A Spectral Study of a Moderately Loaded LPT Airfoil: Part 1—Identifying Frequencies Affecting By-Pass Transition

2012 ◽  
Author(s):  
J. R. S. Graveline ◽  
S. A. Sjolander
Keyword(s):  
Boundary Layer ◽  
Spectral Analysis ◽  
Boundary Layer Thickness ◽  
Hot Wire ◽  
Airflow Velocity ◽  
Single Wire ◽  
Low Pressure Turbine ◽  
Wire Probe ◽  
Empirical Relations ◽  
Tollmien Schlichting

A single wire, hot-wire, probe is used to examine the airflow in, and in close vicinity to, the shearlayer of a Low-Pressure Turbine (LPT) airfoil. A spectral analysis of the data identifies two sets of wide peaks of turbulent kinetic energy, one near 200 Hz and a second near 1 kHz. A method is developed to identify these peaks based on a combination of empirical relations between the airflow velocity and boundary layer thickness and on the location of the frequency peaks relative to the state of the free shearlayer as it transitioned from laminar to turbulent. The method suggests the presence of Tollmien-Schlichting waves and Kelvin-Helmholtz instabilities. The Kelvin-Helmholtz instabilities are shown to pair.

A Spectral Study of a Moderately Loaded Low-Pressure Turbine Airfoil—Part I: Identifying Frequencies Affecting Bypass Transition

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
J. R. S. Graveline ◽  
S. A. Sjolander
Keyword(s):  
Shear Layer ◽  
Low Pressure ◽  
Bypass Transition ◽  
Free Shear Layer ◽  
Airflow Velocity ◽  
Single Wire ◽  
Low Pressure Turbine ◽  
Wire Probe ◽  
Empirical Relations ◽  
Tollmien Schlichting

A single wire, hot-wire, probe is used to examine the airflow in, and in close vicinity to, the shear layer of a low-pressure turbine (LPT) airfoil. A spectral analysis of the data identifies two sets of wide peaks of turbulent kinetic energy, one near 200 Hz and a second near 1 kHz. A method is developed to identify these peaks based on a combination of empirical relations between the airflow velocity and boundary layer thickness and on the location of the frequency peaks relative to the state of the free shear layer as it transitioned from laminar to turbulent. The method suggests the presence of Tollmien–Schlichting waves and Kelvin–Helmholtz instabilities. The Kelvin–Helmholtz instabilities are shown to pair.

A Spectral Study of a Moderately Loaded LPT Airfoil: Part 2—Effects of Turbulence Intensity and Reynolds Number on Frequencies Affecting By-Pass Transition

2012 ◽  
Author(s):  
J. R. S. Graveline ◽  
S. A. Sjolander
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Spectral Study ◽  
Reynolds Numbers ◽  
Hot Wire ◽  
Spectral Measures ◽  
Single Wire ◽  
Low Pressure Turbine ◽  
Wire Probe ◽  
Tollmien Schlichting

A single wire, hot-wire, probe is used to examine the airflow in, and in close vicinity to, the shearlayer of a Low-Pressure Turbine (LPT) airfoil. The experiment was performed with varying turbulence intensities (Tu) and Reynolds numbers (ReBx); in this work, Re is based on the cascade inflow velocity and axial chord length. In part 1 of the present study [1], the methodology used to identify the key frequencies in the free shearlayer using a combination of statistical and spectral measures of the airflow was first discussed. Here, the focus is on the effects of ReBx and Tu on the spectral results. The frequencies and location in the shearlayer of the Tollmien-Schlichting (TS) waves and Kelvin-Helmholtz (KH) instabilities are shown to be affected by both Tu and ReBx. Additionally, the KH instabilities are shown to undergo pairing.

Revisiting hot-wire anemometer measurement of Tollmien–Schlichting waves on a flat plate

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040095
Author(s):  
Xianyang Jiang
Keyword(s):  
Boundary Layer ◽  
Electromagnetic Interference ◽  
High Speed ◽  
Boundary Layer Transition ◽  
Hot Wire ◽  
S Wave ◽  
Layer Transition ◽  
S Waves ◽  
Wire Probe ◽  
Tollmien Schlichting

The amplification of Tollmien–Schlichting (T-S) wave plays an important role in the process of boundary-layer transition. This paper investigates the measurement of T-S wave using hot-wire anemometer (HWA) in a wind tunnel. To precisely acquire T-S wave, the vibration of hot-wire probe and the influence of electromagnetic interference (EMI) are considered. By introducing different amplitudes and frequencies of vibration ribbon, the development of T-S waves is obtained. Lift-up of low-speed fluid and downward of high-speed fluid are observed during the transition.

A Multi-Sensor Hot-Wire Probe to Measure Vorticity and Velocity in Turbulent Flows

1989 ◽  
Vol 111 (2) ◽  
pp. 220-224 ◽  
Author(s):  
P. Vukoslavc˘evic´ ◽  
J.-L. Balint ◽  
J. M. Wallace
Keyword(s):  
Boundary Layer ◽  
Measurement Error ◽  
Turbulent Boundary Layer ◽  
Turbulent Flows ◽  
Hot Wire ◽  
Preliminary Testing ◽  
Wire Probe ◽  
Vorticity Fluctuation ◽  
Design And Construction

The design and construction of a miniature hot-wire probe capable of simultaneously measuring all components of the velocity and vorticity vectors in turbulent flows are presented. A brief description of the probe resolution and calibration as well as the procedure to solve the cooling equations are given. Preliminary testing in the irrotational region of the flow shows that the spurious vorticity obtained from the probe due to system measurement error does not exceed 8 percent of the RMS vorticity fluctuation levels measured over the region y+ = 15 − 45 in a turbulent boundary layer.

scholarly journals Studies on Wake-Disturbed Boundary Layers Under the Influences of Favorable Pressure Gradient and Free-Stream Turbulence: Part II — Effect of Free-Stream Turbulence

1997 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Takashi Kitazawa ◽  
Kazuyuki Koizumi ◽  
Tadashi Tanuma
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Free Stream ◽  
Transition Model ◽  
Hot Wire ◽  
Time Resolved ◽  
Free Stream Turbulence ◽  
Wire Probe ◽  
Favorable Pressure Gradient ◽  
Probe Measurements

This paper, as Part II of the study on wake-disturbed boundary layer, is aimed at investigation of the effects of free-stream turbulence on wake-induced transition of the boundary layer under a favorable pressure gradient. Hot-wire probe measurements are also made on the wake-disturbed boundary layer to obtain ensemble-averaged shape factor contours on the distance-time diagrams. These data are then used to examine how the favorable pressure gradient and the free-stream turbulence affects time-resolved behaviors of the boundary layer subjected to periodic wakes. In addition, likewise in Part I, the heat transfer data are compared with the transition model proposed by Funazaki (1996) in order to check the capability of the model under the favorable pressure gradient as well as the free-stream turbulence.

Instability and Breakdown of a Zero Net Mass-Flux Jet in a Blasius Boundary Layer

2009 ◽  
Author(s):  
Jonathan H. Watmuff
Keyword(s):  
Boundary Layer ◽  
Mass Flux ◽  
Three Dimensional ◽  
Base Flow ◽  
Hot Wire ◽  
Control Applications ◽  
Blasius Boundary Layer ◽  
Tollmien Schlichting ◽  
Laminar Flow Control ◽  
Zero Net Mass Flux

Hot–wire measurements reveal the evolution of three-dimensional TS (Tollmien-Schlichting) waves and other nonlinear disturbances generated by a ZNMF (Zero Net Mass-Flux) jet. The base flow consists of a highly two-dimensional Blasius boundary layer with extremely small extraneous background disturbance levels (u/U1 < 0.08 %). The response is shown to be linear and symmetrical for sufficiently small actuator amplitudes and under these conditions the TS wave motions conform with the PSE (Parabolized Stability Equations) results of Mack & Herbert (1995). The observations suggest that a small-amplitude ZNMF jet would be a suitable device for active LFC (Laminar Flow Control) applications. For larger actuator amplitudes, other short–wavelength instabilities develop and grow with streamwise development and they ultimately breakdown to form a turbulent wedge. There is an actuator amplitude threshold below which these instabilities do not form, and a larger threshold below which the instabilities do not grow with streamwise development. The characteristics of the turbulent wedge are also considered in some detail.

The effect of endwall boundary layer and incoming wakes on secondary flow in a high-lift low-pressure turbine cascade at low Reynolds number

2019 ◽  
Vol 233 (15) ◽  
pp. 5637-5649 ◽  
Author(s):  
Xiao Qu ◽  
Yanfeng Zhang ◽  
Xingen Lu ◽  
Zhijun Lei ◽  
Junqiang Zhu
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Passage Vortex ◽  
Secondary Vortices

The endwall flow features are heavily dependent on the incoming boundary layer. It was particularly important to increase understanding the effect of inlet boundary layer thickness on endwall secondary flow under unsteady conditions. In present study, the influences of incoming wakes and various boundary layer thickness on endwall secondary flow were studied in a typical high-lift low-pressure turbine cascade, numerical calculation and experiment measurement of seven-hole probe were adopted at Re = 25,000 (based on the inlet velocity and the axial chord). Upstream wakes were simulated through moving rods upstream of the cascade. Detailed analysis was focused on the mechanisms of periodic wake influencing on the endwall vortex structures under thick endwall boundary layer condition. Influences of two different endwall boundary layer thickness on endwall secondary vortices structures were also comparatively analyzed. Under steady condition without wake, although thick incoming boundary layer reduces the cross-passage pressure gradient near endwall, more low momentum fluid inside thick endwall boundary layer is drawn into secondary vortices, finally resulting in stronger the pressure side leg of the leading edge horseshoe vortex and passage vortex, compared to the results of thin boundary layer condition. Under unsteady condition with thick inlet boundary layer, the “negative jet” effect of incoming wakes delays intersection of pressure side leg and suction side leg of leading edge horseshoe vortex on blade suction surface. The time-averaged strength of passage vortex and counter vortex core decreases by about 32%, and the underturning and overturning of endwall secondary flow is suppressed. The instantaneous results also indicate the endwall secondary vortices are reduced periodically at the position of wakes passing.

Studies on Insertion Effects of Hot-Wire Probe upon the Velocity Measurement of Boundary Layer with Separation and Reattachment

2019 ◽  
Vol 2019 (0) ◽  
pp. OS6-08
Author(s):  
Takato SOMA ◽  
Yusuke FUJITA ◽  
Hideo TANIGUCHI ◽  
Ken-ichi FUNAZAKI ◽  
Takahisa NAGAO ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Velocity Measurement ◽  
Hot Wire ◽  
Wire Probe

The Application of Different Tripping Techniques to Determine the Characteristics of the Turbulent Boundary Layer Over a Flat Plate

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Anton Silvestri ◽  
Farzin Ghanadi ◽  
Maziar Arjomandi ◽  
Benjamin Cazzolato ◽  
Anthony Zander
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flat Plate ◽  
Boundary Layer Thickness ◽  
Reynolds Numbers ◽  
Wind Tunnels ◽  
Hot Wire ◽  
Flow Speeds ◽  
Different Diameters ◽  
Insight Into

In the present study, the optimal two-dimensional (2D) tripping technique for inducing a naturally fully developed turbulent boundary layer in wind tunnels has been investigated. Various tripping techniques were tested, including wires of different diameters and changes in roughness. Experimental measurements were taken on a flat plate in a wind tunnel at a number of locations along the flat plate and at a variety of flow speeds using hot-wire anemometry to measure the boundary layer resulting from each tripping method. The results have demonstrated that to produce a natural turbulent boundary layer using a 2D protuberance, the height of the trip must be less than the undisturbed boundary layer thickness. Using such a trip was shown to reduce the development length of the turbulent boundary layer by approximately 50%. This was shown to hold true for all Reynolds numbers investigated (Rex=1.2×105−1.5×106). The present study provides an insight into the effect of the investigated trip techniques on the induced transition of a laminar boundary layer into turbulence.

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