Vortex shedding is mandatory for all the bluff bodies ?

[eswarm21]

Vortex shedding is mandatory for all the bluff bodies ??

Vortex shedding is mandatory for all the bluff bodies ??

for example, flow over a low thickness flat plate with zero attach angle and flow over the very low depth dish antenna (like U shape)

is there any shape (with particular conditions) is exempt from shedding... ?

 

[boneh3ad]

I don't think many people would consider a flat plate a bluff body. At any rate, not all bluff bodies undergo vortex shedding. It will depend on the separation dynamics, which depends on the shape and the flow around the body. Take, for example, Stokes flow. You can have a sphere or a cylinder, two bodies noted for their shedding behavior, and if the Reynolds number is tiny, you have no shedding. On the other hand, you could have an airfoil shape that normally has no shedding but when it gets to a high enough angle of attack, the flow over the upper half separates and vortex shedding occurs.

 

[SteamKing]

The term 'mandatory' suggests that vortex shedding has been decreed by some agency.

Vortices are formed because real fluids (air, water, etc.) are affected by friction when flowing over a body.

 

[eswarm21]

Thanks for quick reply !...One more ...i would like to study air load on structure .. But i am going to use water as a medium in wind tunnel experiment. I am matching with Re and St numbers . Now will gravity affect the solution (thermal effects are negligible) in terms of load on structure and vortex shedding? if so what we need to be done in this case?

 

[boneh3ad]

Well in the sense that buoyancy is gravity-driven, then yes. If you are studying forces on something submerged in any fluid, buoyancy exists. In air it is usually negligible. In water it is often important.