Quintuple Hot-Wire Measurements of the Turbulence Structure in Confined Swirling Flows

1999 ◽  
Vol 121 (3) ◽  
pp. 517-525 ◽  
Author(s):  
F. Holza¨pfel ◽  
B. Lenze ◽  
W. Leuckel
Keyword(s):  
Turbulence Structure ◽  
The Novel ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Isothermal Model ◽  
Swirl Flows ◽  
Turbulence Closures ◽  
Measured Flow ◽  
The Mean ◽  
Development And Validation

The novel quintuple hot-wire measurement technique was used to perform detailed measurements of the mean velocities and Reynolds stresses in an isothermal model combustion chamber at two different levels of swirl. The measured flow quantities are analyzed and described in detail where the emphasis is put on typical swirl-related effects as well as the interaction of rotation and turbulence dynamics. The results provide a well-documented data base for the development and validation of turbulence closures. They also serve to improve understanding of specific characteristics of swirl flows.

The Structure of a Boundary Layer on a Rough Wall with Blowing and Heat Transfer

1979 ◽  
Vol 101 (2) ◽  
pp. 193-198 ◽  
Author(s):  
M. M. Pimenta ◽  
R. J. Moffat ◽  
W. M. Kays
Keyword(s):  
Boundary Layer ◽  
Correlation Coefficients ◽  
Turbulent Heat Flux ◽  
Turbulent Heat ◽  
Turbulence Structure ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Mean Velocity ◽  
Length Constant ◽  
The Mean

A regular, deterministic, rough surface was tested at four velocities from 11 to 40 m/s, with and without blowing, to evaluate the Stanton number and friction factor characteristics. Hot-wire data were taken to document the turbulence components, the Reynolds stresses, and the turbulent heat flux. Data are presented concerning the streamwise development of the mean and fluctuating components, and the effect of blowing. Correlation coefficients and mixing lengths were deduced from the hot-wire data and are also presented. While the mean velocity data showed only two allowable states for the boundary layer (laminar and “fully rough”), the turbulence structure indicated a third: “transitionally rough”. Distributions of u′v′/uτ2 and v′t′/uτtτ are similar, except for high blowing (F = 0.004). The turbulent Prandtl number lies between 0.85 and 1.0 for the entire layer, and a mixing length constant of κ = 0.41 describes the data with good accuracy for all velocities and all values of blowing tested.

Hot Wire Measurements at the Exit of a Centrifugal Compressor Impeller

1979 ◽  
Vol 193 (1) ◽  
pp. 341-347
Author(s):  
A. Goulas ◽  
R. C. Baker
Keyword(s):  
Centrifugal Compressor ◽  
Magnetic Tape ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Mean Velocity ◽  
Isentropic Flow ◽  
Compressor Impeller ◽  
The Mean

Hot wire measurements at the exit of a small centrifugal compressor impeller are reported. Three different hot wire readings were obtained and stored on a magnetic tape for each point by gating the analogue hot wire signal with a pulse which indicated circumferential position. The combination of the three readings yielded the mean velocity and some Reynolds stresses at each point. The measurements show a ‘jet-wake’ profile towards the shroud and ‘isentropic’ flow near the hub.

The reduction and elimination of a closed separation region by free-stream turbulence

2001 ◽  
Vol 446 ◽  
pp. 271-308 ◽  
Author(s):  
M. KALTER ◽  
H. H. FERNHOLZ
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Free Stream ◽  
Reverse Flow ◽  
Flow Region ◽  
Adverse Pressure Gradient ◽  
Turbulence Structure ◽  
Hot Wire ◽  
Free Stream Turbulence ◽  
The Mean

This paper is an extension of an experimental investigation by Alving & Fernholz (1996). In the present experiments the effects of free-stream turbulence were investigated on a boundary layer with an adverse pressure gradient and a closed reverse-flow region. By adding free-stream turbulence the mean reverse-flow region was shortened or completely eliminated and this was used to control the size of the separation bubble. The turbulence intensity was varied between 0.2% and 6% using upstream grids while the turbulence length scale was on the order of the boundary layer thickness. Mean and fluctuating velocities as well as spectra were measured by means of hot-wire and laser-Doppler anemometry and wall shear stress by wall pulsed-wire and wall hot-wire probes.Free-stream turbulence had a small effect on the boundary layer in the mild adverse-pressure-gradient region but in the vicinity of separation and along the reverse-flow region mean velocity profiles, skin friction and turbulence structure were strongly affected. Downstream of the mean or instantaneous reverse-flow regions highly disturbed boundary layers developed in a nominally zero pressure gradient and converged to a similar turbulence structure in all three cases at the end of the test section. This state was, however, still very different from that in a canonical boundary layer.

An Explicit Non-Real Time Data Reduction Method of Triple Sensors Hot-Wire Anemometer in Three-Dimensional Flow

1988 ◽  
Vol 110 (2) ◽  
pp. 110-119 ◽  
Author(s):  
Y. T. Chew ◽  
R. L. Simpson
Keyword(s):  
Real Time ◽  
Three Dimensional ◽  
Computation Time ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Time Data ◽  
Three Dimensional Flow ◽  
Mean Velocity ◽  
Dimensional Flow ◽  
The Mean

An explicit non-real time method of reducing triple sensor hot-wire anenometer data to obtain the three mean velocity components and six Reynolds stresses, as well as their turbulence spectra in three-dimensional flow is proposed. Equations which relate explicitly the mean velocity components and Reynolds stresses in laboratory coordinates to the mean and mean square sensors output voltages in three stages are derived. The method was verified satisfactorily by comparison with single sensor hot-wire anemometer measurements in a zero pressure gradient incompressible turbulent boundary layer flow. It is simple and requires much lesser computation time when compared to other implicit non-real time method.

An experimental study of the turbulence structure in smooth- and rough-wall boundary layers

1987 ◽  
Vol 177 ◽  
pp. 437-466 ◽  
Author(s):  
A. E. Perry ◽  
K. L. Lim ◽  
S. M. Henbest
Keyword(s):  
Boundary Layers ◽  
Wall Turbulence ◽  
Wall Region ◽  
Turbulence Structure ◽  
Hot Wire ◽  
Mean Flow ◽  
Wavy Surfaces ◽  
The Mean ◽  
Flow Turbulence ◽  
Turbulent Wall

The turbulence structure in zero-pressure-gradient boundary layers above smooth, rough and wavy surfaces was investigated. The mean flow, turbulence intensity and spectral data for both smooth and rough surfaces show support for the attached eddy hypothesis of Townsend (1976), the model for wall turbulence proposed by Perry & Chong (1982) and the extended version developed by Perry, Henbest & Chong (1986). Anomalies in hot-wire behaviour when measuring in the turbulent wall region of the flow were discovered and some of these have been resolved.

The Effect of Buoyancy on the Turbulence Structure of Vertical Round Jets

1978 ◽  
Vol 100 (4) ◽  
pp. 659-664 ◽  
Author(s):  
F. Tamanini
Keyword(s):  
Strain Tensor ◽  
Turbulent Heat Flux ◽  
Turbulent Heat ◽  
Turbulence Structure ◽  
Reynolds Stresses ◽  
Buoyant Jet ◽  
Buoyant Flows ◽  
Round Jets ◽  
The Mean ◽  
Rate Of Dissipation

The paper presents an application of the algebraic stress modeling (ASM) technique to the prediction of the flow in a turbulent round buoyant jet. In the ASM approach, algebraic formulas are obtained for the Reynolds stresses, uiuj, and for the components of the turbulent heat flux, tui. In the model used here, transport equations are solved for the turbulence kinetic energy, k, its dissipation, ε, and the mean square temperature fluctuations, g. The study shows that buoyancy increases the rate of dissipation of g above the values indicated by previous recommendations for the modeling of that quantity. As a possible explanation for this result it is suggested that buoyancy introduces anisotropy in the fluctuations at the dissipation scale. The study shows that the contribution from the secondary components of the strain tensor to the production of k is non-negligible. In addition, between 12 and 17 percent of the longitudinal enthalpy flux is contributed by the turbulent fluctuations. Finally, it is observed that the modeling of buoyant flows still presents uncertainties and that additional work is necessary to properly account for the effect of buoyancy on the production of ε and the dissipation of g.

scholarly journals A wall-wake model for the turbulence structure of boundary layers. Part 2. Further experimental support

1995 ◽  
Vol 298 ◽  
pp. 389-407 ◽  
Author(s):  
Ivan Marušić ◽  
A. E. Perry
Keyword(s):  
Boundary Layers ◽  
Cone Angle ◽  
Power Spectra ◽  
Turbulent Boundary Layers ◽  
Turbulence Structure ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Equilibrium Pressure ◽  
Extended Theory ◽  
Wake Model

In Part 1 an extension of the attached eddy hypothesis was developed and applied to equilibrium pressure gradient turbulent boundary layers. In this paper the formulation is applied to data measured by the authors from non-equilibrium layers and agreement with the extended theory is encouraging. Also power spectra of the Reynolds stresses as developed from the extended theory compare favourably with experiment. The experimental data include a check of cone-angle effects by using a flying hot wire.

Homogeneity of turbulence generated by static-grid structures

2010 ◽  
Vol 654 ◽  
pp. 473-500 ◽  
Author(s):  
Ö. ERTUNÇ ◽  
N. ÖZYILMAZ ◽  
H. LIENHART ◽  
F. DURST ◽  
K. BERONOV
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Numerical Simulations ◽  
Direct Numerical Simulations ◽  
Uniform Grid ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Mean Velocity ◽  
Wide Range ◽  
The Mean

Homogeneity of turbulence generated by static grids is investigated with the help of hot-wire measurements in a wind-tunnel and direct numerical simulations based on the Lattice Bolztmann method. It is shown experimentally that Reynolds stresses and their anisotropy do not become homogeneous downstream of the grid, independent of the mesh Reynolds number for a grid porosity of 64%, which is higher than the lowest porosities suggested in the literature to realize homogeneous turbulence downstream of the grid. In order to validate the experimental observations and elucidate possible reasons for the inhomogeneity, direct numerical simulations have been performed over a wide range of grid porosity at a constant mesh Reynolds number. It is found from the simulations that the turbulence wake behind the symmetric grids is only homogeneous in its mean velocity but is inhomogeneous when turbulence quantities are considered, whereas the mean velocity field becomes inhomogeneous in the wake of a slightly non-uniform grid. The simulations are further analysed by evaluating the terms in the transport equation of the kinetic energy of turbulence to provide an explanation for the persistence of the inhomogeneity of Reynolds stresses far downstream of the grid. It is shown that the early homogenization of the mean velocity field hinders the homogenization of the turbulence field.

Modeling Turbulent Wall Flows Subjected to Strong Pressure Variations

1999 ◽  
Vol 121 (1) ◽  
pp. 57-64 ◽  
Author(s):  
K. Hanjalic´ ◽  
I. Hadzˇic´ ◽  
S. Jakirlic´
Keyword(s):  
Pressure Gradient ◽  
Viscous Sublayer ◽  
Moment Closure ◽  
Wall Friction ◽  
Wall Region ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Second Moment ◽  
Turbulence Closures ◽  
The Mean

Mean pressure gradient affects the turbulence mainly through the modulation of the mean rate of strain. Modification of the turbulence structure feeds, in turn, back into the mean flow. Particularly affected is the near wall region (including the viscous sublayer) where the pressure gradient invalidates the conventional boundary-layer “equilibrium” assumptions and inner-wall scaling. Accurate predictions of such flows require application of advanced turbulence closures, preferably at the differential second-moment level with integration up to the wall. This paper aims at demonstrating the potential usefulness of such a model to engineers by revisiting some of the recent experimental and DNS results and by presenting a series of computations relevant to low-speed external aerodynamics. Several attached and separated flows, subjected to strong adverse and favorable pressure gradient, as well as to periodic alternation of the pressure gradient sign, all computed with a low-Re-number second-moment closure, display good agreement with experimental and DNS data. It is argued that models of this kind (in full or a truncated form) may serve both for steady or transient Reynolds-Averaged Navier-Stokes (RANS, TRANS) computations of a variety of industrial and aeronautical flows, particularly if transition phenomena, wall friction, and heat transfer are in focus.

Turbulence Measurements Near the Stern of a Ship Model

1984 ◽  
Vol 28 (03) ◽  
pp. 186-201
Author(s):  
Lennart Löfdahl ◽  
Lars Larsson
Keyword(s):  
Boundary Layer ◽  
Strong Influence ◽  
Three Dimensional ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Calculation Methods ◽  
Mean Velocity ◽  
Ship Model ◽  
The Mean ◽  
Stress Profiles

An experimental investigation in which Reynolds stress profiles were measured in the thick three-dimensional turbulent boundary layer at the stern of a ship model has been carried out. The measurements were performed using a specially developed hot-wire technique in which the mean velocity component perpendicular to the surface was considered. A large number of results are given in diagrams, and an error estimation for the different Reynolds stresses is presented. Efforts have been made, when positioning the measured turbulence profiles, to enable future development of calculation methods based on these results. The measured profiles have revealed a strong influence of streamline convergence (divergence) on the Reynolds stresses. Also, the effects of wall curvature are of importance, and since most parts of the investigated region have a convex curvature the average level of the stresses is reduced.

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