Abstract
An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997; Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).
Highlights
In recent years, particle image velocimetry (PIV) has become one of the most popular techniques for measuring velocity fields
Another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997; Tagawa et al 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the constant-current hot-wire anemometer (CCA)
We estimated the frequency response of the hotwires 5 μm, 10 μm and 20 μm in diameter to apply the theoretical response compensation scheme mentioned in section 3.1 to the CCA outputs
Summary
Particle image velocimetry (PIV) has become one of the most popular techniques for measuring velocity fields. The hot-wire anemometry [1,2,3,4,5], on the other hand, has long been used mainly for measuring turbulent gaseous flows because of its simple and highlyreliable measurement systems and wide range of applicability. For the application of the hot-wire anemometry, the constant-temperature anemometer (CTA) is commercially available and almost always used as a standard system for driving the hot-wire, while the other two modes are rarely used, primarily due to their response lag during velocity fluctuation mea-. The electric circuit of the CTA is not simple, and the measurement system is fairly expensive. The constant-current hot-wire anemometer (CCA) can be set up with a very simple and low-cost electric circuit for heating the hot-wire. If we improve the response characteristics of the CCA with the aid of digital signal processing, the CCA will have a great advantage over the CTA and will be a promising tool for multipoint turbulence measurement
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