Water Flow 9170E7
1. **Problem Statement:** Calculate the theoretical volumetric flow rate and time to empty a water tank using given parameters in an Automated Water Management System (AWMS).
2. **Given Data and Assumptions:**
- Tank volume $V_{\text{tank}} = 1000$ L $= 1$ m$^3$
- Pipe diameter $d = 0.0127$ m
- Water head $h = 1$ m
- Gravitational acceleration $g = 9.8$ m/s$^2$
- Discharge coefficient $C_d = 0.6014$
- Velocity coefficient $C_v = 0.97$
3. **Step 1: Calculate Water Velocity at Tank Outlet**
Using Torricelli's law with velocity coefficient:
$$V_{wp} = C_v \sqrt{2gh}$$
Substitute values:
$$V_{wp} = 0.97 \times \sqrt{2 \times 9.8 \times 1} = 0.97 \times \sqrt{19.6} \approx 0.97 \times 4.427 = 4.294 \text{ m/s}$$
4. **Step 2: Calculate Cross-Sectional Area of Pipe**
$$A = \pi \left( \frac{d}{2} \right)^2 = \pi \times (0.00635)^2 = \pi \times 4.032 \times 10^{-5} \approx 1.267 \times 10^{-4} \text{ m}^2$$
5. **Step 3: Calculate Volumetric Flow Rate**
Using discharge coefficient:
$$Q = C_d \times A \times \sqrt{2gh}$$
Calculate $\sqrt{2gh}$:
$$\sqrt{2 \times 9.8 \times 1} = 4.427$$
Then:
$$Q = 0.6014 \times 1.267 \times 10^{-4} \times 4.427 \approx 3.374 \times 10^{-4} \text{ m}^3/\text{s}$$
Convert to liters per second:
$$Q = 3.374 \times 10^{-4} \times 1000 = 0.3374 \text{ L/s}$$
Convert to cubic meters per hour:
$$Q_w = Q \times 3600 = 3.374 \times 10^{-4} \times 3600 = 1.2146 \text{ m}^3/\text{h}$$
6. **Step 4: Calculate Time to Empty the Tank**
$$t = \frac{V_{\text{tank}}}{Q} = \frac{1}{3.374 \times 10^{-4}} \approx 2964 \text{ s}$$
Convert to minutes:
$$t = \frac{2964}{60} \approx 49.4 \text{ minutes}$$
7. **Step 5: General Flow Rate Expression**
$$Q = C_d \left( \frac{\pi d^2}{4} \right) \sqrt{2gh}$$
This formula provides the baseline flow rate under normal conditions.
8. **Leakage Detection Criterion:**
If the measured flow rate $Q_{\text{measured}}$ exceeds $110\%$ of the expected discharge $Q_{\text{threshold}}$ for a sustained time (e.g., 5-10 seconds), an alert for abnormal water flow is triggered.
**Final answers:**
- Volumetric flow rate $Q \approx 3.374 \times 10^{-4}$ m$^3$/s or 0.3374 L/s
- Time to empty tank $t \approx 2964$ s or 49.4 minutes