# UpwindOperator from DiffEqOperators.jl

**URL:** <https://discourse.julialang.org/t/upwindoperator-from-diffeqoperators-jl/21053>\
**Category:** Numerics\
**Tags:** question, diffeq\
**Created:** [February 21, 2019, 4:01pm UTC](https://discourse.julialang.org/t/upwindoperator-from-diffeqoperators-jl/21053 "2019-02-21T16:01:49Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![boutor2](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/boutor2/32/27869_2.png) [@boutor2](https://discourse.julialang.org/u/boutor2)\
**Post date:** [February 21, 2019, 4:01pm UTC](https://discourse.julialang.org/t/upwindoperator-from-diffeqoperators-jl/21053/1 "2019-02-21T16:01:49Z")

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I have been playing around with` DifferentialEquations.jl`, mainly for solving reaction diffusion PDE’s. I now wish to add an advection term to my model. For this purpose I discovered DiffEqOperators.jl. `UpwindOperator` sounds like the class I am looking for. However, I can not figure out what is the `directions` argument, that should be a `BitArray`.

@ChrisRackauckas could you enlighten me? 😁

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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:** [February 21, 2019, 4:59pm UTC](https://discourse.julialang.org/t/upwindoperator-from-diffeqoperators-jl/21053/2 "2019-02-21T16:59:55Z")

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It needs work before this is automatic and the BCs are fixed. Sorry!

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**Author:** ![boutor2](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/boutor2/32/27869_2.png) [@boutor2](https://discourse.julialang.org/u/boutor2)\
**Post date:** [February 22, 2019, 8:38am UTC](https://discourse.julialang.org/t/upwindoperator-from-diffeqoperators-jl/21053/3 "2019-02-22T08:38:36Z")

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Alright, I will do my small cuisine then ! Thanks 🙂