scholarly journals Hot-Wire Anemometer for the Boundary Layer Data System

2012 ◽  
Author(s):  
William D Neumeister
Keyword(s):  
Boundary Layer ◽  
Data System ◽  
Hot Wire

Turbulence structure of a reattaching mixing layer

1981 ◽  
Vol 110 ◽  
pp. 171-194 ◽  
Author(s):  
C. Chandrsuda ◽  
P. Bradshaw
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Reynolds Shear Stress ◽  
Mixing Layer ◽  
Three Dimensional ◽  
Flow Region ◽  
Turbulent Energy ◽  
Turbulence Structure ◽  
Hot Wire ◽  
Recirculating Flow

Hot-wire measurements of second- and third-order mean products of velocity fluctuations have been made in the flow behind a backward-facing step with a thin, laminar boundary layer at the top of the step. Measurements extend to a distance of about 12 step heights downstream of the step, and include parts of the recirculating-flow region: approximate limits of validity of hot-wire results are given. The Reynolds number based on step height is about 105, the mixing layer being fully turbulent (fully three-dimensional eddies) well before reattachment, and fairly close to self-preservation in contrast to the results of some previous workers. Rapid changes in turbulence quantities occur in the reattachment region: Reynolds shear stress and triple products decrease spectacularly, mainly because of the confinement of the large eddies by the solid surface. The terms in the turbulent energy and shear stress balances also change rapidly but are still far from the self-preserving boundary-layer state even at the end of the measurement region.

Separation in oscillating laminar boundary-layer flows

1971 ◽  
Vol 47 (1) ◽  
pp. 21-31 ◽  
Author(s):  
R. A. Despard ◽  
J. A. Miller
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Reverse Flow ◽  
Oscillation Amplitude ◽  
Hot Wire ◽  
Boundary Layer Flows ◽  
Laminar Boundary Layers ◽  
History Of

The results of an experimental investigation of separation in oscillating laminar boundary layers is reported. Instantaneous velocity profiles obtained with multiple hot-wire anemometer arrays reveal that the onset of wake formation is preceded by the initial vanishing of shear at the wall, or reverse flow, throughout the entire cycle of oscillation. Correlation of the experimental data indicates that the frequency, Reynolds number and dynamic history of the boundary layer are the dominant parameters and oscillation amplitude has a negligible effect on separation-point displacement.

An experiment on the stability of hypersonic laminar boundary layers

1960 ◽  
Vol 7 (3) ◽  
pp. 385-396 ◽  
Author(s):  
Anthony Demetriades
Keyword(s):  
Boundary Layer ◽  
Flat Surface ◽  
Hypersonic Boundary Layer ◽  
Natural Disturbances ◽  
Hot Wire ◽  
Amplitude Variation ◽  
Laminar Boundary Layers ◽  
Boundary Layer Instability ◽  
The Stability ◽  
Maximum Amplification

An experimental investigation of the hydrodynamic stability of the laminar hypersonic boundary layer was carried out with the aid of a hot-wire anemometer. The case investigated was that of a flat surface at zero angle of attack and no heat transfer.The streamwise amplitude variation of both natural disturbances and of disturbances artifically excited with a siren mechanism was studied. In both cases it was found that such small fluctuations amplify for certain ranges of frequency and Reynolds number Rθ, and damp for others. The demarcation boundaries for the amplification (instability) zone were found to resemble the corresponding limits of boundary-layer instability at lower speeds. A ‘line of maximum amplification’ of disturbances was also found. The amplification rates and hence the degree of selectivity of the hypersonic layer were found, however, to be considerably lower than those at the lower speeds. The disturbances selected by the layer for maximum amplifications have a wavelength which was estimated to be about twenty times the boundary-layer thickness δ.

Statistical Analysis of Nonlinear Processes on a Porous Surface in a Hypersonic Boundary Layer

2009 ◽  
Vol 4 (3) ◽  
pp. 43-49
Author(s):  
Dmitriy Buntin ◽  
Anatoliy Maslov ◽  
Timur Chimytov ◽  
Aleksandr Shiplyuk
Keyword(s):  
Boundary Layer ◽  
Statistical Analysis ◽  
Porous Surface ◽  
Transition To Turbulence ◽  
Hypersonic Boundary Layer ◽  
Hot Wire ◽  
Turbulent Transition ◽  
Hypersonic Wind Tunnel ◽  
Sharp Cone ◽  
Skewness And Kurtosis

Experimental investigation of nonlinear stage of the transition to turbulence in a hypersonic boundary layer is presented. The experiments were carried out in a hypersonic wind tunnel T-326 at the Institute of theoretical and applied mechanics SB RAS. The model was a sharp cone with porous surface. Using the statistical analysis of the signals obtained by means of hot-wire it was shown that skewness and kurtosis distribution in a boundary layer on both solid and porous surface are in a qualitative agreement. At the same time the growing of skewness and kurtosis on a porous surface was shown. Analysis of mean voltage and rms voltage pulsation profiles of the hot-wire sensors showed that there is a delay of the laminar-turbulent transition on a porous surface.

scholarly journals Simplified Calibration Method for Constant-Temperature Hot-Wire Anemometry

2020 ◽  
Vol 10 (24) ◽  
pp. 9058
Author(s):  
Hidemi Takahashi ◽  
Mitsuru Kurita ◽  
Hidetoshi Iijima ◽  
Seigo Koga
Keyword(s):  
Boundary Layer ◽  
Flow Velocity ◽  
Constant Temperature ◽  
Calibration Method ◽  
Large Temperature ◽  
Velocity Data ◽  
Hot Wire ◽  
Temperature Variations ◽  
Wire Temperature ◽  
Hot Wire Anemometry

This study proposes a unique approach to convert a voltage signal obtained from a hot-wire anemometry to flow velocity data by making a slight modification to existing temperature-correction methods. The approach was a simplified calibration method for the constant-temperature mode of hot-wire anemometry without knowing exact wire temperature. The necessary data are the freestream temperature and a set of known velocity data which gives reference velocities in addition to the hot-wire signal. The proposed method was applied to various boundary layer velocity profiles with large temperature variations while the wire temperature was unknown. The target flow velocity was ranged between 20 and 80 m/s. By using a best-fit approach between the velocities in the boundary layer obtained by hot-wire anemometry and by the pitot-tube measurement, which provides reference data, the unknown wire temperature was sought. Results showed that the proposed simplified calibration approach was applicable to a velocity range between 20 and 80 m/s and with temperature variations up to 15 °C with an uncertainty level of 2.6% at most for the current datasets.

New perspectives on the impulsive roughness-perturbation of a turbulent boundary layer

2011 ◽  
Vol 677 ◽  
pp. 179-203 ◽  
Author(s):  
I. JACOBI ◽  
B. J. McKEON
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flow Field ◽  
Spectral Energy ◽  
Internal Layers ◽  
Hot Wire ◽  
Mean Velocity ◽  
Composite Maps ◽  
Downstream Flow ◽  
Near Wall

The zero-pressure-gradient turbulent boundary layer over a flat plate was perturbed by a short strip of two-dimensional roughness elements, and the downstream response of the flow field was interrogated by hot-wire anemometry and particle image velocimetry. Two internal layers, marking the two transitions between rough and smooth boundary conditions, are shown to represent the edges of a ‘stress bore’ in the flow field. New scalings, based on the mean velocity gradient and the third moment of the streamwise fluctuating velocity component, are used to identify this ‘stress bore’ as the region of influence of the roughness impulse. Spectral composite maps reveal the redistribution of spectral energy by the impulsive perturbation – in particular, the region of the near-wall peak was reached by use of a single hot wire in order to identify the significant changes to the near-wall cycle. In addition, analysis of the distribution of vortex cores shows a distinct structural change in the flow associated with the perturbation. A short spatially impulsive patch of roughness is shown to provide a vehicle for modifying a large portion of the downstream flow field in a controlled and persistent way.

The Evolution of Streamwise Counter-Rotating Vortices in Flat Plate Boundary Layer With Leading Edge Pattern

2015 ◽  
Author(s):  
Seyed Mohammad Hasheminejad ◽  
Hatsari Mitsudharmadi ◽  
S. H. Winoto ◽  
Kim Boon Lua ◽  
Hong Tong Low
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Plate Boundary ◽  
Leading Edge ◽  
Streamwise Vortex ◽  
Streamwise Velocity ◽  
Stream Velocity ◽  
Hot Wire ◽  
Layer Flow ◽  
Different Characteristics

The evolution of streamwise counter-rotating vortices induced by different leading edge patterns is investigated quantitatively using hot-wire anemometer. A notched and triangular leading edge with the same wavelength and amplitude were designed to induce streamwise vortices over a flat plate at Reynolds number (based on the wavelength of the leading edge patterns) of 3080 corresponding to free-stream velocity of 3 m/s. The streamwise velocity at different streamwise locations collected and analyzed using a single wire probe hot-wire anemometer showed reveal different characteristics of boundary layer flow due to the presence of these two leading edge patterns. The major difference is the appearance of an additional streamwise vortex between the troughs of the notched pattern. Such vortices increase the mixing effect in the boundary layer as well as the velocity profile.

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