Studies of a Hot Wire Anemometer with Digital Feedback

摘要

Thermal anemometry has been a key experimental technique in fluid mechanics for many decades. Due to the small physical size and high frequency response of the sensors the technique has been widely used for studies of turbulent flows. Even with the advent of nonintrusive techniques such as Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV), hot wire anemometry is uniquely capable of extremely high frequency response and fine spatial resolution. However, the basic configuration of the thermal anemometer has changed little in the last 50 years. Lengthy cables which are inherently part of the traditional Wheatstone bridge circuit employed in the anemometer circuitry are of particular concern. What is now proposed is a fundamental change to the anemometer configuration, with two related aspects. First, the essential circuitry to power the sensor and establish its operating point will be packaged immediately adjacent to the sensor. Second, modern analog/digital conversion hardware will be employed to the maximum extent possible, ideally including directly driving the sensor from a D/A converter. Data transmission to and from the "anemometer" will then be digital, immune to environmental variations or electrical noise. The ultimate objective of the research is therefore referred to as a "Digital Bridge". Phase I of the reported study verified this concept with two variations demonstrated and documented. Work on a pre-production 3rd generation version is currently underway.