Asymptotic modeling of the wave-propagation over acoustic liners - - PowerPoint PPT Presentation

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Asymptotic modeling of the wave-propagation over acoustic liners - - PowerPoint PPT Presentation

Asymptotic modeling of the wave-propagation over acoustic liners Adrien Semin Technische Universit at Berlin, Institut f ur Mathematik Joint work with Kersten Schmidt (TU Berlin) and B erang` ere Delourme (Paris 13) Research Center M


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SLIDE 1

Asymptotic modeling of the wave-propagation over acoustic liners

Adrien Semin

Technische Universit¨ at Berlin, Institut f¨ ur Mathematik Joint work with Kersten Schmidt (TU Berlin) and B´ erang` ere Delourme (Paris 13)

Research Center MATHEON Mathematics for key technologies

Analysis and Numerics of Acoustic and Electromagnetic Problems, October 17th-22nd

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SLIDE 2

Background

Optimized noise reduction in transportation and interior spaces

Courtesy of A. Th¨

  • ns-Zueva

Jet engines of air-planes ⊲ Absorption of the generated acoustic pressure at different frequencies (noise) Jet engines and turbo machines ⊲ Damping of acoustic instabilities in the combustion chamber at particular frequencies

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SLIDE 3

Motivation

Bias flow liner in an acoustic channel (DUCT-C) at the institute of Institute of Propulsion Technology at DLR Berlin (courtesy of F. Bake)

Perforated liners absorb acoustic waves ⊲ Absorption due to viscosity and interaction with flow through holes ⊲ Measurements at realistic temperatures, pressures are extremely expensive ⊲ Direct numerical simulations not feasible (small holes, boundary layer ≪ wave-length)

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SLIDE 4

Outline

1

Surface homogenization for micro-structured layers with singularities

2

Extension of the macroscopic part of the solution Periodic layer obstacle and transmission conditions (2 scales) End-point of the periodic layer and corner singularities Periodic layer obstacle and transmission conditions (3 scales)

3

Numerical simulations

4

Conclusion and perspectives

4 / 34

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SLIDE 5

Outline

1

Surface homogenization for micro-structured layers with singularities

2

Extension of the macroscopic part of the solution Periodic layer obstacle and transmission conditions (2 scales) End-point of the periodic layer and corner singularities Periodic layer obstacle and transmission conditions (3 scales)

3

Numerical simulations

4

Conclusion and perspectives

5 / 34

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SLIDE 6

Surface homogenization for micro-structured layers with singularities

Θ x− O h(δ) x+ O η(δ) δ x− O Θ x+ O

Γ Figure: On the left: the exact domain Ωδ,η. On the right: the limit domain Ω0.

⊲ Navier-Stokes equation with non-linear advection for isothermal process ∂t v + (v ·∇) v + ∇p − ν∆ v = f in Ωδ,η Conservation of momentum ∂tp + c2 div v + v ·∇p + p div v = 0 in Ωδ,η Conservation of mass v = 0

  • n ∂Ωδ,η

No-slip boundary condition Here, p = p′/ρ0, where p′ is the acoustic pressure, and ν is the kinematic viscosity. ⊲ This model contains effects of different nature: small geometrical scales (δ, η(δ), h(δ)), re-entrant corners, viscosity (ν = ν(δ)) , non-linearity. ⊲ In the following, we develop the surface homogenization method in which the effect of the micro-structure and the viscosity is there (taken into account through Wentzel boundary conditions) for a single frequency excitation (f(t, x) = F(x) exp(−ıωt)).

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SLIDE 7

Surface homogenization for micro-structured layers with singularities

Θ x− O h(δ) x+ O η(δ) δ x− O Θ x+ O

Γ Figure: On the left: the exact domain Ωδ,η. On the right: the limit domain Ω0.

⊲ Navier-Stokes equation with non-linear advection for isothermal process ∂t v + (v ·∇) v + ∇p − ν∆ v = f in Ωδ,η Conservation of momentum ∂tp + c2 div v + v ·∇p + p div v = 0 in Ωδ,η Conservation of mass v = 0

  • n ∂Ωδ,η

No-slip boundary condition Here, p = p′/ρ0, where p′ is the acoustic pressure, and ν is the kinematic viscosity. ⊲ This model contains effects of different nature: small geometrical scales (δ, η(δ), h(δ)), re-entrant corners, viscosity (ν = ν(δ)) , non-linearity. ⊲ In the following, we develop the surface homogenization method in which the effect of the micro-structure and the viscosity is there (taken into account through Wentzel boundary conditions) for a single frequency excitation (f(t, x) = F(x) exp(−ıωt)).

6 / 34

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SLIDE 8

Surface homogenization for micro-structured layers with singularities

Θ x− O h(δ) x+ O η(δ) δ x− O Θ x+ O

Γ Figure: On the left: the exact domain Ωδ,η. On the right: the limit domain Ω0.

⊲ Navier-Stokes equation with non-linear advection for isothermal process ∂t v + (v ·∇) v + ∇p − ν∆ v = f in Ωδ,η Conservation of momentum ∂tp + c2 div v + v ·∇p + p div v = 0 in Ωδ,η Conservation of mass v = 0

  • n ∂Ωδ,η

No-slip boundary condition Here, p = p′/ρ0, where p′ is the acoustic pressure, and ν is the kinematic viscosity. ⊲ This model contains effects of different nature: small geometrical scales (δ, η(δ), h(δ)), re-entrant corners, viscosity (ν = ν(δ)) , non-linearity. ⊲ In the following, we develop the surface homogenization method in which the effect of the micro-structure and the viscosity is there (taken into account through Wentzel boundary conditions) for a single frequency excitation (f(t, x) = F(x) exp(−ıωt)).

6 / 34

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SLIDE 9

Surface homogenization for micro-structured layers with singularities

⊲ This model is considered on a geometry that is dependent on a small parameter δ.

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SLIDE 10

Surface homogenization for micro-structured layers with singularities

⊲ This model is considered on a geometry that is dependent on a small parameter δ. ⊲ Solving directly this problem numerically, with a mesh that resolves this exact geometry, is costly:

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SLIDE 11

Surface homogenization for micro-structured layers with singularities

⊲ This model is considered on a geometry that is dependent on a small parameter δ. ⊲ Solving directly this problem numerically, with a mesh that resolves this exact geometry, is costly: ⊲ Then, we aim for describing an efficient model in which we don’t need to resolve the small geometrical scales.

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SLIDE 12

Surface homogenization for micro-structured layers with singularities

⊲ Previous system can be reduced to an Helmholtz equation with Wentzel boundary conditions, with homogeneous wave number k0 := ω/c and viscosity parameter ν′(δ): ∆pδ + k2

0pδ = div F,

in Ωδ,η, ∂npδ + (1 + ı)

  • ν′(δ)∂2

t pδ = 0,

  • n ∂Ωδ,η.
  • K. Schmidt, A. Th¨
  • ns-Zueva, J. Joly. Asymptotic analysis for acoustics in viscous

gases close to rigid walls. Math. Models Meth. Appl. Sci., 24, 2014. ⊲ Away from the periodic layer, pδ is described by its macroscopic part p(x), ⊲ close to the periodic layer, the macroscopic part is corrected by a periodic boundary layer Π(x1, x/δ), ⊲ close to the end-point x±

O of the periodic layer, the macroscopic part is corrected by a

near field corrector P±((x − x±

O )/δ).

⊲ Goal: derive an effective macroscopic description of the solution.

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SLIDE 13

Surface homogenization for micro-structured layers with singularities

⊲ Previous system can be reduced to an Helmholtz equation with Wentzel boundary conditions, with homogeneous wave number k0 := ω/c and viscosity parameter ν′(δ): ∆pδ + k2

0pδ = div F,

in Ωδ,η, ∂npδ + (1 + ı)

  • ν′(δ)∂2

t pδ = 0,

  • n ∂Ωδ,η.
  • K. Schmidt, A. Th¨
  • ns-Zueva, J. Joly. Asymptotic analysis for acoustics in viscous

gases close to rigid walls. Math. Models Meth. Appl. Sci., 24, 2014. ⊲ Away from the periodic layer, pδ is described by its macroscopic part p(x), ⊲ close to the periodic layer, the macroscopic part is corrected by a periodic boundary layer Π(x1, x/δ), ⊲ close to the end-point x±

O of the periodic layer, the macroscopic part is corrected by a

near field corrector P±((x − x±

O )/δ).

⊲ Goal: derive an effective macroscopic description of the solution.

8 / 34

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SLIDE 14

Surface homogenization for micro-structured layers with singularities

⊲ Previous system can be reduced to an Helmholtz equation with Wentzel boundary conditions, with homogeneous wave number k0 := ω/c and viscosity parameter ν′(δ): ∆pδ + k2

0pδ = div F,

in Ωδ,η, ∂npδ + (1 + ı)

  • ν′(δ)∂2

t pδ = 0,

  • n ∂Ωδ,η.
  • K. Schmidt, A. Th¨
  • ns-Zueva, J. Joly. Asymptotic analysis for acoustics in viscous

gases close to rigid walls. Math. Models Meth. Appl. Sci., 24, 2014. ⊲ Away from the periodic layer, pδ is described by its macroscopic part p(x), ⊲ close to the periodic layer, the macroscopic part is corrected by a periodic boundary layer Π(x1, x/δ), ⊲ close to the end-point x±

O of the periodic layer, the macroscopic part is corrected by a

near field corrector P±((x − x±

O )/δ).

⊲ Goal: derive an effective macroscopic description of the solution.

8 / 34

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SLIDE 15

Surface homogenization for micro-structured layers with singularities

⊲ Previous system can be reduced to an Helmholtz equation with Wentzel boundary conditions, with homogeneous wave number k0 := ω/c and viscosity parameter ν′(δ): ∆pδ + k2

0pδ = div F,

in Ωδ,η, ∂npδ + (1 + ı)

  • ν′(δ)∂2

t pδ = 0,

  • n ∂Ωδ,η.
  • K. Schmidt, A. Th¨
  • ns-Zueva, J. Joly. Asymptotic analysis for acoustics in viscous

gases close to rigid walls. Math. Models Meth. Appl. Sci., 24, 2014. ⊲ Away from the periodic layer, pδ is described by its macroscopic part p(x), ⊲ close to the periodic layer, the macroscopic part is corrected by a periodic boundary layer Π(x1, x/δ), ⊲ close to the end-point x±

O of the periodic layer, the macroscopic part is corrected by a

near field corrector P±((x − x±

O )/δ).

⊲ Goal: derive an effective macroscopic description of the solution.

8 / 34

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SLIDE 16

Surface homogenization for micro-structured layers with singularities

⊲ Previous system can be reduced to an Helmholtz equation with Wentzel boundary conditions, with homogeneous wave number k0 := ω/c and viscosity parameter ν′(δ): ∆pδ + k2

0pδ = div F,

in Ωδ,η, ∂npδ + (1 + ı)

  • ν′(δ)∂2

t pδ = 0,

  • n ∂Ωδ,η.
  • K. Schmidt, A. Th¨
  • ns-Zueva, J. Joly. Asymptotic analysis for acoustics in viscous

gases close to rigid walls. Math. Models Meth. Appl. Sci., 24, 2014. ⊲ Away from the periodic layer, pδ is described by its macroscopic part p(x), ⊲ close to the periodic layer, the macroscopic part is corrected by a periodic boundary layer Π(x1, x/δ), ⊲ close to the end-point x±

O of the periodic layer, the macroscopic part is corrected by a

near field corrector P±((x − x±

O )/δ).

⊲ Goal: derive an effective macroscopic description of the solution.

8 / 34

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SLIDE 17

Surface homogenization for micro-structured layers with singularities

x−

O

x+

O

⊲ We are interested in the macroscopic part of the solution, defined on a domain dependent on δ . . . ⊲ and we would like to extend it on the limit domain Ω0. ⊲ Extension of macroscopic part towards the limit interface Γ might not be done in a continuous way and lead to transmission conditions. ⊲ Extension of macroscopic part towards the end-points x±

O might not be done in a

regular way and lead to corner conditions.

9 / 34

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SLIDE 18

Surface homogenization for micro-structured layers with singularities

x−

O

x+

O

⊲ We are interested in the macroscopic part of the solution, defined on a domain dependent on δ . . . ⊲ and we would like to extend it on the limit domain Ω0. ⊲ Extension of macroscopic part towards the limit interface Γ might not be done in a continuous way and lead to transmission conditions. ⊲ Extension of macroscopic part towards the end-points x±

O might not be done in a

regular way and lead to corner conditions.

9 / 34

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SLIDE 19

Surface homogenization for micro-structured layers with singularities

x−

O

x+

O

⊲ We are interested in the macroscopic part of the solution, defined on a domain dependent on δ . . . ⊲ and we would like to extend it on the limit domain Ω0. ⊲ Extension of macroscopic part towards the limit interface Γ might not be done in a continuous way and lead to transmission conditions. ⊲ Extension of macroscopic part towards the end-points x±

O might not be done in a

regular way and lead to corner conditions.

9 / 34

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SLIDE 20

Surface homogenization for micro-structured layers with singularities

x−

O

x+

O

⊲ We are interested in the macroscopic part of the solution, defined on a domain dependent on δ . . . ⊲ and we would like to extend it on the limit domain Ω0. ⊲ Extension of macroscopic part towards the limit interface Γ might not be done in a continuous way and lead to transmission conditions. ⊲ Extension of macroscopic part towards the end-points x±

O might not be done in a

regular way and lead to corner conditions.

9 / 34

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SLIDE 21

Surface homogenization for micro-structured layers with singularities

x−

O

x+

O

⊲ We are interested in the macroscopic part of the solution, defined on a domain dependent on δ . . . ⊲ and we would like to extend it on the limit domain Ω0. ⊲ Extension of macroscopic part towards the limit interface Γ might not be done in a continuous way and lead to transmission conditions. ⊲ Extension of macroscopic part towards the end-points x±

O might not be done in a

regular way and lead to corner conditions.

9 / 34

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SLIDE 22

Surface homogenization for micro-structured layers with singularities

Γ x−

O

x+

O

⊲ We are interested in the macroscopic part of the solution, defined on a domain dependent on δ . . . ⊲ and we would like to extend it on the limit domain Ω0. ⊲ Extension of macroscopic part towards the limit interface Γ might not be done in a continuous way and lead to transmission conditions. ⊲ Extension of macroscopic part towards the end-points x±

O might not be done in a

regular way and lead to corner conditions.

9 / 34

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SLIDE 23

Surface homogenization for micro-structured layers with singularities

Γ x−

O

x+

O

⊲ We are interested in the macroscopic part of the solution, defined on a domain dependent on δ . . . ⊲ and we would like to extend it on the limit domain Ω0. ⊲ Extension of macroscopic part towards the limit interface Γ might not be done in a continuous way and lead to transmission conditions. ⊲ Extension of macroscopic part towards the end-points x±

O might not be done in a

regular way and lead to corner conditions.

9 / 34

slide-24
SLIDE 24

Surface homogenization for micro-structured layers with singularities

Γ x−

O

x+

O

⊲ We are interested in the macroscopic part of the solution, defined on a domain dependent on δ . . . ⊲ and we would like to extend it on the limit domain Ω0. ⊲ Extension of macroscopic part towards the limit interface Γ might not be done in a continuous way and lead to transmission conditions. ⊲ Extension of macroscopic part towards the end-points x±

O might not be done in a

regular way and lead to corner conditions.

9 / 34

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SLIDE 25

Outline

1

Surface homogenization for micro-structured layers with singularities

2

Extension of the macroscopic part of the solution Periodic layer obstacle and transmission conditions (2 scales) End-point of the periodic layer and corner singularities Periodic layer obstacle and transmission conditions (3 scales)

3

Numerical simulations

4

Conclusion and perspectives

10 / 34

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SLIDE 26

Extension of the macroscopic part of the solution

Θ x− O h(δ) x+ O η(δ) δ x− O Θ x+ O

Γ

∂npδ + (1 + ı)

  • ν′(δ)∂2

t pδ = 0

h(δ) δ η(δ) Γ Goal: extend the macroscopic part of the solution towards the limit interface Γ, including its end-points. ⊲ First story: 2 scales (

  • ν′(δ) = ζδ, h(δ) = Hδ and η(δ) = ρδ, 0 < ρ < 1).

⊲ Second story: (inviscid) 3 scales (

  • ν′(δ) = 0, h = Hη(δ) and η(δ) = o(δ)).

11 / 34

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SLIDE 27

Outline

1

Surface homogenization for micro-structured layers with singularities

2

Extension of the macroscopic part of the solution Periodic layer obstacle and transmission conditions (2 scales) End-point of the periodic layer and corner singularities Periodic layer obstacle and transmission conditions (3 scales)

3

Numerical simulations

4

Conclusion and perspectives

12 / 34

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SLIDE 28

Periodic layer obstacle and transmission conditions (2 scales)

Hδ δ ρδ ∆pδ + k2

0pδ = div F,

in Ωδ, ∂npδ + (1 + ı)ζδ∂2

t pδ = 0,

  • n ∂Ωδ.

Goal: derive an approximate model on the limit geometry Ω0. Tool: surface homogenization. pδ(x) = pδ

0(x) + δpδ 1(x) + . . . ,

away from Γ, pδ(x) = Πδ

  • x1, x

δ

  • + δΠδ

1

  • x1, x

δ

  • + . . . ,

close to Γ. Γ Ω = Ω0 \ Γ

13 / 34

slide-29
SLIDE 29

Periodic layer obstacle and transmission conditions (2 scales)

Hδ δ ρδ ∆pδ + k2

0pδ = div F,

in Ωδ, ∂npδ + (1 + ı)ζδ∂2

t pδ = 0,

  • n ∂Ωδ.

Goal: derive an approximate model on the limit geometry Ω0. Tool: surface homogenization. pδ(x) = pδ

0(x) + δpδ 1(x) + . . . ,

away from Γ, pδ(x) = Πδ

  • x1, x

δ

  • + δΠδ

1

  • x1, x

δ

  • + . . . ,

close to Γ. Γ Ω = Ω0 \ Γ

13 / 34

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SLIDE 30

Periodic layer obstacle and transmission conditions (2 scales)

Hδ δ ρδ ∆pδ + k2

0pδ = div F,

in Ωδ, ∂npδ + (1 + ı)ζδ∂2

t pδ = 0,

  • n ∂Ωδ.

Goal: derive an approximate model on the limit geometry Ω0. Tool: surface homogenization. pδ(x) = pδ

0(x) + δpδ 1(x) + . . . ,

away from Γ, pδ(x) = Πδ

  • x1, x

δ

  • + δΠδ

1

  • x1, x

δ

  • + . . . ,

close to Γ. Γ Ω = Ω0 \ Γ

13 / 34

slide-31
SLIDE 31

Periodic layer obstacle and transmission conditions (2 scales)

Hδ δ ρδ ∆pδ + k2

0pδ = div F,

in Ωδ, ∂npδ + (1 + ı)ζδ∂2

t pδ = 0,

  • n ∂Ωδ.

Goal: derive an approximate model on the limit geometry Ω0. Tool: surface homogenization. pδ(x) = pδ

0(x) + δpδ 1(x) + . . . ,

away from Γ, pδ(x) = Πδ

  • x1, x

δ

  • + δΠδ

1

  • x1, x

δ

  • + . . . ,

close to Γ. Γ Ω = Ω0 \ Γ The limit term pδ

0 satisfies

          

∆pδ

0 + k2 0pδ 0 = div F,

in Ω ∂npδ

0 = 0,

  • n ∂Ω0
  • Γ = 0,
  • ∂x2pδ
  • Γ = 0.

13 / 34

slide-32
SLIDE 32

Periodic layer obstacle and transmission conditions (2 scales)

Hδ δ ρδ ∆pδ + k2

0pδ = div F,

in Ωδ, ∂npδ + (1 + ı)ζδ∂2

t pδ = 0,

  • n ∂Ωδ.

Goal: derive an approximate model on the limit geometry Ω0. Tool: surface homogenization. pδ(x) = pδ

0(x) + δpδ 1(x) + . . . ,

away from Γ, pδ(x) = Πδ

  • x1, x

δ

  • + δΠδ

1

  • x1, x

δ

  • + . . . ,

close to Γ. Γ Ω = Ω0 \ Γ The first corrector pδ

1 satisfies

          

∆pδ

1 + k2 0pδ 1 = 0,

in Ω ∂npδ

1 = −(1 + ı)ζ∂2 t pδ 0,

  • n ∂Ω0

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ ,
  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

Constants D∞ and N0 are given through the resolution of a periodic cell problem (see next slide).

13 / 34

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SLIDE 33

Periodic layer obstacle and transmission conditions (2 scales)

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ

and

  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

H ρ X1 X2

  • ΩH

X1 = 0 X1 = 1 ⊲ Making a δ-scale around one hole ⇒ periodic cell domain

  • Ω = (0, 1) × R \

ΩH. ⊲ In this domain, resolution of the blockage function

            

∆D = 0, in Ω, ∂nD + (1 + ı)ζ∂2

t D = 0,

  • n ∂

ΩH, D(1, X2) = D(1, X2), X2 ∈ (−H, 0), ∂X1D(1, X2) = ∂X1D(1, X2), X2 ∈ (−H, 0), D(X1, X2) − X2 is bounded. ⊲ This function is defined up to an additive constant. This constant is chosen, taking the blockage coefficient D∞ such that lim

X2→±∞ D(X1, X2) − (X2 ± D∞) = 0

⊲ Numerical computation: truncation to |X2| < B, using DtN

  • perators on |X2| = B.

14 / 34

slide-34
SLIDE 34

Periodic layer obstacle and transmission conditions (2 scales)

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ

and

  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

H ρ X1 X2

  • ΩH

X1 = 0 X1 = 1 ⊲ Making a δ-scale around one hole ⇒ periodic cell domain

  • Ω = (0, 1) × R \

ΩH. ⊲ In this domain, resolution of the blockage function

            

∆D = 0, in Ω, ∂nD + (1 + ı)ζ∂2

t D = 0,

  • n ∂

ΩH, D(1, X2) = D(1, X2), X2 ∈ (−H, 0), ∂X1D(1, X2) = ∂X1D(1, X2), X2 ∈ (−H, 0), D(X1, X2) − X2 is bounded. ⊲ This function is defined up to an additive constant. This constant is chosen, taking the blockage coefficient D∞ such that lim

X2→±∞ D(X1, X2) − (X2 ± D∞) = 0

⊲ Numerical computation: truncation to |X2| < B, using DtN

  • perators on |X2| = B.

14 / 34

slide-35
SLIDE 35

Periodic layer obstacle and transmission conditions (2 scales)

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ

and

  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

H ρ X1 X2

  • ΩH

X1 = 0 X1 = 1 ⊲ Making a δ-scale around one hole ⇒ periodic cell domain

  • Ω = (0, 1) × R \

ΩH. ⊲ In this domain, resolution of the blockage function

            

∆D = 0, in Ω, ∂nD + (1 + ı)ζ∂2

t D = 0,

  • n ∂

ΩH, D(1, X2) = D(1, X2), X2 ∈ (−H, 0), ∂X1D(1, X2) = ∂X1D(1, X2), X2 ∈ (−H, 0), D(X1, X2) − X2 is bounded. ⊲ This function is defined up to an additive constant. This constant is chosen, taking the blockage coefficient D∞ such that lim

X2→±∞ D(X1, X2) − (X2 ± D∞) = 0

⊲ Numerical computation: truncation to |X2| < B, using DtN

  • perators on |X2| = B.

14 / 34

slide-36
SLIDE 36

Periodic layer obstacle and transmission conditions (2 scales)

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ

and

  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

H ρ X1 X2

  • ΩH

X2 = B X2 = −B X1 = 0 X1 = 1 ⊲ Making a δ-scale around one hole ⇒ periodic cell domain

  • Ω = (0, 1) × R \

ΩH. ⊲ In this domain, resolution of the blockage function

            

∆D = 0, in Ω, ∂nD + (1 + ı)ζ∂2

t D = 0,

  • n ∂

ΩH, D(1, X2) = D(1, X2), X2 ∈ (−H, 0), ∂X1D(1, X2) = ∂X1D(1, X2), X2 ∈ (−H, 0), D(X1, X2) − X2 is bounded. ⊲ This function is defined up to an additive constant. This constant is chosen, taking the blockage coefficient D∞ such that lim

X2→±∞ D(X1, X2) − (X2 ± D∞) = 0

⊲ Numerical computation: truncation to |X2| < B, using DtN

  • perators on |X2| = B.

14 / 34

slide-37
SLIDE 37

Outline

1

Surface homogenization for micro-structured layers with singularities

2

Extension of the macroscopic part of the solution Periodic layer obstacle and transmission conditions (2 scales) End-point of the periodic layer and corner singularities Periodic layer obstacle and transmission conditions (3 scales)

3

Numerical simulations

4

Conclusion and perspectives

15 / 34

slide-38
SLIDE 38

End-point of the periodic layer and corner singularities

x−

O

x+

O

Θ Γ x−

O

x+

O

Θ

⊲ Reminder from what we have just seen previously:

          

(∆ + k2

0)pδ 0 = div F,

(∆ + k2

0)pδ 1 = 0,

∂npδ

0 = 0,

∂npδ

1 = −(1 + ı)ζ∂2 t pδ 0,

  • Γ = 0,

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ ,
  • ∂x2pδ
  • Γ = 0,
  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

with term pδ

0 and pδ 1 that hare H1 regularity away from the corners.

⊲ If pδ

0 ∈ H1(Ω), can we find pδ 1 ∈ H1(Ω) satisfying these transmission conditions?

⊲ Can we even consider pδ

0 ∈ H1(Ω)?

16 / 34

slide-39
SLIDE 39

End-point of the periodic layer and corner singularities

x−

O

x+

O

Θ Γ x−

O

x+

O

Θ

⊲ Reminder from what we have just seen previously:

          

(∆ + k2

0)pδ 0 = div F,

(∆ + k2

0)pδ 1 = 0,

∂npδ

0 = 0,

∂npδ

1 = −(1 + ı)ζ∂2 t pδ 0,

  • Γ = 0,

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ ,
  • ∂x2pδ
  • Γ = 0,
  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

with term pδ

0 and pδ 1 that hare H1 regularity away from the corners.

⊲ If pδ

0 ∈ H1(Ω), can we find pδ 1 ∈ H1(Ω) satisfying these transmission conditions?

⊲ Can we even consider pδ

0 ∈ H1(Ω)?

16 / 34

slide-40
SLIDE 40

End-point of the periodic layer and corner singularities

x−

O

x+

O

Θ Γ x−

O

x+

O

Θ

⊲ Reminder from what we have just seen previously:

          

(∆ + k2

0)pδ 0 = div F,

(∆ + k2

0)pδ 1 = 0,

∂npδ

0 = 0,

∂npδ

1 = −(1 + ı)ζ∂2 t pδ 0,

  • Γ = 0,

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ ,
  • ∂x2pδ
  • Γ = 0,
  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

with term pδ

0 and pδ 1 that hare H1 regularity away from the corners.

⊲ If pδ

0 ∈ H1(Ω), can we find pδ 1 ∈ H1(Ω) satisfying these transmission conditions?

⊲ Can we even consider pδ

0 ∈ H1(Ω)?

16 / 34

slide-41
SLIDE 41

End-point of the periodic layer and corner singularities

x−

O

x+

O

Θ Γ x−

O

x+

O

Θ

⊲ Reminder from what we have just seen previously:

          

(∆ + k2

0)pδ 0 = div F,

(∆ + k2

0)pδ 1 = 0,

∂npδ

0 = 0,

∂npδ

1 = −(1 + ı)ζ∂2 t pδ 0,

  • Γ = 0,

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ ,
  • ∂x2pδ
  • Γ = 0,
  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

with term pδ

0 and pδ 1 that hare H1 regularity away from the corners.

⊲ If pδ

0 ∈ H1(Ω), can we find pδ 1 ∈ H1(Ω) satisfying these transmission conditions? No.

⊲ Can we even consider pδ

0 ∈ H1(Ω)? No.

16 / 34

slide-42
SLIDE 42

End-point of the periodic layer and corner singularities

x−

O

x+

O

Θ Γ x−

O

x+

O

Θ

⊲ Reminder from what we have just seen previously:

          

(∆ + k2

0)pδ 0 = div F,

(∆ + k2

0)pδ 1 = 0,

∂npδ

0 = 0,

∂npδ

1 = −(1 + ı)ζ∂2 t pδ 0,

  • Γ = 0,

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ ,
  • ∂x2pδ
  • Γ = 0,
  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

with term pδ

0 and pδ 1 that hare H1 regularity away from the corners.

⊲ If pδ

0 ∈ H1(Ω), can we find pδ 1 ∈ H1(Ω) satisfying these transmission conditions? No.

⊲ Can we even consider pδ

0 ∈ H1(Ω)? No.

⊲ ⇒ We need to study what happens close to the corner, and two kind of corner singularities (i.e. functions not in H1(Ω) close to the corner) will appear:

◮ corner singularities due to the transmission conditions (two next slides), ◮ corner singularities coming from the matching to the near field (slides beneath), 16 / 34

slide-43
SLIDE 43

End-point of the periodic layer and corner singularities

x−

O

x+

O

Θ Γ x−

O

x+

O

Θ

⊲ Reminder from what we have just seen previously:

          

(∆ + k2

0)pδ 0 = div F,

(∆ + k2

0)pδ 1 = 0,

∂npδ

0 = 0,

∂npδ

1 = −(1 + ı)ζ∂2 t pδ 0,

  • Γ = 0,

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ ,
  • ∂x2pδ
  • Γ = 0,
  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

with term pδ

0 and pδ 1 that hare H1 regularity away from the corners.

⊲ If pδ

0 ∈ H1(Ω), can we find pδ 1 ∈ H1(Ω) satisfying these transmission conditions? No.

⊲ Can we even consider pδ

0 ∈ H1(Ω)? No.

⊲ ⇒ We need to study what happens close to the corner, and two kind of corner singularities (i.e. functions not in H1(Ω) close to the corner) will appear:

◮ corner singularities due to the transmission conditions (two next slides), ◮ corner singularities coming from the matching to the near field (slides beneath), 16 / 34

slide-44
SLIDE 44

End-point of the periodic layer and corner singularities

Θ Hδ δ ρδ x−

O

Θ x−

O

⊲ We already derived the ansatz pδ(x) = pδ

0(x) + δpδ 1(x) + . . . ,

away from Γ, Now, we expand each pδ

q(x) under the form

q(x) = p0,q(x) + δ

π Θ p1,q(x) + δ 2π Θ p2,q(x) + . . .

⇒ The macroscopic term pδ admits the expansion pδ(x) = p0,0(x) + δ

π Θ p1,0(x) + δp0,1(x) + δ 2π Θ p2,0(x) + δ π Θ +1p1,1(x) + . . .

⊲ The limit term p0,0 has no jump condition across Γ, and is moreover in H1(Ω). ⊲ Therefore it can be expanded towards the corner x−

O in polar coordinates as

p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . .

17 / 34

slide-45
SLIDE 45

End-point of the periodic layer and corner singularities

Θ Hδ δ ρδ x−

O

Θ x−

O

⊲ We already derived the ansatz pδ(x) = pδ

0(x) + δpδ 1(x) + . . . ,

away from Γ, Now, we expand each pδ

q(x) under the form

q(x) = p0,q(x) + δ

π Θ p1,q(x) + δ 2π Θ p2,q(x) + . . .

⇒ The macroscopic term pδ admits the expansion pδ(x) = p0,0(x) + δ

π Θ p1,0(x) + δp0,1(x) + δ 2π Θ p2,0(x) + δ π Θ +1p1,1(x) + . . .

⊲ The limit term p0,0 has no jump condition across Γ, and is moreover in H1(Ω). ⊲ Therefore it can be expanded towards the corner x−

O in polar coordinates as

p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . .

17 / 34

slide-46
SLIDE 46

End-point of the periodic layer and corner singularities

Θ Hδ δ ρδ x−

O

Θ x−

O

⊲ We already derived the ansatz pδ(x) = pδ

0(x) + δpδ 1(x) + . . . ,

away from Γ, Now, we expand each pδ

q(x) under the form

q(x) = p0,q(x) + δ

π Θ p1,q(x) + δ 2π Θ p2,q(x) + . . .

⇒ The macroscopic term pδ admits the expansion pδ(x) = p0,0(x) + δ

π Θ p1,0(x) + δp0,1(x) + δ 2π Θ p2,0(x) + δ π Θ +1p1,1(x) + . . .

⊲ The limit term p0,0 has no jump condition across Γ, and is moreover in H1(Ω). ⊲ Therefore it can be expanded towards the corner x−

O in polar coordinates as

p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . .

17 / 34

slide-47
SLIDE 47

End-point of the periodic layer and corner singularities

Θ x−

O

⊲ We plug the expansion p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . . into the jump conditions (correspond for θ = 0) [p0,1]Γ = 2D∞ ∂x2p0,0Γ , [∂x2p0,1]Γ = N0(∂2

x1 + k2 0) p0,0Γ .

⊲ From this transmission conditions, we obtain a singularity of the form J π

Θ −1(k0r).

⊲ More precisely, there exists a function φ1(x) = J π

Θ −1(k0r)ψ1(θ) such that

(∆ + k2

0)φ1 = 0 and a numeric constant C1 such that

p0,1 − C1ℓ1(p0,0)φ1 ∈ H1 in a vicinity of x−

O

18 / 34

slide-48
SLIDE 48

End-point of the periodic layer and corner singularities

Θ x−

O

⊲ We plug the expansion p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . . into the jump conditions (correspond for θ = 0) [p0,1]Γ = 2D∞ ∂x2p0,0Γ , [∂x2p0,1]Γ = N0(∂2

x1 + k2 0) p0,0Γ .

⊲ From this transmission conditions, we obtain a singularity of the form J π

Θ −1(k0r).

⊲ More precisely, there exists a function φ1(x) = J π

Θ −1(k0r)ψ1(θ) such that

(∆ + k2

0)φ1 = 0 and a numeric constant C1 such that

p0,1 − C1ℓ1(p0,0)φ1 ∈ H1 in a vicinity of x−

O

18 / 34

slide-49
SLIDE 49

End-point of the periodic layer and corner singularities

Θ x−

O

⊲ We plug the expansion p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . . into the jump conditions (correspond for θ = 0) [p0,1]Γ = 2D∞ ∂x2p0,0Γ , [∂x2p0,1]Γ = N0(∂2

x1 + k2 0) p0,0Γ .

⊲ From this transmission conditions, we obtain a singularity of the form J π

Θ −1(k0r).

⊲ More precisely, there exists a function φ1(x) = J π

Θ −1(k0r)ψ1(θ) such that

(∆ + k2

0)φ1 = 0 and a numeric constant C1 such that

p0,1 − C1ℓ1(p0,0)φ1 ∈ H1 in a vicinity of x−

O

18 / 34

slide-50
SLIDE 50

End-point of the periodic layer and corner singularities

Θ H 1 ρ x−

O

⊲ Near field expansion with the scaled variable X− = (x − x−

O )/δ:

pδ(x) = P0,0 + δ

π Θ P1,0(X−) + δP0,1(X−) + δ 2π Θ P2,0(X−) + δ π Θ +1P1,1(X−) + . . .

⊲ Near field function P1,0 is solution of Laplace equation on the infinite domain Ω− with a prescribed growth R

π Θ cos π

Θ(θ − π) towards infinity.

⊲ Therefore, we have to study the function S, given by

      

∆S = 0, in Ω−, ∇S · n + (1 + ı)ζ∂2

ΓS = 0,

  • n ∂

Ω−, S(R, θ) ∼ R

π Θ cos π

Θ(θ − π), R → ∞, θ = 0. ⊲ We are interested in its behavior towards R → ∞.

19 / 34

slide-51
SLIDE 51

End-point of the periodic layer and corner singularities

Θ H 1 ρ x−

O

⊲ Near field expansion with the scaled variable X− = (x − x−

O )/δ:

pδ(x) = P0,0 + δ

π Θ P1,0(X−) + δP0,1(X−) + δ 2π Θ P2,0(X−) + δ π Θ +1P1,1(X−) + . . .

⊲ Near field function P1,0 is solution of Laplace equation on the infinite domain Ω− with a prescribed growth R

π Θ cos π

Θ(θ − π) towards infinity.

⊲ Therefore, we have to study the function S, given by

      

∆S = 0, in Ω−, ∇S · n + (1 + ı)ζ∂2

ΓS = 0,

  • n ∂

Ω−, S(R, θ) ∼ R

π Θ cos π

Θ(θ − π), R → ∞, θ = 0. ⊲ We are interested in its behavior towards R → ∞.

19 / 34

slide-52
SLIDE 52

End-point of the periodic layer and corner singularities

Θ H 1 ρ x−

O

⊲ Near field expansion with the scaled variable X− = (x − x−

O )/δ:

pδ(x) = P0,0 + δ

π Θ P1,0(X−) + δP0,1(X−) + δ 2π Θ P2,0(X−) + δ π Θ +1P1,1(X−) + . . .

⊲ Near field function P1,0 is solution of Laplace equation on the infinite domain Ω− with a prescribed growth R

π Θ cos π

Θ(θ − π) towards infinity.

⊲ Therefore, we have to study the function S, given by

      

∆S = 0, in Ω−, ∇S · n + (1 + ı)ζ∂2

ΓS = 0,

  • n ∂

Ω−, S(R, θ) ∼ R

π Θ cos π

Θ(θ − π), R → ∞, θ = 0. ⊲ We are interested in its behavior towards R → ∞.

19 / 34

slide-53
SLIDE 53

End-point of the periodic layer and corner singularities

Θ H 1 ρ x−

O

⊲ Near field expansion with the scaled variable X− = (x − x−

O )/δ:

pδ(x) = P0,0 + δ

π Θ P1,0(X−) + δP0,1(X−) + δ 2π Θ P2,0(X−) + δ π Θ +1P1,1(X−) + . . .

⊲ Near field function P1,0 is solution of Laplace equation on the infinite domain Ω− with a prescribed growth R

π Θ cos π

Θ(θ − π) towards infinity.

⊲ Therefore, we have to study the function S, given by

      

∆S = 0, in Ω−, ∇S · n + (1 + ı)ζ∂2

ΓS = 0,

  • n ∂

Ω−, S(R, θ) ∼ R

π Θ cos π

Θ(θ − π), R → ∞, θ = 0. ⊲ We are interested in its behavior towards R → ∞.

19 / 34

slide-54
SLIDE 54

End-point of the periodic layer and corner singularities

Θ H 1 ρ x−

O

⊲ We have to study the function S, given by

      

∆S = 0, in Ω−, ∇S · n + (1 + ı)ζ∂2

ΓS = 0,

  • n ∂

Ω−, S(R, θ) ∼ R

π Θ cos π

Θ(θ − π), R → ∞, θ = 0. ⊲ Main tool: extension of the Kondrat’ev theory V.A. Kondrat’ev, Boundary-value problems for elliptic equations in conical regions.

  • Dokl. Akad. Nauk SSSR 153, 1963.

S.A. Nazarov, The Neumann problem in angular domains with periodic and parabolic perturbations of the boundary. Tr. Mosk. Mat. Obs. 69, 2008.

20 / 34

slide-55
SLIDE 55

End-point of the periodic layer and corner singularities

Θ H 1 ρ x−

O

⊲ We have to study the function S, given by

      

∆S = 0, in Ω−, ∇S · n + (1 + ı)ζ∂2

ΓS = 0,

  • n ∂

Ω−, S(R, θ) ∼ R

π Θ cos π

Θ(θ − π), R → ∞, θ = 0. ⊲ The non-variational radial part of S is given by the asymptotic block P1 = R

π Θ cos π

Θ(θ − π) + R

π Θ −1ψ1(θ) + O(R π Θ −2 ln R)

Existence of the tail is related to the presence of the periodic array, ⊲ there exists a constant L (S) ∈ C such that S = P1 + L (S)R− π

Θ cos π

Θ(θ − π) + O(Rmax( π

Θ −2,− 2π Θ ) ln R) 21 / 34

slide-56
SLIDE 56

End-point of the periodic layer and corner singularities

Θ H 1 ρ x−

O

⊲ We have to study the function S, given by

      

∆S = 0, in Ω−, ∇S · n + (1 + ı)ζ∂2

ΓS = 0,

  • n ∂

Ω−, S(R, θ) ∼ R

π Θ cos π

Θ(θ − π), R → ∞, θ = 0. ⊲ The non-variational radial part of S is given by the asymptotic block P1 = R

π Θ cos π

Θ(θ − π) + R

π Θ −1ψ1(θ) + O(R π Θ −2 ln R)

Existence of the tail is related to the presence of the periodic array, ⊲ there exists a constant L (S) ∈ C such that S = P1 + L (S)R− π

Θ cos π

Θ(θ − π) + O(Rmax( π

Θ −2,− 2π Θ ) ln R) 21 / 34

slide-57
SLIDE 57

End-point of the periodic layer and corner singularities

⊲ Reminder: p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . . ⊲ P1,0 is, up to a multiplicative constant, the function S which is given by S = R

π Θ cos π

Θ(θ − π) + R

π Θ −1ψ1(θ) + L (S)R− π Θ cos π

Θ(θ − π) + . . . ⊲ R

π Θ term ⇐ comes from the matching with p0,0,

⊲ R

π Θ −1 term ⇒ will be matched by p0,1 (already matched),

⊲ R− π

Θ term ⇒ will be matched by p2,0: there exists a numeric constant C2 such that

p2,0 − C2ℓ1(p0,0)L (S)Y π

Θ (k0r) cos π

Θ(θ − π) ∈ H1 in a vicinity of x−

O

22 / 34

slide-58
SLIDE 58

End-point of the periodic layer and corner singularities

⊲ Reminder: p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . . ⊲ P1,0 is, up to a multiplicative constant, the function S which is given by S = R

π Θ cos π

Θ(θ − π) + R

π Θ −1ψ1(θ) + L (S)R− π Θ cos π

Θ(θ − π) + . . . ⊲ R

π Θ term ⇐ comes from the matching with p0,0,

⊲ R

π Θ −1 term ⇒ will be matched by p0,1 (already matched),

⊲ R− π

Θ term ⇒ will be matched by p2,0: there exists a numeric constant C2 such that

p2,0 − C2ℓ1(p0,0)L (S)Y π

Θ (k0r) cos π

Θ(θ − π) ∈ H1 in a vicinity of x−

O

22 / 34

slide-59
SLIDE 59

End-point of the periodic layer and corner singularities

⊲ Reminder: p0,0(x) = ℓ0(p0,0)J0(k0r) + ℓ1(p0,0)J π

Θ (k0r) cos π

Θ(θ − π) + . . . ⊲ P1,0 is, up to a multiplicative constant, the function S which is given by S = R

π Θ cos π

Θ(θ − π) + R

π Θ −1ψ1(θ) + L (S)R− π Θ cos π

Θ(θ − π) + . . . ⊲ R

π Θ term ⇐ comes from the matching with p0,0,

⊲ R

π Θ −1 term ⇒ will be matched by p0,1 (already matched),

⊲ R− π

Θ term ⇒ will be matched by p2,0: there exists a numeric constant C2 such that

p2,0 − C2ℓ1(p0,0)L (S)Y π

Θ (k0r) cos π

Θ(θ − π) ∈ H1 in a vicinity of x−

O

22 / 34

slide-60
SLIDE 60

Outline

1

Surface homogenization for micro-structured layers with singularities

2

Extension of the macroscopic part of the solution Periodic layer obstacle and transmission conditions (2 scales) End-point of the periodic layer and corner singularities Periodic layer obstacle and transmission conditions (3 scales)

3

Numerical simulations

4

Conclusion and perspectives

23 / 34

slide-61
SLIDE 61

Periodic layer obstacle and transmission conditions (3 scales)

Computation of the blockage coefficient D∞ in the inviscid case (ζ = 0)

1

  • Γ = 2D∞
  • ∂x2pδ
  • Γ

and

  • ∂x2pδ

1

  • Γ = N0(∂2

x1 + k2 0)

  • Γ .

H ρ X1 X2

10−1 100 10−2 10−1 100 101

1

ρ D∞

H = 0.3 H = 0.6

⊲ When ρ → 0, D∞ → ∞. Here the 2 scale model is not suitable for small holes. ⊲ In the following, we study an asymptotic model that suits more.

24 / 34

slide-62
SLIDE 62

Periodic layer obstacle and transmission conditions (3 scales)

From now on, η(δ) = o(δ) (asymptotically small holes). Hη(δ) δ η(δ) ∆pδ + k2

0pδ = div F,

in Ωδ, ∂npδ = 0,

  • n ∂Ωδ.

Goal: derive an approximate model on the limit geometry Ω0. Γ

25 / 34

slide-63
SLIDE 63

Periodic layer obstacle and transmission conditions (3 scales)

From now on, η(δ) = o(δ) (asymptotically small holes). Hη(δ) δ η(δ) ∆pδ + k2

0pδ = div F,

in Ωδ, ∂npδ = 0,

  • n ∂Ωδ.

Goal: derive an approximate model on the limit geometry Ω0. Γ The limit term pδ

0 satisfies

            

∆pδ

0 + k2 0pδ 0 = div F,

in Ω ∂npδ

0 = 0,

  • n ∂Ω0
  • Γ = − 2

π δ ln η ∂x2pδ

  • Γ ,
  • ∂x2pδ
  • Γ = 0.

Non-trivial limit when δ ln η ∼ 1.

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SLIDE 64

Periodic layer obstacle and transmission conditions (3 scales)

From now on, η(δ) = o(δ) (asymptotically small holes). Hη(δ) δ η(δ) ∆pδ + k2

0pδ = div F,

in Ωδ, ∂npδ = 0,

  • n ∂Ωδ.

Goal: derive an approximate model on the limit geometry Ω0. Tool: three-scale expansion. Γ The limit term pδ

0 satisfies

            

∆pδ

0 + k2 0pδ 0 = div F,

in Ω ∂npδ

0 = 0,

  • n ∂Ω0
  • Γ = − 2

π δ ln η ∂x2pδ

  • Γ ,
  • ∂x2pδ
  • Γ = 0.

Non-trivial limit when δ ln η ∼ 1.

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SLIDE 65

Periodic layer obstacle and transmission conditions (3 scales)

Hη(δ) δ η(δ) Mesoscopic (δ-) scale H η

δ η δ

Mesoscopic field ∆Π = g, ∂nΠ = 0, with periodic lateral b.c. Macroscopic scale

          

∆pδ

0 + k2 0pδ 0 = div F,

in Ω ∂npδ

0 = 0,

  • n ∂Ω0
  • Γ = −2δ ln η/π

∂x2pδ

  • Γ ,
  • ∂x2pδ
  • Γ = 0.

Microscopic (η-) scale H 1 Microscopic field ∆P = H, ∂nP = 0, ⇒ transmission conditions for pδ

0.

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SLIDE 66

Periodic layer obstacle and transmission conditions (3 scales)

Hη(δ) δ η(δ) Mesoscopic (δ-) scale H η

δ η δ

Mesoscopic field ∆Π = g, ∂nΠ = 0, with periodic lateral b.c. Macroscopic scale

          

∆pδ

0 + k2 0pδ 0 = div F,

in Ω ∂npδ

0 = 0,

  • n ∂Ω0
  • Γ = −2δ ln η/π

∂x2pδ

  • Γ ,
  • ∂x2pδ
  • Γ = 0.

Microscopic (η-) scale H 1 Microscopic field ∆P = H, ∂nP = 0, ⇒ transmission conditions for pδ

0.

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SLIDE 67

Periodic layer obstacle and transmission conditions (3 scales)

Γ Mesoscopic (δ-) scale H η

δ η δ

Mesoscopic field ∆Π = g, ∂nΠ = 0, with periodic lateral b.c. Macroscopic scale

          

∆pδ

0 + k2 0pδ 0 = div F,

in Ω ∂npδ

0 = 0,

  • n ∂Ω0
  • Γ = −2δ ln η/π

∂x2pδ

  • Γ ,
  • ∂x2pδ
  • Γ = 0.

Microscopic (η-) scale H 1 Microscopic field ∆P = H, ∂nP = 0, ⇒ transmission conditions for pδ

0.

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SLIDE 68

Periodic layer obstacle and transmission conditions (3 scales)

Hη(δ) δ η(δ) Γ

Corresponds to the experimental results provided by DLR Berlin

  • A. Schulz, F. Bake, L. Enghardt et al.

(2015) Acta Acust. united Ac., 101 (1).

Observation (confirmed by theory): p0,0 is H1 close to the re-entrant corners.

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slide-69
SLIDE 69

Outline

1

Surface homogenization for micro-structured layers with singularities

2

Extension of the macroscopic part of the solution Periodic layer obstacle and transmission conditions (2 scales) End-point of the periodic layer and corner singularities Periodic layer obstacle and transmission conditions (3 scales)

3

Numerical simulations

4

Conclusion and perspectives

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SLIDE 70

Numerical simulations Computation of the macroscopic error as a function of δ (2 scales)

10−3 10−2 10−1 10−6 10−5 10−4 10−3 10−2 10−1 100 101 102 103

1 4/3 2

Distance δ between two consecutive holes Relative macroscopic error

two scale limit u0,0 two scale expansion u0,0 + δu0,1 two scale expansion u0,0 + δu0,1 + δ4/3u2,0

Figure: Numerically computed errors of macroscopic expansions truncated at different orders in dependence of δ for the inviscid model for the porosity ρ = 0.3 and the height h(δ) = 0.6 δ.

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SLIDE 71

Numerical simulations Computation of the macroscopic error as a function of δ (2 scales)

10−3 10−2 10−1 10−4 10−3 10−2 10−1 100 101 102 103

∼ 1 ∼ 4/3

Distance δ between two consecutive holes Relative macroscopic error

two scale limit u0,0 two scale expansion u0,0 + δu0,1

Figure: Numerically computed errors of macroscopic expansions truncated at different orders in dependence of δ for the viscous model (ζ = 0.1) for the porosity ρ = 0.3 and the height h(δ) = 0.6 δ.

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SLIDE 72

Numerical simulations Computation of the macroscopic error: 2 scale or 3 scale strategy?

⊲ inviscid model, ⊲ distance between two holes δ = 1/64, ⊲ height h(δ) = 0.002 ⊲ size of a hole η = ρδ, ⊲ wave number k0 = 5π,

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 10−4 10−3 10−2 10−1 100 Porosity ρ Relative macroscopic error two scale limit u0,0 two scale expansion u0,0 + δuδ

0,1

two scale epxansion u0,0 + δuδ

0,1 + δ

4 3 uδ

2,0

three scale limit u0,0 30 / 34

slide-73
SLIDE 73

Outline

1

Surface homogenization for micro-structured layers with singularities

2

Extension of the macroscopic part of the solution Periodic layer obstacle and transmission conditions (2 scales) End-point of the periodic layer and corner singularities Periodic layer obstacle and transmission conditions (3 scales)

3

Numerical simulations

4

Conclusion and perspectives

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slide-74
SLIDE 74

Conclusion and perspectives

Γ x−

O

x+

O

Θ

∂t v + (v ·∇) v + ∇p−ν∆ v = f in Ωδ,η ∂tp + c2 div v + v ·∇p + p div v = 0 in Ωδ,η v = 0

  • n ∂Ωδ,η

⊲ We described the surface homogenization method in presence of finite periodic layer with corner singularities. ⊲ In this method, we separated the solution into macroscopic part, boundary periodic corrector, and near field corrector. ⊲ We studied the extension of the macroscopic part to the solution to the interface Γ, including its end-points x±

O , using different stories.

⊲ Validated by numerical simulations. ⊲ WIP: extend the surface homogenization method taking into account the viscosity (full model) and the non-linearity.

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slide-75
SLIDE 75

Conclusion and perspectives

Γ x−

O

x+

O

Θ

∂t v + (v ·∇) v + ∇p−ν∆ v = f in Ωδ,η ∂tp + c2 div v + v ·∇p + p div v = 0 in Ωδ,η v = 0

  • n ∂Ωδ,η

⊲ We described the surface homogenization method in presence of finite periodic layer with corner singularities. ⊲ In this method, we separated the solution into macroscopic part, boundary periodic corrector, and near field corrector. ⊲ We studied the extension of the macroscopic part to the solution to the interface Γ, including its end-points x±

O , using different stories.

⊲ Validated by numerical simulations. ⊲ WIP: extend the surface homogenization method taking into account the viscosity (full model) and the non-linearity.

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slide-76
SLIDE 76

Conclusion and perspectives

Θ H 1 ρ x−

O

Θ M

⊲ We have studied the function S, given by

      

∆S = 0, in Ω−, ∇S · n + (1 + ı)ζ∂2

ΓS = 0,

  • n ∂

Ω−, S(R, θ) ∼ R

π Θ cos π

Θ(θ − π), R → ∞, θ = 0. ⊲ and we developed tools to study such that problem. ⊲ Similar tools can be used to study the 2D eddy current formulation for a conductor surrounded by a dielectric medium towards infinity (recent discussion with K. Schmidt,

  • R. Hiptmair, R. Cassagrande, M. Dauge)

−∆uδ + ı δ2 1Muδ = f

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SLIDE 77

Thank you for your attention

  • B. Delourme, K. Schmidt, and A. S. On the homogenization of thin perforated walls
  • f finite length. Asymptotic Analysis, 97(3-4):211-264, April 2016.
  • B. Delourme, K. Schmidt, and A. S. When a thin periodic layer meets corners:

asymptotic analysis of a singular Poisson problem. Technical Report arXiv:1506.06964, June 2015.

  • A. S., B. Delourme, and K. Schmidt. On the homogenization of the Helmholtz

problem with thin perforated walls of finite length. Submitted.

  • A. S. and K. Schmidt. On the homogenization of the acoustic wave propagation in

perforated ducts of finite length for an inviscid and a viscous model. Submitted. Numerical simulations have been done using the C++ library Concepts http://www.tu-berlin.de/?concepts

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