Grain-Stream Velocity Measurements

1971 ◽  
Vol 14 (1) ◽  
pp. 0162-0166 ◽  
Author(s):  
D. E. Fiscus ◽  
G. H. Foster and H. H. Kaufmann
Keyword(s):  
Stream Velocity ◽  
Velocity Measurements

Separating and Reattaching Flow Structure in a Suddenly Expanding Rectangular Duct

1995 ◽  
Vol 117 (1) ◽  
pp. 17-23 ◽  
Author(s):  
G. Papadopoulos ◽  
M. V. O¨tu¨gen
Keyword(s):  
Aspect Ratio ◽  
Flow Structure ◽  
Three Dimensional ◽  
Side Wall ◽  
Stream Velocity ◽  
Rectangular Duct ◽  
Mean Flow ◽  
Wall Effects ◽  
Velocity Measurements ◽  
Aspect Ratios

The incompressible turbulent flow over a backward-facing step in a rectangular duct was investigated experimentally. The side wall effects on the core flow were determined by varying the aspect ratio (defined as the step span-to-height ratio) from 1 to 28. The Reynolds number, based on the step height and the oncoming free-stream velocity, was 26,500. Detailed velocity measurements were made, including the turbulent stresses, in a region which extended past the flow reattachment zone. Wall static pressure was also measured on both the step and flat walls. In addition, surface visualizations were obtained on all four walls surrounding the separated flow to supplement near-wall velocity measurements. The results show that the aspect ratio has an influence on both the velocity and wall pressure even for relatively large aspect ratios. For example, in the redevelopment region downstream of reattachment, the recovery pressure decreases with smaller aspect ratios. The three-dimensional side wall effects tend to slow down the relaxation downstream of reattachment for smaller aspect ratios as evidenced by the evolution of the velocity field. For the two smallest aspect ratios investigated, higher centerplane streamwise and transverse velocities were obtained which indicate a three-dimensional mean flow structure along the full span of the duct.

Velocity Measurements on the Forward Portion of a Cylinder

1990 ◽  
Vol 112 (2) ◽  
pp. 243-245 ◽  
Author(s):  
D. E. Paxson ◽  
R. E. Mayle
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Static Pressure ◽  
Free Stream ◽  
Stream Velocity ◽  
Pressure Measurements ◽  
Velocity Measurements ◽  
Flow Around A Cylinder

Velocity measurements in the laminar boundary layer around the forward portion of a circular cylinder are presented. These results are compared to Blasius’ theory for laminar flow around a cylinder using a free-stream velocity distribution obtained from static pressure measurements on the cylinder. Even though the flow is periodically unsteady as a result of vortex shedding from the cylinder, it is found that the agreement is excellent.

Improvement of Constant Temperature Anemometer and Measurement of Energy Spectra in a Plane Turbulent Jet

2012 ◽  
Author(s):  
Osamu Terashima ◽  
Kazuhiro Onishi ◽  
Yasuhiko Sakai ◽  
Kouji Nagata
Keyword(s):  
Frequency Response ◽  
Free Stream ◽  
Wheatstone Bridge ◽  
Wave Number ◽  
Stream Velocity ◽  
Fine Scale ◽  
Hot Wire ◽  
Velocity Measurements ◽  
Scale Structures ◽  
Constant Temperature Anemometer

A constant temperature anemometer (CTA) is a useful instrument for measuring the velocity fluctuations in turbulent flow. However, in our calibration test, the actual frequency response of a typical CTA was no more than 5 kHz under normal laboratory conditions: for example, the diameter of the hot wire is 5 μm and the free stream velocity is 20 m/s. Therefore, in some cases, a typical CTA is not enough to measure accurately turbulent velocity fluctuations for fine scale structures. In this paper, we present a rearranged CTA circuit to obtain a faster frequency response so that in turn fine-scale structures can be more accurately investigated. A typical CTA circuit consists of a Wheatstone bridge and a feed back circuit. To improve the frequency response, the ratio of the electrical resistance of the Wheatstone bridge is set to 1 and two operational amplifiers with a gain-band width product of 100 MHz and a slew rate of 20 V/μs are used in the feedback circuit. An experiment to estimate the frequency response of the rearranged CTA circuit is performed with a free stream velocity of 20 m/s and using hot wires of diameter 5 μm and 3 μm. Experimental results show that the roll-off frequency of the rearranged CTA circuit is improved from 5 kHz to 20 kHz for the 5 μm hot wire and from 6 kHz to 40 kHz for the 3 μm hot wire. Velocity measurements are made using the rearranged CTA circuit in a plane turbulent jet where the value of the Taylor microscale λ is 3.2 mm and the Taylor-scale Reynolds number Reλ is 440. Measurements shows that the power spectrum obeys the reliable numerical profile derived by a LDIA (Lagrangian Direct-Interaction Approximation) theory until more than 0.20 of the non-dimensional wave number κ1η, which is a wider range in comparison with the results obtained when using a typical CTA circuit. Here, κ1 is the axial wave number and η is the Kolmogorov microscale. Further, velocity measurements are performed taken using the rearranged CTA circuit with a square jet where the value of λ is 6.3 mm and Reλ is 1,720. Measurements shows that the power spectrum obeys the numerical profile by the LDIA theory in the range 0.04 < κ1η < 0.20, which is a much wider range than the results obtained when using a typical CTA circuit (0.04 < κ1η < 0.08). These results indicate that the rearranged CTA circuit can be used to investigate fine-scale structures in turbulent flows more accurately.

scholarly journals EXPERIMENTAL RESEARCH ON THE DISTRIBUTION OF AIR STREAM VELOCITY USING THE TWO-LEVEL CYCLONE / EKSPERIMENTINIAI ORO SRAUTO GREIČIŲ PASISKIRSTYMO DVIEJŲ LYGIŲ CIKLONE TYRIMAI

2013 ◽  
Vol 5 (4) ◽  
pp. 330-336 ◽  
Author(s):  
Egidijus Baliukas ◽  
Pranas Baltrėnas
Keyword(s):  
Air Flow ◽  
Solid Particles ◽  
Maximum Speed ◽  
Stream Velocity ◽  
Velocity Measurements ◽  
Air Velocity ◽  
Air Volume ◽  
Air Stream ◽  
Before And After ◽  
Air Speed

In order to properly analysethe operation of a two-level multichannel cyclone,a studyon how air flow moves inside the cyclone is necessary. The two-level multichannel cyclone is designed to separate solid particles from the air stream andhas been built in the Environmental Protection Laboratory at Vilnius Gediminas Technical University. Researches on findinghow theair flow distributes withintwo levels and channels of the six-channel cyclone were made. Air velocity was measured using multimeter Testo–400 and dynamic Pito tube. Air velocity measurements in ducts before and after thedevice were done using an anemometer. The results showed that the air volume at both cyclone levels wereequal, and air velocity inthe channels that werethe same at both levels was also distributed equally. The highest air speed was measured at the end of the last IV channel and reached 13 m/s. Minimum air velocity can be observed when the rings are arranged in such way that 75% of the air flow returns to the previous channel, and the maximum speed is when the previous channel returns 25% of the air flow. Article in Lithuanian. Santrauka Siekiant tinkamai išanalizuoti dviejų lygių daugiakanalio ciklono veikimą būtina išnagrinėti valomo oro srauto judėjimą. Šis įrenginys skirtas kietosioms dalelėms iš oro srauto valyti. Daugiakanalis dviejų lygių ciklonas sukurtas ir pastatytas Vilniaus Gedimino technikos universiteto Aplinkos apsaugos laboratorijoje. Tyrimais siekiama nustatyti oro srauto pasiskirstymą dviejuose šešiakanalio ciklono lygiuose bei kanaluose. Oro greičiams kanaluose nustatyti naudojamas daugiafunkcis matuoklis Testo-400 ir dinaminis Pito vamzdelis. Oro srauto greičiams matuoti ortakiuose prieš ir už įrenginio naudojamas sparninis anemometras. Rezultatai rodė, kad į abu ciklone įrengtus lygius patenka vienodas oro tūris, ir greičiai šių lygių kanaluose pasiskirsto vienodai. Didžiausias greitis – 13 m/s užfiksuotas paskutiniojo kanalo pabaigoje. Mažiausi oro greičiai kanaluose esti, kai žiedai sudėti taip, kad 75 % oro srauto grįžtų į ankstesnį kanalą, o didžiausias greitis yra tada, kai į ankstesnį kanalą grįžta 25 % oro srauto.

An Experimental Study of Spark Anemometry for In-Cylinder Velocity Measurements

2006 ◽  
Author(s):  
D. P. Gardiner ◽  
G. Wang ◽  
M. F. Bardon ◽  
M. LaViolette ◽  
W. D. Allan
Keyword(s):  
Experimental Study ◽  
Flow Velocity ◽  
Free Stream ◽  
Spark Ignition Engine ◽  
Constant Current ◽  
Stream Velocity ◽  
Velocity Measurements ◽  
Lower Velocity ◽  
Channel Shape ◽  
Spark Channel

It has been demonstrated by previous researchers that an approximate value of the bulk flow velocity through the spark plug gap of a running spark ignition engine may be deduced from the voltage and current waveforms of the spark. The technique has become known as spark anemometry and offers a robust means of velocity sensing for engine combustion chambers and other high temperature environments. This paper describes an experimental study aimed at improving performance of spark anemometry as an engine research tool. Bench tests were conducted using flow provided by a calibrated nozzle apparatus discharging to atmospheric pressure. Whereas earlier studies had relied upon assumptions about the shape of the stretching spark channel to relate the spark voltage to the flow velocity, the actual spark channel shape was documented using high speed video in the present study. A programmable ignition system was used to generate well-controlled constant current discharges. The spark anemometry apparatus was then tested in a light duty automotive engine. Results from the image analysis of the spark channel shape undertaken in the present study have shown that the spark kernel moves at a velocity of less than that of the free stream gas velocity. A lower velocity threshold exists below which there is no response from the spark. It is possible to obtain a consistent, nearly linear relationship between the first derivative of the sustaining voltage of a constant current spark and the free stream velocity if the velocity falls within certain limits. The engine tests revealed a great deal of cycle-to-cycle variation in the in-cylinder velocity measurements. Instances where the spark restrikes occur during the cycle must also be recognized in order to avoid false velocity indications.

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