# Asking about the jump definition for Darcy Flow problem in Freefem

**URL:** https://community.freefem.org/t/asking-about-the-jump-definition-for-darcy-flow-problem-in-freefem/3986
**Category:** General Discussion
**Created:** [June 26, 2025, 3:13pm UTC](https://community.freefem.org/t/asking-about-the-jump-definition-for-darcy-flow-problem-in-freefem/3986 "2025-06-26T15:13:25Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![NhuLe](https://avatars.discourse-cdn.com/v4/letter/n/278dde/32.png) [@NhuLe](https://community.freefem.org/u/NhuLe)
#### Post date: [June 26, 2025, 3:13pm UTC](https://community.freefem.org/t/asking-about-the-jump-definition-for-darcy-flow-problem-in-freefem/3986/1 "2025-06-26T15:13:25Z")

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Dear all experts, I’m a beginner in Freefem. I tried to write the Freefem code for the eq.(28) in the paper " Mixed Discontinuous Galerkin methods for Darcy flow. F. Brezzi, T.J.R. Hughes, L.D. Marini and A. Masud" (2005):

> **[Mixed Discontinuous Galerkin Methods for Darcy Flow - Journal of Scientific...](https://link.springer.com/article/10.1007/s10915-004-4150-8)**
>
> We consider a family of mixed finite element discretizations of the Darcy flow equations using totally discontinuous elements (both for the pressure and the flux variable). Instead of using a jump stabilization as it is usually done for discontinuos...

which is,

 ![image](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/8/80a8e891447e8582f2a42be1704f02f80eff217a.png)

I did the code but the result is not good.In the paper, the jump for vector valued function is defined as follows:

 ![image](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/e/e6b99d9e87575f3470d68d561a848ba96eed60ba.png)

So I am not sure about the macro jump definition for the vector valued function I wrote in my freefem code is correct based on the jump definition.

> macro jumpV(vec1, vec2) (jump(vec1)\*N.x + jump(vec2)\*N.y) //  
> I tried to fix but it does’t seem to work. Looking forwards to any ideas.  
> Here is my code for the eq.(28)  
> [DarcyFlow.edp](https://community.freefem.org/uploads/short-url/janz1TAHoubX5VlTQP5EokEsrTB.edp) (5.7 KB)  
> Thanks in advance.