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Author: pcarruscag

_vandv/index.md

@@ -27,3 +27,5 @@ Code-to-code comparisons of drag and skin friction on a turbulent flat plate is
 Code-to-code comparisons for a bump in a channel, which results in pressure gradients, is presented using data from the NASA Turbulence Modeling Resource.
 * [Three-Element High-Lift Subsonic Airfoil](/vandv/30p30n/)
 Results for the 30p30n airfoil, mesh independence study at low angle-of-attack, and determination of maximum lift, both comparing different numerical schemes.
+* [Shock-Wave Boundary-Layer Interaction](/vandv/swbli/)
+Comparison of grid-converged results with experimental data. SA and SST turbulence models.

_vandv/swbli.md

@@ -7,7 +7,7 @@ permalink: /vandv/swbli/
 | --- | --- | --- |
 | `RANS` | 7.4.0 | P. Gomes |
 
-The details of the Mach 5 SWBLI validation case are taken from [NASA](https://www.grc.nasa.gov/www/wind/valid/m5swbli/m5swbli.html).
+The details of the Mach 5 SWBLI validation case are taken from the [NPARC Alliance Validation Archive](https://www.grc.nasa.gov/www/wind/valid/m5swbli/m5swbli.html).
 
 <p align="center">
 <img src="/vandv_files/swbli/mach.png" alt="Mach number contours (SST-2003m)" />
@@ -18,77 +18,33 @@ We validate our implementation of the SA and SST models by comparing the SU2 num
 
 ## Problem Setup
 
-The geometry and flow conditions are according to the [main reference](https://www.grc.nasa.gov/www/wind/valid/m5swbli/m5swbli.html).
+The main geometry features and flow conditions are according to the [main reference](https://www.grc.nasa.gov/www/wind/valid/m5swbli/m5swbli.html). In this study, the inlet was extended 10mm to avoid the intersection of the supersonic inlet with a no-slip wall (that extension is modelled with a slip wall).
 The SU2 configuration files used in this study are [available here](https://github.com/su2code/SU2/blob/develop/TestCases/vandv/rans/swbli/).
+These are applicable to all grid levels, however note that simulations on finer grids were restarted from the results on the previous (coarser) level.
 Mean flow convective fluxes were computed with Roe's scheme and a limited MUSCL reconstruction (Green-Gauss gradients and Venkatakrishnan's limiter).
 The SA-neg and SST-2003m turbulence models were used with first order advection.
 SU2 was run with "freestream equal Mach" non-dimensionalization for all configurations.
 
 ## Mesh Description
 
 Quad-dominant meshes of increasing density were used to perform a grid convergence study.
-The meshes were generated using GMSH by defining a refinement factor for all sizes and counts.
+The meshes were generated using GMSH where a refinement factor was applied for all sizes and counts.
 Particular attention was given to the y+ on the bottom plate (smaller than 1 on the coarsest level), the main shock, and the separation region.
 The GMSH script can be downloaded from the [SU2 V&V GitHub repository](https://github.com/su2code/VandV/tree/master/rans/swbli).
-The mesh designations and approximate sizes are: 
+The mesh designations and approximate sizes are:
 
 - L1 "coarse" (2 x "fine") - 37k quadrilaterals
 - L2 "medium" (1.41 x "fine") - 76k quadrilaterals
 - L3 "fine" - 146k quadrilaterals
 
 ## Results
 
-Given the focus of this validation case (interaction between a shock and a boundary layer) it is of particular interest to analyze how well CFD predicts the 
+Given the focus of this validation case (interaction between a shock wave and a boundary layer) it is of particular interest to analyze how well CFD predicts the skin friction coefficient on the bottom plate and the separation (caused by the shock wave) and re-attachment locations.
+Figure 2 compares the skin friction coefficient for the two turbulence models and three mesh levels used, with the experimental values.
 
-### Grid convergence
-
-The main configuration studied here is the Roe scheme, with MUSCL reconstruction using Green-Gauss gradients, and limited using the van Albada edge-based limiter.
-The only possible tunning parameter of this configuration is the entropy fix coefficient, which was fixed at 1e-5.
-We compare this configuration with the JST scheme on three grid levels (with 2nd and 4th order coefficient values of 0.5 and 0.01, respectively).
-For completeness, we also test the effect of the limiter on the "fine" level by using the Venkatakrishnan limiter with coefficient 0.05.
-
-We observe second order convergence of the lift and drag coefficients, and good agreement between Roe + van Albada, JST, [FaSTAR results](https://jaxa.repo.nii.ac.jp/?action=pages_view_main&active_action=repository_view_main_item_detail&item_id=2921&item_no=1&page_id=13&block_id=21), and [Cflow results](https://jaxa.repo.nii.ac.jp/?action=pages_view_main&active_action=repository_view_main_item_detail&item_id=2923&item_no=1&page_id=13&block_id=21).
-The Roe + Venkatakrishnan configuration predicts lower values, which were observed to be sensitive to the limiter coefficient. For example lowering it to 0.025 increases drag to the level obtained with the other two configurations.
-
-<p align="left">
-<img src="/vandv_files/30p30n/drag.png" alt="Drag coefficient at 5.5deg AoA" />
-</p>
-**Figure 2** - Drag coefficient at 5.5deg AoA.
-
-<p align="left">
-<img src="/vandv_files/30p30n/lift.png" alt="Lift coefficient at 5.5deg AoA" />
-</p>
-**Figure 3** - Lift coefficient at 5.5deg AoA.
-
-### Maximum lift
-
-Roe + van Albada and JST agree well on the maximum lift, and again match the results of other codes.
-However JST predicts the flow to remain attached at significantly higher angle-of-attack than expected.
-
-<p align="left">
-<img src="/vandv_files/30p30n/max_lift.png" alt="Lift coefficient on the fine grid level" />
-</p>
-**Figure 4** - Lift coefficient on the fine grid level.
-
-<p align="left">
-<img src="/vandv_files/30p30n/max_drag.png" alt="Drag coefficient on the fine grid level" />
-</p>
-**Figure 5** - Drag coefficient on the fine grid level.
-
-### Discussion
-
-The pressure coefficient distributions at 5.5 degrees AoA computed by Roe + van Albada and JST are nearly identical.
-However, JST predicts significantly higher skin friction coefficient (Cf) on the suction side which explains the higher angle-of-attack required for leading-edge separation to occur.
-Away from this critical point the lift and drag characteristics are dominated by the pressure distribution and thus the two schemes agree well.
-The only significant differences in Cf between the van Albada and Venkatakrishnan limiters are at the trailing-edges.
-
-<p align="left">
-<img src="/vandv_files/30p30n/cp.png" alt="Pressure coefficient distribution at 5.5deg AoA on fine grid level" />
-</p>
-**Figure 6** - Pressure coefficient distribution at 5.5deg AoA on fine grid level.
-
-<p align="left">
-<img src="/vandv_files/30p30n/cf.png" alt="Skin friction coefficient distribution at 5.5deg AoA on fine grid level" />
+<p align="center">
+<img src="/vandv_files/swbli/cf.png" alt="Comparison of skin friction coefficient." />
 </p>
-**Figure 7** - Skin friction coefficient distribution at 5.5deg AoA on fine grid level.
+**Figure 2** - Comparison of skin friction coefficient.
 
+The results do not change significantly between meshes L2 and L3, they were also not sensitive to other perturbations such as refining the mesh around the main shock, or global refinement (i.e. L4).