Characteristics of the near wake of a compressor or fan rotor blade

Reynolds, B.; Lakshminarayana, B.; Ravindranath, A.

doi:10.2514/6.1978-1141

Cited by 12 publications

(17 citation statements)

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“…At the wake center, near the trailing-edge region, the turbulence intensity terms dominate (as reported by Ravindranath and Lakshminarttyana,l980) and hence the static pressure gradients can exist even in the absence of curvature R,: Qualitative analysis of this effect is given by Reynolds et al (1979).…”

Section: Pressure Variation Across the Wakementioning

confidence: 76%

“…Numerical codes have been successfully employed to predict rotor flow fields but experimental data is needed not only to validate these codes but also to contribute to the data base and ultimately a more complete understanding of the flow fields in turbomachinery. Most recent attempts at rotor wake flow field measurement has been conducted by Reynolds et al, 1979, Dring, et al, 1982Hirsh, et al, 1978;Ravindranath and Lakshminarayana, 1980;Strazisar, et al, 1989;Gallus, et al, 1982. Of these attempts very few have given a comprehensive survey (three velocity components at an array of axial and radial stations) of the wake at different blade loading: This motivated the research reported in this paper.…”

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confidence: 98%

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Investigation of Compressor Rotor Wake Structure at Peak Pressure Rise Coefficient and Effects of Loading

Prato

Lakshminarayana

1992

Volume 1: Turbomachinery

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This paper reports an experimental study of the three-dimensional characteristics of the mean velocity in the trailing-edge, near-wake and far-wake regions of a highly loaded low-speed compressor rotor. The wake structure and decay characteristics are compared with the wake data in the same compressor with moderate loading. The experimental investigation was carried out using a rotating five-hole probe. The flow field was surveyed at various radial and axial locations downstream of the compressor rotor. Variations in the axial, tangential and radial components of mean velocity at various axial and radial locations were derived from the data and compared with earlier data at lower loading to discern the effects of loading. It was found that the higher loading had the following effects: Higher total velocity defects were observed in the hub-wall region, increased wake growth rate in the tip region, faster decay of static pressure difference in the trailing-edge region, larger initial wake width in the trailing-edge region, increased rate of growth of the semi-wake width in the trailing-edge region, increased decay rate of radial velocity in the trailing-edge region and decreased decay rate of the radial velocity in the far-wake region. Far wake properties were almost identical in both cases.

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Section: Pressure Variation Across the Wakementioning

confidence: 76%

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confidence: 98%

Investigation of Compressor Rotor Wake Structure at Peak Pressure Rise Coefficient and Effects of Loading

Prato

Lakshminarayana

1992

Volume 1: Turbomachinery

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“…Narasimha and Prabhu [3] focused on the relaxation to equilibrium of a similar low-speed turbulent wake. Low-speed rotor wake flows have been investigated by Reynolds, et al [4], and by Lakshminarayana and Davino [5]. One of their principal observations was the existence of significant spanwise flow velocities which alter the turbulence properties relative to 2-D cascade wakes.…”

Section: Introductionmentioning

confidence: 99%

Turbulence Characteristics in a Supersonic Cascade Wake Flow

Andrew

1993

Volume 3C: General

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The turbulent character of the supersonic wake of a linear cascade of fan airfoils has been studied using a two–component Laser Doppler Anemometer. The cascade was tested in the Virginia Polytechnic Institute and State University intermittent wind tunnel facility, where the Mach and Reynolds numbers were 2.36 and 4.8 × 106, respectively. In addition to mean flow measurements, Reynolds normal and shear stresses were measured as functions of cascade incidence angle and streamwise locations spanning the near–wake and the far–wake. The extremities of profiles of both the mean and turbulent wake properties were found to be strongly influenced by upstream shock–boundary–layer–interactions, the strength of which varied with cascade incidence. In contrast, the peak levels of turbulence properties within the shear layer were found to be largely independent of incidence, and could be characterized in terms of the streamwise position only. The velocity defect turbulence level was found to be 23%, and the generally–accepted value of the turbulence structural coefficient of 0.30 was found to be valid for this flow. The degree of similarity of the mean flow wake profiles was established, and those profiles demonstrating the most similarity were found to approach a state of equilibrium between the mean and turbulent properties. In general, this wake flow may be described as a classical free shear flow, upon which the influence of upstream shock–boundary–layer–interactions has been superimposed.

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“…The authors have analyzed the variation of higher Fourier coefficients up to A 7 and have found for the two sets of rotors [1,2] that the predominant harmonics are up to A 5 in the trailing-edge and nearwake regions and only the first two in the far-wake region.…”

Section: Author's Closurementioning

confidence: 99%

Discussion: “Mean Velocity and Decay Characteristics of the Near and Far-Wake of a Compressor Rotor Blade of Moderate Loading” (Ravindranath, A., and Lakshminarayana, B., 1980, ASME J. Eng. Power, 102, pp. 535–547)

Okiishi

1980

Journal of Engineering for Power

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normalized wake. The average values of the harmonics are shown in Fig-26 for the authors' data. Fig. 26 shows the plot of the scatter in the first four coefficients for the data under consideration. The Fourier curve correlated quite well with the data when the first four coefficients were considered in the analysis, with the correlation coefficient for the entire wake being about 0.998. ConclusionsThe measurements reported in this paper represent the first set of data in the trailing-edge region of a moderately-loaded compressor rotor blade. The results reveal the highly three-dimensional nature of the rotor-wake, with radial velocities dominating the flow in the trailing-edge region. It is also seen that the effect of loading has a substantial influence on the wake width and the decay of the velocity defect. Some of the major conclusions of the present investigation are:1 In the trailing-edge region the radial velocities are found to be very large and are influenced by the trailing-vortex system. Large velocity defects are measured in the trailing edge region.2 Higher blade loading results in not only higher velocity defect but also slows down the decay rate. Tangential velocities are found to decay much more rapidly in the trailing-edge region than the other velocity components. In the far-wake region the decay of all the three components of velocities are of the same order. Decay laws are presented for all the velocity components.3 The wake curvature is considerable in the trailing-edge region and beyond 0.2 chords downstream the relative flow angle variation as well as curvature of the wakes become very small. 4 The variation of the wake width with downstream distance is found to be very rapid in the trailing-edge region. In the near-and far-wake the growth is slow.5 Mean velocity profiles in the trailing-edge and near-wake regions are unsymmetrical and tend to become symmetrical in the far-wake region. The effect of loading has been found to sustain the asymmetry to a much longer downstream distance as compared to a lightly loaded case investigated earlier. All the components of velocity become symmetrical and similar when the defect is normalized by its value at the wake center and the lengths by corresponding length scale. All the similarity profiles follow the Gaussian function given by e -0 -693 '; 2 . The wake profiles are also represented by Fourier series. The magnitude of the coefficients decrease rapidly, with the first three coefficients being the dominant ones.6 Static-pressure in the wake is found to increase towards the wake center. The decay of static-pressure difference across the wake is found to be rapid in the trailing-edge region and it slows down in the far-wake region. The static-pressure profiles also exhibit the similarity, except in the trailing-edge region, and the similarity follows the Gaussian distribution, e -0 -693 '' 2 . The discrepancy in the trailingedge region from the Gaussian might be due to the complex interactions of the boundary-layer flow and the trailing-vortex syste...

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Characteristics of the near wake of a compressor or fan rotor blade

Cited by 12 publications

References 5 publications

Investigation of Compressor Rotor Wake Structure at Peak Pressure Rise Coefficient and Effects of Loading

Investigation of Compressor Rotor Wake Structure at Peak Pressure Rise Coefficient and Effects of Loading

Turbulence Characteristics in a Supersonic Cascade Wake Flow

Discussion: “Mean Velocity and Decay Characteristics of the Near and Far-Wake of a Compressor Rotor Blade of Moderate Loading” (Ravindranath, A., and Lakshminarayana, B., 1980, ASME J. Eng. Power, 102, pp. 535–547)

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