Is the Immersed Boundary (IB) method considered a Direct Numerical Simulation?

A DNS code is the most detailed type of simulation and the most accurate but computationally expensive, right?

What makes a simulation not a DNS?


1 Answer 1


The term immersed boundary method has nothing to do with the term direct numerical simulation.

The immersed boundary method is a numerical methodology that is often used to handle heterogeneous fluid regions in your simulation domain.

For example:

  • Fluid-structure interaction
  • Multi-phase flows

The term direct numerical simulation is often used in the LES community where the underlying equation system, e.g. Navier-Stokes, is numerically solved without any turbulence model. This means that the whole range of spatial and temporal scales of the turbulence must be resolved. The term can also be understood more generally as a highly resolved numerical simulation of a given PDE without additional modelling where all relevant physical effects are sufficiently accurately resolved.

  • $\begingroup$ your last sentence potentially conflicts with your first one $\endgroup$
    – user20857
    Commented Aug 4, 2020 at 18:50
  • $\begingroup$ @Spencer Bryngelson There are a few sentences. Could you be more precise? $\endgroup$
    – ConvexHull
    Commented Aug 4, 2020 at 21:11
  • $\begingroup$ How would you answer this question? $\endgroup$
    – ConvexHull
    Commented Aug 4, 2020 at 21:37
  • 1
    $\begingroup$ @SpencerBryngelson I think we should agree that the question about IBM and DNS is a category error. This is the main issue of my answer. How DNS is defined in different communities is something I didn't want to explain in detail here. There are probably dozens of opinions on this. $\endgroup$
    – ConvexHull
    Commented Aug 5, 2020 at 0:00
  • 2
    $\begingroup$ My take for brevity: IB is a way of dealing with boundary conditions. DNS is a way of dealing with the equation in the domain circumscribed by the boundaries. $\endgroup$ Commented Aug 7, 2020 at 0:50

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