Gliding flight in a jackdaw: a wind tunnel study
(2001) In Journal of Experimental Biology 204(6). p.11531166 Abstract
 We examined the gliding flight performance of a jackdaw Corvus monedula in a wind tunnel. The jackdaw was able to glide steadily at speeds between 6 and 11 m s(1). The bird changed its wingspan and wing area over this speed range, and we measured the socalled glide superpolar, which is the envelope of fixedwing glide polars over a range of forward speeds and sinking speeds. The glide superpolar was an inverted Ushape with a minimum sinking speed (V(ms)) at 7.4 m s(1) and a speed for best glide (V(bg)) at 8.3 m s()). At the minimum sinking speed, the associated vertical sinking speed was 0.62 m s(1). The relationship between the ratio of lift to drag (L:D) and airspeed showed an inverted Ushape with a maximum of 12.6 at 8.5 m... (More)
 We examined the gliding flight performance of a jackdaw Corvus monedula in a wind tunnel. The jackdaw was able to glide steadily at speeds between 6 and 11 m s(1). The bird changed its wingspan and wing area over this speed range, and we measured the socalled glide superpolar, which is the envelope of fixedwing glide polars over a range of forward speeds and sinking speeds. The glide superpolar was an inverted Ushape with a minimum sinking speed (V(ms)) at 7.4 m s(1) and a speed for best glide (V(bg)) at 8.3 m s()). At the minimum sinking speed, the associated vertical sinking speed was 0.62 m s(1). The relationship between the ratio of lift to drag (L:D) and airspeed showed an inverted Ushape with a maximum of 12.6 at 8.5 m s(1). Wingspan decreased linearly with speed over the whole speed range investigated. The tail was spread extensively at low and moderate speeds; at speeds between 6 and 9 m s(1), the tail area decreased linearly with speed, and at speeds above 9 m s(1) the tail was fully furled. Reynolds number calculated with the mean chord as the reference length ranged from 38 000 to 76 000 over the speed range 611 m s(1). Comparisons of the jackdaw flight performance were made with existing theory of gliding flight. We also reanalysed data on span ratios with respect to speed in two other bird species previously studied in wind tunnels. These data indicate that an equation for calculating the span ratio, which minimises the sum of induced and profile drag, does not predict the actual span ratios observed in these birds. We derive an alternative equation on the basis of the observed span ratios for calculating wingspan and wing area with respect to forward speed in gliding birds from information about body mass, maximum wingspan, maximum wing area and maximum coefficient of lift. These alternative equations can be used in combination with any model of gliding flight where wing area and wingspan are considered to calculate sinking rate with respect to forward speed. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/131558
 author
 Rosén, Mikael ^{LU} and Hedenström, Anders ^{LU}
 organization
 publishing date
 2001
 type
 Contribution to journal
 publication status
 published
 subject
 in
 Journal of Experimental Biology
 volume
 204
 issue
 6
 pages
 1153  1166
 publisher
 The Company of Biologists Ltd
 external identifiers

 wos:000167934600009
 scopus:0035744947
 ISSN
 14779145
 language
 English
 LU publication?
 yes
 id
 f405ca38d3cc4afe9223dd2e4eaaa312 (old id 131558)
 alternative location
 http://jeb.biologists.org/cgi/content/abstract/204/6/1153
 date added to LUP
 20070626 12:02:54
 date last changed
 20180610 03:37:31
@article{f405ca38d3cc4afe9223dd2e4eaaa312, abstract = {We examined the gliding flight performance of a jackdaw Corvus monedula in a wind tunnel. The jackdaw was able to glide steadily at speeds between 6 and 11 m s(1). The bird changed its wingspan and wing area over this speed range, and we measured the socalled glide superpolar, which is the envelope of fixedwing glide polars over a range of forward speeds and sinking speeds. The glide superpolar was an inverted Ushape with a minimum sinking speed (V(ms)) at 7.4 m s(1) and a speed for best glide (V(bg)) at 8.3 m s()). At the minimum sinking speed, the associated vertical sinking speed was 0.62 m s(1). The relationship between the ratio of lift to drag (L:D) and airspeed showed an inverted Ushape with a maximum of 12.6 at 8.5 m s(1). Wingspan decreased linearly with speed over the whole speed range investigated. The tail was spread extensively at low and moderate speeds; at speeds between 6 and 9 m s(1), the tail area decreased linearly with speed, and at speeds above 9 m s(1) the tail was fully furled. Reynolds number calculated with the mean chord as the reference length ranged from 38 000 to 76 000 over the speed range 611 m s(1). Comparisons of the jackdaw flight performance were made with existing theory of gliding flight. We also reanalysed data on span ratios with respect to speed in two other bird species previously studied in wind tunnels. These data indicate that an equation for calculating the span ratio, which minimises the sum of induced and profile drag, does not predict the actual span ratios observed in these birds. We derive an alternative equation on the basis of the observed span ratios for calculating wingspan and wing area with respect to forward speed in gliding birds from information about body mass, maximum wingspan, maximum wing area and maximum coefficient of lift. These alternative equations can be used in combination with any model of gliding flight where wing area and wingspan are considered to calculate sinking rate with respect to forward speed.}, author = {Rosén, Mikael and Hedenström, Anders}, issn = {14779145}, language = {eng}, number = {6}, pages = {11531166}, publisher = {The Company of Biologists Ltd}, series = {Journal of Experimental Biology}, title = {Gliding flight in a jackdaw: a wind tunnel study}, volume = {204}, year = {2001}, }