Changes between Version 7 and Version 8 of u/erica/scratch5

Timestamp:

04/12/16 14:25:39 (9 years ago)

Author:

Erica Kaminski

Comment:

—

u/erica/scratch5

@@ -47 +47 @@
 == Run 1 == 
 
-de/dt=7.73246e+5
+de/dt=7.73246e+21
 
 I calculated the diffusion time assuming the scale-height was = box radius (which also equals the mean free path). Because of this, I thought I was in the optically thick limit everywhere in my box, so chose the flux limiter to be constant... =1/3 in the data file. From this, I calculate the diffusion time to be 24 days. Is this a good estimate?
 
+A diffusion wave is the time is take a signal to spread out over some length scale. Imagine a delta source spreading out. When its width equals its half max, is roughly a diffusion time. 
+
+Here is Erad over time:
+
+[[Image(erad_hugedetdt.gif, 50%)]] 
+
 Why do the wings leave the grid faster than the speed of light?
 
-This has to do with the fact I am not 'limiting' the diffusion through the limiter, when I should be doing that. Show plots of R. 
+This has to do with the fact I am not 'limiting' the diffusion through the limiter, when I should be doing that. Instead, I am using a constant lambda, which I thought at the time might be appropriate. However, as this plot of R shows, that is not the case:
 
-However, the scale height is not the same as the mean free path in actuality, and so it is curious then what it means to calculate a diffusion time in the FLD approximation.
+[[Image(rlimiter_hugedetdt.png, 50%)]] 
 
-If my entire box was optically thick, I would expect the t_diff=24 days. But since it is not, the wave should diffuse through some parts 
+In some regions, the limiter should be smaller than 3, so as to limit the diffusion wave in optically thin regions -- so that it is below the speed of light. Because that is not happening, I am getting superluminal signal. (This should be fixed by tracking lambda dynamically through the grid).
 
-Now knowing that my signal is propagating through my medium at an unphysical speed, 
+Here is a [[attachment: movie]] of R_limiter.
+
+And an image of the inverse scale height:
+
+[[Image(scaleheight_hugededt.png, 50%)]]
+
+
+Since, the scale height is not the same as the mean free path in actuality, getting unphysical diffusion speeds on the wings. However, given this does not represent a diffusion time, not sure it effects my prediction for a diffusion time. 
+
+Here is a movie of the temperatures over time:
+
+[[Image(temps_hugededt.gif)]] 
+
+
 
 == Run 2 ==