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Archive for September, 2011

XFOIL Study Notes (3)

September 29th, 2011 No comments

Workflow

The typical workflow of airfoil analysis using XFOIL is: Run XFOIL -> Load Airfoil Shape (using LOAD command or NACA command) -> Run Analysis (using OPER command) -> Plot results (using PPLO command).

Categories: Engineering Tags:

XFOIL Study Notes (2)

September 29th, 2011 No comments

Units

Most XFOIL operations are performed on the airfoil’s cartesian coordinates x,y, which do not necessarily have a unit chord c. Since the chord is ambiguous for odd shapes, the XFOIL force coefficients C_L, C_D, C_M are obtained by normalizing the forces and moment with only the freestream dynamic pressure (the reference chord is assumed to by unity). Likewise, the XFOIL Reynolds number RE is defined with the freestream velocity and viscosity, and an implied unit chord:

Force Coefficients in XFOIL

The conventional definitions are:

Conventional Force Coefficients

It can be seen that the conventional and XFOIL definitions differ only by the chord factor c or c^2.

Categories: Engineering Tags:

XFOIL Study Notes (1)

September 29th, 2011 No comments

Buffer Airfoil and Current Airfoil

XFOIL uses the concept of a “current airfoil” and “buffer airfoil”. These are the airfoils on which various calculations are performed, and they are distinct from the “polar” x,y coordinates. The “polar” x,y are simply archived data, and do not directly participate in computation. The “polar” x,y must first be transferred into the current airfoil if they are to be used for computation.

Some notes on buffer airfoil and current airfoil:

  • When the buffer airfoil coordinates are read from a file during startup, or read in via the LOAD command, they are by default also copied directly into the current airfoil.
  • The NACA command automatically invokes the paneling routine to create a current airfoil with a suitable paneling.
  • In some cases it is desirable to explicitly re-copy the buffer airfoil into the current airfoil via the PCOP command.
  • If the normalization flag is set (toggled with the NORM command), the buffer airfoil coordinates will be normalized to unit chord and the leading edge will be placed at the origin.
  • The GDES facility allows very extensive manipulation of the buffer airfoil.
Categories: Engineering Tags:

电子书下载网站

September 20th, 2011 No comments

找英文书到这里:http://library.nu/。记得要登录后搜索,不登录的话有很多书搜不出来。

Categories: Uncategorized Tags:

Use the On-Board SATA Port on Pogoplug Pro

September 14th, 2011 11 comments

There is an internal SATA port on Pogoplug Pro. You can connect an eSATA external hard drive to this SATA port. But before doing so, you need an SATA to eSATA cable and make some modifications to the Pogoplug Pro’s covers. Here is how:

  1. Take the Pogoplug Pro apart. Grab the transparent housing using one hand and the front cover (the stand) using the other hand and use some force to jig them apart. Then cut a small slot on the front cover (the stand) between the front USB port and the LED light cover.
    Pogoplug SATA Mod
  2. You can see the red SATA port on the PCB board.
    Pogoplug SATA Mod
  3. On the top cover you need to cut two slots into the ribs to make room for the SATA to eSATA cable.
    Pogoplug SATA Mod
  4. Connect the SATA to eSATA cable to the on-board SATA port. Remember to pass the cable through the front cover slot (the one that we cut in the previous step) first.
    Pogoplug SATA Mod
  5. Replace the top cover, the transparent housing, and the front cover (the stand). Make sure they close tight and slug. Now you can connect your eSATA external hard drive to the Pogoplug Pro.
    Pogoplug SATA Mod
Categories: Tips and Tricks Tags:

Fix Gmail Manager 0.6.4.1

September 11th, 2011 1 comment

If you encountered login problems with Gmail Manager 0.6.4.1 recently, here is the fix that I found on the Internet.

Problems logging in? Here’s the fix!
by divrsit on September 8, 2011 #

EDIT: With regards to the Portable Apps version, if you access the troubleshooting page in FF via Help > Troubleshooting Information or by typing in about:support in the address bar it will allow you to see the location of your profile directory and also the name/location of the Gmail Manager extension. (This works for any version of FF, portable or not). I’m running the latest version of FF via the Portable Apps site and can verify this fix works.

First of all, this is a truly great app! I know it’s frustrating when it suddenly stops working (with no dev support), but thanks to the scripting gods I was able to find a fix over at the Webmail Notifier add-on review page. Credit for the new url’s goes to Sirhc; I just made the modifications to meet Gmail Manager script.

1. Browse yourself to C:\Users\YOUR USER NAME\AppData\Roaming\Mozilla\Firefox\Profiles\A RANDOM CODE IS HERE.default\extensions\

2. Locate the file {582195F5-92E7-40a0-A127-DB71295901D7}.xpi and use WinRaR/WinZip ect. to extract the files

3. Open the components folder, look for the file gmServiceGmail.js and use a text editor to modify the file

4. Look for these 2 lines:

this._loginURL = “https://www.google.com/accounts/ServiceLoginAuth”;
should be changed to this
this._loginURL = “https://accounts.google.com/accounts/ServiceLoginAuth?service=mail”;

this._loginURL = “https://www.google.com/a/” + this.domain + “/LoginAction2”;
should be changed to this
this._loginURL = “https://accounts.google.com/a/”+ar[1]+”/LoginAction2?service=mail”;

5. Save the file, overwrite the existing gmServiceGmail.js with this one and VIOLA! After restarting Firefox you should be all set.

Additional Fix
by Xander on September 9, 2011 #

The fix Divrsit posted earlier was not enough to get it to work again for me. I had to make 1 more adjustment. Thanks for Divrsit for posting the solution.
This works for Windows 7. If you use a different version of Windows, the files mentioned below are most likely on different locations.
1. Browse to C:\Users\YOUR USER NAME\AppData\Roaming\Mozilla\Firefox\Profiles\A RANDOM CODE IS HERE.default\extensions\
2. Locate the file {582195F5-92E7-40a0-A127-DB71295901D7}.xpi, rename it to {582195F5-92E7-40a0-A127-DB71295901D7}.zip and extract the files to a temporary location.
3. Open the components folder, look for the file gmServiceGmail.js and use a text editor to modify these 2 lines:
this._loginURL = “https://www.google.com/accounts/ServiceLoginAuth”;
should be changed to this
this._loginURL = “https://accounts.google.com/accounts/ServiceLoginAuth?service=mail”;

this._loginURL = “https://www.google.com/a/” + this.domain + “/LoginAction2”;
should be changed to this
this._loginURL = “https://accounts.google.com/a/”+ar[1]+”/LoginAction2?service=mail”;
4. Save the file, overwrite the existing gmServiceGmail.js
5. Open the file install.rdf with a text editor and change the line:
4.0.*
to
6.0.*
6. Save the file, overwrite the existing install.rdf.
7. Rezip all files you extracted in step 2 and name it {582195F5-92E7-40a0-A127-DB71295901D7}.xpi
8. Replace the old {582195F5-92E7-40a0-A127-DB71295901D7}.xpi for the 1 you just adjusted and restart FireFox

Categories: Tips and Tricks Tags: