1.4. Turbulence Modeling Challenges

Try these first

1. 1.

   What is the main advantage of using Large Eddy Simulation (LES) over Direct Numerical Simulation (DNS)?

   Hint

   Consider the computational demands of DNS.

2. 2.

   What does the Kolmogorov hypothesis state about small eddies?

   Hint

   Think about the characteristics of small scale turbulence.

3. 3.

   What is a significant advantage of LES compared to DNS?

   • It resolves all turbulence scales
   • It models smaller eddies
   • It requires less computational power

   Hint

   Think about the trade-offs between the two simulation techniques.

4. 4.

   True or False: The Kolmogorov hypothesis suggests that small eddies are dependent on the flow geometry.

   • True
   • False

   Hint

   Reflect on the definition of the hypothesis.

5. 5.

   Given a complex fluid system, design a hypothetical LES framework including the choice of grid size and turbulence model. Justify your selections based on the system’s characteristics.

   Hint

   Evaluate the characteristics of turbulence likely to be present in your system.

6. 6.

   Analyze the following scenario: A large eddy forms in a flowing river. Describe the process of energy transfer from this large eddy to smaller eddies, incorporating the Kolmogorov hypothesis.

   Hint

   Think about how energy moves through scales in this turbulent flow.