Some Corrections to the Linearized Response of a Constant-Temperature Hot-Wire Anemometer Operated in a Low-Speed Flow

1962 ◽  
Vol 29 (3) ◽  
pp. 554-558 ◽  
Author(s):  
W. G. Rose
Keyword(s):  
Shear Stress ◽  
Constant Temperature ◽  
Flow Direction ◽  
Turbulent Intensity ◽  
Order Effects ◽  
Fluid Temperature ◽  
Hot Wire ◽  
Mean Velocity ◽  
Low Speed ◽  
Speed Flow

An equation is obtained for the instantaneous response of a constant-temperature hot-wire anemometer having a linearized output. The result includes the second-order effects of variations in fluid temperature and in flow direction. Corrected equations for outputs in terms of mean velocity, turbulent-intensity components, and shear stress are derived from the instantaneous response.

Measurements with a pulsed-wire and a hot-wire anemometer in the highly turbulent wake of a normal flat plate

1976 ◽  
Vol 77 (3) ◽  
pp. 473-497 ◽  
Author(s):  
L. J. S. Bradbury
Keyword(s):  
Turbulent Flow ◽  
Flat Plate ◽  
Flow Direction ◽  
Operating Conditions ◽  
Turbulent Intensity ◽  
Hot Wire ◽  
Mean Flow ◽  
Mean Velocity ◽  
The Mean ◽  
Better Than

This paper describes an investigation into the response of both the pulsed-wire anemometer and the hot-wire anemometer in a highly turbulent flow. The first part of the paper is concerned with a theoretical study of some aspects of the response of these instruments in a highly turbulent flow. It is shown that, under normal operating conditions, the pulsed-wire anemometer should give mean velocity and longitudinal turbulent intensity estimates to an accuracy of better than 10% without any restriction on turbulence level. However, to attain this accuracy in measurements of turbulent intensities normal to the mean flow direction, there is a lower limit on the turbulent intensity of about 50%. An analysis is then carried out of the behaviour of the hot-wire anemometer in a highly turbulent flow. It is found that the large errors that are known to develop are very sensitive to the precise structure of the turbulence, so that even qualitative use of hot-wire data in such flows is not feasible. Some brief comments on the possibility of improving the accuracy of the hot-wire anemometer are then given.The second half of the paper describes some comparative measurements in the highly turbulent flow immediately downstream of a normal flat plate. It is shown that, although it is not possible to interpret the hot-wire results on their own, it is possible to calculate the hot-wire response with a surprising degree of accuracy using the results from the pulsed-wire anemometer. This provides a rather indirect but none the less welcome check on the accuracy of the pulsed-wire results, which, in this very highly turbulent flow, have a certain interest in their own right.

Hot-wire probes in low speed flow

1979 ◽  
Vol 18 ◽  
pp. 271-323 ◽  
Author(s):  
J.-D. Vagt
Keyword(s):  
Hot Wire ◽  
Low Speed ◽  
Speed Flow

Calibration of Constant-Temperature Hot-Wire Anemometers at Low Velocities in Water with Variable Fluid Temperature

1972 ◽  
Vol 94 (1) ◽  
pp. 17-22 ◽  
Author(s):  
K. Hollasch ◽  
B. Gebhart
Keyword(s):  
Experimental Study ◽  
Natural Convection ◽  
Constant Temperature ◽  
Fluid Temperature ◽  
Hot Wire ◽  
Temperature Variations ◽  
Wire Probe ◽  
Temperature Mode

Calibration of hot-wire probes operated in a constant-temperature mode in water at low velocities is discussed. Operation under circumstances where natural convection effects are important is considered. A method of calibrating a constant-temperature hot-wire probe for variations in fluid temperature is presented. The method consists of varying wire overheat during calibration at a constant fluid temperature. A relation is derived analytically relating anemometer output with a variable overheat resistance to anemometer output with fluid temperature variations. An experimental study to verify the analysis is presented.

Measurement of turbulence quantities in a two-stream mixing layer

1978 ◽  
Vol 89 (4) ◽  
pp. 709-722 ◽  
Author(s):  
M. Saiy ◽  
S. J. Peerless
Keyword(s):  
Shear Stress ◽  
Wind Tunnel ◽  
Mixing Layer ◽  
Measuring System ◽  
Hot Wire ◽  
Mean Velocity ◽  
Plane Mixing Layer ◽  
Air Streams

Measurements have been made of the time-mean velocity, all three fluctuating velocity components and the turbulence shear stress in the plane mixing layer produced in an open wind tunnel between two nominally parallel air streams with fairly low turbulence levels. The hot-wire measuring system is described, the evaluation equations derived and the principal results presented.

Measurement of Intake Valve/Cylinder Boundary Flows Using a Multiple Orientation Hot-Wire Technique

1988 ◽  
Vol 110 (4) ◽  
pp. 361-366 ◽  
Author(s):  
T. C. Wagner ◽  
J. C. Kent
Keyword(s):  
Flow Direction ◽  
Sequential Sampling ◽  
Effective Area ◽  
Flow Speed ◽  
Intake Valve ◽  
Hot Wire ◽  
Mean Velocity ◽  
Local Flow ◽  
Discharge Coefficients ◽  
Velocity Magnitude

A new measurement method is utilized to determine velocity distributions on the intake-valve/cylinder boundary for different induction system designs. The velocity information is being used to calculate the angular momentum flux and to define local discharge coefficients around the valve periphery. The contribution of local flow direction (effective area) and local flow speed (velocity losses) to the global discharge coefficients is examined. The dependence of the discharge coefficient on the flow direction and mean velocity magnitude provides useful diagnostic data to relate intake port geometry and flow performance. The measurement technique is also described in detail. The directional response of a single hot-wire anemometer is utilized along with sequential sampling of the signal as the probe shaft is rotated through 360 deg. Within the range of velocity and flow direction required, the velocity magnitude and direction can be determined to within 2 percent and 2 deg, respectively.

The Measurements of Mean Flow Angles Between an Automotive Fan and Stator

2002 ◽  
Author(s):  
Gregory A. Kopp ◽  
Robert J. Martinuzzi
Keyword(s):  
Flow Direction ◽  
Leading Edge ◽  
Laser Doppler Velocimeter ◽  
Hot Wire ◽  
Mean Flow ◽  
Mean Velocity ◽  
Flow Angle ◽  
Automotive Engine ◽  
Engine Cooling ◽  
The Mean

Measurements of the mean velocity vector were conducted to determine the exit angle from an automotive engine cooling fan module. The measurements were made at 15 locations along a radius between the hub and the band. The radius investigated was located in a plane roughly half-way between the blade trailing edge and stator leading edge. A two-component laser Doppler velocimeter and a four-wire hot-wire probe were used to measure the flow fields. It was found that the results obtained from hot-wire anemometry will have significant bias errors when used to measure the velocity vectors between the fan and the stator unless phase-averaged data are obtained with the probe re-oriented by phase. The differences between the techniques occur because the distribution of instantaneous swirl angles is bi-modal. Further, the mean flow angle is close to a local minimum in the probability density function of the swirl angle. This will act to increase errors in measurement devices whose accuracy depends on flow direction (the quantity being measured) such as five-hole probes which are used in industry.

scholarly journals AERODYNAMICS AND AEROACOUSTICS SURVEY FOR A LOW SPEED SUBSONIC JET OPERATING AT MACH 0.25

2014 ◽  
Vol 13 (2) ◽  
pp. 33
Author(s):  
A. R. Proença ◽  
O. De almeida ◽  
R. H. Self
Keyword(s):  
Pitot Tube ◽  
Hot Wire ◽  
Mean Velocity ◽  
Low Speed ◽  
Free Jet ◽  
Acoustic Signature ◽  
Total Noise ◽  
Subsonic Regime ◽  
The Mean

The purpose of this work is to study and characterize, in laboratory, the aerodynamics of a free jet operating at subsonic regime and identify its acoustic signature. This study aims to analyze the fundamental role of turbulent flow structures in the total noise produced at different Mach numbers. This work is focused at low speed subsonic jets operating at Mach number 0.25. The research is done by analyzing the data obtained in experiments using Pitot tube, hot-wire anemometer and acoustic measurements. This work also describes the experimental procedures for each step of analysis, as well as the characteristics of jet noise facility. The data from measurements with Pitot tube is used to study the mean velocity profiles. The average properties are also analyzed with anemometry system, likewise used to study the turbulent intensity of eleven axial lines, ranging from the center line to the edge of the nozzle (lipline). These results are compared with the literature and is verified the accuracy of hot-wire anemometers for turbulent intensities lower than 15%. A database with the sound pressure level as a function of frequency is constructed from experiments serving as data for further numerical analysis to solve this problem.

An Unsteady Flow Wind Tunnel

1974 ◽  
Vol 25 (2) ◽  
pp. 81-90 ◽  
Author(s):  
J H Horlock
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow ◽  
Free Stream ◽  
Flow Direction ◽  
Axial Flow ◽  
Mean Velocity ◽  
Low Speed ◽  
The Mean ◽  
Low Speed Wind Tunnel

SummaryA novel low-speed wind tunnel which produces unsteady “gust” flows is described. The walls are sinusoidal in shape and are moved in the flow direction with a velocity Wwless than the mean velocity Wmof the free stream. The tunnel is useful for testing isolated aerofoils and aerofoils in cascade in non-convective gusts (Ww< Wm) so that comparisons with predictions by thin aerofoil theory may be made. However, it does not simulate precisely the unsteady flow that occurs in axial flow turbomachines.

scholarly journals Significance of Slippage and Electric Field in Mucociliary Transport of Biomagnetic Fluid

Lubricants ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 48
Author(s):  
Sufian Munawar
Keyword(s):  
Shear Stress ◽  
Flow Direction ◽  
Pressure Rise ◽  
Physical Parameters ◽  
Slippage Effect ◽  
Channel Surface ◽  
Electro Osmosis ◽  
Biomagnetic Fluid ◽  
Velocity Pressure ◽  
Metachronal Waves

Shear stress at the cilia wall is considered as an imperative factor that affects the efficiency of cilia beatings as it describes the momentum transfer between the fluid and the cilia. We consider a visco-inelastic Prandtl fluid in a ciliated channel under electro-osmotic pumping and the slippage effect at cilia surface. Cilia beating is responsible for the stimulation of the flow in the channel. Evenly distributed cilia tend to move in a coordinated rhythm to mobilize propulsive metachronal waves along the channel surface by achieving elliptic trajectory movements in the flow direction. After using lubrication approximations, the governing equations are solved by the perturbation method. The pressure rise per metachronal wavelength is obtained by numerically integrating the expression. The effects of the physical parameters of interest on various flow quantities, such as velocity, pressure gradient, pressure rise, stream function, and shear stress at the ciliated wall, are discussed through graphs. The analysis reveals that the axial velocity is enhanced by escalating the Helmholtz–Smoluchowski velocity and the electro-osmosis effects near the elastic wall. The shear stress at the ciliated boundary elevates with an increase in the cilia length and the eccentricity of the cilia structure.

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