Oil of relative density 0.85 issues from a 50 mm diameter orifice under a pressure of 100 kPa (gauge). The diameter of the vena contracta is 39.5 mm and the discharge is 18 L ·s'. What is the coefficient of velocity?

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
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**Problem Statement:**

Oil of relative density 0.85 issues from a 50 mm diameter orifice under a pressure of 100 kPa (gauge). The diameter of the vena contracta is 39.5 mm and the discharge is 18 L·s⁻¹. What is the coefficient of velocity?

**Solution:**

To determine the coefficient of velocity, let's explore the given data and the relevant concepts. The coefficient of velocity (\(C_v\)) is used to describe how actual velocity of a fluid jet compares to its theoretical velocity. 

**Step-by-step Calculation:**

1. **Theoretical Discharge Velocity (\(v_t\)):**

   The theoretical discharge velocity can be calculated using Torricelli’s theorem:

   \[
   v_t = \sqrt{\frac{2 \times P}{\rho}}
   \]

   where \(P = 100 \text{ kPa} = 100,000 \text{ Pa}\) and \(\rho\) is the density of oil. The oil's density can be found from the relative density:
   
   \[
   \rho = \text{relative density} \times \text{density of water} = 0.85 \times 1000 \text{ kg/m}^3 = 850 \text{ kg/m}^3
   \]

   Substituting in the values:

   \[
   v_t = \sqrt{\frac{2 \times 100,000}{850}} \text{ m/s}
   \]

2. **Actual Discharge Velocity (\(v_a\)):**

   To find the actual velocity, we use the discharge formula:

   \[
   Q = A \times v_a
   \]

   where \(Q = 18 \, \text{L/s} = 0.018 \text{ m}^3/\text{s}\), and the area \(A\) is based on the vena contracta diameter:

   \[
   A = \frac{\pi \times (39.5 \times 10^{-3})^2}{4} \, \text{m}^2
   \]

   Solving for \(v_a\):

   \[
   v_a = \frac{Q}{A}
   \]

3. **Coefficient of Velocity (\(C_v\)):**

   Using \(v_a\) and \(v_t
Transcribed Image Text:**Problem Statement:** Oil of relative density 0.85 issues from a 50 mm diameter orifice under a pressure of 100 kPa (gauge). The diameter of the vena contracta is 39.5 mm and the discharge is 18 L·s⁻¹. What is the coefficient of velocity? **Solution:** To determine the coefficient of velocity, let's explore the given data and the relevant concepts. The coefficient of velocity (\(C_v\)) is used to describe how actual velocity of a fluid jet compares to its theoretical velocity. **Step-by-step Calculation:** 1. **Theoretical Discharge Velocity (\(v_t\)):** The theoretical discharge velocity can be calculated using Torricelli’s theorem: \[ v_t = \sqrt{\frac{2 \times P}{\rho}} \] where \(P = 100 \text{ kPa} = 100,000 \text{ Pa}\) and \(\rho\) is the density of oil. The oil's density can be found from the relative density: \[ \rho = \text{relative density} \times \text{density of water} = 0.85 \times 1000 \text{ kg/m}^3 = 850 \text{ kg/m}^3 \] Substituting in the values: \[ v_t = \sqrt{\frac{2 \times 100,000}{850}} \text{ m/s} \] 2. **Actual Discharge Velocity (\(v_a\)):** To find the actual velocity, we use the discharge formula: \[ Q = A \times v_a \] where \(Q = 18 \, \text{L/s} = 0.018 \text{ m}^3/\text{s}\), and the area \(A\) is based on the vena contracta diameter: \[ A = \frac{\pi \times (39.5 \times 10^{-3})^2}{4} \, \text{m}^2 \] Solving for \(v_a\): \[ v_a = \frac{Q}{A} \] 3. **Coefficient of Velocity (\(C_v\)):** Using \(v_a\) and \(v_t
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