Skip to content

Add V&V for the 2D Backward facing step #2463

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 4 commits into
base: master
Choose a base branch
from
Open
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
Binary file not shown.
Binary file not shown.
52 changes: 52 additions & 0 deletions TestCases/vandv/inc_bfs/docs/su2validation_inc_bfs.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,52 @@
---
title: 2D Backward Facing Step Validation Case
permalink: /docs/su2validation_inc_bfs.md
---

# 2D Backward Facing Step Validation Case


<style>
table th:first-of-type {
width: 50%;
}
table th:nth-of-type(2) {
width: 30%;
}
</style>

| Solver | Version |
| --- | --- |
| INC_RANS | 8.1.0 "Harrier" |

---

The 2D Backward-Facing Step (BFS) is a classical benchmark case for validating turbulence models. In this configuration, a fully developed turbulent boundary layer encounters a sudden back step, leading to flow separation and recirculation zones downstream. The experimental data provided by Driver and Seegmiller serves as the reference for this validation case.

## Problem Setup

Geometry: The BFS model consists of a channel with a sudden expansion due to a step. The step height (H) is the primary geometric parameter and in this case it is set to $0.0127m$. This corresponds to a Reynolds number of approximately 36,000 based on step height H. Geometry of the testcase is shown in the following image.

![geometry](../images/bfsw-geom.png)

The simulation is performed with the following boundary conditions:

- Inlet: A specified velocity profile representing the turbulent boundary layer.
- Walls: No-slip conditions on both the upper and lower walls.
- Outlet: pressure outlet condition.

## Mesh Description

To ensure accurate resolution of the flow features, particularly in the recirculation region downstream of the step, a sequence of structured nested grids is used. These grids are designed to effectively capture adverse pressure gradients and flow separation. The approximate mesh sizes are:

- L1 "coarse" - 20k quadrilaterals
- L2 "medium" - 104k quadrilaterals
- L3 "fine" - 210k quadrilaterals

## Results

The SST turbulence model demonstrates excellent agreement with experimental results for velocity and turbulent kinetic energy. However, the pressure coefficient appears to be slightly under-predicted, as seen in the comparison figures below.

![Velocity](../images/Velocity.png)
![tke](../images/tke.png)
![Cp](../images/Cp.png)
Binary file added TestCases/vandv/inc_bfs/images/Cp.png
Loading
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
Binary file added TestCases/vandv/inc_bfs/images/Velocity.png
Loading
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
Binary file added TestCases/vandv/inc_bfs/images/bfsw-geom.png
Loading
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
Binary file added TestCases/vandv/inc_bfs/images/tke.png
Loading
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
116 changes: 116 additions & 0 deletions TestCases/vandv/inc_bfs/inc_bfs.cfg
Original file line number Diff line number Diff line change
@@ -0,0 +1,116 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% SU2 configuration file %
% Case description: Backward Facing Step of Driver (incompressible) %
% http://turbmodels.larc.nasa.gov/backstep_val.html %
% Author: Nijso Beishuizen %
% Institution: TU Eindhoven %
% Date: Dec 8th, 2024 %
% File Version 8.1.0 "Harrier" %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% ------------- DIRECT, ADJOINT, AND LINEARIZED PROBLEM DEFINITION ------------%
%
SOLVER= INC_RANS
KIND_TURB_MODEL= SST
SST_OPTIONS= V2003m

RESTART_SOL= YES

% ---------------- INCOMPRESSIBLE FLOW CONDITION DEFINITION -------------------%
%
INC_DENSITY_INIT= 1.2
INC_DENSITY_REF = 1.2

INC_VELOCITY_INIT= ( 44.2, 0.0, 0.0 )
INC_VELOCITY_REF = 44.2
INC_NONDIM= DIMENSIONAL

% --------------------------- VISCOSITY MODEL ---------------------------------%
%
VISCOSITY_MODEL= CONSTANT_VISCOSITY
MU_CONSTANT= 1.8e-05

% ---------------------- REFERENCE VALUE DEFINITION ---------------------------%
%
REF_ORIGIN_MOMENT_X = 0.25
REF_ORIGIN_MOMENT_Y = 0.00
REF_ORIGIN_MOMENT_Z = 0.00
REF_LENGTH= 0.0127
REF_AREA= 1.0
% -------------------- BOUNDARY CONDITION DEFINITION --------------------------%
%
INC_INLET_TYPE= VELOCITY_INLET
INC_INLET_DAMPING= 0.05
INC_OUTLET_TYPE= PRESSURE_OUTLET
SPECIFIED_INLET_PROFILE= YES
INLET_FILENAME= inlet.dat
MARKER_HEATFLUX= ( wall_upper, 0.0, wall_lower_left, 0.0, wall_vertical, 0.0, wall_lower_right, 0.0)
MARKER_INLET= ( inlet, 300.0, 44.2, 1.0, 0.0, 0.0 )
MARKER_INLET_TURBULENT= (inlet, 0.10, 100.0)
MARKER_OUTLET= ( outlet, 0.0)
INLET_MATCHING_TOLERANCE = 1e-3
%

% ------------- COMMON PARAMETERS DEFINING THE NUMERICAL METHOD ---------------%
%
NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES
CFL_NUMBER= 10.0
CFL_ADAPT= YES
CFL_ADAPT_PARAM= ( 0.95, 1.01, 1.0, 100.0 )
ITER= 50000

% ----------------------- SLOPE LIMITER DEFINITION ----------------------------%
%
VENKAT_LIMITER_COEFF= 0.01
ADJ_SHARP_LIMITER_COEFF= 3.0
REF_SHARP_EDGES= 3.0
SENS_REMOVE_SHARP= NO

% ------------------------ LINEAR SOLVER DEFINITION ---------------------------%
%
LINEAR_SOLVER= FGMRES
LINEAR_SOLVER_PREC= LU_SGS
LINEAR_SOLVER_ERROR= 1E-4
LINEAR_SOLVER_ITER= 5

% -------------------- FLOW NUMERICAL METHOD DEFINITION -----------------------%
%
CONV_NUM_METHOD_FLOW= FDS
MUSCL_FLOW= NO
SLOPE_LIMITER_FLOW= VENKATAKRISHNAN
JST_SENSOR_COEFF= ( 0.5, 0.02 )
TIME_DISCRE_FLOW= EULER_IMPLICIT

% -------------------- TURBULENT NUMERICAL METHOD DEFINITION ------------------%
%
CONV_NUM_METHOD_TURB= BOUNDED_SCALAR
MUSCL_TURB= NO
CFL_REDUCTION_TURB= 0.5
SLOPE_LIMITER_TURB= VENKATAKRISHNAN
TIME_DISCRE_TURB= EULER_IMPLICIT

% --------------------------- CONVERGENCE PARAMETERS --------------------------%
%
CONV_RESIDUAL_MINVAL= -10
CONV_STARTITER= 10
CONV_CAUCHY_ELEMS= 500
CONV_CAUCHY_EPS= 1E-6

% ------------------------- INPUT/OUTPUT INFORMATION --------------------------%
%
MESH_FILENAME= mesh_fine_200k.su2

MESH_FORMAT= SU2
MESH_OUT_FILENAME= ./mesh_out.su2
SOLUTION_FILENAME= solution_flow.dat
TABULAR_FORMAT= CSV
CONV_FILENAME= history
RESTART_FILENAME= restart_flow.dat
VOLUME_FILENAME= flow
SURFACE_FILENAME= surface_flow
OUTPUT_WRT_FREQ= 100
SCREEN_OUTPUT= (INNER_ITER, RMS_PRESSURE, RMS_DENSITY, RMS_VELOCITY-X, RMS_VELOCITY-Y, RMS_TKE, RMS_DISSIPATION, LIFT, DRAG, AVG_CFL)
OUTPUT_FILES= RESTART, PARAVIEW_MULTIBLOCK, CSV
VOLUME_OUTPUT= SOLUTION, PRIMITIVE, RESIDUAL