Difference between revisions of "Step 1"
(Created page with "= Step 1 = This step is very easy to set-up: it is a simple 2D box with 4 Green-vortices inside it.") |
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| − | = Step 1 = | + | = Step 1 Description = |
| − | This step is | + | The 2-D TGV test case has been already well documented in the scientific literature, e.g. <ref name="abelsamie2016" /><ref name="Laizet2009"/> |
| + | Therefore, only a brief description is given here. | ||
| + | This configuration is used as verification step, since an analytic solution exists~\cite{Taylor1937}. | ||
| + | |||
| + | An incompressible flow with constant density and viscosity is simulated. | ||
| + | |||
| + | The fluid is contained in a square box of dimension <math>[0;L]^2</math> with periodic boundary conditions in both directions. | ||
| + | The value <math>L=2 \pi L_0</math> with <math>L_0 = 1 \; \mathrm{m}</math> has been arbitrarily chosen in the present benchmark for dimensional codes. | ||
| + | The numerical value for the kinematic viscosity is chosen as <math>\nu = 6.25 \times 10^{-4} \; \mathrm{m^2/s}</math> to get suitable conditions, as discussed below. | ||
| + | The initial velocity components are prescribed as follows: | ||
| + | |||
| + | <math> | ||
| + | u(x,y,0) = +u_0 \times \sin(x/L_0) \times \cos(y/L_0)\,, | ||
| + | </math> | ||
| + | |||
| + | <math> | ||
| + | v(x,y,0) = -u_0 \times \cos(x/L_0) \times \sin(y/L_0)\,. | ||
| + | </math> | ||
| + | |||
| + | with <math>u_0 = 1 \; \mathrm{m/s}$. | ||
| + | The flow is thus initially composed of four vortices, one in each quarter of the box. | ||
| + | The vortex turnover time is defined as <math>\tau_\mathrm{ref} = L_0/u_0 = 1\;\mathrm{s}</math>. | ||
| + | For non-dimensional codes, the relevant parameter for this simulation is the vortex Reynolds number, <math>Re=u_0 L_0/\nu = 1,600</math> in the present setup. | ||
| + | It should be noted that the theoretical solution is only stable for sufficiently small Reynolds numbers, explaining why the particular value <math>Re=1,600</math> has been chosen here, as done in many previous studies using the TGV configuration. | ||
| + | |||
| + | A major interest of this test-case is that an analytical solution has been derived for such conditions~\cite{Taylor1937}: | ||
| + | |||
| + | <math> | ||
| + | u(x,y,t) = u(x,y,0) \times \mathrm{e}^{-2\nu t/L_0^2} = u(x,y,0) \times \mathrm{e}^{-2 \, (t/\tau_{\mathrm{ref}}) / \mathrm{Re}} \,, | ||
| + | </math> | ||
| + | |||
| + | <math> | ||
| + | v(x,y,t) = v(x,y,0) \times \mathrm{e}^{-2\nu t/L_0^2} = v(x,y,0) \times \mathrm{e}^{-2 \, (t/\tau_{\mathrm{ref}}) / \mathrm{Re}} \,. | ||
| + | </math> | ||
| + | |||
| + | All physical conditions are now completely defined and only numerical parameters remain to be set. | ||
| + | Based on previously published studies, the recommended parameters for time and space discretization are <math>\Delta t = \tau_\mathrm{ref}/2000 = 5 \times 10^{-4} \; \mathrm{s}</math> and <math>N = 64</math> grid points in each direction. | ||
| + | The flow must be simulated for a physical time of <math>t=10 \; \tau_{\mathrm{ref}}=10\; \mathrm{s}</math>. | ||
| + | |||
| + | = Aside suggestions = | ||
| + | |||
| + | = Notes = | ||
| + | <references> | ||
| + | <ref name="abelsamie2016">A. Abdelsamie and G. Fru and F. Dietzsch and G. Janiga and D. Thévenin , ''Towards direct numerical simulations of low-Mach number turbulent reacting and two-phase flows using immersed boundaries'', '''Comput. Fluids''', 2016 (131-5, pp123--141)</ref>. | ||
| + | <ref name="Laizet2009">S. Laizet and E. Lamballais , ''High-order compact schemes for incompressible flows: A simple and efficient method with quasi-spectral accuracy'', '''J. Comput. Phys.''', 2009 (228, pp5989--6015)</ref>. | ||
| + | </references> | ||
Revision as of 05:42, 27 July 2020
Step 1 Description
The 2-D TGV test case has been already well documented in the scientific literature, e.g. [1][2] Therefore, only a brief description is given here. This configuration is used as verification step, since an analytic solution exists~\cite{Taylor1937}.
An incompressible flow with constant density and viscosity is simulated.
The fluid is contained in a square box of dimension with periodic boundary conditions in both directions. The value with has been arbitrarily chosen in the present benchmark for dimensional codes. The numerical value for the kinematic viscosity is chosen as to get suitable conditions, as discussed below. The initial velocity components are prescribed as follows:
with . For non-dimensional codes, the relevant parameter for this simulation is the vortex Reynolds number, in the present setup. It should be noted that the theoretical solution is only stable for sufficiently small Reynolds numbers, explaining why the particular value has been chosen here, as done in many previous studies using the TGV configuration.
A major interest of this test-case is that an analytical solution has been derived for such conditions~\cite{Taylor1937}:
All physical conditions are now completely defined and only numerical parameters remain to be set. Based on previously published studies, the recommended parameters for time and space discretization are and grid points in each direction. The flow must be simulated for a physical time of .
Aside suggestions
Notes
- ↑ A. Abdelsamie and G. Fru and F. Dietzsch and G. Janiga and D. Thévenin , Towards direct numerical simulations of low-Mach number turbulent reacting and two-phase flows using immersed boundaries, Comput. Fluids, 2016 (131-5, pp123--141)
- ↑ S. Laizet and E. Lamballais , High-order compact schemes for incompressible flows: A simple and efficient method with quasi-spectral accuracy, J. Comput. Phys., 2009 (228, pp5989--6015)
