# Boundary values with entropy filter **URL:** \ **Category:** Cases\ **Tags:** config\ **Created:** [8 March 2024 10:22 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050 "2024-03-08T10:22:40Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![wgbb](https://avatars.discourse-cdn.com/v4/letter/w/6f9a4e/32.png) [@wgbb](https://pyfr.discourse.group/u/wgbb)\ **Post date:** [8 March 2024 10:22 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050/1 "2024-03-08T10:22:40Z")
Hello everyone, I tried using` solver entropy filter` to calculate supersonic flow with shock waves, but strange physical peak values appeared at the inlet boundary. ![image](https://global.discourse-cdn.com/free1/uploads/pyfr/original/1X/d1d36fc748fceaada4f9cbf88c836eb098136c6f.png) I used `type = sup-in-fa` and `type = char-riem-inv` methods, but none of them were solved. Is it a grid problem? Good wishes. ---
**Author:** ![WillT](https://avatars.discourse-cdn.com/v4/letter/w/bc79bd/32.png) [@WillT](https://pyfr.discourse.group/u/WillT)\ **Post date:** [8 March 2024 15:28 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050/2 "2024-03-08T15:28:40Z")
How big are these ‘peak’ values relative to the background? ---
**Author:** ![wgbb](https://avatars.discourse-cdn.com/v4/letter/w/6f9a4e/32.png) [@wgbb](https://pyfr.discourse.group/u/wgbb)\ **Post date:** [10 March 2024 10:35 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050/3 "2024-03-10T10:35:08Z")
Compared to the environmental background, its magnitude is not very large, about twice that of the background, because the background uses a flow value of 1.0 ![image](https://global.discourse-cdn.com/free1/uploads/pyfr/original/1X/fb7aac6c9d174bcd17a51801de46185682ba253b.png) Good wishes. ---
**Author:** ![WillT](https://avatars.discourse-cdn.com/v4/letter/w/bc79bd/32.png) [@WillT](https://pyfr.discourse.group/u/WillT)\ **Post date:** [12 March 2024 09:34 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050/4 "2024-03-12T09:34:36Z")
What is the initial condition, and what is the condition that you are applying at this boundary? ---
**Author:** ![wgbb](https://avatars.discourse-cdn.com/v4/letter/w/6f9a4e/32.png) [@wgbb](https://pyfr.discourse.group/u/wgbb)\ **Post date:** [13 March 2024 08:58 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050/5 "2024-03-13T08:58:47Z")
Sorry for my negligence, it should be due to an issue with the initial values. Thank you for your reminder. Also, I don’t quite understand the meaning of these three variables. How should the minimum values of p and rho be adjusted? Also, etol. Thank you for your suggestion. I am very confused about this. Does adjusting their values have any impact on capturing shock waves? ---
**Author:** ![fdw](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@fdw](https://pyfr.discourse.group/u/fdw)\ **Post date:** [13 March 2024 13:18 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050/6 "2024-03-13T13:18:21Z")
Can you show the full configuration file for your case? Regards, Freddie. ---
**Author:** ![wgbb](https://avatars.discourse-cdn.com/v4/letter/w/6f9a4e/32.png) [@wgbb](https://pyfr.discourse.group/u/wgbb)\ **Post date:** [19 March 2024 11:25 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050/7 "2024-03-19T11:25:44Z")
Thank you for your attention, I understand that my problem is due to an unscientific setting of the initial value, I set the initial value u=0.0, and as time advances the strange spikes near the inlet will be eliminated, but a larger problem has been found, which can be described in detail as seen in one of the new threads I’ve started, thank you for your time. Regards, Wgbb. ---
**Author:** ![wgbb](https://avatars.discourse-cdn.com/v4/letter/w/6f9a4e/32.png) [@wgbb](https://pyfr.discourse.group/u/wgbb)\ **Post date:** [19 March 2024 11:32 UTC](https://pyfr.discourse.group/t/boundary-values-with-entropy-filter/1050/8 "2024-03-19T11:32:25Z")
> [@About initial values and exit boundaries](https://pyfr.discourse.group/t/about-initial-values-and-exit-boundaries/1067): > > Hello everyone. I have a question related to initial values and exit boundaries to ask for advice. I’m trying to calculate a supersonic flat plate flow with squares. First of all I used the free coming flow values to initialize the whole field, but it quickly reported an error dispersion, I also tried several initial conditions to try to set the initial velocity near the leading and trailing edges of the square a little bit smoother, but it still reported an error, I found that setting the in…