fixed typo in domain sizes

overview-ns-forw.ipynb

@@ -57,7 +57,7 @@
    "source": [
     "## Setting up the simulation\n",
     "\n",
-    "The following code sets up a few constants, which are denoted by upper case names. We'll use $40\\times32$ cells to discretize our domain, introduce a slight viscosity via $\\nu$, and define the time step to be $\\Delta t=1.5$. \n",
+    "The following code sets up a few constants, which are denoted by upper case names. We'll use $40 \\times 32$ cells to discretize our domain, introduce a slight viscosity via $\\nu$, and define the time step to be $\\Delta t=1.5$. \n",
     "\n",
     "We're creating a first `CenteredGrid` here, which is initialized by a `Sphere` geometry object. This will represent the inflow region `INFLOW` where hot smoke is generated."
    ],
@@ -82,9 +82,9 @@
   {
    "cell_type": "markdown",
    "source": [
-    "The inflow will be used to inject smoke into a second centered grid `smoke` that represents the marker field $d$ from above. Note that we've defined a `Box` of size $100 \times 80$ above. This is the physical scale in terms of spatial units in our simulation, i.e., a velocity of magnitude $1$ will move the smoke density by 1 unit per 1 time unit, which may be larger or smaller than a cell in the discretized grid, depending on the settings for `x,y`. You could parametrize your simulation grid to directly resemble real-world units, or keep appropriate conversion factors in mind. \n",
+    "The inflow will be used to inject smoke into a second centered grid `smoke` that represents the marker field $d$ from above. Note that we've defined a `Box` of size $100 \\times 80$ above. This is the physical scale in terms of spatial units in our simulation, i.e., a velocity of magnitude $1$ will move the smoke density by 1 unit per 1 time unit, which may be larger or smaller than a cell in the discretized grid, depending on the settings for `x,y`. You could parametrize your simulation grid to directly resemble real-world units, or keep appropriate conversion factors in mind. \n",
     "\n",
-    "The inflow sphere above is already using the \"world\" coordinates: it is located at $x=30$ along the first axis, and $y=15$ (within the $100 \times 80$ domain box).\n",
+    "The inflow sphere above is already using the \"world\" coordinates: it is located at $x=30$ along the first axis, and $y=15$ (within the $100 \\times 80$ domain box).\n",
     "\n",
     "Next, we create grids for the quantities we want to simulate. For this example, we require a velocity field and a smoke density field."
    ],