Effective boundary conditions for compressible flows over rough boundaries

2015 ◽  
Vol 25 (07) ◽  
pp. 1257-1297 ◽  
Author(s):  
Giulia Deolmi ◽  
Wolfgang Dahmen ◽  
Siegfried Müller
Keyword(s):  
Boundary Conditions ◽  
Compressible Flows ◽  
Incompressible Flows ◽  
Laminar Flows ◽  
Small Scale ◽  
Reynolds Number Flow ◽  
Effective Boundary ◽  
Effective Boundary Conditions ◽  
High Reynolds ◽  
Rough Boundaries

Simulations of a flow over a roughness are prohibitively expensive for small-scale structures. If the interest is only on some macroscale quantity it will be sufficient to model the influence of the unresolved microscale effects. Such multiscale models rely on an appropriate upscaling strategy. Here the strategy originally developed by Achdou et al. [Effective boundary conditions for laminar flows over periodic rough boundaries, J. Comput. Phys. 147 (1998) 187–218] for incompressible flows is extended to compressible high Reynolds number flow. For proof of concept a laminar flow over a flat plate with partially embedded roughness is simulated. The results are compared with computations on a rough domain.

Effective Boundary Conditions: A General Strategy and Application to Compressible Flows Over Rough Boundaries

2017 ◽  
Vol 21 (2) ◽  
pp. 358-400 ◽  
Author(s):  
Giulia Deolmi ◽  
Wolfgang Dahmen ◽  
Siegfried Müller
Keyword(s):  
Boundary Conditions ◽  
Compressible Flows ◽  
Stokes Equations ◽  
Scale Effects ◽  
Multiscale Model ◽  
Local Regularity ◽  
General Strategy ◽  
Micro Scale ◽  
Effective Boundary ◽  
Effective Boundary Conditions

AbstractDetermining the drag of a flowover a rough surface is a guiding example for the need to take geometric micro-scale effects into account when computing a macroscale quantity. A well-known strategy to avoid a prohibitively expensive numerical resolution of micro-scale structures is to capture the micro-scale effects through someeffective boundary conditionsposed for a problem on a (virtually) smooth domain. The central objective of this paper is to develop a numerical scheme for accurately capturing the micro-scale effects at essentially the cost of twice solving a problem on a (piecewise)smoothdomain at affordable resolution. Here and throughout the paper “smooth” means the absence of any micro-scale roughness. Our derivation is based on a “conceptual recipe” formulated first in a simplified setting of boundary value problems under the assumption of sufficient local regularity to permit asymptotic expansions in terms of the micro-scale parameter.The proposed multiscale model relies then on an upscaling strategy similar in spirit to previous works by Achdou et al. [1], Jäger and Mikelic [29, 31], Friedmann et al. [24, 25], forincompressiblefluids. Extensions tocompressiblefluids, although with several noteworthy distinctions regarding e.g. the “micro-scale size” relative to boundary layer thickness or the systematic treatment of different boundary conditions, are discussed in Deolmi et al. [16,17]. For proof of concept the general strategy is applied to the compressible Navier-Stokes equations to investigate steady, laminar, subsonic flow over a flat plate with partially embedded isotropic and anisotropic periodic roughness imposing adiabatic and isothermal wall conditions, respectively. The results are compared with high resolution direct simulations on a fully resolved rough domain.

Influence of wall roughness on the slip behaviour of viscous fluids

2008 ◽  
Vol 138 (5) ◽  
pp. 957-973 ◽  
Author(s):  
Dorin Bucur ◽  
Eduard Feireisl ◽  
Šárka Nečasová
Keyword(s):  
Boundary Condition ◽  
Viscous Fluid ◽  
Boundary Conditions ◽  
Limit Problem ◽  
Viscous Fluids ◽  
Wall Roughness ◽  
Effective Boundary ◽  
Specific Direction ◽  
Friction Term ◽  
Effective Boundary Conditions

We consider the stationary equations of a general viscous fluid in an infinite (periodic) slab supplemented with Navier's boundary condition with a friction term on the upper part of the boundary. In addition, we assume that the upper part of the boundary is described by a graph of a function φε, where φε oscillates in a specific direction with amplitude proportional to ε. We identify the limit problem when ε → 0, in particular, the effective boundary conditions.

Sign in / Sign up

Export Citation Format

Share Document