Table 2.

Velocity parameters for bristling events. PTV-derived velocity parameters at (A) initial scale movement and (B) peak scale bristling. Medians and ranges of mean velocity parameters within a 0.2 × 0.2 mm region centred above the tip of a bristling scale, at peak bristling angle, for three flow cases: a backward jet (n = 2), a forward jet (n = 3) and a forward jet with a vortex upstream of the sale (n = 1).

	backward jet			forward jet			vortex
flow parameter	median	range		median	range		—
A
x velocity (m s−1)	−0.92	−1.03	−0.81	−0.13	−0.61	−0.11	0.63
y velocity (m s−1)	0.13	−0.04	0.29	−0.30	−0.41	−0.20	−0.07
magnitude (m s−1)	0.94	0.86	1.03	0.33	0.23	0.74	0.63
direction (deg.)	8.76	−2.02	19.53	−60.03	−65.88	−33.56	−173.76
B
x velocity (m s−1)	−1.95	−2.37	−1.53	−0.36	−0.66	0.11	−0.22
y velocity (m s−1)	0.04	−0.06	0.14	−0.40	−0.40	0.20	0.25
magnitude (m s−1)	1.96	1.54	2.37	0.44	0.41	0.76	0.33
direction (deg.)	1.93	−1.53	5.40	−29.30	−105.10	33.83	49.32