6. Manufactured Solution Mathematical Forms¶
(Note: All solution variables are in SI units.)
The baseline manufactured solution selected for the verification study is a combination of sine and cosine functions and takes the following general form [25], [1]
where, \(L\) is a characteristic length (herein, selected equal to the domain length or \(L = 1\)), and \(\phi = \left\lbrack P_{g},u_{g},v_{g},w_{g},u_{s},v_{s},w_{s},T_{g},T_{s} \right\rbrack^{T}\) represents the set of primitive variables being tested for order of accuracy. The sinusoidal functions (\(f_{\text{ϕx}}\), \(f_{\text{ϕy}}\), etc.) selected are shown in Table 6.1
Variable, \(ϕ\) |
\(f_{ϕx}\) |
\(f_{ϕy}\) |
\(f_{ϕz}\) |
\(f_{ϕxy}\) |
\(f_{ϕyz}\) |
\(f_{ϕzx}\) |
---|---|---|---|---|---|---|
\(u_{g}\) |
sin |
cos |
cos |
cos |
sin |
cos |
\(v_{g}\) |
sin |
cos |
cos |
cos |
sin |
cos |
\(w_{g}\) |
cos |
sin |
cos |
sin |
sin |
cos |
\(u_{s}\) |
sin |
cos |
cos |
cos |
sin |
cos |
\(v_{s}\) |
sin |
cos |
cos |
cos |
sin |
cos |
\(w_{s}\) |
cos |
sin |
cos |
sin |
sin |
cos |
\(P_{g}\) |
cos |
cos |
sin |
cos |
sin |
cos |
\(T_{g}\) |
cos |
cos |
sin |
cos |
sin |
cos |
\(T_{s}\) |
cos |
cos |
sin |
cos |
sin |
cos |
\(\varepsilon_{s}\) |
cos |
cos |
sin |
– |
– |
– |
The frequency constants (\(a_{\phi x}\), \(a_{\phi y}\), \(a_{\phi xy}\), etc.) and the amplitude constants (\(\phi_{0}\), \(\phi_{x}\), \(\phi_{\text{xy}}\), etc.) are selected to ensure functions that are smooth but show reasonable periodicity and magnitude within the domain. The frequency constants selected are shown in Table 6.2.
Variable, \(ϕ\) |
\(a_{ϕx}\) |
\(a_{ϕy}\) |
\(a_{ϕz}\) |
\(a_{ϕxy}\) |
\(a_{ϕyz}\) |
\(a_{ϕzx}\) |
---|---|---|---|---|---|---|
\(u_{g}\) |
0.5 |
0.85 |
0.4 |
0.6 |
0.8 |
0.9 |
\(v_{g}\) |
0.8 |
0.8 |
0.5 |
0.9 |
0.4 |
0.6 |
\(w_{g}\) |
0.85 |
0.9 |
0.5 |
0.4 |
0.8 |
0.75 |
\(u_{s}\) |
0.5 |
0.85 |
0.4 |
0.6 |
0.8 |
0.9 |
\(v_{s}\) |
0.8 |
0.8 |
0.5 |
0.9 |
0.4 |
0.6 |
\(w_{s}\) |
0.85 |
0.9 |
0.5 |
0.4 |
0.8 |
0.75 |
\(P_{g}\) |
0.4 |
0.45 |
0.85 |
0.75 |
0.7 |
0.8 |
\(T_{g}\) |
0.75 |
1.25 |
0.8 |
0.65 |
0.5 |
0.6 |
\(T_{s}\) |
0.5 |
0.9 |
0.8 |
0.5 |
0.65 |
0.4 |
\(\varepsilon_{s}\) |
0.4 |
0.5 |
0.5 |
– |
– |
– |
The amplitude constants selected are shown Table 6.3.
Variable, \(ϕ\) |
\(ϕ_{0}\) |
\(ϕ_{x}\) |
\(ϕ_{y}\) |
\(ϕ_{z}\) |
\(ϕ_{xy}\) |
\(ϕ_{yz}\) |
\(ϕ_{zx}\) |
---|---|---|---|---|---|---|---|
\(u_{g}\) |
7 |
3 |
-4 |
-3 |
2 |
1.5 |
2 |
\(v_{g}\) |
9 |
-5 |
4 |
5 |
-3 |
2.5 |
3.5 |
\(w_{g}\) |
8 |
-4 |
3.5 |
4.2 |
-2.2 |
2.1 |
2.5 |
\(u_{s}\) |
7 |
3 |
-4 |
-3 |
2 |
1.5 |
2 |
\(v_{s}\) |
9 |
-5 |
4 |
5 |
-3 |
2.5 |
3.5 |
\(w_{s}\) |
8 |
-4 |
3.5 |
4.2 |
-2.2 |
2.1 |
2.5 |
\(P_{g}\) |
100 |
20 |
-50 |
20 |
-25 |
-10 |
10 |
\(T_{g}\) |
350 |
10 |
-30 |
20 |
-12 |
10 |
8 |
\(T_{s}\) |
300 |
15 |
-20 |
15 |
-10 |
12 |
10 |
\(\varepsilon_{s}\) |
0.3 |
0.06 |
0.1 |
0.06 |
– |
– |
– |
The baseline manufactured solutions presented above are used to generate manufactured solutions for the two-phase flow test cases. As an example, the manufactured solution for the test case presented in Section 2.6 is provided next.
The manufactured solutions for the scalar variables (\(P_{g}\), \(T_{g}\), and \(T_{s}\)) are simply obtained from Eq.6.1 and by substituting the appropriate functions and constants described above. For example, for the pressure variable (\(P_{g}\)), this function is as follow:
The manufactured solutions for velocity components of the gas phase are obtained by taking the curl of the baseline velocity vector field, i.e.,
where, for example, \(\phi\left( u_{g} \right)\) is the baseline manufactured solution obtained from Eq.6.1, the functions, and the constants described above for the variable \(u_{g}\). This results in a divergence free velocity field because \(\nabla \cdot (\nabla \times \overrightarrow{H})\) is identically zero for any vector field, \(\overrightarrow{H}\). Thus, the manufactured solution for \(u_{g}\) is given as:
Similarly, the manufactured solution for \(v_{g}\) and \(w_{g}\) can be derived.
Finally, the manufactured solution for velocity components of the solids phase is selected as simply the following divergence free field:
Manufactured solutions for other MMS test cases presented are derived using the baseline manufactured solutions and appropriate constraints (divergence free field, boundary conditions, etc.). For a complete look at the MMS function and MMS source terms, please see the MMS_MOD.f file under the respective test case of the MFIX distribution.