Richardson 1997

8/20/2019 Richardson 1997

1/11

; vJn'~

ELSEVIER

Journal of Wind Engineering

and Industrial Aerodynamics72 (1997) 187-197

JOURN L OF

The S i l soe S tructures Bu i ld ing

C om p a r i so n s o f p r e s su r e s m e asu r e d a t fu ll s c a le

a n d i n t w o w i n d t u n n e l s

G.M. Richardson, R.P. Hoxey*, A.P. Rober tson , J .L. Shor t

Silsoe Research Institute, Wrest Park, Silsoe, Bedford M K4 5 4HS , UK

Ab s t r a c t

Two independent sets of full-scale wind pressure measurements have been completed on the

Silsoe Structures Building in both its configurations (featuring a conventional sharp eaves and

a modern curved eaves). Results are compared with those from two 1 : 100 scale measurement

programmes conducted in two leading wind tunnels on models of the building with both the

sharp and curved eaves. These comparisons highlight the importance of implementing certain

wind tunnel procedures in order to obtain good predictions of full-scale mean pressure

coefficients. However, areas of high negative pressure still tend to be under-estimated in

wind-tunnel measurements and this is considered to be associated with a Reynolds number

effect.

1 I n t r o d u c t i o n

The Silsoe Structures Building (SSB) [1] was constructed during 1986/87 specifi-

cally to undertake full-scale wind pressure measurements. The building was construc-

ted with an optional eaves geometry offering either a traditional sharp eaves or

a curved eaves of 635 mm radius. Results of wind pressures generated by bot h

arrangement s are presented. The 24 m long by 12.9 m span by 5.3 m ridge height

building with a 10 ° duo- pitch roo f is loca ted on a flat, exposed, open-co unt ry site at

Silsoe Research Institute (SRI). Measurements [2] show that the profile is well

represented by a log-law with a roughness l ength (Zo) of 0.01 m, and a frictional

velocity comp ared with the free-stream velocity at 10 m u , / u l o ) of 0.06. A brief

abst rac t of the pressure measuring proced ure is presented in Section 2; a more

detailed account is given in Ref. [1].

* Corresponding author. E-mail: [email protected].

0167-6105/97/ 17.00 © 1997 Elsevier Science B.V. All rights reserved.

P I I S01 67-61 05 (9 7)0 02 74- 2


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88 G.M. Richardson el al.:d. Wind Eng. hul. Aerodvn. 72 1997) 187-197

A n o b j e c t i v e o f t h i s w o r k w a s t o p r o v i d e r e li a b l e f u ll -s c a le d a t a f o r c o m p a r i s o n w i t h

w i n d - tu n n e l m e a s u r e m e n t s a n d c o m p u t a t i o n a l f lu id d y n a m i c s s o l u ti o n s. T w o w i n d-

t u n n e l s tu d i es w e r e c o n d u c t e d , o n e a t th e U n i v e r s i t y o f W e s t e r n O n t a r i o a n d o n e

a t t h e B u i l d i n g R e s e a r c h E s t a b l i s h m e n t ; t h e s e a r e d e s c r i b e d i n S e c t i o n 2 . C o m p a r i -

s o n s b e t w e e n t h e f u l l - s c a l e a n d w i n d - t u n n e l r e s u l t s a r e r e s t r i c t e d i n t h i s r e p o r t t o

c o m p a r i n g m e a n p r e s s u r e co e f f ic i e n ts S e c t i o n 4 ) s i n ce t h e m e a n c a n b e d e t e r m i n e d

w i t h h i g h e r s t a ti s ti c a l c o n f id e n c e ; i f a g r e e m e n t c a n n o t b e o b t a i n e d , e x p l a n a t i o n s

s h o u l d b e s o u g h t b e f o r e e x a m i n i n g p e a k o r e x t r e m e v a lu e s. T h e m e t h o d s u s e d t o

a n a l y s e t h e f u l l- s ca l e d a t a w e r e p r e s e n t e d i n R ef. [ 3 ]; t h e s e m e t h o d s c a n a l s o b e

a p p l i e d t o w i n d - t u n n e l m e a s u r e m e n t s p r o v i d e d t h a t a s im u l t a n e o u s r e c o r d is m a d e o f

w i n d s p e e d a n d d i r e c t io n i m m e d i a t e l y u p s t r e a m o f t h e m o d e l . E x t e n s i v e an a l y s is o f

t h e d a t a h a s a ls o b e e n c o m p l e t e d e x p l o r i n g m e a n , R M S a n d p e a k v a lu e s, a n d

p r o b a b i l i t y a n d s p e c t r a l d e n s i t i e s . T h e s e a n a l y s e s w e r e p r e s e n t e d a n d d i s c u s s e d i n

Ref . [3] .

2 Experimental detai ls

2.1. Full scale measurements

T w o i n d e p e n d e n t s e ts o f f u ll -s c al e p r e s s u r e m e a s u r e m e n t s h a v e b e e n m a d e o n t h e

S S B . T h e fi rs t s e t o f m e a s u r e m e n t s S R I m e a s u r e m e n t s ) a r e d e s c r i b e d i n d e t a il in

R ef. [ 1 ]. S i m p l e t a p p i n g h o l e s w e r e u s e d o n t h e s i d e o f t h e b u i l d i n g a n d s t a t ic

p r e s s u re p r o b e s [ 4 ] o n t h e r o o f; t h e p r o b e s o v e r c a m e th e p r o b l e m o f r a i n - w a t e r

p e n e t r a t i o n a n d l o c a l e f fe c ts c a u s e d b y t h e p r o f i l e d c l a d d i n g . I n t o t a l , 7 7 p r e s s u r e

t a p p i n g p o i n t s w e r e i n s t a l l e d o n t h e b u i l d i n g a n d m e a s u r e m e n t s w e r e m a d e u s i n g

a s e q u e n c e c o n t r o l l e r w h i c h s a m p l e d t w o p r e s s u r e s a t o n e t im e . A d w e l l ti m e o f 4 ra i n

w a s u s e d f o r e a c h p a i r o f t a p p i n g p o i n t s , a n d 4 r a in m e a n v a l u e s w e r e c o m p u t e d .

A c o m p l e t e d e f in i t io n o f p r e ss u r e s o v e r t h e b u i l d in g s u r f a c e r e q u ir e d m a n y h o u r s o f

r e c o r d i n g .

A s e c o n d i n d e p e n d e n t s e t o f i n s t r u m e n t a t i o n w a s i n s ta l le d o n t h e b u i ld i n g f o r w o r k

s p o n s o r e d b y t h e B u il d i n g R e s e a r c h E s t a b l i sh m e n t B R E m e a s u r e m e n t s ). I n t h is

e x p e r i m e n t , 3 2 p r e s s u r e t a p p i n g p o i n t s w e r e i n s ta l le d , e a c h w i t h a p r e s s u r e t r a n s d u c e r

m o u n t e d l o c a ll y o n t h e i n si d e o f t h e b u il d in g . S i m u l t a n e o u s m e a s u r e m e n t s w e r e m a d e

f r o m t h e 3 2 p r e s s u r e t a p p i n g p o i n t s t o g e t h e r w i t h w i n d v e l o c i t y s e n s e d b y a t h r e e -

c o m p o n e n t s o n i c - a n e m o m e t e r . R e c o r d s o f I h d u r a t i o n w e r e m a d e , a n d t h e se w e r e

p a r t i t i o n e d i n t o s i x t 0 m i n r e c o r d s f o r a n a ly s i s .

I n b o t h e x p e r i m e n t s , a ll p r e s s u r e s w e r e m e a s u r e d r e l a t i v e to a s t a t i c p r e s s u r e s e n s e d

b y a p r o b e w h i c h w a s p o s i t i o n e d a t t h e r id g e h e i g h t o f t h e b u i ld i n g 2 0 m u p s t r e a m o f

t h e b u i l d i n g w h e r e t h e i n f l u e n c e o f t h e p r e s s u r e f ie ld a s s o c i a t e d w i t h t h e b u i l d i n g w a s

s m a l l. P r e s s u r e t r a n s d u c e r s w e r e a u t o m a t i c a l l y z e r o e d u s in g a s o l e n o i d v a l v e t o

e q u a l i s e t h e p r e s s u r e a c ro s s t h e t r a n s d u c e r , a n d w e r e c a l i b r a t e d b y u s i n g s o l e n o i d

v a lv e s t o a p p l y a c o m m o n w i n d d y n a m i c p r e ss u r e to a ll t r a n s d u c e rs . T h i s p r o c e d u r e

e n s u r e d a p r e s s u r e m e a s u r e m e n t a c c u r a c y o f b e t t e r t h a n _+ 1 N / m 2. F o r t h e S R I

m e a s u r e m e n t s , p l a s t ic t u b e s u p t o 2 5 m i n l e n g t h c o n v e y e d th e p r e s s u r e s f r o m t h e


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G.M. Richardson e t al . / J . W ind Eng. Ind. Aerodyn. 72 1997) 18 7-1 97

89

t a p p i n g p o i n t s t o t h e t r a n s d u c e r s a n d t h is r e s t r ic t e d th e f r e q u e n c y r e s p o n s e t o 3 d B

d o w n a t 2 .5 H z . P n e u m a t i c f i lt er s w e r e in s t a ll e d t o d a m p u n w a n t e d r e s o n a n c e ef fe ct s.

T h e a n a l o g u e o u t p u t s f r o m t h e p r e s s u r e t ra n s d u c e r s w e r e d ig i ti s ed a t a r a t e o f 2 .5 H z ,

p r o c e s s e d a n d d i s c a r d e d a f t e r d i g i ti s a ti o n . F o r t h e B R E m e a s u r e m e n t s , a 0.5 m l e n g t h

o f t r a n s m i s s io n t u b i n g w a s u s e d a n d t h e r e w a s n o m e a s u r a b l e a t t e n u a t i o n u p t o

5 0 H z . T h e s a m p l i n g f r e q u e n c y w a s 5 H z . T h e r e c o r d s w e r e s to r e d o n d i g i ta l m a g n e t i c

t a p e a n d a r e a v a i l a b l e f o r f u r t h e r a n a l y si s .

2.2. University of Western Ontario UWO): 1988) 1:100 scale measurements

T h e b o u n d a r y l a y e r i n w i n d t u n n e l N o . 1 a t U W O w a s d e v e l o p e d o v e r a d i s ta n c e o f

a b o u t 2 0 m a s t h e a ir w a s s u c k e d d o w n t h e t u n n e l . T h e w o r k i n g s e c t io n w a s

a p p r o x i m a t e l y 2.5 m w i d e b y 2 .0 m h i g h . T h r e e la r g e s p i re s n e a r t h e i n l e t w e r e u s e d t o

i n c r e a s e t h e b o u n d a r y l a y e r t h i c k n e s s a n d t o i n c r e a s e t h e t u r b u l e n c e s c a l e s . R o u g h -

n e s s e l e m e n t s c o n s i s t e d o f s e ts o f s t a g g e r e d 2 5 m m c u b e s p o s i t i o n e d t o w i t h i n 2 m o f

t h e m o d e l a n d r a n d o m l y s p a c e d 7 m m h i g h m a c h i n e n u t s d i s t ri b u t e d o v e r th e a r e a

a r o u n d t h e m o d e l .

T h e v e l o c i t y p r o f il e at t h e c e n t r e o f t h e t u r n t a b l e w a s d e f i n e d u s i n g t w o l i n e ar i se d

s i n g l e h o t - w i r e a n e m o m e t e r s . T h i s p r o f i l e w a s l a t e r u s e d t o c o r r e c t t h e p r e s s u r e

c o e ff ic i en t s w h i c h w e r e r e f e r e n c e d to f r e e -s t r e a m p r e s s u r e s r e c o r d e d a b o v e t h e g e n e r -

a t e d b o u n d a r y l ay e r. T h e l im i t a t io n s o f t hi s p r o c e d u r e h a v e b e e n p r e s e n t e d b y

R i c h a r d s o n e t a l . [ 5 ] .

T h e 1 : 1 0 0 s c a l e m o d e l s w e r e m a n u f a c t u r e d b y t h e B R E w h o k i n d l y l o a n e d t h e

m o d e l s f o r t h is c o m p a r a t i v e s t u d y . T h e t a p p i n g s w e r e 1 .0 m m i n t e r n a l d i a m e t e r h o l e s.

T h e p n e u m a t i c s y s t e m w a s e s s en t ia l ly l in e a r i n it s r e s p o n s e t o a b o u t 9 0 H z . T h e

S t a t h a m 2 .5 p s i t r a n s d u c e r s p r o v i d e d d i g i ti z e d d a t a a c c u r a t e t o w i t h in 0 . 0 4 4 ) .0 8 o f

t y p i c a l w i n d d y n a m i c p r e s su r e q ) a t m o d e l r i d g e h ei g h t.

2.3. BuiMing research establishment BRE) : 1992) 1:100 scale measurements

T h e b o u n d a r y l a y e r i n th e B R E w i n d t u n n e l N o . 3 w a s d e v e l o p e d o v e r a d i s ta n c e o f

a b o u t 1 5 m a s th e a i r w a s b l o w n d o w n t o t h e 2 m w i d e b y 1 .5 m h i g h w o r k i n g s e c t i o n .

I n i ti a ll y , t h e a i r w a s p a s s e d t h r o u g h a 0.5 m s q u a r e g r id a n d o v e r a s h a r p - t o o t h e d

b a r r i e r o f 4 8 5 m m t o t a l h e i g h t. D o w n s t r e a m o f t h is w a s 1 4 m o f 1 0 m m h i g h s u r f ac e

r o u g h n e s s e l em e n t s. T h e f in a l i n n e r b o u n d a r y l a y er w a s d e v e l o p e d o v e r t h e s m o o t h

t u r n t a b l e b y t h e a d d i t i o n o f t h r ee c o n c e n t r i c 1 0 m m h i g h p e r m e a b l e b a r ri e rs o f l o o p e d

i n t e r l i n k e d c h a i n .

T h e v e l o c i t y p r o f i le a t t h e c e n t r e o f t h e m o d e l p o s i t i o n w a s m e a s u r e d u s i n g a

T S I M o d e l 8 4 5 1 - 5 1 M - B a i r v e l o c it y t r a n s d u c e r m o u n t e d h o r i z o n t a l l y at a c o n -

s t a n t r e f e r en c e h e i g h t o f 1 0 0 r a m a n d a v e r ti c a ll y t r a v e r s e d D a n t e c T y p e 5 5

s in g le h o t - w i r e p r o b e . T h e B R E 1 :1 00 s c al e m o d e l s w e r e u se d , as in t h e U W O t es ts ,

b u t t h i s t i m e w i t h B R E t u b i n g a n d s e n s o r s . T h e p n e u m a t i c s y s t e m g a v e a u n i t y

r e s p o n s e t o 1 00 H z . T h e d i f fe r e n ti a l p r e s s u r e t r a n s d u c e r s w e r e S c a n i v a l v e m o d e l t y p e

P D C R 2 4 D .


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19 G. M. R ic hardson e l a l . / J . ~ T nd Eng . I nd . Ae rod y n . 72 1997) 18 7 - 1 97

3 D a t a reco rdin g a n d a n a ly s i s

T h e f u ll -s ca le m e a s u r e m e n t s w e r e p r o c e s s e d to g i ve m e a n , R M S , m a x i m u m a n d

m i n i m u m v a l u e s o f s u r f a c e p r e s s u r e s a n d s i m i l a r s t a ti s ti c s fo r th e w i n d d y n a m i c

p r e ss u r e, t o g e t h e r w i th t h e m e a n a n d R M S o f t h e w i n d d i re c t io n . A li m i te d n u m b e r o f

a d d i t i o n a l m e a s u r e m e n t s w e r e m a d e w i th b o t h s et s o f i n s t r u m e n t a t i o n in w h i ch t h e

p r e s s u r e s w e r e r e c o r d e d a t a h i g h e r d i g i t is a t i o n r a t e o f 2 0 H z f o r s p e c t ra l a n a l y s is . F o r

t h e S R I m e a s u r e m e n t s , t h e p r e s s u re t r a n s d u c e r s w e r e t h e n p o s i t i o n e d l o c a ll y s o t h a t

t u b e l e n g t h s w e r e r e d u c e d t o le ss t h a n 6 m , g iv i n g a n i m p r o v e d f r e q u e n c y r e s p o n s e o f

3 d B d o w n a t 1 2 H z .

T h e t w o m o d e l - s ca l e d a t a s et s r e q u i r e d t r a n s f o r m a t i o n f o r c o m p a r i s o n w i t h t h e

f u ll -s ca le d a t a . I n t h e ca s e o f t h e U W O d a t a , c o n s i d e r a b l e w o r k w a s c o n d u c t e d t o

i n t e r p r e t t h e d a t a s e t s [ 5 ] . F o l l o w i n g a p i l o t e x p e r i m e n t [ 6 ] , t h e B R E w i n d - t u n n e l

t es ts i n c l u d e d s i m u l t a n e o u s m e a s u r e m e n t o f su r fa c e p re s s u r e a n d f r e e -s t r ea m w i n d

d y n a m i c p r e ss u r e. T h i s e n a b l e d s e n s o r c a l i b r a t i o n a n d c o e ff ic i en t e v a l u a t i o n t o b e

m a d e i n t h e s a m e m a n n e r a s a t f u l l s c a l e . T w o c o r r e c t i o n s w e r e a p p l i e d : t h e f i r s t f o r

t h e s t at ic p r e s s u re f r o m t h e p i t o t -s t a t i c p r o b e w h i c h i n t u r b u l e n t f lo w u n d e r - r e a d b y

4 . 2 , a n d t h e s e c o n d f o r t h e 1 5 u n d e r e s t i m a t i o n o f ~ d u e to th e l o n g tu b e l e n g th s

u s e d f o r th e r e f e r e n c e p i t o t p r o b e [ 7 ] .

P r e s s u r e c o e ff ic ie n ts w e r e o b t a i n e d b y n o n - d i m e n s i o n a l i s i n g m e a s u r e d p r e s su r e s b y

t h e f re e - s tr e a m w i n d d y n a m i c p r e s s u re m e a s u r e d a p p r o x i m a t e l y 4 b u i l d i n g h e i g h ts

u p s t r e a m a t t h e r i d g e h e i g h t o f t h e b u i l d i n g .

4 C o m p a r i s o n o f re su lt s

4.1. Sc ale f i~ctors

A typ ic a l a ve r a g e r e f e r e nc e ve loc i ty a t b u i ld ing r idge he igh t i n t he S i l soe f u l l -s c a l e

m e a s u r e m e n t s w a s 1 0 m / s . T h e U W O r id g e h e i g h t v e l o c i ty w a s 6 . 9 m / s , a n d

i n th e B R E w i n d t u n n e l i t w a s 9 m / s . T h e r e f e re n c e h e i g h t s p e c t r a in b o t h w i n d

tunn e l s w e r e a t a 1 :100 f r e q ue n c y sc a l ing , in ke e p ing w i th the l i ne a r s c a l ing o f t he

m o d e l s .

4.2 . Pro f i l e s

A c o m p a r i s o n o f th e l o n g i t u d i n a l v e l o c i ty {u p r o f il e s f r o m f ul l s c a le a n d b o t h w i n d

tunn e l s i s g ive n in F ig . 1. Th e l i ne d r a w n f o r a fu l l -s c a l e su r f a c e r oug hn e ss he ig h t ( z0 )

o f 10 m m is a g o o d f it t o t h e f u ll -s c al e a n d B R E w i n d - t u n n e l d a t a , b u t t h e U W O d a t a

s h o w o n l y li m i t e d a g r e e m e n t b e t w e e n h e i g h ts o f 3 a n d 1 5 m . T h e U W O m e a s u r e -

m e n t s i n d i c a t e a s i g n i f i c a n t r e d u c t i o n i n s u r f a c e r o u g h n e s s c l o s e t o t h e m o d e l

p o s i t i o n .

T h e c o m p a r i s o n o f t u r b u l e n c e i n t en s i ti e s in F i g . 2 al so s h o w s t h e B R E d a t a t o b e in

c l o s e r a g r e e m e n t w i t h t h e f u ll -s c a le d a t a . A c o m p a r i s o n o f r e fe r e n c e h e i g h t v e l o c i t y

s p e c t r a w a s m a d e b y R i c h a r d s o n e t al . [ 6 ,7 ] . T h e m o s t s i g n i f i c a n t d i f fe r e n c e s i n t h e


5/11

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Fig. I. Verticalprofiles of longitudinal velocity.

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Fig. 2. Ve rtical profiles of longitudinal turbulence intensity.

m o d e l l e d b o u n d a r y l a y e r s o c c u r c l o se t o t h e g r o u n d a re g i o n f r o m w h e r e s t r ea m l i n e s

o r i g i n a t e w h i c h i n f lu e n c e f lo w a r o u n d t h e b u il d in g i n c l u d i n g t h o s e t h a t s t a g n a t e a n d

t h o s e t h a t s e p a r a t e f r o m i t s s h a r p e d g e s .


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F i g . 5. F u l l - s c a le d a t a c o m p a r i s o n : s h a r p e a v e d b u i l d i n g , n e a r - e a v e s r o o f t a p .

4 3 Ov eral l sur face pres sure d i s t ribut ion: t ransverse wind

F i g s . 3 a n d 4 s h o w t h e m e a n p r e s s u r e c o e f f i ci e n t C p) d i s t r i b u t i o n s f o r th e f u ll - sc a l e

b u i l d i n g i n i t s c u r v e d a n d s h a r p e a v e d c o n f i g u r a t i o n s . T h e s i g n i f i c a n t d i f f e r e n c e

b e t w e e n t h e s e d i s t r ib u t i o n s o c c u r s a t t h e w i n d w a r d e a v e s w h e r e t h e s u c t i o n s o v e r th e

w i n d w a r d r o o f a r e g r e a t e r f o r t h e s h a r p e a v e s. T h i s is d u e t o t h e d i f f e re n c e i n t h e fl o w ,

w h i c h w a s i l l u s t ra t e d [ 8 ] t h r o u g h f lo w v is u a l is a t io n . O b s e r v a t i o n s o f t h e s h a r p e a v e s

f lo w s e p a r a t i o n i n t h e U W O w i n d t u n n e l s h o w e d i t t o b e le ss s ev e r e t h a n a t f ul l s ca le ,

a n d t h is i s r e f le c t e d i n t h e r e d u c e d s u c t i o n s r e c o r d e d i n t h is r e g i o n i n b o t h w i n d

t u n n e l s a s d e m o n s t r a t e d b y c o m p a r i n g F ig s . 5 a n d 6 f o r t h e t r a n s v e r s e w i n d d i r e c t i o n

given by 0 = 180°) .

4 4 Speci f i c tapping poin ts

F i g. 5 s h o w s t h e t y p i c a l l y g o o d a g r e e m e n t b e t w e e n t h e m e a n p r e s s u r e c oe f fi c ie n t s

o b t a i n e d f r o m t h e t w o s et s o f f u ll -s c al e m e a s u r e m e n t s . T h i s e x a m p l e is f o r a r o o f

t a p p i n g a t t h e m i d - l e n g t h o f t h e b u i ld i n g , 1 m u p f r o m t h e w i n d w a r d e a v e s o f t h e

s h a r p e a v e d b u i l d i n g . T h e r e d u c e d s c a t t e r i n t h e B R E d a t a , e v i d e n t n e a r t h e 1 80 ° w i n d

d i r e c ti o n , re f le c ts th e l o n g e r t i m e a v e r a g e p e r i o d o f 1 0 m i n u s e d t o o b t a i n t h e s e d a t a

c o m p a r e d w i t h 4 m i n u s e d t o o b t a i n t h e S R I d a t a . A t t h e 2 7 0 ° a n d 9 0 ° d i r e c t i o n s t h e r e

is a s u g g e s t i o n t h a t t h e S R I d a t a a r e a f fe c t ed b y i n a p p r o p r i a t e p o s i t i o n i n g o f t h e

r e f e re n c e m a s t i n r e l a t i o n t o t h e s e a p p r o a c h w i n d d i r e c t io n s w h i c h p r o d u c e d a b i as i n

t h e r e f e r e n c e s t a t i c p r e s s u r e d a t a w e r e n o t o r i g i n a l l y e x p e c t e d t o b e c o l l e c t e d a t t h e s e

d i r e c t i o n s ) . F i g . 6 c o m p a r e s t h e t w o w i n d - t u n n e l d a t a s e t s f o r t h e s a m e t a p p i n g a n d


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F i g. 6 . M o d e l - s c a l e d a t a c o m p a r i s o n : s h a r p e a v e d b u i l d in g , n e a r - e a v e s r o o f t a p .

s h o w s b e t t e r t h a n e x p e c t e d a g r e e m e n t c o n s i d e r i n g t h e d i f fe r en c e i n fl o w c h a r a c t e r -

i st ic s in t h e l o w e r p r of il e . C o m p a r i n g F i g s. 5 a n d 6 s h o w s t h a t t h e h i g h s u c t i o n s w h i c h

r e s u l t f r o m f l o w s e p a r a t i o n a t t h e w i n d w a r d s h a r p e a v e s f o r a t r a n s v e r s e (0 = 1 8 0 )

w i n d d i r e c t i o n a r e s i g n i f i c a n t l y u n d e r e s t i m a t e d a t m o d e l s c a l e c o m p a r e d w i t h t h o s e

m e a s u r e d a t fu ll s ca le , P r e v i o u s c o m p a r i s o n s m a d e b y R i c h a r d s o n [ 7 ] f o r t h is s a m e

t a p b u t w i th t h e c u r v e d e a v e s c o n f i g u r a t i o n i n p l a c e s h o w c l o s e a g r e e m e n t b e t w e e n

f u ll -s c a le a n d m o d e l s u c t i o n s t h e e x p l a n a t i o n fo r t h is is t h a t t h e c u r v e d e a v e s

p r o d u c e a c o n t r a s t i n g a t t a c h e d f l o w r e g i m e , a s d e m o n s t r a t e d b y f u l l - s c a l e f l o w

v i s u a l i s a t i o n , f o r w h i c h m u c h c l o s e r m o d e l - s c a l e p r e d i c t i o n s a r e a t t a i n a b l e .

F igs . 7 a nd 8 r e l a t e t o a s e n so r on a s ide wa ll ne a r t he ga b le e nd . F ig . 7 a ga in show s

g o o d a g r e e m e n t b e t w e e n t h e f u ll -s c a le d a t a s e ts , in t h i s c a s e fo r a s i d e -w a l l t a p a t 3 m

h e i g h t l o c a t e d 0 .5 m f r o m t h e g a b l e e n d o f t h e s h a r p e a v e d b u i l d in g . I n c o n t r a s t , F i g . 8

i l l u s tr a t e s w i n d - t u n n e l d i f f e r en c e s p o s s i b l y a t t r i b u t a b l e t o t h e b o u n d a r y l a y e r d i ff e r-

e n c e s a f f e ct i n g t h e fl o w a r o u n d t h e b u i l d in g . T h e h i g h e r m a x i m u m Cp v a l u e s f ro m t h e

B R E w i n d - t u n n e l i n d i c a te s t h e s t a g n a t i o n o f a s t r e a m l i n e f ro m a r e g i o n h i g h e r in t h e

b o u n d a r y l a ye r . T h e d i ff e re n c e b e t w e e n t h e Cv v a l u e s f o r w i n d d i r e c t i o n s 2 7 0 - 3 1 5 is

p o s s i b ly i n d i c a t iv e o f t h e h i g h e r f r e e - s tr e a m t u r b u l e n c e i n t e n s it y c l o se t o t h e g r o u n d

i n th e B R E w i n d - t u n n e l r e s u l t i n g in a m o r e n e g a t i v e s e p a r a t i o n p r e s s u r e . L i e t a l. [ 9 ]

i n d i c a t e t h a t t h is is d u e t o a r e d u c t i o n i n t h e s i ze o f t h e s e p a r a t i o n b u b b l e . A c o m p a r i -

s o n o f F ig s . 7 a n d 8 s h o w s c l o s e a g r e e m e n t b e t w e e n f u l l- s ca l e a n d m o d e l - s c a l e m e a n

p v a lu e s . T h e m a x i m u m a n d m i n i m u m f u ll -s c a le C~ v a l u e s f al l w i t h i n t h e b o u n d s o f

t h e t w o s e t s o f m o d e l - s c a l e r e su l ts . I n th i s c o m p a r i s o n , t h e s u c t i o n p r o d u c e d i n t h e

w i n d t u n n e l f o r t h e b e s t b o u n d a r y l a y e r s i m u l a t i o n h a s r e p r o d u c e d t h e m i n i m u m

f u l l - s c a l e suc t ion a c c u r a t e ly .


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G.M. Richard son e t al . / J . Wind Eng. Ind. Aerodyn. 72 1997) 18 7-1 97 195

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F i g . 7 . F u l l - s c a le d a t a c o m p a r i s o n : s h a r p e a v e d b u i l d i n g , s i d e - w a l l t a p n e a r t h e g a b l e e n d .

5 D i s c u s s i o n

T h e d i ff er en c es b e t w e e n t h e m i n i m u m m e a n pm e a s u r e d a t f u ll a n d m o d e l s c al e a s

i l l u s tr a t e d in F ig s . 5 a n d 6 h a v e a l s o b e e n o b s e r v e d b y O k a d a e t al. [ 1 0 ] w h e n m a k i n g

s i m i l a r c o m p a r i s o n s o f d a t a f r o m t h e T e x a s T e c h B u i l d i n g ( T T B ) . C o c h r a n e t al. [ 1 1 ]

i n v e s t i g a t e d t h e e ff ec t o f d e p a r t i n g f r o m g e o m e t r i c a ll y s ca l ed t a p p i n g p o i n t a r e a s f o r

t h e T T B , b u t t h e y c o n c l u d e d t h a t c o r r e c t s i m i li tu d e is o n l y n e c e s s ar y w h e n t h e s ca le o f

t h e f l o w is c o m p a r a b l e t o t h e t a p s iz e. T h u s , i t c a n b e c o n c l u d e d t h a t t h is e f fe c t d o e s

n o t c o n t r i b u t e t o t h e d i f fe r en c e s i n m e a n

p

b e t w e e n f ul l- a n d m o d e l - s c a l e re s u lt s o n

t h e S S B . C o c h r a n e t a l. [ 1 1 ] a l s o s u g g e s t e d t h a t v i s c o u s s t r es s e s i n t h e s m a l l m o d e l l e d

v o r t i c e s w o u l d b e d i s p r o p o r t i o n a t e l y l ar g e (a v o r t e x R e y n o l d s n u m b e r e ff ec t) . C o o k

h a s m a d e a s im i l a r c o m m e n t r e c o r d e d i n t h e d i sc u s s i o n o f R i c h a r d s o n e t al. [ 7 ].

T h u s , a s f ar a s m e a n C p 's a r e c o n c e r n e d , w i n d t u n n e l s m a y b e u s e d t o e s t i m a t e

w i n d l o a d s o v e r t h e m a j o r i t y o f t h e s u r fa c e o f a b u i l d in g . H o w e v e r , r e g io n s

o f s e p a r a t e d a n d c o n i c a l - v o r t e x f lo w a re l ik e l y t o p r o d u c e u n d e r e s t i m a t i o n s o f

s u r f a c e p r e s s u r e s a t m o d e l s c a l e . F u r t h e r m o r e , t h e s t r e a m l i n e s i n f l u e n c i n g t h e s e

f lo w r e g i o n s o r i g i n a t e f r o m c l o s e to t h e g r o u n d , j u s t w h e r e i t is m o s t d i ff ic u lt t o

s u s t a i n t h e s h e a r - f l o w c h a r a c t e r i s t i c s a c c u r a t e l y i n a w i n d t u n n e l . T h i s p r o b l e m

i s l ik e l y t o b e a c c e n t u a t e d w i t h l o n g b u i l d i n g s a s t h e f lo w b e c o m e s m o r e t w o -

d i m e n s i o n a l a n d h e n c e t h e s e p a r a t e d f l o w w ill o r i g i n a t e f r o m e v e n l o w e r s t r e a m l i n e s

i n th e p r o fi le as m o r e o f th e a p p r o a c h f lo w g oe s o v e r r a th e r t h a n a r o u n d t h e

o b s t r u c t i o n .


10/11

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V ig . 8 . M o d e l - s c a l e d a t a c o m p a r i s o n : s h a r p e a r e d b u i l d in g , s id e - w a l l t a p n e a r t h e g a b l e en d .

T h e s i g n if i c an c e o f t h e p r e s e n t f u ll -s c a le d a t a a n d c o m p a r i s o n s w i t h w i n d - t u n n e l

m e a s u r e m e n t s i s t h a t m o r e m e a n i n g f u l m o d e l - s c a l e d a t a w o u l d r e s u l t i f t h e f ul l- s ca l e

p r a c t i c e o f s i m u l t a n e o u s l y m e a s u r i n g s u r f a c e a n d n e a r - f ie l d r e f e r e n c e p r e s s u r e s w a s

a d o p t e d i n t h e w i n d t u n n e l . T h i s w o u l d n e c e s s i ta t e a d e q u a t e s a m p l i n g r a t e s a n d

f r e q u e n c y re s p o n s e s a n d c o r r e c t i o n o f t h e u n d e r e s t i m a t i o n o f s t at i c p r e s s u re f r o m t h e

p i t o t - s t a t i c p r o b e i n t u r b u l e n t b o u n d a r y l a y e r s .

6 C l o s i n g r e m a r k s

T h e S i ls o e S tr u c t u r e s B u i l d i n g h a s b e e n t h e f o ca l p o i n t o f a n i n t e r a c t iv e p r o g r a m m e

o f c o m p a r i s o n s o f w i n d - l o a d d a t a . T h e c u r v e d e a v e s fe a t u r e h a s h i g h l i g h t e d h o w s m a l l

a r c h i t e c t u r a l c h a n g e s c a n h a v e s i g n i fi c a n t e ff ec ts o n l o a d d i s t r i b u t i o n . M o r e

r e l i a b l e w i n d - t u n n e l t e c h n i q u e s h a v e r e s u l t e d f r o m i m p r o v e m e n t s t o b o u n d a r y l a y e r

g e n e r a t i o n a n d f r o m t h e a d o p t i o n o f f u ll -s ca le m e a s u r e m e n t p r a c ti c es . T h e u s e o f

r e m o t e r e f e r e n c e p r e s s u r e s c a n r e s u l t i n r e li a b l e m e a n Cp d a t a f r o m w i n d t u n n e l s .

H o w e v e r , s t a ti s ti c s r e l a t e d t o t r a n s i e n t f l o w c h a r a c t e r i s t i c s a r e m o r e m e a n i n g f u l i f

s i m u l t a n e o u s l o c a l r e fe r e n ce p r e s su r e s a n d d i r e c t i o n d a t a a r e u s e d i n n o r m a l i s i n g t h e

s u r f a c e p r e s s u r e d a t a . T h e f u t u r e r e l i ab i l i ty o f w i n d - t u n n e l d a t a d e p e n d s o n t h e

i n c o r p o r a t i o n o f t h e l e ss o n s l e a rn t , i n t o c o d e s o f l a b o r a t o r y p r a c ti c e. T h e r e r e m a i n s

e v i d en c e , h o w e v e r , t h a t a t m o d e l s ca le v i sc o u s d a m p i n g a t t e n u a t e s t h e m a g n i t u d e

o f t h e p r e s s u r e f i el d i n s e p a r a t e d a n d v o r t e x f lo w s , a n d h e n c e c o r r e c t i o n n e e d s

t o b e a p p l i e d f o r R e y n o l d s n u m b e r e f fe c ts i n th e s e r e g i o n s - w o r k is c o n t i n u i n g

on th is .


11/11

G.M. Richard son e t al . / J . W ind Eng. Ind. Aerodyn. 72 1997) 18 ~ 1 9 7 197

cknowledgements

This programme of work was funded by the UK Ministry of Agriculture Fisheries

and Food and the Building Research Establishment. Financial assistance was also

received from the Natural Sciences and Engineering Research Council of Canada

through operating grants made available to D. Surry and A.G. Davenport at the

University of Western Ontario.

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fac il it ie s, Di v . Not e D N 1482, A FR C Ins t i t u t e o f Eng i nee r i ng Resea rch , S il soe , U K , 1988, pp 1-59 .

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t o w i n d l o a d i n g o n l o w - r i s e b u i l d i n g s , J . W i n d E n g . I n d . A e r o d y n . 4 1 - 4 4 1 9 92 ) 3 1 7 -3 2 7 .

[3] R .P . Hoxey , P . J . R i cha rds , G.M . R i cha rdson , A.P . Robe r t son , J .L . Shor t , The S i l soe s t ruc t ure s

b u i l d i n g : t h e c o m p l e t e d e x p e r i m e n t P a r t 2 , P r o c . 9 t h I n t . C o n f . o n W i n d E n g i n e e r i n g , N e w D e l h i .

I n d i a , 9 - 1 3 J a n u a r y 1 9 9 5 .

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1979) 752 753.

[ 5 ] G . M . R i c h a r d s o n , D . S u r r y , T h e S i l so e b u i l d in g : c o m p a r i s o n b e t w e e n fu ll- sc ale a n d w i n d - t u n n e l d a t a ,

J . W i nd Eng . Ind . Ae rodyn . 5 l 1994) 157 176 .

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mo de l an d ful l- scal e, J . W i nd En g . Ind . Ae rodyn . 41-44 1992) 1653-1664 .

[ 7 ] G . M . R i c h a r d s o n , P . A . B l a c k m o r e , T h e S i l s o e s t r u c t u r e s b u i ld i n g : c o m p a r i s o n o f 1 :1 0 0 m o d e l - s c a l e

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Richardson 1997

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