 Okay, there is a folder on your desktop, contains two folders, the first one is the assignment that's the problem statements, the second one is the Sylab codes, so I'll go to the Sylab codes first, lab one is today's lab session, within lab one you have two Sylab files, the first one is the explicit FTCS solver, the second one is the implicit solver, just click on the first file, okay, so this similar restore last session windows pop up again and again whenever you open Sylab, so you may just cancel it, so the source code opens up, here you can see like the first problem has been hardcoded, the values of all the properties have been hardcoded here, and simply press this icon here, that's the execute icon, and once you press that at the bottom you'll find the console window, so just go to the console window, so here you'll find that the properties that had been hardcoded show up on the screen, and then as the problem statement states that we need to run the problem at three different pressure gradients, so I've made a selection menu that says for the first when you enter one year it will select db by dx equal to zero, when you press enter two over here it will select db by dx equal to twenty thousand, and when you enter three over here it will select db by dx equal to minus thirty thousand, so say I go with the first option and I enter one year, so in this case it will take a pressure gradient of zero and generate the output, so the output window pops up, so it's dynamically plotting like you can see on the console, it has been shown that output is plotted at different time steps, the same correspond to the legend over here, so the marks correspond to the analytical solution, the marked graph, whereas the continuous lines are the numerical solution. Let me just say one thing here, okay so when you saw that the program was actually plotting the output, if you look at it carefully it first plotted six continuous lines, six yeah, and then it plotted on top of those six lines, six set of symbols, so the continuous lines are actually the numerical output at the various times as I have been mentioned in the legend, and the marks correspond to actually that series solution for the same time levels which are now superimposed, so the point here is that you can see that the analytical solution and the numerical solution for a simple problem such as this really match each other quite well, just keep that in mind that the marks correspond to the analytical solution, the series solution and the continuous lines which come first before the mark show up, they are the numerical solution. So as you can see here very quickly before he shows how to take this output and put it in that world file, you can see that at the last time level which is t of 1.08, you see that the velocity profile has become more or less straight as what we would expect when the time goes to a very large value, because this is a dp dx equal to 0 situation, so there is no imposed pressure gradient, the way it started was initially the velocity here is 40, at the top plate the velocity at the bottom plate is 0, and then as time progresses it simply the velocity profile simply develops into more and more of a linear profile, eventually it will become linear, if you let the code run for more time than say 1.08 as has been the last time step, if you let it run for say 20 or whatever then you will see that it has become a straight line. So the idea now is that for all these lab sessions such outputs will be generated by placing those or choosing those options, so for example here what you chose was the option was dp dx equal to 0 corresponded to that prompt of 1, similarly you can do for prompt of 2 and 3 and so on, and every time such an output will be generated, the idea is that you can take this output and copy it from here and paste it in that word document where a place has been provided, so that you have some sort of a homework file for yourself which you can utilize for later purpose, I think is that the idea, so now he will demonstrate how you can take this output from the Sylab window and paste it in that word. To save it as a image file simply go to file export to and then from the bottom you can drop down when you can select bitmap file right at the top here and just rename it and so it will by default get stored in lab 1, the folder lab 1. Lab 1, yeah fine, alright why don't we just look at that some other value of dp dx just for completeness, so to rerun the code again go to the source code and we will again press this execute icon here and if you go back to the console window, the code has started again, say this time I select the option 3 that's dp dx of minus 30,000. Bitmap option is not available, the very first one I think, Windows BMP as it says, okay now you see in this case this was a dp dx of minus 30,000 which means that it's an assisting pressure gradient, so what it turns out is as we had sketched earlier when we were talking the analytical solution, the final time profile as you can see it's a fuller time profile for the purple line and that is precisely how we had sketched also the solution for an assisting pressure gradient and that is precisely how it is coming. And then here the continuous lines are the code output that is the numerical solution and the marks are the analytical solution. Let us run one more of that adverse pressure gradient, so you go back to source code, press execute, go to the Sylab console 2, so in this case you can see that there is actually some sort of a reverse flow type situation on the bottom side because there is a adverse pressure gradient and then it reaches the boundary condition of u equal to 40 at the top as is expected. So this was all done using the FTCS which is the explicit method, exact same thing you can do with the implicit solution.