Slug force is equal to the change in momentum with respect to time.
While performing slug flow analysis the following two assumptions are made
It is assumed that the slug is formed across the full cross-section of the pipe for the maximum impact. This configuration is least probable for vertically down word flow as no hold – up is possible for the accumulation of liquid and eventual formation of the slug. Hence slug force at elbows for vertically downward flow lines is not considered.