Parameter exploration TCV IWL - Antoinehoff/personal_gkyl_scripts GitHub Wiki

Overview

This report documents recent simulation results testing parameter modifications in TCV simulations. (Status of each study is indicated by colored circles: 🟢 finished, 🟠 first results but still in progress, 🔴 waiting for the first results.)

1. Corrected Q-Profile (with Shafranov Shift)

• Modification: The q-profile now includes the Shagranov shift in its argument $R=r+R_{axis}$ became $R=R(r,\theta=0)$.
• Status: 🟢
• Results:
  • Minimal impact on species kinetic profiles observed both for NT and PT.
  • Previous simulations remain valid (not compromised by incorrect q-profile) ✅

OBMP densities, NT baseline resolution simulation, restart with Shaf shift in q-prof.
OBMP temperatures, NT baseline resolution simulation, restart from NT baseline, Shaf shift in q-prof.

2. Recycling Source Position

• Modification: Moved recycling source closer to limiter ($\sigma_{src,x} = 0.5 L_x \rightarrow 0.7 L_x$)

• Motivation: Discussion with Greg on improving physical coherence relative to the results of Coroado et al. 2022. The previous position was inspired solely by the result on ionization rate but half of the neutral-ion process is related to charge exchange, which occurs closer to the limiter.

• Status: 🟠

• Results:

  • Reduced ion temperature depletion ✅
  • Lowered electron SOL temperature ✅
  • Effects observed both for NT and PT.

Ion source density injection with $\sigma_x=0.7x{LCFS}$ (left), and $\sigma_x=0.5x_{LCFS}$ (right)._
OBMP densities, NT baseline resolution, restart from NT baseline simulation with Shafranov shift in q-profile and source moved closer to limiter.
OBMP temperatures, NT baseline resolution simulation, restart with Shafranov shift in q-profile and source moved closer to limiter.

3. Increase Parallel Resolution

• Modification: Increased parallel resolution from 12 to 32 in coarse resolution simulations.
• Status: 🟠
• Results:
  • The quasi-steady state reached in coarse simulation with $N_z=12$ is destabilized by the increase in parallel resolution ⚠️
  • Needs to be run longer to see what it will converge towards.

Time evolution of OBMP profiles, PT coarse resolution, restart from 2ms PT coarse sim with $N_z=32$.

4. Reduction of the Collision Frequency

• Modifications: Change $\nu_{frac}=0.5$ to $\nu_{frac}=0.1$
• Status: 🟢
• Results:
  • A reduction of collision yields unphysical results. In particular, the electron temperature rises significantly, and the ion temperature decreases, especially in the SOL region. This is likely due to the reduced collisionality leading to less effective energy transfer between electrons and ions.
  • The NT case is based on a restart and similar conclusions can be drawn.
  • ➡️ A high enough collision frequency is crucial to obtain physically realistic temperature profiles.

OBMP densities, PT coarse resolution simulation, start from scratch, $\nu{frac}=0.1$._
OBMP temperatures, PT coarse resolution simulation, start from scratch, $\nu{frac}=0.1$._
OBMP temperatures, NT coarse resolution simulation, restart from NT coarse sim., $\nu{frac}=0.1$._

5. Increase of the Collision Frequency

• Modifications: Change $\nu_{frac}=0.5$ to $\nu_{frac}=1.0$
• Status: 🔴
• Results: