# How to solve PDE that also contain Time Delay DDE terms?

**URL:** <https://discourse.julialang.org/t/how-to-solve-pde-that-also-contain-time-delay-dde-terms/93452>\
**Category:** New to Julia\
**Tags:** question\
**Created:** [January 24, 2023, 10:28am UTC](https://discourse.julialang.org/t/how-to-solve-pde-that-also-contain-time-delay-dde-terms/93452 "2023-01-24T10:28:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Hassan\_Alam](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/hassan_alam/32/46169_2.png) [@Hassan\_Alam](https://discourse.julialang.org/u/Hassan_Alam)\
**Post date:** [January 24, 2023, 10:28am UTC](https://discourse.julialang.org/t/how-to-solve-pde-that-also-contain-time-delay-dde-terms/93452/1 "2023-01-24T10:28:07Z")

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Hello, I am trying to solve a system of partial differential equations that also contains a time delay part. For DDE, people usually use “DDEProblem” and for PDE people use “ODEProblem”. But, when I am trying to solve my two PDE coupled equations by using finite-differences scheme, then I am facing problmes. If I am using DDEProblem to solve it, then solution is become unstable. If I am trying to use ODEProblem, then it is not allowing me to use h(p,t) history function and error is coming that it is not compatible with ODEProblem. What should I do?

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**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [January 25, 2023, 2:46am UTC](https://discourse.julialang.org/t/how-to-solve-pde-that-also-contain-time-delay-dde-terms/93452/2 "2023-01-25T02:46:43Z")

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> [@Hassan\_Alam](#):
>
> Hello, I am trying to solve a system of partial differential equations that also contains a time delay part. For DDE, people usually use “DDEProblem” and for PDE people use “ODEProblem”.

PDE people use whatever the discretization gives. For your case, it should give a DDEProblem.

> [@Hassan\_Alam](#):
>
> If I am using DDEProblem to solve it, then solution is become unstable.

What’s your discretization like? Is it a stable discretization? Are you using an implicit method? Etc. There’s little information here.