundary-layer characteristics at a downstream distance about 530 cylinder diameters have values typical for naturally-developed turbulent boundary layer. Mean velocity profiles in the artificially thickened boundary layer taken in wall-law variables are approximated with a good accuracy by the wellknown velocity law valid for canonic boundary layer and they are generalized by a unified dependence using empirical velocity scale

Effect of Shock Boundary Layer Interaction on Aerofoil Pressure Distributions at Transonic Speeds

1963 ◽  
Vol 67 (634) ◽  
pp. 674-677
Author(s):  
D. Tirumalesa
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Turbulent Boundary Layer ◽  
Two Dimensional ◽  
Relative Thickness ◽  
Circular Arc ◽  
Layer Interaction ◽  
Pressure Distributions ◽  
Boundary Layer Interaction ◽  
Theoretical Results

SummaryA method of improving pressure distributions predicted by inviscid theory over two-dimensional aerofoils at transonic speeds taking into account shock-wave turbulent boundary layer interaction as obtained in the case of the flat plate is described.The method was applied to a non-lifting circular arc aerofoil of eight per cent relative thickness. The shock wave location, pressure distribution and drag coefficient were calculated and compared with experimental and inviscid theoretical results.It has been found that the method gives results which are consistent with experimental results in various aspects.

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