[ex-fluidsystem][propertiesheader] Update README.md

exercises/exercise-fluidsystem/README.md

@@ -19,8 +19,10 @@ Locate all the files you will need for this exercise
 * The shared __main file__ : `main.cc`
 * The __input file__ for part a: `aparams.input`
 * The __problem file__ for part a: `2pproblem.hh`
+* The __properties file__ for part a: `2pproperties.hh`
 * The __input file__ for part b: `bparams.input`
 * The __problem file__ for part b: `2p2cproblem.hh`
+* The __properties file__ for part b: `2p2cproperties.hh`
 * The __spatial parameters file__: `spatialparams.hh`
 
 Furthermore you will find the following folders:
@@ -32,7 +34,7 @@ To see more components, fluidsystems and binarycoefficients implementations, hav
 
 ### 2. Implement a new component
 
-In the following, the basic steps required to set the desired fluid system are outlined. Here, this is done in the __problem file__, i.e. for this part of the exercise the code shown below is taken from the `2pproblem.hh` file.
+In the following, the basic steps required to set the desired fluid system are outlined. Here, this is done in the __properties file__, i.e. for this part of the exercise the codes shown below is taken from the `2pproperties.hh` file.
 
 In this part of the exercise we will consider a system consisting of two immiscible phases. Therefore, the _TypeTag_ for this problem (`ExerciseFluidsystemTwoP`) derives from
 the `TwoP` _TypeTag_ (immiscible two-phase model properties) and the `BoxModel` _TypeTag_ (specifies properties of the discretization scheme).
@@ -61,7 +63,7 @@ while the `BoxModel` _TypeTag_ can be found in the `discretization/box.hh` heade
 
 For a cell-centered scheme, you could derive from `CCTpfaModel` or `CCMpfaModel` instead (and, of course, include the right headers).
 
-As one of the two phases we want to use water and we want to precompute tables on which the properties are then interpolated in order to save computational time. Thus, in a first step we have to include the following headers:
+As one of the two phases we want to use water and we want to precompute tables on which the properties are then interpolated in order to save computational time. Since we need this part in both problem file and properties file, we have to include the following two headers in our problem file, i.e. `2pproblem.hh` file, and the properties file has access to them through problem file.
 
 ```c++
 // The water component
@@ -162,7 +164,7 @@ We now want to implement a pressure-dependent density for our component. Open th
 
 $`\displaystyle \rho_{MyComp} = \rho_{min} + \frac{ \rho_{max} - \rho_{min} }{ 1 + \rho_{min}*e^{-1.0*k*(\rho_{max} - \rho_{min})*p} } `$
 
-where $`p`$ is the pressure and $`\rho_{min} = 1440 `$, $`\rho_{max} = 1480 `$ and $`k = 5 \cdot 10^{-7} `$. Also, make sure the header is included in the `2pproblem.hh` file by uncommenting the corresponding line. Furthermore, the new component has to be set as a liquid phase in the fluid system. To do so, search for `TODO: dumux-course-task 2.2`. Comment out the corresponding line and uncomment the other. The density distribution of this phase (rhoN) at the final simulation time should look like this:
+where $`p`$ is the pressure and $`\rho_{min} = 1440 `$, $`\rho_{max} = 1480 `$ and $`k = 5 \cdot 10^{-7} `$. Also, make sure the header is included in the `2pproperties.hh` file by uncommenting the corresponding line. Furthermore, the new component has to be set as a liquid phase in the fluid system. To do so, search for `TODO: dumux-course-task 2.2`. Comment out the corresponding line and uncomment the other. The density distribution of this phase (rhoN) at the final simulation time should look like this:
 
 ![](../extradoc/exercise-fluidsystem_a_solution2.png)
 
@@ -173,8 +175,9 @@ Compare the gnuplot output to the following plot of the density function from ab
 
 ### 3. Implement a new fluid system
 
-The problem file for this part of the exercise is `2p2cproblem.hh`. We now want to implement a new fluid system consisting of two liquid phases, which are water and the previously implemented compressible component. We will consider compositional effects, which is why we now have to derive our _TypeTag_ (`ExerciseFluidsystemTwoPTwoC`) from a _TypeTag_ (`TwoPTwoC`) that holds the miscible two-phase
-two-component model properties:
+The problem file and properties file for this part of the exercise are `2p2cproblem.hh` and `2p2cproperties.hh`, respectively. 
+We now want to implement a new fluid system consisting of two liquid phases,which are water and the previously implemented compressible component. We will consider compositional effects, which is why we now have to derive our _TypeTag_ (`ExerciseFluidsystemTwoPTwoC`) from a _TypeTag_ (`TwoPTwoC`) that holds the miscible two-phase
+    two-component model properties:
 
 ```c++
 // The numerical model