Determination of the magnitudes and signs of flow parameters by hot‐wire anemometry. Part I. Measurements using hot‐wire X probes

1989 ◽  
Vol 60 (7) ◽  
pp. 1275-1280 ◽  
Author(s):  
Michael Acrivlellis
Keyword(s):  
Hot Wire ◽  
Flow Parameters ◽  
Hot Wire Anemometry

Accurate Boundary Layer Measurements using Hot-Wire Anemometry - Improvements and Error Analysis

2021 ◽  
pp. 1-15
Author(s):  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Heat Effect ◽  
Correction Term ◽  
Accurate Determination ◽  
Hot Wire ◽  
Static Correction ◽  
Transitional State ◽  
Sensor Position ◽  
Hot Wire Anemometry

Abstract In this paper two approaches are presented dealing with common challenges of 2D boundary layer measurements with hot-wire anemometry under challenging test conditions. Novel procedures for accurate determination of the sensor position and correction of the wall heat effect were developed and tested at high free stream velocities of about M1 = 0.3 and thin boundary layers (δ99 = 0.7 - 3.5 mm) of different transitional state in a low density environment. First of all, a novel procedure for automatized determination of the accurate hot-wire sensor position relative to the wall is presented. The quantification and correction of possible sub-miniature sensor misalignments is achieved by taking advantage of the linear nature of the laminar sub-layer of each boundary layer. The statistical approaches for identification and verification of the linear sub-layer demonstrate satisfying results of minimized position uncertainties of about 24 μm. Secondly, a highly adaptable method for correction of the well-known wall heat effect is presented. In contrary to a series of static correction approaches, the biased velocity information is corrected by optimizing the parameters of an exponential approach, where the correction term is optimized for each boundary layer individually. This novel approach resolves the problem of limited applicability of static correction methods, caused by system inherent measurement uncertainties.

HOT WIRE METHOD FOR DETERMINATION OF THE THERMAL CONDUCTIVITY OF SUGAR CANE FIBERS

2020 ◽  
Author(s):  
Marcelo Borges dos Santos ◽  
CLAUDIA BITTENCOURT ◽  
Ana Carolina Mendonça Mansur ◽  
Luís Mauro Moura ◽  
Carlos Augusto Castro Ferreira
Keyword(s):  
Thermal Conductivity ◽  
Sugar Cane ◽  
Hot Wire ◽  
Wire Method

Hot-wire Anemometry in Low-Density Flows

AIAA Journal ◽  
1971 ◽  
Vol 9 (10) ◽  
pp. 2019-2027 ◽  
Author(s):  
E. M. SCHMIDT ◽  
R. J. CRESCI
Keyword(s):  
Low Density ◽  
Hot Wire ◽  
Hot Wire Anemometry

Flow-Induced Vibration in a Single Row of Cylinders With p/D = 1.26

2021 ◽  
Author(s):  
Roberta F. Neumeister ◽  
Adriane P. Petry ◽  
Sergio V. Möller
Keyword(s):  
Hot Wire ◽  
Flow Induced Vibration ◽  
Single Row ◽  
Reference Flow ◽  
Wake Interaction ◽  
Hot Wire Anemometry ◽  
Tube Banks ◽  
Comparison Of The Results ◽  
The Impact ◽  
Space Ratio

Abstract Crossflow over a row of cylinders with a close space ratio presents an asymmetric configuration with large and narrow wakes behind the cylinders. The wake interaction can impact the vibration response of the cylinders. In tube banks, the impact results in damages to the equipment. The present experimental study aims to analyze the influence of close space observed in a single row of cylinders on the flow-induced vibration. The study compares a single row with fixed cylinders and a single row with one cylinder free to vibrate. The cylinder free to vibrate is tested in four configurations. The study was conducted with an aerodynamic channel with a cross-section of 0.193 × 0.146 m and smooth cylinders with a diameter of 25.1 mm, space ratio is 1.26. The measurements are executed with hot-wire anemometry and accelerometers, for the cases with one cylinder free to vibrate and with hot-wire anemometry and microphones for the case with all fixed cylinders. The Reynolds number ranges between 1.0 × 104 and 4.5 × 104, obtained with the reference flow velocity, measured with a Pitot tube, and the cylinder diameter. The comparison between the wake response for single row fixed and single row and free to vibrate are executed using Fourier transform and Wavelet Transform. The comparison of the results with the models presented in the literature to predict the elastic instability of the fluid in a single row of cylinders is performed.

scholarly journals Estimation of thermal conductivity of short pastry biscuit at different baking stages

2014 ◽  
Vol 45 (2) ◽  
pp. 64 ◽  
Author(s):  
Chiara Cevoli ◽  
Angelo Fabbri ◽  
Simone Virginio Marai ◽  
Enrico Ferrari ◽  
Adriano Guarnieri
Keyword(s):  
Thermal Conductivity ◽  
Thermal Processing ◽  
Physical Property ◽  
Physical Models ◽  
Hot Wire ◽  
Line Heat Source ◽  
Food Material ◽  
Wire Method ◽  
Thermal Conductivity Probe

Thermal conductivity of a food material is an essential physical property in mathematical modelling and computer simulation of thermal processing. Effective thermal conductivity of non-homogeneous materials, such as food matrices, can be determined experimentally or mathematically. The aim of the following research was to compare the thermal conductivity of short pastry biscuits, at different baking stages (60-160 min), measured by a line heat source thermal conductivity probe and estimated through the use of thermo-physical models. The measures were carried out on whole biscuits and on powdered biscuits compressed into cylindrical cases. Thermal conductivity of the compacted material, at different baking times (and, consequently at different moisture content), was then used to feed parallel, series, Krischer and Maxwell-Eucken models. The results showed that the application of the hot wire method for the determination of thermal conductivity is not fully feasible if applied directly to whole materials due to mechanical changes applied to the structure and the high presence of fats. The method works best if applied to the biscuit component phases separately. The best model is the Krischer one for its adaptability. In this case the value of biscuit thermal conductivity, for high baking time, varies from 0.15 to 0.19 Wm<sup>–1</sup> K<sup>–1</sup>, while the minimum, for low baking time, varies from 0.11 to 0.12 Wm<sup>–1</sup> K<sup>–1</sup>. These values are close to that reported in literature for similar products.

Determination of Discharge Coefficient for Ball Valves With Calibrated Inserts

2004 ◽  
Author(s):  
Gino James Rouss ◽  
William S. Janna
Keyword(s):  
Discharge Coefficient ◽  
Polynomial Equation ◽  
The Body ◽  
Orifice Diameter ◽  
Flow Parameters ◽  
Dimensionless Groups ◽  
Order Polynomial ◽  
Experimental Process ◽  
Power Law Equation

The valve coefficient was measured for 1, 1-1/4, 1-1/2 and 2 nominal ball valves. A recently designed orifice insert was used with these valves to obtain smaller valve coefficients. Orifice inserts were threaded into the body of a ball valve just upstream of the ball itself. The valve coefficient was measured for every insert used with these valves, and an expression was determined to relate the orifice diameter to other pertinent flow parameters. Two dimensionless groups were chosen to correlate the collected data, and expressions were developed that can be used as aids in sizing the orifice insert needed to obtain the desired valve coefficient. The study has shown that a 2nd order polynomial equation as well as a power law equation can both be used to predict the desired results. Knowing pipe size and schedule, the diameter of the orifice insert needed to obtain the required valve coefficient can be approximated with minimum error. An error analysis performed on the collected data shows that the results are highly accurate, and that the experimental process is repeatable.

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