From fddd75dd5b9d4baffacf397500f3c32583cfe3d6 Mon Sep 17 00:00:00 2001
From: Tristan Montoya <montoya.tristan@gmail.com>
Date: Sat, 30 Sep 2023 00:00:15 -0400
Subject: [PATCH] add kelvin-helmholtz

---
 src/ConservationLaws/ConservationLaws.jl   |  2 +-
 src/ConservationLaws/euler_navierstokes.jl | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/ConservationLaws/ConservationLaws.jl b/src/ConservationLaws/ConservationLaws.jl
index eef35381..8d7d2d05 100644
--- a/src/ConservationLaws/ConservationLaws.jl
+++ b/src/ConservationLaws/ConservationLaws.jl
@@ -147,7 +147,7 @@ module ConservationLaws
     export InviscidBurgersEquation, ViscousBurgersEquation
     include("burgers.jl")
 
-    export EulerEquations, NavierStokesEquations, EulerPeriodicTest, TaylorGreenVortex, IsentropicVortex, TrixiIsentropicVortex
+    export EulerEquations, NavierStokesEquations, EulerPeriodicTest, TaylorGreenVortex, IsentropicVortex, KelvinHelmholtzInstability
     include("euler_navierstokes.jl")
 
 end
\ No newline at end of file
diff --git a/src/ConservationLaws/euler_navierstokes.jl b/src/ConservationLaws/euler_navierstokes.jl
index 8e7cc046..17a7d16d 100644
--- a/src/ConservationLaws/euler_navierstokes.jl
+++ b/src/ConservationLaws/euler_navierstokes.jl
@@ -302,4 +302,22 @@ end
     v = -cos(x[1])*sin(x[2])*cos(x[3])
 
     return SVector{5}(1.0, u, v, 0.0,  p/(f.γ-1.0) + 0.5*ρ*(u^2 + v^2))
+end
+
+struct KelvinHelmholtzInstability <: AbstractGridFunction{2}
+    γ::Float64
+    N_c::Int
+    function KelvinHelmholtzInstability(conservation_law::EulerEquations{2})
+        return new(conservation_law.γ,4)
+end
+
+@inline function evaluate(f::KelvinHelmholtzInstability, 
+    x::NTuple{2,Float64}, t::Float64=0.0)
+    (x₁,x₂) = (x - 1, y - 1)
+    B = tanh(15*x₂ + 7.5) - tanh(15*x₂ - 7.5)
+    ρ = 0.5 + 0.75*B
+    p = 1.0
+    u = 0.5*(B-1) 
+    v = 0.1*sin(2π*x₁)
+    return SVector{4}(ρ,ρ*u,ρ*v,p/(f.γ-1) + 0.5*ρ*(u^2 + v^2))
 end
\ No newline at end of file