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-   -   Cd value....hole in a rectangular tank.... (http://www.cfd-online.com/Forums/fluent/38387-cd-value-hole-rectangular-tank.html)

karthik October 26, 2005 10:44

Cd value....hole in a rectangular tank....
 
hello ppl

my problem is described in the link given below....

http://www.geocities.com/karthik_machomech/hole.bmp

if there is no hole in the rectangular box,(only external flow), i'm getting a Cd value of 1.59

after making the hole, what shud be the reference area i have to input?? for external flow i gave frontal area....

with hole wat area shud be given as reference area??? and shud the Cd increase or decrease?? actually with both internal and external flow i expected the drag to increase.....

but i took the same frontal area as reference area for flow with the hole and found the Cd value getting decreased......please help me frens....any help is highly appreciated.....thanks a lot in advance....

expecting ur replies....

regards

karthik

sai shiva muppur October 29, 2005 11:49

Re: Cd value....hole in a rectangular tank....
 
hi karthik,

for 2D models i have used unit area as frontal area. Not sure if that is correct. Or you can use the actual area and make sure you mention it. dont you have any measurements of force values for validation?

karthik October 29, 2005 13:11

Re: Cd value....hole in a rectangular tank....
 
hi sai

i don't have any values for validation....if i use the actual area (reduced area-exluding the hole region), then the Cd value increases....if i use the frontal area(which i used when there r no holes, the Cd decreases)...

i'm not sure what to use...i'll talk to my professor and tell u... meanwhile, anybody having any idea...pls help me... thanks... regards

karthik


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