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<div style="line-break:after-white-space">Dear PETSc team,
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<div>We are solving the Stokes equations using PETSc (via Firedrake) on a highly anisotropic 3D domain (L_x=1, L_y=0.01, L_z=0.1).</div>
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<div>In this setup, standard Schur complement preconditioners using a mass inverse for pressure struggle to converge. We could solve the problem with the LSC preconditioner (solver parameters are shown in the script). </div>
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<div>We have the following questions:</div>
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<li>Why standard preconditioners struggle in such domains? </li><li>Why is the preconditioned residual norm for the Schur complement system much higher than the true residual norm?</li><li>Would you recommend alternative or more robust preconditioners for such geometries? </li></ul>
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<div>Thank you for your help. </div>
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<div>Best regards, </div>
<div>Hardik</div>
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