Wide Pier in Shallow Water
This method introduces a correction factor for a wide pier in shallow water. The experimental data used in the analysis have flow depth to pier width ratios in the range of 0.2 and 0.8. Therefore use of this data outside of these limits is not recommended.
The correction factor is as follows
Kw= 2.58*(y1/a)0.34*Fr10.65 for V1/Vc<1
Kw= (y1/a)0.13*Fr10.25 for V1/Vc>=1
Where:
y1= flow depth upstream of pier
a= pier width
Fr1= Frounde Number
V1= Flow velocity upstream of pier
Vc= Critical velocity
The Neill's critical velocity is used as the default in the program. The above correction factor Kw is applied to basic pier scour equation to get the scour depth for wide pier in shallow water.
Limitations of Kw correction factor:
- Only sand bed streams were available for calibration with (a/D50)>50. Use on gravel bed streams should be avoided or used cautiously.
- y1/a values less than 0.8
- Froude Number less than 1
Use of the correction factor outside these limits is not recommended. The program will assign Kw to 1 if the about limitation is exceeded.