Why doesn't the Navier-Stokes equation have a solution?

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Sawawdeh
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Why the navier-stokes equation don't have a solution ?
 
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  • #2
Sawawdeh said:
Why the navier-stokes equation don't have a solution ?
Because it’s hard enough that so far no one has figured it out. Perhaps no one ever will.

Google for “Millennium prize navier-stokes” for more about what has to be figured out.
 
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  • #3
The Navier Stokes equations do have solutions for certain specific flows.
 
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  • #4
If we don't know the solution(s), it does not mean that the equation does not have solutions, does it?
 
  • #5
Classically the word solution often refer to a closed form solution, i.e. a "simple" symbolic solution general for large set of initial conditions and parameters, and in that sense we know that there are some (turbulent) flows that cannot have such a solution even if the actual flow dynamics still satisfy the equations.
However, in context of numerical analysis (i.e. in this case computational fluid dynamics) the word solution more imply any possible solutions achievable by numerical means so here it would make sense to say that a specific turbulent flow is a solution to the equations. Since turbulent flows has sensitivity to initial conditions this usually means the numerical solution can only be an approximation that share some statistical measure with the exact solution but also that the two will eventually diverge over time.
 
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  • #6
@Sawawdeh It's never a surprise when an analytical solution to a problem doesn't exist. We start our Maths and Science education being presented with a number of situations and equations that are soluble analytically and exactly (you have to be encouraged initially) but, once you get into Integral Equations you find that most situations can only be dealt with numerically. In the recent past (pre-digital) people used vast books of tables of integrals to calculate approximate answers for problems.
Then someone discovered Chaos. . . . . .
 
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1. Why doesn't the Navier-Stokes equation have a solution?

The Navier-Stokes equations are a set of nonlinear partial differential equations that describe the motion of fluid substances. One of the main reasons why these equations do not always have a solution is due to the existence of turbulence in fluid flow. Turbulence introduces chaotic behavior and irregularities that make it difficult to find a general solution.

2. Is it possible to approximate a solution to the Navier-Stokes equation?

Yes, it is possible to approximate a solution to the Navier-Stokes equation using numerical methods. By discretizing the equations and solving them iteratively, researchers can obtain approximate solutions that provide valuable insights into fluid dynamics. However, these approximations may not always be accurate, especially in cases of highly turbulent flows.

3. Are there any simplifications or assumptions that can make the Navier-Stokes equation solvable?

Yes, there are several simplifications and assumptions that can make the Navier-Stokes equation more tractable. For example, by assuming incompressible flow, neglecting viscosity, or considering only laminar flow regimes, researchers can derive simplified versions of the equations that have analytical solutions. However, these simplifications may not capture the full complexity of real-world fluid dynamics.

4. What are some of the current challenges in solving the Navier-Stokes equation?

One of the main challenges in solving the Navier-Stokes equation is the computational complexity of the problem. The equations are highly nonlinear and require significant computational resources to solve accurately. Additionally, the presence of turbulence and chaotic behavior makes it difficult to predict fluid flow patterns with certainty, further complicating the solution process.

5. How important is it to find a solution to the Navier-Stokes equation?

Finding a solution to the Navier-Stokes equation is crucial for understanding and predicting fluid dynamics in a wide range of applications, including weather forecasting, aerodynamics, and industrial processes. While the equations may not always have a general solution, approximations and numerical methods can still provide valuable insights that help researchers improve their understanding of fluid flow phenomena.

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