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:: Author Message K.Haroon Site Admin Joined: 11 Dec 2005 Posts: 1318 Posted: Thu Oct 13, 2011 3:19 pm Post subject: Questions on Transonic Flight The regime of flight from the critical Mach number upto M = 1.3 is called Transonic Range. Reducing the thickness/chord ratio on a wing will reduce the transonic variations in lift and drag coefficient and delay the onset of shockwave formation. The Mach cone semi-angle decreases with increasing speed. At mach numbers below the critical Mach number 'Dutch Roll' phenomenon can happen. Dutch Roll phenomenon 'can exist' at low Mach numbers. The two areas of speed instability in transonic aircraft are below 'VDmin' and from 'M 0.89 to 0.98' As an aircraft accelerates through the transonic speed range the coefficient of drag increases then decreases.
This drag increase encountered at these high speeds is called wave drag. The drag of the airplane wing, or for that matter, any part of the airplane rises sharply, and large increases in thrust are necessary to obtain further increases in speed. This wave drag is due to the unstable formation of shock waves that transforms a considerable part of the available propulsive energy into heat, and to the induced separation of the flow from the airplane surfaces.
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Throughout the transonic range, the drag coefficient of the airplane is greater than in the supersonic range because of the erratic shock formation and general flow instabilities. Once a supersonic flow has been established, however, the flow stabilizes and the drag coefficient is reduced. Source: (Shock stall is separation of the boundary layer behind the shock wave. The Mach trim system, depending on the Mach Number, will adjust the 'Stabilizer' not the elevator trim tab. On a typical symmetrical airfoil, as the free stream Mach number approaches M 1.0 the centre of pressure will move aft to about 45% chord. On a typical transonic airfoil the transonic rearward shift of the CP occurs at about M 0.75 to M 0.98 On an example wing (Symmetrical at 2 deg alpha with MCrit at M0.75) At MFS (free stream Mach) of M0.75: - Mini shockwaves form on upper surface of wing.
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CP 20% MFS between M0.75 and M0.81: - As Mach number increases the shock waves join up and move aft. At MFS of M0.81: - A single clearly defined shockwave is formed at 70% chord. CP moves aft to 30% - Bottom flow (not so fast at 2 deg alpha) is not yet sonic.
Its just below it. At MFS of M0.89: - Top shockwave is stuck at 70% chord (high pressure behind it). Bottom shockwave is at the trailing edge. CP moves forward to 15% At MFS of M0.98: - Both shockwaves at trailing edge. CP moves back to 45% (in the transition from M0.89 to M0.98 ) At MFS of M1.4: - Bow shock attaches (MDet) - Trailing edge shocks become oblique. CP 50% To be able to predict compressibility effects you have to determine the Mach No. Transonic speed is a speed at which locally around the aeroplane both supersonic and subsonic speeds exist.
Speed of sound varies with the square root of the 'ABSOLUTE' temperature. Because the speed of sound and the TAS both increase with the square root of the absolute temperature of the air, the mach number will 'remain constant' with an increase in OAT for an aircraft flying at a constant flight level and CAS. Vmo can be exceeded in a descent at a constant mach number because Vmo is an IAS and descending at a constant mach will require an increase in TAS which will increase dynamic pressure. Just to visualize: TAS / Local Speed of Sound = Mach No e.g.
20/2 = 10 Descending means getting into warmer air i.e. Speed of sound increases. Lets say the speed of sound becomes 5 The eqauation then becomes 20/5 = 4 This is incorrect because our mach number had to be constant at 10. The equation then has to be: 50/5 = 10 Thus TAS has to increase.
Its the opposite in a climb, since we are getting into colder air where the speed of sound will be decreasing. Thus to maintain a constant mach number with decreasing speed of sound the TAS will decrease. Assuming ISA conditions, climbing at a constant Mach Number up the tropopause the TAS will 'Decrease'. In ISA conditions as you climb up 'To' the tropopause but 'Not Above' the tropopause, temperature reduces. Thus local speed of sound reduces and at constant Mach number TAS also reduces.
However above the tropopause tempearture remains constant so local speed of sound remains same and thus TAS is same at constant Mach. On a non-swept wing, when the aerofoil is accelerated from subsonic to supersonic speeds, the aerodynamic centre shifts from 25% to about 50% of the aerofoil chord. Aerodynamic Center is a sationary point only when the airflow is subsonic.
When airflow over a wing becomes supersonic, the pressure pattern over the surface will become 'Rectangular'. During acceleration from subsonic to supersonic speed the centre of pressure movement will be irregular, forward and aft, but overall rearward to 50% of the chord. Movement of the Aerodynamic Center from subsonic to supersonic is from 25 to 50% Display posts from previous: - All times are GMT Page 1 of 1 Jump to: You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum.
SubSonic Guide A Practical Guide to Installing and Configuring SubSonic by Shane R. Monroe, Monroeworld.com Welcome! This guide was designed for the casual computer and phone user; specifically using the Windows operating system and an Android-based cell phone. Others may find this guide useful, helpful or possibly entertaining. The non-install areas such as Introduction and Music Organization may be valuable to those that do not need extra help. You will be starting from scratch - installing and configuring every component from start to finish. The goal is that at the end of this guide, you are streaming your own music to your own phone with your own internet connection.
Worth noting that all references, prices, links and information were current at time of writing and will surely be subject to change without getting updated here. Good luck and have fun!
Introduction to SubSonic There are tons of ways to listen to music on your cell phone - and they fall into one of two categories: streaming or locally hosted. Streaming music comes from a server - often one you pay a monthly subscription to - like ($5/month), ($8/month), ($10/month) or, just to name a few. This is music where you have some input on the genre of music, but it isn't 'your' music.
Local music comes from your phone's memory or SD card. This is 'your' music, but you have to actually populate the phone's memory yourself - more than likely from your own massive library of music sitting on a computer at your home or work. Unless you have a very small taste in music or a really big SD card, chances are likely you're changing this music out every so often - or you find yourself wanting to hear music that isn't 'preinstalled' on your phone.
A couple of companies like, and others have tried to bridge this gap - by providing a 'cloud' music streaming where you fill the cloud with music, then you can listen to the cloud music: your music, stored in the cloud, available anywhere. Of course, there are endless limitations - like you have to constantly sync your music into the cloud, storage space is small, you cannot share music with more than one account, there are monthly fees involved, etc.
The problem is - why should I fill a cloud with music when I have all my music already stored somewhere, on hardware I already own, with a 24/7 internet connection I'm already paying around the clock for? ALL your music, streamed from your own server without restrictions or fees. The answer is SubSonic. I don't need to do a full commercial for SubSonic - if you want the brochure, check out. You're here to figure out how to get SubSonic up and running on your computer and phone. There are three parts to a successful SubSonic install: the server, the router and the phone. Setting Up The Server The first step is to actually install the SubSonic software on your computer.
It doesn't have to be the same computer your music is stored on - but it does need access to the folders your music is in. It needs a full time connection to the internet. It doesn't need to be overly powerful. Any average PC will do the trick. Remember, there are dozens of hardware and operating system configurations that you can install SubSonic on. I am only going to demonstrate one possible scenario on my own configuration. The screens and instructions may vary if you are not using the same configuration.
Install the Server. Go to and download the appropriate package for your Operating System. In my case, it was the Windows version. Run the installer. Once installed, you will see an new icon in your systray.
That's it for the install. Let's move on to configuration.
Configure the Server Configure Port. Right click the SubSonic icon in your systray.
Select SUBSONIC CONTROL PANEL. Note any message in the ERROR box. (You should be good, but if you have some other program using port 80, you may see an error here.).
Click the SETTINGS tab. You will see:. I recommend changing the port from 80 to something else - like 8080. Many internet service providers do not allow incoming port 80 connections to their customers - and you may have trouble hitting your SubSonic server from outside your network. If you saw an error message in #3 above, changing the port number is not optional. Change the port to another value, such as 8080.
If you made changes, hit SAVE SETTINGS. You will be prompted to restart SubSonic for the new changes to take effect. Click the STATUS tab, hit STOP - wait for the service to stop, then hit START.
Verify no error messages in the error box. Once SubSonic is running without errors, you're ready to move on. Set Admin Password. Right click the SubSonic icon in your systray. Select OPEN SUBSONIC IN BROWSER. The SubSonic login screen appears: NOTE: If you are using the Opera web browser, you may have trouble seeing the login screen because Opera can have issues displaying 'Try using 'instead of LOCALHOST. Enter admin in the username and password fields and click LOG IN.
A GETTING STARTED page appears. Select CHANGE ADMINISTRATOR PASSWORD. Check the box CHANGE PASSWORD. Enter your new admin password (and confirmation) in the appropriate boxes. Configure Folders. Click MUSIC FOLDERS.
If you just changed the admin password, you will be prompted to log in again. Do so with admin and your new password.
Subsonic Radio View Topic Pendragon
If you are comfortable with doing so, check the REMEMBER ME box - it will save you time later. The GETTING STARTED page should appear again. Click SET UP MUSIC FOLDERS. You will see a default music folder has been set up with the name MUSIC that points to 'c: music'. Since this is unlikely where your music is kept, change the FOLDER name to point to the actual folder your music is in.
There is no 'selector tool' to help you find the folder, so I recommend using your favorite file manager to find the folder where your music is and cut/Paste the full folder path into this box and name it appropriately:. Hit SAVE. The red message that was likely at the top of the screen, warning you about no music folders being set up should disappear. If not, go back to step 3 and try again.
Add more folders with distinct names and hit SAVE after each one. If all your music is located on this computer, you can probably skip the next steps and move on to CONFIGURE USERS.
Permissions to remote folders If you are using a UNC or MAPPED drive that points to music on another computer, you will likely run into problems getting SubSonic to see your music located there. The reason is that SubSonic is a service that runs with LOCAL MACHINE permissions - and SubSonic will not be authorized to access these file shares outside the local machine. We will configure the SubSonic service to run as an administrator - so that it will have complete access to everything you do. Note: many people will 'condemn' the use of the administrator account for this purpose because it violates 'good security practices'. Once you have SubSonic actually WORKING, then you can go back and make designated user accounts and implement all those 'good practices'. In the meantime, I'm going to get you running.
Go to START-CONTROL PANEL-SYSTEM AND SECURITY-ADMINISTRATIVE TOOLS. Run SERVICES. Locate SUBSONIC on the list:.
Double click SubSonic. SubSonic Properties will appear. Click the LOG ON tab. Select the THIS ACCOUNT radio button.
Click BROWSE. Enter in an ADMINISTRATOR level log in name (like the one you log in with) and hit CHECK NAMES. Once you have a valid username in there, click OK. Enter the username's password in the appropriate boxes and hit OK.
You should get a message that says that the username has been granted the Log On As A Service right. You will be warned that the changes won't take effect until you restart the service. Double click SubSonic on the Services list again.
Wait for the service to stop. You should receive no errors. You can close services, control panel, etc. Return to the SubSonic web screen - you should still be at MUSIC FOLDERS. Click SAVE. Any red warning messages should now clear from the top. Configure Users.
Click USERS. The Users screen will come up:. Ensure SELECT USER says '- New User -'. Set appropriate permissions for the new user using the check boxes below.
Most of them are pretty self-explanatory. If this user is going to be a CELL PHONE that is typically on 3G and not wifi - especially if your music collection is at very high bitrates - you may wish to consider setting a MAX BITRATE to something smaller like 128 or even smaller. This will help ensure your slower connection can handle streaming your music without hiccuping. You will have to install LAME to make this work. Bubble next to the MAX BITRATE field to learn more. We will not be doing this for this guide. Give them a username and password (remember to name it accordingly and keep in mind the devices that you will be entering this information on).
Click SAVE. Click the SELECT USER drop down and verify your new user is there.
Repeat to create other users. I recommend a user for each person you plan to access the SubSonic server as well as one for cell phones, tablets, etc. So you can fine tweak the performance for each user. When you are done, click HOME.
Configure Network. The GETTING STARTED page comes up. Click CONFIGURE NETWORK SETTINGS. Check the box for ACCESS YOUR SERVER OVER THE INTERNET. DO NOT CHECK THE AUTOMATIC CONFIGURATION box!. Fill in the YOURNAME box with a friendly name you would like to name your address.
I'm a big believer that 'short is better'. Click SAVE. If your name is unavailable, you will have to keep trying until you get one that is. If your computer is behind a strict FIREWALL (especially a corporate one) there is a good chance this will fail. Once you have your address, hit HOME. Note - you get 30 days to use this friendly web address without donating to the SubSonic cause. Once you do, this address is good indefinitely.
Misc Configuration. Now that we're done with the GETTING STARTED screen, click DON'T SHOW THIS AGAIN. Let's make sure SubSonic has picked up all our music, click SETTINGS. Click SEARCH. Click UPDATE SEARCH INDEX NOW. Wait a few moments at least. While you are there, be sure the Automatic Search Index settings meet your needs.
Click HOME. The left side of the screen should now fill with your music. If you still aren't seeing music, verify your settings under FOLDERS and try hitting the SAVE button on that screen.
Test the Server Locally. 1. Now that you see music, go ahead and play some. Find a song on the left. Click the PLAY button.
Verify the music plays. If you are planning on other computers on your network accessing your SubSonic server, go to those PCs and point the web browser at:. 5. The SubSonic log on page appears. Log in and verify you can play music in a similar manner to when you are on the local server. Local tests are complete! You're ready to get EXTERNAL access to your server going.
About Music Organization and Display SubSonic assumes you are controlling your music storage hierarchy. This means that the program assumes you are organizing your music via the file system, not by 'tags' embedded in the music files. The term 'album' is synonomous with 'folder'. On SubSonic's Home screen, when it says it's displaying 10 albums, it's really displaying 10 FOLDERS (which it assumes is a collection of songs on a particular album). So, if all your music is in one big folder (shame on you) and you are relying on some music player to organize and display the music in some hierarctical format, SubSonic is going to be painful for you.
SubSonic assumes that the ROOT of your music folder doesn't have music in it - but is INSTEAD filled with ARTISTS folders. Within the ARTISTS there are ALBUMS folders (which are their own folders) and within those albums are SONGS on that album. In fact, songs that are on the ROOT of your music folders will NOT show up in the Android SubSonic app for playback - despite the fact that you CAN get to them from the web interface. Make sure all your music is in a folder off the music folder you have specified.
For example, if your music folder is C: MUSIC - make sure there are no songs in that folder - only more folders: C: MUSIC BEACH BOYS - CALIFORNIA GIRLS.MP3. Will NOT show up at all in the Android app - and will appear on the BOTTOM of the music listings in the web interface.
C: MUSIC BEACH BOYS BEACH BOYS - CALIFORNIA GIRLS.MP3. Will render you the response you're probably expecting. It will show up in the Android app under BEACH BOYS and it will show up in it's own section within the web interface. Even better would be to adopt this hierarchy: C: MUSIC BEACH BOYS GREATEST HITS BEACH BOYS - CALIFORNIA GIRLS.MP3 The reason being that SubSonic will assume ALL the songs in a folder BELONG TO THE SAME ALBUM. If they don't, your cover art is going to be.
Random seeming. If you have a ton of Beach Boys in a folder from different albums, SubSonic will get the album name from one of them, throw the artwork in the folder, and EVERY song in that folder will show that cover art - right or wrong. BAD METHOD (you're asking for trouble) C: MUSIC JOURNEY - SEPARATE WAYS.MP3 C: MUSIC JOURNEY - WHEEL IN THE SKY.MP3 C: MUSIC JAMES BROWN - I FEEL GOOD.MP3 C: MUSIC JANET JACKSON - RHYTHM NATION.MP3 OK METHOD (Expect the unexpected; music will be available but cover art will be whacked) C: MUSIC J JOURNEY - SEPARATE WAYS.MP3 C: MUSIC J JOURNEY - WHEEL IN THE SKY.MP3 C: MUSIC J JAMES BROWN - I FEEL GOOD.MP3 C: MUSIC J JANET JACKSON - RHYTHM NATION.MP3 I have a couple of thse myself. Here is a look at my 'miscellaneous C' folder as seen by SubSonic: Note that SubSonic chose The Cranberries out of the blue to represent the folder/album.