Vortex flow measurement

Endrcss and Hauser pic Technical Information TI03ID/06/e 11997). Vortex flow measuring system, pttwirl 70. 

Differential pressure level transmitter http //www.youtube.com/watch v=Eym D3tGwlE The Vortex Flow Measuring Principle http //www.youtube.com/watch v=GmTmDM7jHzA The Differential Pressure Flow Measuring Principle http //www.youtube.com/watch v=oUd4WxjoHKY Temperature Measurement Methods. Pyrometers http //www.youtube.com/watch7vKJgHTeqF-jik... 

The principal classes of flow-measuring instruments used in the process industries are variable-head, variaBle-area, positive-displacement, and turbine instruments, mass flowmeters, vortex-shedding and iiltrasonic flowmeters, magnetic flowmeters, and more recently, Coriohs mass flowmeters. Head meters are covered in more detail in Sec. 5. 

Flow measurements using nonintrusive or low mechanical ac tion principles are desired, such as magnetic, vortex-shedding, or Coriolis-type flowmeters. Orifice plates are easy to use and reliable but have a limited range and may not be suitable for streams which are not totally clean. Rotameters with glass tubes should not be used. 

Many polymers exhibit neither a measurable stick-slip transition nor flow oscillation. For example, commercial polystyrene (PS), polypropylene (PP), and low density polyethylene (LDPE) usually do not undergo a flow discontinuity transition nor oscillating flow. This does not mean that their extrudate would remain smooth. The often observed spiral-like extrudate distortion of PS, LDPE and PP, among other polymer melts, normally arises from a secondary (vortex) flow in the barrel due to a sharp die entry and is unrelated to interfacial slip. Section 11 discusses this type of extrudate distortion in some detail. Here we focus on the question of why polymers such as PS often do not exhibit interfacial flow instabilities and flow discontinuity. The answer is contained in the celebrated formula Eqs. (3) or (5). For a polymer to show an observable wall slip on a length scale of 1 mm requires a viscosity ratio q/q equal to 105 or larger. In other words, there should be a sufficient level of bulk chain entanglement at the critical stress for an interfacial breakdown (i.e., disentanglement transition between adsorbed and unbound chains). The above-mentioned commercial polymers do not meet this criterion. 

A second example can be generated when an intensive flow over a body produces closed field lines (called a vortex) at variable distances. This effect was observed by Strouhal (1850-1912) when some flow of air over wires produced a song. The Strouhal s singing wires give the measure of the frequency that characterizes the vortex flow. This type of flow has been used to produce the so-called grid turbulence, which has various applications in the forced cooling of electronic devices [6.29]. 

Meng, H., and Hussain, F., Instantaneous flow field in an unstable vortex ring measured by holographic particle velodmetiy, Physics of Fluids, 7 (1), 9 (1995). 

There are many other types of flow meters that can be used such as venturi meters, vortex shedder flow meters, and Coriolis flow meters. Any of these may be preferred depending on the application. Fluid flow can also be measured indirectly using chemical analysis and mass and energy balance calculations. Air flow measurements are commonly made this way since an oxygen analyzer is generally more accurate than a thermal mass flow meter. 

The effect of polymer solutions, ejected at very small flow rates at the tip of a finite span hydrofoil, on the inception and extent of tip vortex cavitation is investigated. The results show that the dessinent cavitation numbers are significantly reduced by polymer additives as compared with those in pure water. Moreover, for operating conditions well below critical, the presence of polymer in the vortex core results in the nearly complete elimination of the vapour cavity. These effects can be interpreted on the basis of a modification of the velocity field due to the viscoelastic properties of the polymer solutions. L.D.A. measurements indicate a large decrease of the tangential velocity component in the transition region between the inner solid body rotation co.e and the outer potential vortex flow. Also, a change of the slope of the velocity within the core is observed. 

Diverse redundancy uses different technology, design, manufacture, software, firmware, etc., to reduce the influence of common-cause faults. Measures that can be used to achieve diverse redundancy include, but are not limited to, the use of different measurements (e.g., pressure and temperature) when there is a known relationship between them and the use of different measurement technologies for the same process variable (e.g., Coriolis flow and Vortex flow). An example of input diversity is the use of a Resistance Temperature Detector (RTD), Infrared (IR), or bimetal to achieve technology diversity in measuring temperature. An example of output diversity is closing a block valve and turning off a pump to stop flow. 

HAJI ISMAIL, A.W.B. "An investigation of Taylor vortex flow using torgue measurements and hot film aneometry." PhD. Thesis, Dept. Mech. Eng. University of Leeds. 1982. 

Vortex flow meters The flow of a damming body causes vortices. The volume flow can be derived from the measured vortex frequency. Suitable for low viscous, gaseous or vaporous media. The measuring principle requires a minimum Reynolds number of approx. 4000. 

Electronic flow measurement Vortex flow meter Differential pressure measurement ... 

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