Check Divergence Theorem on Unit Cube

In summary, the conversation was about calculating the Divergence Theorem using a given function and unit cube. The person calculating the divergence initially got a different result than what was stated in Griffith's, but after a reminder to check the first term, they realized their mistake.
  • #1
Saladsamurai
3,020
7

Homework Statement


Check the Divergence Theorem [itex]\int_V(\nabla\cdot\bold{v})\,d\tau=\oint_S\bold{v}\cdot d\bold{a}[/itex]

using the function [itex] \bold{v}=<y^2, 2xy+z^2, 2yz> [/itex] and the unit cube below.
Photo1-1.jpg


Now when I calculate the divergence I get
[itex](\nabla\cdot\bold{v})=2y+2x+2y[/itex]

but Griffith's says that it is 2(x+y)

before I continue, I need to know what the heck I am missing?
 
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  • #2
Saladsamurai said:
Now when I calculate the divergence I get
[itex](\nabla\cdot\bold{v})=2y+2x+2y[/itex]
How did you get that? You should have [tex]\frac{\partial v_x}{\partial x} + \frac{\partial v_y}{\partial y} + \frac{\partial v_z}{\partial z}[/tex]. Check your first term [tex]\frac{\partial v_x}{\partial x}[/tex].
 
  • #3
Defennder said:
How did you get that? You should have [tex]\frac{\partial v_x}{\partial x} + \frac{\partial v_y}{\partial y} + \frac{\partial v_z}{\partial z}[/tex]. Check your first term [tex]\frac{\partial v_x}{\partial x}[/tex].

Oh man. Thanks Defennder. I am a retard :smile:
 

1. What is the Divergence Theorem and how does it relate to the Unit Cube?

The Divergence Theorem is a mathematical principle that relates the surface integral of a vector field to the volume integral of its divergence over a closed surface. In the context of the Unit Cube, the Divergence Theorem can be used to calculate the flux of a vector field through the surface of the cube by integrating the divergence of the field over the entire volume of the cube.

2. Why is the Unit Cube often used to demonstrate the Divergence Theorem?

The Unit Cube, which has sides of length 1, is a commonly used example because it has a simple and regular shape, making it easier to calculate and visualize. Additionally, the Divergence Theorem can be applied to any closed surface, and the Unit Cube is a simple example of a closed surface.

3. What is the formula for calculating the flux through the surface of a Unit Cube using the Divergence Theorem?

The formula for calculating the flux through the surface of a Unit Cube is ∫ ∧F ⋅ dS = ∩ ∧F dV, where F is the vector field, dS is the differential surface element, and dV is the differential volume element.

4. Can the Divergence Theorem be applied to other shapes besides the Unit Cube?

Yes, the Divergence Theorem can be applied to any closed surface, not just the Unit Cube. However, the calculation may be more complex for other shapes and may require using different coordinate systems or techniques.

5. What are some real-world applications of the Divergence Theorem on Unit Cube?

The Divergence Theorem has many practical applications in engineering, physics, and other fields. For example, it can be used to calculate the flow of fluids through a pipe, the distribution of electric charge in a region, or the movement of heat in a solid object. In these cases, the Unit Cube can represent a small part of a larger system, and the Divergence Theorem can be used to analyze and solve for the behavior of the entire system.

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