Hello fellow Stressers!!

I have seen this formula for resultant slug force at a bend showing (FR=density * velocity^2 * A * SQRT[2*(1-cos*bend angle)].

For a 45 deg bend angle this will result in a resultant force [FR=0.766 * density * velocity^2 * A], which is less than 1. This will be resolved into two component of force.

Does this mean, that for a 45 deg bend angle, the resulting impact of slug force will be less than 90 deg. bend angle. I'm confused on how the formula is derived.

Kindly share your thoughts.

Cheers!!

See
http://forums.coade.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=60278

BR

Thanks Mariog for sharing especially the attachment.

How about for 5D bends, what would be the possible impact.

Warm Regards!!

We know from particle physics that F=v2/r, and larger r without changing v means less force - for *slug* loads.

It also means that larger slugs can be better approximated as particle loads.

From a time transient perspective, it also slows down the ramp up and ramp down of the load, thereby making the dynamic load factor increasingly conservative.

After all, an infinitely large radius bend exerts no load.

Here's a thought experiment.

Draw a 90 degree bend. Plot a point located at x=y away from the bend. Draw a straight line from the bend midpoint to this point. this vector represents the load under the simplified method.

Water stops moving in the x direction. Water starts moving in the y direction.

Draw a second 90 degree bend. Plot a point at x2=y2 away from the bend. x2 and y2 will be smaller than x=y. Assuming the midpoint of the bend is 0,0, then also plot a point at x2,0 and a point at 0,y2. Plot 2 semicircles, using these 2 points as their center, and 0,0 and x2,y2 as their end points.

It'll look like a lens rotated at 45 degrees.

As a particle travels into this bend, the vector of the force will follow this shape in a clockwise fashion, at a linear angular velocity. Squint hard enough, and it looks like the simplified case.

In a simplified (laminar flow) frame of mind, this doesn't change for a fluid slug.

Take a "short" slug for example (L < length of elbow). The beginning of that slug will follow the same path as the particle. And the end of that slug will also follow the same path as the particle. It'll still act like a particle acting from the slug center.

But for a "long" slug (L > length of elbow), it'll act similarly, except the force will "pause" while the elbow is full and point in a stead direction.

Of course, like mariog's link indicates, slug flow in a bend is hardly laminar, and fluid doesn't really ever act as a solid mass. I would expect that as the slug cascades and crashes over itself, you're going to see a mess of noise in all sorts of directions.

We don't really have that research readily available.

Thanks Mariog for that very nice explanation. It clears my mind and as an engineer, there are really many things that are not straight forward.

Cheers!!

Thanks Michael & Mariog I mean.

Warm Regards,