# Friction at walls

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April 17, 2013, 04:42
Friction at walls
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Hi everyone,

Problem description:
Fuel zone( represented by porous zone ) is vertically as well as horizontally separated to sectors in order to model areas with different hydraulics and power distribution. Although there was set zero shear stress (Picture 1) on all separation walls, the coolant has a lower velocity at walls (seems like nonzero wall friction). You can see the lower velocity on velocity contours: horizontal (Picture 2) and vertical (Picture 3). The friction wall effect is undesirable.

Question:
How to set boundary conditions to eliminate undesirable „friction forces“ that have occurred at separating walls?

Description of the model:
1. 3D model represents a typical spent fuel pool coolant.
2. Regions of fuel channels are set as „porous zones“.
3. Flow of coolant (water) is forced up from the bottom of the pool.
4. Heat generation in each fuel channel is homogenous.

Setting:
Solver – pressure based, absolute, steady, gravity
Models – energy, k-epsilon, realizable, standard wall functions
Methods – SIMPLE, second order

Regards, roupcik.
Attached Images
 Picture1.jpg (52.0 KB, 6 views) Picture2.jpg (48.3 KB, 8 views) Picture3.jpg (37.8 KB, 8 views)

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