1 Erratum to: Exp Fluids (2009) 46:777–798 DOI 10.1007/s00348-009-0661-2

In Ansari et al. (2009), we presented results of our low-Reynolds number particle-image velocimetry (PIV) experiments on a wing rotating in a water tank. These experiments were aimed at investigating some aspects of insect-like flapping flight flow for application in micro air vehicle design.

Unfortunately, we have realised that our original paper suffered from erroneous calculations of experimental errors owing to confusion over the use of the terms ‘spanwise’ and ‘chordwise’. Chordwise measurement planes are vertical planes, perpendicular to the wing span. Spanwise measurement planes are also vertical but lie along the wing span (perpendicular to the chordwise measurement planes). Together with the locally-level ground plane, the three planes form an orthogonal set. Figure 6 in Ansari et al. (2009) shows 4 chordwise measurement planes and 1 spanwise measurement plane (see also Table 2 below).

We will now present the correct data, together with corrections to some other areas of confusion that we have noticed.

2 Experimental error analysis

Table 1 in Ansari et al. (2009) presented the PIV acquisition parameters for our experiments and Table 2 presented the test cases. These should have read as Tables 1 and 2 below.

Table 1 PIV acquisition parameters
Full size table
Table 2 Test cases
Full size table

In addition, the aspect ratio of our wings was 2.5, not 4 as stated in Ansari et al. (2009, Sect. 3.1, last para). As a result of these correct data, our statement of experimental errors in Ansari et al. (2009, Sect. 4.2, last para) should have read as follows:

Thus, with an rms error of 0.43 px for the spanwise measurements, this leads to a measurement uncertainty of ±6.7 × 10−4 and ±0.039 m/s for the Re = 500 and 15,000 cases, respectively. Similarly, for the chordwise measurements, in the Re = 500 and 15,000 cases an rms error of 0.35 px leads to a measurement uncertainty of ±8.2 × 10−4 and ±0.02 m/s, respectively.

3 Presentation of results

Several of the figures in Ansari et al. (2009) show PIV results for our wing from a section near the root out to beyond the tip; we did not state where this inboard section was. In fact Figs. 15, 16, 21 and 22 in Ansari et al. (2009) all show data starting at 10% of span. The titles of these figures, and Fig. 18, should not refer to Fig. 5.