Reel and Paddle
Environmental Engineering · FE Reference Handbook section
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.
reel and paddle flocculator power dissipation calculation Given drag coefficient of paddle (C_D) = 1.9100; fluid density (rho) = 995.0 kg/m^3; paddle area (A) = 3.9000 m^2; paddle velocity relative to water (v_p) = 0.3400 m/s, determine the power dissipated (P) in W.
Given
Find
power dissipated (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except P is given, so isolate P 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.9100, fluid density (rho) = 995.0 kg/m^3, paddle area (A) = 3.9000 m^2, paddle velocity relative to water (v_p) = 0.3400 m/s.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 145.7 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 291.3 — kept a factor of two that cancels in the correct rearrangement.
- 72.8279 — dropped that same factor in the other direction.
- 160.2 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle mixer design for flocculation basin Given drag coefficient of paddle (C_D) = 1.3200; fluid density (rho) = 996.5 kg/m^3; paddle velocity relative to water (v_p) = 0.5200 m/s; power dissipated (P) = 3,069 W, determine the paddle area (A) in m^2.
Given
Find
paddle area (A), in m^2
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except A is given, so isolate A 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for A:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.3200, fluid density (rho) = 996.5 kg/m^3, paddle velocity relative to water (v_p) = 0.5200 m/s, power dissipated (P) = 3,069 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
A = 33.1868\ \text{m^2}Step 6 — Check: returning A = 33.1868 m^2 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 66.3736 — kept a factor of two that cancels in the correct rearrangement.
- 16.5934 — dropped that same factor in the other direction.
- 36.5055 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle drag power for a slow-mix flocculator Given drag coefficient of paddle (C_D) = 1.0700; fluid density (rho) = 995.5 kg/m^3; paddle area (A) = 6.4500 m^2; power dissipated (P) = 4,893 W, determine the paddle velocity relative to water (v_p) in m/s.
Given
Find
paddle velocity relative to water (v_p), in m/s
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except v_p is given, so isolate v_p 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for v_p:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.0700, fluid density (rho) = 995.5 kg/m^3, paddle area (A) = 6.4500 m^2, power dissipated (P) = 4,893 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning v_p = 1.1251 m/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2.2503 — kept a factor of two that cancels in the correct rearrangement.
- 0.5626 — dropped that same factor in the other direction.
- 1.2377 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle flocculator power dissipation calculation Given drag coefficient of paddle (C_D) = 1.4700; fluid density (rho) = 995.0 kg/m^3; paddle area (A) = 1.7000 m^2; paddle velocity relative to water (v_p) = 0.2000 m/s, determine the power dissipated (P) in W.
Given
Find
power dissipated (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except P is given, so isolate P 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.4700, fluid density (rho) = 995.0 kg/m^3, paddle area (A) = 1.7000 m^2, paddle velocity relative to water (v_p) = 0.2000 m/s.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 9.9460 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 19.8920 — kept a factor of two that cancels in the correct rearrangement.
- 4.9730 — dropped that same factor in the other direction.
- 10.9406 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle mixer design for flocculation basin Given drag coefficient of paddle (C_D) = 1.2000; fluid density (rho) = 996.0 kg/m^3; paddle velocity relative to water (v_p) = 0.4400 m/s; power dissipated (P) = 1,915 W, determine the paddle area (A) in m^2.
Given
Find
paddle area (A), in m^2
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except A is given, so isolate A 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for A:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.2000, fluid density (rho) = 996.0 kg/m^3, paddle velocity relative to water (v_p) = 0.4400 m/s, power dissipated (P) = 1,915 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
A = 37.6184\ \text{m^2}Step 6 — Check: returning A = 37.6184 m^2 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 75.2368 — kept a factor of two that cancels in the correct rearrangement.
- 18.8092 — dropped that same factor in the other direction.
- 41.3802 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle drag power for a slow-mix flocculator Given drag coefficient of paddle (C_D) = 1.9900; fluid density (rho) = 998.0 kg/m^3; paddle area (A) = 4.0500 m^2; power dissipated (P) = 1,199 W, determine the paddle velocity relative to water (v_p) in m/s.
Given
Find
paddle velocity relative to water (v_p), in m/s
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except v_p is given, so isolate v_p 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for v_p:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.9900, fluid density (rho) = 998.0 kg/m^3, paddle area (A) = 4.0500 m^2, power dissipated (P) = 1,199 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning v_p = 0.6680 m/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.3361 — kept a factor of two that cancels in the correct rearrangement.
- 0.3340 — dropped that same factor in the other direction.
- 0.7348 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle flocculator power dissipation calculation Given drag coefficient of paddle (C_D) = 1.8600; fluid density (rho) = 998.5 kg/m^3; paddle area (A) = 3.0000 m^2; paddle velocity relative to water (v_p) = 0.2500 m/s, determine the power dissipated (P) in W.
Given
Find
power dissipated (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except P is given, so isolate P 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.8600, fluid density (rho) = 998.5 kg/m^3, paddle area (A) = 3.0000 m^2, paddle velocity relative to water (v_p) = 0.2500 m/s.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 43.5284 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 87.0567 — kept a factor of two that cancels in the correct rearrangement.
- 21.7642 — dropped that same factor in the other direction.
- 47.8812 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle mixer design for flocculation basin Given drag coefficient of paddle (C_D) = 1.8400; fluid density (rho) = 994.5 kg/m^3; paddle velocity relative to water (v_p) = 0.8100 m/s; power dissipated (P) = 1,679 W, determine the paddle area (A) in m^2.
Given
Find
paddle area (A), in m^2
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except A is given, so isolate A 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for A:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.8400, fluid density (rho) = 994.5 kg/m^3, paddle velocity relative to water (v_p) = 0.8100 m/s, power dissipated (P) = 1,679 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
A = 3.4531\ \text{m^2}Step 6 — Check: returning A = 3.4531 m^2 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 6.9061 — kept a factor of two that cancels in the correct rearrangement.
- 1.7265 — dropped that same factor in the other direction.
- 3.7984 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle drag power for a slow-mix flocculator Given drag coefficient of paddle (C_D) = 1.0500; fluid density (rho) = 998.0 kg/m^3; paddle area (A) = 0.9000 m^2; power dissipated (P) = 4,091 W, determine the paddle velocity relative to water (v_p) in m/s.
Given
Find
paddle velocity relative to water (v_p), in m/s
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except v_p is given, so isolate v_p 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for v_p:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.0500, fluid density (rho) = 998.0 kg/m^3, paddle area (A) = 0.9000 m^2, power dissipated (P) = 4,091 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning v_p = 2.0548 m/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 4.1096 — kept a factor of two that cancels in the correct rearrangement.
- 1.0274 — dropped that same factor in the other direction.
- 2.2603 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator
reel and paddle flocculator power dissipation calculation Given drag coefficient of paddle (C_D) = 1.7700; fluid density (rho) = 992.5 kg/m^3; paddle area (A) = 6.0000 m^2; paddle velocity relative to water (v_p) = 0.4500 m/s, determine the power dissipated (P) in W.
Given
Find
power dissipated (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Reel and Paddle.
- Everything except P is given, so isolate P 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.
- Reel and paddle flocculators dissipate power in proportion to paddle drag, area, and relative velocity through the water.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: drag coefficient of paddle (C_D) = 1.7700, fluid density (rho) = 992.5 kg/m^3, paddle area (A) = 6.0000 m^2, paddle velocity relative to water (v_p) = 0.4500 m/s.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 480.2 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 960.5 — kept a factor of two that cancels in the correct rearrangement.
- 240.1 — dropped that same factor in the other direction.
- 528.3 — rounded an intermediate value before the final step.
Reference: FE Handbook — Reel and Paddle Flocculator