Calculations
Head loss in water treatment 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
Head Loss in Water Treatment Trash Racks
This calculation determines the head loss across trash racks used in water treatment, evaluating upstream and downstream depths, velocities, specific energies, and head loss for both clean and 50% obstructed conditions.
Trash rack
Calculation Methods
-
Given downstream depth
Calculates parameters based on provided downstream water depth. -
Given upstream depth
Calculates parameters based on provided upstream water depth.
Inputs and Outputs
Inputs
Parameter | Units | Description |
|---|---|---|
Flow ($Q$) | m³/s | Water volumetric flow rate |
Channel width ($b$) | m | Width of the channel |
Bar width ($w$) | m | Width of the trash rack bars |
Distance between bars ($d$) | m | Spacing between bars |
Downstream water depth ($y_j$) | m | Water depth at the downstream side |
Upstream water depth ($y_m$) | m | Water depth at the upstream side |
Bar slope (𝝓) | deg | Angle of the bars relative to the flow |
Kirschmer $\beta$ | - | Dimensionless Kirschmer coefficient |
Outputs
Parameter | Units | Description |
|---|---|---|
Flow ($Q_{out}$) | m³/s | Volumetric flow rate |
Upstream velocity ($U_m$) | m/s | Velocity at the upstream |
Upstream energy ($E_m$) | J | Specific energy at the upstream |
Upstream water depth ($y_m$) | m | Water depth at the upstream |
Downstream velocity ($U_j$) | m/s | Velocity at the downstream |
Between bars velocity ($U$) | m/s | Average velocity between bars |
Downstream energy ($E_j$) | J | Specific energy at the downstream |
Head loss ($H_f$) | m | Total head loss |
Water level difference ($y_m - y_j$) | m | Height difference between upstream and downstream |
Upstream depth at 50% obstruction ($y_{50%}$) | m | Upstream depth considering 50% obstruction |
Upstream velocity at 50% obstruction ($U_{m50%}$) | m/s | Upstream velocity considering 50% obstruction |
Upstream energy at 50% obstruction ($E_{m50%}$) | J | Upstream energy considering 50% obstruction |
Head loss at 50% obstruction ($H_{f50%}$) | m | Head loss considering 50% obstruction |
Between bars velocity at 50% obstruction ($U_{50%}$) | m/s | Velocity between bars at 50% obstruction |
Water level difference at 50% obstruction ($y_{50%} - y_j$) | m | Height difference at 50% obstruction |
References
- PESSOA, Constantino A. Tratamento de esgotos domésticos. 7. ed. Rio de Janeiro, ABES, 2014.