1. CFD Exercise 1 Laminar & turbulent flows with COMSOL

2. What is CFD?

3. What is needed to numerically solve N-S eqs?

4. Exercise 1 Calculate the velocity profile at the end of the pipe (10 cm of inner diameter and 30 m length). The property of the fluid are 1 g/mL density,1 mPa s viscosity and the average velocity is 1 cm/s. What is the Reynolds number? Is the flow laminar or turbulent? Can the geometry be simplified? Transient or steady state?

5. Questions - 1  Compare the numerical results with the analytical solution (Poiseuille profile). Is there any deviation? Why?  What is the length after that we can say that the flow is developed?  What does it happens to the numerical solution when the computational grid is coarsened or refined?

6. Setup of a simulation with COMSOL Steps to follow: 1.Model wizard (appropriate) selections 2.Parameters input 3.Construction of the geometry 4.Selection of the materials (fluid with a certain density and viscosity) 5.Setup of boundary conditions and initial conditions 6.Generation the computational grid 7.Calculation of the solution 8.Analysis of the results

7. Exercise 2 Increase the fluid velocity up to 1 m/s and calculate again the velocity profile. What is the now the Reynolds number? Do we need other models (and other initial/boundary conditions)?

8. Questions - 2  Comment the numerical results. What is the main difference with respect to the laminar case?  What is the length after that we can say that the flow is developed?  Do you find something strange in the solution?