2D axisymmetric and 3D CFD simulations of flow over the benchmark DARPA SUBOFF submarine model

Now, of course, any CFD study will not become valid unless and until you do a grid sensitivity analysis or a grid independent study. So we have also done a grid sensitivity analysis of grid independent study using the Richardson Extrapolation. This Richardson Extrapolation is based on REFERENCES 10 and 11 and has now become a mandatory criteria when publishing research work in many peer-reviewed journals. As reference nine has cited, this has become a very mandatory criteria. That's why, if you take any research articles related to CFD on external four cases in APR reviewed article, you can see that this Chang and extrapolation has been explained there.

In our articles, we have explained in detail this research and extrapolation. The reason why this Richardson Extrapolation is connected is that from the grid sin analysis, we are selecting the fine mesh. The case where the Bible process is less than one is obtained, that is the finest mesh. But you should also be aware of what the uncertainty is associated with your fine mesh and how far you are deviating from the ideal mesh. Ideal mesh means when your cell size is zero, then using that cell, the results that you're getting is called ideal CFT value. So such a kind of measure is called ideal mission.

There are a set of equations used in the Richardson Extrapolation to find out what is the Grid Convergence Index and Order offs. These are the two important parameters which are the end results of research and extrapolation. The equations used for calculating these parameters are explained in reference 10, 9, and 11.

Now 12.3 represents the fine medium and Cores much respectively. We have selected three different representative sizes for these grid sensitivity analyses. In my case, I'm focusing on the drag value, but drag is also dependent on the wall sea stress as well as the pressure distribution. These pressure and water cells stress are actually flow variables, velocity distribution is also considered. So these flow variables are the primary variables which are greatly affected by small changes in the cell sizes.

We have selected a near wall layer, Celtic S as the representative size since by experience, we have seen that when you change the thickness of the water ad layer thickness, there are drastic changes that are obtained in the research. We have selected three different sizes in the case of 2D axis symmetric and 3D. Then we have, for each case, calculated what is the number of Prism Layers and kept the growth rate constant.

Finally, we are actually calculating the relative error between the fine and medium mesh. So that is 770.35% in the case of 2D axis symmetric, whereas it is 1.2% in the case of 3D. The Grid Convergence Index is the parameter which indicates how far you are deviating from the fine mesh or what is the uncertainty that is associated with the fine mesh.

Now we are coming into the research section verification and validation. So this is something which confuses everyone verification and validation. Are they both the same or are they both different? So what April This REFERENCES? 10 is very important P J Roa. He has actually given a beautiful definition for this verification and validation. Verification means you are solving the equations in the right manner, but as validation means you are solving the right equation.