HW 3 AAE 334 Assignment PDF

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HW 3 Assignment...

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Problem(Set(3( AAE#334#Fall#2017# Assigned:#Friday,#September#8,#2017# Due:#Friday,#September#15,#2017# # 1. [5#pts]#Starting#from#the#definition#of#the#moment#about#the#leading#edge:# . $ !"# = −'( )(

*+, * -* # /

and#the#series#solution#for#the#circulation#density:# , 0 = 2)(

1 + cos 0 + 2/ sin 0

(

2: sin ;0

#

:?,"# = − 2/ + 2= − 2 2 . Recall#that#our#standard#change#of#variables#is#* = 1 − cos 0 .# B # 2. [10#pts]#Consider#a#two-dimensional#airfoil#with#the#following#camber#line:# DF D DB C D =E F − G+1 +G + # B > > > H = Here#G #and#E #are#constants.#Remember#to#use#the#transformation# = (1 − cos 0).## B .

# (a)#Find#-C/-D #in#terms#of#cos 0.#It#should#have#the#form#LB cos B 0 + L= cos 0 + L/ ,# where#L/ ,#L= ,#and#LB #are#constants.# (b)#Find#the#coefficients#A0,#A1,#and#A2# (c)#Compute#the#lift#coefficient#>M # (d)#Compute#the#moment#coefficient#about#the#quarter#chord#>?,./N # (e)#Find#the#value#of#the#constant#B#that#gives#zero#moment#about#the#quarter#chord# # 3. [2.5#pts]#Why#does#a#good#airfoil#have#a#blunt#leading#edge,#and#a#sharp#trailing#edge?# What#problems#would#occur#if#you#flew#with#a#reversed#airfoil?#(Hint:#think#about#the# behavior#of#a#flat#plate#at#angle-of-attack.)# # 4. [2.5#pts]#Carry#out#the#computer#exercise#detailed#on#the#next#page,#and#attach#a# screenshot#of#your#terminal#window#to#your#homework.#

AAE 334 Homework 3 First Computer Assignment Assigned: Friday, September 8, 2017 Due: Friday, September 15, 2017 Introduction This is a very simple lesson to get you started using the Purdue Scholar computer cluster. You will log in, open a terminal window, and run a few commands. Most of you will find this to be a trivial exercise; come to office hours if you get stuck. In the coming weeks, we will generate grids, run a Computational Fluid Dynamics (CFD) code, and visualize the results. The Scholar cluster is a virtual computer cluster, which allows classes to use the unused time on the research cluster Rice. If you are not familiar with the idea of a computer cluster, think of a lot of stripped-down personal computers (called nodes) connected by a very fast network (here, a system called Infiniband). Each of the nodes on Scholar has twenty cores, so you can potentially run twenty programs at once on a node, or run one program with twenty components. CFD software, like the SU2 code, can utilize many nodes at once, with thousands of computational tasks executing at once. The operating system on Scholar is a form of GNU/Linux, which is currently the most commonly-used operating system for computer clusters. Systems like this are meant for large computations (batch jobs), not interactive use. The usual CFD work pattern is to generate grids and visualize results on your personal workstation using interactive point-and-click programs, but to run jobs and compile programs using a text-based terminal. We’ll practice using the terminal program in this homework. You can find more details about Scholar here: https://www.rcac.purdue.edu/compute/scholar/ In particular, have a look at the “User Guide” link on the left side of the page. For a tutorial on Linux commands, try searching for something like “Introduction to Basic Linux Commands” on YouTube. Logging In The simplest way to connect to Scholar is through Thinlinc. Go to the following website and log in with your Purdue Career account information: https://thinlinc.rcac.purdue.edu:300/main/ A black desktop should appear. If you have trouble, try a different web browser, such as Firefox. Under the “Applications Menu”, select “Terminal Emulator” to bring up a terminal window. Click on the window to obtain input focus, and type the following in the window: ssh -Y [email protected] But wait! Change “jpoggie” to your own username before you try this. Enter your password when prompted. (If you are stuck here, see again the bit about using your own username.) You may get a message about whether you are sure you want to continue connecting; type “yes” and hit return. Using the Terminal At the new command prompt, type:

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uname -a You should see that you are on the Scholar cluster which runs Linux. Another good command on Linux is: lscpu Give that a try. You should see that a node consists of two sockets, each having ten cores, for a total of twenty cores per node. You can also see that the cores run at a clock speed of 2.6 GHz, and see that there are three levels of cache memory (very fast memory for temporarily holding data). These parameters can a big impact on how fast your CFD batch job will run. If you are a true Linux enthusiast, you can look up what “BogoMIPS” means. If you want to know more about any of these commands, you can use the online manual. To find out about “lscpu”, type: man lscpu Hit the spacebar to page down, and type “q” to quit. There is even a manual page for “man”; try typing “man man”. As on Windows or macOS, Linux files are organized into directories or folders. To see which directory you’re currently in on the terminal, type: pwd This means print working directory. To see the files there, type: ls You may not have any files yet. Let’s create one. Type the following: echo This is some arbitrary text. > file1.txt Type “ls” again; you should see the new file. Now type: cat file1.txt You should see the contents of the file. When you get chance, look up “cd”, for change directory. Using a Simple Text Editor Now we’ll use a simple text editor to do something useful. The default behavior of the following Linux commands is to permanently delete or overwrite files without warning: rm (remove file), mv (move or rename file), ln (link or alias file), and cp (copy file). By default, there is no “trash” like on macOS. Let’s change the default behavior to ask before obliterating. I’ll give the instructions for “vi”, but you may like the graphical editor “gedit” better. Type: vi .bashrc

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(Note that the filename “.bashrc” begins with a period or dot.) If the screen is empty, that’s fine. If there’s text, use the arrow keys to move to the bottom of the file. Type “o” to go into insert mode, and type or paste the following text into your file: alias rm='rm -i' alias mv='mv -i' alias ln='ln -i' alias cp='cp -i' Hit “Esc” to get out of insert mode, then type “:wq” to quit the program. If you run into trouble, hit “Esc” and “:q!” to get out without saving. Try looking at your file with “cat .bashrc”, “more .bashrc”, or “gedit .bashrc”. Now type on separate lines, type the following in the terminal: alias source .bashrc alias You should see a change. The commands are now a bit safer. Last Things To prove that you actually did this yourself, type the following on separate lines: fortune date whoami The output of “fortune” may or may not be funny. Now I would like you to capture an image of the window you’re working in. To find the required tool on macOS, look up “take pictures of the screen” in the Finder help menu. On Linux Gnome desktop select the pulldown menu “Applications > Accessories > Take Screenshot”, and on Ubuntu Linux press the keys “Alt” and “PrtScn” together. On Windows, select the Start button, and type “snipping tool” in the search box. To get out of Scholar, type “exit” in the terminal window. To get out of the terminal, type “exit” again or click the “X” at the top of the terminal. Now log out of the workstation using the menubar at the top of the screen. It’s very important that you get in the habit of logging out when done, or locking the screen when you step away from the computer. Computer security is an extremely serious matter in industry and government. Next week we’ll start doing CFD.

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