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Wind effects on building with varying leakage characteristics — wind tunnel investigation
Journal of Industrial Aerodynamics, 5 (1979) 193--194
193
© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
Discussion WIND EFFECTS ON BUILDING WITH VARYING L E A K A G E CHARACTERISTICS -- WIND TUNNEL INVESTIGATION
B.S. KANDOLA
Department of Fire Safety Engineering, University of Edinburgh, Edinburgh (Gt. Britain) (Received March 21, 1979)
Response to discussion contribution by T. Stathopoulos* In response to Dr. Stathopoulos, the following c o m m e n t s are offered. 1. It is correct to presume that the pressure coefficients presented in the paper are the relationships o f the mean measured surface pressures referred to in the dynamic pressure measured at the roof height of the model when the model is absent from the tunnel working section. 2. The a u t h o r of the paper cannot agree that all the internal pressure coefficients are "drastically c o n t a m i n a t e d " due to the model having flexible sides. This is because when a leakage is given to the sides, the influence of any flexure of the model on the pressures developed is not likely to be significant. Only in the case of zero leakage will internal flexure induced pressures become important. The change in internal pressures, for zero leakage, with the wind angle may be due to the presence o f the partition which gives added stiffness to two walls. It is unlikely t h a t the changes in internal pressure were due to any leakage in the base as such leakage should give rise to an internal pressure which is constant and independent o f wind direction. Referring to Figs. 12 and 13, the internal pressures for zero leakage change with wind direction which helps to confirm the above comment in that the pressure changes are due to volume change. 3. It is admitted that a discrepancy exists between Figs. 10 and 11. The values in Fig. 11 are correct but these in Fig. 10 were miscalculated and should be multiplied by 4. 4. The differences between the results presented in Fig. 6 and 9 are most likely to be the consequence o f experimental errors probably due to small variations in model alignment. 5. As noted earlier, the values presented in Fig. 10 are four times too small, but this does not invalidate the sample calculation as such low pressure coefficients do exist on part of the roof. It is agreed that more complicated calculations would be required to analyse a real system. In such calculations an average A Cp~oof would still be appropriate, providing that the area of r o o f used is a direct reflection o f the internal space beneath [12]. *J. Ind. Aerodyn., 5 (1979) 191--192.
194
6. The results presented in Fig. 14 are given for values o f R up to 5 as additional measurements were made with other leakage combinations b u t not reported in the earlier part of the paper. 7. The conclusions drawn from Fig. 14 are not in conflict with the content of the figure. Taking the corrected values from Fig. 10, the average outside pressure coefficient on the r o o f is a b o u t --0.68 (when a = 90 ° ). From Fig. 14 the values for Cpi (when ~ = 90 ° ) vary with leakage ratio from a b o u t - 0 . 7 6 to - 0 . 8 6 . These values are all greater than the outside pressure, hence the statement that "all vents will fail" still holds good for the specified conditions. Naturally, some points on the r o o f will have negative pressure coefficients greater than the internal negative pressure coefficients, then vents in these locations will n o t fail (i.e. the flow of air and any smoke would be from the inside to the outside of the building with this particular pressure system). 8. As Fig. 15 in the printed paper was calculated from the same data as Fig. 10, a corrected Fig. 15 is presented here and it is agreed that this gives values relevant to the specified conditions only (e.g. wind speed and fire size). 2.5
o, < 2,0
o----o
c< = 4 5
\
'¢ /.5
u /.0
0.£
I
I
I
I
I
i.o
2.0
3.o
,~o
5.o
LEAKAGE RATIO, R
Fig. 15. V a r i a t i o n o f critical v e n t area
(Avcrlt) w i t h leakage ratio
9. It should be noted that the paper design aid b u t as a contribution to the it attempts to show that the effects of terms o f the success or the failure o f a
R, f o r a = 0 ° , 45 ° .
presented was not intended as a study of smoke control systems and the natural wind can be significant in smoke vent system.
Reference
12
J. Morgan and E.W. M a r c h a n t , S o m e e f f e c t s o f natural w i n d o n vent operation in shopping malls, P a p e r 13 in CIB S y m p o s i u m o n t h e C o n t r o l o f S m o k e Movement in Building Fires, pp. 1 7 1 - - 1 8 3 .
193
© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
Discussion WIND EFFECTS ON BUILDING WITH VARYING L E A K A G E CHARACTERISTICS -- WIND TUNNEL INVESTIGATION
B.S. KANDOLA
Department of Fire Safety Engineering, University of Edinburgh, Edinburgh (Gt. Britain) (Received March 21, 1979)
Response to discussion contribution by T. Stathopoulos* In response to Dr. Stathopoulos, the following c o m m e n t s are offered. 1. It is correct to presume that the pressure coefficients presented in the paper are the relationships o f the mean measured surface pressures referred to in the dynamic pressure measured at the roof height of the model when the model is absent from the tunnel working section. 2. The a u t h o r of the paper cannot agree that all the internal pressure coefficients are "drastically c o n t a m i n a t e d " due to the model having flexible sides. This is because when a leakage is given to the sides, the influence of any flexure of the model on the pressures developed is not likely to be significant. Only in the case of zero leakage will internal flexure induced pressures become important. The change in internal pressures, for zero leakage, with the wind angle may be due to the presence o f the partition which gives added stiffness to two walls. It is unlikely t h a t the changes in internal pressure were due to any leakage in the base as such leakage should give rise to an internal pressure which is constant and independent o f wind direction. Referring to Figs. 12 and 13, the internal pressures for zero leakage change with wind direction which helps to confirm the above comment in that the pressure changes are due to volume change. 3. It is admitted that a discrepancy exists between Figs. 10 and 11. The values in Fig. 11 are correct but these in Fig. 10 were miscalculated and should be multiplied by 4. 4. The differences between the results presented in Fig. 6 and 9 are most likely to be the consequence o f experimental errors probably due to small variations in model alignment. 5. As noted earlier, the values presented in Fig. 10 are four times too small, but this does not invalidate the sample calculation as such low pressure coefficients do exist on part of the roof. It is agreed that more complicated calculations would be required to analyse a real system. In such calculations an average A Cp~oof would still be appropriate, providing that the area of r o o f used is a direct reflection o f the internal space beneath [12]. *J. Ind. Aerodyn., 5 (1979) 191--192.
194
6. The results presented in Fig. 14 are given for values o f R up to 5 as additional measurements were made with other leakage combinations b u t not reported in the earlier part of the paper. 7. The conclusions drawn from Fig. 14 are not in conflict with the content of the figure. Taking the corrected values from Fig. 10, the average outside pressure coefficient on the r o o f is a b o u t --0.68 (when a = 90 ° ). From Fig. 14 the values for Cpi (when ~ = 90 ° ) vary with leakage ratio from a b o u t - 0 . 7 6 to - 0 . 8 6 . These values are all greater than the outside pressure, hence the statement that "all vents will fail" still holds good for the specified conditions. Naturally, some points on the r o o f will have negative pressure coefficients greater than the internal negative pressure coefficients, then vents in these locations will n o t fail (i.e. the flow of air and any smoke would be from the inside to the outside of the building with this particular pressure system). 8. As Fig. 15 in the printed paper was calculated from the same data as Fig. 10, a corrected Fig. 15 is presented here and it is agreed that this gives values relevant to the specified conditions only (e.g. wind speed and fire size). 2.5
o, < 2,0
o----o
c< = 4 5
\
'¢ /.5
u /.0
0.£
I
I
I
I
I
i.o
2.0
3.o
,~o
5.o
LEAKAGE RATIO, R
Fig. 15. V a r i a t i o n o f critical v e n t area
(Avcrlt) w i t h leakage ratio
9. It should be noted that the paper design aid b u t as a contribution to the it attempts to show that the effects of terms o f the success or the failure o f a
R, f o r a = 0 ° , 45 ° .
presented was not intended as a study of smoke control systems and the natural wind can be significant in smoke vent system.
Reference
12
J. Morgan and E.W. M a r c h a n t , S o m e e f f e c t s o f natural w i n d o n vent operation in shopping malls, P a p e r 13 in CIB S y m p o s i u m o n t h e C o n t r o l o f S m o k e Movement in Building Fires, pp. 1 7 1 - - 1 8 3 .