Solving Bernoulli's Equation: Step-by-Step Guide

In summary, the conversation discusses a problem involving the equation dy/dx + P(x)y = Q(x)y^n, and the attempt at a solution involves finding the derivative of y in terms of x and using the reverse chain rule to solve for the integral required to solve the problem.
  • #1
domesticbark
6
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Homework Statement


[itex]
2xy'+y^3e^(-2x)=2xy
[/itex]



Homework Equations


[itex]
dy/dx + P(x)y=Q(x)y^n
[/itex]
[itex]
v=y^(1-n)
[/itex]



The Attempt at a Solution


[itex]
dy/dx-y=-y^3e^(-2x)/2x
[/itex]

[itex]
P(x)=-1
Q(x)=-e^(-2x)/2x
[/itex]

[itex]
n=3
[/itex]
[itex]
v=1/y^2
[/itex]

[itex]
dy/dx=dy/dv*dv/dx
[/itex]

[itex]
dy/dx=-1/2v^-(3/2)*dv/dx
[/itex]

[itex]
-1/2v^(-3/2)*dv/dx-v^(-1/2)=-v^(-3/2)e^(-2x)/2x
[/itex]

[itex]
dv/dx + 2v=e^(-2x)/x
[/itex]

[itex]
e^(\int P(x)\,dx)=e^(\int -1\,dx)=e^(-x)
[/itex]

[itex]
dv/dx*e^(-x)+2ve^(-x)=e^(-3x)/x
[/itex]


This is supposed to look live reverse chain rule so I get [itex] (e^(-x)*v)'=e^(-3x)/x [/itex]
but it doesn't look right and I have no idea how to do the integral required to then solve the rest of this problem.
 
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  • #2
domesticbark said:

Homework Statement


[itex]
2xy'+y^3e^(-2x)=2xy
[/itex]

Homework Equations


[itex]
dy/dx + P(x)y=Q(x)y^n
[/itex]
[itex]
v=y^(1-n)
[/itex]

The Attempt at a Solution


[itex]
dy/dx-y=-y^3e^(-2x)/2x
[/itex]

That should be ##\frac{dy}{dx}-y = -y^3e^{-2x}##
 

FAQ: Solving Bernoulli's Equation: Step-by-Step Guide

1. What is Bernoulli's equation?

Bernoulli's equation is a fundamental equation in fluid dynamics that describes the relationship between pressure, velocity, and elevation in a fluid flow. It states that the total energy of a fluid system remains constant as long as there is no external work or heat transfer.

2. Why is it important to solve Bernoulli's equation?

Solving Bernoulli's equation allows us to understand and predict the behavior of fluids in various systems, such as in pipes, nozzles, and wings of airplanes. It is also used in various engineering applications, such as in designing efficient and safe hydraulic systems.

3. What are the steps to solve Bernoulli's equation?

The steps to solve Bernoulli's equation are:

  • Identify the given parameters, such as pressure, velocity, and elevation, at two points in the fluid system.
  • Apply Bernoulli's equation, which states that the sum of the pressure, kinetic energy, and potential energy at one point in the system is equal to the sum of these energies at another point.
  • Simplify and rearrange the equation to solve for the unknown parameters, if necessary.
  • Check for consistency and accuracy of the solution by comparing it to real-world observations or using other equations or principles.

4. What are the assumptions made in Bernoulli's equation?

The assumptions made in Bernoulli's equation are:

  • Steady flow: The fluid is assumed to be flowing at a constant rate with no fluctuations.
  • Incompressibility: The density of the fluid is assumed to be constant throughout the flow.
  • No viscosity: The fluid is assumed to have no internal friction, which would cause energy losses.
  • No external work or heat transfer: There are no external forces or heat transfer acting on the fluid system.
  • Flow along a streamline: The fluid particles follow a smooth and predictable path.

5. How is Bernoulli's equation applied in real-world situations?

Bernoulli's equation is applied in many real-world situations, such as in designing pipe systems, calculating the lift force on airplane wings, and understanding blood flow in the human body. It is also used in industries like aviation, hydraulics, and plumbing to optimize the performance and efficiency of fluid systems.

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