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-rw-r--r--README.md2
-rw-r--r--channel.cc30
-rw-r--r--lid_driven_cavity.cc8
-rw-r--r--src/boundary_conditions.cc17
-rw-r--r--src/boundary_conditions.h2
-rw-r--r--src/vector.h5
6 files changed, 48 insertions, 16 deletions
diff --git a/README.md b/README.md
index 385627b..5ab879a 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@
| - | - |
| `lid_driven_cavity.cc` | Lid driven cavity using Zou/He boundary conditions for the top wall and simple bounce back for all other walls |
| `lid_driven_cavity_with_obstacles.cc` | Same as `lid_driven_cavity.cc` but includes a grid of boxes to make things more interesting |
-| `channel.cc` | Channel flow some obstacles and Dirichlet inflow |
+| `channel.cc` | Channel flow with some obstacles and Dirichlet inflow condition |
## Build
diff --git a/channel.cc b/channel.cc
index 3e7641b..b1a6166 100644
--- a/channel.cc
+++ b/channel.cc
@@ -9,8 +9,8 @@
constexpr std::size_t dimX = 500;
constexpr std::size_t dimY = 40;
-constexpr double uInflow = 0.1;
-constexpr double reynolds = 1000;
+constexpr double uInflow = 0.01;
+constexpr double reynolds = 100;
constexpr double tau = 3. * uInflow * (dimX-1) / reynolds + 0.5;
constexpr double omega = 1. / tau;
@@ -56,6 +56,10 @@ void computeLbmStep() {
computeWallCell(pop, {x, dimY-1}, { 0,-1});
}
+ for ( std::size_t y = 1; y < dimY-1; ++y ) {
+ computeMovingWallCell(pop, {0,y}, {1,0}, {uInflow,0});
+ }
+
// obstacles
for ( const auto& box : obstacles ) {
box.applyBoundary(pop);
@@ -63,16 +67,18 @@ void computeLbmStep() {
for ( std::size_t x = 0; x < dimX; ++x ) {
for ( std::size_t y = 0; y < dimY; ++y ) {
- if ( x == 0 && y > 0 && y < dimY-1 ) {
- // inflow
- fluid.density(x,y) = 1.0;
- fluid.velocity(x,y) = { uInflow, 0 };
- } else {
- Cell& cell = static_cast<Cell&>(pop.curr(x,y));
- fluid.density(x,y) = cell.sum();
- fluid.velocity(x,y) = cell.velocity(fluid.density(x,y));
+ Cell& cell = static_cast<Cell&>(pop.curr(x,y));
+
+ // bulk density
+ fluid.density(x,y) = cell.sum();
+
+ // outflow
+ if ( x == dimX-1 && y > 0 && y < dimY-1 ) {
+ fluid.density(x,y) = 1.0;
}
+ fluid.velocity(x,y) = cell.velocity(fluid.density(x,y));
+
if ( std::all_of(obstacles.cbegin(), obstacles.cend(), [x, y](const auto& o) {
return !o.isInside(x, y);
}) ) {
@@ -90,10 +96,10 @@ int main() {
std::cout << "tau: " << tau << std::endl;
std::cout << "omega: " << omega << std::endl;
- for ( std::size_t t = 0; t <= 5000; ++t ) {
+ for ( std::size_t t = 0; t <= 10000; ++t ) {
computeLbmStep();
- if ( t % 100 == 0 ) {
+ if ( t % 1000 == 0 ) {
std::cout << ".";
std::cout.flush();
fluid.writeAsVTK("result/data_t" + std::to_string(t) + ".vtk");
diff --git a/lid_driven_cavity.cc b/lid_driven_cavity.cc
index 79f330b..7a978ad 100644
--- a/lid_driven_cavity.cc
+++ b/lid_driven_cavity.cc
@@ -38,10 +38,12 @@ void computeLbmStep() {
}
}
- // straight wall cell bounce back
+ // moving top wall
for ( std::size_t x = 0; x < dimX; ++x ) {
- computeZouHeVelocityWallCell(pop, {x, dimY-1}, { 0,-1}, uLid);
+ computeMovingWallCell(pop, {x, dimY-1}, {0, -1}, {uLid, 0});
}
+
+ // straight wall cell bounce back
for ( std::size_t x = 1; x < dimX-1; ++x ) {
computeWallCell(pop, {x, 0}, { 0, 1});
}
@@ -76,7 +78,7 @@ int main() {
for ( std::size_t t = 0; t <= 10000; ++t ) {
computeLbmStep();
- if ( t % 100 == 0 ) {
+ if ( t % 1000 == 0 ) {
std::cout << ".";
std::cout.flush();
fluid.writeAsVTK("result/data_t" + std::to_string(t) + ".vtk");
diff --git a/src/boundary_conditions.cc b/src/boundary_conditions.cc
index 3488463..08b157c 100644
--- a/src/boundary_conditions.cc
+++ b/src/boundary_conditions.cc
@@ -1,5 +1,7 @@
#include "boundary_conditions.h"
+#include "lbm.h"
+
std::pair<Vector<int>, Vector<int>> neighbors(Vector<int> v) {
if ( v[0] == 0 ) {
return {
@@ -27,6 +29,21 @@ void computeWallCell(DataCellBuffer& pop, Vector<std::size_t> cell, Vector<int>
pop.curr(cell).get(neighborB) = pop.curr(cell).get(-neighborB);
}
+void computeMovingWallCell(DataCellBuffer& pop, Vector<std::size_t> cell, Vector<int> normal, Vector<double> u) {
+ const auto [neighborA, neighborB] = neighbors(normal);
+
+ const double rho = pop.curr(cell).get(-1,0) + pop.curr(cell).get(0,0) + pop.curr(cell).get(1,0)
+ + 2.*(
+ pop.curr(cell).get(-neighborA) +
+ pop.curr(cell).get(-normal ) +
+ pop.curr(cell).get(-neighborB)
+ );
+
+ pop.curr(cell).get(neighborA) = pop.curr(cell).get(-neighborA) - (6. * weight.get(-neighborA) * rho * (-neighborA * u));
+ pop.curr(cell).get(normal ) = pop.curr(cell).get(-normal ) - (6. * weight.get(-normal) * rho * (-normal * u));
+ pop.curr(cell).get(neighborB) = pop.curr(cell).get(-neighborB) - (6. * weight.get(-neighborB) * rho * (-neighborB * u));
+}
+
void computeZouHeVelocityWallCell(DataCellBuffer& pop, Vector<std::size_t> cell, Vector<int> normal, double vX) {
const auto [neighborA, neighborB] = neighbors(normal);
diff --git a/src/boundary_conditions.h b/src/boundary_conditions.h
index 6b7de19..5f528e1 100644
--- a/src/boundary_conditions.h
+++ b/src/boundary_conditions.h
@@ -5,4 +5,6 @@
void computeWallCell(DataCellBuffer& pop, Vector<std::size_t> cell, Vector<int> normal);
+void computeMovingWallCell(DataCellBuffer& pop, Vector<std::size_t> cell, Vector<int> normal, Vector<double> u);
+
void computeZouHeVelocityWallCell(DataCellBuffer& pop, Vector<std::size_t> cell, Vector<int> normal, double vX);
diff --git a/src/vector.h b/src/vector.h
index 5e105c4..839707f 100644
--- a/src/vector.h
+++ b/src/vector.h
@@ -53,6 +53,11 @@ Vector<T> operator*(T scalar, const Vector<T>& v) {
}
template <typename T, typename W>
+decltype(T{}*W{}) operator*(const Vector<T>& a, const Vector<W>& b) {
+ return a[0]*b[0] + a[1]*b[1];
+}
+
+template <typename T, typename W>
Vector<T> operator-(const Vector<T>& a, const Vector<W>& b) {
return Vector<T>{
a[0] - b[0],