Calculations
Head loss in sewer trash racks
Input data
Flow (Q)
Channel width (b)
Bar width (w)
Distance between bars (d)
Downstream water depth (yj)
Bar slope (𝝓)
Kirschmer β
Output data
Upstream velocity (Um)
Upstream energy (Em)
Upstream water depth (ym)
Downstream velocity (Uj)
Between bars velocity (U)
Downstream energy (Ej)
Head loss (Hf)
Water level difference (ym - yj)
Upstream depth at 50% obstruction (ym50%)
Upstream velocity at 50% obstruction (Um50%)
Upstream energy at 50% obstruction (Em50%)
Head loss at 50% obstruction (hf50%)
Between bars velocity at 50% obstruction (U50%)
Water level difference at 50% obstruction (ym50% - yj)
Input data
Flow (Q)
Channel width (b)
Bar width (w)
Distance between bars (d)
Bar slope (𝝓)
Kirschmer β
Output data
Upstream velocity (Um)
Upstream energy (Em)
Downstream velocity (Uj)
Between bars velocity (U)
Downstream energy (Ej)
Head loss (Hf)
Water level difference (ym - yj)
Head loss at 50% obstruction (hf50%)
Between bars velocity at 50% obstruction (U50%)
Water level difference at 50% obstruction (ym - yj50%)
Description
Given the flow, channel geometry, and screen characteristics, this tool calculates the downflow water level if the upflow water level is known, or the upflow water level if the downflow water level is known. This is particularly useful in wastewater systems where trash racks are used to remove solids.
Head Loss in Sewer Trash Racks Image
Available Calculation Methods
1. Downflow
Calculates the upflow water level, velocity, and energy, considering the known downflow water level.
Inputs:
| Parameter | Unit | Description |
|---|---|---|
| Flow (Q) | m³/s | Inlet flow |
| Width (b) | m | Width of the channel |
| Trashrack width (W) | m | Thickness of the trashrack |
| Distance between trashracks (d) | m | Spacing between the trashracks |
| Downflow level (y) | m | Water level at downflow |
| Slope (º) | - | Slope angle of the trashrack |
| β - Kirschmer | - | Kirschmer coefficient |
Outputs:
| Parameter | Unit | Description |
|---|---|---|
| Upflow level (ym) | m | Water level at upflow |
| Upflow velocity (Um) | m/s | Flow velocity at upflow |
| Energy (Em) | J | Energy at the upflow |
| Velocity between bars (Ubb) | m/s | Flow velocity between bars |
| Head loss (Hl) | m | Head loss in the system |
2. Upflow
Calculates the downflow water level, velocity, and energy, considering the known upflow water level.
Inputs:
| Parameter | Unit | Description |
|---|---|---|
| Flow (Q) | m³/s | Inlet flow |
| Channel width (b) | m | Width of the channel |
| Trashrack width (W) | m | Thickness of the trashrack |
| Distance between trashracks (d) | m | Spacing between the trashracks |
| Upflow level (ym) | m | Water level at upflow |
| Slope (º) | - | Slope angle of the trashrack |
| β - Kirschmer | - | Kirschmer coefficient |
Outputs:
| Parameter | Unit | Description |
|---|---|---|
| Downflow level (y) | m | Water level at downflow |
| Downflow velocity (U) | m/s | Flow velocity at downflow |
| Energy (E) | J | Energy at the downflow |
| Velocity between bars (Ubb) | m/s | Flow velocity between bars |
| Head loss (Hl) | m | Head loss in the system |
References
- PESSOA, Constantino A. Tratamento de esgotos domésticos. 7. ed. Rio de Janeiro, ABES, 2014.