On Cup Anemometer Rotor Aerodynamics

Abstract

The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

Improved analytical method to study the cup anemometer performance

“…In our former works this was not considered [12,14]. However, this shift is taken into account in an interesting work published in 1895 by Chree [19].…”

“…Non-dimensional shift of the normal-to-the-cup aerodynamic force, measured from the cup center (see also figure 2), dlR c , as a function of the wind speed angle with respect to the cup, a. In the graph the results from CFD calculations (solid -K -s-oo-and dashed lines -K = 3.5, with r r = 0.5-) are included [16], together with testing results from a previous work [14], and the 1-harmonic Fourier approximation (equation (8)) to these experimental results.…”

“…However, this quadratic expression is not clear [2]. Taking into account the testing results from [14], the slope of the cup anemometer calibration curve based on the rotation frequency, A r , can be expressed as a function of R rc and the cups' front area, S c , (S c TTR 2…”

“…In figure 4 this shift is shown as a function of the wind angle with respect to the cup. Three cases are included in the graph, the experimental results corresponding to the testing series measured in 2012 on a static conical cup [14], and the CFD results corresponding to a static (K ->• oo) andarotating cup (K = 3.5, with r r = 0.5) [16]. The results corresponding to the static cups are anti-symmetrical with respect to a = 180°, whereas a phase angle can be observed regarding the shift d on the rotating cup.…”

Studies on Cup Anemometer Performances Carried out at IDR/UPM Institute. Past and Present Research

“…With regard to the aforementioned wind speed sensors calibration, this line of work has produced a strong research, mainly focused on cup anemometers (see Figure 1) [22][23][24][25][26][27][28][29][30][31][32][33][34]. Additionally, some relevant research devoted to sonic anemometers has been carried out at IDR/UPM [35][36][37][38][39].…”