{"id":374241,"date":"2024-07-30T15:00:20","date_gmt":"2024-07-30T15:00:20","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/frozen-field-simulation-not-solving-for-the-scalar-tracer-cfx\/"},"modified":"2024-07-30T15:00:20","modified_gmt":"2024-07-30T15:00:20","slug":"frozen-field-simulation-not-solving-for-the-scalar-tracer-cfx","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/frozen-field-simulation-not-solving-for-the-scalar-tracer-cfx\/","title":{"rendered":"Frozen field simulation not solving for the scalar tracer [CFX]"},"content":{"rendered":"

Hey!<\/p>\n

I’m working on determining the mixing time of a bioreactor at different rpm. To achieve this, a tracer injection (scalar additional variable) is simulated while monitoring its concentration. I work in CFX.<\/p>\n

Due to the geometry of my fluid domain, steady-state simulations don’t converge, so everything is done as a transient simulation, even to establish the velocity fields.<\/p>\n

It works fine when the tracer injection is solved simultaneously with the establishment of the fluid and turbulence fields in a single simulation.<\/p>\n

However, when using a Frozen Field approach, it doesn’t work: all equations for the tracer remain at 0 in the solver step, as if it is never injected or calculated (even though the same injection mechanism works in a simultaneous simulation). For a Frozen Field approach, I’m following this procedure:<\/p>\n

1. Perform a transient simulation (15s) of the reactor stirred at the desired speed. There is no tracer injection, and the tracer concentration (initial conditions) is 0 throughout the entire domain.
2. Add the tracer injection to the same .def file. Using Expert parameters, turn off the equations for the fluid and turbulence while activating the scalar equations.
3. In the solver, use the file from step 2 and solve with double precision, using the results file from step 1 as initial values.<\/p>\n

This procedure doesn’t cause the solver to crash, but the tracer equation (the only one being solved now) remains at 0 (see picture attached).<\/p>\n

Do you have any idea why this might be happening? What am I doing wrong when moving from a simultaneous simulation to a Frozen Field approach?<\/p>\n

Thanks for your help!\"\"<\/p>\n","protected":false},"template":"","class_list":["post-374241","topic","type-topic","status-closed","hentry","topic-tag-ansys-cfx","topic-tag-cfx-tracer-simulation","topic-tag-scalar"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t