diff --git a/overview-burgers-forw.ipynb b/overview-burgers-forw.ipynb index 6a0e1f6..2f338fa 100644 --- a/overview-burgers-forw.ipynb +++ b/overview-burgers-forw.ipynb @@ -132,7 +132,7 @@ "source": [ "## Running the simulation\n", "\n", - "Now we're ready to run the simulation itself. To ccompute the diffusion and advection components of our model equation we can simply call the existing `diffusion` and `semi_lagrangian` operators in phiflow: `diffuse.explicit(u,...)` computes an explicit diffusion step via central differences for the term $\\nu \\nabla\\cdot \\nabla u$ of our model. Next, `advect.semi_lagrangian(f,u)` is used for a stable first-order approximation of the transport of an arbitrary field `f` by a velocity `u`. In our model we have $\\partial u / \\partial{t} + u \\nabla f$, hence we use the `semi_lagrangian` function to transport the velocity with itself in the implementation:" + "Now we're ready to run the simulation itself. To compute the diffusion and advection components of our model equation we can simply call the existing `diffusion` and `semi_lagrangian` operators in phiflow: `diffuse.explicit(u,...)` computes an explicit diffusion step via central differences for the term $\\nu \\nabla\\cdot \\nabla u$ of our model. Next, `advect.semi_lagrangian(f,u)` is used for a stable first-order approximation of the transport of an arbitrary field `f` by a velocity `u`. In our model we have $\\partial u / \\partial{t} + u \\nabla f$, hence we use the `semi_lagrangian` function to transport the velocity with itself in the implementation:" ] }, { diff --git a/overview-ns-forw.ipynb b/overview-ns-forw.ipynb index 405cefc..ca80469 100644 --- a/overview-ns-forw.ipynb +++ b/overview-ns-forw.ipynb @@ -15,7 +15,7 @@ "\\end{aligned}$$\n", "\n", "\n", - "Here, we're aiming for an incompressible flow (i.e., $\\rho = \\text{const}$), and use a simple buoyancy model (the Boussinesq approximation) via the term $(0,1)^T \\xi d$. This models changes in density without explicitly calculating $\\rho$, and we assume a gravity force that acts along the y direction via the vector $(0,1)^T$. \n", + "Here, we're aiming for an incompressible flow (i.e., $\\rho = \\text{const}$), and use a simple buoyancy model (the Boussinesq approximation) via the term $(0,1)^T \\xi d$. This approximates changes in density for incompressible solvers, without explicitly calculating $\\rho$. We assume a gravity force that acts along the y direction via the vector $(0,1)^T$. \n", "We'll solve this PDE on a closed domain with Dirichlet boundary conditions $\\mathbf{u}=0$ for the velocity, and Neumann boundaries $\\frac{\\partial p}{\\partial x}=0$ for pressure, on a domain $\\Omega$ with a physical size of $100 \\times 80$ units. \n", "[[run in colab]](https://colab.research.google.com/github/tum-pbs/pbdl-book/blob/main/overview-ns-forw.ipynb)\n", "\n" diff --git a/overview-optconv.md b/overview-optconv.md index 4731eed..4982aa8 100644 --- a/overview-optconv.md +++ b/overview-optconv.md @@ -57,7 +57,7 @@ Then we also need the _Lagrange form_, which yields an exact solution for a $\xi $$L(x+\Delta) = L + J \Delta + \frac{1}{2} H(\xi) \Delta^2$$ -In several instances we'll make use of the fundamental theorem of calculus, repeated here for completeness:  +In several instances we'll make use of the fundamental theorem of calculus, repeated here for completeness: $$f(x+\Delta) = f(x) \int_0^1 \text{d}s ~ f'(x+s \Delta) \Delta \ . $$ @@ -128,7 +128,7 @@ a parabola, and a small $H$ might overshoot in undesirable ways. The far left in To make statements about convergence, we need some fundamental assumptions: convexity and smoothness of our loss function. Then we'll focus on showing that the loss decreases, and -that we move along a sequence of smaller sets $\forall x ~ L(x)