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Rose Equation

Environmental Engineering · FE Reference Handbook section

Environmental Engineering
1 formulas
10 exam-style examples
~47 min
All Environmental Engineering lectures

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • Monosized Media Multisized Media

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1
Rose Equation — solve for headloss through clean bed — Rose Equation

Rose equation headloss through a clean rapid sand filter bed Given drag coefficient (C_D) = 2.2000; filter media depth (L) = 0.7900 m; filtration velocity (v_f) = 0.0038 m/s; shape factor (phi) = 0.8700; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0019 m; porosity (eps) = 0.4040, determine the headloss through clean bed (h_L) in m.

Given

  • dragcoefficient(CD)=2.2000drag coefficient (C_D) = 2.2000
  • filtermediadepth(L)=0.7900mfilter media depth (L) = 0.7900 m
  • filtrationvelocity(vf)=0.0038m/sfiltration velocity (v_f) = 0.0038 m/s
  • shapefactor(phi)=0.8700shape factor (phi) = 0.8700
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0019mgrain diameter (d) = 0.0019 m
  • porosity(eps)=0.4040porosity (eps) = 0.4040

Find

headloss through clean bed (h_L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except h_L is given, so isolate h_L symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for h_L:

    hL=1.067CDLvf2ϕgd ϵ4h_{L} = \dfrac{1.067C_DLv_f^2}{\phi g d \,\epsilon^4}
  3. Step 3 — List the givens: drag coefficient (C_D) = 2.2000, filter media depth (L) = 0.7900 m, filtration velocity (v_f) = 0.0038 m/s, shape factor (phi) = 0.8700, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0019 m, porosity (eps) = 0.4040.

  4. Step 4 — Substitute the given values:

    hL=1.067CDLvf20.87009.81000.0019 ϵ4h_{L} = \dfrac{1.067C_DLv_f^2}{0.8700 9.8100 0.0019 \,\epsilon^4}
  5. Step 5 — Evaluate:

    hL=0.0620 mh_{L} = 0.0620\ \text{m}
  6. Step 6 — Check: returning h_L = 0.0620 m to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
hL=0.0620 mh_{L} = 0.0620\ \text{m}

Why the other options are there

  • 0.1240 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0310 — dropped that same factor in the other direction.
  • 0.0682 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 2
Rose Equation — solve for filter media depth — Rose Equation (2)

Rose equation used to estimate clean-bed head loss in filtration Given drag coefficient (C_D) = 1.6500; filtration velocity (v_f) = 0.0027 m/s; shape factor (phi) = 0.7800; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0009 m; porosity (eps) = 0.3990; headloss through clean bed (h_L) = 0.6650 m, determine the filter media depth (L) in m.

Given

  • dragcoefficient(CD)=1.6500drag coefficient (C_D) = 1.6500
  • filtrationvelocity(vf)=0.0027m/sfiltration velocity (v_f) = 0.0027 m/s
  • shapefactor(phi)=0.7800shape factor (phi) = 0.7800
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0009mgrain diameter (d) = 0.0009 m
  • porosity(eps)=0.3990porosity (eps) = 0.3990
  • headlossthroughcleanbed(hL)=0.6650mheadloss through clean bed (h_L) = 0.6650 m

Find

filter media depth (L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except L is given, so isolate L symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for L:

    L=hLϕgd ϵ41.067CDvf2L = \dfrac{h_L \phi g d \,\epsilon^4}{1.067C_Dv_f^2}
  3. Step 3 — List the givens: drag coefficient (C_D) = 1.6500, filtration velocity (v_f) = 0.0027 m/s, shape factor (phi) = 0.7800, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0009 m, porosity (eps) = 0.3990, headloss through clean bed (h_L) = 0.6650 m.

  4. Step 4 — Substitute the given values:

    L=hL0.78009.81000.0009 ϵ41.067CDvf2L = \dfrac{h_L 0.7800 9.8100 0.0009 \,\epsilon^4}{1.067C_Dv_f^2}
  5. Step 5 — Evaluate:

    L=8.7422 mL = 8.7422\ \text{m}
  6. Step 6 — Check: returning L = 8.7422 m to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=8.7422 mL = 8.7422\ \text{m}

Why the other options are there

  • 17.4844 — kept a factor of two that cancels in the correct rearrangement.
  • 4.3711 — dropped that same factor in the other direction.
  • 9.6164 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 3
Rose Equation — solve for filtration velocity — Rose Equation (3)

Rose equation filter headloss calculation for uniform media Given drag coefficient (C_D) = 1.6500; filter media depth (L) = 1.4600 m; shape factor (phi) = 0.7500; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0013 m; porosity (eps) = 0.3910; headloss through clean bed (h_L) = 0.7850 m, determine the filtration velocity (v_f) in m/s.

Given

  • dragcoefficient(CD)=1.6500drag coefficient (C_D) = 1.6500
  • filtermediadepth(L)=1.4600mfilter media depth (L) = 1.4600 m
  • shapefactor(phi)=0.7500shape factor (phi) = 0.7500
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0013mgrain diameter (d) = 0.0013 m
  • porosity(eps)=0.3910porosity (eps) = 0.3910
  • headlossthroughcleanbed(hL)=0.7850mheadloss through clean bed (h_L) = 0.7850 m

Find

filtration velocity (v_f), in m/s

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except v_f is given, so isolate v_f symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for v_f:

    vf=hLϕgd ϵ41.067CDLv_{f} = \sqrt{\dfrac{h_L \phi g d\,\epsilon^4}{1.067C_DL}}
  3. Step 3 — List the givens: drag coefficient (C_D) = 1.6500, filter media depth (L) = 1.4600 m, shape factor (phi) = 0.7500, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0013 m, porosity (eps) = 0.3910, headloss through clean bed (h_L) = 0.7850 m.

  4. Step 4 — Substitute the given values:

    vf=h1.46000.75009.81000.0013 ϵ41.067CD1.4600v_{f} = \sqrt{\dfrac{h_1.4600 0.7500 9.8100 0.0013\,\epsilon^4}{1.067C_D1.4600}}
  5. Step 5 — Evaluate:

    vf=0.0083 m/sv_{f} = 0.0083\ \text{m/s}
  6. Step 6 — Check: returning v_f = 0.0083 m/s to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
vf=0.0083 m/sv_{f} = 0.0083\ \text{m/s}

Why the other options are there

  • 0.0165 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0041 — dropped that same factor in the other direction.
  • 0.0091 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 4
Rose Equation — solve for headloss through clean bed (case 2) — Rose Equation (4)

Rose equation headloss through a clean rapid sand filter bed Given drag coefficient (C_D) = 0.5800; filter media depth (L) = 1.2300 m; filtration velocity (v_f) = 0.0043 m/s; shape factor (phi) = 0.9500; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0005 m; porosity (eps) = 0.4080, determine the headloss through clean bed (h_L) in m.

Given

  • dragcoefficient(CD)=0.5800drag coefficient (C_D) = 0.5800
  • filtermediadepth(L)=1.2300mfilter media depth (L) = 1.2300 m
  • filtrationvelocity(vf)=0.0043m/sfiltration velocity (v_f) = 0.0043 m/s
  • shapefactor(phi)=0.9500shape factor (phi) = 0.9500
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0005mgrain diameter (d) = 0.0005 m
  • porosity(eps)=0.4080porosity (eps) = 0.4080

Find

headloss through clean bed (h_L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except h_L is given, so isolate h_L symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for h_L:

    hL=1.067CDLvf2ϕgd ϵ4h_{L} = \dfrac{1.067C_DLv_f^2}{\phi g d \,\epsilon^4}
  3. Step 3 — List the givens: drag coefficient (C_D) = 0.5800, filter media depth (L) = 1.2300 m, filtration velocity (v_f) = 0.0043 m/s, shape factor (phi) = 0.9500, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0005 m, porosity (eps) = 0.4080.

  4. Step 4 — Substitute the given values:

    hL=1.067CDLvf20.95009.81000.0005 ϵ4h_{L} = \dfrac{1.067C_DLv_f^2}{0.9500 9.8100 0.0005 \,\epsilon^4}
  5. Step 5 — Evaluate:

    hL=0.1090 mh_{L} = 0.1090\ \text{m}
  6. Step 6 — Check: returning h_L = 0.1090 m to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
hL=0.1090 mh_{L} = 0.1090\ \text{m}

Why the other options are there

  • 0.2180 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0545 — dropped that same factor in the other direction.
  • 0.1199 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 5
Rose Equation — solve for filter media depth (case 2) — Rose Equation (5)

Rose equation used to estimate clean-bed head loss in filtration Given drag coefficient (C_D) = 2.8600; filtration velocity (v_f) = 0.0040 m/s; shape factor (phi) = 0.8600; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0020 m; porosity (eps) = 0.4470; headloss through clean bed (h_L) = 0.8400 m, determine the filter media depth (L) in m.

Given

  • dragcoefficient(CD)=2.8600drag coefficient (C_D) = 2.8600
  • filtrationvelocity(vf)=0.0040m/sfiltration velocity (v_f) = 0.0040 m/s
  • shapefactor(phi)=0.8600shape factor (phi) = 0.8600
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0020mgrain diameter (d) = 0.0020 m
  • porosity(eps)=0.4470porosity (eps) = 0.4470
  • headlossthroughcleanbed(hL)=0.8400mheadloss through clean bed (h_L) = 0.8400 m

Find

filter media depth (L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except L is given, so isolate L symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for L:

    L=hLϕgd ϵ41.067CDvf2L = \dfrac{h_L \phi g d \,\epsilon^4}{1.067C_Dv_f^2}
  3. Step 3 — List the givens: drag coefficient (C_D) = 2.8600, filtration velocity (v_f) = 0.0040 m/s, shape factor (phi) = 0.8600, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0020 m, porosity (eps) = 0.4470, headloss through clean bed (h_L) = 0.8400 m.

  4. Step 4 — Substitute the given values:

    L=hL0.86009.81000.0020 ϵ41.067CDvf2L = \dfrac{h_L 0.8600 9.8100 0.0020 \,\epsilon^4}{1.067C_Dv_f^2}
  5. Step 5 — Evaluate:

    L=11.3575 mL = 11.3575\ \text{m}
  6. Step 6 — Check: returning L = 11.3575 m to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=11.3575 mL = 11.3575\ \text{m}

Why the other options are there

  • 22.7150 — kept a factor of two that cancels in the correct rearrangement.
  • 5.6787 — dropped that same factor in the other direction.
  • 12.4932 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 6
Rose Equation — solve for filtration velocity (case 2) — Rose Equation (6)

Rose equation filter headloss calculation for uniform media Given drag coefficient (C_D) = 8.9700; filter media depth (L) = 0.9500 m; shape factor (phi) = 0.8200; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0018 m; porosity (eps) = 0.4300; headloss through clean bed (h_L) = 1.6550 m, determine the filtration velocity (v_f) in m/s.

Given

  • dragcoefficient(CD)=8.9700drag coefficient (C_D) = 8.9700
  • filtermediadepth(L)=0.9500mfilter media depth (L) = 0.9500 m
  • shapefactor(phi)=0.8200shape factor (phi) = 0.8200
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0018mgrain diameter (d) = 0.0018 m
  • porosity(eps)=0.4300porosity (eps) = 0.4300
  • headlossthroughcleanbed(hL)=1.6550mheadloss through clean bed (h_L) = 1.6550 m

Find

filtration velocity (v_f), in m/s

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except v_f is given, so isolate v_f symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for v_f:

    vf=hLϕgd ϵ41.067CDLv_{f} = \sqrt{\dfrac{h_L \phi g d\,\epsilon^4}{1.067C_DL}}
  3. Step 3 — List the givens: drag coefficient (C_D) = 8.9700, filter media depth (L) = 0.9500 m, shape factor (phi) = 0.8200, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0018 m, porosity (eps) = 0.4300, headloss through clean bed (h_L) = 1.6550 m.

  4. Step 4 — Substitute the given values:

    vf=h0.95000.82009.81000.0018 ϵ41.067CD0.9500v_{f} = \sqrt{\dfrac{h_0.9500 0.8200 9.8100 0.0018\,\epsilon^4}{1.067C_D0.9500}}
  5. Step 5 — Evaluate:

    vf=0.0095 m/sv_{f} = 0.0095\ \text{m/s}
  6. Step 6 — Check: returning v_f = 0.0095 m/s to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
vf=0.0095 m/sv_{f} = 0.0095\ \text{m/s}

Why the other options are there

  • 0.0189 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0047 — dropped that same factor in the other direction.
  • 0.0104 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 7
Rose Equation — solve for headloss through clean bed (case 3) — Rose Equation (7)

Rose equation headloss through a clean rapid sand filter bed Given drag coefficient (C_D) = 2.1400; filter media depth (L) = 0.7800 m; filtration velocity (v_f) = 0.0045 m/s; shape factor (phi) = 0.8700; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0004 m; porosity (eps) = 0.3700, determine the headloss through clean bed (h_L) in m.

Given

  • dragcoefficient(CD)=2.1400drag coefficient (C_D) = 2.1400
  • filtermediadepth(L)=0.7800mfilter media depth (L) = 0.7800 m
  • filtrationvelocity(vf)=0.0045m/sfiltration velocity (v_f) = 0.0045 m/s
  • shapefactor(phi)=0.8700shape factor (phi) = 0.8700
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0004mgrain diameter (d) = 0.0004 m
  • porosity(eps)=0.3700porosity (eps) = 0.3700

Find

headloss through clean bed (h_L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except h_L is given, so isolate h_L symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for h_L:

    hL=1.067CDLvf2ϕgd ϵ4h_{L} = \dfrac{1.067C_DLv_f^2}{\phi g d \,\epsilon^4}
  3. Step 3 — List the givens: drag coefficient (C_D) = 2.1400, filter media depth (L) = 0.7800 m, filtration velocity (v_f) = 0.0045 m/s, shape factor (phi) = 0.8700, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0004 m, porosity (eps) = 0.3700.

  4. Step 4 — Substitute the given values:

    hL=1.067CDLvf20.87009.81000.0004 ϵ4h_{L} = \dfrac{1.067C_DLv_f^2}{0.8700 9.8100 0.0004 \,\epsilon^4}
  5. Step 5 — Evaluate:

    hL=0.5369 mh_{L} = 0.5369\ \text{m}
  6. Step 6 — Check: returning h_L = 0.5369 m to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
hL=0.5369 mh_{L} = 0.5369\ \text{m}

Why the other options are there

  • 1.0737 — kept a factor of two that cancels in the correct rearrangement.
  • 0.2684 — dropped that same factor in the other direction.
  • 0.5905 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 8
Rose Equation — solve for filter media depth (case 3) — Rose Equation (8)

Rose equation used to estimate clean-bed head loss in filtration Given drag coefficient (C_D) = 6.9800; filtration velocity (v_f) = 0.0040 m/s; shape factor (phi) = 0.8500; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0004 m; porosity (eps) = 0.4540; headloss through clean bed (h_L) = 1.2580 m, determine the filter media depth (L) in m.

Given

  • dragcoefficient(CD)=6.9800drag coefficient (C_D) = 6.9800
  • filtrationvelocity(vf)=0.0040m/sfiltration velocity (v_f) = 0.0040 m/s
  • shapefactor(phi)=0.8500shape factor (phi) = 0.8500
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0004mgrain diameter (d) = 0.0004 m
  • porosity(eps)=0.4540porosity (eps) = 0.4540
  • headlossthroughcleanbed(hL)=1.2580mheadloss through clean bed (h_L) = 1.2580 m

Find

filter media depth (L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except L is given, so isolate L symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for L:

    L=hLϕgd ϵ41.067CDvf2L = \dfrac{h_L \phi g d \,\epsilon^4}{1.067C_Dv_f^2}
  3. Step 3 — List the givens: drag coefficient (C_D) = 6.9800, filtration velocity (v_f) = 0.0040 m/s, shape factor (phi) = 0.8500, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0004 m, porosity (eps) = 0.4540, headloss through clean bed (h_L) = 1.2580 m.

  4. Step 4 — Substitute the given values:

    L=hL0.85009.81000.0004 ϵ41.067CDvf2L = \dfrac{h_L 0.8500 9.8100 0.0004 \,\epsilon^4}{1.067C_Dv_f^2}
  5. Step 5 — Evaluate:

    L=1.4959 mL = 1.4959\ \text{m}
  6. Step 6 — Check: returning L = 1.4959 m to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=1.4959 mL = 1.4959\ \text{m}

Why the other options are there

  • 2.9919 — kept a factor of two that cancels in the correct rearrangement.
  • 0.7480 — dropped that same factor in the other direction.
  • 1.6455 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 9
Rose Equation — solve for filtration velocity (case 3) — Rose Equation (9)

Rose equation filter headloss calculation for uniform media Given drag coefficient (C_D) = 9.5600; filter media depth (L) = 0.7300 m; shape factor (phi) = 0.7400; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0013 m; porosity (eps) = 0.4860; headloss through clean bed (h_L) = 0.3790 m, determine the filtration velocity (v_f) in m/s.

Given

  • dragcoefficient(CD)=9.5600drag coefficient (C_D) = 9.5600
  • filtermediadepth(L)=0.7300mfilter media depth (L) = 0.7300 m
  • shapefactor(phi)=0.7400shape factor (phi) = 0.7400
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0013mgrain diameter (d) = 0.0013 m
  • porosity(eps)=0.4860porosity (eps) = 0.4860
  • headlossthroughcleanbed(hL)=0.3790mheadloss through clean bed (h_L) = 0.3790 m

Find

filtration velocity (v_f), in m/s

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except v_f is given, so isolate v_f symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for v_f:

    vf=hLϕgd ϵ41.067CDLv_{f} = \sqrt{\dfrac{h_L \phi g d\,\epsilon^4}{1.067C_DL}}
  3. Step 3 — List the givens: drag coefficient (C_D) = 9.5600, filter media depth (L) = 0.7300 m, shape factor (phi) = 0.7400, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0013 m, porosity (eps) = 0.4860, headloss through clean bed (h_L) = 0.3790 m.

  4. Step 4 — Substitute the given values:

    vf=h0.73000.74009.81000.0013 ϵ41.067CD0.7300v_{f} = \sqrt{\dfrac{h_0.7300 0.7400 9.8100 0.0013\,\epsilon^4}{1.067C_D0.7300}}
  5. Step 5 — Evaluate:

    vf=0.0051 m/sv_{f} = 0.0051\ \text{m/s}
  6. Step 6 — Check: returning v_f = 0.0051 m/s to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
vf=0.0051 m/sv_{f} = 0.0051\ \text{m/s}

Why the other options are there

  • 0.0102 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0025 — dropped that same factor in the other direction.
  • 0.0056 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

Example 10
Rose Equation — solve for headloss through clean bed (case 4) — Rose Equation (10)

Rose equation headloss through a clean rapid sand filter bed Given drag coefficient (C_D) = 8.2500; filter media depth (L) = 0.8000 m; filtration velocity (v_f) = 0.0028 m/s; shape factor (phi) = 0.9400; gravitational acceleration (g) = 9.8100 m/s^2; grain diameter (d) = 0.0011 m; porosity (eps) = 0.4810, determine the headloss through clean bed (h_L) in m.

Given

  • dragcoefficient(CD)=8.2500drag coefficient (C_D) = 8.2500
  • filtermediadepth(L)=0.8000mfilter media depth (L) = 0.8000 m
  • filtrationvelocity(vf)=0.0028m/sfiltration velocity (v_f) = 0.0028 m/s
  • shapefactor(phi)=0.9400shape factor (phi) = 0.9400
  • gravitationalacceleration(g)=9.8100m/s2gravitational acceleration (g) = 9.8100 m/s^2
  • graindiameter(d)=0.0011mgrain diameter (d) = 0.0011 m
  • porosity(eps)=0.4810porosity (eps) = 0.4810

Find

headloss through clean bed (h_L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Rose Equation.
  • Everything except h_L is given, so isolate h_L symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • The Rose equation calculates head loss through a clean granular filter bed based on grain size, depth, and porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)
  2. Step 2 — Rearrange symbolically for h_L:

    hL=1.067CDLvf2ϕgd ϵ4h_{L} = \dfrac{1.067C_DLv_f^2}{\phi g d \,\epsilon^4}
  3. Step 3 — List the givens: drag coefficient (C_D) = 8.2500, filter media depth (L) = 0.8000 m, filtration velocity (v_f) = 0.0028 m/s, shape factor (phi) = 0.9400, gravitational acceleration (g) = 9.8100 m/s^2, grain diameter (d) = 0.0011 m, porosity (eps) = 0.4810.

  4. Step 4 — Substitute the given values:

    hL=1.067CDLvf20.94009.81000.0011 ϵ4h_{L} = \dfrac{1.067C_DLv_f^2}{0.9400 9.8100 0.0011 \,\epsilon^4}
  5. Step 5 — Evaluate:

    hL=0.0981 mh_{L} = 0.0981\ \text{m}
  6. Step 6 — Check: returning h_L = 0.0981 m to

    hL=1.067CDLvf2ϕgd(1ϵ4)h_L = \dfrac{1.067 C_D L v_f^2}{\phi g d} \left(\dfrac{1}{\epsilon^4}\right)

    reproduces the given quantities, and both sides carry the same units.

Answer:
hL=0.0981 mh_{L} = 0.0981\ \text{m}

Why the other options are there

  • 0.1962 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0491 — dropped that same factor in the other direction.
  • 0.1079 — rounded an intermediate value before the final step.

Reference: FE Handbook — Rose Equation (filter headloss)

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