FlowManager

Summary

class pvade.fluid.FlowManager.Flow(domain, params)

This class solves the CFD problem

Initialize the fluid solver

This method initialize the Flow object, namely, it creates all the necessary function spaces on the mesh, initializes key counting and boolean variables and records certain characteristic quantities like the minimum cell size and the number of degrees of freedom attributed to both the pressure and velocity function spaces.

Parameters:

domain (pvade.geometry.MeshManager.Domain) – A Domain object

_assemble_system(params)

Pre-assemble all LHS matrices and RHS vectors

Here we pre-assemble all the forms corresponding to the left-hand side matrices and right-hand side vectors once outside the time loop. This will enable us to re-use certain features like the sparsity pattern during the timestepping without any modification of the function calls.

Parameters:

params (pvade.Parameters.SimParams) – A SimParams object

_solver_step_1(params)

Solve step 1: tentative velocity

Here we calculate the tentative velocity which, not guaranteed to be divergence free.

Parameters:

params (pvade.Parameters.SimParams) – A SimParams object

_solver_step_2(params)

Solve step 2: pressure correction

Here we calculate the pressure field that would be required to correct the tentative velocity such that it is divergence free.

Parameters:

params (pvade.Parameters.SimParams) – A SimParams object

_solver_step_3(params)

Solve step 3: velocity update

Here we update the tentative velocity with the effect of the modified, continuity-enforcing pressure field.

Parameters:

params (pvade.Parameters.SimParams) – A SimParams object

_solver_step_4(params)

Solve step 4: Solves for temperature using the advection-diffusion equation

Parameters:

params (pvade.Parameters.SimParams) – A SimParams object

_solver_step_5(params)

Solve step 5: Projects stress onto a tensor function space

Parameters:

params (pvade.Parameters.SimParams) – A SimParams object

adjust_dpdx_for_constant_flux()

Adjust the forcing term, dpdx, to maintain flowrate

Here we calculate what the value of the dolfinx.fem.constant driving pressure/force, dpdx, should be adjusted to to maintain a dolfinx.fem.constant flux through the domain. This is a useful option if performing a periodic simulation in which the flux will slowly decay due to viscous dissipation. The amount of change in dpdx is calculated by comparing the current flux to the flux measured in the initial condition and then employing a PID controller to adjust the driving force to seek the target defined by the initial condition.

Parameters:

None

build_boundary_conditions(domain, params)

Build the boundary conditions

A method to manage the building of boundary conditions, including the steps of identifying entities on the boundary, marking those degrees of freedom either by the identified facets or a gmsh marker function, and finally assembling a list of Boundary objects that enforce the correct value.

Parameters:

• domain (pvade.geometry.MeshManager.Domain) – A Domain object

• params (pvade.Parameters.SimParams) – A SimParams object

build_forms(domain, params)

Builds all variational statements

This method creates all the functions, expressions, and variational forms that will be needed for the numerical solution of Navier Stokes using a fractional step method. This includes the calculation of a tentative velocity, the calculation of the change in pressure required to correct the tentative velocity to enforce continuity, and the update to the velocity field to reflect this change in pressure.

Parameters:

• domain (pvade.geometry.MeshManager.Domain) – A Domain object

• params (pvade.Parameters.SimParams) – A SimParams object

compute_cfl()

Solve for the CFL number

Using the velocity, timestep size, and cell sizes, we calculate a CFL number at every mesh cell. From that, we select the single highest value of CFL number and record it for the purposes of monitoring simulation stability.

Parameters:

None

solve(domain, params, current_time)

Solve for a single timestep advancement

Here we perform the three-step solution process (tentative velocity, pressure correction, velocity update) to advance the fluid simulation a single timestep. Additionally, we calculate the new CFL number associated with the latest velocity solution.

Parameters:

params (pvade.Parameters.SimParams) – A SimParams object